Milk Urea Research Articles

Cow-level factors associated with nitrogen utilization in grazing dairy cows using a cross-sectional analysis of a large database

Reducing nitrogen pollution while maintaining milk production is a major challenge of dairy production. One of the keys to delivering on this challenge is to improve the efficiency of how dairy cows use nitrogen. Thus, estimating the nitrogen utilization of lactating grazing dairy cows and exploring the association between animal factors and productivity with nitrogen utilization are the first steps to understanding the nitrogen utilization complex in dairy cows. Nitrogen utilization metrics were derived from milk and body weight records from 1,291 grazing dairy cows of multiple breeds and crossbreeds; all cows had sporadic information on nitrogen intake concurrent with information on nitrogen sinks (and other nitrogen sources, such as body tissue mobilization). Several nitrogen utilization metrics were investigated, including nitrogen use efficiency (nitrogen output as products such as milk and meat divided by nitrogen intake) and nitrogen excreted (nitrogen intake less the nitrogen output as products such as milk and meat). In the present study, a primiparous Holstein-Friesian used, on average, 20.6% of the nitrogen it ate, excreting the surplus as feces and urine, representing 402 g of nitrogen per day. Intercow variability existed, with a between-cow standard deviation of 0.0094 for nitrogen use efficiency and 24 g of nitrogen per day for nitrogen excretion. As lactation progressed, nitrogen use efficiency declined and nitrogen excretion increased. Nevertheless, nitrogen use efficiency improved (i.e., decreased) from first to second parity, even though it did not improve from second to third parity or greater. Furthermore, nitrogen excretion continued to increase from first to third parity or greater. Nitrogen use efficiency and nitrogen excretion were negatively correlated (-0.56 to -0.40), signifying that dairy cows who partition more of the ingested nitrogen into products such as milk and meat, on average, also excrete less nitrogen. Milk urea nitrogen was, at best, weakly correlated with nitrogen use efficiency and nitrogen excretion; the correlations were between -0.01 and 0.06. In conclusion, several cow-level factors such as parity, stage of lactation, and breed were associated with the range of different nitrogen efficiency metrics investigated; moreover, even after accounting for such effects, 4.8% to 6.3% of the remaining variation in the nitrogen use efficiency and nitrogen balance metrics were attributable to intercow differences.

Effects of cashew nut shell extract supplementation on production, rumen fermentation, metabolism, and inflammatory biomarkers in transition dairy cows

Cashew nut shell extract (CNSE) is a byproduct of the cashew nut industry, containing bioactive compounds that alter rumen fermentation patterns. Therefore, study objectives were to evaluate the effects of CNSE (59% anacardic acid and 18% cardol) on production, rumen fermentation variables, metabolism, and inflammation in transition dairy cows. A total of 51 multiparous Holstein cows were used in a randomized design and assigned to treatment based on their previous 305-d mature equivalent milk and parity. Cows were assigned to 1 of 2 treatments 21 d before expected calving: (1) CON (control diet; n = 17) or (2) CNSE-5.0 (control diet and 5.0 g/d CNSE granule [containing 50% CNSE]; n = 34). Following parturition, 17 cows (preselected at initial treatment assignment) from the CNSE-5.0 treatment were reallocated into a third treatment group: CNSE-2.5 (control diet and 2.5 g/d CNSE granule; n = 17), resulting in 3 total treatments postpartum: (1) CON, (2) CNSE-2.5, and (3) CNSE-5.0. Prepartum rumen pH was unaltered by treatment; however, postpartum rumen pH was increased (0.31 units) in CNSE cows relative to CON. Prepartum rumen ammonia N concentration tended to be decreased (34%) in CNSE-5.0 cows compared with CON, and there tended to be a quadratic effect on postpartum ammonia N, as it was decreased in CNSE-2.5 compared with CON and CNSE-5.0. Prepartum dry matter intake (DMI) was unaffected by treatment; however, postpartum DMI was increased (8%) in CNSE cows relative to CON. No treatment differences were observed in pre- or postpartum digestibility measurements. Milk and protein yields from cows fed CNSE tended to be increased (6% and 7%, respectively) relative to CON. No treatment differences were detected for energy-corrected milk, feed efficiency, body weight, body condition score, energy balance, milk composition, milk urea nitrogen, or somatic cell count. Prepartum fecal pH decreased (0.12 units) in CNSE-5.0 cows relative to CON cows but was similar between treatments postpartum. Supplementing CNSE did not affect prepartum glucose, nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), or insulin. However, prepartum circulating blood urea nitrogen tended to be decreased and glucagon was decreased in CNSE-5.0 cows compared with CON (9 and 20%, respectively). Additionally, CNSE supplementation decreased glucose and insulin concentrations postpartum relative to CON cows (6% and 20%, respectively). Quadratic effects were detected for postpartum circulating NEFA and BHB such that their levels were increased in CNSE-2.5 cows relative to CON and CNSE-5.0. Pre- and postpartum circulating serum amyloid A, lipopolysaccharide-binding protein, and haptoglobin were unaffected by treatment. Overall, CNSE influenced some key rumen fermentation variables, altered postabsorptive metabolism, and increased production parameters in transition dairy cows.

