Milk True Protein Research Articles

Effects of rumen-protected folic acid and branched-chain volatile fatty acids supplementation on lactation performance, ruminal fermentation, nutrient digestion and blood metabolites in dairy cows

This study evaluated the effects of branched-chain volatile fatty acids (BCVFA) and rumen protected folic acid (RPFA) supplementation on lactation performance, ruminal fermentation, nutrient digestion and blood metabolites in dairy cows. Fifty-six multiparous Chinese Holstein cows (3.2 ± 1.1 of parity, 631 ± 16.4 kg of body weight [BW], 65 ± 2.6 days in milk [DIM] and 30.2 ± 2.1 kg of milk yield per day, mean ± SD) were blocked by lactation number, milk yield per day and DIM and were arranged into one of four groups in a randomized block design with a 2 × 2 factorial arrangement. Supplemental BCVFA (0 g/d [BCVFA-] or 80 g/d [BCVFA+]) and RPFA (0 mg/d [RPFA-] or 128 mg/d [RPFA+]) were hand-mixed into the top one-third of total mixed ration. Dietary concentrate to forage ratio was 50:50 based on a dry matter (DM) basis. Experimental periods comprised 105 days with 15 d of adaptation followed by 90 d of data collection. DM intake was increased with BCVFA supplementation, but was unaffected by RPFA. The BW changes were similar among treatments. Yields of milk, milk fat and lactose were increased, and milk true protein yield tended to increase with BCVFA or RPFA supplementation. Milk fat percentage was increased with BCVFA supplementation, but was unaffected by RPFA. Percentage of milk true protein was increased, lactose was unaltered and feed conversion ratio was decreased with BCVFA or RPFA supplementation. Ruminal pH and ammonia N concentration were decreased, but total volatile fatty acids concentration was increased with BCVFA or RPFA supplementation. Molar proportion of acetate was increased and propionate was decreased, resulting in an increased ratio of acetate to propionate with BCVFA supplementation. Acetate and propionate molar proportion and the ratio of acetate to propionate were not affected by RPFA. Digestibilities of DM, organic matter, crude protein, non-fiber carbohydrates, neutral detergent fibre and acid detergent fibre were increased with BCVFA or RPFA supplementation. Similarly, activities of caboxymethyl-cellulase, cellobiase, xylanase, pectinase, α-amylase and protease and abundance of R. albus, R. flavefaciens, F. succinogenes, B. fibrisolvens and P. ruminicola were increased. However, R. amylophilus abundance was not affected by BCVFA and increased with RPFA supplementation. Serum concentrations of glucose and non-esterified fatty acids (NEFA) were unaltered and total protein was increased with BCVFA or RPFA supplementation. Serum acetoacetate (ACAC) and BHBA were increased by BCVFA, but were decreased by RPFA. Supplementation of BCVFA or RPFA increased serum growth hormone releasing hormone, growth hormone and insulin-like growth factor-1. These results indicated that lactation performance, ruminal fermentation, nutrient digestion and hormone secretion improved due to the stimulated ruminal bacteria growth and enzyme activity with BCVFA or RPFA supplementation, but no BCVFA × RPFA interaction was detected during the trial.

Comparison of Breast Milk Compositions Among Mothers Delivering Small-for-Gestational Age, Appropriate-for-Gestational Age, and Large-for-Gestational Age Infants.

The aim of this study was to compare the breast milk compositions of mothers who delivered babies in three different birth weight categories. We collected 75 breast milk samples from mothers of small-for-gestational age (SGA), appropriate-for-gestational age (AGA), and large-for-gestational age (LGA) term infants (25 per group) on the 11th-28th day postpartum using a manual or electric breast pump. Homogenized samples were analyzed using a mid-infrared human milk analyzer within 2 hours of collection, and protein, carbohydrate (CHO), fat, and energy levels were compared. Of 75 participants (median maternal age: 29 years), there was a significant difference in maternal body mass index (BMI), gestational age, and birth weight among the three groups. However, we found no significant variation in breast milk true protein, crude protein, fat, or energy. The CHO composition of breast milk in mothers of SGA infants (7.1 g/100 mL, range: 6.6-7.3 g/100 mL) was significantly lower than that in the AGA (7.3 g/100 mL, range: 7.1-7.5 g/100 mL) and LGA (7.2 g/100 mL, range: 6.7-7.4 g/100 mL) groups. After post hoc multiple comparison, only CHO levels between the SGA and AGA groups were significantly different (p = 0.025), whereas no significant correlation was found between maternal BMI, gestational age, and CHO. The CHO component in breast milk from mothers of SGA infants was significantly lower compared with the AGA and LGA groups, but with no clinical significance. Breast milk compositions of mothers of LGA infants were comparable to those of SGA and AGA infants. Therefore, fetal growth status does not significantly influence maternal breast milk nutrients.

Influence of supplementing a methionine derivative, N-acetyl-l-methionine, in dairy diets on production and ruminal fermentation by lactating cows during early to mid lactation

The present study investigated production responses and ruminal fermentation characteristics of lactating dairy cows when supplemented with N-acetyl-l-Met (NALM) as a source of rumen-protected Met in metabolizable protein (MP)-deficient (MPD) or MP-adequate diet (MPA). Eight lactating dairy cows (53 ± 10.4 d in milk, average ± standard deviation) were blocked by parity and days in milk, and the experiment was performed in a replicated 4 × 4 Latin square design. Within each square, cows were randomly assigned to a sequence of 4 diets during each of the four 21-d periods (14 d of treatment adaptation and 7 d of data collection and sampling). A 2 × 2 factorial arrangement was used; MPD or MPA was combined without or with NALM: MPD without NALM, MPD with NALM (MPD+NALM), MPA without NALM, and MPA with NALM (MPA+NALM). A NALM product was supplemented in the MPD+NALM and the MPA+NALM at 30 g/cow per d. Supplementation of NALM did not affect dry matter intake (DMI) and milk yield regardless of MP concentration. In addition, supplementing NALM resulted in a similar milk true protein concentration and yield. In contrast, NALM supplementation increased milk fat concentration and yield and 3.5% fat-corrected milk yield and tended to increase energy-corrected milk yield regardless of MP difference. Additionally, trends were observed for increased 3.5% fat-corrected milk yield/DMI and energy-corrected milk yield/DMI, and the positive effects were greater under the MPA than the MPD diet, resulting in trends toward interactions between MP and NALM. Dietary treatments had similar effects on ruminal fermentation characteristics and microbial protein yield. Plasma concentration of Met increased under the MPD but not the MPA diet, leading to an MP × NALM interaction. Overall results in the current study suggest that NALM exerted a minor influence on ruminal metabolism, but increased milk fat concentration, resulting in increases in milk fat yield and feed efficiency. Yet, potential effects of NALM on intermediary metabolism between the gastrointestinal tract, the liver, and the mammary gland need to be explored to understand utilization efficiency for production of dairy cows.

