Elsevier

Meat Science

Volume 181, November 2021, 108581
Meat Science

Impact of heat stress on the growth performance and retail meat quality of 2nd cross (Poll Dorset × (Border Leicester × Merino)) and Dorper lambs

https://doi.org/10.1016/j.meatsci.2021.108581Get rights and content

ABSTRACT

The present study investigated the impact of heat stress and genetics on lamb growth performance and meat quality. Forty-eight Dorper and 2nd cross [Poll Dorset × (Border Leicester × Merino)] lambs (38‐–42 kg; 4–5 months old) were allocated to either thermoneutral [TN; 18–21 °C, 45–55% relative humidity (RH)], or heat stress (HS; 28 °C–38 °C, 40–60% RH) conditions in a 2 × 2 factorial design for 2 weeks. Compared with 2nd cross, Dorper lambs had a lower respiration rate (RR) and rectal temperature (RT), and exhibited less decline in body weight under HS. 2nd cross lambs showed a higher body weight gain than Dorpers under TN conditions. HS increased a* and chroma of the Longissimus thoracis et lumborum (LTL) from 2nd cross lambs over 10 days of display, but had no impact on Dorper LTL. In conclusion, Dorpers showed higher heat tolerance compared with 2nd cross lambs during the 2 weeks HS.

Introduction

Heat stress (HS) is one of the greatest challenges facing the global livestock industry. An increase in global temperature and relative humidity (RH) is likely to compromise animal welfare and production during hot summer months, especially in the warmer parts of the world. HS occurs when an animal is unable to maintain normal core body temperature due to increased ambient temperature which compromises the animal's ability to lose heat from the body. HS is not only detrimental for animal welfare and production, but has been implicated in higher incidence of dark cutting or pale soft and exudative (PSE) meat (Gonzalez et al., 2020; Gregory, 2010; Zhang et al., 2020).

Stress is well known to deplete muscle glycogen stores and lead to lower acidification of postmortem muscle and consequently a higher ultimate pH (pHu) (Scanga, Belk, Tatum, Grandin, & Smith, 1998) and dark cutting. However, the studies reporting the impact of HS on different meat quality traits of ruminants are equivocal, and most of these focused on effects of long-term (≥ 1 month) HS. For example, Kadim, Mahgoub, and Khalaf (2014) reported that seasonal HS (34.3 ± 1.67 °C and 48.8 ± 7.57% RH, 6 m) had a negative effect on fresh colour, tenderness and water holding capacity (WHC) of sheep and goat meat. Conversely, albeit at a much lower ambient temperature, Saha et al. (2013) and Rana et al. (2014) reported that 4 and 8 h (27.8 °C, 81.9% RH; 45 d) heat exposure had no effect on goat slaughter weight and drip loss of the meat. Recently, Archana et al. (2018) showed that seasonal HS significantly increased Longissimus thoracis et lumborum (LTL) pH24, and shear force of meat from Osmanabadi and Salem Black goats, but had no influence on colour and WHC. The majority of researchers agree that high summer temperatures would have negative impact on animal welfare and meat quality (Gregory, 2010; Zhang et al., 2020). However, the extent to which it is affected may vary depending upon the severity of HS which in turn depends upon the daily ambient temperature, RH, and exposure duration (Tang, Yu, Zhang, & Bao, 2013; Zhang et al., 2018, Zhang et al., 2018) as animals may have variable responses to short-term and chronic HS. Ponnampalam et al. (2016) reported that one-week of HS (28–40 °C, 30–40% RH) had no effect on lamb growth performance (slaughter weight, carcass weight and fat depth) or meat quality (pHu and lipid oxidation). Thus, there is a need for further research to elucidate the impacts of HS exposure on growth performance and meat quality of small ruminants.

Hair and wool traits are known to affect heat tolerance in sheep (McManus et al., 2011). Hair sheep breeds such as Pelibuey, Dorper, Katahdin, and their crossbreds have better adaptability to high environmental temperatures which is attributed to improved physiological and metabolic responses (lower thyroid hormone levels and metabolic heat production, and deeper breathing compared with wool sheep breeds (Correa et al., 2012; Romero, Pardo, Montaldo, Rodriguez, & Ceron, 2013; Ross, Goode, & Linnerud, 1985). In Australia, higher carcass yield was reported for Dorper and Damara (African hair sheep) compared to Merino sheep (Almeida et al., 2013). However, it is unknown whether heat tolerance would have any implications for meat quality attributes and growth performance, when heat exposure shorter than 1 month and breeds are compared. The objective of this study was therefore to compare the growth performance and meat quality attributes of hair-type sheep breeds (Dorper) and wool-type sheep breeds [2nd cross; Poll Dorset × (Border Leicester × Merino)] exposed to two weeks of HS during the finishing phase. The choice of breeds for examination was based on the hypothesis that, under HS conditions, Dorper lambs (hair breed) would exhibit a higher degree of thermotolerance, better growth rates and meat quality attributes compared to 2nd cross lambs (wool breed).

