Milk Energy Output Research Articles

The Effect of Rumen-Protected Conjugated Linoleic Acid on Milk Composition and Milk Energy Output of Holstein Cows and Its Potential Mechanism.

Conjugated linoleic acid (CLA) can regulate fatty acid metabolism and increase the content of unsaturated fatty acids in milk during the nutritional regulation process in dairy cows. However, its effects on milk composition and milk energy output in dairy cows remain unclear. We aimed to investigate whether RP-CLA reduces milk energy output during early lactation while lowering milk fat, as well as whether it affects milk protein synthesis and the potential mechanisms. We examined the milk composition of Holstein fresh cows at different stages by administering RP-CLA for 7 days and analyzing related gene expression in the MAC-T cell line. RP-CLA did not significantly alter milk yield, lactose, or blood ketone levels in early lactation. Starting RP-CLA from day 21 postpartum reduced milk fat by about 26% (3.74% vs 2.78%) on day 28 postpartum, slightly increased milk protein, and improved blood glucose on day 24. No such effects were seen with RP-CLA beginning on day 7 postpartum. RP-CLA supplementation saved 6.45 and 11.43% milk energy output during days 7-14 and 21-28, respectively. We hypothesize that the limited RP-CLA regulation effect during days 7-21 may relate to intense lipid mobilization under negative energy balance. In MAC-T cells under low glucose, t-10, c-12 CLA decreased the expression of SREBP1 and AMPK, while increased CDK1, indicating its role in reducing fat synthesis, easing energy deficiency, promoting cell proliferation, and enhancing protein synthesis. Similarly, under normal glucose, t-10, c-12 CLA suppressed SREBP1 and elevated CDK1 expression, with AMPK reduction only at low doses. Inhibiting milk fat synthesis with an SREBP1 inhibitor slightly upregulated CDK 1 without significantly affecting AMPK. In conclusion, RP-CLA has the potential to alleviate negative energy balance in dairy cows during days 21-35 postpartum. t10, c12 CLA can inhibit milk fat synthesis by reducing the expression of SREBP1 and AMPK in mammary epithelial cells, while increasing the expression of CDK1, thereby improving the cellular energy status and promoting milk protein synthesis. The energy required for the increase in milk protein is not derived from the energy saved by the inhibition of milk fat synthesis by CLA.

A New Strain of Saccharomyces cerevisiae in Diets of Lactating Holstein Cows Improved Feed Efficiency and Lactation Performance

Abstract This study compared the effects of feeding a new strain of Saccharomyces cerevisiae HSA2020 with a commercial strain on in vitro rumen fermentation and production performance of dairy cows. Permeate was used as a substrate for the laboratory production of the new strain of S. cerevisiae after the hydrolysis by β-galactosidase (5000 µ/mL at 37°C). Two experiments were conducted: in Experiment 1, the effects of three levels (1, 2 and 3 g/kg dry matter) of S. cerevisiae on in vitro ruminal fermentation kinetics were evaluated. In Experiment 2, for 60 days, sixty multiparous Holstein cows (639±24.8 kg BW, 3±1 parity, 7±1 days in milk, with a previous milk production of 23±2.0 kg/d) during the previous lactation, were randomly assigned to 3 treatments in a completely randomized design. Cows were fed without any additives (control treatment) or supplemented with 2 g/kg feed daily of laboratory produced (PY) or commercial (CY) S. cerevisiae. In Experiment 1, inclusion of PY and CY increased (P<0.05) gas production, propionate, and nutrient disappearance, while decreased (P<0.05) methane production and protozoal count. Moreover, in Experiment 2, PY followed by CY increased (P<0.01) nutrient digestibility, and serum concentrations of total protein, albumin, and glucose (P<0.05). Higher daily milk yield, and milk energy output were observed with PY and CY without affecting concentrations of milk components or milk fatty acid profile. Compared to control, increased feed efficiency was observed with PY and CY. Compared to PY, CY increased serum concentrations of urea-N and decreased triglycerides, while PY decreased serum aspartate transaminase and increased concentration of conjugated linoleic acids in milk. In early lactating cow diets, both strains of S. cerevisiae improved production performance at 2 g/kg, and minimal differences between strains were found.

Dietary macronutrient composition and partial soybean meal replacement with slow-release urea: Effects on performance, digestibility, rumen fermentation, and nitrogen metabolism in dairy cows