Milk protein composition in purebred Holsteins and in first/second-generation crossbred cows from Swedish Red, Montbeliarde and Brown Swiss bulls

The aim of this study was to analyze milk protein composition in purebred and crossbred dairy cattle and estimate the effects of individual sources of variation on the investigated traits. Milk samples were collected from 505 cows from three commercial farms located in Northern Italy, some of which had originated from crossbreeding programs, although most were purebred Holsteins (HO). The basic crossbreeding scheme was a three-breed rotational system using Swedish Red (SR) semen on HO cows (SR×HO), Montbeliarde (MO) semen on SR×HO cows (MO×(SR×HO)) and HO semen again on MO×(SR×HO) cows. A smaller number of purebred HO from each of the herds were mated inverting the breed order (MO×HO and SR×(MO×HO)) or using Brown Swiss (BS) bulls (BS×HO) then MO bulls (MO×(BS×HO)). Milk samples were analyzed by reverse-phase HPLC to obtain protein fraction amounts (g/l) and proportions (% of total true protein). Traits were analyzed using a linear model, which included the fixed effects of herd-test-day (HTD), parity, days in milk and breed combination. Results showed that milk protein fractions were influenced by HTD, stage of lactation, parity and breed combination. The increase in protein concentration during lactation was due in particular to β-casein (β-CN), αS1-CN and β-lactoglobulin (β-LG). The higher protein content of primiparous milk was mainly due to higher concentrations of all casein fractions. The milk from crossbred cows had higher contents and proportions of κ-CN and α-lactalbumin (α-LA), lower proportions of β-LG and greater proportion of caseins/smaller in whey proteins on milk true protein than purebred HO. The three-way crossbreds differed from two-way crossbreds only in having greater proportions of α-LA in their milk. Of the three-way crossbreds, the SR sired cows yielded milk with a smaller content and proportion of β-LG than the MO sired cows, and, consequently, a higher proportion of caseins than whey proteins. Results from this study support the feasibility of using crossbreeding programs to alter milk protein profiles with the aim of improving milk quality and cheese-making properties.

Replacing ground corn with incremental amounts of liquid molasses does not change milk enterolactone but decreases production in dairy cows fed flaxseed meal

We investigated the effects of replacing ground corn (GRC) with incremental amounts of liquid molasses (LM) on milk enterolactone concentration, antioxidant enzymes activity in plasma, production, milk fatty acid (FA) profile, and nutrient utilization in Jersey cows fed flaxseed meal and low-starch diets. Sixteen multiparous organically certified Jersey cows averaging (mean ± standard deviation) 101 ± 45 d in milk, 462 ± 38 kg of body weight, and 19.8 ± 3.90 kg/d of milk in the beginning of the study were randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design, with 14 d for diet adaptation and 7 d for data and sample collection. Diets were fed as total mixed rations consisting (dry matter basis) of 52% grass-legume baleage, 8% grass hay, 8.5% soyhulls, 2.5% roasted soybean, 15% flaxseed meal, and 2% minerals-vitamins premix. The GRC-to-LM dietary ratios (dry matter basis) were 12:0, 8:4, 4:8, and 0:12. Orthogonal polynomials were used to test linear, quadratic, and cubic effects using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). The milk concentration of enterolactone tended to respond cubically, thus suggesting that replacing GRC with LM did not affect this lignan in milk. The plasma activities of the antioxidant enzymes glutathione peroxidase and catalase did not differ, but superoxide dismutase activity tended to respond cubically with feeding increasing amounts of LM. Dry matter intake and yields of milk and milk fat, true protein, and lactose decreased linearly with substituting GRC for LM. Whereas the concentrations of milk fat and milk true protein did not differ across treatments, milk lactose content decreased linearly. Feeding incremental levels of LM reduced linearly the milk concentration of urea N and the amount of N excreted in urine, and tended to decrease linearly the concentration of plasma urea N. Apparent total-tract digestibilities of dry matter, organic matter, and neutral and acid detergent fiber did not differ across treatments, whereas digestibility of crude protein decreased linearly. Digestibility of starch responded linearly and quadratically, but the actual differences between treatments were too small to be biologically significant. Milk FA profile was substantially changed most notably by linear increases in cis-9,trans-11 18:2, cis-9,cis-12,cis-15 18:3, Σ odd-chain FA, and the trans-11-to-trans-10 ratio, and linear decreases in cis-9 18:1 and cis-9,cis-12 18:2 when replacing GRC by incremental amounts of LM.

Utilization of protein in red clover and alfalfa silages by lactating dairy cows and growing lambs

