Effect of season (summer vs. fall) and diet nutrient density on performance and carcass characteristics of growing-finishing swine

摘要

A study was conducted to evaluate the effects of rearing environment/season (hot, humid/summer vs. thermoneutral/fall) and dietary nutrient density (high energy/high lysine vs moderate) on performance and carcass lean content of growing-finishing swine (32 to 112 kg). For each of two consecutive years, two trials, each with 80 pigs, were conducted - one during the summer and the other during the fall. The trials were conducted in NH Florida (31 deg N); average daily low and high temperatures, and average RH for yr 1 and 2 were 21/21 deg C and 32/33 deg C, and 83/78 percent for summer; 9/7 deg C and 22/21 deg C, and 79/76 percent for fall. Diets were corn and soybean meal based; the high energy/high lysine diets (H) were additionally supplemented with L-lysine HCl (at 0.15 percent of the diet) and feed fat (at 6 percent). The H and moderate (M) diets averaged 3.6 and 3.3 meal ME/kg, respectively. Ten pigs were allotted to each pen and assigned to one of two dietary treatments. Pigs were housed ina curtain-sided building in pens with, solid concrete floors. Pigs had access to water for evaporative cooling. Floor space was 0.72 m~2 per pig. Pigs reared during summer grew, on average, 6 percent slower (P<.001) and had 8 percent lower lean gain per day (P<.001) than pigs reared during fall. Pigs fed the H diets grew 5 percent faster (P<.001) than pigs fed the M diets; lean gain per day was also greater (P<.05). Carcass lean content was slightly affected by season (P=.11) but not by diet type (P>.10). Average feed-to-gain ratio for pigs fed the M diets was slightly poorer for summer vs fall, whereas it was not affected by season for pigs fed the H diets (SxD, P=.11; M vs H, P<.001). Detrimental effects due to season occurred mostly in pigs during finisher II phase (82 to 112 kg). Thus, the feeding of H diets resulted in equal improvements during summer and fall for growth and lean gain, and tended to result in a greater improvement in feed-to-gain during summer than during fall (12 vs 9 percent