Simplification of the growth recording protocol for meat sheep applied in Morocco

The study aimed to simplify the actual sheep weight recording protocol used in Morocco that is based on weighing lambs at four different intervals of 21 days. The study was simulated using the weights of 1554 Timahdite lambs, born between 2008 and 2012 in four state farms. Nine simplified protocols were applied,,based on constant birth weight for all lambs or according to their type of birth and sex and number of weighings to be carried out. Comparison between the standard weights at 30, 70 and 90 days, calculated using the actual and simplified protocols, was based on the average bias, mean squared error and accuracy loss. Moreover, direct and maternal heritability estimates of the standard weights, calculated using the actual and simplified protocols, were compared. Similarly, the Spearman correlation coefficients between sheep rankings on the direct genetic indexes and correlation coefficients between sheep rankings on the maternal genetic indexes for weight at 30, 70 and 90 days, estimated using the actual protocol and each of the simplified protocols, were calculated. Based on these criteria, the closest standard weights’ estimation to those of the actual protocol was performed using protocols based on constant birth weight for all lambs or according to their type of birth and sex, and two controls at 42 and 84 days or three controls at 42, 63 and 84 days, with only lambs more than 21 days old being weighed at each control. It was concluded that ignoring one or two controls out of the four currently practiced would not alter the shape of the lambs' growth curve and would allow standard weights to be estimated without much loss of accuracy.