The influence of heat load on Merino sheep. 1. Growth, performance, behaviour and climate
A. M. Lees
A B D , M. L. Sullivan A , J. C. W. Olm C , A. J. Cawdell-Smith A and J. B. Gaughan A
A School of Agriculture and Food Sciences, Animal Science Group, The University of Queensland, Gatton, Qld 4343, Australia.
B Present address: School of Environmental and Rural Science, University of New England, Armidale, NSW 2350, Australia.
C School of Veterinary Science, The University of Queensland, Gatton, Qld 4343, Australia.
D Corresponding author. Email: a.lees@uqconnect.edu.au
Animal Production Science 60(16) 1925-1931 https://doi.org/10.1071/AN19687
Submitted: 30 November 2019 Accepted: 4 May 2020 Published: 7 July 2020
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.
Additional keywords: feed intake, live export, posture, rumination, temperature humidity index, water intake.
References
Abdalla EB, Kotby EA, Johnson HD (1993) Physiological responses to heat-induced hyperthermia of pregnant and lactating ewes. Small Ruminant Research 11, 125–134.| Physiological responses to heat-induced hyperthermia of pregnant and lactating ewes.Crossref | GoogleScholarGoogle Scholar |
Achmadi J, Yanagisawa T, Sano H, Terashima Y (1993) Pancreatic insulin secretory response and insulin action in heat-exposed sheep given a concentrate or roughage diet. Domestic Animal Endocrinology 10, 279–287.
| Pancreatic insulin secretory response and insulin action in heat-exposed sheep given a concentrate or roughage diet.Crossref | GoogleScholarGoogle Scholar | 8306632PubMed |
Alhidary IA, Shini S, Al Jassim RAM, Gaughan JB (2012) Physiological responses of Australian Merino wethers exposed to high heat load. Journal of Animal Science 90, 212–220.
| Physiological responses of Australian Merino wethers exposed to high heat load.Crossref | GoogleScholarGoogle Scholar | 21841087PubMed |
Baumgard LH, Rhoads RP (2012) Ruminant nutrition symposium: ruminant production and metabolic responses to heat stress. Journal of Animal Science 90, 1855–1865.
| Ruminant nutrition symposium: ruminant production and metabolic responses to heat stress.Crossref | GoogleScholarGoogle Scholar | 22205665PubMed |
Beatty DT, Barnes A, Fleming PA, Taylor E, Maloney SK (2008) The effect of fleece on core and rumen temperature in sheep. Journal of Thermal Biology 33, 437–443.
| The effect of fleece on core and rumen temperature in sheep.Crossref | GoogleScholarGoogle Scholar |
Beede DK, Collier RJ (1986) Potential nutritional strategies for intensively managed cattle during thermal stress. Journal of Animal Science 62, 543–554.
| Potential nutritional strategies for intensively managed cattle during thermal stress.Crossref | GoogleScholarGoogle Scholar |
Blaxter KL, Graham NM, Wainman FW, Armstrong DG (1959) Environmental temperature, energy metabolism and heat regulation in sheep. II. The partition of heat losses in closely clipped sheep. The Journal of Agricultural Science 52, 25–40.
| Environmental temperature, energy metabolism and heat regulation in sheep. II. The partition of heat losses in closely clipped sheep.Crossref | GoogleScholarGoogle Scholar |
Chauhan SS, Celi P, Leury BJ, Clarke IJ, Dunshea FR (2014) Dietary antioxidants at supranutritional doses improve oxidative status and reduce the negative effects of heat stress in sheep. Journal of Animal Science 92, 3364–3374.
| Dietary antioxidants at supranutritional doses improve oxidative status and reduce the negative effects of heat stress in sheep.Crossref | GoogleScholarGoogle Scholar | 24894002PubMed |
Collins T, Hampton J, Barnes A (2018) A systematic review of heat load in Australian livestock transported by sea. Animals 8, 164
| A systematic review of heat load in Australian livestock transported by sea.Crossref | GoogleScholarGoogle Scholar |
Department of Agriculture and Fisheries (2009) ‘Animal care and protection act 2001.’ (Queensland Government: Brisbane)
Department of Agriculture Fisheries and Forestry (2011) Australian standards for the export of livestock (version 2.3) 2011 and the Australian position statement of the export of livestock. Available at: http://www.agriculture.gov.au/ [Verified 18 May 2016]
DeShazer JA, Hahn GL, Xinm H (2009) Basic principals of the thermal environment and livestock energetics. In ‘Livestock energetics and thermal environmental management’. pp. 1–22 (Ed JA DeShazer) (American Society of Agricultural and Biological Engineers: St. Joseph, MI)
Dixon R, Thomas R, Holmes J (1999) Interactions between heat stress and nutrition in sheep fed roughage diets. The Journal of Agricultural Science 132, 351–359.
