Please use this identifier to cite or link to this item: https://hdl.handle.net/1959.11/35543
Title: The influence of heat load on Merino sheep. 1. Growth, performance, behaviour and climate
Contributor(s): Lees, A M  (author)orcid ; Sullivan, M L (author); Olm, J C W (author); Cawdell-Smith, A J (author); Gaughan, J B (author)
Publication Date: 2020
Early Online Version: 2020-07-07
DOI: 10.1071/AN19687
Handle Link: https://hdl.handle.net/1959.11/35543
Abstract: 

Context. Annually, millions of sheep are exported from Australia to the Middle East, typically during the southern hemisphere winter to the northern hemisphere summer. During these voyages, sheep can be exposed to relatively rapid changes in ambient conditions within a short period of time (≤29 days); therefore, excessive heat load concerns can arise.

Aims. The aim of this study was to define the responses of sheep to incremental heat load under simulated live export conditions. The study herein describes (1) the heat load imposed, and (2) the effect of this heat load on the growth, performance and behavioural responses of sheep during periods of incremental heat load.

Methods. A total of 144 Merino wethers (44.02 ± 0.32 kg) were included in a 29-day climate controlled study using two cohorts of 72 sheep (n = 2), exposed to two treatments: (1) thermoneutral and (2) hot (HOT). Ambient temperature (°C) and relative humidity (%) for the HOT treatment were modelled from live export voyages from Australia to the Middle East in July. Climatic conditions within the climate control chambers were recorded at 10-min intervals, then used to calculate a temperature humidity index. Sheep posture, rumination, eating, drinking and demeanour (calm, agitated or depressed) were observed four times daily at 3-h intervals between 0800 hours and 1700 hours. Feed intake was recorded daily and water intake was measured using an automated meter. Sheep were weighed on Day 0 and then at 7-day intervals. Sheep were weighed at slaughter and carcass weights were obtained, these data were used to determine carcass dressing percentage. Data were analysed using a repeated measures model, with a compound symmetry covariance structure.

Key results. Climatic conditions in the HOT treatment increased incrementally between Day 1 (temperature humidity index ≥19) and Day 29 (temperature humidity index ≤34.7). Behaviour, feed intake, average daily gain (g/day), carcass weight (kg) and dressing percentage were not influenced by treatment (P > 0.05). Sheep in the HOT treatment group showed a 137% increase in water intake (P < 0.01) and on average consumed 2.15 L/sheep.day, whereas the thermoneutral group consumed 1.67 L/sheep.day.

Conclusions. These results suggest that these sheep were capable of maintaining feed intake and growth despite exposure to heat load, albeit with a 137% increase in water intake.

Implications. These results highlight the resilience of the Australian Merino genotype, as these sheep were capable of maintaining feed intake and growth during exposure to heat load. As the climatic conditions in this study were modelled based on typical live export vessel conditions, these results may suggest that the climatic conditions experienced by sheep during voyages may not be as critical as previously thought.

Publication Type: Journal Article
Source of Publication: Animal Production Science, 60(16), p. 1925-1931
Publisher: CSIRO Publishing
Place of Publication: Australia
ISSN: 1836-5787
1836-0939
Fields of Research (FoR) 2008: 070203 Animal Management
Fields of Research (FoR) 2020: 300302 Animal management
300306 Animal welfare
Socio-Economic Objective (SEO) 2008: 839901 Animal Welfare
Socio-Economic Objective (SEO) 2020: 109902 Animal welfare
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article
School of Environmental and Rural Science

Files in This Item:
1 files
File SizeFormat 
Show full item record

SCOPUSTM   
Citations

4
checked on Mar 23, 2024

Page view(s)

1,162
checked on Mar 17, 2024

Download(s)

2
checked on Mar 17, 2024
Google Media

Google ScholarTM

Check

Altmetric


Items in Research UNE are protected by copyright, with all rights reserved, unless otherwise indicated.