Milk Urea Nitrogen Concentration Research Articles

Subclinical mastitis in Jersey dairy cows and its effects on productivity and inflammatory markers

This study assessed the effect of subclinical mastitis on the productivity and inflammatory markers in Jersey dairy cows. Blood, milk, and milk yield data were collected from 59 Jersey dairy cows reared under a semi-extensive system. Milk samples were collected from individual collectors and evaluated for their somatic cell count (SCC), lactose (Lact), protein, fat, total and defatted dry extracts (DDE), casein, freezing point, and milk urea nitrogen (MUN) levels. After milking, blood was collected by puncturing the coccygeal arteriovenous complex. In the serum samples, the inflammatory biomarkers paraoxonase-1, albumin, and total plasma protein levels were analyzed using colorimetric methods. Samples of the entire diet provided and pastures were submitted for bromatological analysis. Additionally, the body condition score, number of lactations, milk yield, days of lactation, calving interval, number of inseminations until conception, calving-conception interval, and days of pregnancy were analyzed. The cows were categorized based on their SCC into a subclinical mastitis group (SubG), with SCC levels greater than or equal to 200,000 cells/mL, and a control group (CG), with SCC levels below 200,000 cells/mL. Blood metabolic variables, milk quality, and milk production data were analyzed using multivariate regression, analysis of variance, and logistic regression using the SAS® program. The multivariate regression analysis revealed that several markers, such as Lact, total protein, and casein, influenced milk composition, predicting over 97% of the data. The SubG showed lower concentrations of Lact (4.37 vs. 4.47%; P = 0.0002), MUN (20.55 vs. 23.85 mg/dL; P = 0.02), and DDE (9.24 vs. 9.50%; P = 0.02) compared with the CG; moreover, animals in the SubG had a higher number of lactations compared with those in the CG (4.30 vs. 2.69; P = 0.0039). Cows with a Lact content lower than 4.265% (quartile 25%), compared with those with Lact content greater than 4.565% (quartile 100%), were 52 times more likely to have subclinical mastitis. Jersey dairy cows with subclinical mastitis have lower Lact, urea, and defatted dry extract levels in their milk as well as a higher number of lactations. Therefore, Lact levels in milk serve as a good diagnostic marker of subclinical mastitis in Jersey cows. Subclinical mastitis in Jersey dairy cows did not decrease milk yield nor effect reproductive performance.

Effects of one-hour daily outdoor access on milk yield and composition and behaviors of tethered dairy cows.

We investigated the effects of outdoor access for one-hour per day (ODA) on milk yield and composition and behaviors of tethered dairy cows. Eleven all-day tethered dairy cows were treated the ODA for two weeks. To evaluate the effect of ODA on milk yield, we first calculated the average daily milk yield of each cow for three days during two weeks before the ODA, three days before the ODA, three days at the end of the ODA, and three days during two weeks after the ODA. We then compared the milk yield change during the ODA with that for two weeks before and two weeks after the ODA. The effects of ODA on milk compositions and behaviors were evaluated by comparing the average values for each composition and behavior for the three days before the ODA and the last three days of the ODA. The decrease of milk yield during the two weeks of ODA was significantly higher than that during the two weeks before ODA (p<0.01). The milk fat rate was significantly higher during ODA than before ODA (p<0.05). Lactose rate was significantly lower during ODA than before ODA (p<0.05). The concentrations of milk urea nitrogen, ketone bodies, and free fatty acids in the milk were significantly higher during ODA than before ODA (p<0.05). The mean total duration per day of lying during ODA was significantly lower than that before ODA (p<0.05). The walking steps per one-hour outdoor access were 158.4 ± 54.7. The social behavior during the one-hour outdoor access of the 11 cows was 53 times/h/herd. . Our results suggested that ODA promotes the express of normal behavior in dairy cows, but even one hour of ODA decreases milk production in cows, which may drop producers' profits without some financial supplementation.

Compound probiotics microcapsules improve milk yield and milk quality of dairy cows by regulating intestinal flora

AbstractTo address the issues of probiotic activity loss during storage and feeding, as well as the limited efficacy of single probiotics, a solution was devised by embedding a mixture of Bacillus coagulans SN‐8 (SN‐8) and Saccharomyces boulardii SN‐6 (SN‐6) in a gel. The initial step involved screening the probiotic microcapsules' preparation method and wall material. Using sodium alginate and β‐cyclodextrin as composite wall material and chitosan as the outer coating material allowed for an embedding rate of 82.11% in composite probiotic microcapsules prepared by the air atomization method. Next, in vitro, simulated digestion experiments were conducted to determine the number of viable bacteria and the release rate of the microcapsules. The results showed that compared to the free strain, the mixed probiotic microcapsules retained a survival rate of 67.5% after 3 h of simulated gastric juice exposure and 70.56% after 42 days of storage at 4°C. This demonstrated higher survival rates and storage stability. The prepared probiotic microcapsules were then administered to dairy cows. 16S rDNA gene sequencing showed that consumption of the microcapsules reduced the number of harmful bacteria, such as Paeniclostridium, in the intestinal tract of dairy cows while accelerating the growth of beneficial bacteria, such as Bifidobacterium. In particular, this resulted in a significant improvement in the lactation performance of the cows, with a 4.5% increase in milk fat content, a 92.5% increase in milk protein content, and a 3.5% increase in milk urea nitrogen content (6.75 mL/dL). In conclusion, probiotic microcapsules can effectively regulate intestinal flora, improving milk production, and quality in dairy cows.

