Comparative Assessment of Thermotolerance in Dorper and Second-Cross (Poll Dorset/Merino × Border Leicester) Lambs

The objective of this study was to compare the thermotolerance of second-cross (SC; Poll Dorset × Merino × Border Leicester) and Dorper lambs. Dorper and SC lambs (4-5 months of age) were subjected to cyclic heat stress (HS) (28-40 °C). The temperature was increased to 38-40 °C between 800 and 1700...

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Bibliographic Details
Published in:	Animals (Basel) Vol. 10; no. 12; p. 2441
Main Authors:	Joy, Aleena, Dunshea, Frank R, Leury, Brian J, DiGiacomo, Kristy, Clarke, Iain J, Zhang, Minghao H, Abhijith, Archana, Osei-Amponsah, Richard, Chauhan, Surinder S
Format:	Journal Article
Language:	English
Published:	Switzerland MDPI AG 20-12-2020 MDPI
Subjects:	Adaptability Animals Blood Climate change Climatic conditions Creatinine Efficiency Electrolytes Esterification Feeds Fertility Genotype & phenotype Genotypes Heat Heat stress Heat tolerance Hemoglobin Humidity Livestock Livestock production Metabolism Physiology Prolactin Rectum Relative humidity Respiration Sheep Skin Skin temperature Temperature tolerance Test chambers Thermal cycling thermotolerance Urea Variance analysis Water intake Water intakes Wool Australia United States > US physiology heat stress prolactin thermotolerance sheep
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Summary:	The objective of this study was to compare the thermotolerance of second-cross (SC; Poll Dorset × Merino × Border Leicester) and Dorper lambs. Dorper and SC lambs (4-5 months of age) were subjected to cyclic heat stress (HS) (28-40 °C). The temperature was increased to 38-40 °C between 800 and 1700 h daily and maintained at 28 °C for the remainder of the day (30-60% relative humidity (RH)) in climatic chambers for 2 weeks ( = 12/group), with controls maintained in a thermoneutral (TN) (18-21 °C, 40-50% RH) environment ( = 12/group). Basal respiration rate (RR), rectal temperature (RT) and skin temperature (ST) were higher ( < 0.01) in SC lambs than in Dorpers. HS increased RR, RT and ST ( < 0.01) in both genotypes, but the levels reached during HS were lower ( < 0.01) in Dorpers. HS increased ( < 0.01) water intake to a greater extent in SC lambs, while feed intake was reduced ( < 0.05) by HS in SC lambs but not in Dorpers. HS increased ( < 0.01) blood urea nitrogen and creatinine in SC lambs only. Plasma non-esterified fatty acid concentrations were reduced ( < 0.05) by HS in SC lambs but increased ( < 0.05) in Dorpers. There was no effect of HS on pO , cHCO and cSO , but higher ( < 0.01) blood pH and lower ( < 0.01) pCO were recorded under HS in both genotypes. Blood electrolytes and base excess were reduced ( < 0.01) under HS, while a genotype difference ( < 0.05) was only observed in blood K and hemoglobin concentrations. Basal plasma prolactin concentrations were lower ( < 0.01) in Dorpers but were elevated at a similar level during HS ( < 0.01) in both genotypes. Dorper lambs are more resilient to HS than SC lambs. Future research should focus on confirming whether the better heat tolerance of Dorpers is translated to better returns in terms of growth performance and carcass traits over the summer months.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	2076-2615 2076-2615
DOI:	10.3390/ani10122441