Effects of proportion and digestibility of grass-clover silage on milk protein, mineral and fatty acid compositions in Danish Holstein cows

ABSTRACT The objective of this study was to investigate the effects of proportion and organic matter digestibility (OMD) of grass-clover silage on milk composition. Grass-clover silages with low (LD) or high (HD) OMD were mixed at low (30:70, LP) or high (70:30, HP) proportion (DM basis) with maize silage to arrange 4 total mixed rations (TMR) with a forage-to-concentrate ratio of 60:40. The TMR were fed ad libitum to 36 cows in a 4 × 4 Complete Latin Square design. The proportion × OMD interaction showed that feeding a high proportion of low-digestible grass-clover silage resulted in a higher content of milk urea nitrogen (P < .001). The diets had a minor impact on milk protein and mineral compositions. Decreasing the grass-clover to maize silage ratio from 70:30 to 30:70 improved the nutritional value of milk fat by decreasing the share of saturated and increased the share of unsaturated fatty acids (P < .001).

Rumen-protected lysine supplementation improved amino acid balance, nitrogen utilization and altered hindgut microbiota of dairy cows

This study was conducted to evaluate the effects of dietary crude protein (CP) and rumen-protected lysine (RPL) supplementation on lactation performance, amino acid (AA) balance, nitrogen (N) utilization and hindgut microbiota in dairy cows. Treatments were in a 2 × 2 factorial arrangement, and the main effects were CP concentration (16% vs. 18%) and RPL supplementation (with or without RPL at 40 g/cow per day). Forty cows were randomly allocated to 4 groups: low-CP diet (LP), low-CP diet plus RPL (LPL), high-CP diet (HP), high-CP diet plus RPL (HPL). The experiment was conducted for 8 weeks. Results showed that RPL increased the dry matter intake (P < 0.01), milk protein yield (P = 0.04) and energy corrected milk (P = 0.04), and tended to increase milk fat yield (P = 0.06) and fat corrected milk (P = 0.05). Cows in the HP group tended to have higher milk urea N (P = 0.07). Plasma concentrations of Arg, Ile, Lys, Met, Pro, total essential AA and total nonessential AA were increased by RPL (P < 0.05). The total essential AA, total nonessential AA and most AA (except Ile, Phe, Gly and Pro) were increased in the HP group (P < 0.05). N excretion was increased in the HP group through an increase in urea N excretion (P < 0.01) and an upward trend in plasma urea N (P = 0.07). In addition, RPL tended to increase milk protein N secretion (P = 0.08), milk N (P = 0.07) and microbial protein synthesis (P = 0.06), and decreased plasma urea N (P < 0.001). In the hindgut, the bacterial community were different between the LP and LPL groups (P < 0.01). The probiotic abundances of Christensenellaceae_R-7_group and Acinetobacter were increased by RPL (P = 0.03 and 0.03, respectively). The pathogenic abundances of Clostridium_sensu_stricto_1 (P < 0.001) and Turicibacter (P < 0.01) were decreased by RPL. In conclusion, supplementing RPL with low dietary CP could balance AA supply and increase milk protein yield, resulting in an improvement in N utilization efficiency, and altered the composition of the hindgut microbiota to favor the lactation performance of dairy cows.

