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標題: Functional characterization of mammary gland of Holstein cows under humid tropical summer climates
作者: Lu, C.H.
Chang, C.J.
Lee, P.N.
Wu, C.P.
Chen, M.T.
Zhao, X.
關鍵字: tropics;Holstein cow;lactation;N-acetylglucosaminidase;urea;milk protein depression;amino-acid utilization;lactating dairy-cows;bovine somatotropin;heat-stress;jersey cows;fed fat;environment;metabolism;nitrogen
Project: Asian-Australasian Journal of Animal Sciences
期刊/報告no:: Asian-Australasian Journal of Animal Sciences, Volume 16, Issue 7, Page(s) 988-995.
Physiological parameters were measured on six primiparous, non-pregnant Holstein cows prior to peak lactation over a 3-month summer season in southwestern Taiwan. The objectives were to characterize heat stress-induced change in functionality of mammary gland under natural climates of tropical summer and to establish physiological indices applicable to this environment in referring to this change. Environmental and physiological readings, milk and blood samples were taken at 15:00 h biweekly for totally five time points during the study. Climate readings showed that the afternoon humidex value reached the highest (53.5) around mid summer. Rectal temperature of cows taken simultaneously varied between 38.26degreesC and 40.02degreesC in parallel to humidex. Milk production declined drastically from 29.2 to 22.2 kg/d the first month entering summer but leveled up at end of the summer season suggesting effects exerted by heat stress rather than stages of lactation. Lactose content decreased linearly (p<0.05) with times in summer, from 4.69 to 4.38%. On the other hand, activity of N-acetylglucosaminidase (NAGase) in milk increased linearly to over two folds (p<0.05) during the same intervals. Elevations of fractional constituent of BSA in whey protein and serum cortisol level were also noticed in the course. Measurement of arteriovenous concentration (A-V) difference across the mammary gland demonstrated net uptake of glucose and net release of urea throughout the study period. The amount of urea released from mammary gland increased (p<0.05) progressively from 1.54 to 7.76 mg/dl during summer. It is concluded that gradual regression of mammary gland occurred along the humid tropical summer season. This regression is likely initiated through elevation of body temperature, which is irreversible above certain point. The increased release of urea from mammary gland during heat stress suggests its potential role as an early indicator of suboptimal mammary function.
ISSN: 1011-2367
Appears in Collections:動物科學系

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