Feeding trials were conducted with lactating cows and growing lambs to quantify effects of replacing dietary alfalfa silage (AS) with red clover silage (RCS) on nutrient utilization. The lactation trial had a 2 × 4 arrangement of treatments: AS or RCS fed with no supplement, rumen-protected Met (RPM), rumen-protected Lys (RPL), or RPM plus RPL. Grass silage was fed at 13% of dry matter (DM) with AS to equalize dietary neutral detergent fiber (NDF) and crude protein contents. All diets contained (DM basis) 5% corn silage and 16% crude protein. Thirty-two multiparous (4 ruminally cannulated) plus 16 primiparous Holstein cows were blocked by parity and days in milk and fed diets as total mixed rations in an incomplete 8 × 8 Latin square trial with four 28-d periods. Production data (over the last 14 d of each period) and digestibility and excretion data (at the end of each period) were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Although DM intake was 1.2 kg/d greater on AS than RCS, milk yield and body weight gain were not different. However, yields of fat and energy-corrected milk as well as milk content of fat, true protein, and solids-not-fat were greater on AS. Relative to AS, feeding RCS increased milk and energy-corrected milk yield per unit of DM intake, milk lactose content, and apparent N efficiency and reduced milk urea. Relative to AS, apparent digestibility of DM, organic matter, NDF, and acid detergent fiber were greater on RCS, whereas apparent and estimated true N digestibility were lower. Urinary N excretion and ruminal concentrations of ammonia, total AA, and branched-chain volatile fatty acids were reduced on RCS, indicating reduced ruminal protein degradation. Supplementation of RPM increased intake, milk true protein, and solids-not-fat content and tended to increase milk fat content. There were no silage × RPM interactions, suggesting that RPM was equally limiting on both AS and RCS. Supplementation of RPL did not influence any production trait; however, a significant silage × RPL interaction was detected for intake: RPL reduced intake of AS diets but increased intake of RCS diets. Duplicated metabolism trials were conducted with lambs confined to metabolism crates and fed only silage. After adaptation, collections of silage refusals and excreta were made during ad libitum feeding followed by feeding DM restricted to 2% of body weight. Intake of DM was not different when silages were fed ad libitum. Apparent digestibility of DM, organic matter, NDF, and hemicellulose was greater in lambs fed RCS on both ad libitum and restricted intake; however, acid detergent fiber digestibility was only greater at restricted intake. Apparent and estimated true N digestibility was substantially lower, and N retention was reduced, on RCS. Results confirmed greater DM and fiber digestibility in ruminants and N efficiency in cows fed RCS. Specific loss of Lys bioavailability on RCS was not observed. Based on milk composition, Met was the first-limiting AA on both silages; however, Met was not limiting based on production and nutrient efficiency. Depressed true N digestibility suggested impaired intestinal digestibility of rumen-undegraded protein from RCS.

Meta-analysis to predict the effects of metabolizable amino acids on dairy cattle performance

Meta-analytic methods were used to determine statistical relationships between metabolizable AA supplies and milk protein yield, milk protein percentage, and milk yield in lactating dairy cows. Sixty-three research publications (258 treatment means) were identified through a search of published literature using 3 search engines and met the criteria for inclusion in this meta-analysis. The Cornell Net Carbohydrate and Protein System (CNCPS) version 6.5 was used to determine dietary nutrient parameters including metabolizable AA. Two approaches were used to analyze the data. First, mixed models were fitted to determine whether explanatory variables predicted responses. Each mixed model contained a global intercept, a random intercept for each experiment, and data were weighted by the inverse of the SEM squared. The second analysis approach used classical effect size meta-analytical evaluation of responses to treatment weighted by the inverse of the treatment variance and with a random effect of treatment nested within experiment. Regardless of the analytical approach, CNCPS-predicted metabolizable Met (g/d) was associated with milk protein percentage and yield. Milk yield was positively associated with CNCPS-predicted metabolizable His, Leu, Trp, Thr, and nonessential AA (g/d). Milk true protein yield was also associated with CNCPS-predicted metabolizable Leu (g/d). Predicted metabolizable Lysine (g/d) did not increase responses in production outcomes. However, mean metabolizable Lys supply was less than typically recommended and the change with treatment was minimal (157 vs. 162 g; 6.36 vs. 6.38% metabolizable protein). Experiments based solely on Lys or Met interventions were excluded from the study database. It is possible that the inclusion of these experiments may have provided additional insight into the effect of these AA on responses. This meta-analysis supports other research indicating a positive effect of Met and His as co-limiting AA in dairy cows and suggests Leu, Trp, and Thr be given greater consideration in future research.

Effect of supplemental yeast culture and dietary starch content on rumen fermentation and digestion in dairy cows

The objectives of this experiment were to evaluate the effect of feeding a culture of Saccharomyces cerevisiae on rumen metabolism and digestibility when cows are fed diets varying in starch content. Four lactating Holstein cows were assigned to a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Treatments were low starch (LS; 23% of diet DM) and no yeast culture (YC; LS-control), LS and 15 g of YC/d (LS-YC), high starch (HS; 29% of diet DM) and no YC (HS-control), and HS and 15 g of YC/d (HS-YC). Periods lasted 28 d, with the last 9 d for data collection. Days 20 to 24 were used to determine production, nutrient flow, and digestibility. On d 25, 3 kg of corn grain DM was placed in the rumen 1 h before the morning feeding, and yields of milk and milk components were measured after the challenge. Blood was sampled -1, 3, 7, and 11 h relative to the morning feeding on d 24 and 25. Rumen pH was measured continuously on d 24 and 25. Rumen papillae were collected on d 24 and 28 to quantify mRNA expression of select genes. Supplementing YC increased yields of milk (26.3 vs. 29.6 kg/d), energy-corrected milk (ECM; 26.5 vs. 30.3 kg/d), fat (0.94 vs. 1.08 kg/d), true protein (0.84 vs. 0.96 kg/d), and ECM/dry matter intake (1.15 vs. 1.30) compared with the control but did not affect dry matter intake (22.6 vs. 22.9 kg/d). Cows fed HS had increased milk true protein percentage (3.18 vs. 3.31%) and yield (0.87 vs. 0.94 kg/d) compared with cows fed LS. Feeding HS-YC increased the proportion of dietary N incorporated into milk true protein from 24.9% in the other 3 treatments to 29.6%. Feeding HS increased the concentration of propionate (21.7 vs. 32.3 mM) and reduced that of NH3-N (8.3 vs. 6.7 mg/dL) in rumen fluid compared with the control, and combining HS with YC in HS-YC tended to increase microbial N synthesis compared with LS-YC (275 vs. 322 g/d). Supplementing YC to cows fed HS reduced plasma haptoglobin and rumen lactate concentrations, increased mean rumen pH, reduced the time with pH <6.0, and prevented the decrease in rumen neutral detergent fiber digestion caused by HS. Cows fed HS had less total-tract digestion of organic matter (73.9 vs. 72.4%) because of reduced acid detergent fiber (57.6 vs. 51.7%) and neutral detergent fiber (60.9 vs. 56.7%) digestibility. Production performance after the challenge was similar to that before the challenge, and YC improved yield of ECM. After the challenge, supplementing YC tended to reduce rumen lactate concentration compared with the control and reduced haptoglobin in cows fed HS. Feeding HS but not YC increased expression in rumen papillae of genes for receptors (FFAR2 and FFAR3) and transporter (SLC16A3) of short-chain fatty acids but did not affect genes involved in transport of Na+/H+ or water or in inflammatory response. Supplementing YC to dairy cows improved lactation performance in diets containing low or high starch, and mechanisms might be partially attributed to improvements in rumen pH, digestion of fiber, microbial N synthesis, and reduction in acute phase response.