Validating genomic prediction for nitrogen efficiency index and its composition traits of Holstein cows in early lactation.

Nitrogen (N) use efficiency (NUE) is an economically important trait for dairy cows. Recently, we proposed a new N efficiency index (NEI), that simultaneously considers both NUE and N pollution. This study aimed to validate the genomic prediction for NEI and its composition traits and investigate the relationship between SNP effects estimated directly from NEI and indirectly from its composition traits. The NEI composition included genomic estimated breeding value of N intake (NINT), milk true protein N (MTPN) and milk urea N yield. The edited data were 132,899 records on 52,064 cows distributed in 773 herds. The pedigree contained 122,368 animals. Genotypic data of 566,294 SNP was available for 4514 individuals. A total of 4413 cows (including 181 genotyped) and 56 bulls (including 32 genotyped) were selected as the validation populations. The linear regression method was used to validate the genomic prediction of NEI and its composition traits using best linear unbiased prediction (BLUP) and single-step genomic BLUP (ssGBLUP). The mean theoretical accuracies of validation populations obtained from ssGBLUP were higher than those obtained from BLUP for both NEI and its composition traits, ranging from 0.57 (MTPN) to 0.72 (NINT). The highest mean prediction accuracies for NEI and its composition traits were observed for the genotyped cows estimated under ssGBLUP, ranging from 0.48 (MTPN) to 0.66 (NINT). Furthermore, the SNP effects estimated from NEI composition traits, multiplied by the relative weight were the same as those estimated directly from NEI. This study preliminary showed that genomic prediction can be used for NEI, however, we acknowledge the need for further validation of this result in a larger dataset. Moreover, the SNP effects of NEI can be indirectly calculated using the SNP effects estimated from its composition traits. This study provided a basis for adding genomic information to establish NEI as part of future routine genomic evaluation programs.

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.

Application of ATR-FTIR Incorporated with Multivariate Data Analysis for Discrimination and Quantification of Urea as an Adulterant in UHT Milk.

Urea is naturally present in milk, yet urea is added intentionally to increase milk's nitrogen content and shelf life. In this study, a total of 50 Ultra heat treatment (UHT) milk samples were spiked with known urea concentrations (0-5 w/v%). Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy with principal component analysis (PCA), discriminant analysis (DA), and multiple linear regression (MLR) were used for the discrimination and quantification of urea. The PCA was built using 387 variables with higher FL > 0.75 from the first PCA with cumulative variability (90.036%). Subsequently, the DA model was built using the same variables from PCA and demonstrated the good distinction between unadulterated and adulterated milk, with a correct classification rate of 98% for cross-validation. The MLR model used 48 variables with p-value < 0.05 from the DA model and gave R2 values greater than 0.90, with RMSE and MSE below 1 for cross-validation and prediction. The DA and MLR models were then validated externally using a test dataset, which shows 100% correct classification, and the t-test result (p > 0.05) indicated that the MLR could determine the percentage of urea in UHT milk within the permission limit (70 mg/mL). In short, the wavenumbers 1626.63, 1601.98, and 1585.5534 cm-1 are suitable as fingerprint regions for detecting urea in UHT milk.

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.

