Resumen

URBANO, Diannelis; DAVILA, Ciro  y  MORENO, Pedro. Effect of tree legumes and commercial feed supplementation on milk production and weight changes in double purpose cows. Zootecnia Trop. [online]. 2006, vol.24, n.1, pp.69-83. ISSN 0798-7269.

A grazing trial was conducted for 22 weeks in the University of the Andes farm located in El Vigía, Mérida state, Venezuela, to evaluate legume tree association (Leucaena leucocephala and Gliricidia sepium) with grasses of the Brachiaria genus and four combinations of two protein level contents and two milk/concentrate proportions on the milk production and weight changes of double purpose cows. A completely randomized design with 8 treatment and 5 replications was used; treatments were the combinations of grazing systems (with and without legume trees), amount of concentrate (5:1 and 3:1) and protein content (16 and 21% protein). Forty double purpose cows, at the beginning of lactation, were randomly assigned to treatments. Milk production was recorded daily and weight changes monthly. Significant effect of the protein content x milk concentrate proportion and protein content x pasture system interactions were detected, while differences due to the main effects were not detected. Average milk production for the associated legumes treatment was 8.96 L/cow/day, and for the grasses was 8.21 L/cow/day, but productivity was 13,343 and 5,244 L/ha/year for associations and the traditional grass system, respectively. Concentrate proportion and crude protein did not affect milk production average, but in the combination of low relation milk concentrate (5:1) with low protein content (16%), cows decreased milk production only in the intensive grazed legume grass system. Weight changes were not significantly affected by treatments. The contribution of the tree legume to the high milk production per unit of land on pasture was more influenced by the carring capacity than by cow increment of production.

Palabras clave : Leucaena leucocephala; Gliricidia sepium; associations; concentrate; milk production; weight change.