Effects of heating soybeans on postruminal amino acid bioavailability, performance, and ruminal fermentation in lactating cows.

Soybeans can provide ruminally degradable protein, lipid, and metabolizable amino acid (AA) to lactating dairy cows; however, soy-based trypsin inhibitors can limit protein digestion in nonruminants. Eight ruminally cannulated lactating Holstein cows were used to evaluate the impacts of soy-based trypsin inhibitors on nutrient disappearance, lactation, and plasma AA bioavailability. Treatments were abomasal infusion of 0 or 400g/d casein or a crystalline AA analog of casein with unroasted or roasted soybeans fed at 10% dry matter (DM). Data were analyzed using the MIXED procedure of SAS. Measures of digestion were determined from fecal output determined with acid detergent insoluble ash and urine output determined from measures of urine creatinine. Neither soybean processing (P ≥ 0.20) nor the source of abomasal infusion (P ≥ 0.60) impacted nutrient digestibility. Ruminal ammonia, isobutyrate, and isovalerate were increased (P ≤ 0.01) among cattle consuming unroasted soybeans. Source of infusion did not affect (P ≥ 0.38) ruminal volatile fatty acids or nitrogen metabolism. Ruminal N metabolism was largely unaffected by soybean processing although microbial N efficiency was greater (P < 0.01) among cows fed unroasted soybeans. DM intake and energy-corrected milk were greater (P < 0.01) in cows fed roasted compared to unroasted soybeans. The proportion of fat, protein, lactose, and solids not fat (SNF) in milk did not differ between soybean processing or postruminal AA source, but fat, protein, lactose, and SNF yield was greater (P ≤ 0.01) when cows were fed roasted soybeans because milk yields were greater when cows were fed roasted vs. unroasted soybeans. As expected, infusion of casein or its crystalline AA analog increased plasma essential AA and milk urea nitrogen concentration. The rate of increase in essential AA concentration in plasma was 2.9× greater for casein than for crystalline AA. These data seem to indicate that soy-based trypsin inhibitors have no impacts on postruminal AA bioavailability when fed to cows and that metabolizable protein from casein is greater than from crystalline AA.

Intravenous infusion of 5-hydroxytryptophan to mid-lactation Holstein cows transiently affects milk production and circulating amino acid concentrations

In dairy cows, the lactating mammary glands synthesize serotonin, which acts in an autocrine-paracrine manner in the glands and is secreted into the periphery. Serotonin signaling during lactation modulates nutrient metabolism in peripheral tissues such as adipose and liver. We hypothesized that the elevation of circulating serotonin during lactation would increase nutrient partitioning to the mammary glands, thereby promoting milk production. Our objective was to elevate circulating serotonin via intravenous infusion of the serotonin precursor 5-hydroxytryptophan (5-HTP) to determine its effects on mammary supply and extraction efficiency of AA, and milk components production. Twenty-two multiparous mid-lactation Holstein cows were intravenously infused with 5-HTP (1 mg/kg body weight) or saline, in a crossover design with two 21-d periods. Treatments were infused via jugular catheters for 1 h/d, on d 1 to 3, 8 to 10, and 15 to 17 of each period, to maintain consistent elevation of peripheral serotonin throughout the period. Milk and blood samples were collected in the last 96 h of each period. Whole-blood serotonin concentration was elevated above saline control for 96 h after the last 5-HTP infusion. Dry matter intake was decreased for cows receiving 5-HTP, and on average they lost body weight over the 21-d period, in contrast to saline cows who gained body weight. Milk production and milk protein yield were lower in cows receiving 5-HTP during the 3 infusion days, but both recovered to saline cow yields in the days after. Although milk fat yield exhibited a day-by-treatment interaction, no significant difference occurred on any given day. Milk urea nitrogen concentration was lower in 5-HTP cows on the days following the end of infusions, but not different from saline cows on infusion days. Meanwhile, plasma urea nitrogen was not affected by 5-HTP infusion. Circulating concentrations of AA were overall transiently decreased by 5-HTP, with concentrations mostly returning to baseline within 7 h after the end of 5-HTP infusion. Mammary extraction efficiency of AA was unaffected by 5-HTP infusion. Overall, both lactation performance and circulating AA were transiently reduced in cows infused with 5-HTP, despite sustained elevation of circulating serotonin concentration.