EVALUACIÓN DE ENSILADO DE ARVENSES EN LA ALIMENTACIÓN DE GANADO LECHERO EN SISTEMAS DE PRODUCCIÓN DE LECHE EN PEQUEÑA ESCALA

&lt;p&gt;&lt;strong&gt;Background:&lt;/strong&gt; The use of weeds in animal feed is a common practice in Mexico. &lt;strong&gt;Objective:&lt;/strong&gt; To evaluate the ensilage of grasses as forage alternatives in the feeding of cows in small-scale milk production systems. &lt;strong&gt;Methodology:&lt;/strong&gt; Two grass silages were evaluated: Slg-40 with 40% mirasol and 30% barley, and Slg-60 with 60% mirasol and 40% grasses and other grasses, with corn silage (Slg-Mz), supplemented with 4.1 kg MS of commercial concentrate. In a 3X3 Latin square repeated twice with 6 cows and 14-day periods. Forage chemical composition and productive response were evaluated. &lt;strong&gt;Results:&lt;/strong&gt; An average content of Neutral Detergent Fibre of 650 g/kg MS, Acid Detergent Fibre of 479 g/kg MS, and Crude Protein of 62 g/kg DM were reported in the grass silages; estimated metabolizable energy levels of 7 and 8 MJ/kg DM were reported for the SLG-40 and Slg-Mz silages, respectively. In the productive response a higher fat content is reported for the Slg-40 treatment, with respect to Slg-60, for milk yield, protein, lactose, milk urea nitrogen, dry matter intake, live weight and body condition no differences were reported (p˃0.05). &lt;strong&gt;Implications:&lt;/strong&gt; This work raises the use of vetch as silage in animal feeding. &lt;strong&gt;Conclusion:&lt;/strong&gt; Silage of weed proved to be a feeding alternative in the face of forage shortage scenarios.&lt;/p&gt;

Assessment of different dietary alfalfa hay to alfalfa silage ratios for dromedary camel feeding

ABSTRACT Two in vivo experiments studied the effects of different alfalfa hay (AH) to alfalfa silage (AS) ratios including 100:0 (AH100), 50:50 (AH50:AS50) and 0:100 (AS100) in total mixed rations (TMR) of dromedary camels. In experiment (Exp.) 1, a total of 18 multiparous Baluchi dairy camel [100 ± 5 days in milk (DIM); 3.65 ± 0.539 kg milk yield] were randomly allocated to one of the three groups (n = 6) for 42 d of experimental period. Dry matter intake (DMI) and milk yield were recorded daily, and blood samples were collected on days 0, 21 and 42. In Exp. 2, 18 male Baluchi camel calves [275 ± 14 days of old; 105 ± 8 kg BW] were housed in individual shaded pens for 150 days. DMI was recorded daily and individual weights of camels were recorded monthly. Blood samples were collected on days 0, 75 and 150. In Exp.1, feeding different dietary AH:AS ratios altered neither DMI (p = 0.351) nor milk yield (p = 0.667). Of all milk components, only the milk urea nitrogen (MUN) was increased (p = 0.015) by AS feeding (both AH50:AS50 and/or AS100). AS feeding tended to increase AST (p = 0.099) and ALT (p = 0.092) levels in lactating camels. In Exp. 2, DMI (p = 0.845), average daily gain (ADG; p = 0.092) and return per kg BW gain (p = 0.710) of silage-fed camels were similar to those of hay-fed group. The plasma concentration of BUN (p = 0.014) and AST (p = 0.014) were increased in camels fed AS100. Overall, the results suggest that both AS and/or AH could be used in dromedary camel diets based on the climatic condition, season and available facilities; however, the long-term use of AS (as sole forage) should done with caution due to the potential risk of impaired liver function. Further studies needed to explore the impact of hay versus silage feeding on digestibility, rumen function and nitrogen pollution in camel feeding.

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.