A 2 × 2 factorial arrangement of treatments was used to investigate the interactive effects of dietary macronutrient composition [high-starch, low-fat, low-fiber (HsLFF) than low-starch, high-fat, high-fiber (LsHFF)] and N source [soybean meal (SBM) or partially replaced by slow-release urea (SRU)] on lactation performance, rumen fermentation, N utilization efficiency, nutrient digestibility, blood metabolites, and feeding behavior in cows. A replicated 4 × 4 Latin square design was used involving 12 multiparous Holstein cows (milk yield of 40.5 ± 5.6 kg/d, BW of 590 ± 20 kg; 81 ± 12 d in milk). The HsLFF diet contained 300 g/kg starch, 31.3 g/kg fat, and 301 g/kg NDF, without straw or additional fat. In contrast, the LsHFF diet contained 195.5 g/kg starch, 60.8 g/kg fat, and 367.5 g/kg NDF, enriched with wheat straw (100 g/kg), and additional fat (34 g/kg). The diets were formulated to be iso-nitrogenous and isocaloric. Cows fed the HsLFF diet had greater DM intake, digestibility of DM and CP, milk yield and milk protein %, but lower intakes of NDF, and physically effective NDF, and milk fat % than cows fed the LsHFF diet. Replacing SBM with SRU significantly increased milk solids yield without affecting other lactation performance or BW. Cows fed the LsHFF diet had higher ruminal pH and branched-chain VFA proportions but lower total VFA concentrations compared with the HsLFF diet, while those on the LsHFF-SRU diet had the highest ruminal ammonia levels. Compared with the HsLFF diet, cows fed LsHFF had lower NE intake, milk energy output and energy requirement for maintenance, although energy balances were similar among groups. The HsLFF diet improved N utilization, resulting in higher N content in milk and lower N excretion in feces. Blood metabolite studies showed significant interactions between the main factors, particularly for blood glucose and creatinine, with the lowest levels in cows fed the LsHFF-SRU and LsHFF-SBM diets. In addition, alanine aminotransferase levels were higher in cows fed the LsHFF diet than in cows fed the HsLFF diet. This could indicate early-stage liver stress due to the metabolic imbalance caused by a high-fat, low-starch diet, which can alter energy metabolism. Cows on the HsLFF-SRU diet had the highest glucose levels, indicating possible changes in carbohydrate metabolism or a higher metabolic rate. The concentration of BUN increased steadily after feeding in the LsHFF diet and peaked after 4 h in the LsHFF-SRU diet, with no difference between N sources in the HsLFF diet. Partial replacement of SRU with SBM had no effect on BUN. The interaction between the main factors had a significant effect on MUN content, which was highest in LsHFF-SRU and lowest in HsLFF-SRU, with no difference between the N sources in the HsLFF diets. Overall, while diets with reduced starch and increased fiber and fat compromised lactation performance, partially substituting SRU with SBM helped maintain milk production and milk nitrogen efficiency. However, the LsHFF-SRU diet was less efficient in N utilization, as shown by higher levels of ruminal ammonia, BUN and MUN.

Effects of the palmitic-to-oleic ratio in the form of calcium salts of fatty acids on the production and digestibility in high-yielding dairy cows

The form of fat supplements, degree of saturation, and the fatty acid (FA) profile influence cows' production response. The objective was to determine the effects of supplemental fats in the form of calcium salts (CS) of FA (CSFA) with different ratios between palmitic (PA) and oleic (OA) acids on nutrient digestibility and cow performance. Forty-two dairy cows were assigned to 3 groups and fed (for 13 wk) rations that contained 2.2% CSFA (on a DM basis) with increasing PA-to-OA ratios as follows: (1) CS45:35, 45% PA and 35% OA; (2) CS60:30, 60% PA and 30% OA; and (3) CS70:20, 70% PA and 20% OA. Rumen and fecal samples were taken for VFA and digestibility measurements, respectively. Increasing the PA-to-OA ratio linearly decreased the milk and ECM yields, whereas a quadratic effect was observed for milk fat concentration (3.55%, 3.94%, and 3.87% in the CS45:35, CS60:30, and CS70:20 groups, respectively) and fat yield. Dry matter intake was highest in the CS60:30 group (33.7 kg/d) and lowest in the CS70:20 group (31.6 kg/d), and a tendency of quadratic effect was observed for calculated energy balance with no difference in BW gain among the groups. The milk-to-DMI ratio was decreased, and the ratio of ECM-to-DMI tended to decrease when the PA-to-OA ratio increased. The highest apparent total-tract digestibilities of DM, OM, and protein were observed in the CS60:30 cows, and NDF tended to decrease with increasing PA-to-OA ratio; however, digestibility of the total FA and FA subgroups (16- and 18-carbon FA) were not different among groups. Across treatments, the 18-carbon FA digestibility was higher than the 16-carbon FA digestibility. Under the current study conditions, the CS60:30 cows had the highest fat concentration and fat yield; energy output in milk; DMI; and digestibility of DM, OM, and protein. However, further research is required to fine tune the optimal FA ratio in supplemental fat sources to maximize production and efficiency under various conditions, such as production level, stage of lactation, and diet composition.