Effects of supplementing yeast culture to diets differing in starch content on performance and feeding behavior of dairy cows

The objectives were to evaluate the effects of a culture of Saccharomyces cerevisiae (YC) on lactation performance of cows fed diets differing in starch content. Fifty-six Holstein cows at 42 d postpartum were blocked by parity and milk production and randomly assigned to 1 of 4 treatments, low starch (23% diet DM) and no YC (LS-control), low starch and 15 g/d of YC (LS-YC), high starch (29% diet DM) and no YC (HS-control), and high starch and 15 g/d of YC (HS-YC). The experiment lasted 14 wk. Blood was sampled twice weekly during the first 5 wk in the experiment. Feeding behavior was evaluated in 2 consecutive days when cows were 33 d in the experiment. On d 92 in the experiment, cows were challenged with 3 kg of corn grain DM immediately before the morning feeding. Blood was sampled in the first 12 h after the challenge. Rumen fluid was collected 5 h after the challenge, and pH, ammonia N, short-chain fatty acids, and lactate concentrations were quantified. Lactation performance was measured daily before and after the challenge. Supplementation with YC increased yields of 3.5% fat-corrected milk and energy-corrected milk by 2.2 and 2.0 kg/d, and the increments were observed in both low- and high-starch diets. Feeding HS tended to decrease milk fat content (LS = 3.88 vs. HS = 3.73%), but increased concentration (LS = 2.87 vs. HS = 3.00%) and yield (LS = 1.11 vs. HS = 1.20 kg/d) of milk true protein. Feeding YC increased yields of fat and true protein in milk by 100 and 60 g/d. Energy balance, body weight, and feed efficiency did not differ with treatments. Feeding HS reduced eating time (LS = 177 vs. HS = 159 min/12 h) and intermeal interval (LS = 103 vs. HS = 82 min), but tended to increase eating rate (LS = 139 vs. HS = 150 g/min). Interactions were detected between level of starch and YC for ruminating time, meal duration, and meal size because within LS, feeding YC increased ruminating time 23 min/12 h, but reduced meal duration 6 min/meal and meal size 0.7 kg/meal. Concentrations of glucose in plasma increased (LS = 62.1 vs. HS = 63.8 mg/dL), whereas those of urea N decreased (LS = 10.1 vs. HS = 9.4 mg/dL) with feeding HS compared with LS in the first 5 wk in the experiment, and the same responses were observed after the challenge with corn grain. After the challenge, rumen pH was less and short-chain fatty acid concentrations were greater in cows fed HS compared with those fed LS; however, supplementing YC to high-starch diets increased rumen pH (HS-control = 5.72 vs. HS-YC = 6.12) and reduced concentrations of lactate in rumen fluid (HS-control = 7.72 vs. HS-YC = 1.33 mM) and haptoglobin in plasma 28%. Feeding YC improved lactation performance irrespective of the level of dietary starch and reduced the risk of subacute rumen acidosis induced by a grain challenge when cows were fed a high-starch ration.

The plasma free amino acid dose-response technique: A proposed methodology for determining lysine relative bioavailability of rumen-protected lysine supplements

Estimates of Lys bioavailability of rumen-protected Lys (RP-Lys) supplements are often obtained using in vitro or 2-step in situ techniques, with little to no data determining efficacy and bioavailability in vivo. The objective of this study was to further evaluate and refine the use of the plasma free AA dose-response technique as a method for determining Lys relative bioavailability of RP-Lys supplements. Thirteen dose-response Latin square studies using 87 lactating, ruminally cannulated multiparous Holstein cows (days in milk from 55 to 315 and milk yield from 12 to 62 kg/d at the start of the studies) were conducted to measure the relative bioavailability of RP-Lys supplements. Intestinal (1 study) and abomasal (12 studies) infusions of Lys ranged from 0 to 84 g/d, and experimental periods ranged from 4 to 21 d. Basal diets were formulated to be adequate in metabolizable Met, but varied in predicted metabolizable Lys (5.04 to 6.81% of metabolizable protein). One to 4 daily blood samples were taken from the coccygeal vessels for 1 to 3 consecutive days in each period. Plasma Lys concentration in cows assigned to the control treatment (0 g/d Lys) ranged from 1.83 to 5.21% of total plasma AA, whereas that from cows duodenally or abomasally infused with Lys ranged from 2.53 to 7.51% of total plasma AA. Results from studies involving more than 2 amounts of infused Lys confirmed linearity of response. The following variables were regressed against the plasma Lys dose-response slopes generated from the Lys infusion treatments to examine their effects on the magnitude of the slopes: plasma Lys concentration of the control diet, plasma Lys concentration at the greatest amount of infused Lys, net energy of lactation and metabolizable protein balances, metabolizable protein supply, days in milk, milk yield, milk concentrations of fat, true protein, and lactose, milk true protein yield, and dry matter intake. The variable having the greatest effect on the magnitude of the dose-response slope was the plasma Lys concentration at the greatest amount infused. The relative bioavailability of evaluated RP-Lys supplements using the plasma free AA dose-response technique ranged from 5 to 87%. It was concluded that plasma free Lys increases in a linear fashion to increasing amounts of absorbed Lys and that the dose-response technique is an appropriate technique for evaluating RP-Lys supplements.

Production and nitrogen utilization in lactating dairy cows fed ground field peas with or without ruminally protected lysine and methionine.

