Valor nutritivo das silagens de três genótipos de milho em três estádios de maturação

Abstract

The aim of this work was to evaluate the voluntary intake, apparent digestibility, partition energy, methane production, degradation kinetic and ruminal in situ degradability by sheep feeding the of the three corn hybrids (BRS 1035, BRS 1031 e BRS 1001) harvested at three maturation stages (soft dought, floury and hard-floury). The dry matter intake, in grams per metabolic weight (DIM/MW) ranged from 43.36 to 62,02 g/MW/day, and the animals feeding with silages of the hybrid BRS 1001 had major DIM/MW at floury stage (P<0,05). The dry matter apparent digestibility (DMAP) ranged from 55.33 to 64.10%. The crude protein intake in grams per metabolic weight (CPI/MW) ranged from2.39 to 4.27 g/MW/day. The neutral detergent fiber intakes in grams per metabolic weight ranged from 24.62 to 35.24g/WG/day. The values of neutral detergent fiber digestibility (NDFD) ranged from 42.20 to 56.07%, and didnt change with the maturity (P>0,05) for all the hybrids. The intakes of gross energy (GEI), digestible energy (DEI) and metabolizable energy (MEI), in Kcal per kg of metabolic weight (MW), varied from 182.9 to 262.2, from 103.26 to 152.33 and 89.09 to 135.64, respectively, and the sheep feeding the silages of BRS 1035 hybrid harvested at the hard-floury stage showed highest GEI, DEI and MEI. For animals feeding with silages of the others hybrids, GEI, DEI and MEI didnt change among harvest periods. The intakes of net energy (NEI) for animals feeding silage of BRS 1035 hybrid at hard-floury stages showed higher value than the silage harvested at soft dought stage, and the silage harvested at floury stage dont differed from the previous (P>0.05). The NEI of others hybrids didnt vary among harvest periods. The feces represented the major loss of energy (37.01% to 45.36% of GEI), followed by heat increment (9.590% to 35.56% of GEI), enteric methane production (4.88% to 6.88% of GEI) and urine (0.91% to 2.04% of GEI). The value of digestible energy (DE), metabolizable energy (ME) and net energy (NE), in Mcal/kg of dry matter intakes (DMI), ranged from 2.42 to 2.86, 2.12 to 2.54, and 0.61 to 1.56. The silage of BRS 1031 showed highest value of DE and ME at the soft dought stage, and the silages of hybrids BRS 1035 and BRS 1001 didnt change among harvested periods. The silage of BRS 1035 showed lower value of NE at the soft dought stage, and the silages of hybrids BRS 1031 and BRS 1001 didnt change among harvested periods. The consumption of oxygen and production on carbon oxide ranged from 23.0 to 32.06 L/MW and 21.05 to 27.43 L/MW, respectively. The methane production ranged from 1.15 to 1.74 L/MW, and did note differ with harvest periods. The heat production ranged from 113.62 to 155.84 Kcal/MW. The value of respiratory coefficient (RC) varied of 0.83 to 0.94. The methane production in liters for day (20.82 to 32.55 L/day), grams for day (0.82 to 1.24 g/day), grams for Kg of dry matter intake (17.36 to 22.78 g/kg of DMI) and grams for Kg of digestible dry matter intake (29.75 to 38.68 g/Kg of digestible DMI), dont change among the silages harvested at different stages. By evaluation utilizing the semi-automated in vitro gas production, after 96 hours of fermentation, dont change the gas production cumulative (GPC) among silages harvested periods for all hybrids, and values ranged from 254.18 to 282.05 ml/g of DM. The silages maximal degradation potential for all hybrids decreased with advanced maturity stages, and ranged from 259.32 to 279.96 ml/g of dry matter. The effective degradability values were highest to silages harvest at soft dought stage. By the ruminal incubation in situ technique, the silages of BRS 1035 and BRS 1001 hybrids showed highest potentials degradability (PD) from silages harvested at hard-floury stage. The silage of BRS 1031 hybrid showed higher of DP from silage harvested at stage floury. The values of effective degradability at 2%/h ranged from 51.69 to 59.66%. The values of organic matter ruminal degradability showed the same behavior of dry matter ruminal degradability. According to the results obtained in various experiments, for hybrid BRS 1035 the maturity stage recommended for silage is hard-floury, already for the BRS 1031 is the floury stage, while the BRS 1001 is soft dough stage.