Idacir Antonio Santin Junior

Wheat silage is an underexplored forage in ruminant nutrition that offers potential benefits due to its high crude protein content and capacity to mitigate methane emissions. However, little is known about its interaction with feed additives. This study evaluated the effects of monensin (25 ppm) and narasin (13 ppm) on the in vitro ruminal fermentation of wheat silage using a randomized complete block design with three treatments and seven replicates per incubation. Gas production was recorded over 48 h, and fermentation parameters, including pH, in vitro organic matter digestibility (IVOMD), metabolizable energy (ME), ammonia nitrogen (NH₃-N), and volatile fatty acid (VFA) profiles, were determined. Both ionophores maintained a higher ruminal pH compared to the control (p < 0.01) and reduced total gas production, ME, and IVOMD (p < 0.01), without significant differences between monensin and narasin. No effects were observed on total VFA production, acetate-to-propionate ratio, or ammonia concentration, although isobutyrate was reduced (p < 0.01). Fermentation kinetics revealed decreased gas production and digestion rates in the slowly degradable fraction, particularly with monensin. In conclusion, ionophores modulated fermentation but did not improve digestibility or energy availability, suggesting limited nutritional benefits when wheat silage is used as the sole forage source.

Beef cattle production has a large variety of systems with different performance and technology levels. This study compared young Angus steers carcass and meat quality traits of high growth potential early-finished animals fed exclusively on pasture with low growth potential late-finished animals. Besides the grazed forage, the low growth potential group received corn grain at 0.8% of their body weight right after the slaughtering of the first group. Following weaning, the 20 steers grazed pastures composed of oat, ryegrass, and clovers. At winter’s onset, animals were moved to native pastures improved with fescue and clovers. The supplemented period of late steers began when the first group of ten early-finished animals reached the requirements for slaughter. Supplementation ended when the animals got the slaughter requirements. The high growth potential steers showed a ribeye area (P < 0.0001) and a Longissimus muscle width highly significantly (P < 0.0001) superior to the low growth group. However, corn-supplemented animals showed better dressing percentage (P < 0.0001), subcutaneous fat thickness (P < 0.0001), marbling (P < 0.0001), and muscle (P = 0.0033) scores, but lower shear force (P = 0.0001). The finishing system did impact fat lightness (L*; P = 0.0234) at the slaughter time. Grass-fed animals showed higher red-green color parameter (a*) values than corn supplemented on fat at 24 h (P = 0.0439) but lower hue angle (P = 0.0418). The consumer panel showed better results for tenderness and general acceptability for supplemented animals beef compared to grass-fed. The supplementation resulted in a higher carcass standardization. It also provided higher PUFA: MUFA and n-6: n-3 ratios, and a higher amount of n-3. Supplemental corn grain did not have adverse effects upon the beneficial effects to human health of the grass-fed beef.

O selênio é um mineral essencial sendo cofator de enzimas antioxidantes, dentre as fontes disponíveis no mercado o selenito de sódio (fonte inorgânica) é a mais estuda e utilizada, contudo fontes orgânicas têm sido descritas como mais eficientes. Com base nisso o objetivo deste estudo foi avaliar se as diferentes fontes inorgânica (selenito de sódio) e orgânica (selenometionina) na dieta de grão de milho inteiro para terminação de novilhos Angus apresentam efeitos sobre desempenho e qualidade de carcaça e carne. Para isso, foram selecionados 22 animais, divididos em: grupo selenito de sódio (SS=11) e grupo selenometionina (SM=11). O confinamento foi de 82 dias, sendo realizadas 4 pesagens. Foi mensurado o peso de carcaça, temperatura e pH ao abate e 24 horas, rendimento de carcaça, perdas por resfriamento, pH, cor, e espessura da gordura subcutânea. Amostras do músculo Longissimus thoracis foram retiradas entre 12º e 13º costelas da meia carcaça esquerda para mensuração de largura e profundidade do músculo, área de olho de lombo, coloração e pH da carne em 24 horas e 48 horas, além de demais análises laboratoriais como: maciez, perda por cocção, TBARS e concentração de selênio. Não houve diferença entre os grupos para os parâmetros de desempenho e qualidade de carcaça e carne, bem como para concentração de selênio e tempo de congelamento. Portanto, ambas as fontes de selênio podem ser usadas nas dietas de grão de milho inteiro para terminação de novilhos Angus e apresentam os mesmos efeitos sobre desempenho, qualidade de carcaça e carne.