Study on the milk yield and lactation persistency of F4 crosses between Pleven blackhead sheep and the Assaf sheep during different lambing seasons

Zornitsa Petkova and Vasil Nikolov

Abstract: The milk yield and lactation persistency of 85 F4 crosses between Pleven blackhead sheep and the Assaf sheep breed were studied based on the performance of 932 controls. It was ascertained that under the conditions of intense production system- a year-round barn breeding and standardized, good quality feeding, the average 180-day-period daily milk yield upon first lactation was 1.584±0.028 kg, and for a 300-day period it was 1.500±0.027 kg. Up to 180th lactation day, the percentage of ewes milked was 82,4, and up to day 300 – 55.3%. No reliable differences in the milk yield (P > 0.05) were ascertained upon lambing during 4 periods- March, July, August and September which serves to prove that the cross-breeds may be successfully used for a year-round milk production. The lactation persistency was reliably influenced (P < 0.001) by the month of lambing. The lactation peak was reached at the end of the first month post lambing (2.024 kg/d), the milk yield was retained until the end of the second month (97.6% of the maximum) and after that it gradually decreased reaching 63.2% on day 120 and 51.9% of the maximum on day 180. The most stable lactation is reported for the sheep which lambed in the spring- it started at the lowest level of 1.541 kg/d (on day 15 after lambing), reached the peak of 2.112 kg/d at the end of the second month and as of the latter period until the 120th lactation day, it remained higher when compared with that of the other groups. The sheep which lambed in July exhibited the highest dynamics – their lactation started at the highest level (2.442 kg/d), reached its maximum (2.563 kg/d) but until the middle of the second month, the milk yield sharply decreased (1.734 kg/d) and after that it maintained the level of the other groups. The sheep which lambed in August and September had milk yield of respectively 1.723 kg/d and 1.910 kg/d during the first control, the peak was registered at the third control (45th day) and was respectively 2.126 kg/d and 2.110 kg/d for the two months.

Keywords: Assaf crosses; dairy sheep; intensive system; lactation curve; milk yield; Pleven blackhead sheep

Date published: 2022-11-01