Factors Affecting The Lactation Curve Parameters of Crossbred Dairy Ewes In The Highlands of Mexico

Abstract Sheep milk production is incipient in Mexico with scarce knowledge on the performance of dairy ewes from different breeds. The objective was to evaluate the effect of breed (Awassi (Aw), East Friesian (EF) and other (Ot)), parity number 1, 2 and 3 or more (+3), litter size 1 and 2 or more (+2), and lambing season Spring-Summer (SS) and Autumn-Winter (AW) on day to peak milk yield (DP), peak yield (PY), persistency (P), total milk yield (TMY), 305-day milk yield (TMY305d), 150-day milk yield (TMY150d) and lactation length (LL) of crossbred dairy ewes in an intensive confined system in the central highlands of Mexico. A total of 4,312 weekly milk yield records collected from 2014 to 2015 were used to model 133 lactations using a random regression model with a 5th order orthogonal polynomial. Flock mean values of curve parameters were 42 days at DP, 1.2 kg/day at PY, -3.5 g/day of P, 190 kg TMY, 189 kg TMY305, 124 kg TMY150 and 269 days of LL. Multiparous ewes had significantly higher (P<0.05) PY and TMY than primiparous ewes. Ewes that lambed in AW had 15% higher PY and produced 14% more TMY than ewes that lambed in SS (P<0.05). Correlations among curve parameters were significant except for PY with LL, and P with TMY150d. TMY was strongly correlated with LL (0.91). It is concluded that second parity ewes lambing in AW season resulted in higher TMY. Predominantly, Awassi crossbred ewes had lower curve parameter values than predominantly East Friesian and other crossbred ewes.