ABSTRACT Two studies were carried out to evaluate the effects of levels of soybean meal produced from damaged soybean grains replacing normal soybean meal on in vitro and in situ digestibility of ruminant diets as well as on intake, digestibility, and animal performance of growing/finishing lambs. In trial 1, we evaluated the in vitro digestibility of each soybean meals (normal and damaged), as well as diets containing levels of the damaged replacing the normal (0, 333, 667 and 1,000 g.kg−1) soybean meal on kinetic parameters of in vitro cumulative gas production, in vitro dry matter and crude protein digestibility, in situ rumen-degradable protein, rumen-undegradable protein, and in vitro intestinal digestibility of rumen-undegradable protein. In trial 2, we used 48 growing/finishing lambs to evaluate the effects of damaged soybean meal levels (0, 333, 667, and 1,000 g.kg−1) replacing normal soybean meal in feedlot diets (20:80 roughage:concentrate ratio) on intake and digestibility of nutrients and on animal performance. The damaged soybean meal presented lower values for total gas production and in vitro dry matter digestibility than normal soybean meal. Higher rumen-undegradable protein was estimated for damaged soybean meal than for the normal and consequently lower rumen-degradable protein for damaged compared to normal. Because of the lower rumen-degradable protein, damaged soybean meal promoted lower in vitro ammonium nitrogen (NH3-N) concentrations than the normal in feedlot diets. In the in vivo trial, there were no effects of damaged soybean meal levels in the diets on intake and digestibility of nutrients (dry matter, organic matter, crude protein, and fiber) as well as on total weight gain, average daily gain, carcass yield, or feeding efficiency. Thus, damaged soybean meal can fully replace the normal one in lamb feedlot diets (in up to of 1,000 g.kg−1 of the normal soybean meal) without causing adverse effects on intake and digestibility of nutrients and on animal performance.

ABSTRACT Our objective was to identify the best fit mathematical models for in vitro gas production kinetics using rumen fluid and forage plants commonly used in ruminant feed to obtain better estimates of parameters that describe the rumen fermentation. Four mathematical models were tested, two unicompartmental (M1 = first order, M2 = Gompertz) and two bicompartmental (M3 = M1 + M2; M4 = M2 + M2). Two temperate grasses were evaluated, as well as four tropical grasses and three temperate forage legumes. The fit of the models was verified by the corrected Akaike information criterion (AICcr) and the difference among AICcr values (Δr), likelihood probability (Wr), and relative likelihood (ERr). Temperate forages reached maximum gas production between 48 and 72 h. In the tropical forages, it occurred only after 72 h. In profiles in which M3 was the best choice, the values of parameters Vf 1 were higher than those of Vf 2, and k1 values were higher than k2 values. The only exception was for Tifton 85 profile, whose Vf 2 value was higher than Vf 1. The model M3 has a better fit for tropical forages with higher fiber content and lower levels of nonfibrous carbohydrates and crude protein. The model M1 has a better fit for forage with higher nonfibrous carbohydrate contents and low lignin content.

ABSTRACT The objective of this study was to simulate total dry matter intake and cost of diets optimized by nonlinear programming to meet the nutritional requirements of dairy does and growing doelings. The mathematical model was programmed in a Microsoft Excel(r) spreadsheet. Increasing values of body mass and average daily weight gain for growing doelings and increasing body mass values and milk yield for dairy does were used as inputs for optimizations. Three objective functions were considered: minimization of the dietary cost, dry matter intake maximization, and maximization of the efficiency of use of the ingested crude protein. To solve the proposed problems we used the Excel(r) Solver(r) algorithm. The Excel(r) Solver(r) was able to balance diets containing different objective functions and provided different spaces of feasible solutions. The best solutions are obtained by least-cost formulations; the other two objective functions, namely maximize dry matter intake and maximize crude protein use, do not produce favorable diets in terms of costs.

The objective of the present study was to evaluate the parameters related to the digestion of the fiber from silages of four corn hybrids (BX1280, SHS4070, 2B433, and DKB390) developed for silage production. Four rumen-cannulated castrated Holstein × Zebu crossbred cattle with approximate initial weight of 400 kg were distributed in a Latin square design. To determine the fiber passage rate and degradability, the techniques of chromium-mordant and in situ incubation of the neutral detergent fiber of the silages in nylon bags were used. The profiles of concentration of the marker in the feces were described by the generalized two-compartment model. Corn hybrid DKB390 is the most indicated for production of better-quality silages, because its fiber is more degradable in the rumen as compared with the other hybrids tested.