CHARACTERIZATION OF ANIMAL GENETIC RESOURCE IN THE DESIGN OF SUSTAINABLE CATTLE PRODUCTION SYSTEMS IN THE TROPICS

Abstract

With the objective to characterize and to identify the level of harmony between animal genetic and feed resources available in commercial dual purpose cattle production systems in Southeast Mexico, cow productivity and apparent energetic efficiency (EEA) of low, medium and high European grade (GG) managed under direct grazing with and without supplementation (NN) were estimated. First, 316 cows and 254 calves in nine herds grouped in four nutritional levels (temporal direct grazing with or without supplementation and irrigated and fertilized grazing with either five or seven kg of commercial concentrate per cow a day) were used; and second, 63 cows in two herds, one with direct grazing and the second with supplementation with dehydrated poultry excreta mixed with sugar cane during the dry season. Effects of GG, NN and their interaction and other environmental factors on productive traits were estimated by using the procedure of generalized least squares; and EEA through the ratio of energetic equivalents (Mcal ME) of saleable milk production, calf weaning weight per calved cow, cow body condition change during lactation and metabolizable energy consumed per cow during 240 days. The effects of GG and NN were significant for PL, WW and CCC (P<0.001). ME retained in the products and the energetic balance was similar between cows managed either with or without supplementation and the EEA was 17% higher when supplementation was used. In relation to GG, the ME retained and contained in the products were higher in medium compared to low and high European grade cows (P<0.05) and EEA were 78 and 86% compared to low and high cow GG, respectively. Medium graded cows were both more productive and more efficient in the use of energy available in grass and supplements used. The increment of EEA was higher when medium grade cows were used than the use of supplements during the dry season, and allowed better use of feed resources and the sustainability of the system.