Previous research has shown that cows fed ≥24% of the diet dry matter (DM) as field peas decreased milk yield as well as concentration and yield of milk protein, possibly due to reduced DM intake and limited supply of Lys and Met. Twelve multiparous and 4 primiparous lactating Holstein cows were randomly assigned to 1 of 4 diets in a replicated 4 × 4 Latin square design. The diets contained (DM basis) 34.8% corn silage, 15.2% grass-legume silage, 5.9% roasted soybean, 2.4% mineral-vitamin premix, 2.0% alfalfa pellets, and either (1) 36% ground corn, 2.4% soybean meal, and 1.3% urea (UR), (2) 29.7% ground corn, 9.8% soybean meal, 0.13% ruminally protected (RP) Lys, and 0.07% RP-Met (CSBAA), (3) 25% ground field peas, 12.3% ground corn, and 2.4% soybean meal (FP), or (4) FP supplemented with 0.15% RP-Lys and 0.05% RP-Met (FPAA). Our objective was to test the effects of FP versus UR, FPAA versus CSBAA, and FPAA versus FP on milk yield and composition, N utilization, nutrient digestibility, ruminal fermentation profile, and plasma concentration of AA. Milk yield did not differ across diets. Compared with cows fed UR, those fed FP had greater DM intake, concentration and yield of milk true protein, apparent total-tract digestibility of fiber, urinary excretion of purine derivatives, and concentrations of total volatile fatty acids in the rumen and Lys in plasma, and less milk urea N and ruminal NH3-N. The concentration of milk urea N, as well as the concentration and yield of milk fat increased in cows fed FPAA versus CSBAA. Moreover, cows fed FPAA had greater ruminal concentration of total volatile fatty acids, increased proportions of acetate and isobutyrate, and decreased proportions of propionate and valerate than those fed CSBAA. The plasma concentrations of His, Leu, and Phe decreased, whereas plasma Met increased and plasma Lys tended to increase in cows fed FPAA versus CSBAA. Concentration of milk true protein, but not yield, was increased in cows fed FPAA versus FP. However, cows fed FPAA showed decreased concentrations of His and Leu in plasma compared with those fed FP. Overall, compared with the CSBAA diet, feeding FPAA did not negatively affect milk yield and milk protein synthesis. Furthermore, RP-Lys and RP-Met supplementation of the FP diet did not improve milk yield or milk protein synthesis, but decreased urinary urea N excretion.

Replacing alfalfa silage with tannin-containing birdsfoot trefoil silage in total mixed rations for lactating dairy cows

Two lactation trials were conducted comparing the feeding value of silages made from birdsfoot trefoil (BFT, Lotus corniculatus L.) that had been selected for low (BFTL), medium (BFTM), and high (BFTH) levels of condensed tannins (CT) to an alfalfa silage (AS) when fed as the principal forage in total mixed rations. Diets also included corn silage, high-moisture shelled corn, soybean meal, soy hulls, and supplemental fat. In trial 1, 32 lactating Holstein cows were blocked by days in milk, assigned to treatment sequences in 8 balanced 4 × 4 Latin squares, and fed 50% dietary dry matter from AS or 1 of 3 BFT silages containing 0.6, 1.2, or 1.7% CT. Diets averaged 17.5 to 19.5% crude protein and 26% neutral detergent fiber on a dry matter basis. Data were collected over the last 2 wk of each 4-wk period. Intakes were 1.3 to 2.8 kg of dry matter/d greater on BFT than on AS and cows gained 0.5 kg of body weight/d on BFT diets while losing 0.14 kg of body weight/d on the AS diet; this resulted in greater milk per dry matter intake (DMI) on AS. Linear effects indicated true protein yield and milk urea nitrogen declined with increasing CT concentration and quadratic effects indicated DMI, energy-corrected milk, and fat yield were increased at intermediate CT concentration. True protein yield and apparent N-efficiency were greater, and milk urea nitrogen lower, on all BFT diets than on AS. In trial 2, 50 lactating Holstein cows were fed a covariate AS diet for 2 wk and then blocked by parity and days in milk and randomly assigned to 1 of 5 diets that were fed continuously for 12 wk. Diets contained (dry matter basis) 48% AS, 16% AS plus 32% of 1 of 3 BFT silages with 0.5, 0.8, or 1.5% CT, or 48% of an equal mixture of each BFT silage. Diets averaged 16.5% crude protein and 30% neutral detergent fiber. Intake and milk yield tended to be lower on AS than BFT, but body weight gains averaged 0.6 kg/d on all diets. Cows fed any of the BFT silages had reduced milk urea nitrogen and ruminal ammonia and reduced urinary N excretion. Feeding the BFT mixture reduced concentrations of milk true protein and milk urea nitrogen and depressed apparent nutrient digestibility. Among diets containing the individual BFT silages, linear reductions in DMI and yield of milk, fat, true protein, lactose, and SNF were observed with increasing CT concentration. By contrast, a previous trial with the same BFT populations showed that substituting BFTH silage containing 1.6% CT for AS in rations containing 60% silage dry matter had no effect on intake, increased yield of milk, energy-corrected milk and milk components, elevated protein use-efficiency, but with a more modest reduction in milk urea nitrogen and urinary N excretion. Silage analyses suggested that the inconsistent responses among trials were related to growth environment or ensiling effects that altered tannin-protein interactions in BFT silage. Differences in diet formulation among trials may have also influenced responses. Results from the current and previous trials indicate further work is needed to identify optimum tannin levels in forages.

Effect of high-oleic-acid soybeans on production performance, milk fatty acid composition, and enteric methane emission in dairy cows

