Effect of different dietary CP levels on the growth, nutrient utilizationand carcass characteristics of finishing barrows and gilts reared in phasefeeding regimen.

摘要

This experiment was to investigate the effects of different crude protein (CP) sequences on growth performance, nutrients utilization and carcass characteristics of finishing barrows and gilts under three phase feeding regimen. A total of 120 finishing pigs (LandracexLarge WhitexDurox) averaging 53.3 +/-0.91 kg of body weight and 30 pigs (averaging 52.5 +/-0.57 81.8 +/-0.79 and. 100.7 +/-0.89, respectively) were assigned to the feeding and the metabolic trial, respectively. Experiment was arranged as a 2x3 factorial design, barrows and gilts and three dietary treatments. Each treatment had four replicates with five pigs per replicate. Finishing period (53 to 107 kg) was divided into three phases (53 to 69 kg, 69 to 88 kg and 88 to 107 kg). Dietary treatments included 1) 17%-15%-13% (high CP), 2) 16%-14%-12% (medium CP), 3) 15%-13%-11% (low CP) sequence for finishing period. During the overall experimental period (53 to 107 kg), there was no interaction between sexes and dietary CP levels on growth performances. Barrows consumed more feed (p <0.01) and grew faster (p <0.01) than gilts did. ADG of pigs fed on high dietary CP feeding group was improved significantly than that of pigs fed on low dietary CP feeding group (p <0.05). Average values of essential amino acids (EAA), non-essential amino acids (NEAA) and total amino acids digestibilities were generally not influenced by dietary CP levels and sexes. However, fecal daily nitrogen (N) excretion averaged over all periods was significantly higher in high dietary CP feeing group than in medium and low dietary CP feeding groups (p <0.05). Averaged blood urea nitrogen (BUN) concentration was greater (p <0.05) in barrows than in gilts and was increased as dietary CP concentration increased (p <0.05). Backfat (BF) thickness was greater in barrows than in gilts (p <0.05). Longissimus muscle area (LEA) was greater in gilts than in barrows (p <0.01) and was greater in high and medium dietary CP feeding regimens than in low dietary CP feeding regimen (p <0.05). It is concluded that 16%-14%-12% dietary CP sequence is desirable in respect of economics and environment for practical three phase feeding regimen for gilts and barrows during finishing period.