Responses of lactating dairy cows when fed diets with different particle size of alfalfa hay

Forage particle sizes has two opposite effects on animal performance, on the one hand fed with long particle increases ruminant activity and rumen buffer and reduce the risk of subacute acidosis, on the other hand decreases the flow rate of digestion and subsequently feed intake and milk production. Therefore this experiment was done to determine the functional response of lactating cows when fed diets containing alfalfa hay forage whit 3.09 and 4.65 mm geometric mean.
In this study was used of 8 Holstein cows similarly, with regard to the production stage, weight, age, breed and health, in rotate design 2×2 and the two period 21-day (2 weeks to adaptation with the diet and 7 days for samples) with four replicates for each treatment. During the 7 days of sampling, was measured feed intake, indicators blood and milk.
The cows DMI increased with reduced forage particle size (25 versus 22.5 kg per day). Non-fiber carbohydrates, organic matter, neutral detergent fiber, ash, and acid detergent fiber intake was reduced by increasing the particle size alfalfa hay. Physically effective fiber greater than 8 mm intanke in the experiment was statistically significant between the two treatments, that diet smaller particle size had lower levels compared to the larger particle size diet (0.41 to 0.52 kg) . With increase geometric mean particle size alfalfa hay of diet from 3.09 to 4.65 mm did production increase from 3.26 to 3.65 percent. In this experiment protein content, lactose, urea, solid nonfat, total solids, somatic cell counts of milk were not significantly different between the two treatments. By increasing the particle size of alfalfa hay increased blood glucose and triglyceride levels. Blood insulin levels was more in cows fed diets greater geometric mean alfalfa hay (16.29 and 12.86 mg per deciliter). Cholesterol levels, antioxidants, urea and beta-hydroxy butyric acid were not significantly different between two treatments of alfalfa hay particle size in diet. According to the results of this experiment, the particle size reduction of alfalfa hay and diet was decreased in the rumen fluid pH. The rumen fluid pH for diets containing alfalfa hay with geometric mean 3.09 and 4.65 was 6.09 and 6.39 respectively.
With increasing the forage particle size increased pH of the rumen fluid, dry matter intake and milk fat.