Body composition at first heat of gilts exposed to three different feeding regimens

Abstract Text: This study was conducted to evaluate the possibility of increasing body fatness of gilts by nutritional means during rearing. Forty-eight gilts (Danish Landrace x Yorkshire; LY) with an initial BM of 62 +/- 2 kg were selected from 16 litters (3 littermates from each).Gilts were fed individually with one of three diets from 62 to 105 kg LW and then transferred to diets lower in CP and lys. Littermates stratified for BM were randomly allocated to one of three dietary regimens: low protein ad libitum (LPAD) (4.3/3.5 g SID lys/kg feed), moderate protein restriction (MPRE) (5.4/4.3 g SID lys/kg feed) or high protein ad libitum (HPAD) (7.0/5.4 g SID lys/kg feed). The experiment was designed to limit growth by lysine (LPAD), energy (MPRE) or the growth potential of gilts (HPAD). Body water content was measured using the deuterium oxide dilution technique before the dietary intervention were initiated (n=9) and at first heat (n=47). Body contents of fat, protein and ash were calculated using prediction equations developed for LY-gilts by Rozeboom and co-workers and back fat depth was measured at the P2 site. Statistical analysis of fixed effect of treatment was performed using a mixed model to account for repeated measurements. Initially, no differences were observed in body water content or derived contents of fat, protein or ash (P > 0.20). On average gilts initially contained 61.2% water, 11.2% fat, 17.9% protein and 3.4% ash. At first heat the measured water content was lowest in LPAD, highest in MPRE and intermediate in HPAD gilts (P < 0.001), whereas the body fat content was changed inversely as LPAD (26.6%), MPRE (23.1%), and HPAD gilts (25.3%) had highest, lowest and intermediate body fat contents (P < 0.001), respectively. The protein and ash contents were lowest (P < 0.001) in LPAD fed gilts (15.5% and 2.8%, respectively), highest in MPRE fed gilts (16.1% and 3.0%, respectively) and intermediate in HPAD fed gilts (15.8% and 2.9%, respectively). The change in body fatness was supported by measurements of back fat depth, which at first heat was highest (P <0.001) in LPAD gilts (15.1 mm), lowest in MPRE gilts (11.8 mm) and intermediate in HPAD sows (14.3 mm). In conclusion, body fatness of gilts can be increased considerably through dietary means even in breeds that thoroughly have been genetically selected for leanness.

Keywords: body condition; body fatness; dietary composition; gilt rearing; growth performance