Effect of Heat Stress on Production of Mediterranean Dairy Sheep

Abstract

RIASSUNTO -Effetto delloKEY WORDS: heat tolerance, temperature-humidity index (THI), dairy sheep.INTRODUCTION -European Mediterranean countries are characterized by exposure to considerable heat between three and six months annually. High ambient temperature, solar radiation, wind speed and relative humidity, cause the effective temperature of the environment to be above the thermo-neutral zone of the animals (5 to 25ºC; McDowell, 1972) and therefore heat stress occurs (Bianca, 1962). Heat stress is one of the limiting factors in dairy production in hot climates (Johnson et al., 1962) and is hard to account for by management in the extensive grazing-based farming system of Mediterranean dairy sheep where animals are rarely kept indoors. The interest of our study was to investigate if in the Mediterranean area heat stress has an effect on dairy sheep performance. Some studies (Ames et al., 1971;Sevi et al., 2001) on sheep heat stress investigated changes in rectal temperatures, respiration rates, volumes of air inhaled and other physiological functions. Unfortunately, such measurements are costly and not feasible on a large scale in practical farming circumstances, which leads to insufficient data quantity, especially for genetic studies. In the present paper the methodology of Ravagnolo et al. (2000) based on using weather station data for Holstein cattle was applied to Valle del Belice dairy sheep. The animals were investigated with the following aims: to establish the relationship between production and weather conditions using information from a weather station, and to estimate the additive genetic variances of milk production traits and heat tolerance, and therefore to investigate the possibility of future selection for increased heat tolerance.

Genetic variability for heat stress sensitivity in Merino de Grazalema sheep

“…This temperature increase can negatively affect the physiology and performances of this breed in a similar manner to that which has been reported to affect other dairy animals (West, 2003). The economic consequence of heat stress has already been identified for Murciano-Granadina and Payoya goats in Spain (Menéndez-Buxadera et al, 2012) and similar effects were also reported for milk yield in Valle del Belice dairy sheep in Palermo, Italy (Finocchiaro et al, 2005). Moreover, both groups of authors found important genetic variation in response to heat stress.…”

“…This made it possible to quantify the reaction norm or plasticity of each trait -an old biological concept recently reviewed by de Jong and Bijma (2002). Random regression models were used for these analyses in dairy cattle (Bohmanova et al, 2005(Bohmanova et al, , 2008Aguilar et al, 2009;Brugemann et al, 2011;Bernabucci et al, 2014;Hammami et al, 2013), dairy sheep (Finocchiaro et al, 2005) and dairy goats (Menéndez-Buxadera et al, 2012). The application of the random regression models to solve different types of problems in animal breeding was reviewed by Schaeffer (2004).…”

Climatic Effects on Productive Traits in Livestock

“…Milk production traits in ewes seem to have higher negative correlation with the direct values of temperature or relative humidity than THI. The values of THI above which ewes start to suffer from HS seem to be quite different among sheep breeds (Finocchiaro et al, 2005). Solar radiation seems to have a lesser effect on milk yield, but a greater effect on yield of casein, fat and clot firmness in the milk of Comisana ewes (Sevi et al, 2001).…”

Genetics of adaptation in domestic farm animals: A review

“…The authors reported significant differences between animals due to breed, skin type and time of the day and concluded the Santa Inês (hair sheep) with white color were shown to be better adapted to higher environmental temperatures while Bergamasca, wool sheep, were least adapted. Finocchiaro et al (2005) reported the genetic correlation between the general additive effect of milk production and the additive effect of heat tolerance to be negative (r = −0.8) during all periods considered indicating that selection for increased milk production will reduce heat tolerance. Turner (1980) extensively reviewed the genetic and biological aspects of zebu adaptability and attributed their unique suiting to hot climates to coat, hide, skin, hematological characteristics, form, growth, and physiological aspects which are unique genetic attributes of zebu compared to Bos taurus cattle.…”