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 ’: 8.5 m and 10.0 m ( 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.