Milk Urea Nitrogen Research Articles

Live yeast supplementation altered the bacterial community's composition and function in rumen and hindgut and alleviated the detrimental effects of heat stress on dairy cows.

The objective of this study was to investigate the effects of live yeast (LY, Saccharomyces cerevisiae) on the lactation performance, bacterial community, and functions in the rumen and hindgut of dairy cows under heat stress. Thirty-three multiparous (parity 3.9 ± 0.8) Holstein dairy cows (189.1 ± 6.6 d in milk at the beginning of the experiment) were randomly assigned to three groups (11 cows per treatment). Cows in the three groups were fed a diet without yeast (CON), with 10 g yeast/d/head (LY-10), and with 20 g yeast/d/head (LY-20). The yeast product contained 2.0 × 1010 CFU/g. Supplementing LY decreased the rectal temperature and respiratory rate of cows, and increased dry matter intake, milk yield, milk fat yield, milk protein yield, and milk lactose yield (P < 0.001), yet decreased milk urea nitrogen concentration (P = 0.035). Interaction effects of treatment × week were observed for rectal temperature (P < 0.05), respiratory rate (P < 0.05), milk yield (P = 0.015), milk urea nitrogen (P = 0.001), milk protein yield (P = 0.008), and milk lactose yield (P = 0.030). In rumen, LY increased the concentrations of acetate, isobutyrate, isovaterate, valerate, total volatile fatty acids (VFAs), and NH3-N (P < 0.05). Miseq sequencing of the 16S rRNA genes showed that LY increased the relative abundance of Prevotella and Prevotellaceae UCG-003 at the genus level with a series of enriched pathways in the metabolism of carbohydrates and protein. In fecal samples, LY did not affect the profile of VFAs (P > 0.05). Clostridium sensu stricto 1 (P = 0.013) and Actinobacillus (P = 0.011) increased in the relative abundance by LY, whereas Bacteroides (P = 0.016) and Oscillospirales UCG-010 (P = 0.005) decreased with a series of enriched pathways in carbohydrate metabolism, secondary bile acid biosynthesis. In summary, LY supplementation altered the bacterial community's composition and function in rumen and hindgut, and simultaneously alleviated the detrimental effects of heat stress on dairy cows. These findings provide extended insight into the effects of LY in the rumen and hindgut of dairy cows exposed to heat stress.

Associations of Lameness with Indicators of Nitrogen Metabolism and Excretion in Dairy Cows

The aim of the study was to investigate the impact of lameness on nitrogen (N) metabolism and excretion. Two treatment groups of 20 multiparous Holstein–Friesian dairy cows were included in study; the control group consisted of cows with locomotion score ≤2, while the experimental group consisted of cows with locomotion scores 3 and 4. Fodder, milk, feces, and urine were collected to determine nitrogen emissions. The milk yield, the energy-corrected milk, the fat and protein yield were higher for lame animals compare with non-lame cows. Differences were also detected in the milk urea nitrogen (MUN) between groups where lame cows had a 15% lower MUN than non-lame animals. Urine volume was lower (p &lt; 0.008), while urinary creatinine concentration was higher (p &lt; 0.05) in lame animals compare with those in the non-lame group. Consequently, the creatinine/urea ratio was significantly higher (p &lt; 0.001) in the lame vs. no-lame animals. Nitrogen excretion in milk was higher (p = 0.008) and N in urine was lower (p &lt; 0.001) in the lame compared to non-lame cows with lower urinary N emissions in lame animals. Taken together, our results show that urinary creatinine concentration and urinary creatinine/urea ratio have the potential to be used as a tool for lameness detection.

Evaluation of Urine Nitrogen Excretion as the Measure of the Environmental Load and the Efficiency of Nitrogen Utilization

Abstract The aim of this study was to evaluate the relationship between nutrition, the concentration of milk urea nitrogen (MUN) and the urinary nitrogen excretion in farm conditions and to use the MUN concentration as a tool to control protein nutrition and environmental load in dairy farming. Urinary N excretion was evaluated by an empirical model according to the intake and metabolic transformation of N to milk protein in selected farms was on average 208.8 ± 34.8 g with a range of values from 127.7 to 277.8 g N.day−1. The evaluated proportion of excreted N in relation to crude protein (CP) intake in the total mix ration (TMR) was statistically significant (R2 = 0.504; P &lt; 0.0001). Urinary N excretion, evaluated according to the analysis of the MUN content, using selected regression equations, was on average 211.8 ± 24.3 g.day−1 with an individual variation of 157.2‒274.7 g.day−1 with a significantly higher positive correlation to the received CP in the TMR (R2 = 0.693; P &lt; 0.0001). The evaluated effect of CP concentration in the TMR on urine N excretion confirmed the higher nitrogen excretion in the urine by 25.6 g per day with an increased CP in the TMR by 1 %. The proportion of urea nitrogen in the total N excreted in the urine was on average 80.5 %. The validation of the models for the prediction of nitrogen excretion, according to the MUN for the practical application on farms, was determined the best equation by Kaufmann a St-Pierre, which used available data from routine analysis of milk composition by the Breeding service of Slovakia. The MUN analysis offered a simple and non-invasive approach to the evaluation of the urinary N excretion, as well as, the efficiency of N utilization from feed to milk.