P31 Protein supplement type affect milk urea nitrogen in lactating dairy cows

P31 Protein supplement type affect milk urea nitrogen in lactating dairy cows

Effects of Two Levels of Dietary Energy Content on Milk Production and Serum Metabolites in Early Lactation Temperate Crossbred Dairy Cows Fed Guinea Grass (&lt;em&gt;Megathyrsus maximus&lt;/em&gt;) Based Diets

The current study investigated the association of two levels of metabolizable energy (ME) content on milk production, composition, and blood metabolites of temperate crossbred (Jersey x Frieician) dairy cows fed with Guinea grass (Panicum maximum) and concentrates (50:50 on a DM basis) based total mixed ration (TMR). Twelve multiparous temperate crossbred dairy cows were randomly allocated to each dietary treatment (n=6) in a randomized block design. The required energy diet (RE) was predicted to supply the recommended level (100%) of ME, and the high energy diet (HE) was predicted to supply 10% more than the recommended level (110%) of the daily ME requirements of the dairy cows. Dry matter intake, body weight, and milk yield were recorded, and feed and blood samples were obtained for proximate and blood metabolite analysis during the 14 weeks experimental period. No treatment effects were observed (P&gt;0.05) on BW, milk fat, SNF, protein, and milk urea nitrogen or on blood metabolites such as serum non esterified fatty acids, beta-hydroxy butyric acid, Albumin, Ca and P. Compared to the cows fed with RE, HE diet fed cows had high (P&lt;0.05) dry matter intake at 4, 10, 12, and 14 weeks but dietary treatment had no effect on dry matter intake (P&gt;0.05) at 2, 6, and 8 weeks of the experimental period. Until the 4th week of lactation, dietary treatment had no effect (P&gt;0.05) on milk yield, but from the 4th to the 14th week, cows fed with HE had a higher (P&lt;0.05) milk yield than those fed with RE. Thus, the cumulative milk yield of the cows fed with HE were higher (P&lt;0.05) than that of cows fed with RE from the 10th to 14th weeks of lactation. It was concluded that the milk yield of temperate crossbred dairy cows fed diets based on Guinea grass can be enhanced by incorporating high energy content into the diet.

Effect of diets with different crude protein levels on ammonia and greenhouse gas emissions from a naturally ventilated dairy housing

Less crude protein (CP) in the diet can reduce nitrogen excretion of dairy cattle and lower their ammonia (NH3) and nitrous oxide (N2O) formation potential. The diet composition might also affect emissions of methane (CH4) and carbon dioxide (CO2). However, previous studies did not investigate the effect of diets with different CP levels that are customary practice in Switzerland on NH3 and greenhouse gas emissions on a practical scale. In a case-control approach, we quantified the emissions (NH3, N2O, CH4, CO2) in two separate but identical compartments of a naturally ventilated cubicle housing for lactating dairy cows over six days by using a tracer ratio method. Cows in one compartment received a diet with 116 g CP per kilogram dry matter (DM), in the other compartment with 166 g CP kg−1 DM. Subsequently, diets were switched for a second 6-day measurement phase. The results showed that the diet, aside from outside temperature and wind speed in the housing, was driving NH3 and N2O emissions. NH3 and N2O emission reduction per livestock unit (LU) was on average 46 % and almost 20 %, respectively, for the diet with low CP level compared to the higher CP level. In addition, strong relationships were observed between the CP content of the diet, N excretion in the urine and the milk urea content. An increased temperature or wind speed led to a clear increase in NH3 emissions. Differences in CH4 and CO2 emissions per LU indicated a significant influence of the diet, which cannot be attributed to the CP content. Our herd-level study demonstrated that a significant reduction in NH3 and N2O emissions related to LU, energy-corrected milk as well as DM intake can be achieved by lowering the CP content in the diet.

