Summary

Prairie Swine Centre and others have shown improvements in lean growth and feed efficiency when ractopamine (Paylean®) was fed to finishing pigs. The objective of the following experiment was to determine if the improvements in nutrient utilization with Paylean can lead to a demonstrable reduction in the environmental footprint of pork production. A metabolism experiment was conducted to measure the effect of 5 or 10 mg/kg ractopamine (RAC) from Paylean on nitrogen (N) and water balance in finishing swine. Paylean improved average daily gain (ADG), N retention in the carcass and feed efficiency and decreased water intake and urine output. Because of the improvement in N and water utilization in finishing pigs, the authors conclude that Paylean can reduce the environmental impact of pork production.

Introduction

The excretion of nitrogen (N) in the manure of swine is problematic because it is in the form of ammonia, which has odour and other environmental implications. Ractopamine hydrochloride (RAC) or Paylean (Elanco Animal Health, Guelph, ON) is a β-adrenergic agonist which, when added to the diet of finishing swine, improves ADG, feed efficiency and carcass lean growth. These growth performance and carcass improvements are well noted in the literature but there is limited research on other potential benefits of Paylean.

A small number of studies have looked at RAC’s impact on reducing nutrient excretion; however inclusion levels of 18 to 20 mg/kg were used. Currently, the Canadian Food Inspection Agency approves RAC at inclusion levels of 5 and 10 mg per kg, thus, these were the levels used in the following study.

The overall objective of this experiment was to define the impact of RAC on the efficiency of pork production with a view to reducing the environmental impact of pork production. Specifically we wanted to determine the effect of RAC on the efficiency of N utilisation, and to evaluate the eff ect of RAC on the efficiency of animal performance, including carcass quality and water and feed requirements for growth.

Materials and Methods

The experiment used 54 barrows assigned to one of nine treatments when they reached 95±3kg bodyweight.

Treatments were three levels of RAC (0, 5 or 10 mg/kg) × three lysine:DE ratios (1.75, 2.25 or 2.75g ileal digestible lysine:kcal DE). Barrows were on test for 15 days and maintained in pens that allowed the collection of faeces and urine. Collection of urine and faeces occurred on days 6 to 8 and 13 to 15 of the experiment allowing us to determine if the response to RAC changed over time. Diets were based on wheat, barley and soybean meal and also contained canola oil, vitamin/mineral premix and synthetic amino acids. All diets were formulated to contain 3,300 kcal DE/kg and formulated to meet or exceed the nutrient requirements of the finisher pig.

* “It is proven that Paylean can reduce the environmental impact of pork production because of the improvement in nitrogen and water utilization”

Results and Discussion

Final BW, ADG, ADFI and G:F (P<0.05) increased as RAC concentration in the diet increased. Final BW, ADG (P<0.05) and G:F increased (P<0.001) and ADFI decreased (P<0.001) with increasing lysine (Lys) levels (Table 1). Pigs fed no RAC averaged 19 days to reach market and RAC fed pigs required 17 days.

Table 2 describes water balance and faecal ouput. A decrease in water intake and excretion (urine output and faecal moisture; P<0.05) was observed with increased RAC. Apparent water retention tended to decrease with RAC inclusion (P=0.10). Faecal output (dry basis) was greatest for the 5mg/kg RAC-fed pigs than the other treatments (P<0.05). Greater lysine concentrations tended to decrease fecal output (P<0.10) but lysine had no effect on water intake, excretion and apparent water retention (P>0.10).

Nitrogen intake, N digestibility, urinary N excretion, faecal N excretion and total N excretion decreased and N retention increased (P<0.05) with increased RAC (Table 3). Nitrogen intake, N digestibility, urinary N excretion, total N excretion and N retention increased with greater dietary Lys concentration (P<0.05) but faecal N excretion was unaffected (P>0.10).

Calculations based on the present data were applied to a commercial situation 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 fi-nishing barn (Table 4). In these calculations, it was assumed that pigs started on treatment diets at 95kg and finished at 120kg.

The calculations indicated that 10 mg/kg Paylean supplemented at 95kg and fed for 17 days would reduce feed intake and water consumption by 7.5 kg and 33.1 litres per pig, respectively. Water and faecal excretion would be reduced by 18.6 litres and 0.9kg per pig, respectively. N intake was reduced by 0.2kg per pig, and N excretion declined by 0.2kg per pig. When comparing the 5 mg/kg Paylean level to the 10 mg/kg level, the 10 mg/kg Paylean-fed pigs had the most substantial reduction in intake and excretion of both water and nitrogen.

Using the results obtained in this experiment and applying them to a commercial situation demonstrates that Paylean can have a significant impact on reducing the environmental footprint for pork production. Therefore, feeding either 5 or 10 mg/kg RAC can improve environmental sustainability of market hogs by reducing feed requirements, decreasing water consumption and excretion, and improve utilization of dietary N.

Implications

RAC feeding has the potential to reduce the environmental footprint associated with marketing hogs. Results from these experiments indicate that supplementing either 5 or 10mg/kg RAC in finishing swine diets can improve N utilisation. A decrease in urinary N excretion from 35.1 per cent to 29.8 per cent and improvement in N retention from 49.3 to 54.0 per cent in control and 10 mg/kg RAC-fed pigs, respectively, can reduce excess N being released in soil and water when manure is spread on land. RAC also improved protein deposition rates to 189.2 grammes per day in the 10 mg/kg RAC-fed pigs, whereas lipid deposition rates decreased to 542.3 grammes per day.

Supplementing RAC produced a leaner carcass with improved nutrient utilisation. As well, RAC-feeding reduced water intake by onelitre per day and water excretion was reduced by 0.7 litres per day with 10 mg/kg RAC–feeding, which can decrease water consumption requirements for finishing hogs.

Acknowledgements

Strategic program funding is provided by Sask Pork, Alberta Pork, Manitoba Pork Council and the Saskatchewan Agricultural Development Fund. Project funds were provided by Elanco Animal Health.

May 2010