Marongiu, Maria Laura and Dimauro, Corrado (2009) Short and long high ambient temperature exposure differently affect plasma luteinizing hormone and ultrasound-assessed ovarian dynamics of laying hens. In: Prospects of world poultry: a Mediterranean perspective: 2nd Mediterranean Summit of WPSA, 4-7 October 2009, Antalya, Turkey. Beekbergen, World Poultry Science Association. p. 123-126. Conference or Workshop Item.
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In order to clarify the mechanism involved in the reproductive failure associated with heat stress and to test in vivo the effect on ovarian function, 42 White Leghorn laying hens were separated into two equal groups and individually caged in two environmentally controlled chambers. One group was exposed daily for 12 h and for 15 d to an ambient temperature of 37°C. The second group was maintained under thermoneutral conditions (23°C) and served as control. Body temperature was recorded daily and heparinized blood samples were drawn at d 0, 1, to determine the effect exerted by a short heat exposure, and every 3 d. Plasma LH levels were assayed by RIA. At d 1 the ovary of half of the birds in each group was examined by means of real time B-mode ultrasound scanning to characterize large follicles (LF; diameter greater than 10 mm) and the same procedure was repeated at d 6 and 15. Short and long heat exposure caused significant hyperthermia. Ultrasound images revealed a significant reduction of LF number both at d 6 and 15 whereas the acute thermal stress, as assessed 1 d after starting the temperature treatment, did not adversely affect this ovarian trait. Decreased plasma LH was detected 24 h after exposing the birds to heat stress. In contrast, no significant change was found in LH concentrations during d 3, 6, 9, 12 and 15. The reduction in the number of LF observed after 6 d of heat stress and maintained until the end of the experiment at d 15, was not accompanied by a decline in plasma LH, suggesting a possible direct debilitating effect of high ambient temperature on ovarian function of domestic birds. The ultrasonography, representing a non-invasive, rapid, reliable method for studying reproductive efficiency also in the hens, could be advantageous for developing new management strategies to maximize production.
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