Ractopamine as a metabolic modifier feed additive for finishing pigs: a review

The β-adrenergic agonist ractopamine is increasingly used in the swine industry due to higher consumer demand for leaner pork products. Redirecting nutrients to favor leanness rather than fat deposition, ractopamine improves growth and carcass traits of finishing pigs. However, the impact of this agonist on pork quality is not clearly defined. Understanding the biological effects of dietary ractopamine dose, treatment period, lysine levels, and the lysine to metabolizable energy ratio will help pork producers achieve improvements in animal performance, carcass leanness, and economic efficiency in swine production systems

Combined use of ionophore and virginiamycin on metabolism, digestibility, and feeding behavior of Nellore steers confined with high concentrate diets

Dois experimentos foram conduzidos com o objetivo de avaliar os efeitos do uso combinado de salinomicina e virginiamicina sobre o metabolismo ruminal, a digestibilidade, o comportamento ingestivo e as características sanguíneas de novilhos Nelore alimentados com dietas de alto concentrado. No experimento I, oito novilhos Nelore com 322 ± 26 kg de peso vivo (PV) inicial foram alocados no delineamento em quadrado latino 4 x 4 replicado, com quatro tratamentos em quatro períodos de 16 dias. Os tratamentos foram arranjados em esquema fatorial 2 x 2, com dois níveis de salinomicina (0 e 13 ppm) e dois níveis de virginiamicina (0 e 15 ppm) na matéria seca (MS) das dietas, que continham 80% de concentrado na MS. No experimento II, oito novilhos Nelore com 434 ± 35 kg de PV inicial foram alocados no mesmo delineamento, mas com períodos de 21 dias. Os tratamentos foram arranjados em esquema fatorial 2 x 2, com dois níveis de concentrado (70 e 90%) e dois níveis de virginiamicina (0 e 15 ppm) na MS das dietas. A salinomicina foi incluída em todas as dietas (13 ppm). Em ambos os experimentos, foram avaliados o consumo individual, a degradabilidade ruminal in situ, a digestibilidade aparente, a fermentação ruminal, o comportamento ingestivo, a população de protozoários ciliados ruminais e as características sanguíneas. As análises estatísticas foram realizadas pelo procedimento MIXED do SAS. No experimento I, houve efeito de nível de salinomicina e virginiamicina sobre as degradabilidades efetiva (DE) e potencial (DP) da fibra insolúvel em detergente neutro (FDN), sendo que os menores valores (P ≤ 0,05) foram observados para os animais tratados com os aditivos. A digestibilidade da proteína bruta (PB) foi maior (P = 0,01) para os novilhos que receberam salinomicina. Animais tratados com virginiamicina apresentaram maior (P = 0,01) concentração ruminal de propionato e menores (P ≤ 0,05) concentrações de acetato, butirato e lactato. Esses animais também apresentaram maior (P ≤ 0,03) tempo total de ruminação (TTR) e mastigação (TTM) e maior (P = 0,05) concentração de lactato no sangue. No experimento II, o aumento no teor de concentrado das dietas promoveu aumento (P = 0,01) no consumo de MS e nas digestibilidades aparentes da MS e PB, bem como redução (P < 0,01) na DE da FDN e PB. Animais tratados com ambos os aditivos apresentaram menor (P = 0,03) DE da FDN. As concentrações ruminais de acetato foram reduzidas (P < 0,01) com a inclusão de virginimicina, mas novilhos tratados com ambos os aditivos e alimentados com dieta contendo 90% de concentrado apresentaram aumento (P < 0,01) nas concentrações de propionato. O aumento no teor de concentrado promoveu redução (P < 0,01) no TTR e TTM dos animais, bem como na população de protozoários ciliados do rúmen e no pH sanguíneo. O uso combinado de salinomicina e virginiamicina apresentou efeitos positivos sobre a fermentação ruminal, especialmente quando a dieta com maior proporção de concentrado foi utilizada.Two experiments were conducted to evaluate the effects of the combined use of salinomycin and virginiamycin on ruminal metabolism, digestibility, feeding behavior, and blood characteristics of Nellore steers fed high concentrate diets. In experiment I, eight Nellore steers with 322 ± 26 kg of initial body weight (BW) were allotted to a replicated 4 x 4 Latin square, with four treatments and four 16-day periods. Treatments were arranged in a 2 x 2 factorial design, with two salinomycin levels (0 and 13 ppm) and two virginiamycin levels (0 and 15 ppm) in the diet dry matter (DM), which contained 80% concentrate on a DM basis. In experiment II, eight Nellore steers with 434 ± 35 kg of initial BW were allotted to the same experimental design, but with 21-day periods, in a 2 x 2 factorial arrangement of treatments, with two concentrate levels (70 and 90%) and two virginiamycin levels (0 and 15 ppm) in the diet DM. Salinomycin was included in all diets (13 ppm). In both experiments, individual intake, in situ ruminal degradability, apparent digestibility, ruminal fermentation, feeding behavior, ciliated protozoa counts, and blood characteristics were evaluated. Statistical analyses were conducted using the MIXED procedure of SAS. In experiment I, there were effects of salinomycin and virginiamycin on effective and potential degradabilities (ED and PD, respectively) of the neutral detergent fiber (NDF), with lower values (P ≤ 0.05) observed for animals receiving the additives. Crude protein (CP) digestibility was higher (P = 0.01) for salinomycin-treated steers. Animals receiving virginiamycin showed higher (P = 0.01) ruminal concentrations of propionate and lower (P ≤ 0.05) ruminal concentrations of acetate, butyrate, and lactate. These animals also showed higher (P ≤ 0.03) total time spent ruminating (TTSR) and total time spent chewing (TTSC), as well as higher (P = 0.05) blood lactate concentrations. In experiment II, increasing concentrate levels increased (P = 0.01) DM intake and DM and CP digestibilities, but also decreased (P < 0.01) ED of the NDF and CP. Ruminal concentrations of acetate were reduced (P < 0.01) due to the inclusion of virginiamycin, but steers receiving both feed additives within the 90% concentrate group showed increased (P < 0.01) ruminal concentrations of propionate. Increasing concentrate levels decreased (P < 0.01) TTSR and TTSC, as well as ciliated protozoa counts and blood pH. The combined use of salinomycin and virginiamycin showed positive effects on ruminal fermentation, especially when animals were fed the higher concentrate diet

