Effects of additional organic micro-minerals and methionine on carcass composition, gait score, bone characteristics, and osteochondrosis in replacement gilts of different growth rate

Abstract

Osteochondrosis (OC) is a multifactorial defective endochondral ossification that causes lameness and early culling in gilts and sows. Previous research suggested that nutrition and growth rate could influence OC development and progression. As part of a broader study [n = 360 gilts; 28.8 ± 8.8 kg body weight (BW)] designed to evaluate the effect of 4 dietary treatments: 1) basal diet (CON); 2) CON plus organic micro-minerals (MIN, copper, manganese and zinc at 10, 20 and 50 mg/kg, respectively); 3) additional methionine (MET, at 102% methionine:lysine); and, 4) the organic micro-minerals plus the additional methionine (MM), on lameness and performance, a sub-sample of 40 heavy replacement gilts (10 gilts/treatment, 171.5 ± 8.1 kg of BW) was used. Within treatment, gilts were classified for final average daily gain (ADG) as low (LG, 838 ± 36.3 g/day; n = 20) or high (HG, 922 ± 31.1 g/day; n = 20). Dietary treatment and growth classification were the fixed effects to evaluate gait, OC, tibia bending measures, metacarpal mineralization; and using computerized tomography, the carcass composition, bone size, and whole bone density (WBD). The WBD was expressed as volume of Hounsfield values (HU), where higher values indicate increased density. A porcine reproductive and respiratory syndrome virus outbreak occurred during this trial. It differentially affected MM gilt performance and consequently may have influenced the results for this treatment. Gilts fed MIN diet had 0.75 cm larger tibia than CON (P < 0.05), and 10% increase of WBD > 140 HU compared to CON and MET (P < 0.05). The volume of high dense bones (> 1000 HU) was also increased in MIN and MET compared with CON (P < 0.05). Tibia bending moment and breakage strength were greater (P < 0.05) in MIN than in CON, with MET and MM intermediate. Metacarpal ash, Ca, and P content, but not proportions, were higher in gilts fed MIN than CON (P < 0.05). Total score of OC lesions was lower in MM gilts compared to CON (P < 0.05). The OC total score increased with ADG from 35.8 to 109.8 kg BW (R2 = 0.10; P < 0.10). However, between 109.8 and 171.5 kg BW OC score increased with decreased ADG (R2 = 0.14; P < 0.05). In conclusion, supplementing growing gilts with MIN enhanced bone strength and bone density, MET increased the proportion of highly dense bone (>1000 HU), and MM dietary treatment reduced OC lesion score compared with CON.