LAUSR

Abstract A total number of 23,271 parturitions were studied from two sheep farms of the Churra (CH) and Lacaune (LA) breeds. CH lambs were kept with their mothers during the first 30 days of age; from that moment onwards, ewes were machine-milked. LA lambs were not allowed to suckle their mothers, and ewes were machine-milked from parturition. Milking length (ML), total milk yield (TMY) and daily milk yield (DMY) (TMY/ML) were calculated. For the CH breed, there was an effect (p < .001) of prolificacy on ML, TMY and DMY and of offspring gender on TMY and DMY. For the LA breed, prolificacy and offspring gender had an effect (p < .001) on ML, TMY and DMY. Ewes giving birth to twin lambs produced more milk (CH: +0.15 l/d and +27.5 l/ewe; LA: +0.15 l/d and +11 l/ewe), than ewes giving birth to single lambs. For single parturitions in the CH breed, ewes giving birth to females produced more milk (+0.04 l/d and +5.2 l/ewe) (p < .0001) than ewes giving birth to males. In this breed, this effect of female offspring on milk production was similar for those ewes giving birth to twin lambs. In conclusion, ewes presenting twin parturitions produced more milk than single parturitions and the presence of female lambs had a positive effect on milk yield. These results open new possibilities to increase profitability of dairy sheep farms through a selection of the offspring gender.