Effects of the level and source of dietary physically effective fiber on feed intake, nutrient utilization, heat energy, ruminal fermentation, and milk production by Alpine goats

Thirty-two primiparous and 31 multiparous Alpine goats were used to determine influences of diets varying in level and source of forage on performance in early to mid-lactation for 16 wk. Diets consisted of 40%, 50%, 60%, and 70% forage (designated as 40F, 50F, 60F, and 70F, respectively) with 60F and 70F containing coarsely ground grass hay (primarily orchardgrass) and 40F and 50F containing cottonseed hulls, alfalfa pellets, and coarsely ground wheat hay. Diets contained 15.9% to 16.3% crude protein and 37.8%, 42.1%, 53.5%, and 55.4% neutral detergent fiber (NDF) with 10.0%, 15.8%, 50.1%, and 55.5% particle retention on a 19-mm sieve, and 26.1%, 29.6%, 38.3%, and 40.0% physically effective NDF (peNDF) for 40F, 50F, 60F, and 70F, respectively. Dry matter intake (2.71, 2.75, 1.96, and 1.95 kg/d) and milk yield (2.82, 2.71, 2.23, and 2.10 kg/d for 40F, 50F, 60F, and 70F, respectively) were lower (P < 0.05) for the two diets highest in forage. Digestion of organic matter was similar among diets (P > 0.05), but digestibility of NDF was greater (P < 0.05) for 60F and 70F (57.5%, 58.4%, 68.9%, and 72.2% for 40F, 50F, 60F, and 70F, respectively). Diet affected (P < 0.05) milk fat (3.16%, 3.37%, 2.93%, and 2.97%) and protein concentrations (2.62%, 2.69%, 2.58%, and 2.52% for 40F, 50F, 60F, and 70F, respectively). Milk energy yield was greater (P < 0.05) for the two diets lowest in forage (7.51, 7.45, 5.68, and 5.34 MJ/d), although yield relative to dry matter intake was not affected (P > 0.05) by diet and was lower (P < 0.05) for primiparous vs. multiparous goats (2.71 and 3.09 MJ/kg). Ruminal pH and acetate proportion were greater for 60F and 70F than for the other diets and the proportion of butyrate was lower for the two diets highest in fiber. The mean lengths of time spent ruminating, eating, standing, and lying were not affected (P > 0.05) by diet or parity, but many interactions involving diet, period, hour, and parity were significant (P < 0.05). In conclusion, lactational performance of Alpine goats in early to mid-lactation will be constrained with diets high in forage of moderate quality, peNDF content, and large particle size, which appeared related to limited feed intake.

Structural equation models to infer relationships between energy-related blood metabolites and milk daily energy output in Holstein cows.

During lactation, high-yielding cows experience metabolic disturbances due to milk production. Metabolic monitoring offers valuable insights into how cows manage these challenges throughout the lactation period, making it a topic of considerable interest to breeders. In this study, we used Bayesian networks to uncover potential dependencies among various energy-related blood metabolites, i.e., glucose, urea, beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), cholesterol (CHOL), and daily milk energy output (dMEO) in 1,254 Holstein cows. The inferred causal structure was then incorporated into structural equation models (SEM) to estimate heritabilities and additive genetic correlations among these phenotypes using both pedigree and genotypes from a 100k chip. Dependencies among traits were determined using the Hill-Climbing algorithm, implemented with the posterior distribution of the residuals obtained from the standard multiple-trait model. These identified relationships were then used to construct the SEM, considering both direct and indirect relationships. The relevant dependencies and path coefficients obtained, expressed in units of measurement variation of 1σ, were as follows: dMEO → CHOL (0.181), dMEO → BHB (-0.149), dMEO → urea (0.038), glucose → BHB (-0.55), glucose → urea (-0.194), CHOL → urea (0.175), BHB → urea (-0.049), and NEFA → urea (-0.097). Heritabilities for traits of concern obtained with SEM ranged from 0.09 to 0.2. Genetic correlations with a minimum 95% probability (P) of the posterior mean being >0 for positive means or <0 for negative means include those between dMEO and glucose (-0.583, P = 100), dMEO and BHB (0.349, P = 99), glucose and CHOL (0.325, P = 100), glucose and NEFA (-0.388, P = 100), and NEFA and BHB (0.759, P = 100). The results of this analysis revealed the existence of recursive relationships among the energy-related blood metabolites and dMEO. Understanding these connections is paramount for establishing effective genetic selection strategies, enhancing production and animal welfare.

Supplementation of Multistrain Probiotics Improves Milk Production, Blood Metabolites, Digestibility, and Rectal Microbiota during the Prepartum and Early Lactation Stages in Crossbred Cows

The current study aimed to study the effects of administration with a multistrain probiotic formulation (MPF) initiated from the prepartum stage on lactation performance, digestibility, rectal microbiota, and blood metabolites of postpartum dairy cows. A total of 30 multiparous crossbred (Holstein Friesian × Balady) dairy cows were randomized into three groups: control (no MPF supplementation), MPF1 (0.5 g MPF/cow/d), and MPF2 (1 g MPF/cow/d). The administration of MPF started 28 days before calving and continued for 84 days after. The results revealed that cows in the MPFI and MPF2 groups had higher milk production, 3.5% FCM, and ECM than those in the control group. The MPF‐supplemented cows had significantly greater milk energy output, DMI, and yields of solids‐not‐fat, lactose, total solids, ash, fat, and protein. The MPF supplementation significantly enhanced feed conversion and significantly interacted with milk solids‐not‐fat, lactose, total solids, and protein. Hematological indicators did not significantly alter between the MPF and control groups. However, cows receiving MPF supplements had higher levels of Hct. Serum biochemical measurements showed lower serum concentrations of LDL, total cholesterol, and VLDL in MPF‐fed cows than in the control group. The digestibility of organic and dry matter tended to be higher in MPF‐supplemented cows. The populations of lactobacillus, bacillus, and total bacterial count increased due to MPF administration, while the count of Clostridium, Salmonella, E. coli, and coliforms decreased in MPF‐fed cows. In summary, administering MPF during late gestation and early lactation period improved milk production, fecal microbial composition, and overall health of dairy cows.