Efficacy of Grass and Concentrate Ratio on Milk Urea Nitrogen, Progesterone, and Pregnancy Status in Friesian Holstein

This study was conducted to know the influence of grass to concentrate ratio to milk urea nitrogen (MUN) level, progesterone level and pregnancy status in Friesian Holstein. A total of 18 dairy cows were randomly selected from the population. The cows were grouped based on feed and MUN and pregnancy. Milk sample collection was carried out once on the seventh day after estrus (D7) and tested with the Barthelot method for measuring urea nitrogen levels. Blood samples were taken three times, on the day of estrus (D0), seven days after estrus (D7), and twenty-two days after estrus (D22), and were tested using Immuno-Sorbent Assay (ELISA). Pregnancy examination was carried out at D90 after artificial insemination through rectal palpation. Based on the analysis, grass to concentrate ratio, progesterone level and MUN level showed no significant difference (p&gt;0.05) but it showed significantly different on milk yield (p&lt;0,05). Based on pregnancy status, progesterone level at D22 showed significantly different whereas at D0 and D7 showed insignificantly different. MUN level and grass to concentrate level also showed significantly different. It can be concluded that the ratio of grass and concentrate did not increase MUN level, progesterone level and pregnancy rate.

PSII-A-5 Effects of Time Postpartum and Late Gestational Nutrient Restriction on Beef Heifer Colostrum

Abstract Our objectives were to determine changes in colostrum yield and composition across the 36 hours post-calving and effects of late gestational nutrient restriction (NR) on these changes. Fall-calving, crossbred beef heifers (BW: 472 ± 33 [SD] kg; BCS: 5.4 ± 0.5) were individually fed 100% (control; CON; n = 13) or 70% (NR; n = 13) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, growth, and pregnancy from d 160 of gestation to parturition. Calves were removed from dams immediately post-calving and pre-suckling. Colostrum was hand-milked from all quarters at 1, 12, 24, and 36 h to determine total colostrum volume and weight. Colostrum protein, triglycerides, and milk urea nitrogen (MUN) concentration were analyzed using colorimetric assays on a UV-visible light microplate reader. Data were analyzed using fixed effects of treatment, hour, treatment × hour (repeated measures); calf sex, maternal sire, and treatment initiation date were covariates. Colostrum yield was affected (P &amp;lt; 0.02) by the treatment × hour interaction. Colostrum volume and weight were 28% less (P ≤ 0.03) for NR than CON at 1 h. For both treatments, colostrum volume and weight decreased (P ≤ 0.04) from 1 to 12 h, before increasing (P ≤ 0.02) from 12 to 36 h. Triglyceride concentration was greater (P = 0.03) in NR than CON. Both triglyceride concentration and total protein decreased (P ≤ 0.01) from 1 to 24 h. Protein concentration decreased (P &amp;lt; 0.001) from 1 to 36 h. Total triglycerides and MUN decreased (P &amp;lt; 0.001) from 1 to 12 h, before total MUN increased (P &amp;lt; 0.001) from 12 to 36 h and total triglycerides increased (P = 0.004) from 24 to 36 h. In conclusion, nutrient restriction may only affect colostrum yield at 1 h, and colostrum nutrient content decreases dramatically after the first milking.

PSVII-12 Efficacy of Formic Acid as a Silage Preservative on Dairy Cattle Performance

Abstract Formic acid (FOR) is a silage additive used to suppress growth of undesired bacteria. However, its effects on silage quality and dairy cattle performance have not yet been systematically reviewed. The objectives of this study were to conduct a systematic review and meta-analysis (1) to evaluate the efficacy of FOR as a silage additive on fermentation quality and (2) to evaluate the effects of silage preserved with FOR on dairy cattle performance. One hundred and fifty-three and twenty-eight research articles were reviewed for silage quality and dairy cattle performance. The data were analyzed using a mixed model, with random effects of study and fixed effect of treatment (formic acid) The raw mean difference (RMD) for each response variable, with 95% confidence interval, was calculated as the difference between FOR and control diets. The additives increased (P &amp;lt; 0.01) dry matter intake (RMD = 0.540 kg/d), milk yield (RMD = 0.453 kg/d), fat (RMD = 0.115 %) and protein (RMD = 0.075 %) concentrations. Milk urea nitrogen (RMD = -0.813 mg/dL) and lactose (RMD = -0.018 %) were reduced (P &amp;lt; 0.01) with the use of additives. Formic acid increased (P &amp;lt; 0.01) silage dry matter (DM) concentration (RMD = 6.06 g/kg DM), recovery (RMD = 2.30 % of DM), and in vitro digestibility (RMD = 19.1 g/kg DM), and water-soluble carbohydrates (RMD = 16.5 g/kg DM) concentration. The addition of FOR reduced (P &amp;lt; 0.001) silage pH (RMD = -0.226), ammonia-N (RMD = -37.3 g/kg of total nitrogen), lactic (RMD = -13.4 g/kg DM), acetic (RMD = - 11.5g/kg DM) and butyric (RMD = - 1.92 g/kg DM) acids. Formic acid-based additives ( &amp;gt;50% of FOR) improved silage quality and dairy cattle performance.