Combined use of ionophore and virginiamycin for finishing Nellore steers fed high concentrate diets

Zebu cattle fed high concentrate diets may present inconsistent performance due to the occurrence of metabolic disorders, like acidosis. The isolated use of ionophores and virginiamycin in high grain diets can improve animal performance and reduce the incidence of such disorders, but recent studies suggested that their combination may have an additive effect. Thus, 72 Nellore steers, 389 ± 15 kg initial body weight (BW), were confined and fed for 79 days to evaluate the combination of virginiamycin and salinomycin on performance and carcass traits. Animals were allocated to a randomized complete block design by BW, in a 2 × 2 factorial arrangement of treatments, with two concentrate levels (73 and 91 %) and two virginiamycin levels (0 and 15 mg kg-1), and salinomycin (13 mg kg-1) included in all diets. The interaction was not significant (p &gt; 0.05). Dry matter intake (DMI), average daily gain (ADG), gain-to-feed ratio (G:F), starch consumed, and fecal starch content were higher (p < 0.05) for the 91 % concentrate treatment. These animals also had higher (p < 0.05) hot carcass weight and dressing percentage. Virginiamycin-treated animals showed lower DMI, but ADG and G:F did not differ (p &gt; 0.05) between treatments. Starch consumed and estimated dietary net energy for maintenance (NEm) and gain (NEg) were higher (p < 0.05) for virginiamycin-treated animals, with no substantial effects on carcass traits. The inclusion of virginiamycin in finishing diets containing salinomycin reduced DMI while maintaining ADG and improving NEm and NEg, suggesting an additive effect of virginiamycin and ionophores, but without affecting carcass quality