The objective of this study was to investigate the effect of 3 soybean sources differing in fatty acid profile and processing method on productivity, milk composition, digestibility, rumen fermentation, and enteric methane emission in lactating dairy cows. The soybean sources were conventional, high-linoleic-acid variety extruded soybean meal (ESBM; 8.7% ether extract with 15% oleic and 54% linoleic acids); extruded Plenish (DuPont Pioneer, Johnston, IA), high-oleic-acid variety soybean meal (EPSBM; 8.4% ether extract with 73% oleic and 8% linoleic acids); and whole, heated Plenish soybeans (WPSB; 20.2% ether extract). The study involved 15 Holstein cows in a replicated 3 × 3 Latin square design experiment with three 28-d periods. The inclusion rate of the soybean sources in the diet was (dry matter basis) 17.1, 17.1, and 7.4% for ESBM, EPSBM, and WPSB, respectively, which resulted in ether extract concentration of the diets of 3.99, 3.94, and 4.18%, respectively. Compared with ESBM, the Plenish diets tended to increase dry matter intake and decreased feed efficiency (but had no effect on energy-corrected milk feed efficiency). The Plenish diets increased milk fat concentration on average by 5.6% and tended to increase milk fat yield, compared with ESBM. The WPSB diet tended to increased milk true protein compared with the extruded soybean meal diets. Treatments had no effect on rumen fermentation and enteric methane or carbon dioxide emissions, except pH was higher for WPSB versus EPSBM. The Plenish diets decreased the prevalence of Ruminococcus and increased that of Eubacterium and Treponema in whole ruminal contents. Total-tract apparent digestibility of organic matter and crude protein were decreased by WPSB compared with ESBM and EPSBM. Compared with the other treatments, urinary N excretion was increased by EPSBM and fecal N excretion was greater for WPSB. Treatments had marked effects on milk fatty acid profile. Generally, the Plenish diets increased mono-unsaturated (mostly cis-9 18:1) and decreased polyunsaturated, total trans-, and conjugated linoleic fatty acids concentrations in milk fat. In this study, compared with conventional, high-linoleic-acid variety extruded soybean meal, the Plenish soybean diets increased milk fat concentration and tended to increase fat yield, decreased feed efficiency, and modified milk fatty acid profile in a manner expected from the greater concentration of oleic acid in Plenish soybean oil.

Effects of two yeast based direct fed microbials on performance of high producing dairy cows

Our aim was to determine effects of two S. cerevisiae yeast based direct fed microbial (DFM) feed additives on the productive response of high producing early lactation dairy cows. The study consisted of three high producing Holstein cow pens (±315 cows/pen) in a 3×3 Latin square design experiment with 3 periods of 28 d each. The 3 treatments were: (1) Basal total mixed ration (Control), (2) Control supplemented with ‘XPC’ yeast culture at 14g/cow/d and, (3) Control supplemented with ‘Yeasture (YST)’ DFM at 10g/cow/d. Milk (P=0.01), milk true protein (P=0.01), lactose (P=0.01) and energy (P=0.02) outputs were higher for YST cows, and there was a tendency for milk fat (P=0.07) to increase compared to Control cows. In contrast, milk and component yields were not impacted by feeding XPC. Total net energy (NE) output was higher for both DFM treatments vs. Control (YST (P<0.01) and XPC (P=0.01)), but neither treatment impacted the NE level of the diets. Total tract apparent digestibility of organic matter (OM) and crude protein (CP) tended to be lower (P=0.08 and 0.05) than Control for the XPC treatment, while total tract apparent digestibility of OM and CP for YST cows was lower (P=0.02 and<0.01 respectively) than Control. Total tract apparent digestibility of ash-free neutral detergent fibre (aNDFom) and starch were not affected by treatment, and there was no effect of either DFM treatment on microbial CP (MCP) flow from the rumen. Total plasma essential amino acid (EAA) concentrations tended to be higher (P=0.07) with YST, which was mainly driven by increases in threonine (P=0.03), tryptophan (P=0.02), valine (P=0.08) and histidine (P=0.06). Although total plasma non-essential amino acids (NEAA) did not differ with YST feeding, there was an increase in concentrations of glycine (P=0.04), asparagine (P=0.03), tyrosine (P=0.05), serine (P=0.07), proline (P=0.06) and taurine (P=0.07). In contrast, XPC had no impact on plasma concentrations of any AA. Overall, MCP flow and whole tract aNDFom data suggest no substantive impact of either yeast additive on rumen fermentation, but whole tract digestibility of OM and plasma AA concentrations suggest a post-ruminal effect of YST wherein gut health improved thereby leading to increased efficiency of nutrient absorption.

Casein infusion rate influences feed intake differently depending on metabolizable protein balance in dairy cows: A multilevel meta-analysis

The effects of casein infusion have been investigated extensively in ruminant species. Its effect on responses in dry matter intake (DMI) has been reviewed and indicated no significant effect. The literature reviewed in the current meta-analysis is more extensive and limited to dairy cows fed ad libitum. A total of 51 studies were included in the meta-analysis and data were fitted to a multilevel model adjusting for the correlated nature of some studies. The effect size was the mean difference calculated by subtracting the means for the control from the casein-infused group. Overall, casein infusion [average of 333g of dry matter (DM)/d; range: 91 to 1,092g of DM/d] tended to increase responses in DMI by 0.18kg/d (n=48 studies; 3 outliers). However, an interaction was observed between the casein infusion rate (IR) and the initial metabolizable protein (MP) balance [i.e., supply minus requirements (NRC, 2001)]. When control cows were in negative MP balance (n=27 studies), responses in DMI averaged 0.28kg/d at mean MP balance (−264g/d) and casein IR (336g/d), and a 100g/d increment in the casein IR from its mean increased further responses by 0.14kg/d (MP balance being constant), compared with cows not infused with casein. In contrast, when control cows were in positive MP balance (n=22 studies; 2 outliers), responses in DMI averaged −0.20kg/d at mean casein IR (339g/d), and a 100g/d increment in the casein IR from its mean further decreased responses by 0.33kg/d, compared with cows not infused with casein. Responses in milk true protein yield at mean casein IR were greater (109 vs. 65g/d) for cows in negative vs. positive MP balance, respectively, and the influence of the casein IR on responses was significant only for cows in negative MP balance. A 100g/d increment in the casein IR from its mean increased further responses in milk true protein yield by 25g/d, compared with cows not infused with casein. Responses in blood urea concentration increased in casein studies (+0.59mM) and the influence of the casein IR was greatest for cows in positive MP balance (0.26 vs. 0.11mM per 100g/d increment). Responses in DMI were also correlated negatively with responses in blood urea concentration only for cows in positive MP balance. Together, these results suggest an association between satiety and deamination and oxidation of AA supplied in excess of requirements for cows in positive MP balance. Therefore, casein stimulated appetite in cows fed MP-deficient diets possibly via the supply of orexigenic AA or through a pull effect in response to an increased metabolic demand. Conversely, casein induced satiety in cows fed diets supplying MP in excess of requirements. Not precluding other factors involved in satiety (e.g., insulin, gut peptides), casein could have increased the supply of AA (e.g., Ser, Thr, Tyr), which might depress appetite at the brain level or increase the deamination and the oxidation of AA in oversupply in agreement with the hepatic oxidation theory.