Exploring the heights: Impact of altitude on dairy milk composition

The aim of the present study was to assess the impact of altitude on the quality of milk from dairy cows housed in small-scale farms in alpine areas. Therefore, a dataset comprising 5,680 bulk milk samples from 32 farms located at different geographical altitudes was considered. Milk traits such as fat, protein, lactose, free fatty acids, casein, milk urea nitrogen content, pH value, and somatic cell score were examined in the laboratories of the South Tyrolean Dairy Association using mid-infrared spectroscopy. The data were analyzed using a statistical model that considered altitude category, grazing practice, housing system, and season of milk analysis as fixed effects. The findings revealed a positive association between altitude and milk fat, free fatty acids, and somatic cell count. Conversely, lactose content, milk urea nitrogen, and pH value in milk from cows kept on farms at higher altitude (>1,200 m above sea level) showed a negative relationship with altitude. Farms located at altitudes above 1,200 m exhibited higher fat, protein, urea, and somatic cell content than farms located at lower levels. The results provide new insights into a production effect that has so far received little attention and should be considered in farm management (e.g., feeding management, breed decision) to ensure animal health and the associated animal welfare as well as the productivity of dairy cows reared in traditional small-scale mountain dairy farms.

Effect of monensin on milk production efficiency and milk composition in lactating dairy cows fed modern diets

Since the US Food and Drug Administration's approval of monensin in 2004, significant nutritional advances have been made to increase feed efficiency and milk fat production. Recent evidence suggests monensin's adverse effect on milk fat percentage may be absent when diets are formulated to address known diet-induced milk fat depression risk factors. Thus, study objectives were to evaluate effects of monensin level on dry matter intake (DMI), milk production and composition, and efficiency of high-producing cows fed diets formulated to optimize milk fat. Ninety-six lactating Holstein cows (36 primiparous, 60 multiparous; 106 ± 17 d in milk [DIM]) were balanced by parity, DIM, and milk production and were randomly assigned to 1 of 12 pens with 8 cows per pen. All cows received 11 g/t monensin for 5 wk after which pens received 1 of 4 dietary treatments (n = 3) formulated to provide 0 (CON), 11 (R11), 14.5 (R14.5), or 18 (R18) g/t monensin for 9 wk. The basal diet was 54% forage, 27% NDF, 29% starch, and 2.3% rumen unsaturated fatty acid load. Pen was the experimental unit and data were analyzed using the Fit Model Procedure of JMP. Effects of treatment, time, and treatment × time interaction were included as fixed effects and pen as a random effect. Least squares means were determined and linear and quadratic contrasts were tested. Dry matter intake tended to decrease linearly with increasing monensin dose. Milk yield, fat percentage, and protein percentage and yield were unaffected by treatment while fat yield was quadratically increased. Milk de novo and mixed fatty acid (FA) yields (g/d) increased quadratically with monensin whereas preformed FA linearly decreased during the experimental period. Energy-corrected milk (ECM) was quadratically increased by monensin. Milk urea nitrogen concentrations increased linearly with increasing monensin dose. Monensin linearly increased feed efficiency (ECM/DMI, 3.5% fat-corrected milk/DMI, and solids-corrected milk/DMI). Body weight gain did not differ between treatments. Estimated dietary energy tended to increase linearly with increasing monensin level. These data suggest monensin improves component-corrected milk production efficiency, estimated dietary energy, and does not negatively affect milk fat percentage or FA profile.

Dietary Neutral Detergent Fiber Levels Impacting Dairy Cows' Feeding Behavior, Rumen Fermentation, and Production Performance during the Period of Peak-Lactation.

This study investigated the impact of dietary neutral detergent fiber (NDF) levels (25.49%, 28.65%, 31.66%, and 34.65%, respectively) on the feeding behavior, rumen fermentation, cellulolytic bacteria, and production performance of dairy cows during peak lactation. A feeding experiment was conducted using four fistulated Holstein dairy cows (600 ± 25 kg) with days in milk (50 ± 15 days), employing a 4 × 4 Latin square design to assign the cows to four groups. The results demonstrated that increasing NDF levels in the diet had the following effects: (1) A linear decrease in dry matter intake (DMI), NDF intake, and physically effective NDF8.0 (peNDF8.0) intake; a linear increase in the average time spent eating and ruminating, as well as the time spent eating and ruminating per kilogram of dry matter (DM); a quadratic response in the time spent ruminating per kilogram of NDF and peNDF8.0. (2) A linear increase in average pH value, acetate concentration, and the proportions of Fibrobacter succinogenes and Ruminococcus flavefaciens among total bacteria; a linear decrease in ammonia nitrogen (NH3-N) concentration, microbial crude protein (MCP), total volatile fatty acid (TVFA), propionate, butyrate, and lactate. (3) A linear decrease in milk yield, milk protein percentage, and nitrogen efficiency of dairy cows; a linear increase in milk fat percentage and milk urea nitrogen (MUN) concentration. Based on the combined results, it was found that diets with 25% and 34% NDF had detrimental effects on the feeding behavior, rumen fermentation, and production performance of dairy cows. However, the diet with 28% NDF showed superior outcomes in production performance compared to the one with 31% NDF. Therefore, it is strongly recommended to include a diet containing 28% NDF during the critical peak lactation period for dairy cows.

