Torta de algodão como fonte de fibra efetiva na dieta de novilhos Nelore terminados em confinamento

Abstract

Cottonseed cake (CSC) is a co-product rich in neutral detergent fiber (NDF), which allows its use as a source of fiber in forage-free diets for ruminant animals. The objective was to evaluate CSC as a source of physically effective fiber (peNDF) replacing corn silage (CS) in the diet of feedlot finished beef cattle. Twenty-four Nellore bulls (Bos taurus indicus L.) were used, with an average body weight (BW) of 377.8 kg and an approximate age of 24 months. The treatments were: diet with 30% forage in the form of CS, and diet without forage containing 30% CSC as a source of fiber, based on dry matter (DM). The design used was completely randomized with two treatments and 12 replications. There was an interaction between fiber source and nutrient in the material retained in the Penn State Particle Separator, CSC had higher peNDF (particles ≥ 8 mm) than CS. The highest concentrations (p<0.05) of peNDF and in vitro digestibility of peNDF were for CSC. Bulls fed with CSC showed longer feeding time and feeding efficiency, with less rumination time and rumination efficiency (p<0.05). The intake of DM, organic matter (OM), NDF, peNDF, crude protein (CP) and non-fiber carbohydrates (NFC) of bovines fed CS diet were higher (p<0.05), and the consumption of ether extract of cattle fed CSC diet was higher (p<0.05). Dry matter, OM, NDF and CP digestibility were higher for CS diet (p<0.05), and NFC consumption tended to be higher (p=0.09) for CSC diet. There was no interaction between diets and periods (p>0.05) for BW and feed conversion, bovines fed with CS showed higher BW in periods of 0-15 and 15-30 days. There was interaction between diets and periods for total weight gain (TWG), average daily gain (ADG) and feed efficiency (FE). It was observed that animals fed CSC diet had a more difficult adaptation (0-15 days), but ADG and FE recovered at 15-30 days, ADG and TWG were higher from 30-60 days. The CSC diet promoted higher weight and carcass yield (p<0.05). There was no interaction between maturation times and fiber sources. Maturation for 7 days tended to promote (p=0.05) improvement in shear strength. The CS diet showed higher concentrations (p<0.05) of C16:1, C18:1n9c, C18:3n3, C22:2, monounsaturated and ω9 fatty acids in meat. The CSC diet showed higher concentrations (p<0.05) of C15:0, C18:1n9t, C18:2n6c, 20:3n3, ω6 and ω6:ω3 ratio in meat. The CS diet promoted higher total costs per animal (US$ 408.41 vs. US$ 336.06) and daily costs (US$ 3.65 vs. US$ 3.00). The CSC treatment had the highest net margin (US$ 106.98/animal). Cottonseed cake can be used in feedlots for beef cattle as a source of peNDF and forage-free diets. Because it improves animal performance, stimulates rumination, increases the ω6:ω3 ratio in beef and reduces confinement costs.