289 Zinc Source and Genotype Influenced the Growth Rate and Carcass Characteristics of Commercially Housed Fattening Pigs

Abstract

Abstract The study evaluated the effects of zinc source on the growth performance and carcass characteristics of commercially housed fattening pigs of different genotypes. The study design was a randomized complete block with 4 experimental treatments and 11 replicate pens per treatment (20 pigs/pen, 220 pigs/treatment). Treatments were arranged in a 2 x 2 factorial, with the factors genotype (“A” or “B”) and zinc source (inorganic, ZnO or hydroxychloride, IBZ). All pigs were fed the same feed budget: phase 1, 25 kg/pig; phase 2, 80 kg/pig; phase 3, 90 kg/pig; phase 4, 75 kg/pig. Diets were corn-soy, and the zinc was included in the micropremix to deliver a total of 100 ppm Zn from ZnO and 80 ppm Zn from IBZ. The genotypes evaluated were selected by the commercial facility. Body weight (BW) and feed disappearance of each pen were recorded every third week to calculate average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR). In a subset of pigs, carcass cut-out measurements were obtained from the processor (80 pigs/treatment). Data were analyzed using PROC GLIMMIX in SAS according to a randomized design with factorial treatment arrangement. Zinc source influenced growth, with pigs fed IBZ having increased market BW (+0.7 kg, P < 0.05) and ADG (+15 g/d, P < 0.05), and a tendency for increased carcass weight (+0.6 kg, P = 0.08), compared with pigs fed ZnO. There were no interactions between genotype and zinc source for any growth or carcass variables. Genotype B pigs had increased market BW (+2.0 kg P < 0.05), ADG (+26 g/d, P < 0.05) and ADFI (+60 g/d, P < 0.05) than genotype A pigs. Furthermore, genotype B pigs had increased carcass weight (+0.9 kg, P < 0.05), carcass length (+0.2 inches, P < 0.05), belly weight (+220 g, P < 0.05) and decreased ham weight (-140 g, P < 0.05), muscle and fat depth (P < 0.05), compared with genotype A. Carcass quality metrics were also affected by genotype, where B pigs had decreased Minolta L (P < 0.05), firmer texture (P < 0.05), greater pH (P < 0.05) and less drip loss (-1%, P < 0.05) than genotype A. In conclusion, providing fattening pigs a hydroxychloride zinc source improved growth rate leading to heavier market BW and carcass weights compared with pigs fed ZnO irrespective of genotype. Genotype also significantly impacted growth rate, carcass characteristics and quality metrics.