Pig keeping over a fattening period of 14 (standard) or 20 weeks (heavy): effect on growth performance

Two trials were carried out in the research stations of ITP (trial 1) and EDE (trial 2) to quantify growth performances of group housed barrows and gilts over two fattening periods corresponding to production of French standard pigs (S, 14 weeks) or heavy (H, 20 weeks) ones. Average daily gain (ADG) and feed conversion ratio (FCR) were calculated from 28 kg body weight (BW) to slaughter (total), over the first 14 weeks (0-14) for all pigs (H + S), and over the following 6 weeks (14-20) for H pigs. Barrows were fed ad libitum below 70 kg BW, 2.7 kg/d from 70 to 110 kg BW, and 2.9 kg/d thereafter in both trials. Gilts were fed ad libitum from 28 kg to slaughter in trial 1 and restrictively fed like barrows in trial 2. The H pigs were slaughtered at 151 and 142 kg BW in trials 1 and 2, respectively. Corresponding values were 112 and 110 kg BW for S pigs. Differences in gilts’ feeding level between trials 1 and 2 resulted in sex effect on ADG14-20: it was significantly higher in trial 1 (967 vs. 785 g/d for barrows), but not different in trial 2 (770 g/d). Total FCR increased by 0.06 and 0.09 unit per additional 10 kg BW at slaughter in trials 1 and 2 on average, respectively. According to a factorial approach of nutrient requirements, a specific diet could be used above 110 kg with a digestible lysine content lower than 6 g/kg.