Evaluation of an ELISA for the diagnosis of bovine tuberculosis using milk samples from dairy cows in China

Bovine tuberculosis (bTB) is an important zoonotic disease in developing countries including China. Lack of rapid and simple detection methods for surveillance affects efficient control and eradication of this disease. The objective of this study was to determine the feasibility of using an individual and bulk milk sample ELISA based on the fusion protein of four specific antigens (CFP10/ESAT-6/MPB70/MPB83) of Mycobacterium bovis for the rapid detection and surveillance of bTB in dairy cattle herds and to identify individual animal factors that affect its results. The study population consisted of 388 dairy cows from four herds in Henan province, China. The serum sample ELISA (cut-off value 30%) and milk sample ELISA (cut-off value 10%) were shown to have good agreement, while, there was fair agreement between a blood sample IFN-γ in vitro release assay and the milk sample ELISA (cut-off value 10%) (Cohen’s kappa statistic of 0.492 and 0.306, respectively). The sensitivity and specificity for the milk sample ELISA using a S/P% cut-off value of 10%, as estimated using a Bayesian latent class analysis model, was 48.4% (95%CI: 31.0 – 85.2) and 97.1% (95%CI: 92.2 – 99.7), respectively. Although both ELISAs had comparable sensitivities and specificities, the milk sample ELISA had a greater discriminatory ability, as measured by the area under the curve (ROC), than the serum sample ELISA with the difference of their AUCs being − 0.069 (95%PCI: −0.121 to −0.021). Further, it was estimated that the lower limit of detection at an animal level lacto-prevalence might be 1.1% with this milk ELISA using bulk milk samples. Additionally, a mixed linear regression model, incorporating herd as a random effect variable, was constructed to investigate the association between natural log-transformed bTB sample-to-positive ratio (LnS/P%) and milk data. Across the model, natural log-transformed Somatic Cell Count (SCC) and parity had a positive effect on the LnS/P% of bTB antibody response, and milk urea nitrogen had a curvilinear association with LnS/P%. In conclusion, a milk ELISA for bTB antibodies, especially bulk tank milk antibodies, could be used as an efficient tool for rapid screening in surveillance, which might be followed by confirmatory testing with IFN-γ assay in dairy cattle, during the implementation of bTB control programmes. Relevant milk factors should be considered to adjust the S/P% with the aim of classifying the infection status of animals and herds as accurately as possible.

Bioconversion of agro-industrial residues as a protein source supplementation for multiparous Holstein Thai crossbreed cows.

The purpose of this field study was to compare the effects of top-dressing tropical lactating cows with soybean meal (SBM) or citric waste fermented yeast waste (CWYW) on intake, digestibility, ruminal fermentation, blood metabolites, purine derivatives, milk production, and economic return. Sixteen mid-lactation Thai crossbreeds, Holstein Friesian (16.7 ± 0.30 kg/day milk yield and 490 ± 40.0 kg of initial body weight) were randomly allocated to two treatments in a completed randomized design: SBM as control (n = 8) or CWYW (n = 8). The feeding trial lasted for 60 days plus 21 days for treatment adaptation. The results showed that total dry matter intake, nutrient intake, and digestibility did not (p>0.05) differ between SBM and CWYW top-dressing. Ruminal pH and the protozoal population did not (p>0.05) differ between SBM and CWYW top-dressing. After 4 hours of feeding, CWYW top-dressing showed greater ammonia nitrogen, plasma urea nitrogen, and bacterial population compared with the top-dressing of SBM. Volatile fatty acids and purine derivatives were not different (p>0.05) between SBM and CWYW top-dressing. For milk urea nitrogen, there was a greater (p<0.05) and somatic cell count was lower (p<0.05) for cows fed the CWYW top-dress compared to cows fed the SBM top-dress. The cost of the top-dress and total feed cost were less (p<0.05) for CWYW compared to SBM top-dressing, at 0.59 vs 1.16 US dollars/cow/day and 4.14 vs 4.75 US dollars/cow/day, respectively. In conclusion, CWYW could be used as an alternative protein source to SBM without having a negative impact on tropical lactating cows.

