Performance evaluation of barrows and gilts of three different sire lines

Abstract Text: Barrows and gilts from three sire lines (n = 240) were measured to evaluate their BW growth, daily feed intake (DFI) and feed conversion. Pigs were weaned at 21 d of age with 8 pigs per pen during the nursery and 4 pigs per pen (1.12 m²/pig) in grow-finishing phase.  The first 3 nursery diets were fed on a feed budget with nursery phase 4 diet fed to d 35 post-weaning.  Grow-finish diets were fed in 6 phases with the first 5 phases fed for 21 d each and the final diet fed until marketing.  Pigs were weighed at 21, 28, 35, 49, 56, 77, 98, 119, 140, and 161 d of age and at close to target final BW of 145 kg.  A Generalized Michaelis-Menten function was fitted to the BW data with 2 pig specific random effects.  The Bridges function was fitted to the DFI data as a function of BW with pen as a random effect.  Data were analyzed using Proc GLM and NLMIXED of SAS. Sire line (SL) and sex by SL interactions were significant (P < 0.03) for nursery ADG and DFI.  Sire line 1 (SL1) and 2 (SL2) pigs had similar d 35  BW ( 27.9 and 28.5 kg) which were greater (P < 0.001) than sire line 3 (SL3) pigs (26.0 kg) due to differences in ADG (603, 615, and 555g/d, respectively) .  Sire line differences existed (P < 0.001) for grow-finish ADG (1005, 968, and 840 g/d respectively), DFI (2.73, 2.66, and 2.27 kg/d respectively), and final BW.  Pigs of SL1 and SL2 had similar ADG and final BW which were greater (P < 0.001) than SL3 pigs. Gilts had lower (P < 0.001) ADG (919 versus 956 g/d), DFI (2.46 versus 2.64 kg/d) and greater gain:feed (0.373 vs 0.362) than barrows.  Overall, ADG increased from weaning to about 122 d of age and then slowly decreased.  The SL3 pigs achieved their maximal ADG at lower BW than SL1 and SL2 pigs.  The ADG had a great increase from weaning to 75 days of age, slowly increased to  maximal ADG at about 104 d of age, and then slowly decreased. Pigs from difference sire lines have substantial differences in growth performance which need to be evaluated relative to the type of production and marketing system.

Keywords: growth functions, pig growth, feed intake