| Interactions between heat stress and nutrition in sheep fed roughage diets.Crossref | GoogleScholarGoogle Scholar |
El-Nouty FD, Elbanna IM, Davis TP, Johnson HD (1980) Aldosterone and ADH response to heat and dehydration in cattle. Journal of Applied Physiology 48, 249–255.
| Aldosterone and ADH response to heat and dehydration in cattle.Crossref | GoogleScholarGoogle Scholar | 7364609PubMed |
Finch VA (1986) Body temperature in beef cattle: its control and relevance to production in the tropics. Journal of Animal Science 62, 531–542.
| Body temperature in beef cattle: its control and relevance to production in the tropics.Crossref | GoogleScholarGoogle Scholar |
Fuquay JW (1981) Heat stress as it affects animal production. Journal of Animal Science 52, 164–174.
| Heat stress as it affects animal production.Crossref | GoogleScholarGoogle Scholar | 7195394PubMed |
Gaughan JB, Davis MS, Mader TL (2004) Wetting and the physiological responses of grain-fed cattle in a heated environment. Australian Journal of Agricultural Research 55, 253–260.
| Wetting and the physiological responses of grain-fed cattle in a heated environment.Crossref | GoogleScholarGoogle Scholar |
Hahn GL (1999) Dynamic responses of cattle to thermal heat loads. Journal of Animal Science 77, 10–20.
| Dynamic responses of cattle to thermal heat loads.Crossref | GoogleScholarGoogle Scholar | 15526777PubMed |
Hales JRS, Brown GD (1974) Net energetic and thermoregulatory efficiency during panting in the sheep. Comparative Biochemistry and Physiology. Part A, Physiology 49, 413–422.
| Net energetic and thermoregulatory efficiency during panting in the sheep.Crossref | GoogleScholarGoogle Scholar |
Livecorp (2018) Sheep statistics. Available at http://www.livecorp.com.au [Verified 21 July 2018]
Mahjoubi E, Amanlou H, Mirzaei-Alamouti HR, Aghaziarati N, Yazdi MH, Noori GR, Yuan K, Baumgard LH (2014) The effect of cyclical and mild heat stress on productivity and metabolism in Afshari lambs. Journal of Animal Science 92, 1007–1014.
| The effect of cyclical and mild heat stress on productivity and metabolism in Afshari lambs.Crossref | GoogleScholarGoogle Scholar | 24492566PubMed |
Mahjoubi E, Yazdi MH, Aghaziarati N, Noori GR, Afsarian O, Baumgard LH (2015) The effect of cyclical and severe heat stress on growth performance and metabolism in Afshari lambs. Journal of Animal Science 93, 1632–1640.
| The effect of cyclical and severe heat stress on growth performance and metabolism in Afshari lambs.Crossref | GoogleScholarGoogle Scholar | 26020185PubMed |
Marai IFM, El-Darawany AA, Fadiel A, Abdel-Hafez MAM (2007) Physiological traits as affected by heat stress in sheep: a review. Small Ruminant Research 71, 1–12.
| Physiological traits as affected by heat stress in sheep: a review.Crossref | GoogleScholarGoogle Scholar |
Mitlöhner FM, Morrow-Tesch JL, Wilson SC, Dailey JW, McGlone JJ (2001) Behavioral sampling techniques for feedlot cattle. Journal of Animal Science 79, 1189–1193.
| Behavioral sampling techniques for feedlot cattle.Crossref | GoogleScholarGoogle Scholar | 11374538PubMed |
National Health and Medical Research Council (2013) ‘Australian code for the care and use of animals for scientific purposes.’ (National Health and Medical Research Council: Canberra)
O’Brien MD, Rhoads RP, Sanders SR, Duff GC, Baumgard LH (2010) Metabolic adaptations to heat stress in growing cattle. Domestic Animal Endocrinology 38, 86–94.
| Metabolic adaptations to heat stress in growing cattle.Crossref | GoogleScholarGoogle Scholar | 19783118PubMed |
Pearce SC, Gabler NK, Ross JW, Escobar J, Patience JF, Rhoads RP, Baumgard LH (2013) The effects of heat stress and plane of nutrition on metabolism in growing pigs. Journal of Animal Science 91, 2108–2118.
