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This study was conducted to determine whether carotenoid pigments can act as biomarkers of grass feeding to trace lamb production systems. Three production systems were compared: G = grazing (72 lambs), S = stall-feeding (26 lambs), and GS = grazing period followed by a stall-feeding period (27 lambs). Presence of carotenoids in tissues was evaluated by plasma concentration and reflectance spectrum of subcutaneous caudal adipose tissue. Plasma carotenoid content was measured during the grazing period for G and GS lambs, at the end of the grazing period for GS lambs and at slaughter for G, S and GS lambs. Reflectance spectrum of adipose tissue was measured at slaughter for 38 G and 26 S lambs. We collected 135 G and 26 S blood samples. Carotenoids were detected in 97% of the G blood samples, whereas they were not detected in 93% of the S blood samples. Plasma carotenoid content of all the GS lambs decreased during the stall-feeding period. Mean reflectance spectra of adipose tissue of G and S lambs differed between 450 and 510 nm, which corresponds to light absorption by carotenoids. We performed a mathematical analysis of the spectrum in order to quantify absorbance in this zone and to propose an index that can be used in the meat industry to trace animal production systems. This method was less discriminating than plasma carotenoid analysis, as there was some overlapping in the frequency distribution of the traceability index for G and S lambs that concerned 19% of the lambs. Sensitivity of the two methods to bias and applicability to cattle are discussed.

-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.

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(-3.5 units) than in sheep. In contrast, digestibility in camelids was higher (3-4 units). Finally, the digestibility of different forages in horses was markedly lower than in sheep (-2-3 units for legumes, -4 units for grass hays and -8 units for straw). In conclusion to this review, 2 important findings can be underlined: (i) the digestibility differences between herbivores are more evident for low quality forages with high cell-wall contents; and (ii) the total OM digestion is generally related to live-weight and nutritional requirements are proportional to LIN!.!S , and so herbivores can more easily adjust their requirements when their body weight is increased. intake / digestibility l ovines / goats / bovines / deers / camelids / horses

Dairy ewes (Prealpes breed) were subjected to differential photoperiod treatments: either long (15·5 light (L): 8·5 dark (D) or short (8·5 L: 15·5 D). Treatments started 15 days before lambing and continued until the 5th week of lactation. After lambing the 22 ewes of each photoperiodic treatment were divided in two groups and fed on either a high or low plane (19 v. 10·5 MJ/day and 370 v. 237 g crude protein per day). Milk yield was not affected by photoperiod but significantly modified by feeding levels (1154 v. 789 ml/day). Protein content of the milk was reduced under long days (—4·9 g/1) compared with short days, while no effect was observed for fat content. Body chemical composition changes, estimated by the deuterium oxide (heavy water) dilution technique between weeks 1 and 4, were affected by both treatments, with a significant interaction between photoperiod and diet for body protein changes: under short days lipid and protein changes were closely related while under long days they were independent.Blood samples were taken on day 23 of lactation from six ewes per group, every 30 min from 07.30 to 15.30 h for growth hormone (GH) and prolactin (PRL) measurements. The timing of GH and PRL pulses were different, but there was evidence that secretory patterns of each hormone were synchronized across ewes within the four treatments. Long photoperiod increased plasma PRL baseline rather than pulse amplitude, with no effect of diet. Undernutrition mainly increased GH pulse amplitude rather than baseline concentration, with no significant effects of photoperiod.High spontaneous concentrations of GH were associated with body lipid mobilization (R2 = 0·51) and were also involved in the control of protein changes (R2 = 0·71). These results indicate that GH (and PRL) are involved in nutrient partitioning in the lactating ewe.

RésuméAu cours des 6 dernières semaines de la gestation et des 5 premières de la lactation, 40