Loss of UHT milk quality: changes in compositional and physicochemical parameters triggered by different storage conditions

The objective of this study was to evaluate some compositional and physicochemical changes that occur during UHT (Ultra-high temperature) milk storage for up to four months. A total of 120 samples of UHT milk were collected from two dairy plants in the state of Minas Gerais, Brazil, and stored under two temperatures (20°C and 30°C) during five periods (0, 30, 60, 90 and 120 days). The experimental design was completely randomized, in a 2x2x5 factorial arrangement, with six replicates per treatment (six batches). Evaluated parameters included fat, total protein, casein, lactose, total solids, solids nonfat (SNF) and milk urea nitrogen (MUN) contents, as well as acidity, density, freezing point and indexes of lipolysis and caseinomacropeptide (CMP). When compared to the Brazilian requirements for UHT milk, the mean values ​​for acidity, fat and SNF contents were in accordance with the standards ​​until the last day of storage. The other parameters are still not covered by the specific UHT milk legislation in Brazil. There was no change of relative density and lactose content also remained constant, except for a decrease at the fourth month. A significant increase, over storage time, in acidity, MUN, lipolysis and CMP indexes occurred. On the other hand, there was a significant decrease in SNF and protein contents. The results showed that there was a gradual loss of quality during UHT milk storage, aggravated by the rise in temperature. These findings demonstrate that UHT milk legislation could be improved by adding parameters such as lipolysis and CMP indexes.

The Effects of High-Fat Diets from Calcium Salts of Palm Oil on Milk Yields, Rumen Environment, and Digestibility of High-Yielding Dairy Cows Fed Low-Forage Diet.

Simple SummaryCalcium salts of fatty acids from palm oil represent a very common supplement in dairy cows’ diets. The present results show that including up to 3.9% of CS-PFA in lactating cow rations with low fiber content did not affect milk and fat yields, decreased protein percentages and yields, reduced rumen fermentation, and decreased the total-tract apparent digestibility of NDF. In spite of the negative effects on rumen fermentation and digestibility, the adverse effects on yields were minor, which indicates that, under specific circumstances, feeding high-fat diets containing large amounts of CS-PFA to dairy cows fed low-fiber diets is possible.Instability in grain prices led to continuing worldwide growth in the proportion of fat supplements in lactating cows’ rations. However, fat supplementation was associated with decreases in feed intake, rumen fermentation, and feed digestibility. The present objectives were to test the effects of high-fat diets from calcium salts of palm oil fatty acids (CS-PFA) in lactating cow rations containing high proportions of concentrate, on feed intake, milk yields, rumen environment, and digestibility. Forty-two multiparous mid-lactation dairy cows were assigned to three treatments, designated as low fat (LF), moderate fat (MF), and high fat (HF) that contained (on DM basis), respectively, (i) 4.7% total fat with 1.7% CS-PFA, (ii) 5.8% total fat with 2.8% CS-PFA, and (iii) 6.8% total fat with 3.9% CS-PFA. Rumen samples were collected for pH, ammonia, and volatile fatty acid (VFA) measurements, and fecal grab samples were collected for digestibility measurements. A numerical trend of decreasing dry matter intake with increasing CS-PFA in diet was observed: 28.7, 28.5, and 28.1 kg/day in LF, MF, and HF, respectively (p < 0.20). No differences between treatments were observed in milk yields and milk-fat percentages, but protein percentage in milk tended to fall with increasing dietary CS-PFA content (p < 0.08), which resulted in 6.4% smaller protein yields in the HF than in the LF group (p < 0.01). Milk urea nitrogen was 15.3% higher in HF than in LF cows (p < 0.05). Rumen pH was higher at all sampling times in the MF and HF than in the LF cows. Concentrations of propionic acid and total VFA were higher in LF than in MF and HF cows. The apparent total-tract digestibility of dry matter was higher with LF than with HF (p < 0.002), and that of organic matter was lowest with the HF diet (p < 0.005). The apparent NDF digestibility declined with increasing dietary fat content, and it was 8.5 percentage points lower in HF than in LF cows (p < 0.009). Apparent fat digestibility increased with increasing dietary fat content, and it was higher by 10.4 percentage points in the HF than in the LF group (p < 0.004). In conclusion, diets with high concentrate-to-forage ratios, containing up to 6.8% total fat and 3.9% CS-PFA, negatively affected rumen fermentation and NDF digestibility in high-yielding dairy cows; however, the effects on yields were minor, indicating that, under specific circumstances, the inclusion of large amounts of CS-PFA in dairy cows’ rations with low fiber content is feasible.

Effect of Varying Dietary Crude Protein Level on Milk Production, Nutrient Digestibility, and Serum Metabolites by Lactating Donkeys.