Effects of heat stress on markers of skeletal muscle proteolysis in dairy cattle

Heat stress (HS) markedly affects postabsorptive energetics and protein metabolism. Circulating urea nitrogen increases in multiple species during HS and it has been traditionally presumed to stem from increased skeletal muscle proteolysis; however, this has not been empirically established. We hypothesized HS would increase activation of the calpain and proteasome systems as well as increase degradation of autophagosomes in skeletal muscle. To test this hypothesis, lactating dairy cows (~139 d in milk; parity ~2.4) were exposed to thermal neutral (TN) or HS conditions for 7 d (8 cows/environment). To induce HS, cattle were fitted with electric blankets for the duration of the heating period and the semitendinosus was biopsied on d 7. Heat stress increased rectal temperature (1.3°C) and respiratory rate (38 breaths per minute) while it decreased dry matter intake (34%) and milk yield (32%). Plasma urea nitrogen (PUN) peaked following 3 d (46%) and milk urea nitrogen (MUN) peaked following 4 d of environmental treatment and while both decreased thereafter, PUN and MUN remained elevated compared with TN (PUN: 20%; MUN: 27%) on d 7 of HS. Contrary to expectations, calpain I and II abundance and activation and calpain activity were similar between groups. Likewise, relative protein abundance of E3 ligases, muscle atrophy F-box protein/atrogin-1 and muscle ring-finger protein-1, total ubiquitinated proteins, and proteasome activity were similar between environmental treatments. Finally, autophagosome degradation was also unaltered by HS. Counter to our hypothesis, these results suggest skeletal muscle proteolysis is not increased following 7 d of HS and call into question the presumed dogma that elevated skeletal muscle proteolysis, per se, drives increased AA mobilization.

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.

Estimation of heritability for milk urea and genetic correlations with milk production traits in 3 Danish dairy breeds

The aim of this study was to estimate genetic parameters for milk urea (MU) content in 3 main Danish dairy breeds. As a part of the Danish milk recording system, milk samples from cows on commercial farms were analyzed for MU concentration (mmol/L) and the percentages of fat and protein. There were 323,800 Danish Holstein, 70,634 Danish Jersey, and 27,870 Danish Red cows sampled with a total of 1,436,580, 368,251, and 133,922 test-day records per breed, respectively, included in the data set. Heritabilities for MU were low to moderate (0.22, 0.18, and 0.24 for the Holstein, Jersey, and Red breeds, respectively). The genetic correlation was close to zero between MU and milk yield in Jersey and Red, and -0.14 for Holstein. The genetic correlations between MU and fat and protein percentages, respectively, were positive for all 3 dairy breeds. Herd-test-day explained 51%, 54%, and 49% of the variation in MU in Holstein, Jersey, and Red, respectively. This indicates that MU levels in milk can be reduced by farm management. The current study shows that there are possibilities to influence MU by genetic selection as well as by farm management.

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.

Effects of forage and grain legume-based silages supplemented with faba bean meal or rapeseed expeller on lactational performance, nitrogen utilization, and plasma amino acids in dairy cows

The objective of this experiment was to investigate the effect of forage type [red clover (51%)-grass silage, i.e., RCG; vs. faba bean (66%)-grass silage, i.e., FBG] and concentrate type (faba bean, FB; vs. rapeseed expeller, RE) on lactational performance, milk composition and nitrogen (N) utilization in lactating dairy cows. Eight lactating multiparous Nordic Red cows were used in a replicated 4 × 4 Latin Square experiment, with 21-d periods, in a 2 × 2 factorial arrangement of treatments. The experimental treatments were as follows: (1) RCG with RE, (2) RCG with FB, (3) FBG with RE, and (4) FBG with FB. Inclusion rates of RE and FB were isonitrogenous. Crude protein contents of the experimental diets were 16.3, 15.9, 18.1, and 17.9% of dry matter, respectively. All diets included oats and barley and were fed ad libitum as total mixed rations with forage-to-concentrate ratio of 55:45. Dry matter intake and milk yield were recorded daily, and spot samples of urine, feces, and blood were collected at the end of each experimental period. Dry matter intake did not differ across diets, averaging 26.7 kg/d. Milk yield averaged 35.6 kg/d and was 1.1 kg/d greater for RCG versus FBG, and milk urea N concentration was lower for RCG compared with FBG. Milk yield was 2.2 kg/d and milk protein yield 66 g/d lower for FB versus RE. Nitrogen intake, urinary N, and urinary urea N excretions were lower, and milk N excretion tended to be lower for RCG compared with FBG. The proportion of the dietary N excreted as fecal N was larger in cows fed RCG than for those fed FBG, and the opposite was true for urinary N. We detected an interaction for milk N as percentage of N intake: it increased with RE compared with FB for RCG-based diet, but only a marginal increase was observed for FBG-based diet. Plasma concentration of His and Lys were lower for RCG than for FBG, whereas His tended to be greater and Lys lower for FB compared with RE. Further, plasma Met concentration was around 26% lower for FB than for RE. Of milk fatty acids, saturated fatty acids were decreased by RCG and increased by FB compared with FBG and RE, respectively, whereas monounsaturated fatty acids were increased by RCG versus FBG, and were lower for FB than for RE. In particular, 18:1n-9 concentration was lower for FB compared with RE. Polyunsaturated fatty acids, such as 18:2n-6 and 18:3n-3, were greater for RCG than for FBG, and 18:2n-6 was greater and 18:3n-3 was lower for FB versus RE. In addition, cis-9,trans-11 conjugated linoleic acid was lower for FB compared with RE. Faba bean whole-crop silage and faba bean meal have potential to be used as a part of dairy cow rations, but further research is needed to improve their N efficiency. Red clover-grass silage from a mixed sward, without inorganic N fertilizer input, combined with RE, resulted in the greatest N efficiency in the conditions of this experiment.

