Frequency of feeding during the periconceptional period did not alter reproduction in Merino sheep

Abstract

Context During drought, it is currently recommended to feed complete rations to sheep every second or third day, rather than daily, to reduce labour costs and the incidence of shy feeders. However, the frequency of feeding to ewes in the periconceptual period may influence fertility and fecundity and therefore profitability. Aims The study was designed to determine whether the feeding frequency of maintenance energy levels during joining affects reproductive performance and wool production of Merino ewes. Methods A group-fed pen study was conducted using two treatments and four replicates. Naturally oestrous-cycling Merino ewes (n = 800) were fed barley grain (90%) and wheat straw (10%) from 17 days before ram introduction until Day 30 of a 48-day joining period, either once-daily or on alternate days at maintenance energy levels. Lambing performance was recorded for 505 ewes pregnant by Day 19 of joining. Wool quality was assessed on Day 117 after commencement of joining. Key results Clinical acidosis occurred in both treatments, although the rate of mortality was low (4/800). The proportion of shy feeders was not affected (P = 0.486) by feeding frequency (n = 77, removed from pens). For the remaining ewes, weight loss was reduced by 1 kg (P = 0.003) when fed daily. Plasma progesterone concentrations post-mating were reduced (P < 0.001) by 18% with alternate-day feeding. Proportions of ewes mated, returning to service, pregnant or bearing multiple fetuses, lamb survival, lamb weights at marking and ram semen morphology were similar (P > 0.05) between feeding groups. Wool fibre diameter, staple strength and yield were similar between treatments. Ewes removed as shy feeders and joined on pasture recorded a 33% lower pregnancy rate but 17% higher rate of multiple fetuses than pen-joined ewes. Conclusions Ewes can be fed complete high-grain maintenance rations at 2-day intervals during joining without a reduction in reproductive traits or wool quality compared with daily feeding. Implications Producers may save labour with longer feeding intervals; however, greater monitoring and management intervention may be needed to maintain ewe liveweight when fed long term. Impacts in flocks without acidosis, on ram fertility when feeding is prolonged pre-joining, and with different diets require study.