Calcium and phosphorus requirement of swine from weaning to market weight: II. Development of response curves for bone criteria and comparison of bending and shear bone testing.

Abstract

Three trials involving 251 crossbred pigs were conducted to establish response surfaces for effects of Ca/P levels (70, 85, 100, 115 and 130% of NRC [1979] estimated requirements) and time (weaning to market) on bone criteria and to compare bending and shear bone testing. Nine replicates, each consisting of five pigs, were used over the three trials. One pig per replicate was slaughtered every 4 wk following the start of the trials. Third metacarpals and metatarsals (3M) and fourth metacarpals and metatarsals (4M) were collected at slaughter; the bone length, bending or shear stress, and dry, fat-free ash percentage (DFF%) were determined. Most bone criteria increased (P less than .01) at a decreasing rate (P less than .05) in response to increasing dietary Ca/P intake and increased linearly (P less than .01) with time on test, although bone length and stress increased at a decreasing rate with time on test. Asymptotic models relating continuous effects of total Ca + P intake ratio (CAP; expressed as a percentage of NRC) and number of days on test before slaughter to bone measurements were fit to least squares slaughter time by diet means. Bone length and DFF% reached 98% maximum at or near 100% the NRC estimated CAP level; however, to reach 98% of maximum bone shear and breaking stress higher CAP levels were required. Shear testing of bones was more desirable than bend testing as a method of determining bone strength due to reduced variability, better discrimination of Ca/P and time effects and ease of calculation.

Available phosphorus levels in diets for pigs with high genetic potential for lean meat deposition kept in thermoneutral environment from 15 to 30 kg

“…Different authors (Kornegay et al, 1981;Mahan, 1982;Combs et al, 1991) also found that greater bone mineralization occurred at levels greater than those required to maximize performance of pigs. By contrast, data obtained by Ketaren et al (1993) showed that the effects of dietary phosphorus in the bone ash concentration can vary depending on the bone assessed.…”

“…In this case, the bone ash content in the radial and femur of the pigs increased linearly, whereas the ash percentage in the metatarsal did not vary with dietary aP levels. Although the phosphorus requirement of pigs for maximum bone mineralization is higher than those required for maximum weight gain and feed conversion (Kornegay et al, 1981;Mahan, 1982;Combs et al, 1991), it has been suggested the formulation of diets that meet the phosphorus requirement of pigs for maximum weight gain or for the best feed conversion (NRC, 1998;Rostagno et al, 2005).…”

Phosphorus equivalency value of microbial phytase in weanling pigs fed a maize-soyabean meal based diet

“…The tenth ribs were cleaned of all tissues and used for determination of shear force and shear energy as described by Combs et al (1991). Bone ash was determined in a muffle furnace at 600°Cfor 12 h.…”

Digestible phosphorus requirement of grower pigs

“…These reported P requirements were based on a comprehensive review of the North American scientific literature compiled between 1962 and 1991. Apparently, the studies included used corn-soybean meal diets and total dietary P was analysed (Combs et al 1991), and the available P requirement was subsequently estimated (NRC 1998) based on average P availability for ingredients included in the diets. In contrast, digestible P requirement (Jongbloed 1987) may be measured during most experiments, because faecal samples can be easily obtained and used to determine dietary digestible P content.…”