205 Level of Supplemental Fat in the Diet of Gestating Beef Cows: Effects on Cow and Calf Performance

Abstract This study evaluated the effects of feeding a canola seed-based (7.2% ether extract) pellet to gestating cows on cow performance, reproductive efficiency, milk yield and composition, and calf birth weight. Seventy-two pregnant, multiparous cows were allocated to 12 pens in a completely randomized block design. Body weight (BW; 605 ± 35 kg) was utilized as the blocking criteria. Diets were formulated to be isonitrogenous (CP: 8.20 ± 0.24% and 9.07 ± 0.05% second and third trimesters, respectively) and isocaloric (TDN: 58.29 ± 0.24% and 60.50 ± 0.04% second and third trimesters, respectively), and to meet NASEM (2016) nutrient requirements for pregnant beef cattle. Pens were randomly assigned to three replicated (n = 4) dietary treatments: 0 (CON), 150 (LOW), and 300 (HIGH) g of fat/d (DM basis). Dietary treatments were fed from 148 ± 8 d prepartum until at least 50% of all cows had calved, then switched to a common lactation diet. Body condition score (BCS), BW and subcutaneous fat thickness were measured at the start (SOT) and end of trial (EOT), and at 21 and 42 d postpartum. Orthogonal contrasts were used to assess linear and quadratic relationships between fat inclusion and dependent variables. At SOT, there were no differences (P ≥ 0.73) in conceptus corrected BW (597 ± 34 kg) or (P ≥ 0.13) BCS (2.85 ± 0.12, Canadian System: 1 to 5). After 84 d on trial (64 ± 8 d prepartum), conceptus corrected average daily gain (ADG) increased linearly (P = 0.04) as fat inclusion increased. After 151 d of supplementation (EOT), conceptus corrected ADG and subcutaneous fat thickness did not differ (P ≥ 0.71 and 0.63, respectively). BCS change from SOT to EOT increased, while EOT to 21 d postpartum decreased quadratically as fat inclusion increased (P = 0.02 and 0.01, respectively). Female calf birth weight decreased quadratically (P = 0.01) as fat inclusion increased, but there was no effect (P ≥ 0.75) on male calf birth weight. As fat inclusion increased, lactose concentration in milk decreased linearly (P = 0.04). As days in milk (DIM) increased, milk protein, total solids, and milk energy yield decreased (P ≤ 0.05). Milk urea-N tended to increase (P = 0.07), while 12 h milk yield (P = 0.05) tended to decrease as DIM increased. Milk fat and energy were not affected by fat inclusion, day, or the interaction between fat inclusion and day (P ≥ 0.16). There was a quadratic tendency for fat inclusion to affect pregnancy rate (P = 0.09), being maximized on LOW treatment. These results suggest that increasing fat inclusion during mid-to-late gestation tended to improve cow reproductive efficiency. Further investigation is required to determine the optimal level of fat inclusion from canola seed.

Limits to sustained energy intake. XXXIII. Thyroid hormones play important roles in milk production but do not define the heat dissipation limit in Swiss mice.

The limits to sustained energy intake set physiological upper boundaries that affect many aspects of human and animal performance. The mechanisms underlying these limits however remain unclear. We exposed Swiss mice to either supplementary thyroid hormones (THs) or methimazole during lactation at 21 °C or 32.5 °C, and measured food intake, resting metabolic rate (RMR), milk energy output (MEO), serum THs and mammary gland gene expression of females, and litter size and mass of their offspring. Lactating females developed hyperthyroidism following exposure to supplementary THs at 21 °C, but they did not significantly change body temperature, asymptotic food intake, RMR or MEO, and litter and mass were unaffected. Hypothyroidism, induced by either methimazole or 32.5 °C exposure, significantly decreased asymptotic food intake, RMR and MEO, resulting in significantly decreased litter size and litter mass. Furthermore, gene expression of key genes in the mammary gland were significantly decreased by either methimazole or hot exposure, including gene expression of THs and prolactin receptors, and Stat5a and Stat5b. This suggests that endogenous THs are necessary to maintain sustained energy intake and milk energy output. Suppression of the thyroid axis seems to be an essential aspect of the mechanism by which mice at 32.5 °C reduce their lactation performance to avoid overheating. However, THs do not define the upper limit to sustained energy intake and milk energy output at peak lactation at 21 °C. Another, as yet unknown, factor, prevents supplementary thyroxine exerting any stimulatory metabolic impacts on lactating mice at 21 °C.

Liver and Muscle Transcriptomes Differ in Mid-Lactation Cows Divergent in Feed Efficiency in the Presence or Absence of Supplemental Rumen-Protected Choline.

