Meta-analysis of rumination behavior and its relationship with milk and milk fat production, rumen pH, and total-tract digestibility in lactating dairy cows.

Time spent ruminating is affected by diet and affects the rumen environment. The objective of the current study was to conduct a meta-regression to characterize the variation in rumination time and its relationship with milk and milk fat yields and variables mechanistically associated with milk fat synthesis, including rumen pH and total-tract digestibility. The analysis included 130 journal articles published between 1986 and 2018 that reported 479 treatment means from lactating Holsteins cows during established lactation. Milk yield averaged 34.3 kg/d (range 14.2-52.1 kg/d), milk fat averaged 3.47% (range 2.20-4.60%), and rumen pH averaged 6.1 (range 5.3-7.0). Rumination observation systems were categorized into 6 groups, but there was little difference in average rumination time among systems. The total time spent ruminating averaged 444 min/d (range 151-638 d) and occurred in 13.8 bouts/d (range 7.8-17.4 bouts/d) that averaged 32.7 min (range 20.0-48.1 min). Bivariate regressions were modeled to include the random effect of study, and correlations were evaluated through the partial R2 that excluded variation accounted for by the random effect. Rumination time was quadratically increased with increasing milk fat yield (partial R2 = 0.27) and milk fat percent (partial R2 = 0.17). Rumination was also increased with increasing milk yield, dry matter intake, and rumen pH, and was quadratically related to dietary neutral detergent fiber (NDF) and total-tract NDF digestibility (partial R2 = 0.10-0.27). Similar relationships were observed for rumination per unit of dry matter and NDF intake. The best-fit multivariate model predicting total rumination time included milk yield, milk fat yield, and concentration and accounted for 37% of the variation. Total-tract digestibility was available for 217 treatment means; when included in the model, the partial R2 increased to 0.41. Last, principal component analysis was conducted to explore the relationship among variables. The first 2 principal components in the broad analyses explained 36.7% of the 39 variables evaluated, which included rumination bouts and time spent ruminating. In conclusion, rumination time was related to milk fat across a large number of studies, although it explained only a limited amount of the variation in milk fat.

Maintenance and Growth Requirements in Male Dorper × Santa Ines Lambs.

The aim of this study was to estimate the energy and protein requirements for maintenance and growth of lambs. A total of 35 crossbreed Dorper × Santa Ines lambs [31 ± 1.28 kg of initial body weight (BW) and 4 months old] were distributed in a completely randomized design with three treatments groups (ad libitum, 30 and 60% of feed restriction). Five lambs were slaughtered at the beginning of the experimental trial as a reference group to estimate the initial empty BW (EBW) and body composition. When the animals of the ad libitum treatment reached a BW average of 47.2 kg, at day 84 of trial, all lambs were slaughtered. The feed restriction promoted reduction in body fat (P < 0.001) and energy concentration (P < 0.001), while protein showed a quadratic response (P = 0.05). The equations obtained for NEg and NPg requirements were 0.2984 × EBW0.75 × EBWG0.8069 and 248.617 × EBW-0.15546, respectively. The net energy (NEm) and protein (NPm) for maintenance were 71.00 kcal/kg EBW0.75/day and 1.76 g/kg EBW0.75/day, respectively. In conclusion, the NEg and NPg requirement for lambs with 30 kg of BW and 200 g of average daily gain (ADG) were 0.736 Mcal/day and 24.38 g/day, respectively. Our findings indicate that the NEm for crossbreed Dorper × Santa Ines lambs is similar to those recommended by the international committees; however, we support the hypothesis that the requirements for gain are lower.

Performance of growing lambs supplemented with ground licuri (Syagrus coronata).

OBJECTIVE: The aim of this study was to determine the effect of dietary ground licuri on lamb performance. METHODS: Forty male lambs were used in a completely randomized design to test the effects of 0, 5, 10, and 15 g/kg of ground licuri added to diets. The trial lasted for 75 days. Intake, digestibility, physically effective neutral detergent fiber, and chewing activity were estimated. Blood samples were taken on day 45 to determine the concentrations of glucose, urea, nonesterified fatty acids, and triglycerides. Average daily gain (ADG) were determined on the last day of the experimental trial. RESULTS: Licuri inclusion markedly increased dietary neutral detergent fiber and ether extract (EE) content, but it decreased dry matter (DM) intake. However, the intake and digestibility of EE linearly increased. The ADG decreased linearly (p<0.05) with licuri inclusion. Licuri had no effect (p>0.05) on the concentrations of blood metabolites; however, blood urea increased (p<0.05), while serum glucose decreased (p<0.05). CONCLUSION: The physically effective fiber of ground licuri is similar to Tyfton hay and licuri inclusion decreases lamb performance due to a decreased in DM intake.

Effects of ammoniated pearl millet silage on intake, feeding behavior, and blood metabolites in feedlot lambs.

The aim of this study was to evaluate the effects of urea as an additive in the ensiling of pearl millet on the intake, feeding behavior, and metabolic parameters of feedlot-finished lambs. Thirty-two uncastrated, mixed-breed male lambs were used in the experiment. Diets were composed of pearl millet silage enriched with 0, 2, 4, or 6% urea plus a concentrate containing ground corn, soybean meal, and a mineral mixture. The treatments did not affect feed intake (P > 0.05) but influenced (P < 0.05) eating time (in min/day, in min/kg of dry matter (DM), and in min/kg of neutral detergent fiber (NDF)) and chewing time in min/kg of DM. Eating efficiency (in g DM/h and in g NDFap/h) responded linearly (P < 0.05) to the increasing urea levels in the silages. By contrast, there was no effect (P > 0.05) of diets on the blood protein profile (total proteins and albumin), although the serum urea levels responded quadratically (P < 0.05). Increasing urea levels in the silage did not change the blood energy profile (cholesterol and triglycerides) or blood enzyme activity (alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT); P > 0.05). In conclusion, the treatment of pearl millet silage with urea does not influence the DM intake or metabolic parameters of lambs, but leads to increased eating time and decreased eating efficiency.