Effects of gonadotropin releasing factor immunological (Improvest??) on carcass characteristics, pork quality, and further processing characteristics of finishing male pigs
The objective of the research was to evaluate a new technology used to suppress testicular function of male pigs using an immunological designed to block the communication of gonadotropin releasing factor (GnRF) with the anterior pituitary gland. This disrupts the production of a number of male sex hormones such as testosterone and androstenone. The reduction of testosterone allows for an increase in hepatic metabolism of skatole. Androstenone and skatole are the two primary compounds associated with objectionable odors and aromas collectively known as "boar taint". Boar taint issues are the one of the key reasons physical castration (surgical castration) has been so widely adopted in United State swine production systems. Improvest?? (Pfizer Animal Health, Kalamazoo, MI) is a 9 amino-acid base pair GnRF conjugate that prevents boar taint in entire male pigs even when allowed to grow to ending live weights over 130 kg. This research used two populations of pigs of PIC genetics (Pig Improvement Company, Hendersonville, TN) divided over three independent experiments. The objectives of the first experiment were to determine if increasing lysine levels in the diets of immunologically castrated (IC) male pigs will increase percent fat free lean and carcass cutability. The objective of the second experiment was to determine if increasing lysine levels in the diets of IC male pigs will affect further processed product characteristics when compared to physical castrates or entire males. Raw materials for this experiment were derived from the same pigs used in the previous experiment evaluating carcass characteristics and cutability. The objectives of the final experiment were to determine if advantages in cutting yields of immunocastrated (IC) males over physical castrates, demonstrated in the first experiment, would persist when pigs were harvested at either 4 weeks (early harvest group) or 6 weeks (late harvest group) post second injection and to evaluate belly quality and bacon processing characteristics of IC males fed a moderate level of dietary unsaturated fatty acids (DDGS). In the first experiment, 96 pigs (16 per treatment) were selected based on ending live weight (weight 48 h prior to harvest) for further analysis. The experiment used four dietary programs differing in percent lysine inclusion where the diets ranged in a low lysine level (0.7% in the late finishing diet) to a high lysine level (1.0% in the late finishing diet). Percent fat-free lean increased 3.7 percentage units in IC males as lysine level was increased from low (56.1% fat-free lean) to high (59.8% fat-free lean) dietary lysine. There were no differences (P > 0.05) among IC males fed low, low/medium, or medium/high lysine levels, but there was a linear increase (P = 0.01) in fat-free lean as dietary lysine level increased. There were no differences in shear force, cook loss, or ultimate pH (P ??? 0.05) among any of the treatment groups. Extractable lipid of loin chops decreased 1.01 percentage units from IC males fed the low lysine diet (2.29%) to the IC males fed the high lysine diet (1.28%). Lean cutting yields and carcass cutting yields were higher in IC males than in physical castrates, but were lower than entire males. There was a linear increase in lean cutting yield (P = 0.05) and carcass cutting yield (P = 0.01) in IC males as dietary lysine level increased. Entire males (2.85 cm) had the thinnest (P 0.05) among physical castrates or IC males regardless of lysine level. There were no differences (P ??? 0.05) in protein content or protein fat-free values in cured and smoked hams among any treatment group. A total of 156 pigs (78 IC males and 78 physical castrates) were used in the second population of pigs. Selection criteria were based on sex and ending live weight where the heaviest 15 pigs within a pen were selected at 4 weeks post-second injection and the remaining 10 pigs in the pen were selected at 6 weeks post second injection. Pigs were harvested at either 4 or 6 weeks post-second injection and within each harvest group pigs were classified as heavy, light, or median weight. There were no differences between IC males and physical castrates for shear force (P = 0.09), ultimate pH (P = 0.57), L* (P = 0.93), a* (P = 0.33), b* (P = 0.31), subjective color score (P = 0.64), or drip loss (P = 0.30). There were no interactions between sex and harvest time (P = 0.99) or between sex and weight category (P = 0.43) or the three-way interaction (P = 0.84) for lean cutting yields. There were also no interactions between sex and harvest time (P = 0.49) or between sex and weight category (P = 0.66) or the three-way interaction (P = 0.28) for carcass cutting yields. Lean cutting yields of IC males (28.84 kg) were 1.20 kg heavier, 2.62 percentage units higher (P < 0.0001), than physical castrates (27.64 kg) and carcass cutting yields were 1.06 kg heavier, 2.27 percentage units higher (P < 0001), for IC males (33.98 kg) when compared to physical castrates (32.91 kg). Bellies from IC males were thinner (P = 0.01) and had wider belly flops (P < 0.0001) than bellies from IC males. Even though cook loss percentage was greater (P < 0.0001) in IC males when compared to physical castrates, cooked yields were not different (P = 0.74) between the two sexes. Over both populations of pigs, immunological castration with Improvest?? does not affect pork quality, improves cutting yields, makes fresh bellies thinner, but does not affect cured product characteristics
