Veterinary School, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Departament of Animal Science, Unimontes, Janaúba, Minas Gerais, Brazil.
PLoS One. 2021 Feb 4;16(2):e0246208. doi: 10.1371/journal.pone.0246208. eCollection 2021.
The purpose of this study was to determine the energy partition of pregnant F1 Holstein x Gyr with average initial body weight (BW) of 515.6 kg and Gyr cows with average initial BW of 435.1 kg at 180, 210 and 240 days of gestation, obtained using respirometry. Twelve animals in two groups (six per genetic group) received a restricted diet equivalent to 1.3 times the net energy for maintenance (NEm). The proportion of gross energy intake (GEI) lost as feces did not differ between the evaluated breeds and corresponded to 28.65% on average. The daily methane production (L/d) was greater for (P<0.05) F1 HxG compared to Gyr animals. However, when expressed as L/kg dry matter (DM) or as percentage of GEI there were no differences between the groups (P>0.05). The daily loss of energy as urine (mean of 1.42 Mcal/d) did not differ (P>0.05) between groups and ranged from 3.87 to 5.35% of the GEI. The metabolizable energy intake (MEI) of F1 HxG animals was greater (P < 0.05) at all gestational stages compared to Gyr cows when expressed in Mcal/d. However, when expressed in kcal/kg of metabolic BW (BW0,75), the F1 HxG cows had MEI 11% greater (P<0.05) at 240 days of gestation and averaged 194.39 kcal/kg of BW0,75. Gyr cows showed no change in MEI over time (P>0.05), with a mean of 146.66 kcal/kg BW0. 75. The ME used by the conceptus was calculated by deducting the metabolizable energy for maintenance (MEm) from the MEI, which was obtained in a previous study using the same cows prior to becoming pregnant. The values of NEm obtained in the previous study with similar non-pregnant cows were 92.02 kcal/kg BW0.75 for F1 HxG, and 76.83 kcal/kg BW0.75 for Gyr (P = 0.06). The average ME for pregnancy (MEp) was 5.33 Mcal/d for F1 HxG and 4.46 Mcal/d for Gyr. The metabolizability ratio, averaging 0.60, was similar among the evaluated groups (P>0.05). The ME / Digestible Energy (DE) ratio differed between groups and periods evaluated (P<0.05) with a mean of 0.84. The heat increment (HI) accounted for 22.74% and 24.38% of the GEI for F1 HxG and Gyr cows, respectively. The proportion of GEI used in the basal metabolism by pregnant cows in this study represented 29.69%. However, there were no differences between the breeds and the evaluation periods and corresponded to 29.69%. The mean NE for pregnancy (NEp) was 2.76 Mcal/d and did not differ between groups and gestational stages (P>0.05).
本研究的目的是确定在妊娠 180、210 和 240 天，平均初始体重（BW）为 515.6 千克的 F1 荷斯坦 x Gyr 奶牛和平均初始 BW 为 435.1 千克的 Gyr 奶牛的能量分配，使用呼吸代谢法获得。两组中的 12 只动物（每组 6 只）接受了相当于维持净能量（NEm）1.3 倍的限量饮食。摄入的总能（GEI）中作为粪便损失的比例在评估的品种之间没有差异，平均为 28.65%。F1 HxG 与 Gyr 动物相比，甲烷日产量（L/d）更高（P<0.05）。然而，当以每干物质（DM）的 L 或 GEI 的百分比表示时，两组之间没有差异（P>0.05）。尿液中能量的每日损失（平均 1.42 Mcal/d）在组间无差异（P>0.05），范围为 GEI 的 3.87%至 5.35%。与 Gyr 奶牛相比，F1 HxG 动物在所有妊娠阶段的可代谢能摄入量（MEI）都更高（P < 0.05），以 Mcal/d 表示。然而，当以代谢体重（BW0.75）的千卡表示时，F1 HxG 奶牛在 240 天妊娠时的 MEI 增加了 11%（P<0.05），平均为 194.39 千卡/kg BW0.75。Gyr 奶牛的 MEI 随时间没有变化（P>0.05），平均为 146.66 千卡/kg BW0.75。概念体使用的可代谢能通过从 MEI 中扣除维持可代谢能（MEm）来计算，这是在同一批奶牛怀孕前进行的先前研究中获得的。之前在类似非妊娠奶牛中进行的 NEm 研究获得了以下值：F1 HxG 为 92.02 kcal/kg BW0.75，Gyr 为 76.83 kcal/kg BW0.75（P = 0.06）。F1 HxG 的妊娠可代谢能（MEp）为 5.33 Mcal/d，Gyr 为 4.46 Mcal/d。代谢率比值在评估组之间相似，平均为 0.60（P>0.05）。ME/可消化能（DE）比值在组间和评估期之间存在差异（P<0.05），平均值为 0.84。F1 HxG 和 Gyr 奶牛的总能摄入的热增量分别占 22.74%和 24.38%。本研究中妊娠奶牛基础代谢所用的总能比例为 29.69%。然而，在品种和评估期之间没有差异，并且对应于 29.69%。妊娠净能（NEp）的平均值为 2.76 Mcal/d，在组间和妊娠阶段没有差异（P>0.05）。
