Department of Bioengineering, Universidade Federal de São João del Rei, 36307-352, São João dei Rei, Minas Gerais, Brazil; Department of Animal Science, Michigan State University, East Lansing, MI 48824.
Dairy Cattle Research Laboratory, Universidade Federal do Mato Grosso, 78557-267, Sinop, Mato Grosso, Brazil.
J Dairy Sci. 2024 Sep;107(9):6686-6695. doi: 10.3168/jds.2023-24393. Epub 2024 Apr 11.
Our objective was to estimate the requirements of metabolizable energy (ME) and NE of lactating and dry cows, the efficiency of ME utilization for milk production (k) and tissue gain (k), and the use of body energy mobilization for milk production (k) throughout the lactation of primiparous crossbred Holstein × Gyr cows, using open-circuit respiration chambers. Twenty-nine primiparous Holstein × Gyr crossbred cows with an initial BW averaging 563 ± 40.1 kg and 2.5 ± 0.09 yr old were used throughout lactation and dry periods. The cows were kept nonpregnant throughout the study to eliminate possible confounding factors. Apparent digestibility assays, followed by calorimeter measurements, were performed 6 times throughout the lactation period. In the dry-off period, the cows were also evaluated but fed with restricted intake (DMI = 1.1% BW/d) to achieve heat production close to maintenance. After 21 d of diet adaptation, an apparent digestibility assay followed by calorimeter measurements was performed. Parameter estimates for lactation period were obtained by mixed models including lactation stage as repeated measures. For restricted feeding at dry-off and fasting period assays, the requirements were estimated by exponential regression. For whole lactation, the values of the ME requirement for maintenance (ME) and NE were 0.588 and 0.395 MJ/BW, respectively. The efficiencies of k, k, and k were 0.672, 0.771, and 0.814, respectively. However, ME and NE were higher in early and mid lactation than late, whereas k was higher in early than other lactation stages. Dry and nonpregnant cows had ME of 0.434 MJ/BW and NE of 0.351 MJ/BW for maintenance level, and ME of 0.396 MJ/BW and NE of 0.345 MJ/BW for fasting metabolism level, and efficiency of ME utilization for maintenance was 0.80. Our findings confirmed that F crossbred Holstein × Gyr dairy cows have differences in energy requirement and efficiency throughout the lactation stages, suggesting the use of different values in each stage. The estimated values of energy requirement for maintenance and efficiencies for primiparous lactating crossbred Holstein × Gyr were similar to those reported in the literature in specific studies and requirements systems.
我们的目标是估计泌乳期和干奶期奶牛的代谢能（ME）和净能（NE）需求、ME 用于产奶（k）和组织生长（k）的效率，以及在初产荷斯坦×吉尔杂交奶牛泌乳期内利用体能量动员用于产奶（k）的情况，使用开放式呼吸室。在整个泌乳期和干奶期，使用了 29 头初始体重平均为 563±40.1kg 和 2.5±0.09 岁的初产荷斯坦×吉尔杂交奶牛。在整个研究过程中，奶牛保持非妊娠状态，以消除可能的混杂因素。在泌乳期进行了 6 次表观消化率测定，然后进行量热仪测量。在干奶期，奶牛也进行了评估，但采食量受限（DMI=1.1%BW/d），以达到接近维持的产热。经过 21 天的饮食适应期后，进行表观消化率测定，然后进行量热仪测量。泌乳期的参数估计是通过包括泌乳阶段作为重复测量的混合模型获得的。对于干奶期和禁食期的限制喂养，通过指数回归估计需求。对于整个泌乳期，维持（ME）和 NE 的 ME 需要量分别为 0.588 和 0.395MJ/BW。k、k 和 k 的效率分别为 0.672、0.771 和 0.814。然而，ME 和 NE 在泌乳早期和中期较高，而 k 在早期较高。干奶牛和非妊娠奶牛的维持水平 ME 为 0.434MJ/BW，NE 为 0.351MJ/BW，禁食代谢水平 ME 为 0.396MJ/BW，NE 为 0.345MJ/BW，维持水平 ME 利用率为 0.80。我们的研究结果证实，F 代荷斯坦×吉尔杂交奶牛在泌乳期各阶段的能量需求和效率存在差异，这表明在每个阶段使用不同的值。初产泌乳期杂交荷斯坦×吉尔的维持能量需求和效率的估计值与特定研究和需求系统中文献报道的相似。
