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Phosphorus in Swine. VI. Utilization of Nitrogen, Calcium and Phosphorus and Reproductive Performance of Gravid Gilts Fed Two Dietary Phosphorus Levels for Five Parities

Virginia Polytechnic Institute and State University^,3, Blacksburg 24061

Abstract

Sixty-two gilts were paired at breeding and assigned randomly to one of the following dietary treatments: (1) low P or (2) high P during gestation and lactation. Two sets of diets (A and B) were formulated; each set to provide a low (10 g) and high (15 g) daily P intake (equal Ca daily intake, 15 g) when fed at 1.82 and 2.27 kg daily, respectively for sets A and B. Females were fed 1.82 kg daily of set A diets during the first 11 wk of gestation, 2.27 kg daily of set B diets for the next 3 wk and 3.34 kg of the appropriate set B diets containing 20% wheat bran until farrowing, at which time the bran was gradually removed from set B diets and the feed level increased to 4 kg daily until weaning. The proportions of defluorinated phosphate and limestone were varied to provide the appropriate level of Ca and P (low and high). At approximately 5 wk before farrowing at each parity, up to 12 females from each group were used in Ca, P and N balance trials that lasted about 2 wk. Dietary P intake did not affect the apparent absorption and retention of N and Ca; 88% of the consumed N was absorbed and one-half of the absorbed was retained, and 37% of the Ca was absorbed and 94% of the absorbed was retained. Females fed the higher P intake, although excreting higher levels of P in the feces and urine, absorbed and retained a larger amount of P; but the low P-fed sows were more efficient in the retention of P when expressed as a percentage of intake or as a percentage of the absorbed P. With the exception of average total litter weight at birth that favored high P-fed sows, live, dead and total pigs at birth, average birth weight and breeding performance were not statistically different between P levels. Except for the first parity, most characteristics favored sows fed the higher P intake. Serum Ca and P levels and hair P concentration were similar between P levels. Hair Ca concentration, however, was higher for the high P-fed sows. Sows fed the higher daily P intake retained more P and there was a trend for better farrowing performance. However, breeding performance, serum Ca and P levels, hair P concentrations and Ca and N balance were similar between dietary P intakes. These results would support current National Research Council-suggested Ca and P levels for sows.

¹ Dept. of Anim. Sci.

² Blue Ridge Community College, Weyers Cave, VA 24486.

³ Appreciation is expressed to John Blaha and Fred Barlow for feeding and caring for the sows, to James Hedges and Helen Bartlett for laboratory analysis, to Sharon Crews and Susan Arthur for statistical analysis, to Cindy Eaton for typing the manuscript and to Agricultural Processing Co., Salem, VA and Smith-Douglas, a Division of Borden Chemical, Borden, Inc., Norfolk, VA for ingredients and to the Virginia Pork Industry Commission for financial support.