Authors : L. Alvarez and F. Galindo
Abstract: The objective of the present study was to determine the daily plasma cortisol pattern in domestic lactating and non-lactating goats. In a total of 12 multiparous goats (6 lactating, 6 non-lactating), 4 daily blood samples were taken over the course of 12 days, beginning at different times, in order to cover two, 24 h periods. Lactating goats were at their 4th month of lactation and were hand-milked daily at 07:30-08:30 h since parturition. Repeated measures ANOVA, Tukey-Kramer and student’s t-tests were used, considering diurnal (07:00-18:00 h) and nocturnal hours (19:00-06:00 h) as well as the condition of lactation. Higher levels of cortisol (45 nmol L 1) were found during diurnal hours, followed by important and sustained decreases (6-16 nmol L 1). A pair of smaller peaks appeared between 23:00-24:00 h, followed by a decrease that was maintained until 06:00 h, at which time high levels of cortisol returned (26 nmol L 1). Daily average cortisol values were similar between lactating (16.6�1.8) and nonlactating goats (16.5�1.8; nmol L 1; p>0.05). Diurnal cortisol was higher (p = 0.003) than nocturnal (19.6�1.9vs. 13.5�1.1 nmol L 1). Daily cortisol levels are similar between lactating and non-lactating domestic goats at their fourth month of lactation and cortisol levels undergo significant changes during the day, with higher concentrations in diurnal compared to nocturnal hours.
L. Alvarez and F. Galindo , 2008. Daily Cortisol Profile in Lactating and Non-Lactating Dairy Goats (Capra hircus). Research Journal of Animal Sciences, 2: 72-77.