Effects of increasing lysine on carcass composition and cutting yields of immunologically castrated male pigs

Abstract

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would increase percentage fat free lean and carcass cutting yields when compared with physical castrates. The anti-gonadotropin-releasing factor (GnRF) immunological product (Improvest, Pfizer Animal Health) is used worldwide to immunologically castrate entire male pigs to control boar taint and take advantage of the inherent ability of the entire male to deposit more muscle, less fat, and grow more efficiently than physically castrated males. The immunization process essentially allows the pig to grow as an entire male pig for most of its life and then removes any boar odor (boar taint) before slaughter. Reported lean meat advantages may also provide economic benefits to the domestic meat industry. Approximately 1,200 male pigs [physical castrates, IC males, and entire males] were each assigned to 1 of 4 diet programs which differed in lysine content. In each case, lysine was fed in a conventional step-down program that culminated with the following concentrations in the late finishing diet: physical castrates fed low lysine (0.7%), IC fed low lysine (0.7%), IC fed low/medium lysine (0.8%), IC fed medium/high lysine (0.9%), IC fed high lysine (1.0%), and entire males fed high lysine (1.0%). At 25 wk of age (5 wk post-second injection), pigs were individually weighed and the 2 pigs (n=96) in each pen closest to the median pig BW were selected and slaughtered. The right side of each carcass was dissected into soft tissue, skin, and bone. Proximate composition was determined on the soft tissue to determine percentage fat-free lean. The left side of each carcass was weighed and initially fabricated into ham, loin, belly, and whole shoulder. Each primal piece was weighed again and further fabricated into respective subprimal cuts. Immunological castration did not change (P>0.05) shear force values or ultimate pH when compared with either physical castrates or entire males. Marbling appeared to decrease as dietary lysine was increased among IC males. As expected, IC males had a greater (P<0.05) percentage fat-free lean than physical castrates but less (P<0.05) than entire males. Immunologically castrated males fed diets with medium/high and high lysine had greater (P<0.05) lean cutting yields and carcass cutting yields than physical castrates. Lean cutting yield and carcass cutting yields appeared to increase as dietary lysine was increased among IC males. Overall, immunological castration improved carcass cutability, increased percentage fat free lean, and had no effect on pork quality when compared with physical castrates.

Características químicas y sensoriales de la carne de cerdo, en función del consumo de dietas con ractopamina y diferentes concentraciones de lisina

“…Efecto de la concentración de lisina y de la adición de ractopamina en las características sensoriales de la carne de cerdo £ Estudios enfocados a incrementar la productividad en función de la cantidad de carne producida, normalmente evalúan el efecto de concentraciones elevadas de proteína y lisina, ya que tienden a optimizar la eficiencia alimenticia. Desafortunadamente, los niveles elevados de lisina y proteína, tienen el efecto inverso en calidad de la carne, ya que tienden a reducir linealmente la GIM y a aumentar la fuerza de corte del lomo (17,42) . Por ejemplo, Apple (43) encontró que en dietas con RAC y una elevada concentración de lisina (2.4 ó 3.1 g lisina/Mcal), se redujo la GIM y aumentó la fuerza de corte.…”

“…Unfortunately, high lysine and protein levels have an inverse effect on meat quality, producing a linear decrease in IMF and an increase in loin shear force (17,42) . For example, diets containing RAC and a high lysine concentration (2.4 or 3.1 g lysine/Mcal) reduced IMF and raised shear force (43) .…”

Castration of male livestock and the potential of immunocastration to improve animal we

“…Thus immunocastrates could have a higher anabolic lean growth potential than surgical castrates even though testosterone production is compromised, provided their nutritional needs are met. This potential change in anabolic growth potential and nutritional requirements was investigated by increasing dietary lysine in the diets of immunocastrates, showing that their cutting yields improved and backfat thickness decreased in comparison to surgical castrates (Boler et al, 2011). Responses to varying dietary protein content also differed between immunocastrates and intact males with regards to backfat deposition, also indicating a possible difference in anabolic growth potential and nutritional requirements between immunocastrates and intact boars (Needham & Hoffman, 2015a).…”

Carcass traits and cutting yields of entire and immunocastrated pigs fed increasing protein levels with and without ractopamine hydrochloride supplementation1–3

“…It has been made evident that dietary lysine is important to optimize the carcass characteristics and yields of finisher pigs when fed with and without RAC (Apple et al, 2004a;Webster et al, 2007). Boler et al (2011) has also shown that immunocastrates (ic) should be fed at a higher lysine level than surgical castrated pigs in order to increase carcass cutting yields and decrease backfat thickness.…”