Improving dairy cow feed efficiency is critical to the sustainability and profitability of dairy production, yet the underlying mechanisms that contribute to individual cow variation in feed efficiency are not fully understood. The objectives of this study were to (1) identify genes and associated pathways that are altered in cows with high- or low-residual feed intake (RFI) using RNA sequencing, and (2) determine if rumen-protected choline supplementation during mid-lactation would influence performance or feed efficiency. Mid-lactation (134 ± 20 days in milk) multiparous Holstein cows were randomly assigned to either supplementation of 0 g/d supplementation (CTL; n = 32) or 30 g/d of a rumen-protected choline product (RPC; 13.2 g choline ion; n = 32; Balchem Corp., New Hampton, NY, USA). Residual feed intake was determined as dry matter intake regressed on milk energy output, days in milk, body weight change, metabolic body weight, and dietary treatment. The 12 cows with the highest RFI (low feed efficient; LE) and 12 cows with the lowest RFI (high feed efficient; HE), balanced by dietary treatment, were selected for blood, liver, and muscle analysis. No differences in production or feed efficiency were detected with RPC supplementation, although albumin was greater and arachidonic acid tended to be greater in RPC cows. Concentrations of β-hydroxybutyrate were greater in HE cows. Between HE and LE, 268 and 315 differentially expressed genes in liver and muscle tissue, respectively, were identified through RNA sequencing. Pathway analysis indicated differences in cell cycling, oxidative stress, and immunity in liver and differences in glucose and fatty acid pathways in muscle. The current work indicates that unique differences in liver and muscle post-absorptive nutrient metabolism contribute to sources of variation in feed efficiency and that differences in amino acid and fatty acid oxidation, cell cycling, and immune function should be further examined.

Observational study on the associations between milk yield, composition, and coagulation properties with blood biomarkers of health in Holstein cows

The considerable increase in the production capacity of individual cows owing to both selective breeding and innovations in the dairy sector has posed challenges to management practices in terms of maintaining the nutritional and metabolic health status of dairy cows. In this observational study, we investigated the associations between milk yield, composition, and technological traits and a set of 21 blood biomarkers related to energy metabolism, liver function or hepatic damage, oxidative stress, and inflammation or innate immunity in a population of 1,369 high-yielding Holstein-Friesian dairy cows. The milk traits investigated in this study included 4 production traits (milk yield, fat yield, protein yield, daily milk energy output), 5 traits related to milk composition (fat, protein, casein, and lactose percentages and urea), 11 milk technological traits (5 milk coagulation properties and 6 curd-firming traits). All milk traits (i.e., production, composition, and technological traits) were analyzed according to a linear mixed model that included the days in milk, the parity order, and the blood metabolites (tested one at a time) as fixed effects and the herd and date of sampling as random effects. Our findings revealed that milk yield and daily milk energy output were positively and linearly associated with total cholesterol, nonesterified fatty acids, urea, aspartate aminotransferase, γ-glutamyl transferase, total bilirubin, albumin, and ferric-reducing antioxidant power, whereas they were negatively associated with glucose, creatinine, alkaline phosphatase, total reactive oxygen metabolites, and proinflammatory proteins (ceruloplasmin, haptoglobin, and myeloperoxidase). Regarding composition traits, the protein percentage was negatively associated with nonesterified fatty acids and β-hydroxybutyrate (BHB), while the fat percentage was positively associated with BHB, and negatively associated with paraoxonase. Moreover, we found that the lactose percentage increased with increasing cholesterol and albumin and decreased with increasing ceruloplasmin, haptoglobin, and myeloperoxidase. Milk urea increased with an increase in cholesterol, blood urea, nonesterified fatty acids, and BHB, and decreased with an increase in proinflammatory proteins. Finally, no association was found between the blood metabolites and milk coagulation properties and curd-firming traits. In conclusion, this study showed that variations in blood metabolites had strong associations with milk productivity traits, the lactose percentage, and milk urea, but no relationships with technological traits of milk. Specifically, increasing levels of proinflammatory and oxidative stress metabolites, such as ceruloplasmin, haptoglobin, myeloperoxidase, and total reactive oxygen metabolites, were shown to be associated with reductions in milk yield, daily milk energy output, lactose percentage, and milk urea. These results highlight the close connection between the metabolic and innate immunity status and production performance. This connection is not limited to specific clinical diseases or to the transition phase but manifests throughout the entire lactation. These outcomes emphasize the importance of identifying cows with subacute inflammatory and oxidative stress as a means of reducing metabolic impairments and avoiding milk fluctuations.

The Impact on Cow Performance and Feed Efficiency When Individual Cow Milk Composition and Energy Intake Are Accounted for When Allocating Concentrates

The objective of this three-treatment, 12-week study (involving 69 dairy cows) was to test three methods of concentrate allocation on milk production efficiency. All treatments were offered a basal mixed ration of grass silage and concentrates, with additional concentrates offered to individual cows based on either milk yield alone (Control), milk energy output (Precision 1) or energy intake and milk energy output (Precision 2). Concentrate requirements were calculated and adjusted weekly. Control cows had lower concentrate dry matter intake (DMI; p = 0.040) and milk protein content (p = 0.003) but yield of milk and energy-corrected milk (ECM), energy balance, bodyweight and condition score were unaffected by treatment. Efficiency measures such as ECM/DMI and ECM/metabolizable energy intake were also unaffected by treatment. Less concentrates were used per kg ECM yield in the Control compared to the Precision treatments (p &lt; 0.001). In conclusion, accounting for individual cow milk composition or milk composition combined with individual cow energy intake did not improve production efficiency compared to an approach based on individual cow milk yield only.

