Full text
| |
| Author(s): |
Ives Cláudio da Silva Bueno
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB) |
| Defense date: | 2002-10-02 |
| Examining board members: |
Adibe Luiz Abdalla;
Ciniro Costa;
Clotilde Maria Korndorfer;
Helder Louvandini;
Dorinha Miriam Silber Schmidt Vitti
|
| Advisor: | Adibe Luiz Abdalla |
| Abstract | |
The objective of this work was to evaluate hays of distinct nutritive values in sheep nutrition regarding to microbial synthesis capacity and digestive kinetics, through in vitro, in situ and in vivo assays, based in conventional and nuclear methodologies. Six Santa Inês sheep (LW = 40±5.7 kg) with rumen and duodenum cannulas were used. Alfalfa (ALF), signalgrass (BRA) and Tifton-85 (TIF) hays were chosen due to their crude protein (CP) content (respectively, 191, 29 and 75 g.kg-1 DM). Two experimental designs were used: Latin square (3 treatments, 3 periods and 6 animals) and complete factorial (3 substrata and 3 inocula). The first one was used for assays of voluntary intake (DMI), in situ rumen degradability, rumen parameters, apparent digestibility, nitrogen balance, digesta transit and in vivo microbial protein transit and synthesis. The second one was used for in vitro assays of rumen degradability, gas production and microbial protein synthesis. Treatments presented differences (P < 0.05) in their chemical composition (DM, OM, NDF, hemicellulose, cellulose and CP). DMI of ALF was superior (P < 0.05) to BRA and TIF DMI and it reflected the strong relationship between intake and CP content in the diet. In situ and in vitro rumen degradabilities showed the poor fermentability of BRA, fact demonstrated by in vitro gas production technique. There were no differences (P > 0.05) between rumen pH values for animals fed with ALF, BRA or TIF, however, ammonia nitrogen concentration illustrated the importance of the dietary protein to guarantee a healthful rumen environment. Treatment BRA did not supply protein enough to supply the minimum amount of rumen soluble ammonia nitrogen. DM and OM apparent digestibility coefficients were superior (P < 0.05) for ALF. CP apparent digestibility presented differences (P < 0.05) between the three treatments, being ALF (0.694) the highest observed followed by TIF (0.500). CP apparent digestibility of BRA was practically null (0.001), indicating intense protein deficit, what it could be proven by nitrogen balance. The in vitro radiophosphorous incorporation for estimating the microbial synthesis showed that there was effect of inoculum (P = 0.0089), but not of period, substratum or inoculum*substratum interaction (P > 0.05). Purine derivatives technique, on the other hand, showed the differences in microbial synthesis capacity, where the greatest microbial production was observed for ALF. The general analysis of the results allowed to conclude that: i) DMI and apparent digestibility of hays were influenced by chemical composition of feeds, by microbial efficiency and by degradation, fermentation, passage and digestion kinetics; ii) feeds with low protein content had negative effect in sheep nutrient availability and in the maintenance of a healthful rumen environment; iii) in situ and in vitro techniques for estimating the degradation kinetics were compatible; and iv) fermentative kinetics (gas production) described with higher fidelity the feed degradation due to microbial activity. (AU) | |