Effect of dietary crude protein and forage contents on enteric methane emissions and nitrogen excretion from dairy cows simultaneously

The study aimed to examine, simultaneously, the effects of changing dietary forage and crude protein (CP) contents on enteric methane (CH4) emissions and nitrogen (N) excretion from lactating dairy cows. Twelve post-peak lactating Holstein cows (157 ± 31 days postpartum; mean ± s.d.) were randomly assigned to four treatments from a 2 × 2 factorial arrangement of two dietary forage levels [37.4% (LF) vs 53.3% (HF) of DM] and two dietary CP levels [15.2% (LP) vs 18.5% (HP) of DM] in a 4 × 4 Latin square design with four 18-day periods. Alfalfa hay was the sole source of dietary forage. Cows were fed ad libitum and milked twice daily. During the first 14 days, cows were housed in a free-stall barn, where enteric CH4 emissions were measured using the GreenFeed system from Days 8 to 14 in each period. Cows were then moved to metabolic cages, where faeces and urine output (kg/cow.day) were measured by total collection from Days 16 to 18 of each period. No dietary forage by CP interactions were detected for DM intake, milk production, enteric CH4 emissions, or N excretions. There was a tendency for DM intake to increase 0.6 kg/day in cows fed LF (P = 0.06). Milk production increased 2.1 kg/day in LF compared with HF (P &lt; 0.01). Milk fat content decreased in cows fed LF compared with HF (1.07 vs 1.17 kg/day; P &lt; 0.01). Milk contents of true protein, lactose and solid non-fat were greater in cows fed LF (P &lt; 0.01). No difference in DM intake, milk yield and milk contents of true protein, lactose and solid non-fat was found between cows fed HP or LP. However, milk fat content increased 0.16 kg/day in cows fed HP (P &lt; 0.05). Enteric CH4 emissions, and CH4 per unit of DM intake, energy-corrected milk, total digested organic matter and neutral detergent fibre were not affected by dietary CP, but decreased by LF compared with HF (P &lt; 0.01). Milk true protein N was not affected by dietary CP content but was higher for LF compared with HF. Dietary N partitioned to milk true protein was greater in cows fed LF compared with HF (29.4% vs 26.7%; P &lt; 0.01), also greater in cows fed LP compared with HP (30.8% vs 25.2%; P &lt; 0.01). Dietary N partitioned to urinary N excretion was greater in cows fed HP compared with LP (39.5% vs 29.6%; P &lt; 0.01) but was not affected by dietary CP content. Dietary N partitioned to faeces was not affected by dietary CP but increased in cows fed LP compared with HP (34.2% vs 27.8%; P &lt; 0.01). Total N excretion (urinary plus faecal) as proportion to N intake did not differ between HP and LP, but tended to be lower in cows fed LF compared with the HF diet (64.2% vs 67.9%; P = 0.09). Both milk urea N (P &lt; 0.01) and blood urea N (P &lt; 0.01) declined with decreasing dietary CP or forage contents. Based on purine derivative analysis, there was a tendency for interaction between dietary CP and forage content on microbial protein synthesis (P &lt; 0.09). Rumen microbial protein synthesis tended to be lower for high forage and low protein treatments. Increasing dietary forage contents resulted in greater CH4 emission (g/kg of energy-corrected milk) and manure N excretion (g/kg of energy-corrected milk) intensities of lactating dairy cows. Cows receiving reduced CP diets had low manure N outputs and improved milk true protein production efficiencies, regardless of dietary forage content.

Impact of feeding reduced crude protein diets to lactating sows on nitrogen utilization1

Forty lactating multiparous Yorkshire sows were used to test the hypothesis that reducing dietary CP and supplementing with crystalline amino acids (CAA) increases dietary N utilization for milk production during early and peak lactation. Sows were assigned to 1 of 4 diets: 1) 16.0% CP (as-fed; analyzed contents; HCP); 2) 15.7% CP (MHCP); 3) 14.3% CP (MLCP); 4) 13.2% CP (LCP); diet HCP was formulated using soybean meal and corn as the only Lys sources. The reduced CP diets contained CAA to meet requirements of the limiting AA. Sow and piglet BW were measured on d 1, 3, 7, 14, 18, and 21 of lactation. Nitrogen retention was measured on sows between d 3 and 7 (early) and d 14 and 18 (peak) of lactation. Milk true protein output was calculated from estimated milk yield and analyzed true protein concentration. Sow BW change (overall mean: -4.2 ± 3.37 kg over the 21-d lactation period) and average daily DM intake (overall mean: 4.05 ± 0.18 and 6.12 ± 0.20 kg/d, early and peak lactation, respectively) did not differ between diets. Nitrogen intake decreased as dietary CP concentration decreased (114.3, 106.0, 107.4, and 99.0 ± 5.29 g/d and 169.5, 168.3, 161.2, and 145.1 ± 5.29 g/d for HCP, MHCP, MLCP, and LCP in early and peak lactation, respectively; L: < 0.05). Sow loin eye area loss tended to increase as dietary CP concentration decreased (Linear (): = 0.082). Litter growth rate (LGR) over the 21-d lactation period tended to increase with decreasing dietary CP concentration (L: = 0.084). In early lactation, N retention (N intake- fecal and urinary N) and milk true protein and casein output were not affected by dietary treatment. In early lactation, as dietary CP decreased, N retained as percentage of N intake tended to increase (L: = 0.093) and estimated efficiency of using retained N for milk N output was not influenced by dietary CP concentration. In peak lactation, N retention (122.5, 123.8, 121.2, and 109.0 ± 4.88 g/d for HCP, MHCP, MLCP, and LCP, respectively) decreased (L: < 0.05), N retained as percentage of N absorbed (N intake - fecal N) increased (L: < 0.05), milk casein yield increased ( = 0.051), and estimated efficiency of using retained N for milk N output (44.5, 51.0, 54.9, and 62.9 ± 5.9% for HCP, MHCP, MLCP, and LCP, respectively) increased (L: < 0.05). Feeding lactating diets reduced in CP from 16.0% to 14.3% with CAA inclusion as partial replacement for limiting AA improved N retention and N utilization efficiency for milk protein production in peak lactation, while these effects were less pronounced in early lactation.

