Stelwagen K, Davis S R, Farr V C, Eichler S J, Politis I
Dairying Research Corporation Ltd., Ruakura Agricultural Centre, Hamilton, New Zealand.
J Dairy Sci. 1994 Oct;77(10):2994-3001. doi: 10.3168/jds.S0022-0302(94)77240-4.
Six pairs of monozygous Friesian twin cows during late lactation were used to assess the effect of once daily milking and bST treatment on yields and tight junction permeability of mammary epithelial cells. During the first 7 d, all cows were milked twice daily; on d 8 through d 21, all cows were milked once daily, but one cow of each twin pair was treated daily with 20 mg of bST on d 13 through 21; and, finally, during d 22 through 28, all cows were again milked twice daily. Once daily milking, a common management practice in New Zealand, resulted in a small (7%) but significant decrease in milk yield. Treatment with bST increased milk yield by 19%, thereby exceeding the milk yield loss from once daily milking. The integrity of mammary tight junctions was assessed indirectly by measuring concentrations of plasma lactose and milk BSA. Once daily milking temporarily disrupted tight junction integrity, based on a 4- to 5-fold increase in plasma lactose and a 42 to 55% increase in the concentrations of milk BSA. In the present study, bST did not affect the permeability of mammary tight junctions.
选用6对处于泌乳后期的弗里斯兰单卵双胎奶牛，以评估每日一次挤奶和牛生长激素（bST）处理对乳腺上皮细胞产量和紧密连接通透性的影响。在最初7天，所有奶牛每日挤奶两次；在第8天至第21天，所有奶牛每日挤奶一次，但每对双胞胎奶牛中的一头在第13天至21天每天接受20毫克bST处理；最后，在第22天至28天，所有奶牛再次改为每日挤奶两次。每日一次挤奶是新西兰常见的管理方式，导致产奶量小幅（7%）但显著下降。用bST处理使产奶量提高了19%，从而超过了每日一次挤奶造成的产奶量损失。通过测量血浆乳糖和乳牛血清白蛋白（BSA）浓度间接评估乳腺紧密连接的完整性。基于血浆乳糖增加4至5倍以及乳牛血清白蛋白浓度增加42%至55%，每日一次挤奶会暂时破坏紧密连接的完整性。在本研究中，bST不影响乳腺紧密连接的通透性。
