EFFICIENCIES OF GENETIC EVALUATION METHODS OF LAMB GROWTH UNDER LOW INPUT PRODUCTION SYSTEMS AND MONITORING OF GENETIC TRENDS

The lack of coherent breeding strategies has been a limiting factor to improve small ruminants. The objectives of this study were: 1) to compare a set of genetic evaluation methods and 2) evaluate the realized genetic progress across flocks. Growth data of 1166 Barbarine lambs with pedigree information recorded during 2009-2014 in five pedigree connected flocks were used in this study. Eight methods of breeding values estimation and prediction were ranged in three classes and compared. Class (1) is a simple deviation of a given lamb W70 from the flock average with no weight adjustments. Class (2) is a Best Linear Predictor (BLP) using adjusted W70 with an estimated heritability of 0.20 and Class (3) included four Best Linear Unbiased Predictor (BLUP) models. The 7th model was a BLUP animal model used for ADG30-70 and the 8th one was a Global Index combining breeding values of W70 and ADG30-70. Main results showed that A Barbarine lamb weighs 16.13±3.31 kg at 70d of age. Rank correlations showed high values among all BLUP models (>=0.98) and lower values between BLUP models and the deviation from flock average or even BLP Index ranging from 0.62 to 0.70 and translating that ranking of lambs based on deviation from flock average or a simple BLP Index was not as accurate as BLUP rankings. These results should a raise awarness of the potential of the use of accurate genetic given evaluation tools on their efficiency in predicting breeding values. Genetic progress was stagnating showing the need to use accurate methods.