Simple SummaryDonkey milk, a functional food, can be used as a milk replacement for newborn nutrition, due to its similar chemical composition to maternal breast milk and hypoallergenic property, and may be useful in the prevention of hypercholesterolemia and atherosclerosis. However, donkey milk yield is very low and cannot satisfy the demands of the market. Some research on dairy cows showed that increasing dietary crude protein levels can increase milk yield and milk component yields. Therefore, this study explored whether increasing dietary crude protein levels could promote the milk production of lactating donkeys. The results showed that increasing crude protein levels could improve milk performance and nutrient digestibility of lactating donkeys. The key finding of this study was that a diet containing 14.2% crude protein supplied adequate protein to improve milk production in lactating donkeys.Donkey milk is considered as a functional food due to its high levels of whey protein, and can be used in newborn nutrition, due to the nutritional similarities with human milk and its hypoallergenic property. However, donkey milk yield is very low and little is known about improving donkey milk yield by nutrition manipulation. The effect of dietary crude protein (CP) levels on milk production, nutrient digestibility, and serum metabolites was investigated in the current study. Twenty-four lactating donkeys were randomly assigned to one of the following three CP content diets: 15.3% (HP), 14.2% (MP), and 13.1% (LP) of dry matter, respectively. The experiment lasted for 10 weeks, with the first two weeks being used for adaptation. The results showed that milk yield and yields of protein, lactose, solid-not-fat, total solid, and contents of protein, total solid and milk urea nitrogen in the HP and MP groups were higher than the LP group. No significant changes were observed in dry-matter intake, contents of milk fat, lactose or solid-not-fat. The feed conversion ratio, milk protein synthesis efficiency, and the digestibility of dry matter, crude protein, ether extract, acid detergent fiber, neutral detergent fiber, calcium and phosphorous in the HP and MP groups were greater than the LP group. Serum total protein, albumin and urea nitrogen concentrations decreased, while concentrations of non-esterified fatty acids and β-hydroxybutyrate increased in the LP group compared with the HP and MP groups. In conclusion, the diet containing 14.2% CP supplied an adequate amount of protein for improving milk production in lactating donkeys, but milk production was not further increased by feeding the donkeys more than 14.2% CP.

The relationship of negative energy balance (NEB) and energy metabolism, milk production and reproductive performance during early lactation in dairy cows in Heilongjiang, China

Negative energy balance (NEB) causes economic losses to dairy farms around the globe. The aim of this study was to investigate the effect of NEB on energy metabolism, reproduction, etc. during early lactation in dairy cows on intensive farms in Heilongjiang, China. According to β- hydroxybutyric acid (BHBA), glucose (GLU), Non-esterified fatty acid (NEFA) levels, and clinical manifestations 14-21 days postpartum, 118 cows were divided into a positive energy balance (PEB) group (BHBA&lt;1.2, GLU&gt;2.8, NEFA&lt;0.7 mmol/L, n=67) and an NEB group (BHBA&gt;1.2, GLU&lt;2.8, NEFA&gt;0.7 mmol/L, n=51). These indicators were analyzed by cross-sectional research methods combined with Pearson correlation analysis and a prospective cohort study. The results showed that at 14-21 days postpartum, compared with the PEB, the body condition score, body condition loss (BCL), milk urea nitrogen, BHBA, NEFA, the interval from calving to first estrus (ICFE), pregnancy per artificial insemination (P/AI), and calving interval were higher (P&lt;0.05), and daily lactation (DL), milk protein and GLU, estrus rate and conception rate were lower in NEB cows. BCL was positively correlated with ICFE and P/AI (P&lt;0.05), and negatively correlated with estrus and conception rate (P&lt;0.05). DL was negatively correlated with the P/AI (P&lt;0.05). There was a positive association between NEB and anestrus (χ2 M-H=12.63, P=0.0004), the risk of anestrus caused by NEB rose by 3.67 times that of PEB. The conclusion showed that NEB is closely related to BCL, which is a factor in the decline of lactation and reproductive performance in dairy cows. NEB is a risk factor for anestrus in dairy cows.

Feed intake, rumen fermentation and performance of dairy cows fed diets formulated at two starch concentrations with either conventional urea or slow-release urea

This study evaluated the effects of high and moderate starch diets by substituting corn grain with wheat and rice bran in diets containing slow-release urea (SU, protected into lipids matrix microencapsulation) or conventional urea (CU) on the performance of high producing dairy cows. Twenty-four multiparous (days in milk = 83 ± 14; milk yield = 47 ± 4.5 kg/d) and sixteen primiparous (days in milk = 83 ± 12; milk yield = 37.5 ± 2.5 kg/d) Holstein dairy cows were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of treatments with 2 dietary starch concentrations [moderate starch (MS; 260 g/kg of dry matter, DM) vs. high starch (HS; 320 g/kg of DM)] and two sources of urea (SU vs. CU). The experiment lasted 52 days (d), consisting of 10 d for covariate period, 21 d for adaptation, and 21 d for sampling. In a preliminary in vitro gas test, the gas production was higher for SU than CU at 0.5, 1, 2, 6, and 24 h post-incubation (P < 0.01). There were interactions between urea source and starch level for dry matter intake (DMI, P < 0.01), propionate proportion (P = 0.04), milk urea nitrogen (MUN, P = 0.09) and rumen NH3-N (P = 0.07) concentrations; the DMI (P = 0.01) was higher and propionate proportion (P = 0.05), MUN (tendency, P = 0.08) and rumen NH3-N (tendency, P = 0.06) were lower with high than moderate starch level in CU diet, but it was not different between the two starch levels in SU diet. Furthermore, the urea source and starch level interaction was significant for butyrate proportion (P = 0.04); the butyrate proportion (P = 0.03) was lower with high than moderate starch level in SU diet, but it was not different between the two starch levels in CU diet. Cows fed CU had greater milk fat (P < 0.01) and protein (P = 0.04) yield and milk fat content (P = 0.05) and tended to have a greater 35 g/kg fat corrected milk yield (P = 0.09) than cows fed SU. The total volatile fatty acids concentrations (P = 0.04) and milk protein content (P < 0.01) were greater in HS-fed cows than in MS-fed cows. Blood urea nitrogen concentration was higher at 2 (P = 0.02) and 4 (P = 0.03) h after feeding in CU-fed cows than in SU-fed cows. Apparent digestibility of starch was greater in HS-fed cows than in MS-fed cows (P < 0.01) and in CU-supplemented cows than in those who received SU (P = 0.05). Overall, the SU product used in this study reduced the rate of ruminal nitrogen release compared to CU; however, no advantages are observed with the addition of SU when compared with CU on high-production dairy cow performance. Moreover, the results suggest that the performance of high-producing dairy cows can be maintained when wheat and rice bran are used instead of corn grains at 150 g/kg of DM.

