Grazing systems for Iactating dairy cows

Ernesto Jahn B.1, Hugo Vyhmeister B.1, Agustín Vidal V.2, Walter Bonilla E.1 y Pablo Millas A.3

Two systems were compared, in two experiments, in central south Chile. Cows were assigned to the following treatments:
A. Cows managed in one group, in a rotational grazing system.
B. Cows managed in two groups: the higher production half as first grazers (Bi) and the other half grazing the remaining grass (B2).
A predominantly ryegrass (LoIiurn perenne) white dover (Trifolium repens) irrigated pasture was used; in the different paddocks, age ranged from 1 to 8 years. In Trial 1, 38 cows were assigned, in a randomized block design, to each treatment, and in Trial 2, 16 replications were used. Milk production in Trial 1 was 12.4 and 12.7 kg/day, for treatments A and 8, respectively, and in Trial 2, 12.6 and 12.9 kg/day, for the same treatments, respectively. These differences were not significant (P >0,05). Cows grazed selectively, prefering leumes over grasses. Chemical composition of the pasture varied between seasons. Small differences were observed in composition of the forage offered to groups Bi vs. B2, which could explain the small differences in animal production.

1 Estación Experimental Quilamapu (INIA), Casilla 426, Chillán, Chile.
2 Subestación Experimental Humán (INIA), Casilla 767, Los Angeles, Chile.
3 Av. Argentina s/n, Casa 53, Población IANSA. Chillán, Chile.