Evaluation of 3 northwest European seaweed species on enteric methane production and lactational performance of Holstein-Friesian dairy cows

Seaweeds have been studied for their ability to reduce enteric methane emissions of ruminants when fed as a feed supplement. In vivo research with dairy cattle is mainly limited to the seaweed species Ascophyllum nodosum and Asparagopsis taxiformis, whereas in vitro gas production research covers a broader range of brown, red, and green seaweed species from different regions. The objective of the present study was to determine the effect of Chondrus crispus (Rhodophyta), Saccharina latissima (Phaeophyta), and Fucus serratus (Phaeophyta), 3 common northwest European seaweeds, on enteric methane production and lactational performance of dairy cattle. Sixty-four Holstein-Friesian dairy cattle (16 primiparous, 48 multiparous) averaging (mean ± standard deviation) 91 ± 22.6 d in milk and 35.4 ± 8.13 kg/d fat- and protein-corrected milk yield (FPCM) were randomly assigned to 1 of 4 treatments in a randomized complete block design. Cows were fed a partial mixed ration [54.2% grass silage, 20.8% corn silage, and 25.0% concentrate; dry matter (DM) basis] with additional concentrate bait in the milking parlor and the GreenFeed system (C-Lock Inc.). The 4 treatments consisted of a control diet without seaweed supplement (CON), or CON supplemented with 150 g/d (fresh weight of dried seaweed) of either C. crispus (CC), S. latissima (SL), or a 50/50 mix (DM basis) of F. serratus and S. latissima. Milk yield (28.7 vs. 27.5 kg/d, respectively), fat- and protein-corrected milk (FPCM) yield (31.4 vs. 30.2 kg/d, respectively), milk lactose content (4.57 vs. 4.52%, respectively), and lactose yield (1,308 vs. 1,246 g/d, respectively) increased for SL compared with CON. Milk protein content was lower for SL compared with the other treatments. Milk fat and protein contents; yields of fat, protein, lactose, and FPCM; feed efficiency; milk nitrogen efficiency; and somatic cell count did not differ between CON and the other treatments. Depending on week of experiment, milk urea content was higher for SL compared with CON and CC. No effects were observed of the treatments compared with CON for DM intake, number of visits to the GreenFeed, or gas emission (production, yield, or intensity) of CO2, CH4, and H2. In conclusion, the seaweeds evaluated did not decrease enteric CH4 emissions and did not negatively affect feed intake and lactational performance of dairy cattle. Milk yield, FPCM yield, milk lactose content, and lactose yield increased, and milk protein content decreased, with S. latissima.