The effect of the spring management system on blood metabolites and luteal function of ewes on Mediterranean mountain areas

Forty-eight adult ewes rearing single lambs were assigned to four management systems with the aim of comparing their productive, metabolic and luteal function response within the anoestrus season: (1) Indoor ewes (IND): Ewes and lambs permanently indoors. Dams fed a total dry mixed ration (forage to concentrate ratio 40:60). (2) Indoor plus rationed grazing ewes (IND-GR): Ewes stocked 8 h daily outdoors and receiving a supplement of barley meal indoors. Lambs from IND and IND-GR were weaned at 6 weeks old and fed concentrates ad libitum whereas their dams were stocked continuously on grassland until late spring. (3) Grazing plus supplement for lambs (GR + S): Ewes and lambs continuously stocked on grassland. Lambs received concentrate ad libitum and suckled their mothers until slaughter. (4) Grazing (GR): The same management as GR + S, but lambs did not receive any concentrate.The average daily gain of ewes throughout the rearing period was higher in IND, GR + S and GR than in IND-GR (P < 0.05). By contrast, on the whole 3 months post-partum ewes managed in confinement during lactation (IND) showed a slight daily loss of live-weight while the rest of the groups displayed gains (P < 0.05). Energy-corrected milk yield during 6 weeks post-partum was higher in IND and GR + S (P < 0.05). The mean plasma triglycerides during 3 months post-partum was higher in IND and GR (P < 0.05). Plasma NEFA were greater whereas plasma urea was lower in IND and IND-GR on weeks 3 and 5 of lactation (P < 0.05). After weaning of indoor treatments (IND and IND-GR), plasma urea was rebalanced in these groups until values close to continuous stocked treatments (GR + S and GR). The proportion of ewes resuming their first luteal phase within spring (nearly 45%) was similar across treatments (P > 0.05). In conclusion, the divergent post-partum metabolic status of ewes managed under grass-based compared to concentrate-based systems during the spring season did not carry over significant effects on their post-partum luteal function.