Lough D S, Beede D L, Wilcox C J
Dairy Science Department, University of Florida, Gainesville 32611-0701.
J Dairy Sci. 1990 Feb;73(2):325-32. doi: 10.3168/jds.S0022-0302(90)78677-8.
Six midlactation Holstein cows were exposed to treatments of thermal comfort environments with ad libitum or restricted (70% of ad libitum) DM intake and a thermal stress environment with ad libitum intake in two balanced 3 X 3 Latin squares to evaluate effects on mammary blood flow and other physiological measurements. Daily DM intake decreased from 17.8 kg in thermal comfort with ad libitum intake to 12.5 kg in thermal comfort with restricted intake and to 14.8 kg in thermal stress. Daily milk production decreased from 23.9 kg in thermal comfort ad libitum to 22.2 kg in thermal comfort restricted and 21.6 kg in thermal stress. Mammary blood flows (half udder) over the entire sampling interval (18 h) were 5.1, 4.3, and 4.5 L/min for treatments: thermal comfort, ad libitum intake; thermal comfort, restricted intake; and thermal stress, ad libitum intake. Mammary blood flows did not differ significantly among between treatments. Relationship of hald udder blood flow (L/min) to previous day's DM intake (kg/d) was described by the linear equation: L/min = .49 + (.27 kg/d); r2 = .46; and the quadratic equation: L/min = 6.04 - (.54 kg/d) + (.03 [kg/d]2); r2 = .55. Mammary blood flows 10 min before through 10 min after milking machine attachment were greater for cows at thermal comfort and ad libitum intake than for cows at thermal comfort and restricted intake or thermal stress and ad libitum intake (5.5, 4.8, and 4.8 L/min).
选用6头处于泌乳中期的荷斯坦奶牛，通过两个平衡的3×3拉丁方设计，使其分别处于热舒适环境下自由采食或限饲（自由采食量的70%），以及热应激环境下自由采食的条件，以评估对乳腺血流量和其他生理指标的影响。每日干物质摄入量从热舒适自由采食时的17.8千克，降至热舒适限饲时的12.5千克，以及热应激自由采食时的14.8千克。日产奶量从热舒适自由采食时的23.9千克，降至热舒适限饲时的22.2千克，以及热应激时的21.6千克。在整个采样间隔（18小时）内，不同处理的乳腺血流量（半侧乳房）分别为：热舒适自由采食组5.1升/分钟、热舒适限饲组4.3升/分钟、热应激自由采食组4.5升/分钟。各处理之间的乳腺血流量差异不显著。半侧乳房血流量（升/分钟）与前一天干物质摄入量（千克/天）的关系可用线性方程描述为：升/分钟 = 0.49 +（0.27千克/天）；r² = 0.46；二次方程为：升/分钟 = 6.04 -（0.54千克/天）+（0.03[千克/天]²）；r² = 0.55。在连接挤奶机前10分钟至连接后10分钟期间，热舒适自由采食的奶牛乳腺血流量大于热舒适限饲或热应激自由采食的奶牛（分别为每分钟5.5升、4.8升和4.8升）。
