Department of Animal Science, Iowa State University, Ames 50011.
Department of Animal Science, Iowa State University, Ames 50011.
J Dairy Sci. 2023 Apr;106(4):2890-2903. doi: 10.3168/jds.2022-22689. Epub 2023 Feb 22.
Study objectives were to evaluate the effects of hindgut acidosis (HGA) on production, metabolism, and inflammation in feed-restricted (FR) dairy cows. Twelve rumen-cannulated cows were enrolled in a study with 3 experimental periods (P). During P1 (5 d), baseline data were collected. During P2 (2 d), all cows were FR to 40% of their baseline feed intake. During P3 (4 d), cows remained FR and were assigned to 1 of 2 abomasal infusion treatments: (1) control (FR-CON; 6 L of HO/d; n = 6) or (2) starch (FR-ST; 4 kg of corn starch + 6 L of HO/d; n = 6). Respective treatments were partitioned into 4 equal doses (1 kg of corn starch/infusion) and were abomasally infused daily at 0000, 0600, 1200, and 1800 h. All 3 P were analyzed independently and the effects of treatment, time, and treatment × time were assessed using PROC MIXED, and P1 and P2 data were analyzed using the treatments cows were destined to be assigned to during P3. Hallmark production and metabolic responses to feed restriction were observed in both treatments, including decreased milk yield (39%) and energy-corrected milk (32%), circulating glucose (12%), insulin (71%), and increased circulating nonesterified fatty acids (3.2-fold) throughout both P2 and P3, relative to P1. However, despite a marked reduction in fecal pH (0.96 units), the aforementioned metrics were unaltered by HGA. During P3, starch infusions increased circulating β-hydroxybutyrate, with the most pronounced increase occurring on d 2 (81% relative to FR-CON). Further, feed restriction decreased blood urea nitrogen during P2 (17% relative to P1) in both treatments, and this was exacerbated by starch infusions during P3 (31% decrease relative to FR-CON). In contrast to our hypothesis, neither feed restriction nor HGA increased circulating acute-phase proteins (serum amyloid A and lipopolysaccharide binding protein) relative to P1 or FR-CON, respectively. Thus, despite marked reductions in fecal pH, prior feed restriction did not appear to increase the susceptibility to HGA.
研究目的在于评估后肠酸中毒（HGA）对限饲（FR）奶牛生产、代谢和炎症的影响。12 头瘤胃瘘管奶牛参与了这项研究，共分为 3 个实验期（P）。在 P1（5 天）期间，收集基线数据。在 P2（2 天）期间，所有奶牛的饲料摄入量减少到基线的 40%。在 P3（4 天）期间，奶牛继续限饲，并被分配到以下 2 种瘤胃输注处理中的 1 种：（1）对照（FR-CON；每天 6 升 HO，n=6）或（2）淀粉（FR-ST；每天 4 公斤玉米淀粉+6 升 HO，n=6）。相应的处理分为 4 等份剂量（1 公斤玉米淀粉/输注），每天 0000、0600、1200 和 1800 小时分别进行瘤胃输注。使用 PROC MIXED 分析所有 3 个 P，评估处理、时间和处理×时间的影响，同时使用 P3 中奶牛预定接受的处理分析 P1 和 P2 数据。在两种处理中均观察到与限饲相关的标志性生产和代谢反应，包括产奶量（39%）和能量校正奶（32%）、循环葡萄糖（12%）、胰岛素（71%）和非酯化脂肪酸（3.2 倍）的增加，整个 P2 和 P3 期间都高于 P1。然而，尽管粪便 pH 值显著降低（0.96 个单位），但上述指标并未因 HGA 而改变。在 P3 期间，淀粉输注增加了循环β-羟丁酸，在第 2 天（相对于 FR-CON 增加 81%）最为明显。此外，在两种处理中，P2 期间的限饲都会降低血液尿素氮（相对于 P1 降低 17%），而在 P3 期间的淀粉输注会加剧这种情况（相对于 FR-CON 降低 31%）。与我们的假设相反，限饲或 HGA 都没有使循环急性期蛋白（血清淀粉样蛋白 A 和脂多糖结合蛋白）相对于 P1 或 FR-CON 增加。因此，尽管粪便 pH 值显著降低，但先前的限饲似乎并没有增加对 HGA 的易感性。
