Ractopamine hydrochloride and the environmental sustainability of pork production

Abstract

These experiments were conducted to determine if ractopamine hydrochloride (RAC) could improve nutrient utilization and decrease water use in hog operations. The growth experiment utilized a comparative slaughter technique that consisted of 120 barrows (95 ± 3 kg BW) including 12 assigned to an initial slaughter group; the remaining pigs were slaughtered at 108- or 120-kg. Growth performance and nutrient retention were determined. The 15 d metabolism experiment consisted of 54 pigs (95 ± 3 kg BW). Growth performance, feed, and water intake and urine and fecal output were measured. The metabolism experiment used 9 dietary treatments arranged as a 3 x 3 factorial: 3 levels of RAC (0, 5 and 10 ppm) and 3 standardized ileal digestible lysine: digestible energy (DE) ratios (1.75, 2.25 and 2.75 g/Mcal DE). The growth study was designed as a 3 x 3 x 2 factorial to include slaughter weight as an additional factor.

In the growth experiment, RAC had no effect ADG, ADFI, or G:F (P > 0.10). With increased Lys levels G:F improved (P < 0.05), but not ADG or ADFI (P > 0.10). Protein deposition rates numerically increased (P = 0.11), water deposition rates tended to increase (P < 0.10), whereas lipid deposition tended to decrease with RAC inclusion (P < 0.10). In the metabolism experiment, with greater levels of RAC and Lys the pigs had improved ADG (P < 0.05) and G:F (P < 0.001). Water intake (P < 0.05.) and urine output (P < 0.05) decreased with greater RAC inclusions. Lys inclusion did not alter water balance (P > 0.10). Urinary N excretion (P < 0.05), total N excretion (P < 0.05), and the urine N:fecal N ratio (P < 0.001) decreased with addition of dietary RAC; however fecal N (P < 0.05) increased with dietary RAC inclusion. Retention of N improved with addition of RAC to the diet (P < 0.05). With greater dietary Lys inclusion fecal N was reduced (P < 0.001). The pigs fed the 2.25 g/Mcal Lys tended to have the lowest urinary N and total N excretion and highest N retention (P < 0.10) and greatest urinary N:fecal N ratio (P < 0.05). A RAC x Lys interaction was observed for N digestibility, excretion, and retention and fecal and urinary N (P < 0.05). By improving N and water utilization in finishing pigs, RAC containing diets supplemented with sufficient Lys can reduce the environmental footprint of pork production.