Milk performance of two cow breeds at two levels of supplementation in long residence time grazing paddocks

摘要

Milk performance of four groups of cows (HO, H4, NO and N4) was studied under grazing: two cow breeds, Holstein-Friesian (H) vs. Normande (N), supplemented at pasture with two levels of concentrate, low vs. high (0 and 4 kg cow~(-1) day~(-1)). A simplified rotational grazing system using three paddocks per rotation with a mean residence time per paddock of 10-days was examined. During this long residence time, maximum milk yield (MY max.) was reached at day 4 followed by a milk yield drop (Dm) at theend. Milk production was higher (P < 0.001) in Holstein-Friesian than in Normande cows (7,452 over 6,067 kg cow~(-1) year~(-1)). Supplemented cows produced more (P < 0.001) milk than unsupplemented cows (7,570 over 5,949 kg cow~(-1) year~(-1)). In each10-day grazing cycle, supplemented cows had higher (P < 0.001) peak (MY max., 25.6 kg cow~(-1)) and less (P < 0.001) drop (Dm - 5.3 kg cow~(-1)) than those without concentrate (21.2 and - 5.7 kg cow~(-1)). The peaks and drops of milk yield were higher (P< 0.001) in Holstein-Friesian (25.5 and - 6.2 kg cow~(-1)) than in Normande cows (21.3 and - 4.7 kg cow~(-1)). When long-residence grazing paddocks are used, these peaks and drops of milk yield are important factors to control for a good milk performance considering both the cow breeds and the supplementation effects.