Enhancing the recovery of human-edible nutrients in milk and nitrogen efficiency throughout the lactation cycle by feeding fatty acid supplements

Dairy cows convert low-quality feedstuffs unsuitable for human consumption into milk, a high-quality protein source for humans. Even under grazing conditions of well-managed pastures, dietary energy limits the efficiency of animal production, contributing to the excretion of nutrients to the environment. Thus, our study aimed to assess the effect of supplying sources and levels of supplemental fat to grazing dairy cows during early lactation on nutrient excretion and recovery of human-edible (HE) nutrients in milk throughout the lactation cycle. Two experiments were conducted with grazing Jersey × Holstein dairy cows. In Experiment 1, five dairy cows were used in a 5 × 5 Latin Square design. Treatments were a control diet (concentrate without supplemental fat) or diets supplemented with calcium salts of either soybean fatty acids (CSSO) or palm fatty acids (CSPO) fed at two levels of supplementation (400 g/day or 700 g/day) for 24 days. In general, the level of supplemental fat had a minor effect on production parameters and methane emission and intensity. Feeding cows with CSPO increased milk yield by 8.1%, milk energy output by 20%, and milk fat yield by 35.2% compared with CSSO. A tendency was observed for CSPO to decrease methane per unit of milk energy compared with CSSO. In experiment 2, 24 dairy cows were used in a randomized block design. Treatments were a control diet or diets supplemented with calcium salts of either CSSO or CSPO fed at 400 g/day for 13 weeks. The carryover effect of the diets was evaluated until 42 weeks of lactation. During the supplementation period, feeding CSPO improved the recovery of HE energy, protein, and indispensable amino acids compared with control and CSSO. Interestingly, we demonstrated that feeding CSPO improved the recovery of HE energy, protein, and indispensable amino acids compared with control over the lactation cycle. Overall, our results suggested that the dose of supplemental fat used in our study had a minor influence on production and rumen fermentation parameters. We demonstrated that feeding dairy cows with a fatty acid source based on palm oil under tropical grazing conditions reduced nutrient excretion and improved the recovery of HE nutrients throughout the lactation cycle.

Dietary supplementation with xylooligosaccharides and exogenous enzyme improves milk production, energy utilization efficiency and reduces enteric methane emissions of Jersey cows

BackgroundSustainable strategies for enteric methane (CH4) mitigation of dairy cows have been extensively explored to improve production performance and alleviate environmental pressure. The present study aimed to investigate the effects of dietary xylooligosaccharides (XOS) and exogenous enzyme (EXE) supplementation on milk production, nutrient digestibility, enteric CH4 emissions, energy utilization efficiency of lactating Jersey dairy cows. Forty-eight lactating cows were randomly assigned to one of 4 treatments: (1) control diet (CON), (2) CON with 25 g/d XOS (XOS), (3) CON with 15 g/d EXE (EXE), and (4) CON with 25 g/d XOS and 15 g/d EXE (XOS + EXE). The 60-d experimental period consisted of a 14-d adaptation period and a 46-d sampling period. The enteric CO2 and CH4 emissions and O2 consumption were measured using two GreenFeed units, which were further used to determine the energy utilization efficiency of cows.ResultsCompared with CON, cows fed XOS, EXE or XOS + EXE significantly (P < 0.05) increased milk yield, true protein and fat concentration, and energy-corrected milk yield (ECM)/DM intake, which could be reflected by the significant improvement (P < 0.05) of dietary NDF and ADF digestibility. The results showed that dietary supplementation of XOS, EXE or XOS + EXE significantly (P < 0.05) reduced CH4 emission, CH4/milk yield, and CH4/ECM. Furthermore, cows fed XOS demonstrated highest (P < 0.05) metabolizable energy intake, milk energy output but lowest (P < 0.05) of CH4 energy output and CH4 energy output as a proportion of gross energy intake compared with the remaining treatments.ConclusionsDietary supplementary of XOS, EXE or combination of XOS and EXE contributed to the improvement of lactation performance, nutrient digestibility, and energy utilization efficiency, as well as reduction of enteric CH4 emissions of lactating Jersey cows. This promising mitigation method may need further research to validate its long-term effect and mode of action for dairy cows.

Dietary Vitamin E and/or Hydroxytyrosol Supplementation to Sows during Late Pregnancy and Lactation Modifies the Lipid Composition of Colostrum and Milk.