Effects of Bacillus subtilis PB6 supplementation on production, metabolism, inflammatory biomarkers, and gastrointestinal tract permeability in transition dairy cows

Objectives were to evaluate the effects of Bacillus subtilis PB6 (BSP) on gastrointestinal tract permeability, metabolism, inflammation, and production parameters in periparturient Holstein cows. Multiparous cows (n = 48) were stratified by previous 305-d mature equivalent milk yield and parity and assigned to 1 of 2 top-dressed dietary treatments 21 d before expected calving through 63 DIM: (1) control (CON; 13 g/d calcium carbonate; n = 24) or (2) BSP (13 g/d BSP; CLOSTAT, Kemin Industries, Des Moines, IA; n = 24). Gastrointestinal tract permeability was evaluated in vivo using the oral paracellular marker chromium (Cr)-EDTA. Effects of treatment, time, and treatment × time were assessed using PROC MIXED of SAS version 9.4 (SAS Institute Inc.). Prepartum dry matter intake (DMI) was unaffected by treatment; however, BSP supplementation decreased postpartum DMI relative to CON (0.7 kg). Milk yield, energy-corrected milk (ECM), fat-corrected milk (FCM), and solids-corrected milk (SCM) increased in BSP cows compared with CON (1.6, 1.8, 1.6, and 1.5 kg, respectively). Decreased DMI and increased production collectively improved feed efficiency of milk yield, ECM, FCM, and SCM for BSP cows (6, 5, 5, and 5%, respectively). No treatment differences were observed for concentrations of milk fat, protein, total solids, somatic cell count, somatic cell score, body weight, or body condition score. Milk urea nitrogen concentrations decreased (5%), whereas milk protein and lactose yield increased (5 and 2%, respectively) with BSP supplementation. Prepartum fecal pH did not differ among treatments; conversely, postpartum fecal pH was increased with BSP supplementation (0.09 pH units). Prepartum fecal dry matter percentage, starch, acetic acid, propionic acid, butyric acid, and ethanol did not differ among treatments. Postpartum concentrations of the aforementioned fecal parameters were also unaffected by treatment, but fecal propionic acid concentration was decreased (24%) in BSP cows relative to CON. Circulating glucose, nonesterified fatty acids, l-lactate, and insulin were similar between treatments both pre- and postpartum. Prepartum β-hydroxybutyrate (BHB) did not differ between treatments, but postpartum BSP supplementation decreased (21%) circulating BHB relative to CON. Regardless of treatment, inflammatory markers (serum amyloid A and haptoglobin) peaked immediately following parturition and progressively decreased with time, but this pattern was not influenced by treatment. Postpartum lipopolysaccharide binding protein tended to be decreased on d 3 in BSP relative to CON cows (19%). Neither treatment nor time affected Cr-EDTA area under the curve. In summary, supplementing BSP had no detectable effects prepartum, but increased key postpartum production parameters. Bacillus subtilis PB6 consistently increased postpartum fecal pH and decreased fecal propionate concentrations but did not appear to have an effect on gastrointestinal tract permeability.

Bioavailability of a novel rumen protected methionine supplement and its effect on milk production and body composition in dairy cows

Our objective was to evaluate the bioavailability of a rumen-protected Met product (EMT 3.4) using milk selenium (Se) marker method and its impact on milk production and body composition in dairy cows. Twelve multiparous Holstein cows (82 ± 27 days in milk, 38.7 ± 3.4 kg/d of milk; mean ± SD) were used in a replicated 3 × 3 Latin-square design with 21 d periods. Prior to the study, cows were fed Se-yeast for 2 wk to reach stable milk Se concentration. Treatments were 1; a negative control diet (NCT) providing 100% of the metabolizable protein (MP) requirement and 90% of the metabolizable Lys and Met requirements, 2; a positive control diet (PCT) providing 101% of the MP, and 110% of the Met and Lys requirements (Met supplied by Smartamine M, Adisseo), and 3; an experimental Met treatment (EMT; Met supplied by EMT 3.4, Ajinomoto Inc.) that was formulated to provide 101% of the MP, and 110% of the metabolizable Met and Lys requirements (AMTS.Cattle.Professional utilizing CNCPS 6.5.5 models). The NCT cows were not supplemented with additional Met or Lys, whereas supplemental Lys for both the EMT and PCT diets was supplied by Aji-Pro L (Ajinomoto). The PCT and EMT treatments decreased milk Se-to-N ratio (i.e. bioavailability; Se:N), by 11% and 9.5% respectively compared with NCT (P < 0.05). The PCT increased DMI and tended to increase milk yield compared to NCT and EMT. The PCT treatment increased yields of milk protein, solids, lactose, and milk lactose concentration compared to NCT and EMT treatments. The EMT treatment increased milk urea nitrogen (MUN) concentration compared with NCT and PCT. However, the potential for milk Se to be inconsistently diluted due to differences in MUN and DMI poses challenges with interpretation. The lack of measurable production responses when supplementing EMT compared to NCT, may indicate less bioavailable Met than the bioavailability calculation assumes.

