The effect of dietary methionine levels on endogenous nitrogen and endogenous amino acids flows in growing goats.

The effect of dietary methionine (Met) levels on endogenous N and amino acids (AA) flows at different part of the digestive tract of growing goats was determined using a (15)N isotope dilution technique. Three goats (25 ± 2.5 kg) were fitted with the ruminal, duodenal and ileal cannulae and allocated to three dietary treatments in a 3 × 3 Latin square design. The dietary treatments consisted of a total mixed ration containing three levels of Met (0.15%, 0.25% and 0.35%) respectively. It was found that at 0.15% Met level, the lowest flow in endogenous N and total AA at the duodenum and ileum occurred. The endogenous N secretion contributed to 26% and 23% of the duodenal and ileal total N flows, respectively, and the proportions were not affected by the dietary Met levels. The duodenal and ileal flows of endogenous total AA were 11.1, 11.8, 11.3 g/d and 2.9, 3.9, 4.1 g/d respectively. The average real digestibility of N was 65%, 87% and 95% in the forestomach, intestine and whole digestive tract respectively.

Morphological fractions, chemical composition and in vitro fermentation characteristics of maize stover of five genotypes.

Five morphological fractions (leaf blade, leaf sheath, stem, husk and cob) of stover of five maize genotypes, namely waxy, conventional, fodder, sweet and high-oil maize, respectively, were used to test the effects of genotype and morphological fractions on chemical composition and in vitro fermentation characteristics. The waxy maize had a higher (P < 0.05) stem but lower (P < 0.05) leaf blade proportion and fodder maize had a higher (P < 0.05) leaf blade but lower (P < 0.05) leaf sheath proportion than other genotypes, respectively. Maize genotype had a significant effect (P < 0.001) on the chemical composition of stover parts except for organic matter (OM) concentration. Chemical composition of stover parts was affected (P < 0.001) by morphological fractions. The interaction effects between genotype and morphological fraction on the fiber content of stover parts were significant. Over 0.40 and 0.50 of phosphorus (P) and crude protein (CP) of whole-plant maize stover were averagely contributed by leaf blade. Leaf blade, stem and cob contributed over 0.75 of OM, CP, P and fiber in the whole plant. There were significant effects of genotype and morphological fraction on both in vitro gas production parameters and in vitro organic matter disappearance of maize stovers. The genotype and morphological fraction of maize stover and their interaction had significant effects on NH3-N and total volatile fatty acid concentration and the molar proportion of volatile fatty acid in the supernatant after 72 h of incubation except for valeric acid. The present data indicated that the genotype and morphological fraction of maize resulted in variation in the nutritive value of maize stover.

Effects of yeast culture and fibrolytic enzyme supplementation on in vitro fermentation characteristics of low-quality cereal straws.

The effects of yeast culture and fibrolytic enzyme preparation (containing cellulase and xylanase) on in vitro fermentation characteristics of rice straw, wheat straw, maize stover, and maize stover silage were examined using an in vitro gas production technique. Four levels of yeast culture and fibrolytic enzyme supplements (0, 2.5, 5.0, and 7.5 g/kg of straw DM, respectively) were tested in a 4 x 4 factorial arrangement. Supplementation of yeast culture increased the cumulative gas production, theoretical maximum of gas production, rate of gas production, IVDMD, and in vitro OM disappearance (IVOMD), and decreased the lag time for each type of straw. Fibrolytic enzyme supplementation tended to increase cumulative gas production, theoretical maximum of gas production, and rate of gas production; prolonged lag time of gas production; and enhanced IVDMD and IVOMD for 4 types of cereal straws, with the significance of this effect being dependent on the level of supplemented enzymes. There were significant interactions between fibrolytic enzymes and yeast on all in vitro gas production parameters, IVDMD, and IVOMD of each type of straw. The outcome of this research indicated that the application of fibrolytic enzyme preparation and yeast culture could improve in vitro gas production fermentation of cereal straws.

Effects of dietary methionine and lysine sources on nutrient digestion, nitrogen utilization, and duodenal amino acid flow in growing goats.

This study investigated the effects of supplementation of various sources of Met and Lys on nutrient digestion, N utilization, and duodenal AA flows in growing goats. Four 4-mo-old Liuyang Black wether goats were used in a 4 x 4 Latin square experiment and were assigned to 4 dietary treatments: (1) control, (2) control + lipid-coated Met-Zn chelate and Lys-Mn chelate (PML), (3) control + Met-Zn chelate and Lys-Mn chelate (CML), and (4) control + dl-Met, l-Lys-HCl, ZnSO(4).7H(2)O, and MnSO(4).H(2)O (FML). Compared with control, PML reduced (P < 0.05) ruminal NH(3) concentration, urinary N excretion, and plasma urea N concentration and increased (P < 0.05) the activity of ruminal endo-1,4-beta-d-glucanase and beta-glucosidase, the duodenal flow of N, N retention (g/d as well as % of absorbed N), the duodenal flows of Met, Lys, His, Val, and total essential AA, and plasma concentrations of Lys, Val, Phe, and total essential AA. Supplementing Zn-Met and Mn-Lys chelates had similar (P > 0.05) but lesser effects on these measures compared with PML, and the effects on most of the measures were not statistically significant (P > 0.05) when compared with control. Supplementing free-form Met and Lys had no effects compared with control (P > 0.05). The results indicate that lipid coating and chelating of AA provide a protection, and to a lesser extent by only chelating, of the AA from microbial degradation in the rumen and possibly has effects on rumen fermentation, which increases MP supply. This technology could improve productive performance and be of potential benefit to ruminant production if cost-effective products are developed.