Med. Weter. 74 (8), 540-543, 2018

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Influence of SRLV infections in sheep flocks on growth and reproductive performance
The aim of the study was to determine the influence of the occurrence of SRLV infections on lamb growth and reproductive performance of sheep. The study was carried out on 98 sheep flocks from mid-Eastern Poland, covering the area of Lubelskie, Świętokrzyskie and Podkarpackie provinces. The study included 6,470 mother ewes. Flocks with at least one detected case of SRLV-positive serological test were considered infected. All flocks included in the experiment were subjected to the analysis of lamb growth on the basis of their body weight achieved on the 56th day of life. Moreover, traits related to reproductive performance, such as fertility, lamb/ewe rate and lamb weaning rate, as well as the reproductive performance itself were evaluated. The observations showed that both ewes (18.98 kg) and rams (19.70 kg) achieved higher body weights in the flocks where SRLV had not been detected. In the flocks in which the presence of SRLV was detected the achieved body weight was lower by 0.93 kg and 1.26 kg, respectively. The sheep in the SRLV-infected flocks were characterized by a significantly lower fertility and higher lamb/ewe rate in comparison to other flocks. The analysis conducted for the purpose of the study showed that the presence of SRLV in a flock resulted in a worse lamb weaning rate by about 6.69 percentage points. To sum up, the flocks with detected presence of SRLV were characterized by a significantly lower fertility and greater lamb mortality rate. The presence of SLRV also had a detrimental effect on the body weight obtained on the 56th day of life, both in rams and ewes. The results of the study clearly indicate the negative influence of SRLV on the reproductive performance of sheep..
Key words: sheep, SRLV, growth, reproductive