Section snippets

Animals and experimental conditions

The experiment was approved by the University of Melbourne Faculty of Veterinary and Animal Sciences Animal Ethics Committee (AEC ID 1714357.1) and the protocols used for the live animal part of this study have been reported elsewhere (Joy et al., 2020). Briefly, forty-eight lambs [Poll Dorset × (Border Leicester × Merino) (n = 24) and Dorper (n = 24)] aged 4–5 months (body weight range: 38–42 kg) were purchased from 5 different breeders across North-East Victoria. All lambs were purchased

THI and growth performance

Temperature–humidity index (THI) is commonly used to measure heat stress which is calculated based on the ambient temperature and relative humidity. An ambient environment with a THI lower than 22.2 is classified as the absence of a heat stress condition. From 22.2 to 23.3 is recognized as moderate heat stress. When THI ranges from 23.3 to 25.6, it is referred to as a severe heat stress condition, and extreme severe heat stress condition when the THI exceeds 25.6 (Marai et al., 2007; St Pierre,

Conclusion

Two weeks cyclic HS had significant negative effect on both Dorper and 2nd cross lambs' physiological responses and growth performance. When exposed to 2 weeks cyclic HS, Dorpers showed higher heat tolerance (less decline of feed intake and body weight and lower RR and RT) than 2nd cross lambs. However, 2nd cross lamb's had higher growth performance compared with Dorpers under the TN conditions. Two weeks of heat exposure caused a small increase in muscle pHu of the two breeds. In terms of

Acknowledgements

Authors would like to acknowledge Faculty of Veterinary and Agricultural Sciences, The University of Melbourne and Lindsay and Alice Gamble trust fund for providing top up scholarship to Minghao Zhang and start up fund to Dr. Surinder Singh Chauhan to conduct this research.

References (47)

  • T.T. Ross et al.

    Effects of high ambient temperature on respiration rate, rectal temperature, fetal development and thyrold gland activity in tropical and temperate breeds of sheep

    Theriogenology

    (1985)
  • S.J. Schoeman

    A comparative assessment of Dorper sheep in different production environments and systems

    Small Ruminant Research

    (2000)
  • N. Silanikove

    Effects of heat stress on the welfare of extensively managed domestic ruminants

    Livestock Production Science

    (2000)
  • A. Srikandakumar et al.

    Effect of heat stress on respiratory rate, rectal temperature and blood chemistry in Omani and Australian Merino sheep

    Small Ruminant Research

    (2003)
  • N.R. St Pierre

    Economic losses from heat stress by US livestock industries

    Journal of Dairy Science

    (2003)
  • Y.M. Zhang et al.

    Carbon monoxide packaging shows the same color improvement for dark cutting beef as high oxygen packaging

    Meat Science

    (2018)
  • F. Adzitey

    Pale soft exudative (PSE) and dark firm dry (DFD) meats: Causes and measures to reduce these incidences – A mini review

    International Food Research Journal

    (2011)
  • A. Aggarwal et al.

    Heat stress and reproduction

    (2013)
  • A.M. Almeida et al.

    Assessing carcass and meat characteristics of Damara, Dorper and Australian merino lambs under restricted feeding

    Tropical Animal Health and Production

    (2013)
  • P.E. Bouton et al.

    Effect of ultimate ph upon the water-holding capacity and tenderness of mutton

    Journal of Food Science

    (1971)
  • S.S. Chauhan et al.

    Errata

    Journal of Animal Science

    (2015)
  • S.S. Chauhan et al.

    The impact of antioxidant supplementation and heat stress on carcass characteristics, muscle nutritional profile and functionality of lamb meat

    Animals

    (2020)
  • A.W. Franzmann

    Variation of rectal temperature in bighorn sheep

    The Journal of Wildlife Management

    (1971)
  • Cited by (5)

    • Non-invasive measure of heat stress in sheep using machine learning techniques and infrared thermography

      2022, Small Ruminant Research
      Citation Excerpt :

      The live animal study was approved by the Faculty of Veterinary and Agricultural Sciences, The University of Melbourne Animal Ethics Committee (Ethics ID: 1714357.1) and was conducted at The University of Melbourne, Dookie Campus, Victoria, Australia (36°23′01.9″S 145°42′52.1″E) over two weeks. The details on animals and experimental design have been previously reported by Joy et al. (2020b) and Zhang et al. (2021). Briefly, 48 lambs of two different breeds, Dorper and 2nd Cross [SC; Poll Dorset X (Border Leicester X Merino)] lambs (24 lambs from each breed; 4−5 months old with live weight = 40.9 ± 0.91 kg, (Mean ± SD) were used in the study.

    • Applications of Genetic Selection in Breeding for Thermo-Tolerance in Livestock

      2022, Climate Change and Livestock Production: Recent Advances and Future Perspectives
    View full text