Effects Of Different Ratios Of Dietary Starch To Neutral Detergent Fiber On Rumen, Blood, Milk And Feces Metabolism Status In High Producing Lactating Cows

The study aimed to investigate different ratios of dietary starch to neutral detergent fiber (NDF) from different forage sources on the lipopolysaccharide (LPS) concentrations in the rumen fluid, artery and venous blood, milk and feces, and the associated metabolites, as well as the correlation among different measurements in lactating dairy cows at peak milking period, which could serve as the indirect indicators to evaluate the health status of rumen in the dairy cows, and provide the information to the dairy cows producers to manipulate the diets to maximize the milk production while maintaining the health rumen status. In the present study,10within100d post-partum dairy cows with similar body condition and parity were selected from1of3different farms:Liangcheng (LC), Gucheng (GC) and Shenniu (SHN) farms, respectively. Rumen content, artery and venous blood, milk, feces and urine were collected and analyzed for the pH, LPS and other acidosis-related metabolites concentrations; all the data will be analyzed using SAS9.0software. The diets and characteristics from3different farms were as follows:1) LC farm diet; roughage were consisted of imported alfafa, high quality Grass hay and corn silage; ratio of starch to NDF in the total mixed ration (TMR) was1.15:1;2) GC farm diet; roughage were consisted of imported alfafa, Grass hay and corn silage; ratio of starch to NDF in TMR was1.21:1;3) SHN farm diet; roughage was only provided by corn straw; ratio of starch to NDF in TMR was1.39:1.During this study, all the experimental dairy cows were healthy with no observed disease, normal feed intake and milk yield. The results showed that the rumen pH from cows in GC farm were significant (P<0.05) lower than the cows from LC farm, while there was no difference between GC farm and SHN farm in terms of rumen pH. Among the cows from GC farm,50%of the cows were within the category of sub-acute ruminal acidosis (5.8-5.5) in terms of rumen pH. Additionally, the LPS concentrations in the rumen fluid was highest in cows from GC farm, and lowest in LC farm, with the SHN farm in the middle, however, there was no difference among the cows from the3farms. Acetic acid, butyric acid, propionic acid and total volatile fatty acid concentrations in rumen fluid were significant (P<0.05) higher in the cows from GC farms compared with the cows from LC and SHN farms. Lactic acid concentration in rumen fluid was highest in cows from GC farm and significant greater (P<0.05) than the cows from SHN farm, while there was no difference between cows from GC and LC farms. Furthermore, LPS concentrations in caudal vein and mammary artery in the cows from the3farms were below the detection limit (0.05EU/ml) of the analytic kit. Serum glucose, total protein and albumin concentrations in cows from LC farm were significant (P<0.05) greater compared with the cows from GC farm, however, there were no differences between cows from GC and SHN farms. Among the3farms, the serum aspartate transaminase (AST) and alanine transaminase (ALT) in the cows from GC farms were significant (P<0.01) higher than the cows from LC and SHN farms. Serum cholesterol concentration was the greatest in the cows from LC farm and significant (P<0.05) higher than the cows from GC and SHN farms. Additionally, the fecal LPS concentration in cows from GC farm was the lowest, however there was no difference among the cows from the3farms. However, the fecal moisture content in cows from GC farm was significant (P<0.05) higher compared with cows from LC farm, while there was no difference between cows from GC and SHN farms.