Association of rumination with milk yield of early, mid and late lactation dairy cows

Identification of the associations of cow feeding behaviour with milk yield (MY) is important for supporting recommendations of strategies that optimize MY. The objective of this study was to identify associations between measures of rumination time (RT) and MY using data collated from 2 777 dairy cows on nine commercial dairy farms during the years 2017 to 2019. A database contained behaviour and daily MY data. Cows averaged (mean ± standard deviation) 2.7 ± 1.6 lactations, 153 ± 81 days in milk, and 23.2 ± 7.5 kg/day of MY during the observation period. Behavioural data included RT (504 ± 93 min/day), feeding time (FT) (479 ± 110 min/day), resting time (360 ± 94 min/day), and activity time (96 ± 45 min/day). The coefficient of variation for RT (min/day) was 18.5%. The behavioural differences observed in this study provide a new insight into the effects of RT and FT on MY. MY was positively associated with RT in early and mid-lactation dairy cows with correlation coefficients of 0.24 (P < 0.001) and 0.25 (P < 0.001), respectively. The mean level of rumination time (MRT) was shown to be correlated with total MY produced over the whole lactation (305 days). The differences in MY between the highest and lowest MRT groups of cows were 1 735 kg, 2 617 kg and 1 941 kg in the first, second and third lactation, respectively. High-yielding dairy cows in early (≥ 23 kg/day) and mid (≥ 30 kg/day) lactation achieved the highest RT (522 ± 3.54 min/day and 507 ± 3.17 min/day, P < 0.05) and the highest FT (457 ± 4.69 min/day and 496 ± 4.00 min/day, P < 0.05), respectively. Cows in the highest MY groups also had the lowest activity and resting times during the most productive (early and mid) phases of lactation (P < 0.05), which is in agreement with our finding that more productive cows spend a greater proportion of their time feeding and ruminating.