Meal patterns of dairy cows consuming mixed foods with a high or a low ratio of concentrate to grass silage

With the aim of testing the effects of food quality on meal patterns 127213 visits by 22 lactating cows to 12 computerized feeders supplying two foods, high forage (HF) and high concentrate (HC) consisting of grass silage and concentrate were analysed. The foods were composed of the same ingredients but the proportion of concentrate dry matter (DM) in the food DM differed between HC (0.59) and HF (0.27). Each of the foods was offered ad libitum to 11 cows from the start of lactation until 156 (s.e. 9) days after calving. Mean daily fresh food intake (49.2 kg) was not affected by treatment. Mean daily intake of DM differed between HC (23.6 kg) and HF (17.8 kg). After estimating individual meal criteria, visits were grouped into meals. The mean daily number of meals was 6.6, the mean fresh food intake per meal was 7.6 kg and neither was affected by treatment. Cows consuming HF had longer meals (41.4 v. 31.3 min) but a lower feeding rate than cows consuming HC (233 v. 337 g of fresh food per min and 78 v. 156 g DM per min). Pre- and post-prandial correlation coefficients were sometimes statistically significant but always low (R2 from 0 to 0.05) and not affected by treatment. Food intake per hour of the feeding cycle (defined as the intake during a meal divided by length of the meal plus the duration of the preceding between-meal interval) showed a diurnal pattern in the shape of a sine-wave with low values of about 1.5 kg/h for cycles starting just after midnight and high values of more than 3.0 kg/h for cycles starting just after noon. Neither the mean, nor the amplitude, nor the shift of the sine-wave were affected by treatment. The data suggest that similar mechanisms are responsible for the short-term intake regulation of HC and HF. No evidence was found to suggest that the diurnal meal pattern of cows consuming HF deviated from that of cows consuming HC as a result of differences between foods in constraints related to their physical properties.