Growth performance and digestive and metabolic responses of gilts penned individually or in groups of four

Two experiments were conducted to identify factors involved in the growth r etardation of pigs housed in groups. In each experiment, 60 gilts were allo tted to two treatments in a randomized complete block design. Twelve gilts were penned individually with one feeder, one waterer, and a space allowanc e of 1.5 m(2) per pen. Forty-eight gilts were allocated to 12 groups of fou r and penned together with four feeders, four waterers, and a space allowan ce of 6 m(2) per pen. In Exp. 1 there were 60 growing gilts (initial and fi nal BW of 17.9 and 50.8 kg, respectively), and in Exp. 2 there were 60 fini shing gilts (initial and final BW of 46.0 and 118.3 kg, respectively). In E xp. 1 there was a trend (P < .10) toward greater final BW, ADG, and average backfat thickness of gilts penned individually. Apparent digestibilities o f DM, CP, and energy tended (P < .10) to be greater and plasma NEFA concent rations were lower (P < .05) for gilts penned individually. Plasma concentr ations of urea and glucose were similar between treatments. In Exp. 2, ADG was greater (P < .05) and there was a trend (P < .10) for greater final wei ght, ADFI, loin weight, and primal cut weight of gilts penned individually. Apparent digestibilities of DM, CP, and energy and the plasma concentratio ns of urea, glucose, and NEFA were similar in both treatments. In summary, growing gilts penned four per group had reductions in daily gain, backfat t hickness, and apparent digestibilities of DM, CP, and energy and increases in plasma NEFA concentrations. Finishing gilts penned four per group had re ductions in daily gain and feed intake with no changes in apparent nutrient digestibilities or plasma metabolite concentrations compared to individual ly penned gilts.