Effect of graded inclusion of pennisetum purpureum grass on growth performance, rumen fermentation and meat quality of feedlot steers

Abstract

The study was carried out to evaluate the effect of graded dietary inclusion levels of Napier grass (Pennisetum purpureum) in steers` fattening diets, on growth performance, rumen fermentation traits, carcass characteristics and meat quality of steers. Representative samples of Napier grass were analysed for proximate (dry matter, crude protein, gross energy, ether extract and ash), fibre fractions (acid detergent fibre, acid detergent lignin and neutral detergent fibre) and mineral profile. Twenty-four 8 months-old male weaners with an average body weight of 176.5±20kg were used. Three experimental diets were formulated wherein Napier grass was included at 0% (Diet 1- control diet), 30% (Diet 2) and 60% (Diet 3) on forage basis to meet the nutrient requirements of growing fattening steers. The steers were allocated to the treatment diets in a completely randomized design. The steers were fed the experimental diets for 120 days during which data was collected following 14 days of adaptation period. Steers were individually weighed at the beginning of the trial and weekly until trial termination. At the end of growth study, the steers were slaughtered and eviscerated. Following evisceration, rumen digesta pH was measured and rumen digesta was collected for volatile fatty acid analysis. Carcass samples were collected and sampled. Dietary inclusion of 60 % Napier grass in steers fattening diet reduced (P˂0.05) body weight gain, daily feed intake and feed efficiency of the steers. The rumen fermentation dynamics of the steers were similar (P>0.05) across the treatment diets. While warm and cold carcass weight, as well as cold muscle temperature of the steers fed diets containing 0 and 30% of Napier grass were higher compared to that containing 60 %; dressing percentage, warm and cold muscle pH of the steers were similar (P>0.05) across dietary treatments. The meat physical attributes (drip loss, colour, myoglobin water holding capacity, cooking loss and tenderness) of the steers did not differ (P>0.05) among the treatment diets. The 7-days aged meat thaw loss increased (P<0.05) with increasing inclusion level of Napier grass. Dietary inclusion of Napier grass at 30% in steers fattening diets yielded meat high in protein and fat. Further research on the fatty acid profile of the meat fat is suggested. Moreover, study to quantify enteric methane production of steers consuming Napier grass-based diets need to be conducted.