| The effects of heat stress and plane of nutrition on metabolism in growing pigs.Crossref | GoogleScholarGoogle Scholar | 23463563PubMed |
Pines MK, Phillips CJC (2013) Microclimatic conditions and their effects on sheep behavior during a live export shipment from Australia to the Middle East. Journal of Animal Science 91, 4406–4416.
| Microclimatic conditions and their effects on sheep behavior during a live export shipment from Australia to the Middle East.Crossref | GoogleScholarGoogle Scholar | 23825334PubMed |
Russel AJF, Doney JM, Gunn RG (1969) Subjective assessment of body fat in live sheep. The Journal of Agricultural Science 72, 451–454.
| Subjective assessment of body fat in live sheep.Crossref | GoogleScholarGoogle Scholar |
Savage DB, Nolan JV, Godwin IR, Mayer DG, Aoetpah A, Nguyen T, Baillie ND, Rheinberger TE, Lawlor C (2008) Water and feed intake responses of sheep to drinking water temperature in hot conditions. Australian Journal of Experimental Agriculture 48, 1044–1047.
| Water and feed intake responses of sheep to drinking water temperature in hot conditions.Crossref | GoogleScholarGoogle Scholar |
Seif SM, Johnson HD, Hahn L (1973) Environmental heat and partial water restriction effects on body fluid spaces, water loss, body temperature, and metabolism of Holstein cows. Journal of Dairy Science 56, 581–586.
| Environmental heat and partial water restriction effects on body fluid spaces, water loss, body temperature, and metabolism of Holstein cows.Crossref | GoogleScholarGoogle Scholar |
Sejian V, Singh AK, Sahoo A, Naqvi SMK (2014) Effect of mineral mixture and antioxidant supplementation on growth, reproductive performance and adaptive capability of Malpura ewes subjected to heat stress. Journal of Animal Physiology and Animal Nutrition 98, 72–83.
| Effect of mineral mixture and antioxidant supplementation on growth, reproductive performance and adaptive capability of Malpura ewes subjected to heat stress.Crossref | GoogleScholarGoogle Scholar | 23332025PubMed |
Sheridan R, Ferreira AV, Hoffman LC (2003) Production efficiency of South African Mutton Merino lambs and Boer goat kids receiving either a low or a high energy feedlot diet. Small Ruminant Research 50, 75–82.
| Production efficiency of South African Mutton Merino lambs and Boer goat kids receiving either a low or a high energy feedlot diet.Crossref | GoogleScholarGoogle Scholar |
Silanikove N (1987) Impact of shelter in hot Mediterranean climate on feed intake, feed utilization and body fluid distribution in sheep. Appetite 9, 207–215.
| Impact of shelter in hot Mediterranean climate on feed intake, feed utilization and body fluid distribution in sheep.Crossref | GoogleScholarGoogle Scholar | 3435137PubMed |
Silanikove N (1992) Effects of water scarcity and hot environment on appetite and digestion in ruminants: a review. Livestock Production Science 30, 175–194.
| Effects of water scarcity and hot environment on appetite and digestion in ruminants: a review.Crossref | GoogleScholarGoogle Scholar |
Silanikove N (2000) Effects of heat stress on the welfare of extensively managed domestic ruminants. Livestock Production Science 67, 1–18.
| Effects of heat stress on the welfare of extensively managed domestic ruminants.Crossref | GoogleScholarGoogle Scholar |
Srikandakumar A, Johnson EH, Mahgoub O (2003) Effect of heat stress on respiratory rate, rectal temperature and blood chemistry in Omani and Australian Merino sheep. Small Ruminant Research 49, 193–198.
| Effect of heat stress on respiratory rate, rectal temperature and blood chemistry in Omani and Australian Merino sheep.Crossref | GoogleScholarGoogle Scholar |
Stockman CA, Barnes AL, Maloney SK, Taylor E, McCarthy M, Pethick D (2011) Effect of prolonged exposure to continuous heat and humidity similar to long haul live export voyages in Merino wethers. Animal Production Science 51, 135–143.
| Effect of prolonged exposure to continuous heat and humidity similar to long haul live export voyages in Merino wethers.Crossref | GoogleScholarGoogle Scholar |
Wheelock JB, Rhoads RP, VanBaale MJ, Sanders SR, Baumgard LH (2010) Effects of heat stress on energetic metabolism in lactating Holstein cows. Journal of Dairy Science 93, 644–655.
| Effects of heat stress on energetic metabolism in lactating Holstein cows.Crossref | GoogleScholarGoogle Scholar | 20105536PubMed |
Wickham SLFleming PACollins T (2017 ) ‘
