Adição de fibra em detergente neutro em dietas à base de palma forrageira para caprinos

Abstract

This study consisted of three experiments. The first evaluated the effects of cactus pear mucilage levels on in vitro ruminal fermentation of cellulose, starch and protein. A 5 × 3 factorial scheme in a completely randomized design with 5 levels of cactus pear mucilage (0, 5, 10, 20 and 40%) and 3 substrates (carboxymethylcellulose, starch and trypticase) was used. The treatments were evaluated by in vitro simulated ruminal environment, following the incubation times: 0, 3, 6, 12, 24 and 48 h. There was interaction (P<0.05) between mucilage and substrate levels for all ruminal parameters evalauted, except on concentration of microbial protein after 48 h of fermentation and for proportion of acetate and butyrate at 0 hour. There was a quadratic effect (P<0.05) on concentration of ammonia nitrogen after 48 h of fermentation in the medium containing carboxymethylcellulose and trypticase. The pH values were quadratically decreased (P<0.05) in function of mucilage levels in the medium containing trypticase and carboxymetilcelulose. Production of ammonia nitrogen by rumen microorganisms in medium containing starch, was maximum at 6 h of fermentation. The concentration of microbial protein by rumen microorganisms in medium containing trypticase, was maximum at 24 h of fermentation, reducing after this time. The inclusion of up to 40% of prickly pear cactus mucilage does not affect rumen fermentation pattern of cellulose, starch and protein by rumen microorganisms. The second experiment evaluated the effects of relationships between neutral detergent fiber from forage (fNDF) and non fibrous carbohydrates (NFC) on ruminal fermentation products and in vitro digestibility of neutral detergent fiber. A 3 × 5 factorial scheme in xvii a completely randomized design with three fNDF levels (10, 19 and 19%) and five levels of NFC (35, 40, 45, 50 and 55%) was used, all on dry mater basis. The treatments were evaluated by in vitro simulated ruminal environment, following the incubation times: 0, 3, 6, 12, 24 and 48 h. There was interaction (P<0.050) between fNDF and NFC for all ruminal parameters variables studied. There was no adjust of linear models (P>0.05) for pH values between fNDF levels in function of NFC levels. Total volatile fatty acid (VFA) and individual molar proportions was affected (P<0.05) among fNDF and NFC levels. NDF digestibility had no effect (P>0.05) of fNDF and NFC levels, except for experimental diets containing 29% of fNDF which had quadratically effect (P=0.0056). Diffferents relationship among the levels of neutral detergent fiber and non fibrous carbohydrates affect fermentation end products and in vitro digestibility by experimental diets. The third experiment evaluated the effects of forage neutral detergent fiber on intake, digestibility, ruminal parameters and feeding behavior of goats fed diets with cactus pear. Treatments consisted of levels of fNDF 0, 109, 222, 339, and 463 g/kg in diets cactus pear based. Intakes of dry matter (DM) and neutral detergent fiber (NDF) were quadratically affected (P ≤ 0.045) by fNDF levels.. Voluntary water intake increased linearly as it was increased the fNDF levels in the diet. The digestibility coefficients of organic matter (OM), neutral detergent fiber (NDF), ether extract (EE) and total digestible nutrients (TDN) were affected quadratically (P ≤ 0.048) with fNDF levels. Ruminal pH was linearly increased (P = 0.001) by fNDF levels, ranging from 5.44 to 5.81, for the diets containing 0 and 463 g/kg of fNDF, respectively. Microbial protein was quadractically affected (P<0.001) of fNDF level, with highest average value observed when diet contained 109 g/kg of fNDF (407.06 mg/dL). On the other hand, the increase of fNDF levels did not affect (P ≥ 0.105) the concentration of ruminal NH3-N, rumen VFA concentration, and molar proportions of acetate, propionate, butirate and acetate to propionate ratio. The fNDF levels promoted a linear increase (P = 0.006) on chewing time and linearly decreased (P = 0.007) on resting time. The inclusion of levels from 109 to 339 g/kg of forage neutral detergent fiber provides favorable conditions for ruminal function, digestibility and feeding behavior in goats fed diets cactus pear based. Animals fed diets with fNDF below 109 g/kg had compromising on ruminal fermentation with drastic decrease in the rumination and nutrients digestibility.