Physiopathological changes related to the use of ractopamine in swine: Clinical and pathological investigations

Abstract

The aim of the study was to investigate clinical and pathological modifications induced by treatment with different doses of the β2-agonist ractopamine (RAC) in pigs. Thirty-two eight-month-old LandracexLarge White pigs (mean weight, 102.8 ±6.7 kg) were treated with 0, 10 (R10), 20 (R20) and 40 (R40) mg/kg/diet of RAC for the last 35 days before slaughtering. Before and after treatment body weight was recorded, blood samples were collected for complete blood count and thyroid hormone concentration analysis, and cardiac instrumental evaluation was performed. At slaughtering, tissue samples were collected for histopathological examination. None of the animals showed any signs of clinical disease during the study period. Treatment did not induce any statistically significant difference in complete blood counts (P>0.05) among groups.A significant (Pb0.05) decrease in feed consumption was observed between R10 and R40 treated animals. A significant (Pb0.01) increase in ventricular internal dimensions and left ventricular mass was observed in R20; a significant reduction in thyroid weight (Pb0.05) was observed in the animals receiving the highest-dose treatment (R40). Urethral hyperplasia and metaplasia, and prostate hyperplasia and a significant (Pb0.05) reduction in circulating triiodothyronine levels were found in overall treated animals. Taken together, these data suggest that RAC treatment in pigs induces adaptative non-neoplastic urethral and prostatic disorders of growth and a reduction in thyroid hormone concentrations. Nevertheless, additional research on a larger group of animals is needed to define the biomolecular mechanisms underlying the observed lesions, in order to improve the surveillance tools to identify illegal treatments. IntroductionRactopamine (RAC) is a ß-adrenergic agonist (ß-agonist) which at repartitioning doses has been found to increase muscle growth and decrease fat deposition in different animal species (Baker et al., 1984;Mersmann, 1998;Mills and Spurlock, 2003;Ricks et al., 1984;Sillence, 2004;Watkins et al., 1990). In pigs and cattle treated during the final period of the finishing improved feed efficiency, heavier carcass weights, and higher dressing percentages have been documented (Gu et al., 1991a,b; Laudert et al., 2005a,b; Poletto et al., 2009;See et al., 2004).The dosage required to induce "anabolic" effects is generally 10-20 times higher than that indicated for therapeutic purposes. At elevated doses, certain β2-agonists such as clenbuterol can cause morphological, histological and/or biochemical changes in various organs of exposed animals (Biolatti et al., 1994;Sillence et al., 1993). In vivo, β-adrenergic agonists may induce secondary events caused by hormonal or physiological responses of several tissues, involving especially endocrine and cardio-respiratory organs.In pigs, treatment during the finishing with repartitioning doses of β-agonists has been associated with modifications of vascular microcirculation characterized by ulcerative lesions of the distal extremities...

Effects and detection of Nandrosol and ractopamine administration in veal calves

“…Thyroid and heart weight reduction was detected in swine following RA administration (Catalano et al, 2012). On the contrary, in the present experiment, the heart relative weight of veal calves did not undergo any change whereas the thyroid weight increased.…”

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

“…Ractopamine effects on market weight pig heart rates has been evaluated in 4 studies ( Table 12 ), but it is worth mentioning that 1 of these studies only reported raw treatment means (Ivers, unpublished data, Study #1). Catalano et al (2012) reported no difference in baseline resting heart rates at the end of the feeding period among pigs fed 0, 10, 20, or 40 mg/kg RAC. Meanwhile, the RAC effects on heart rate during marketing events (presence of unfamiliar human, handling, loading, transport, and unloading) are conflicting in the literature.…”

Interação ractopamina e hormônio do crescimento no metabolismo de ratas hipofisectomizadas

“…Sabe-se que determinadas doses de ractopamina geram alterações cardíacas por meio da ativação ou dessensibilização dos receptores beta adrenérgicos. Em alguns estudos, como o de Catalano et al (2012), as alterações observadas no coração foram dose independente. No seu estudo com suínos a alta dose de ractopamina gerou uma diminuição cardíaca, o que condiz com o presente estudo no qual os animais apresentaram um menor peso cardíaco quando comparados ao grupo controle.…”

“…Com relação ao peso intestinal, de acordo com Catalano et al (2012), a ractopamina pode causar uma diminuição na concentração do hormônio da tireoide T3, responsável pela regulação térmica do organismo, por estimular de forma cruzada os receptores alfa adrenérgicos, então o intestino tende a aumentar para tentar equilibrar a temperatura corporal do animal.…”