Feasibility of Supplying Ruminally Protected Lysine and Methionine to Periparturient Dairy Cows on the Efficiency of Subsequent Lactation.

The objective of this study was to evaluate the effects of supplying ruminally protected Lys (RPL) and ruminally protected Met (RPM) to transition cows' diets on the efficiency of subsequent lactation. A total of 120 prepartum Holstein cows were assigned into four treatments blocked by the anticipated calving date, previous lactation milk yield, number of lactations, and body condition score and fed either RPL, RPM, or the combination (RPML) or control diet (CON) throughout the transition period (3 weeks before till 3 weeks after calving). From 22 to 150 days in milk (DIM), all animals (100 cows) were fed a combination of RPM and RPL (0.17% RPM and 0.41% RPL of DM; n = 25 cows/treatment) as follows; CON–RPML, RPM–RPML, RPL–RPML, and RPML–RPML. Milk production and dry matter intake (DMI) were measured daily; milk and blood samples were taken at 21, 30, 60, 90, 120, and 150 DIM. Supplemented amino acids (AA) were mixed with the premix and added to the total mixed ration during the experiment. DMI (p < 0.001) and energy-corrected milk (ECM, p = 0.04) were higher for cows that were fed RPML–RPML than other cows. Compared with CON–RPML, yields of milk total protein, lactose, and nitrogen efficiency were increased (p < 0.01), whereas milk urea nitrogen (MUN; p = 0.002) was decreased for other treatments. However, supplemental AA did not affect milk lactose percentage, fat yield, feed efficiency, or serum total protein concentration (p > 0.10). Transition cows that consumed AA had a greater peak of milk yield (p < 0.01), as well as quickly reached the peak of milk (p < 0.004). There were differences in β-hydroxybutyrate concentration during the early lactation, with a lower level for AA groups (p < 0.05), and the difference faded with the progression of lactation (p > 0.10). Fertility efficiency as measured by pregnancy rate was improved by supplemental AA during the perinatal period (p < 0.05). In conclusion, transition cows consumed RPM and RPL, increased post-calving DMI, milk production, milk protein yield, nitrogen efficiency, and improved fertility performance.

Performance and milk composition of Holstein cows fed increasing levels of dried distillers’ grains with solubles

The objective was to evaluate the performance and milk composition of cows fed diets containing dried distillers’ grains with solubles (DDGS). Five multiparous Holstein cows were distributed in a 5×5 Latin square. The treatments involved inclusion levels of 0%, 8%, 16%, 24%, and 32% of DDGS from corn in the diet. The inclusion of DDGS in the diet reduced the intake of dry matter (DM), crude protein (CP), and non-fibrous carbohydrates (NFC), and increased the intake of ether extract (EE) and neutral detergent fiber (NDF) (P < 0.05). However, the energy intake was unchanged, which can be explained by the increased digestibility of nutrients. There was a quadratic effect (P < 0.05) on digestibility of DM and NFC, and NDF digestibility increased linearly with the inclusion of DDGS in the diet. Possibly, the reduction of ingested DM promoted a decrease in the passage rate of feed through the gastrointestinal tract resulting in increased digestion. Ruminal microbial protein synthesis was not influenced by the treatments. The inclusion of DDGS promoted a linear increase in the concentration of cholesterol before feeding and in the concentrations of cholesterol and triglycerides four hours after feeding (P < 0.05). Milk production, energy corrected milk, protein content and milk urea nitrogen concentration were unchanged with the inclusion of DDGS in the diet. However, milk fat decreased linearly (P < 0.05) probably due to the high concentration of polyunsaturated fatty acids present in DDGS, that after incomplete biohydrogenation in the rumen form fatty acids responsible for the depression of milk fat. Thus, the inclusion of 32% DDGS from corn in the diet did not alter the performance of lactating cows, however, it reduced milk fat content.

