Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Avda. Montañana 930, 50059, Zaragoza, Spain.
Instituto Agroalimentario de Aragón - IA2 (CITA-Universidad de Zaragoza), Zaragoza, Spain.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad053.
Our study objective was to determine the effect of a short feed restriction (4 d) and subsequent refeeding (4 d) on the performance and metabolism of beef cows with a different nutritional status by particularly focusing on their milk fatty acid (FA) profile, to consider its potential use as biomarker of metabolic status. Thirty-two Parda de Montaña multiparous lactating beef cows were individually fed a diet based on the average cow's net energy (NE) and metabolizable protein requirements. At 58 d in milk (DIM, day 0), cows underwent a 4 d feed restriction (55% requirements, restriction period). Before and after the restriction, diets met 100% of their requirements (basal and refeeding periods). Cow performance, milk yield and composition, and plasma metabolites, were determined on day -2, 1, 3, 5, 6, and 8. Cows were classified into two status clusters according to their pre-challenge performance and energy balance (EB) (Balanced vs. Imbalanced). All traits were statistically analyzed considering the fixed effect of status cluster and feeding period or day, with cow as a random effect. Imbalanced cows were heavier and had a more negative EB (P < 0.001), but similar milk yield, milk composition, and circulating metabolites (except for greater urea) than Balanced cows (P > 0.10). Milk contents of C18:1 cis-9, monounsaturated FA (MUFA), and mobilization FA were greater (P < 0.05), whereas saturated FA (SFA) and de novo FA were lesser in Imbalanced than Balanced cows (P < 0.05). Restriction decreased body weight (BW), milk yield, and milk protein compared to the basal period, but increased milk urea and plasma nonesterified fatty acids (NEFA) (P < 0.001). Milk contents of SFA, de novo, and mixed FA decreased immediately during the restriction, while MUFA, polyunsaturated FA and mobilization FA increased (P < 0.001). Basal milk FA contents were recovered on day 2 of refeeding, and all their changes strongly correlated with differences in EB and NEFA (P < 0.05). The general lack of interactions between status clusters and feeding periods implied that the response mechanisms to diet changes did not differ between cows with a different pre-challenge nutritional status.
我们的研究目的是通过特别关注奶牛的乳脂肪酸（FA）谱，确定短期饲料限制（4 天）和随后再喂养（4 天）对具有不同营养状态的肉牛的生产性能和代谢的影响，以考虑其作为代谢状态生物标志物的潜在用途。32 头帕达尔·德·蒙塔尼亚经产泌乳肉牛个体饲喂基于奶牛净能（NE）和可代谢蛋白需求平均值的日粮。在泌乳 58 天（DIM，第 0 天），奶牛进行了 4 天的饲料限制（需求的 55%，限制期）。在限制之前和之后，日粮满足了 100%的需求（基础和再喂养期）。在第-2、1、3、5、6 和 8 天测定奶牛的生产性能、产奶量和组成以及血浆代谢产物。根据挑战前的生产性能和能量平衡（EB）（平衡与不平衡），将奶牛分为两个状态群。考虑到状态群和饲喂期或天数的固定效应，以及奶牛的随机效应，对所有性状进行统计分析。与平衡牛相比，不平衡牛体重更重，EB 更负（P < 0.001），但产奶量、乳成分和循环代谢产物相似（除了尿素更大）（P > 0.10）。不平衡奶牛的乳中 C18:1 cis-9、单不饱和 FA（MUFA）和动员 FA 含量更高（P < 0.05），而饱和 FA（SFA）和从头 FA 含量更低（P < 0.05）。与基础期相比，限制降低了体重（BW）、产奶量和乳蛋白，但增加了乳尿素和血浆非酯化脂肪酸（NEFA）（P < 0.001）。在限制期间，SFA、从头 FA 和混合 FA 的乳含量立即下降，而 MUFA、多不饱和 FA 和动员 FA 增加（P < 0.001）。再喂养第 2 天基础乳 FA 含量恢复，所有变化与 EB 和 NEFA 的差异密切相关（P < 0.05）。状态群和饲喂期之间缺乏一般的相互作用意味着，对日粮变化的反应机制在具有不同挑战前营养状态的奶牛之间没有差异。
