Supplementation levels for non-lactating cows grazing during the rainy season

Abstract

This study aimed to evaluate levels of concentrate supplementation (1.5, 3.0, 4.5 and 6.0 kg day?1) for grazing dairy cows kept on Panicum maximum Jacq. cv. Tanzania pasture during the rainy season on nutrient intake and digestibility and rumen parameters. Four rumen cannulated non-lactating Holstein × Zebu crossbred cows were used in this study by a 4X4 Latin square design, which presented an average initial body weight of 521.69±31.98 kg. Each period lasted 17 days, being the first 10 days were used for animal adaptation and the remaining seven days for data collection. There was no effect (P > 0.05) of supplementation levels on total dry matter intake, although forage dry matter intake has been linearly decreased (P < 0.05). Treatments have no effect (P > 0.05) on the digestibility coefficients of dry matter, organic matter, crude protein, or ether extract. There was a linear increase (P < 0.05) on daily rumination time and total rumination times according to supplementation levels. There was no significant effect of supplementation levels (P > 0.05) or time after supplementation on rumen pH. Rumen ammonia nitrogen concentration responded quadratically (P < 0.05) to times after supplementation, with a maximum estimated concentration of 17.61 mg dL?1 at 3.87 h after supplementation. Increasing supplementation levels for grazing dairy cows reduces forage intake but has no negative effects on total dry matter intake or rumen-fluid pH.