Abstract
The objective of this work was to study the relationships between different body reserve (BR) dynamic profiles and ewe rearing performance (PERF) traits in a Romane meat sheep population extensively managed in a rangeland of France. Genetic parameters that link litter weight and lamb BW at lambing and weaning, lamb growth rate at 1, 2 and 3 months after lambing and litter survival from lambing to weaning to different BR profiles that have previously been demonstrated in the same animals are reported. Records from the flock of the INRA La Fage experimental farm were used to generate datasets from 14 lambing years (YR: 2002 to 2015). The datasets involved 1,146, 1,072 and 414 females belonging to 3 parities (PAR: 1, 2 and 3, respectively), with first lambing at 2 ages (AGE: 1 or 2-yr-old), and 4 litter sizes (LS: 1, 2, 3 and 4 lambs born alive). Significant effects on PERF were observed on all fixed variables considered (i.e., YR, AGE, PAR and LS). Similarly, the BW and BCS profiles of the ewes were strongly related to the PERFs across the 3 PARs studied, particularly for the BW profiles in the first cycle (PAR 1). In contrast to litter survival, which showed very low h² values and repeatabilities, the traits of lamb BW at lambing and weaning and litter weights at weaning had moderate h² values ranging from 0.20 to 0.23 and repeatabilities ranging from 0.21 to 0.27. In conclusion, our results show that genetic gains may be possible due to the inclusion of combined BR and PERF traits in sheep selection programs for this breed and warrant further research in other sheep populations.