EVALUATION OF OXIDATIVE STRESS IN DAIRY GOATS LACTATING NATURALLY OR BY HORMONAL INDUCTION

Abstract

The objective was to evaluate the oxidative stress (OS) and its association with performance and serum cortisol in dairy goats under induced (IL) and natural lactation (NL). Six goats programmed to be eliminated due to reproductive problems were IL as follows: a) days 1-7, estradiol plus progesterone; b) days 8-14, estradiol; c) days 18-20, flumetasone; d) every seven days bovine somatotropin; f) on day 21 milking began. Cortisol, antioxidant capacity and Glutathione Peroxidase activity (GHS-Px) were determined in serum. During the first two weeks in milk, NL goats had higher cortisol (P<0.05) and lower (P<0.0001) antioxidant capacity than NL goats (week1: NL= 3.5+1.2, IL= 14.4+1.1nM/ml; week2: NL= 9.7+0.8, IL= 34.4+0.7nM/ml) but groups did not differ in GHS-Px activity (P>0.05). Milk yield/day between groups (NL=2.54+0.2; IL= 2.12+0.2kg) and proportion of pregnant goats (NL=100%; IL=83.3%) were similar (P>0.05). The treatment was effective as inductor of lactation; besides most of the IL animals became pregnant despite their previous reproductive problems, prolonging their productive life with a natural lactation plus the additional benefit of at least one more kid. Because the antioxidant capacity increased and cortisol decreased in IL goats, apparently their welfare was more adequate than in NL animals.