• Asian-Australasian Journal of Animal Sciences
• /
• v.13 no.4
• /
• pp.440-445
• /
• 2000

Thirty lactating Javanese thin-tail ewes (12 ewes had been injected, prior to mating, with 700 IU pregnant mare serum gonadotropin, and 18 ewes with saline as a control) were used to evaluate the effect of superovulation on milk production during lactation and mammary chemical indices at the end of lactation. Thirteen ewes (9 control and 4 superovulated ewes) were fed at low and the other 17 ewes (9 control and 8 superovulated ewes) were fed at high quality ration. Superovulated ewes, either fed at low or high quality ration, had dramatically higher milk yields (57%). At the end of lactation, superovulated ewes had higher mammary dry fat-free tissue, mammary DNA concentration, total mammary DNA and RNA contents than nonsuperovulated ewes. Superovulation did not affect mammary RNA and collagen concentrations, and total collagen content. Ration quality did not significantly increase milk production during lactation and mammary chemical indices at the end of lactation. The observed increase in milk production in the superovulated ewes was probably due to the increased mammary secretory cell number and their synthetic activities during lactation as a result of the increased endogenous hormonal stimulation of mammary growth and development during pregnancy.

• Asian-Australasian Journal of Animal Sciences
• /
• v.11 no.6
• /
• pp.648-654
• /
• 1998

Twenty-four Javanese thin-tail ewes (11, 9, and 4 ewes giving birth to 1, 2, and 3 lambs, respectively) with similar body weight and age at breeding were used to study serum progesterone concentrations during pregnancy, milk production during lactation, and mammary gland indices at the end of lactation (3 months postpartum). The results of the experiment showed that averages serum progesterone concentrations during pregnancy in the ewes giving birth to twin and triplet lambs were higher (p < 0.01) than those giving birth to a single lamb. Ewes giving birth to 3 lambs had higher (p < 0.01) mammary dry fat-free tissue (DFFT) (by 31 and 34%), DNA concentration (by 25 and 16%) and RNA concentration (by 29 and 16%) at the end of lactation than those giving birth to 1 and 2 lambs. There was no difference in mammary collagen, protein and glycogen concentrations at the end of lactation among litter sizes. Ewes giving birth to 3 lambs had higher (p < 0.01) total mammary DNA content (by 64 and 61%) and RNA content (by 69 and 53%) at the end of lactation than those giving birth to 1 and 2 lambs. There was no difference in total mammary collagen, protein and glycogen contents at the end of lactation among litter sizes. Even though ewes with higher litter size had numerically higher milk production, there was no significant difference in milk production per 4 h among litter sizes. The results of the experiment indicated that ewes having higher litter size had greater mammary cell number and synthetic activities at the end of lactation. The results suggested that ewes with higher progesterone concentrations and better developed mammary glands during pregnancy could maintain higher cell number and activities throughout lactation.

• Asian-Australasian Journal of Animal Sciences
• /
• v.11 no.3
• /
• pp.300-306
• /
• 1998

An experiment was conducted to investigate correlations of litter size and average serum progesterone concentrations during pregnancy with mammary gland growth and development at parturition. Twenty ewes (5, 9, 4, and 2 ewes carrying 0, 1, 2, and 3 lambs, respectively) were used to measure weekly serum progesterone concentration during pregnancy. At parturition, the experimental ewes were slaughtered for determination of mammary gland growth and development at parturition (mammary dry fat-free tissue [DFFT], DNA, RNA, collagen, protein, and glycogen). Correlation of mammary DFFT with litter size and averages serum progesterone concentrations were 0.75 and 0.72, respectively. Litter size or maternal serum progesterone concentrations did not correlate with the mammary DNA concentration. However, litter size or maternal serum progesterone concentrations positively correlated (p < 0.01) with the mammary RNA and protein concentrations, but negatively correlated with the mammary collagen (p < 0.01) and. glycogen (p < 0.05) concentrations. Litter size or maternal serum progesterone positively correlated (p < 0.01) with the total mammary DNA, RNA, collagen, protein and glycogen contents. These results implied that the increased concentrations of progesterone with the increased litter size during pregnancy improved mammary gland growth and development at parturition.

• Asian-Australasian Journal of Animal Sciences
• /
• v.16 no.7
• /
• pp.988-995
• /
• 2003

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 $38.26^{\circ}C$ and $40.02^{\circ}C$ 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.

• Asian-Australasian Journal of Animal Sciences
• /
• v.24 no.4
• /
• pp.485-492
• /
• 2011

The influence of high temperature on mammary cell turnover during the dry period is still unclear. The objective of this study was to investigate mammary cell turnover and p53 protein expression in the mammary tissue under high temperature conditions. Mammary gland biopsy samples from 8 dairy cows were obtained at 7, 25, 40, and 53 d during the dry period in summer or spring (n = 4, each season). Cell cycle, cell turnover, and p53 protein expression were analyzed by flow cytometry. During the dry period in summer, the percentage of mammary epithelial cells in the G0/G1 phase was the highest, but those in the S and G2/M phases were lower. However, the proportion of cells in the different stages of the cell cycle was not significantly different among the different biopsy time points, except in the G2/M phase. Under different temperature conditions, the cells were significantly different in their apoptotic rate and proliferation index; moreover, the tendencies of these indicators to change significantly differed. In general, the samples under high temperature conditions showed significantly lower apoptotic rates and proliferation indices. Under high temperature conditions, the apoptotic rate and proliferation index were the lowest (2.17% and 3.26%, respectively) at day 40, and the highest at day 53 (3.67% and 4.61%, respectively). However, under normal temperature conditions, the values of these indicators were the lowest (7.60% and 5.54%, respectively) at day 7, and almost the highest at day 25 (12.85% and 6.47%, respectively). Moreover, p53 protein expression was significantly higher under high temperature conditions than under normal temperature conditions, except at day 25. The level of p53 protein was the lowest (13.10%) under high temperature conditions at day 25, but was the highest (26.07%) under normal temperature conditions. Our findings suggest that high temperature delayed the G2/M phase of the cell cycle and the cell turnover rate, but remarkably increased p53 protein expression. Thus, the results indicate that high temperature extends the recovery period of mammary epithelial cells.