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

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 x 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.