Availability of phosphorus in soyabean meal and field peas for growing pigs.

Abstract

Proc. Aust. Soc, Anim. Prod. Vol. 18 AVAILABILITY OF PHOSPHORUS IN SOYABEAN MEAL AND FIELD PEAS FOR GROWING PIGS P.P. KETAREN*, E.S. BATTERHAM* and D.J. FARRELL** Most of the phosphorus (P) recomme ndations for pigs are based on total P as values for available P have not yet'been fully established. A slope-ratio assay technique has been developed by Cromwell (1980) to determine available P in feed ingredients for pigs. In this assay, test meals are evaluated relative to the availability of monosodium phosphate (taken as 100% P availability). Bone bending moment (BBM) is used to assess response rather than growth rate as the former is a more sensitive parameter of P metabolism. Linearity of response is necessary for the assay to be valid. The objective of this experiment was to determine the availability of P in soyabean meal and, field peas using this assay. Sixty female pigs averaging 20 kg were allotted to ten different diets and fed three times maintenance requirement for energy over a 35 day period. Three level8 of P (3.0, 3.5 and 4.0 g/kg) from monosodium phosphate, were added to a basal soyabean meal sugar-based diet (containing 2.5 g/kg P) to determine the response to P. Similarly, three levels of either soyabean meal or field peas were incorporated into the basal diet to supply the same levels of total P as Metacarpal bones were collected at the contributed by monosodium phosphate. end of the experiment for BBM determinations. BBM of the metacarpal bones responded linearly to the diets containing monosodium phosphate (P < 0.01) and field peas (P < 0.05) but not to the diets containing soyabean meal (Table 1). Table 1 BBM (kg-cm) of metacarpal bones as affected by dietary P levels For field peas, the availability of P was 47% which is vegetable protein values (Cromwell 1980). For soyabean not calculated as the response was non linear. This linear response to P may have been due to the very low contributed by the soyabean meal. A greater intake increasing the inclusion level of soyabean meal or by libitum. This may make the response more sensitive. CROMWELL, G-L. (1980). Feedstuffs 52 (9): 38. high compared to other meal, the results were lack of a significant levels of available P could be achieved by feeding the pigs ad * North Coast Agricultural Institute, Wollongbar, N.S.W. 2480. ** Department of Biochemistry, Microbiology and Nutrition, University of New England, Armidale, N.S.W. 2351. 503