Avaliação nutricional de silagens de cana-deaçúcar com aditivos

Abstract

Sugarcane is a very important fodder plant in the animal nutrition. Usually, it is picked, cut and supplied to animals, daily. Its daily cut presents some inconveniences as the labor demand which should reduce by means of silage. However, that silage presents intense alcoholic fermentation by yeasts, causing reduction of its nutritional value, being necessary some additive that controls the action of those yeasts. Thus, this work aimed to evaluate the nutritional quality and the in situ rumen degradability of silages of two sugarcane varieties, treated with different additives. In the evaluation of the nutritional value an entirely randomized design was used, with factorial scheme 2 x 6 being two sugarcane varieties (IAC 86-2480 and RB 86-7515), and five additives (urea, NaOH, CaO, milled corn grain and Lactobacillus buchneri) plus the control (no additive), with three repetitions. The doses of additives for each treatment in relation to the green matter were of: 1% of urea, 1.5% NaOH, 2% CaO, 5% milled corn grain. As for the inoculant, NCIMB 40788 of Silo Max® commercial Inoculant was used in the dose of 2.5 x 1010 UFC/g of forage. Cylindrical experimental silos of PVC were used. The silages were analyzed as for the content of dry matter, crude protein, neutral detergent fiber and acid detergent fiber, hemicellulose, cellulose, lignin, ethereal extract, ashes and no fiber carbohydrates. The additives NaOH, CaO and corn elevated the dry matter content of the silages, and the crude protein content was larger just in the silages treated with urea, while the other treatments were not different amongst themselves. The NaOH and CaO reduced the content of neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose and lignin of the silages; however, the ethereal extract values were not different among the treatments. The values of ashes and no fiber carbohydrates were larger in the silages with NaOH and the CaO. The silages treated with NaOH, CaO are of better nutritional value, because they present higher content of dry matter and lower fibrous fraction one. The IAC 86-2480 variety presents better nutritional value in relation to RB 86-7515 one, due to the highest dry matter content and the lowest no fibrous fraction content. The in situ degradability was also carried out according to randomized blocks design in factorial scheme 2 x 6. In the study of ruminal degradability, three crossbred steers were used, fistulated in the rumen, with medium weight of approximately 450 kg. The technique of nylon bags incubated in the rumen was used. The samples were incubated in the times of 0, 6, 12, 24, 48, 72 and 96 hours. The foods and the remaining residues in the nylon bags, collected in the rumen, were analyzed as for the content of dry matter, crude protein and neutral detergent fiber. In the ruminal degradability, NaOH and CaO increased the values of the soluble fraction and the effective degradability of the dry matter of the silages. The soluble fraction and the effective degradability of the crude protein were larger in the silages with urea. As for the potentially degradable insoluble fraction, the non degradable fraction and the potential degradability of the neutral detergent fiber, there was not difference among the treatments. The effective degradability of the neutral detergent fiber of the two varieties was larger in the silages with NaOH and CaO. The silages treated with NaOH, CaO are of better nutritional value, because they present larger effective degradability of dry matter and neutral detergent fiber. The IAC 86-2480 variety presents better nutritional value than RB 86-7515 one, due to greater effective degradability of dry matter.