ReviewImpact of heat stress on milk production, immunity and udder health in sheep: A critical review
Introduction
Mediterranean countries including France, Greece, Italy, Spain and Turkey account for sheep milk production of about 2,900,000 MT (million tonnes), and were among the first twelve countries in the world for sheep milk production in 2009 (Faostat, 2012). The Mediterranean basin is characterized by hot, dry summers and cool, wet winters. Sheep are believed to be one of the most resistant species to climatic extremes, especially to high ambient temperatures. Temperatures in the Mediterranean basin, however, can often exceed sheep thermoneutral zone, which is comprised between 5 °C and 25 °C (Curtis, 1983). Temperatures higher than the upper critical point can affect both physiological and production performance of lactating sheep. Hot climates may increase energy requirements for maintenance by 7–25%, by inducing a rise in body temperature and breath rate. Feed intake decreases in heat stressed sheep (Marai et al., 2007), especially when they are offered low quality feed (Costa et al., 1992), due to both the attempt of reducing heat production and the reduction of feed transit through the digestive tract. Under these conditions, body reserves of fat and nitrogen are used to supply energy through gluconeogenesis at the expense of the mammary gland, especially in early lactating animals (Amaral-Phillips et al., 1993). In the Mediterranean basin, the rise in ambient temperatures occurs together with the late stage of lactation of dairy ewes. Both heat stress and the advancement of lactation concur to reduce mobilization of body reserve for milk synthesis, thus inducing a worsening of milk yield and quality. Milk from sheep is entirely destined for cheese production; as a consequence, sheep milk is requested to contain high contents of fat and protein to produce high-quality cheese. Heat stress can affect milk composition through a reduction of fat and protein content. High ambient temperatures can also result in plasma mineral imbalance, especially due to reduction in sodium, potassium, calcium and phosphorus and increase in chloride concentrations (Kume et al., 1987, Schneider et al., 1988, Caroprese et al., 2012). Published evidence does not prove that ambient temperature is directly related to udder health, but indicates that it may interact with other predisposing conditions to exert an influence (Klastrup et al., 1987). In the present review the effects of heat stress on the sheep production performance and on milk quality are discussed together with the effects on immunological state and udder health. Strategies to reduce the negative effects of heat stress in sheep are proposed.
Section snippets
Heat stress and sheep production responses
In sheep the efficacy of thermoregulatory mechanisms largely depends on sheep breeds and individual animal genetics. Thermoregulation in newborn lambs can be influenced by the environmental temperature the mothers were exposed to during pregnancy (Stott and Slee, 1985). Furthermore, lambs born from ewes of the same flock and breed, which were able to maintain low rectal temperature have higher birth weight than lambs born from ewes with higher rectal temperature, suggesting that selection of
Heat stress and sheep immune responses
Environmental factors such as ambient temperature have been implicated in alterations of livestock immune function. Heat response at cellular levels includes the synthesis of heat shock proteins, which are divided into a set of different families according to their molecular weights. The most studied of these proteins have molecular weights of approximately 90, 70 and 27 kDa and are referred to as HSP90, HSP70 and HSP27 (Guerriero and Raynes, 1990). HSP, whose expression and activity is strictly
Heat stress and sheep udder health
The incidence of udder health problems in sheep increases during summer because heat stress itself can negatively influenced sheep health by altering sheep normal physiological functions. It is apparent that microorganisms responsible for clinical or sub-clinical infections of ewe udder can increase in summer because of the warm environmental conditions and high relative humidity which occur in the Mediterranean basin.
Exposure to solar radiation has a detrimental effect on the hygienic quality
Conclusions
Field trials have clearly demonstrated that, even if sheep are considered to be among the most heat tolerant species, exposure to high ambient temperatures has a detrimental impact on their production performance, including milk nutritional and technological properties. Evidence exists that management and nutritional strategies able to reduce the negative effects of thermal stress on sheep milk production can also improve sheep immunological functions and udder health. So the reduction of
References (63)
- et al.
Effects of somatic cell count and stage of lactation on the plasmin activity and cheese-making properties of ewe milk
J. Dairy Sci.
(2004) - et al.
Effects of decreased availability of glucose for dairy cows
J. Dairy Sci.
(1993) - et al.
Partitioning of nutrients during pregnancy and lactation: a review of mechanism involving homeostasis and homeorhesis
J. Dairy Sci.
(1980) - et al.
Effects of shade and flaxseed supplementation on the welfare of lactating ewes under high ambient temperatures
Small Rumin. Res.