Dry malt extract from barley partially replacing ground corn in diets of dairy cows: Nutrient digestibility, ruminal fermentation, and milk composition

Dry malt extract (DME) has been used in animal nutrition as an alternative source of rapidly fermentable carbohydrate. An experiment was conducted to evaluate the partial replacement of ground corn with DME in diets of dairy cows on apparent digestibility, ruminal fermentation, predicted rumen microbial protein supply, N excretion, serum urea-N concentration, and milk yield and composition. Twenty-eight Holstein cows (35.3 ± 5.88 kg/d milk yield and 148 ± 78 d in milk), 4 of which were rumen cannulated, were blocked according to the presence of rumen cannulas, parity, milk yield, and days in milk and enrolled into a crossover design experiment. Experimental periods lasted 21 d, of which the first 14 d were allowed for treatment adaptation and 7 d were used for data collection and sampling. Treatment sequences were composed of control (CON) or DME from barley (Liotécnica Tecnologia em Alimentos) replacing ground corn at 7.62% diet dry matter (~2 kg/d). Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc.) modeling the fixed effects of treatment, period, and their interaction, in addition to the random effect of animal. Ruminal fermentation data were analyzed as repeated measures including time and its interaction with treatment in the previous model as fixed effects. Treatments did not affect nutrient intake or feed sorting. Dry malt extract increased apparent digestibility of CP. Feeding DME decreased ruminal pH and molar percentage of butyrate and increased molar percentage of acetate. No treatment effects were detected for predicted rumen microbial protein supply or N excretion. Cows fed DME had lower serum urea-N concentration than CON cows. Dry malt extract increased yields of actual milk, 3.5% fat-corrected milk, fat, and protein, and improved feed efficiency (fat-corrected milk ÷ dry matter intake). Cows fed DME had lower milk urea nitrogen content in comparison with CON cows. Dry malt extract can partially replace ground corn in the diet while improving milk yield and feed efficiency.

Effects of methionine, leucine, and insulin on circulating concentrations and mammary extraction of energy substrates and amino acids in lactating dairy cows

The aim of this experiment was to test whether insulin potentiates the effects of two abomasally infused amino acids (AA), leucine and methionine (LM), on mammary extraction efficiency of energetic and nitrogenous nutrients. Six lactating Holstein cows (155 ± 9 DIM) were ruminally-cannulated and had the right carotid artery subcutaneously transposed. Cows were fed a 20% metabolizable protein-restricted diet and abomasally infused with water (8 L/d) or AA (Met 26 g/d, Leu 70 g/d) for 8 h/d, for 7 days. On the last day of each period, cows were intravenously infused with saline (0.9% NaCl, 110 mL/h) or subjected to 8 h hyperinsulinemic clamp (IC) alongside abomasal infusions. For IC, insulin was infused at 1 µg/kg/h. Normoglycemia was maintained by varying glucose (50% w/v in water) infusion rate based on coccygeal vein glucose concentration. Carotid arterial and subcutaneous abdominal (mammary) vein blood samples were collected at 0, 1, 2, 4, and 6 h from the start of infusions. Milk weights and samples for baseline measurements of production were taken on day 5 PM, day 6 AM and PM, and day 7 AM of the experimental period. A final milk weight and sample was taken immediately after abomasal and intravenous infusions on day 7 PM for assessing the interaction between insulin and the infused AA. The experiment had an incompletely replicated Latin square design with a 2 × 2 factorial arrangement of treatments (abomasal and intravenous infusion). Baseline milk production when cows were only receiving abomasal infusions was largely unaffected by LM, but milk protein yield tended to be decreased. On day 7, LM tended to positively increase milk fat and de novo fatty acid content, and IC tended to decrease milk protein content. Both milk urea nitrogen and plasma urea nitrogen were decreased by IC. Circulating AA concentrations in plasma were decreased by both LM and IC, but mammary extraction efficiency was affected by neither. Infusion of LM had no effect on any energy metabolite analyzed. Circulating non-esterified fatty acid concentration was decreased by IC, with no effect on mammary extraction efficiency. Mammary extraction efficiency of both acetate and β-hydroxybutyrate were decreased by IC. Overall, while both circulating concentrations of energy metabolites and amino acids were decreased in response to treatments, this was not due to improved mammary extraction efficiency.

