Changes in milk yield, fat and protein mass fractions in mares' milk within 24 hours

During the day protein mass fraction and fat mass fraction in mares' milk changes in different ways. The variability of fat content in mare's milk reaches 60% within 24 hours. Several experiments, including the milking of mares continuously during the day, were conducted to explain the nature of this phenomenon. Differences in the variability of fat and protein contents in the mares' milk during the day and various way of secretion of the milk components from udder's secretory cells were explained by the authors in this scientific article. The protein is secreted due to merocrine secretion, and fat secretion mainly occurs due to apocrine secretion. Reduction of fat content in the mares' milk is caused by the significant increase of milk yield in the early morning, when secretion of synthesized fat slows down. When milk yield is reduced, the secretion of stored fat is increased, which also increases the fat content in milk. It was found that in the morning milk yield of mares is higher than at night by 16.39 %. It was also found that during the day protein mass fraction is higher than it is at night by 5.24 %. The fat content in the mares' milk during the day is higher than it is at night by 12.24 %. The ratio of daily milk yield and fat content was amounted to 0.22, of daily milk yield and protein mass fraction was + 0.44, and of fat mass fraction and protein mass fraction was + 0.47.