Rumen function and foraging behaviour of non-lactating, pregnant dairy cows wintered on kale or grass

Abstract

An outdoor grazing study conducted with 45 non-lactating, pregnant dairy cows during winter measured dry matter (DM) intake, grazing behaviour, rumen pH, ammonia (NH₃) and volatile fatty acids (VFAs) of cows fed 11 (K11) or 14 (K14) kg of kale DM/cow/day or 11 (G11) kg DM Italian ryegrass/cow/day. Cows in K14 spent more time grazing (441 min/day) than in K11 (9378 min/day) and G11 (326 min/day). Rumen ammonia concentrations ranged from 108 to 212 mg NH₃/L for K14, 91 to 306 mg NH₃/L for K11 and 57 to 269 mg NH₃/L for G11. Total VFAs concentration (mmol/L) was greatest for K14 (104), intermediate at G11 (96.7) and lowest for K11 (75.4). Rumen pH fell to reach its lowest values of 5.7 for G11, 6.2 for K11 and 6.1 for K14. Hence, there was little evidence of sub-acute rumen acidosis in kale-fed cows.