Stocking rate and monensin supplemental level effects on growth performance of beef cattle consuming warm-season grasses1

Abstract

The objective of this study was to evaluate the effects of monensin supplementation on animals receiving warm-season grass with limited supplementation. In Exp. 1, treatments were a factorial combination of 2 stocking rates (1.2 and 1.7 animal unit [AU] [500 kg BW]/ha) and supplementation with monensin (200 mg/d) or control (no monensin) distributed in a complete randomized design with 3 replicates. Thirty Angus × Brahman crossbred heifers (Bos taurus × Bos indicus) with initial BW of 343 ± 8 kg were randomly allocated into 12 bahiagrass (Paspalum notatum) pastures and supplemented with 0.4 kg DM of concentrate (14% CP and 78% TDN) daily for 86 d. Herbage mass (HM) and nutritive value evaluations were conducted every 14 d, and heifers were weighed every 28 d. There was no effect (P ≥ 0.97) of monensin on HM, herbage allowance (HA), and ADG; however, animals receiving monensin had greater (P = 0.03) plasma urea nitrogen (PUN) concentrations. The stocking rate treatments had similar HM in June (P = 0.20) and July (P = 0.18), but the higher stocking rate decreased (P < 0.01) HM and HA during August and September. Average daily gain was greater (P < 0.01) for the pastures with the lower stocking rate in August but not different in July and September (P ≥ 0.15). Gain per hectare tended to be greater on pastures with the higher stocking rate (P ≤ 0.06). In Exp. 2, treatments were 3 levels of monensin (125, 250, and 375 mg/animal per day) and control (no monensin) tested in a 4 × 4 Latin square with a 10-d adaptation period followed by 5 d of rumen fluid collection and total DMI evaluation. Blood samples were collected on d 4 and 5 of the collection period. Ground stargrass (Cynodon nlemfuensis) hay (11.0% CP and 52% in vitro digestible organic matter) was offered daily. The steers received the same supplementation regimen as in Exp. 1. Total DMI was not different among treatments (P = 0.64). There was a linear increase (P ≤ 0.01) in propionate and a tendency for decreased acetate (P ≤ 0.09) concentrations in the rumen with increasing levels of monensin; however, there was no effect (P ≥ 0.19) of monensin levels on ruminal pH and ruminal concentrations of butyrate and ammonia. In addition, there was no effect (P ≥ 0.73) of monensin levels on plasma concentrations of glucose, insulin, IGF-1, and PUN. In summary, monensin supplementation effects were not detected at either stocking rate and may not be effective in increasing performance of beef cattle grazing low-quality warm-season grasses with limited supplementation.

Virginiamycin and sodium monensin supplementation for beef cattle on pasture

“…The average monensin dose used in the experiments was 28.1mg per kg of diet and a linear effect was observed for ADG with increasing ionophores dose. Vendramini et al (2015) evaluated the effects of monensin in crossbreed Angus x Brahman heifers kept in Paspalum notatum pasture with a concentrate supplementation restricted to 400mg/animal, day -1 and did not observe differences in ADG between animals supplemented or not with monensin (200mg/animal, day -1 ), corresponding to 58mg per 100kg BW, a dose above the one consumed by animals in the present study, but with similar results. Vendramini et al (2015) also tested 0, 14.5, 29.0 and 43.5mg of monensin per kg of DMI, using cannulated young bulls, consuming 0.2% of BW of hay and concentrate.…”

Group sizes effects on growth performance and behavioural characteristics in Korean native calves

“…Fighting for feed is a behaviour that may cause higher feed competition. The results of this study are consistent with other studies that reported similar results in the performance of growing heifers (Vendramini et al 2015) and dairy cattle (Lobeck-Luchterhand et al 2015). Hanwoo calves are social animals and thus higher numbers of calves in one group may increase fighting behaviour in calves as we observed in this study.…”

Degradabilidade de gramíneas, fermentação e protozoários no rúmen de bovinos em dietas com diferentes aditivos

“…Fereli et al (2010) também não observaram diferenças no pH ruminal de bovinos com o uso de levedura e monensina. A monensina tem sido identificada causar aumento do pH ruminal em dietas ricas em concentrado (SAFAEI et al, 2014), mas não em bovinos sob pastejo ou em dieta rica em forragem (DEMARCO et al, 2014;VENDRAMINI et al, 2015). Houve diminuição no valor médio do pH de antes da alimentação (6,62) para 4 h após (6,47).…”

“…A concentração de nitrogênio amoniacal no rúmen foi reduzida com a adição de monensina (13,77mg/dL) em relação à dieta controle (16,48mg/dL) (Tabela 4). Entretanto, pesquisadores não observaram efeitos da monensina na produção de N-amoniacal no rúmen em bovinos (FERELI et al, 2010;VENDRAMINI et al, 2015). Em dieta de baixa qualidade de forragem a adição de levedura tem sido observada causar redução na concentração de N-amoniacal no rúmen (MAO et al, 2013).…”

“…Monensina atua como efeito tóxico a muitas bactérias presentes no rúmen, entretanto, bactérias que reduzem succinato à propionato são mais resistentes à ação da monensina, promovendo aumento na produção de propionato (AZZAZ et al, 2015). Esses resultados estão em concordância com os dados obtidos com bovinos e bubalinos com o uso de monensina e levedura (ZEOULA et al, 2011) e, também com bovinos de corte recebendo diferentes níveis de monensina na dieta (VENDRAMINI et al, 2015). A produção total dos ácidos graxos de cadeia curta no rúmen foi maior nos animais que receberam levedura e Fator P (p<0,05) que aqueles que recebendo dieta sem aditivos e com o uso de monensina sódica.…”