Review: Effects of Ractopamine Hydrochloride (Paylean) on welfare indicators for market weight pigs1

Abstract

This review summarizes the effects of ractopamine hydrochloride (RAC) dose (5, 7.5, 10, and 20 mg/kg) on market weight pig welfare indicators. Ractopamine hydrochloride (trade name Paylean) is a β-adrenergic agonist that was initially approved in the U.S. in 1999 at doses of 5 to 20 mg/kg to improve feed efficiency and carcass leanness. However, anecdotal reports suggested that RAC increased the rate of non-ambulatory (fatigued and injured) pigs at U.S. packing plants. This led to the addition of a caution statement to the Paylean label, and a series of research studies investigating the effects of RAC on pig welfare. Early research indicated that: (1) regardless of RAC administration, fatigued (non-ambulatory, non-injured) pigs are in a state of metabolic acidosis; (2) aggressive handling increases stress responsiveness at 20 mg/kg RAC, while 5 mg/kg reduces stress responsiveness to aggressive handling. Given this information, dosage range for Paylean was changed in 2006 to 5 to 10 mg/kg in market weight pigs. Subsequent research on RAC demonstrated that: (1) RAC has minimal effects on mortality, lameness, and home pen behavior; (2) RAC fed pigs demonstrated inconsistent prevalence and intensity of aggressive behaviors; (3) RAC fed pigs may be more difficult to handle at doses above 5 mg/kg; and (4) RAC fed pigs may have increased stress responsiveness and higher rates of non-ambulatory pigs when subjected to aggressive handling, especially when 20 mg/kg of RAC is fed.

Cattle and Pigs Are Easy to Move and Handle Will Have Less Preslaughter Stress

“…Ractopamine and zilpaterol are feed additives that are used to increase the amount of muscle [27]. High doses of ractopamine were associated with greater difficulty in handling pigs [28,29]. Hot weather is also more likely to increase death losses in cattle fed ractopamine [30,31].…”

“…Hot weather is also more likely to increase death losses in cattle fed ractopamine [30,31]. Handling problems observed by both the author and reports in the scientific literature both indicate that high doses, combined with hot weather over 32 • C, caused the most problems [8,29]. Pigs fed beta-agonists must be handled in a low-stress manner to prevent downed non-ambulatory animals [32].…”

“…(3) Feeding high-grain diets to cattle and a lack of roughages [25]; (4) High doses of beta-agonists fed to both cattle and pigs [28,29].…”

Evaluation of a Phytogenic Compound with Minerals as a Possible Alternative to Ractopamine for Finishing Pigs

“…However, the use of ractopamine generates discussion about the countereffects on pigs as the animals tend to be more susceptible to stress due to the effect on heart rate and catecholamine [ 5 ]. In a review carried out by Ritter et al [ 6 ], the authors concluded that the product makes it difficult to handle pigs as it increases their aggressive behavior. Conversely, studies indicate that ractopamine has no impact on the general welfare status of the animals [ 7 ].…”

Ractopamine: analytical method validation; and the detection in loin, tissues and urine of pigs fed meat and bone meal containing this growth promoter

“…Many studies have demonstrated advantages for pig production by adding RAC to animal feed such as increased weight gain and improved feed efficiency, increased loin-eye area, meat percentage, meat: fat ratio and reduced back fat thickness (Mimbs et al 2005;Rikard-Bell et al 2009;Athayde et al 2012;Ho et al 2014;Ritter et al 2017;Dalla Costa et al 2018). This improvement in carcass yield is directly related to meat quality, which will result in a higher financial profit to the slaughterhouse.…”