Effect of using NRC and CSIRO tables on the performance of lactating ewes of Pelibuey and Katahdin breeds

Abstract

In the tropical sheep production sector, there is no technical consensus on which nutritional requirements tables, published by different international institutions, offer better productive performance when used as a reference for diet formulation by nutritionists. This research aims to determine which tool for calculating nutritional requirements in lactating, first-lambing ewes allows for better performance in maintaining the animal's weight at the end of the lactation period. The study was conducted at the Alfredo Volio Mata Experimental Station of the University of Costa Rica in 2019. Six adult females of the Pelibuey breed and six of the Katahdin breed in their first calving were evaluated. The animals were divided into two homogeneous groups based on the two breeds and were fed diets based on the nutritional requirements published by the National Research Council (NRC) and the Commonwealth Scientific and Industrial Research Organization (CSIRO), both in their 2007 versions. It was determined that there were significant differences (p<0.05) between the two treatments when analyzing the weight of the ewes at the beginning and end of lactation. Thus, the group of ewes of both Katahdin and Pelibuey breeds, whose diets were formulated according to the NRC model, finished with an average weight of 1.34 kg more at the end of lactation. The group of ewes of the same racial conformation whose diets were formulated according to the CSIRO model, finished their lactation with 180 g less on average. In conclusion, it was determined that there are differences in the performance and productive maintenance of ewes from both Pelibuey and Katahdin breeds using two different tools for the calculation of nutritional requirements.