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

Abstract

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 Friesian × Sanga cows. Twenty out of a total of 40 cows (10 Sanga and 10 Friesian × Sanga cows) were supplemented with 2.5 kg of concentrate per day for 16 weeks 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. 1.60 kg/day; P < 0.001). Sanga cows had lower milk yield than the Friesian × Sanga crossbreds (1.61 vs. 2.05 kg/day; P < 0.01). Supplemented cows had higher mean total protein (86.7 vs. 81.3 g/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 Friesian × Sanga cows. Supplemented cows had less proportion not cycling (20 vs. 55%; P = 0.022) and less days open (95.8 vs. 106 days; P = 0.032) than non-supplemented cows. The Friesian × Sanga cows had higher progesterone concentrations at first progesterone rise (3.34 vs. 1.32 ng/mL; P = 0.032) and shorter interval from calving to conception (96.7 vs. 106 days; 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.