Effects of feeding birdsfoot trefoil hay on neutral detergent fiber digestion, nitrogen utilization efficiency, and lactational performance by dairy cows

This experiment was conducted to determine effects of feeding birdsfoot trefoil hay-based diets in comparison with an alfalfa hay-based diet on N utilization efficiency, ruminal fermentation, and lactational performance by mid-lactation dairy cows. Nine multiparous lactating Holstein cows (131±22.6 d in milk), 3 of which were rumen fistulated, were fed 3 experimental diets in a replicated 3×3 Latin square design with 3 periods of 14 d of adaptation and 7 d of data and sample collection. Within squares, cows were randomly assigned to diets as follows: alfalfa hay-based diet (AHT), alfalfa and birdsfoot trefoil hay-based diet (ABT), and birdsfoot trefoil hay-based diet (BT). Intakes of dry matter and crude protein were similar across treatments, whereas ABT and BT diets resulted in decreased fiber intake compared with AHT. Feeding BT tended to increase neutral detergent fiber digestibility compared with AHT and ABT. Milk yield tended to increase for cows consuming ABT or BT diets. Milk true protein concentration and yield were greater for cows consuming ABT relative to those fed AHT. Concentration of total volatile fatty acids tended to increase by cows fed BT compared with those fed AHT and ABT. Feeding birdsfoot trefoil hay in a total mixed ration resulted in a tendency to decrease acetate proportion, but it tended to increase propionate proportion, leading to a tendency to decrease acetate-to-propionate ratio. Whereas concentration of ammonia-N was similar across treatments, cows offered BT exhibited greater microbial protein yield relative to those fed AHT and ABT. Cows offered birdsfoot trefoil hay diets secreted more milk N than AHT, resulting in improved N utilization efficiency for milk N. The positive effects due to feeding birdsfoot trefoil hay were attributed to enhanced neutral detergent fiber digestion, and thus it could replace alfalfa hay in high-forage dairy diets while improving N utilization efficiencies and maintaining lactational performance compared with alfalfa hay.

Replacing dietary soybean meal with canola meal improves production and efficiency of lactating dairy cows

Previous research suggested that crude protein (CP) from canola meal (CM) was used more efficiently than CP from solvent soybean meal (SBM) by lactating dairy cows. We tested whether dietary CP content influenced relative effectiveness of equal supplemental CP from either CM or SBM. Fifty lactating Holstein cows were blocked by parity and days in milk into 10 squares (2 squares with ruminal cannulas) in a replicated 5×5 Latin square trial. Five squares were fed: (1) low (14.5–14.8%) CP with SBM, (2) low CP with CM, (3) low CP with SBM plus CM, (4) high (16.4–16.7%) CP with SBM, and (5) high CP with CM; the other 5 squares were fed the same diets except with rumen-protected Met plus Lys (RPML) added as Mepron (Degussa Corp., Kennesaw, GA) and AminoShure-L (Balchem Corp., New Hampton, NY), which were assumed to provide 8g/d of absorbed dl-Met and 12g/d of absorbed l-Lys. Diets contained [dry matter (DM) basis] 40% corn silage, 26% alfalfa silage, 14 to 23% corn grain, 2.4% mineral-vitamin premixes, and 29 to 33% neutral detergent fiber. Periods were 3wk (total 15wk), and data from the last week of each period were analyzed using the Mixed procedures of SAS (SAS Institute Inc., Cary, NC). The only effects of RPML were increased DM intake and milk urea N (MUN) and urinary N excretion and trends for decreased milk lactose and solids-not-fat concentrations and milk-N:N intake; no significant RPML × protein source interactions were detected. Higher dietary CP increased milk fat yield and tended to increase milk yield but also elevated MUN, urine volume, urinary N excretion, ruminal concentrations of ammonia and branched-chain volatile fatty acids (VFA), lowered milk lactose concentration and milk-N:N intake, and had no effect on milk true protein yield. Feeding CM instead of SBM increased feed intake, yields of milk, energy-corrected milk, and true protein, and milk-N:N intake, tended to increase fat and lactose yields, and reduced MUN, urine volume, and urinary N excretion. At low CP, MUN was lower and intake tended to be greater on SBM plus CM versus SBM alone, but MUN and N excretion were not reduced to the same degree as on CM alone. Interactions of parity × protein source and parity × CP concentration indicated that primiparous cows were more responsive than multiparous cows to improved supply of metabolizable protein. Replacing SBM with CM reduced ruminal ammonia and branched-chain VFA concentrations, indicating lower ruminal degradation of CM protein. Replacing SBM with CM improved milk and protein yield and N-utilization in lactating cows fed both low- and high-CP diets.

The effect of high and low levels of supplementation on milk production, nitrogen utilization efficiency, and milk protein fractions in late-lactation dairy cows

To fill the feed deficit in the autumn/late lactation period in a seasonal grazing system, supplementation is required. This study aimed to investigate the use of baled grass silage or concentrate as supplementation to grazing dairy cows in late lactation. Eighty-four grass-based spring-calving dairy cows, averaging 212d in milk, were allocated to 1 of 6 treatments [high grass allowance (HG), low grass allowance (LG), grass with a low concentrate allocation (GCL), grass with a low grass silage allocation (GSL), grass with a high concentrate allocation (GCH), and grass with a high grass silage allocation (GSH)] to measure the effects of using baled grass silage or concentrate as supplements to grazed grass. Effects on intake, milk yield, milk composition and N fractions, and N utilization efficiency were measured. Treatments HG and LG received 17 and 14kg of dry matter (DM) grass/cow per d, respectively. Treatments GCL and GSL were offered 14kg of DM grass/cow per d and 3kg of DM of supplementation/cow per d. Treatments GCH and GSH were offered 11kg of DM grass/cow per d and 6kg of DM of supplementation/cow per d. Milk yield was greatest in the GCH treatment and milk solids yield was greatest in both concentrate-supplemented treatments. The HG and LG treatments excreted a greater quantity of N as a proportion of N intake than the supplemented treatments. The HG treatment also excreted the greatest total quantity of N. This indicates an improvement in N utilization efficiency when supplementation is offered compared with grazing only. Offering 6kg of DM of either grass silage or concentrate as supplementation decreased milk true protein concentration compared with offering a grass-only diet. This suggests that increasing the proportion of supplementation relative to grass may negatively affect milk processability, which is associated with milk true protein concentration.