Evaluation of fattening performances and carcass characteristics of purebred, first and second cross lambs between Moroccan Timahdite, D'man and improved meat rams

Fattening performance and carcass characteristics were evaluated in 202 lam bs sired by D'man (D), Timahdite (T) and terminal sires of the Ile-de-Franc e (IF), Lacaune (L), and Merinos Precoce (MP) breeds. Previous results had suggested that the three latter improved breeds had relatively similar grow th and carcass performance in crossbreeding. They were, therefore, pooled i n this study into one meat group breed (M) to facilitate comparisons betwee n the five genotypes of interest: two purebreds (T, D), two single crosses (D x T (DT), M x T), and one three-breed cross (M x DT). Results showed imp ortant improvements of performance in crossbred lambs especially those sire d by meat breed rams. M x T and M x DT lambs grew fastest (238 and 256 g/da y, respectively) and showed the best food conversion ratio. D purebred lamb s realized the lowest fattening gains (196 g/day) while, T and D x T lambs were intermediate (209 and 218 g/day, respectively). The D lambs deposited relatively more internal fat and relatively less subcutaneous backfat, and their carcasses had the lowest conformation score and smallest longissimus muscle area (11.23 cm(2)). The carcasses of M x T and M x DT crossbred lamb s had larger longissimus muscle areas 13.97 and 13.88 cm(2), respectively, thicker subcutaneous fat cover and better conformation scores than other ge notypes. The effects of M as a terminal sire breed were favourable for the majority of fattening and carcass characteristics. The absence of differenc es between M x T and M x DT genotypes on post-weaning growth, food conversi on ratio and on objective and subjective measurements of carcass conformati on indicated that the infusion of 25% of D genes in M x DT lambs did not af fect post-weaning growth and carcass traits. The results on the use of M si res and DT dams, which have above average reproductive rates, in M x DT cro ssbreeding indicate that a two-stage crossbreeding system could enhance the quantity and the quality of meat sheep production in Morocco.