SWINE RESPONSES TO CONSTANT AND MODIFIED DIURNAL CYCLIC TEMPERATURES

Ad libitum fed and individually penned crossbred gilts (39 +/- 2 kg) w ere exposed to a constant air temperature of 30.8-degrees-C (CON) and equal-mean diurnal cyclic temperatures cycling from 26-degrees to 33-d egrees-C (RPK) and from 23.4-degrees to 40-degrees-C (RNT). Fluorescen t lighting with an intensity of 800 to 1100 L/m/m2 was provided from 0 600 h to 2100 h. Measurements of feed intake, heat loss rates, water u sage, growth, and ingestion behavior were made for a five-day period a nd replicated six times. Daily average heat loss rates, water usage, a nd feed conversion of the RPK and RNT pigs could be predicted with tho se of the CON pigs. However, daily feed intake and growth of the RNT p igs, 1.56 kg and 0.70 kg, respectively, were reduced (p < 0.01) compar ed to the CON pigs (1.71 and 0.82) and the RPK pigs (1.78 and 0.84). I ngestion patterns of the pigs for all treatments were characterized by a meal size of 160 to 170 g/meal-pig, drink size of 250 to 270 g/drin k-pig, meal frequency of 9 to 11 meals/day, drink frequency of 36 drin ks/day-pig, meal duration of 13 to 14 min/meal, and drink duration of 0.6 min/drink. Hourly feed intakes of the pigs were unevenly distribut ed throughout the 24-h period. Total heat production generally increas ed about two to three hours after an increase in feed intake and decli ned accordingly.