Effect of nitrate supplementation, dietary protein supply, and genetic yield index on performance, methane emission, and nitrogen efficiency in dairy cows

The objective was to investigate the effect of nonprotein nitrogen source, dietary protein supply, and genetic yield index on methane emission, N metabolism, and ruminal fermentation in dairy cows. Forty-eight Danish Holstein dairy cows (24 primiparous cows and 24 multiparous cows) were used in a 6 × 4 incomplete Latin square design with 4 periods of 21-d duration. Cows were fed ad libitum with the following 6 experimental diets: diets with low, medium, or high rumen degradable protein (RDP):rumen undegradable protein (RUP) ratio (manipulated by changing the proportion of corn meal, corn gluten meal, and corn gluten feed) combined with either urea or nitrate (10 g NO3-/kg of dry matter) as nonprotein nitrogen source. Samples of ruminal fluid and feces were collected from multiparous cows, and total-tract nutrient digestibility was estimated using TiO2 as flow marker. Milk samples were collected from all 48 cows. Gas emission (CH4, CO2, and H2) was measured by 4 GreenFeed units. We observed no significant interaction between dietary RDP:RUP ratio and nitrate supplementation, and between nitrate supplementation and genetic yield index on CH4 emission (production, yield, intensity). As dietary RDP:RUP ratio increased, intake of crude protein, RDP, and neutral detergent fiber and total-tract digestibility of crude protein linearly increased, and RUP intake linearly decreased. Yield of milk, energy-corrected milk, and milk protein and lactose linearly decreased, whereas milk fat and milk urea nitrogen concentrations linearly increased as dietary RDP:RUP ratio increased. The increase in dietary RDP:RUP ratio resulted in a linear increase in the excretion of total purine derivatives and N in urine, but a linear decrease in N efficiency (milk N in % of N intake). Nitrate supplementation reduced dry matter intake (DMI) and increased total-tract organic matter digestibility compared with urea supplementation. Nitrate supplementation resulted in a greater reduction in DMI and daily CH4 production and a greater increase in daily H2 production in multiparous cows compared with primiparous cows. Nitrate supplementation also showed a greater reduction in milk protein and lactose yield in multiparous cows than in primiparous cows. Milk protein and lactose concentrations were lower for cows receiving nitrate diets compared with cows receiving urea diets. Nitrate supplementation reduced urinary purine derivatives excretion from the rumen, whereas N efficiency tended to increase. Nitrate supplementation reduced proportion of acetate and propionate in ruminal volatile fatty acids. In conclusion, no interaction was observed between dietary RDP:RUP ratio and nitrate supplementation, and no interaction between nitrate supplementation and genetic yield index on CH4 emission (production, yield, intensity) was noted. Nitrate supplementation resulted in a greater reduction in DMI and CH4 production, and a greater increase in H2 production in multiparous cows than in primiparous cows. As the dietary RDP:RUP ratio increased, CH4 emission was unaffected and RDP intake increased, but RUP intake and milk yield decreased. Genetic yield index did not affect CH4 production, yield, or intensity.

Efeito do estresse calórico e da insolação sobre consumo, indicadores bioquímicos, produção e qualidade do leite de vacas Holandês e Jersey

ABSTRACT The objective of this work was to compare the dry matter intake, milk yield and quality, physiological and biochemical parameters in Holstein (n=10) and Jersey (n=10) cows under heat stress and insolation, in two treatments: CL - cooling by ventilation and sprinkling and HS - heat stress and insolation. Data were submitted to ANOVA. There was an interaction between treatment and breed and day effect for dry matter intake. For consumption in % of body weight, CL and Jersey cows consumed more. CL cows produced more milk and 3.5% fat-corrected milk. Feed efficiency was similar between treatments and breeds. Fat, lactose, total solids, and somatic cell score did not differ. The concentration of milk urea nitrogen was higher for CL cows. Milk from Holstein cows had greater stability to alcohol, and from HT cows had a greater freezing point of milk. HT cows had higher respiratory rates in the morning and surface temperatures in the afternoon. There were no differences in beta-hydroxybutyrate and glucose concentrations. Heat stress, with insulation, reduces intake, especially in Holstein cows, as well as milk production and increases the freezing point of milk, respiratory rate, and surface temperature.

