In global swine production systems where immunological castration is used to control boar taint, pigs physiologically function as entire males for a large portion of their lives and then transition to become more like a castrate after immunization. Historically, most studies which have compared the performance of immunologically castrated (IC) males with physical castrates or intact boars have used the same diet (usually barrow diet) with equal levels of lysine. Therefore, the lysine requirement of IC male pigs is not known. The objective of this study was to determine the effect on performance characteristics of IC male pigs using different levels of lysine in the diets. Male pigs (n = 1174) were raised in a commercial finisher and randomly assigned to 6 treatment groups: physical castrates (barrows) fed a standard lysine level diet for barrows (T01), IC pigs fed a standard lysine level for barrows (T02), IC pigs fed a medium low lysine diet (T03), IC pigs fed a medium high lysine diet (T04), IC pigs fed a high lysine diet (T05) and intact males fed a standard lysine level for intact males (T06). The lysine level fed to groups T01 and T02 were the same as were the lysine levels fed to groups T05 and T06. Pigs were housed approximately 25 to the pen with 8 pens per treatment group. Pen was the experimental unit. The 160 d feeding period was divided into 5 phases: nursery [Day 0 (weaning) to Day 55], grower (Day 55 to 76), developer (Day 76 to 94), finish 1 (Day 94 to 122) and finish 2 (Day 122 to 160). Gonadotropin-releasing factor conjugate was administered via subcutaneous injection to groups T02, T03, T04 and T05 on Days 94 and 122. Pigs were commercially harvested on Day 162, 163 and 177.
The average daily gain (ADG) of T04 pigs (0.79 kg) was significantly (P < 0.05) greater than that of T01 (0.75 kg) and not different (P > 0.05) from T06 (0.78 kg). Furthermore, the feed conversion efficiency (FE) of T04 pigs (2.41 kg feed/kg gain) was significantly (P < 0.05) better than that of T01 pigs (2.66 kg feed/kg gain) and not different (P > 0.05) from that of T06 (2.24 kg feed/kg gain). The medium-high lysine diet (T04) provided the best combination of ADG and FE within the IC male groups, also carcass quality and % carcass lean.
SS Dritz, MD Tokach, RD Goodband, J M DeRouchey, JL Nelssen, DM Meeuwse, VL King, PL Runnels and JP Crane. Effects on performance characteristics of immunologically castrated male pigs using different levels of lysine in the diets. 2011. Journal of Animal Science, 89, E-Suppl. 2, page 68.