Growth performance of immunologically castrated (with Improvest) barrows (with or without ractopamine) compared to gilt, physically castrated barrow, and intact male pigs

Abstract

The study used a randomized complete block design (blocking factor was date of start on test) with 5 treatments: 1) physically castrated barrows (PC), 2) intact males (IM), 3) gilts (G), 4) immunologically castrated barrows (IC), and 5) immunologically castrated barrows fed ractopamine at 5 mg/kg (IC+RAC). The study used 192 pigs and was performed from the 16 wk of age (67.2 ± 2.52 kg BW) to a pen mean BW of 132.5 ± 3.60 kg. For IC+RAC, ractopamine was fed for the final 23 d of the study. Pigs were housed in groups of 4 (10 groups for PC, IM, G, and IC and 8 groups for IC+RAC) in a finishing building at a floor space of 1.18 m(2)/pig. Diets were formulated to meet requirements of IM except that the diet for the IC+RAC fed during the ractopamine feeding period was formulated to meet requirements of pigs on that treatment. Pigs had ad libitum access to feed and water throughout the study period and were individually weighed at the start, wk 2 and 4, and subsequently every week until the end of study. For the overall study period, IC had greater (P ≤ 0.05) ADG than the other genders (1,150, 1,024, 1,064, and 954 g/d for IC, PC, IM, and G, respectively; SEM = 25.8) and required fewer days to reach slaughter weight than the other genders (58.1, 61.6, 61.6, and 66.5 d for IC, PC, IM, and G, respectively; SEM = 1.26). Overall ADFI was less (P ≤ 0.05) for IM and G than IC and PC, which were similar (P > 0.05) in this respect (3.11, 3.06, 2.68, and 2.75 kg/d for IC, PC, IM, and G, respectively; SEM = 0.061). Overall G:F was greater (P ≤ 0.05) for IM than the other genders; IC had greater overall G:F than PC and G, which were similar in this respect (0.371, 0.335, 0.397, and 0.347 kg/kg for IC, PC, IM, and G, respectively; SEM = 0.0068). Immunologically castrated barrows had greater (P ≤ 0.05) ADG (30.7%) and ADFI (22.5%) than PC from the second week following the second Improvest dose to the end of the study. During the ractopamine feeding period, IC+RAC had greater (P ≤ 0.05) ADG (11.6%) and G:F (17.3%) than IC. The results of this study confirmed previously observed gender differences and effects of ractopamine on growth performance and that IC grew faster and had greater feed efficiency than PC during the study period.

Ractopamine supplementation improves leanness and carcass yield, minimally affecting pork quality in immunocastrated pigs

“…These steroids have anabolic effects that stimulate muscle and bone growth, nitrogen and phosphorus retention, and cause a redistribution of nutrients, resulting in better feed conversion, lower backfat thickness and increased lean tissue of intact male carcasses compared to castrates or females (Squires, 2011). In this study, in the time period from the second immunization dose at d 137 to d 164, there was no increase in ADFI of immunocastrated pigs, which was reported by Puls et al (2014). However, other authors (Rikard-Bell et al, 2009;Fàbrega et al, 2010) have reported an increase in ADFI in immunocastrated males.…”

Comparison among gilts, physical castrates, entire males, and immunological castrates in terms of growth performance, nitrogen and phosphorus retention, and carcass fat iodine value1

“…Several studies have evaluated growth performance among the 4 sexes under group-housing conditions (Fábrega et al, 2010;Weiler et al, 2013;Puls et al, 2014). Since this was a metabolism experiment, pigs were housed individually.…”

Effects of immunocastration and time after second Improvest dose on adipose tissue fatty acid profile of finishing barrows

“…Diets fed during the study were similar to those described by Puls et al (2014) and were formulated to meet the nutrient requirement of intact males as proposed by NRC (2012). Briefly, diets were based on corn and soybean meal and did not contain ethanol coproducts.…”