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RESEARCH ARTICLE (Open Access)

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

Susan M. Robertson https://orcid.org/0000-0001-5129-2216 A B C * , Alexandra Morona A , Allan Gunn A C , John Piltz https://orcid.org/0000-0003-3331-3508 D , Christopher J. Scott E and Michael A. Friend F
+ Author Affiliations
- Author Affiliations

A School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.

B Fred Morley Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.

C Gulbali Institute, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.

D Department of Primary Industries NSW, Wagga Wagga Agricultural Institute, Pine Gully Road, Wagga Wagga, NSW 2650, Australia.

E School of Dentistry and Medical Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.

F Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.

* Correspondence to: surobertson@csu.edu.au

Handling Editor: Andy Greer

Animal Production Science 63(1) 59-69 https://doi.org/10.1071/AN22161
Submitted: 20 April 2022  Accepted: 1 August 2022   Published: 9 September 2022

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

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.

Keywords: drought, embryo mortality, feedlots, fertility, nutrition, reproduction, sheep, wool.


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