Relationship between ewe body condition at mating and reproductive performance in the fat-tailed Barbarine breed

The relationship between reproduction performance in early May and ewe body weight (BW), body (or tail) condition score, the week before the rams were introduced into the flock, are presented for the Tunisian fat-tailed Barbarine breed grazing natural ranges in central Tunisia. During 2 contrasting years, 2 flocks (130 to 170 mature ewes each) differing by prolificacy (120%: Control and 160%: Prolific) and mature size (50 and 45 kg) were weighed and scored (according to 2 methods based on back fat thickness, BCS and on tail size, TCS), just before the introduction of rams. Rainfall during the pre-mating periods induced highly significant differences (P < 0.01) in animal body condition. In both flocks, fertility was equal to 75% and 92-96% for groups of ewes whose premating BW was respectively lower or higher than 35 kg. Similarly, the group composed by the 123 leanest ewes (less than 1.5 BCS) was significantly less fertile than the remainder of the flocks: 86% versus 91-95%. In both flocks, the higher the ewe BW, BCS or TCS at the beginning of the mating period, the earlier the lambing date and the higher the litter size. The first and the last lambing ewes (first 2 weeks and third month) weighed over 50 kg and only 35-40 kg, respectively, when rams were introduced into the flock. According to BW, BCS or TCS classes, litter size varied from 1.0 to 1.3 and from 1.2 to 1.8, respectively, in the C and P flocks. Target BW, BCS and TCS at mating to obtain early lambing and adequate litter size in Barbarine flocks can be proposed. According to ewe size, the following values: 39 or 50 kg for BW, 2.1 or 3.0 for BCS and TCS, mean values of the group of ewes lambing during the second month, can be considered as minimal for the whole flock. A second method, taking into account the within-flock animal variability can be used. The percentage of too emaciated ewes (less than 35 kg BW and back and/or tail condition score < 1.5) must be lower than 4 to 10% for BW, 6 to 8% for BCS and 10 to 15% for TCS.