Improvements in lean growth and feed efficiency when ractopamine hydrochloride is fed to finishing pigs are well documented. Research was conducted to determine if the improvements in nutrient utilization can lead to a demonstrable reduction in the environmental footprint of pork production, specifically water utilization and nitrogen (N) output.
Nitrogen in swine manure is problematic because it is excreted in the form of ammonia (NH3), an odorous product with other environmental implications. Ractopamine hydrochloride (RAC, or Paylean from Elanco Animal Health) is a beta-adrenergic agonist that, when added to the diet of finishing swine, improves average daily gain (ADG), feed efficiency and carcass lean growth. These growth performance and carcass improvements are well documented in the literature, but there is limited research on the environmental benefits of RAC supplementation in finishing diets, especially at lower levels of inclusion, permitted in Canada. The Canadian Food Inspection Agency approves RAC at inclusion levels of 4.5 and 9 g./ton, the levels used in this study.
The overall objective of the study was to define the impact of RAC on the efficiency of pork production and, in turn, its impact on the environment. Specifically, researchers wanted to determine the effect of RAC on the efficiency of N utilization and its effect on the efficiency of animal performance, including carcass quality and water and feed requirements for growth.
The experiment included 54 barrows assigned to one of nine treatments when they reached 210 lb. Treatments were three levels of RAC (0, 4.5 or 9 grams/ton) and three lysine:digestible energy (DE) ratios (1.75, 2.25 or 2.75 grams ileal digestible lysine:kcal DE).
Barrows were housed in pens that allowed the collection of feces and urine on Days 6 to 8 and Days 13 to 15, an attempt to determine if the response to RAC changed over time.
Diets were based on wheat, barley and soybean meal, plus canola oil, vitamin/mineral premix and synthetic amino acids. All diets contained 1,500 kcal DE/lb., formulated to meet or exceed the National Research Council (NRC) nutrient requirements.
Final body weight (BW), average daily gain (ADG), average daily feed intake (ADFI), and gain:feed (G:F) ratio increased as RAC concentration increased. Final BW, ADG and G:F increased, and ADFI decreased with increasing lysine levels (Table 1 ). Pigs fed no RAC averaged 19 days to reach market, while RAC-fed pigs required 17 days.
Table 2  contains water balance and fecal output data. A decrease in water intake and excretion (urine output and fecal moisture), was observed as RAC levels increased. Apparent water retention tended to decrease with RAC inclusion.
Fecal output (dry basis) was greatest for the 4.5 g./ton RAC-fed pigs when compared to the 0 (control) and 9 g./ton treatments. Higher lysine concentrations tended to decrease fecal output, but lysine had no effect on water intake, water excretion and apparent water retention.
Nitrogen intake, N digestibility, urinary N excretion, fecal N excretion, and total N excretion decreased, and N retention increased with increased RAC levels (Table 3 ). Nitrogen intake, N digestibility, urinary N excretion, total N excretion and N retention increased with greater dietary lysine concentration (Table 3 ), but fecal N excretion was unaffected.
Results from these experiments indicate that supplementing either 4.5 or 9 g./ton RAC in finishing swine diets can improve N utilization. RAC improved protein deposition and decreased lipid deposition in the
9 g./ton RAC-fed pigs. RAC reduced water intake by 0.26 gal./day, and water excretion was reduced by 0.19 gal./day at the 9 g./ton RAC level. A decrease in urinary N excretion from 35.1% to 29.8% and an improvement in N retention from 49.3 to 54.0% in control and 9 g./ton RAC-fed pigs, respectively, can reduce excess N being released in soil and water when manure is applied to the land.
Calculations based on the research data were applied to a commercial setting to define the potential impact of RAC on the environment. The values obtained in the metabolism study were used to calculate nutrient balance in a 1,000-head finishing barn (Table 4 ). Pigs started on treatment diets at 210 lb. and finished at 260 lb.
Calculations indicated that 9 g./ton RAC supplemented to 210-lb. pigs and fed for 17 days would reduce feed intake and water consumption by 16.5 lb./pig and 8.7 gal./pig, respectively. Water and fecal excretion would be reduced by 4.9 gal./pig and 2 lb./pig, respectively. N intake was reduced by 0.44 lb./pig, and N excretion declined by 0.44 lb./pig.
When the 4.5 g./ton RAC level was compared to the 9 g./ton level, the 9 g./ton-fed pigs had the most substantial reduction in intake and excretion of both water and nitrogen.
These experimental results applied to commercial production demonstrate that Paylean can have a significant impact on reducing the environmental footprint from pork production.
Program funding was provided by Sask Pork, Alberta Pork, Manitoba Pork, the Saskatchewan Agricultural Development Fund and Elanco Animal Health.
Researchers: K.A. Ross and A.D. Beaulieu, Prairie Swine Centre, Saskatoon, SK Canada; J. Merrill and G. Vessie, Elanco Animal Health, Guelph, ON Canada; and J. F. Patience, Iowa State University, Ames, IA. Contact Beaulieu at (306) 667-7441 or e-mail: [email protected] .