(2012) - et al.
Effect of solar radiation and flaxseed supplementation on milk production and fatty acid profile of lactating ewes under high ambient temperature
J. Dairy Sci.
(2011) - et al.
Effects of two different housing systems on behavior, physiology and milk yield of Comisana ewes
Small Rumin. Res.
(2001) - et al.
Invited review: genes involved in the bovine heat stress response
J. Dairy Sci.
(2008) - et al.
Thermal stress as a factor associated with nutrient requirements and interrelationships
- et al.
Factors influencing variation of fatty acid content in ovine milk
J. Dairy Sci.
(2009) - et al.
Conjugated linoleic acid (CLA) content of milk from cows offered diets rich in linoleic and linolenic acid
J. Dairy Sci.
(2000)
Effect of dose of bovine growth hormone on milk composition: alpha-lactalbumin, fatty acids, and mineral elements
J. Dairy Sci.
Effect of psychrotrophic microorganisms on the plasmin system in milk
J. Dairy Sci.
Effect of heat stress on production of Mediterranean dairy sheep
J. Dairy Sci.
Effect of feed on the composition of milk fat
J. Dairy Sci.
Seasonal variation in milk conjugated linoleic acid and Δ9-desaturase in dairy cows
Livest. Prod. Sci.
Effect of a diet enriched in whole linseed and sunflower oil and goat milk fatty acid composition and conjugated linoleic acid isomer profile
J. Dairy Sci.
Physiological traits as affected by heat stress in sheep – a review
Small Rumin. Res.
Utilization of nutrients by sheep as affected by diet composition and solar radiation
Small Rumin. Res.
Seasonal variation in conjugated linoleic acid and vaccenic acid in milk fat of sheep and its transfer to cheese and ricotta
J. Dairy Sci.
Effects of lambing season and stage of lactation on ewe milk quality
Small Rumin. Res.
Effects of solar radiation and feeding time on behavior, immune response and production of lactating ewes under high ambient temperature
J. Dairy Sci.
Effects of water scarcity and hot environment on appetite and digestion in ruminants: a review
Livest. Prod. Sci.
Effects of heat stress on the welfare of extensively managed domestic ruminants
Livest. Prod. Sci.
Some effects of acute fasting and climatic stresses upon milk secretion in Friesland sheep
Comp. Biochem. Physiol.
Coronary heart disease: seven dietary factors
Lancet
Differential regulation of interleukin-10 (IL-10) and IL-12 by glucocorticoids in vitro
Blood
Variability in cytokine production and cell proliferation by mitogen-activate ovine peripheral blood mononuclear cells: modulation by interleukin (IL)-10 and IL-12
Vet. Immunol. Immunopathol.
Effects of feeding oilseeds rich in linoleic and linolenic fatty acids to lactating ewes on cheese yield and on fatty acid composition of milk and cheese
Anim. Feed Sci. Technol.
Effects of flaxseed supplementation to lactating ewes on milk composition, cheese yield, and fatty acid composition of milk and cheese
Small Rumin. Res.
Effect of different ventilation regimes on ewe milk and Canestrato Pugliese cheese quality in summer
J. Dairy Res.
Interleukin-10 therapy—review of a new approach
Pharm. Rev.
Cited by (75)
Effects of extreme heat on milk quantity and quality
2023, Agricultural SystemsA review on the potential effects of environmental and economic factors on sheep genetic diversity: Consequences of climate change
2023, Saudi Journal of Biological SciencesCitation Excerpt :Heat stress affects the synthesis of heat shock proteins (HSPs) at the cellular level. HSPs prevent the formation of non-specific protein aggregates and assist cellular proteins in the acquisition of native nature hence playing vital cellular homeostasis (Singh et al., 2017) enhancing inert immunity which acts as a first-level defense mechanism (Sevi & Caroprese, 2012). There aren't many studies on how terrestrial mammals adapt to cold temperatures, but it is known that these adaptations entail processes that help with thermal insulation.
Effect of short-term radiation stress on physiological and hematological parameters in Pelibuey sheep in Cuba
2022, Small Ruminant ResearchCitation Excerpt :Animals experiencing radiation stress engage a range of physiological and behavioral compensatory mechanisms in attempts to thermoregulate. One of the primary responses to radiation stress is a reduction in feed intake (Marai et al., 2007) leading to decreased growth, poor milk production (Sevi and Caroprese, 2012) and ultimately resulting in economic losses for the farmer. Physiological responses include increasing respiration, heart rate and rectal temperature (Marai et al., 2007).