Effects Of Physically Effective Neutral Detergent Fiber In TMR On Rumen Fermentation, Milk Production Of Cows

The study was conducted to investigate the effects of physically effective neutral detergent fiber (peNDF) of diffferent levels containing alfalfa hay in total mixed ration (TMR) on the production of cows, which contained 3 experiments.In experiment 1, we studied the effects of peNDF of alfalfa hay on rumen fermentation in cows fed with TMR. Three healthy Chinese Holstein cows with the average weight of 550±50 kg were fitted with permanent rumen cannulas and used as experimental animals in the experiment, which were arranged into a 3×3 Latin Square. The alfalfa hay with different lengths ( 1cm, 3cm or 5cm ) was added in TMR and the weight of alfalfa hay accounted for 18% of the total ration ( dry matter basis ). Results showed that with the increasing of peNDF levels, the rumen pH, NH3-N concentration, total volatile fatty acid and fatty acid composition contents were increased and the ration of butyrate to propionate was decreased. The concentrations of propionate of the cows fed with 3cm and 5cm lengths alfalfa hay were significantly higher ( p<0.05 ) than that of those fed with 1cm. The contents of butyric acid in the group fed with 5cm length alfalfa hay was significantly higher than 1cm ( p<0.05 ).The objective of the experiment 2 was to investigate the effects of peNDF levels on the feed intake and milk performance of dairy cows. Total of twenty-one Chinese Holstein mid-lactating cows were selected as experimental animals. The parity of selected cows was 1 ( 9 cows ),2 ( 9 cows ) and 3 ( 3 cows ), respectively. A 3×3 Latin Square design was used to study the effects of different lengths ( 1cm,3cm or 5cm ) and addition levels ( 9%, 18% and 27%,DM basis ) of alfalfa hay on the feed intake and milk performance of dairy cows. Results showed that dry matter intake ( DMI ) was not significantly affected ( p>0.05 ) by levels of peNDF in the diets for all treatments. NDFI, ADFI and peNDFI1.18, were linearly increased with increasing dietary peNDF. While the level of addition was 9%,intake of NDF was significantly different between 5cm group and 1cm of primiparous cows ( p<0.05 ). The same consequence also was found peNDFI1.18 of 3cm and 5cm group ( p<0.05 ), comparing to 1cm, as well as ADFI of 3cm and 5cm group ( p<0.05, p<0.01, respectively). Both 18% and 27%, ADFI of 5cm group increased compared with 1cm significantly ( p<0.05 ), and intake of peNDF1.18 was very significant when the level of addition was 18% ( p<0.01 ). To the second parity, NDFI of 5cm group increased significantly compared with 1cm ( p<0.05 ), Intake of ADF was significantly difference between 1cm group and 3cm, Furthermore, compared with 5cm, 1cm group descended very significantly ( p<0.01 ), for peNDFI1.18, both 3cm and 5cm group were more than 1cm group ( p<0.05 ) as 9%. Additive level was 27%, ADFI of 1cm group also breakdowned compared with 3cm and 5cm group ( p<0.05, p<0.01, respectively), while peNDFI1.18 was significant between 5cm and 1cm group. Compared with 1cm, NDFI of 5cm group improved significantly, as well as peNDFI1.18 ( p<0.05 ) for the thrid parity. However, dietary peNDF did not significantly improve milk production. AS 9%, compared with 5cm group, fat and totle solid in milk of 3cm group raised significantly ( p<0.05 ), meanwhile, the content of Urea nitrogen had the same trend when the level of addition was 27% ( p<0.05 ).In experiment 3, three healthy Chinese Holstein cows with the average body weight of 550±50 kg were fitted with permanent rumen cannulas and used as experimental animals to study the degradability of the stem and leaf of alfalfa in rumen with the technology of nylon bag and scanning electron microscopy technique. The results showed that ruminant microflora attached to the epidermis of the stem and leaf around stoma within 6h. Palisade of mesophyll was rapidly degraded within 6h and then veins and spongy tissue were exposed. After 12h of fermentation, the leaf completely disappeared. Alfalfa stem epidermis was broken alfter 12h, and parenchyma, collenchyma, phloem, cambium and pith were totally degraded within 24h. After 48h, only the primary xylem and xylem-based were left. After 72h, the only undegradation part is xylem. The turn of the digestive order are skin and pith, parenchyma, phloem, collenchyma, cambium, primary xylem, xylem.