摘要
本研究旨在探讨高温环境条件下,高产与中产奶牛产奶量、乳组成和瘤胃发酵的差异。试验选择24头中国荷斯坦奶牛,根据配对试验设计原则,分为高产奶牛组[产奶量:(40.40±3.60)kg/d]和中产奶牛组[产奶量:(30.46±1.92)kg/d],每组12头牛。试验在炎热的夏季进行,每7 d测定1次产奶量和乳组成。试验最后1周,在早晨饲喂后5 h,利用专用口腔采样器采集瘤胃液,测定pH、氨氮、总挥发性脂肪酸、乙酸、丙酸、丁酸、戊酸和异戊酸含量。试验期间每日07:00、14:00和22:00的平均温湿指数分别为:79.29、81.79和78.84,试验牛主要经历了轻度和高度热应激。结果显示:高产奶牛产奶量下降幅度(0.96 kg/wk)显著高于中产奶牛(0.62 kg/wk)(P<0.05);高产奶牛乳脂率显著高于中产奶牛(P<0.05),乳蛋白含量极显著低于中产奶牛(P<0.01),乳糖含量显著低于中产奶牛(P<0.05),体细胞评分显著高于中产奶牛(P<0.05);高产奶牛瘤胃液乙酸与丙酸比极显著低于中产奶牛(P<0.01)。结果提示,在高温环境条件下,高产奶牛产奶量下降幅度大于中产奶牛,热应激对高产奶牛瘤胃功能的负面影响程度大于中产奶牛。
The objective of this study was to investigate the difference of performance and ruminal fermentation between high and mid lactating dairy cows in hot weather. Twenty four Chinese Holstein dairy cows were assigned to high lactating dairy cows group Emilk yield： （40.40 ± 3.60） kg/d] and mid lactating dairy cows group [milk yield： （30.46 ±1.92） kg/d] according to paired experiment design and each group contained 12 cows. The experiment was in hot summer, milk yield was recorded and milk component was determined weekly. The rumen fluid was collected 5 h in the morning post-feeding via oral cavity with stomach-tube in the last week of the experiment to test pH, ammonia nitrogen, total volatile fatty acid, acetate, propionate, butyrate, valerate and isovalerate. The average temperature humidity index of barn was 79.29, 81.79 and 78.84 at 07：00, 14：00 and 22：00 during the experimental period, respectively. The experimental animals suffered mild and high heat stress. The results showed that the milk yield was decreased faster for high lactating cows （0. 96 kg/wk） than mid lactating cows （0.62 kg/wk） （P〈0.05）. The milk fat content in the high lactating cows was higher than that in mid lactating cows （P〈0.05）. The milk protein in the high lactating cows was extremely lower than that in the mid lactating cows （P〈0.01）. The lactose in the high lactating cows was lower than that in the mid lactating cows （P〈0.05） and the somatic cell score was higher for the high lactating cows than that for the mid lactating cows （P〈0.05）. The ratio of acetate to propionate was extremely lower in the high lactating cows compared with the mid lactating cows （P〈0.01）. These results indicated that milk yield and ruminal function were negatively affected severely for the high lactating cows compared with the mid lactating cows in hot weather.
出处
《动物营养学报》
CAS
CSCD
北大核心
2010年第1期51-56,共6页
CHINESE JOURNAL OF ANIMAL NUTRITION
基金
"十一五"国家奶业科技支撑计划(2006BAD04A14
2006BAD12B08)
关键词
热应激
奶牛
产奶性能
瘤胃发酵
Heat stress
Dairy cows
Performance
Ruminal fermentation