Feeding phytogenic ingredients combined or not with Lithothamnium calcareum and a mycotoxin binder to lactating cows: Effects on performance, nutrient digestibility, physiological parameters, and nitrogen excretion

A study was conducted to evaluate the effects of phytogenic feed additives combined or not with buffer compounds and a mycotoxin binder on performance, nutrient digestibility, N utilization, and purine derivatives excretion in lactating cows. Thirty-six Holstein (162 ± 76 days in milk and 32.6 ± 5.57 kg/d milk yield) cows were blocked (n = 12) according to parity, days in milk, and milk yield and were randomly assigned to the following treatments: control (CON), no feed additive; phytogenic feed additive at 5 g/d (PA); and PA + 140 g of buffer compounds (Lithothamnium calcareum, NaHCO3, and MgO) + 25 g/d of a mycotoxin binder (PABB). The PFA mixture contained pepper oleoresin and extracts of cinnamon, pepper, onion, grape seed, Curcuma sp., and Quillaja sp. Treatments were provided mixed into minerals. Cows were allowed a 2 wk-covariate period, and treatments were applied for the following 9 wks. Tukey’s test was used to determine differences between treatment groups. Dry matter (DM) intake was greater (P < 0.001) when feeding phytogenic additives, either PA or PABB, in comparison with CON. Similar nutrient intake was observed between PA and PABB groups. Digestibility of DM was greater (P = 0.047) in cows fed PA than CON but did not differ from those fed PABB. Milk yield was greater (P = 0.041) in cows fed PA than CON group, whereas PA and PABB had similar production values (32.1, 33.6, and 32.8 kg/d for CON, PA, and PABB, respectively). Fat production was increased (P = 0.002) when feeding feed additives. Milk protein concentration was greater (P = 0.043) in PABB-cows than both PA and CON groups. There was no evidence for treatment effects on milk urea nitrogen concentration, feed efficiency, or serum concentrations of glucose and urea-N. The heart rate was lower (P = 0.026) in CON group than PA or PABB during the morning period evaluation. Skin temperature of the face region was elevated (P = 0.040) in cows fed PABB than CON during the morning period. Milk N secretion tended to be greater (P = 0.096) in cows fed treatments with phytogenic additives (PA and PABB) than CON. Relative N excretion (g/kg of N intake) in urine, feces, and milk were not affected by treatments. Urinary purine derivatives daily excretion was similar among treatments. Phytogenic feed additives improve performance of cows, whereas providing a blend of buffer components and mycotoxin binder may increase milk protein concentration.

Determining the Effects of Pelleted Cranberry Vine Grains on the Ewe and Offspring during Pregnancy and Lactation.

When creating any new anti-parasitic interventions, it is important to evaluate their effects across all life stages. This study had three objectives, which were to evaluate the effect of feeding cranberry vine pellet (CVP) on (1) ewes' body weights and BCS during late gestation and lactation; (2) ewes' milk quality during lactation; and (3) lambs' body weight and growth parameters from birth to 65 days of age. Across two years, 41 Dorset ewes were fed either a 50% CVP or a matching control pellet (CON) from 104 ± 1.60 days of gestation for 62.8 ± 0.68 days of lactation. Measurements were collected from ewes (BW, BCS, and milk) and lambs (BW and body size). Milk from CVP ewes exhibited reduced milk fat and solids (p < 0.01) and increased concentrations of milk urea nitrogen (p = 0.02) when evaluated for the treatment-time. There was no significant difference in the BCS, protein, lamb BW, or growth measurements for treatment-time (p ≥ 0.05). Additional research that targets blood biochemistry and metabolic assessments is needed to fully determine the impact of this pellet on ewes and lambs.

Variation of milk urea nitrogen according to milk yield and milk protein in Holstein cows in Boyacá, Colombia

The aim of this study was to determine the variation of milk urea nitrogen (MUN) concentration according to milk yield and milk protein in Holstein cows in Boyacá, Colombia. Data previously collected (n=4901) over two years were used. Univariate analysis of variance was performed with the variables milk yield (l/day) and milk protein (%) as independent variables and the concentration of MUN as the dependent variable. In addition, a simple linear correlation analysis was performed between each variable. The results showed that MUN values are higher when milk yield is lower, but no statistical differences were found for MUN concentration according to milk protein content. Weak and negative correlation was found between milk yield and MUN concentration, but no significant correlation was found between milk protein and MUN concentration.

A cinnamaldehyde feed additive improved feed use-efficiency in lactating dairy cows

