Effect Of Changing The Wildrye Size And Steamed-corn Adding Ratio On Diets Influenced Rumen Fermentation Conditions

V This study includs the following contents:By changing the partical size on diets, acquire the most appropriate one by monitoring the ruminal acidity. Meanwhile, by changing the proportion of steam-flaked corn on diets to change the proportion of rumen degradation starch(RDS), establish suitable particle size and adding porprotion for dairy production.Experiment 1 Effects of varying diets particle size on ruminal acidity environments.This experiment was conducted to investigate the effects of different changes in wildrye particle size on ruminal VFA(volatile fatty acids) production and the influence of p H value. This experiment was designed as a 4*4 Latin square using four Holstein cows in dry period with rumen-cannulated.Diets were chemically similar but varied in forage particle size(2cm、4cm、8cm and 18cm). They were divided into 4 groups(4 trial time) and first 14 days to adjust the diet and last 12 days for experiments. The results showed that reducing wildrye particle size altered particle of diets, in 2 cm,declined ruminal p H and increased TVFA(total volatile fatty acids) production is significantly higher than 4 cm, 8 cm and 18 cm(P < 0.01); after feeding 2 hours(9:00-11:00), ruminal p H differences between four groups were significant(P < 0.01), the acetic acid content in 2 cm group was significantly higher than 4 cm, 8 cm and 18 cm(P < 0.05), and acetate/ propionate ratio of 2 cm was significantly higher than 4 cm, 8 cm and 18 cm(P < 0.05). Therefore, the effects of four changes in wildrye particle size on ruminal p H in varying time had difference significantly, and so were the acetic acid and propionic acid,it changed the rumen fermentation type. This study indicates that it would produce certain adverse effects no matter whether the diets particles were too big or too small.Experiment 2 Effects of changing the proportion of rumen degradation starch on ruminal acidity environments.On the basis of experiment 1, maintain the most appropriate particle size on diets. Diets were chemically similar but varied in steam-flaked corn added(0%,30%,60%,100%). They were divided into 4 groups(4 trial time) and first 14 days for animals to adjust the diets and last 12 days for experiments. According to steam-flaked corn adding ratio: 0%, 30%, 60%, 100% in 4 groups, the rates of ruminal degradation starch(%)were 62.97、71.85、80.74 and 89.63.The results showed that reducing steam-flaked corn ratio of diets, declined ruminal p H significantly(P < 0.01); As increasing steam-flaked corn ratio of diets, the propionate acid content and TVFA(total volatile fatty acids) content was significantly higher than three other groups(P < 0.01), and acetate/ propionate ratio of high steam-flaked corn added significantly lower than three other groups(P < 0.01),it had changed the ruminal fermentation type. Therefore, the effects of feeding steam-flaked corn in varying proportions on ruminal p H in varying time had difference significantly, and so were the propionate acid, it had changed the ruminal fermentation type. This study indicates that adding steam-flaked corn in dairy diets play an active role.In conclusion, this study draw the following conclusions:(1) It makes a significant effects on rumen acidity and rumen fermentation type by changing the particle size of diets. According to the rumen p H after diets within 12 hours, the optimal length of wildye is 8cm for dry milk cows.(2) It makes a significant effects on rumen acidity and rumen fermentation type by changing the ruminal degradation starch of diets. According to the rumen p H after diets within 12 hours, the optimal porprotion of adding steam-flaked corn is 30% for dry milk cows.