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Phosphorus in Swine. IV. Influence of Dietary Calcium and Phosphorus and Protein Levels on Feedlot Performance, Serum Minerals, Bone Development and Soundness Scores in Boars¹

Virginia Polytechnic Institute and State University, Blacksburg 24061

Abstract

The effects of three dietary Ca and P levels and two protein levels on feedlot performance, serum minerals, bone development and soundness scores were evaluated in two trials with 192 crossbred boars. The following factorial arrangement of treatments was used in each trial: (1) 16–14% protein sequence — 100% of NRC-recommended Ca and P levels for market barrows and gilts; (2) 16–14% protein — 125% Ca and P; (3) 16–14% protein — 150% Ca and P; (4) 18–16% protein sequence — 100% Ca and P; (5) 18–16% protein — 125% Ca and P, and (6) 18–16% protein — 150% Ca and P. There were no overall differences in daily gain, daily feed intake and feed per unit of gain between boars fed diets containing 100, 125 and 150% Ca and P. During the growing phase, daily gain was higher (P<.10) and feed/gain lower (P<.01) for pigs fed 125% Ca and P. Although daily gain favored (P<.01) pigs fed the higher protein sequence during the growing phase, there was no overall difference. Feed/gain was lower (P<.05) during the growing phase for pigs fed the higher protein sequence, but there was no difference during the finishing phase. Dietary Ca and P x protein interactions were not significant. Serum P decreased (P<.01) as dietary Ca and P increased, with no difference in serum Ca and Mg, and there was no effect of protein sequence. Values for metacarpal parameters increased as dietary Ca and P level increased, although the magnitude of the increase was small. Except for length and ash values which were lower for pigs fed the high protein sequence, the values for metacarpal parameters were not influenced by protein sequence. Pad, soundness and foot scores and toe lesions and measurements were not generally influenced by dietary Ca and P or protein level. These results provide limited evidence that feedlot performance and bone development of boars were improved when 125% NRC Ca and P levels were fed, but that overall soundness and foot scores and toe lesions and measurements were unaffected. There was little support for the feeding of higher Ca and P levels. With the exception of feed efficiency during the growing phase, no parameter was improved by the feeding of the higher protein sequence. There appears to be no interaction between dietary Ca and P and protein levels.

¹ Appreciation is expressed to Charlie Babb and Carl Eure for feeding and caring for the pigs; to Helen Bartlett for analytical work; to Cindy Atkins for typing the manuscript; to Smith-Douglass, Division of Borden Chemical, Borden, Inc. for supplying ingredients; and to L. B. Allen, J. H. Carter and C. C. Brooks for evaluating the soundness of the pigs.

² Dept. of Anim. Sci.

³ Tidewater Research and Continuing Education Center.

⁴ Dept. of Agr. Eng.