Resumen

MAQUIVAR-LINFOOT, Martín Guillermo et al. Prediction of the Daily Weight Gain by the Use of the NRC Model in Supplemented Heifers in the Humid Tropics of Costa Rica. Rev. Cient. (Maracaibo) [online]. 2006, vol.16, n.6, pp.634-641. ISSN 0798-2259.

The aim of this study was to evaluate the model NRC level 1 to predict the daily weight gain in heifers supplemented under tropical conditions. For this purpose, two experiments were done, in the first experiment 30 heifers were divided into two groups of fifteen animals each, the supplemented group (GS) showed an initial weight of 365.27 ± 24.40 kg, received commercial concentrate to the ratio of 1% of live weight (5.5% PC 2.85 Mcal ED) and the control group which was not supplemented (GNS) with an initial weight of 367.47 ± 31.65 kg. In the second study 45 heifers were divided in two groups, the GSb with 22 animals having an initial weight of 342.23 ± 36.4 kg and given concentrate to the rate of 1% of live weight (13% PC 3.5 Mcal ED) and the GNSb were made up of 23 animals having an initial average weight of 326.0 ± 31.3 kg. In both trials the animals were supplemented throughout for forty-five days and let them grazed on African Star grass (Cynodon nlemfuensis), Candelario grass (Pennisteum purpureum) and Ratana grass (Ischaemum indicum). In both experiments no differences were observed (P > 0.05) in weight change .The GS had daily weight gains (GDP) of 0.27 kg/d while the GNS showed losses of -0.05 kg/d. In the second trial the GSb showed a GDP of 0.90 kg/d and the GNSb of 0.60 kg/d. The predicted GDP of the first experiment was similar in comparison with the observed value for the supplemented group (P > 0.05), in contrast with that presented in the GNS group in which the daily weight gain was over estimated (P < 0.05). In the second trial the GDP predicted for both groups was under estimated (P < 0.05). The level 1 of the NRC simulation model does not seem to be appropriate for predicting changes in weight in heifers under tropical conditions

Palabras clave : Bos indicus; NRC; simulation; supplement; grazing.