Administration of a long-acting antiparasitic to pre-pubertal ewe-lambs in Greece results in earlier reproductive activity and improved reproductive performance

Abstract

We studied the reproductive effects of administration of a long-acting antiparasitic (moxidectin) given to pre-pubertal ewe-lambs in Greece at the beginning of the reproductive season. 45 animals, naturally infected with trichostrongylids, were allocated into treated (n=30, treatment on D0, 21 June) or control (n=15) group. Rams of confirmed fertility, were introduced from 15 August (D55) to 20 December (D182) into the ewe-lambs. Throughout the study (performed at latitude N 36°26', in a flock free from brucellosis, Chlamydophila infection and toxoplasmosis), epg counts were monitored and reproductive performance of ewes was assessed. Up to D112, arithmetic mean epg counts in treated animals were 0; thereafter and up to D350, they were 23-473. Respective figures for controls were 190-977 epg. Reproductive performance parameters for treated and control animals respectively, were as follows; median 'Interval to first mating after ram introduction': 36.5 d and 71.0 (P=0.04); median 'Age at first mating': 8.5m and 10.0m (P=0.045); 'Cycling rate': 20.0% and 6.7% (P=0.03); 'Mating rate': 86.7% and 66.7%; 'Return-to-oestrus rate': 26.7% and 26.7%; 'Abortion rate': 3.3% and 0%; 'Lambing rate': 83.3% and 66.7%; 'Total lambs born per ewe' and 'Liveborn lambs born per ewe': 1.5 and 1.1 (P=0.01); 'Stillbirth rate' 0% and 0% and 'Lamb bodyweight per ewe': 5.0 kg and 3.8 kg (P=0.005). Anthelmintic treatment of pre-pubertal ewes, in order to maximise reproductive performance may be employed as a management strategy according to targets set in individual flocks.