Effect of restricted growth rate and elevated levels of minerals and vitamins on feet and leg characteristics, soundness scores and metacarpal and metatarsal characteristics of growing boars

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Virginia Polytechnic Institute and State University

The effects of dietary energy level (ad libitum vs 75% of ad libitum) and mineral-vitamin intake (100 vs 150% NRC recommendations) on foot and leg development, incidence and severity of foot lesions, soundness scores and metacarpal and metatarsal characteristics of growing boars was studied. Boars assigned to the dietary treatments at 5 wk of age were serially necropsied beginning at 120 d of age. Foot and leg characterization was carried out at four periods (35, 122, 209 and 290 d of age) and at necropsy. Bone samples were obtained at necropsy.

Toe measurements increased over time with outside toes larger than inside toes. The hind outside toe was consistently larger than the other toes. Mineral-vitamin level had little effect on toe measurements, while ad libitum feeding produced larger feet and legs as compared with limit-fed boars at an equal age. Correction for body weight differences removed the energy level differences and often produced trends favoring the limit-fed boars. Dietary treatment had little effect on the incidence and severity of pad or horn lesions, however, restricting feed intake produced boars more structurally sound in appearance.

Bone size increased with age, while bone ether extract decreased and bone ash content increased. As age increased, Ca content of bone ash increased, P level remained unchanged and Mg, Cu, Zn, Fe and Mn levels decreased. Metatarsals were longer and heavier than metacarpals. Percentage of bone ether extract increased with ad libitum feeding while the 150% mineral-vitamin level resulted in increased percentage bone ash. At an equal age, bone size and mechanical characteristics were greater for ad libitum-fed boars, however, weight-correction produced trends favoring limit-fed boars. Greater bone wall thickness and mechanical characteristics resulted from elevated dietary mineral and vitamin levels.

Little consistent correlation was apparent between toe area or volume and the incidence of foot lesions or among the incidence of lesions at the various locations on the front or hind feet.