Milk production, milk composition, rate of milking and grazing behaviour of dairy cows grazing two tropical grass pastures under a leader and follower system

Abstract

Milk production, milk composition, rate of milking and grazing behaviour were measured for lactating Jersey cows having both the first opportunity to graze (leaders) and also when offered the remaining herbage (followers) from 3-week regrowths of two nitrogen-fertilized tropical pastures, Rhodes grass (Choris gayana cv. Pioneer) and Gatton panic (Panicum maximum cv. Gatton). Twenty-four cows were used in a latin-square design with experimental periods of 14 days. Both leaders and followers were allocated 40 kg DM cow-1 day-1. Leader cows produced 8.0 kg milk cow-1 day-1 compared with 5.8 kg milk cow-1 day-1 for followers, a difference of 38 per cent. Both leader and follower cows grazing Gatton panic produced more milk than cows grazing Rhodes grass. Milk from leader cows contained a higher percentage of solids-not-fat and protein and a lower butterfat percentage indicating a higher intake of digestible nutrients. Cows showed a preference for leaf, and after easily accessible leaf was removed by leader cows the follower cows had a small bite size. Follower cows partially compensated by increasing grazing time, mainly at night. Follower cows had a longer let-down time and a longer milking time per kilogram of milk produced. Milk production was linearly related to bite size and availability and accessibility of leaf were considered to be the main factors influencing production.