Blood metabolite concentration, milk yield, resumption of ovarian activity and conception in grazing dual purpose cows supplemented with concentrate during the post-partum period

Cattle grazing on natural pasture face seasonal variation in pasture availability and nutritive value. Improving the nutrition of cows by providing supplementary feeds during periods of pasture or nutrient deficit is necessary for improved productivity. This study was conducted to determine the effect of feed supplementation during the post-partum period on the metabolic status and reproductive performance of 40 grazing Sanga and FriesianxSanga cows. Twenty out of a total of 40 cows (10 Sanga and 10 FriesianxSanga cows) were supplemented with 2.5kg of concentrate per day for 16weeks after calving. Parameters measured include daily milk yield, concentration of blood metabolites, resumption of ovarian activity and conception. Supplemented cows had higher partial milk yield than their non-supplemented counterparts (2.07 vs. 1.60kg/day; P<0.001). Sanga cows had lower milk yield than the FriesianxSanga crossbreds (1.61 vs. 2.05kg/day; P<0.01). Supplemented cows had higher mean total protein (86.7 vs. 81.3g/L; P=0.007) and globulin (53.0 vs. 47.7; P=0.014) concentrations than non-supplemented cows. Sanga cows had higher glucose (P=0.027), total protein (P<0.001) and globulin (P<0.001) but lower triglyceride (P=0.003) and progesterone (P=0.023) concentrations than FriesianxSanga cows. Supplemented cows had less proportion not cycling (20 vs. 55%; P=0.022) and less days open (95.8 vs. 106days; P=0.032) than non-supplemented cows. The FriesianxSanga cows had higher progesterone concentrations at first progesterone rise (3.34 vs. 1.32ng/mL; P=0.032) and shorter interval from calving to conception (96.7 vs. 106days; P=0.042). The results from this study indicate the beneficial effects of feed supplementation in terms of increased milk yield, better metabolic status and reproductive performance.