Responses of Lactation, Rumen Fermentation and Blood Biochemical Parameters with Increasing Dietary Inulin Supplementation in Mid-Lactation Dairy Cows

Effects of dietary supplementation of inulin in dairy cows were investigated in this study. Thirty-six mid-lactation Holstein dairy cows were randomly divided into six groups with six cows per group and offered a total mixed ration supplemented with 0 (control), 50, 150, 200, 250 and 350 g/d inulin per head, respectively. The animals were pre-fed for 2 weeks before rumen fluid, milk and blood samples were collected weekly for 3 weeks. With increasing inulin doses, milk yield (p &lt; 0.01) and milk fat concentration (p = 0.04) were linearly increased, while milk urea nitrogen (p &lt; 0.01) and somatic cell count (p = 0.04) were linearly decreased. Linear increases were also detected in the proportions of milk saturated fatty acids (p &lt; 0.01) and polyunsaturated fatty acids (p = 0.04); however, milk monounsaturated fatty acids were linearly decreased (p = 0.04). The ruminal concentrations of acetate, propionate and butyrate increased, while the ruminal pH and the concentration of NH3-N reduced at a decreasing rate with increasing inulin doses (p &lt; 0.01). Moreover, the concentrations of lactic acid (p = 0.03) and total volatile fatty acids (p &lt; 0.01) were linearly upregulated. There were linear increases in the serum concentrations of superoxide dismutase (p = 0.02), immunoglobin G (p &lt; 0.01), immunoglobin M (p = 0.04), interleukin-2 (p &lt; 0.01) and interleukin-10 (p = 0.04); quadratic increases in serum total protein (p &lt; 0.01) and albumin (p = 0.02) and linear decreases in serum total cholesterol (p = 0.02), triglyceride (p &lt; 0.01) and malondialdehyde (p &lt; 0.01). The results indicated that inulin increased milk production, shifted milk fatty acid profile, upregulated rumen volatile fatty acid concentration, and enhanced antioxidant and immunity function in dairy cows in a dose-dependent manner.

Effect of TMR Briquettes on Milk Production, Nutrient Digestibility, and Manure Excretions of Dairy Cows in the Dry Zone of Sri Lanka.

Simple SummaryCompact total mixed ration (CTMR) is a feeding concept to promote nutrition and productivity in cattle. We compared the milk production and nutrient digestibility of cows fed a form of CTMR, TMR briquettes made of dried forages vs. a conventional diet including fresh-cut Guinea grass in the dry zone of Sri Lanka. Our findings showed that feeding TMR briquettes tended to increase dry matter intake (DMI) and milk yield by about 0.5 and 1.0 kg/d, respectively. The TMR briquettes were related to higher fibre digestibility and lower milk urea nitrogen (MUN) and urinary nitrogen excretions compared to the conventional diet.We showed previously that TMR briquettes made with a variety of forages and industrial by-products had higher crude protein and energy concentrations than the conventional diet including fresh-cut Guinea grass and commercial cattle pellet (CTL). The study objective was to determine to what extent the nutritional advantages of TMR briquettes would be translated into the milk production of dairy cows in the dry zone of Sri Lanka. Nine Jersey × Sahiwal cows were assigned to CTL or two TMR briquettes in a 3 × 3 Latin square design with three periods each including 14 d for production measurement and 7 d for total faeces and urine collection. The TMR briquettes tended to increase milk yield (5.55 to 6.59 kg/d, p = 0.092), milk protein yield (0.170 vs. 0.203 kg/d, p = 0.091) and DMI (6.50 to 7.16 kg/d, p = 0.070), and decreased milk urea nitrogen (13.0 to 10.5 mg/dL, p < 0.006). The TMR briquettes had a higher organic matter and neutral detergent fibre digestibility (p < 0.001), and lower urinary N excretions as a % of N intake (p = 0.149). In conclusion, the TMR briquettes can improve forage digestibility, milk production and environmental sustainability of dairy cows in the dry zone of Sri Lanka.

Nitrate supplementation at two forage levels in dairy cows feeding: milk production and composition, fatty acid profiles, blood metabolites, ruminal fermentation, and hydrogen sink

Abstract Nitrate may reduce the ruminal methane emission by competing methanogenesis to achieve more hydrogen. For this purpose, twenty Holstein lactating cows were examined using a 2×2 factorial design in 4 groups for 60 days with two forage levels (40% and 60%) and supplemental nitrate 0% (F40 and F60) and 3.5% (F40N and F60N) of diet dry matter (DM). Then, the effect of nitrate and forage levels on cow performance, ruminal fermentation, methane emission, and metabolic hydrogen sink were evaluated. The nitrate supplementation did not significantly affect milk yield and ECM/DMI, while milk urea nitrogen was increased. Lowest quantity of milk vitamins (A and E) was observed in nitrate groups. The nitrate supplementation increased c9-C18:1, unsaturated fatty acids, and n-6/n-3 contents of the milk. Blood parameters were affected by nitrate supplementation. Blood met-Hb concentration was increased, while blood glucose was decreased in nitrate groups. High forage and nitrate fed animals (F60N) had higher ruminal acetate and lower propionate concentration, and higher acetate+butyrate to propionate ratio than other groups. Nitrite and NH3-N concentrations were higher in the rumen of nitrate fed animals. Nitrate supplementation inhibited gas volume and methane emission without affecting volatile fatty acids at 12 and 24 h of incubation. The H2 balance, H2 production and consumption, and recovery percentage were significantly lower in F60N group. In conclusion, nitrate supplementation can be employed as an alternative strategy for improving ruminal fermentation, milk quality and methane inhibition.