Evaluation of the rates of mineral accretion per kilogram of body weight gain and net energy intake for two genetic lines of barrows and gilts from 20 to 125 kilograms body weight1

Two genetic lines of barrows and gilts with different lean growth rates were used to determine BW and mineral growth from 23 to 125 kg BW. The experiment was a 2 × 2 × 5 factorial arrangement of treatments conducted in 2 replicates. Six pigs from each sex and genetic line were killed at approximately 25-kg intervals from 23 kg BW to 125 kg BW. At slaughter, tissues were collected and weighed. All components were ground and frozen until analysis for mineral, lipid, and protein content. The allometric function, mineral mass = a BWb, provided the best fit to the data. The linear form of the allometric equations was evaluated for the interactions of the regression coefficients with genetic lines and sex. Daily NE intakes were estimated based on the daily protein and lipid accretion rates. Allometric growth coefficients for the mineral mass were different for each sex and genetic line for Ca (P < 0.05). Interactions of BW and genetic line were found for Se, Zn, S, and K. The high-lean gain pigs had greater rates of mineral accretion per predicted unit of energy intake. In several cases, the predicted ratio of mineral accretion to NE intake were from 10 to 20% greater for the high-lean than the low-lean gain pigs at 25 kg BW and increased to 20 to 50% from 100 to 125 kg BW. These results support the need for genetic population-specific mineral nutrient recommendations.