Diurnal Variations in Milk Amino Acid Concentrations in the Horse

Abstract

In a preliminary study of the effects of diet on the amino acid concentrations in mare’s milk, the diurnal variations in the milk amino acid concentrations were investigated. In this study, the milk amino acid concentrations were measured every 2 hr during a day (00:00, 02:00, 04:00, 06:00, 08:00, 10:00, 12:00, 14:00, 16:00, 18:00, 20:00 and 22:00 hr) in two lactating brood mares. It was found that the ratio of the difference between the maximum and minimum concentrations to the averaged value was 20% or more for all the amino acids, although no statistically significant influence of the sampling time on the amino acid concentrations was observed. The value at each sampling time was in most cases not within the confidence interval (95%) to the mean population of 12 sampling times in a day. On the other hand, the values averaged at three time points, at intervals of 8 hr (04:00, 12:00 and 20:00 hr, or 6:00, 14:00 and 22:00 hr) were within the confidence interval (95%) to that. Therefore, when investigating the milk amino acid concentrations in mares, it is important to conduct measurements in milk samples obtained at several different time-points in the day.