Dietary supplementation of essential oils (EO) may increase milk yield and feed use-efficiency in Holstein cattle. A study was conducted to determine the effect of EO feed additives in dairy cattle productivity. The hypothesis was that compared with cinnamaldehyde feed additive supplementation, the supplementation with an additive containing a blend of cinnamaldehyde and garlic oil would improve feed use-efficiency in lactating dairy cattle. Forty-eight lactating Holstein cows (34 multiparous, days in milk (DIM) 118 ± 31.1, and 14 primiparous, DIM 134 ± 38.8) were enroled and randomly assigned to one of three treatments for 8 weeks: 1) control diet (CTRL; no EO supplementation; n = 16), 2) supplementation with cinnamaldehyde (CIN; 600 mg of a prototype to provide 125 mg of cinnamaldehyde; Novus International Inc., St. Charles, MO; n = 16), or 3) supplementation with essential oil blend (EOB; Next Enhance® CGO feed additive, Novus International Inc., St. Charles, MO; to provide 125 mg of cinnamaldehyde and 10 mg of garlic oil; n = 16). Cows were housed in a free-stall barn and the diet was offered as total mixed ration (TMR) formulated with 36% forage and 64% concentrate. The TMR was fed individually and EO additives were top-dressed. Production data were collected and analyzed using the Mixed procedure of SAS (version 9.4) where the fixed effects of treatment, time (i.e., week or day, as repeated measurements), and all possible interactions were included in the model. Compared with CTRL, CIN and EOB decreased (P < 0.05) dry matter intake (DMI, 30.1, 28.2, and 29.6 kg/day respectively). Yields of milk, fat, protein and lactose, and percentage of fat, protein and lactose were not affected by treatments. Compared with CTRL, CIN and EOB decreased (P < 0.05) milk urea nitrogen (MUN) concentrations (11.8, 10.9 and 11.4 mg/dL, respectively). Compared with CTRL, EOB reduced (P < 0.05) somatic cell count (126 and 84 × 103 cells/mL, respectively). Body weight, body condition score, and plasma free fatty acid concentrations were not affected by treatments. Compared with CTRL and EOB, CIN increased (P < 0.05) energy-corrected milk yield (ECM) to DMI ratio (1.63, 1.64 and 1.68, respectively). Moreover, there was a tendency (P < 0.10) for EOB and CIN treatments to increase milk yield to DMI ratio. Compared with CTRL, CIN elicited an increase (P < 0.05) in the conversion efficiency of dietary nitrogen into milk protein (28.1 and 28.7%, respectively). In our study, CIN supplementation increased nitrogen use-efficiency to sustain synthesis of ECM. Therefore, dietary supplementation of cinnamaldehyde may be used to improve nitrogen metabolism and increase feed use-efficiency in lactating dairy cows.

Short-term physiological responses to moderate heat stress in grazing dairy cows in temperate climate.

Even in temperate climate regions, an increase in ambient temperature and exposure to solar radiation can cause heat stress in lactating dairy cows. We hypothesised that grazing dairy cows exhibit short-term physiological changes due to increasing heat load under moderate climate conditions. Over two consecutive summers, 38 lactating Holstein dairy cows were studied in a full-time grazing system. Data were collected in 10 experimental periods of up to three consecutive days with a moderate comprehensive climate index (CCI). The individual animals' vaginal temperature (VT), heart rate, and locomotor activity data were automatically monitored with sensors. Blood samples and proportional whole milk samples were collected at afternoon milking. The concentrations of beta-hydroxybutyrate, glucose, non-esterified fatty acids, urea nitrogen, plasma thyroxine and triiodothyronine were analysed in blood plasma, and fat, protein, lactose, urea nitrogen, cortisol, Na+, K+, and Cl- concentrations were analysed in milk. The daily distribution of VT recordings greater than 39°C showed a circadian rhythm with a proportion of recordings of 2% and lower during the night and a percentage of 10% or higher in the afternoon. The cows' maximal daily vaginal temperature (VTMAX) between 0830 and 1430h was positively related to the mean daily CCI in the same time period (CCIMEAN; mean and SD 23.6±5.4°C). Cows with greater VTMAX had an increased mean heart rate, plasma glucose and milk cortisol concentrations and decreased concentrations of plasma thyroxine and triiodothyronine. The concentration of Na+ in milk was lower, and the concentration of K+ in milk tended to be higher in cows with increased VTMAX. For beta-hydroxybutyrate, non-esterified fatty acids and urea nitrogen concentrations in plasma and fat and lactose concentrations in milk no relationships were found in terms of increasing VT. For milk urea nitrogen and protein concentrations, the proportion of total variance explained by inter-individual or -period variance was high. In conclusion, changes observed in milk and blood likely reflected short-term physiological responses to moderate heat stress. In particular, milk cortisol and Na+ may be useful traits for timely monitoring of heat stress in individual cows because their inter-individual variances were relatively small and samples can be collected non-invasively.

Effects of essential oils supplementation, associated or not with amylase, on dry matter intake, productive performance, and nitrogen metabolism of dairy cows

The aim was to evaluate the effects of essential oils supplementation, associated or not with amylase, on productive performance, milk fatty acid composition, purine derivatives, ruminal microbial synthesis, and feeding behavior of lactating dairy cows. Thirty-three Holstein dairy cows were blocked by days in milk (78.0 ± 9.51) and allocated according to the milk yield into the treatments: i) no feed additives (CTRL); ii) essential oils (EO), the addition of a blend of essential oils [100 mg/kg dry matter (DM) basis]; and iii) essential oils + amylase (EOam), a combination of essential oils and α-amylase (625 mg/kg DM; provided to achieve 375 KNU/kg of DM). Diets were formulated to requirements supply of 32.0 kg/d and 20.0 kg/d of milk yield and dry matter intake (DMI), respectively, and contained 298 g/kg NDF; 172 g/kg CP, and 282 g/kg starch; DM basis. Cows were adapted to the experimental diets for 14 days and the measurements lasted 56 days. Cows were milked twice daily, and milk samples were collected three times per week in two sequential milkings, to determine fat, protein, lactose, and urea nitrogen contents. The statistical model considered the fixed effects of diet, the week of the measurement period and its interaction, and the random effect of the block. The feed additive supplementation did not affect the DMI (23.9 kg/d). The EOam treatment increased feed efficiency (1.40) compared with CTRL and EO, but there were no differences between CTRL (1.27) and EO (1.21). The inclusion of feed additives did not increase the plasma glucose concentration. EOam increased the milk yield compared to the CTRL (32.2 vs. 28.7 kg/d, respectively). Although, energy-corrected milk (ECM) was not influenced by feed additives. There were no differences for fat (37.4 g/kg), lactose (45.6 g/kg), and milk urea nitrogen contents (17.3 mg/dL). However, cows fed EO had higher milk protein concentration than EOam-fed cows. The use of essential oils associated with amylase increases the milk yield, but not energy-corrected milk yield; it improves the feed efficiency in Holstein dairy cows in mid-lactation, and shifts some ruminal patterns that slightly change the milk fatty acid profile and feeding behavior.