Modifying the composition of a sow's milk could be a strategy to improve the intestinal health and growth of her piglet during the first weeks of life. This study evaluated how dietary supplementation of vitamin E (VE), hydroxytyrosol (HXT) or VE+HXT given to Iberian sows from late gestation affected the colostrum and milk composition, lipid stability and their relationship with the piglet's oxidative status. Colostrum from VE-supplemented sows had greater C18:1n-7 than non-supplemented sows, whereas HXT increased polyunsaturated (∑PUFAs), ∑n-6 and ∑n-3 fatty acids. In 7-day milk, the main effects were induced by VE supplementation that decreased ∑PUFAs, ∑n-6 and ∑n-3 and increased the Δ-6-desaturase activity. The VE+HXT supplementation resulted in lower desaturase capacity in 20-day milk. Positive correlations were observed between the estimated mean milk energy output and the desaturation capacity of sows. The lowest concentration of malondialdehyde (MDA) in milk was observed in VE-supplemented groups, whereas HXT supplementation increased oxidation. Milk lipid oxidation was negatively correlated with the sow's plasma oxidative status and to a great extent with the oxidative status of piglets after weaning. Maternal VE supplementation produced a more beneficial milk composition to improve the oxidative status of piglets, which could promote gut health and piglet growth during the first weeks, but more research is needed to clarify this.

Genomic dominance variance analysis of health and milk production traits in German Holstein cattle.

Genomic analyses commonly explore the additive genetic variance of traits. The non-additive variance, however, is usually small but often significant in dairy cattle. This study aimed at dissecting the genetic variance of eight health traits that recently entered the total merit index in Germany and the somatic cell score (SCS), as well as four milk production traits by analysing additive and dominance variance components. The heritabilities were low for all health traits (between 0.033 for mastitis and 0.099 for SCS), and moderate for the milk production traits (between 0.261 for milk energy yield and 0.351 for milk yield). For all traits, the contribution of dominance variance to the phenotypic variance was low, varying between 0.018 for ovarian cysts and 0.078 for milk yield. Inbreeding depression, inferred from the SNP-based observed homozygosity, was significant only for the milk production traits. The contribution of dominance variance to the genetic variance was larger for the health traits, ranging from 0.233 for ovarian cysts to 0.551 for mastitis, encouraging further studies that aim at discovering QTLs based on their additive and dominance effects.

A genomic assessment of the correlation between milk production traits and claw and udder health traits in Holstein dairy cattle

Claw diseases and mastitis represent the most important disease traits in dairy cattle with increasing incidences and a frequently mentioned connection to milk yield. Yet, many studies aimed to detect the genetic background of both trait complexes via fine-mapping of quantitative trait loci. However, little is known about genomic regions that simultaneously affect milk production and disease traits. For this purpose, several tools to detect local genetic correlations have been developed. In this study, we attempted a detailed analysis of milk production and disease traits as well as their interrelationship using a sample of 34,497 50K genotyped German Holstein cows with milk production and claw and udder disease traits records. We performed a pedigree-based quantitative genetic analysis to estimate heritabilities and genetic correlations. Additionally, we generated GWAS summary statistics, paying special attention to genomic inflation, and used these data to identify shared genomic regions, which affect various trait combinations. The heritability on the liability scale of the disease traits was low, between 0.02 for laminitis and 0.19 for interdigital hyperplasia. The heritabilities for milk production traits were higher (between 0.27 for milk energy yield and 0.48 for fat-protein ratio). Global genetic correlations indicate the shared genetic effect between milk production and disease traits on a whole genome level. Most of these estimates were not significantly different from zero, only mastitis showed a positive one to milk (0.18) and milk energy yield (0.13), as well as a negative one to fat-protein ratio (-0.07). The genomic analysis revealed significant SNPs for milk production traits that were enriched on Bos taurus autosome 5, 6, and 14. For digital dermatitis, we found significant hits, predominantly on Bos taurus autosome 5, 10, 22, and 23, whereas we did not find significantly trait-associated SNPs for the other disease traits. Our results confirm the known genetic background of disease and milk production traits. We further detected 13 regions that harbor strong concordant effects on a trait combination of milk production and disease traits. This detailed investigation of genetic correlations reveals additional knowledge about the localization of regions with shared genetic effects on these trait complexes, which in turn enables a better understanding of the underlying biological pathways and putatively the utilization for a more precise design of breeding schemes.

PSVIII-B-9 Effects of Level and Type of Fiber Sources on Feed Intake, Average Daily Gain, Digestion, and Milk Production by Alpine Goats

