Effects of Solar Radiation and Feeding Time on Behavior, Immune Response and Production of Lactating Ewes Under High Ambient Temperature

Abstract

A 6-wk trial was performed with 40 late-lactation Comisana ewes, which were either exposed to or protected from solar radiation and fed either in the morning (EXPM, PROM) or afternoon (EXPA, PROA) during summer in a Mediterranean climate. Behavioral traits of ewes were recorded once per week from 0800 to 2000 h. Rectal temperature (RT) and respiration rate (RR) were measured twice weekly at 1430 h. The phytohemagglutinin (PHA) skin test was performed to induce nonspecific delayed-type hypersensitivity at d 10, 20, and 32 of the experiment. Jugular blood samples were taken from ewes at the beginning and at d 21 and 42 of the experiment. Ewe milk yield was recorded daily. Individual milk samples were analyzed weekly for milk composition, coagulating properties, somatic cell count (SCC) and polymorphonuclear neutrophil leukocyte counts (PMNLC) and every 2 wk for bacteriological characteristics. Solar radiation and the interaction of solar radiation x time of feeding had significant effects on rectal temperatures. EXPM ewes had higher rectal temperatures than EXPA ewes, which in turn exhibited higher RT compared with PROM and PROA ewes. EXP groups also had significantly higher respiration rates than PRO groups. Immune response was lower in EXPM ewes at d 10 and in EXPM, EXPA, and PROM animals at d 20 compared with PROA ewes. Exposure to solar radiation resulted in decreased plasma concentrations of alanine amino-transferase, alkaline phosphatase, potassium, and magnesium, as well as in increased levels of nonesterified fatty acids and aspartate amino-transferase. Milk yield and composition were not changed by exposure to solar radiation and time of feeding, but the EXPM treatment resulted in lower yields of casein and fat and reduced clot firmness compared with the three other treatments. Milk SCC was similar across treatments, but PMNLC was higher in EXPM than in PROM and PROA milk. EXPM animals also had the greatest amounts of total and fecal coliforms and of Pseudomonadaceae as well as the highest number of mastitis related pathogens in their milk. Results suggest that provision of shaded areas can play a major role in helping lactating ewes to minimize the adverse effects of high ambient temperatures on thermal balance and energy and mineral metabolism. Changing the time of feeding to late afternoon may be beneficial to exposed ewes in lowering their heat loads during the warmest hours of the day, thereby reducing the detrimental impact of thermal stress on immune function and udder health.

Effect of barn airspace temperature on composition and technological parameters of bulk milk produced by dairy cows of Czech Fleckvieh and Holstein breeds

“…As mentioned by Daviau et al (2008), the shorter RCT was associated with a decrease in P content and also of casein. It was found out in this study that lower values of RCT were associated with a lower content of protein above all in the summer season; however, our results do not correspond with data published by Jõudu et al (2008); Ikonnen et al (2004) and Sevi et al (2001) who obtained opposite results. This could be partly explained on the base of high summer temperatures recorded in our study.…”

“…Dolejš et al (1996) found also the milk fat content depression with air temperature increase. Sevi et al (2001) found high ambient temperatures to adversely aff ect the yield and cheese-making parameters of milk by the clotting time and the rate of clot formation and decreasing clot fi rmness. The photoperiod (i.e.…”

Metabolic and hormonal acclimation to heat stress in domesticated ruminants

“…The values of THI above which ewes start to suffer from heat stress seem to be quite different among breeds (Finocchiaro et al, 2005). Solar radiation seems to have a limited 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). Even goats are affected by heat stress and responded by reducing milk yield and the content of milk components (Olsson and Dahlborn, 1989).…”

Effects of Night Grazing, Watering Regime, Time of the Day and Season on Respiration Rate and Rectal Temperature of Sudan Desert Sheep Ewes.

“…might be a reflection of the diurnal fluctuations of the ambient temperature (Table2.) and if the temperature drops at night below 21ºC for 3-6 h, the animal could sufficient opportunity to lose at night all the heat gained from the previous day (Igono et al, 1992;Muller et al, 1994;Sevi et al, 2001). However, night temperatures during these trials have been recorded.…”