Effect of Temperature and Humidity on Milk Urea Nitrogen Concentration.

This study investigated the effect of ambient temperature and humidity on milk urea nitrogen (MUN) concentration in Holstein cows. Meteorological data corresponding to the dates of milk sampling were collected over six years. A linear mixed-effects model including a random effect term for cow identification was used to assess whether temperature and humidity were predictive of MUN concentration. Age, days in milk, temperature humidity index (THI), ration, milk yield, parity and somatic cell count were also evaluated as main effects in the model. A general linear model including all variables as random effects was then fitted to assess the contribution of each variable towards the variability in MUN concentration. Maximum daily temperature and humidity on the sampling day were positively associated with MUN concentration, but their interaction term was negatively associated, indicating that their effects were not independent and additive. Variables that contributed the most to the variability of MUN concentration were dietary crude protein (21%), temperature (18%) and other factors (24%) that were not assessed in the model (error term). Temperature has a significant influence on urea nitrogen concentration and should therefore always be considered when urea nitrogen concentration data are used to make inferences about the dietary management of dairy cows.

Dietary replacement of soybean meal with heat-treated soybean meal or high-protein corn distillers grains on nutrient digestibility and milk composition in mid-lactation cows.

Lactation diets dependent on rumen undegradable protein (RUP) sources derived from soybean meal (SBM) products are generally high in Lys and poor in Met. We conducted an experiment to evaluate the effects of increasing dietary RUP and altering digestible AA supply by inclusion of heat-treated soybean meal (HTSBM) or high-protein corn dried distillers grains with soluble (DDGS) on performance in mid-lactation dairy cows. Twenty-four Holstein cows (200 ± 40 d in milk and 30.0 ± 3.92 kg/d of milk yield) blocked according to parity, milk yield, and days in milk were used in a 3 × 3 Latin square design experiment with 21-d periods. Treatments were (1) control (CON), a diet with 6.0% RUP containing 15.9% SBM as the main protein source; (2) HTSBM, a diet with 6.7% RUP containing 4.4% HTSBM partially replacing SBM; and (3) high-protein DDGS (FP; FlexyPro, SJC Bioenergia), a diet with 6.9% RUP containing 5.34% FP partially replacing SBM and ground corn. Diets had similar crude protein (16.9%) and net energy of lactation. Data were submitted to ANOVA using the mixed procedure of SAS software (SAS Institute Inc.). Treatment differences were evaluated using orthogonal contrasts: (1) increasing RUP (SBM vs. HTSBM + FP) and (2) altering digestible AA supply (HTSBM vs. FP). Cows fed HTSBM and FP had greater intake (values in parentheses represent treatment means of CON, HTSBM, and FP, respectively) of neutral detergent fiber (7.14, 7.35, and 7.69 kg/d), crude protein (4.27, 4.37, and 4.51 kg/d), and ether extract (0.942, 0.968, and 1.04 kg/d) compared with cows fed CON. Feeding FP resulted in greater intake of neutral detergent fiber and ether extract compared with HTSBM. Cows fed HTSBM and FP had lower sorting index for feed particles <4 mm than cows fed CON (1.029, 1.008, and 1.022). Feeding FP resulted in greater intake of feed particles <4 mm compared with HTSBM. Treatments containing HTSBM or FP tended to decrease organic matter digestibility (72.4, 71.2, and 71.1%), but no other effects were detected in digestibility of neutral detergent fiber, crude protein, or ether extract. No evidence for differences among treatments was detected in excretion of purine derivatives in milk and urine. Milk yield was greater in cows fed HTSBM or FP than in cows fed CON (28.0, 28.9, and 28.8 kg/d, respectively). Cows fed HTSBM or FP tended to have greater energy-corrected milk and protein yield compared with those fed CON. Milk protein concentration was greater in DDGS cows than those in the HTSBM group (3.45 and 3.40%, respectively). No differences were detected in milk fat yield and concentration, milk urea nitrogen, feed efficiency, or serum concentrations of urea and glucose. Overall, increasing dietary RUP by feeding HTSBM or FP improved intake of nutrients and milk yield without affecting feed efficiency. Altering digestible AA supply while maintaining similar dietary RUP had negligible effects on performance of cows.