Abstract Thirty Alpine does and 32 doelings, averaging 45±1.5 days-in-milk, were used in a study with four 4-wk periods to determine effects of level and type of neutral detergent fiber (NDF) sources on feed intake, average daily gain (ADG), digestion, and milk production. The 60C, 50C, 50W20S, and 40W30S diets were 60, 50, 30, and 30% concentrate and 40, 50, 50, and 40% forage, with 20 and 30% soybean hulls in 50W20S and 40W30S, respectively. Diet NDF concentration was 36, 39, 52, and 52% for 60C, 50C, 50W20S, and 40W30S, respectively. Overall dry matter intake (DMI) was highest (P&amp;lt; 0.05) for 60C and 50C, but differences were greater in periods 1 (2.96, 2.76, 2.06, and 2.27) and 2 (2.67, 2.76, 2.18, and 2.35) than in periods 3 (2.60, 2.55, 2.04, and 2.28) and 4 (2.38, 2.32, 2.07, and 2.13 kg/day for 60C, 50C, 50W20S, and 40W30S, respectively; SEM=0.142). There was a three-way interaction in ADG, with values of 31, 32, -22, and -10 for doelings (SEM=15.1) and 8, 0, -22, and -11 g for does consuming 60C, 50C, 50W20S, and 40W30S, respectively (SEM=18.6). Digestion of organic matter after period 4 was 71.3, 71.3, 80.1, and 80.7% (SEM=0.95) and of NDF was 44.7, 48.8, 73.7, and 75.8% for 60C, 50C, 50W20S, and 40W30S, respectively (SEM=1.56). Milk fat concentration was highest (P&amp;lt; 0.05) for 40W30S (2.81, 2.92, 2.85, and 3.13%; SEM=0.051), with raw milk yield similar among treatments (3.10, 2.87, 2.64, and 2.79 kg/day 60C, 50C, 50W20S, and 40W30S, respectively; SEM=0.144). Average milk energy yield was 7.61, 7.20, 6.48, and 7.20 MJ/day (SEM=0.354) and 2.85, 2.90, 3.11, and 3.18 MJ/kg DMI for 60C, 50C, 50W20S, and 40W30S, respectively (SEM=0.130). In conclusion, high-NDF diets may limit feed intake more in mid- than late lactation and restrict ADG of doelings; however, perhaps because of differences in digestibility, they did not significantly affect milk energy yield.

The thermal neutral zone is shifted during lactation in striped hamsters

The thermoneutral zone (TNZ), one of the most well-recognized concepts of thermal physiology of homeothermic organisms, is observed to differ between animal species, and may be associated with energy expenditure. However, the characteristics of the TNZ of lactating females, the stage of life history with typically the highest energy demands, remain unclear. In this study, we examined body mass, metabolic rate, TNZ and body composition, and milk energy output, in striped hamsters (Cricetulus barabensis, mean body mass: 29.1 ± 4.4g ranging from 20.0 to 36.6g) at peak lactation, and in hamsters raising small, medium, and large litter sizes throughout lactation.There was a significant downward shift in the lower critical temperature (LCT) of the TNZ in lactating hamsters (TNZ = 22.5–35 °C), resulting in a wider TNZ compared to non-reproductive females (TNZ = 27.5–32.5 °C). At peak lactation, hamsters raising large litter sizes had a considerably lower LCT and a wider TNZ compared to hamsters raising medium and small sized litters, whose upper critical temperature of the TNZ remain fixed. Compared to virgin hamsters, hamsters at peak lactation consumed 2.5 times more food, and had significantly higher energy expenditure corresponding to a significantly higher resting metabolic rate and milk output to meet the requirements of their offspring, which increased with litter size. The organs with the highest oxygen consumption rates, such as the liver, kidneys, and digestive tracts, were considerably heavier in lactating hamsters, particular in those raising large litter sizes, compared to virgin hamsters. The data show that the increased energy expenditure during lactation induces a substantial downward shift of the LCT, consequently resulting in a wider TNZ. The morphological plasticity of organs with high energy requirements is likely involved in this TNZ shift.

Influence of Functional Feed Supplements on the Milk Production Efficiency, Feed Utilization, Blood Metabolites, and Health of Holstein Cows during Mid-Lactation

A 70-day feeding trial was performed to assess the effect of feeding a mixture of functional feed supplements (FFS; contains encapsulated cinnamaldehyde, condensed tannins, capsaicin, piperine, and curcumin) during mid-lactation on the milk production and composition, feed intake, and blood profile of multiparous dairy cows. Sixty Holstein dairy cows (116.1 ± 17.1 days in milk, 606 ± 9.3 kg BW, and 45.73 ± 6.7 kg/d milk production) were distributed into two trial groups: control (CON: n = 30), which received a basal diet; and FFS (n = 30) treatment, which received a basal diet fortified with the FFS at a rate of 35 g/day/head. The results revealed that daily milk production (p = 0.01) and solids-not-fat yield (p = 0.05) were significantly higher in dairy cows that had received FFS compared with the control group. In addition, the 3.5% fat-corrected milk, energy-corrected milk, lactose and protein yields, and milk energy output tended to be higher (p ≤ 0.10) in dairy cattle that consumed FFS during the experimental period. Significant treatment x period interactions were identified (p ≤ 0.02) with respect to feed efficiency and somatic cell count. Dry matter intake tended to be greater (p = 0.064) in dairy cattle that consumed FFS during weeks 0–2 and 2–4 of the trial period. Most serum biochemical parameters were not changed (p ≥ 0.114) between FFS and control cows. However, a greater concentration of serum albumin (p = 0.007) was observed in cows fed diets supplemented with FFS. In summary, supplementing FFS to lactating Holstein cows during mid-lactation was associated with enhanced lactation performance, feed efficiency, and a tendency to increase feed intake, with no obvious adverse effects.