Effects of the source and level of rumen undegradable protein and corn processing on production performance of dairy cows

It has been demonstrated that processing of grain increases the energy available to the microorganisms of the rumen and increases microbial protein production, but the effects of processing of dietary carbohydrate (corn) source on protein requirements of dairy cattle and the interaction effects of corn processing and rumenundegradable protein (RUP) level on performance of Holstein cows fed low forage diets, is not considered. The objective of this study was to investigate the interactions between RUP level with corn processing method and dietary RUP sources on production performance of high- producing Holstein dairy cows fed a high concentrate diet.
In order to determine the interactions level and sources of RUP with corn processing method on production performance of high-producing Holstein dairy cows two separate experiment were conducted. In the first experiment, 12 lactating Holstein cows (48±3 kg/d milk yield) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments that included four treatments. In the second experiment, eight lactating cows were used 4 × 4 Latin square design that included four treatments. Treatments one to four in the first experiment consisted of diet containing 1) RUP equal of 40 percent based on crude protein (CP) and grinding (GC) corn 2) RUP equal of 40 percent and steam flaking (SFC) corn 3) RUP equal of 35 percent based on CP and GC 4) RUP equal of 35 percent and SFC. The CP level in diets was same and equal to 16.7 percent based on dry matter and level of RUP and corn processing were different between diets. Treatments one to four in the second experiment consisted of diet containing xylose treated Soybean meal, fish meal, meat meal, and the mixed of fish and meat meal as RUP sources, respectively.
In the first experiment the level of RUP had no significant effect on dry matter intake (DMI), but reduction in RUP level from 40 to 35% based on CP (or increase RDP level from 60 to 65% of CP) the milk production was increased (average 43.2 vs. 44.4 kg/d, respectively). Cows receiving steam flaked corn had lower DMI rather than who received grinding corn (average 25.1 vs. 26.2 kg/d, respectively). Corn processing method had no significant effect on milk yield. However, fat corrected milk was reduced in cows receiving steam flaked corn compared with those receiving ground corn. Steam flaked corn, increased protein and reduced milk fat percentage. Overall, no significant main treatment interaction effects were observed on dairy cow's performance. The result of second experiment showed no significant effect of RUP sources on DMI, milk yield and composition in high-producing Holstein dairy cows under the conditions of the present study.
No significant interactions of main treatment effects occurred for lactation performance data, but on the grounds of their lower costs, lower RUP level and ground corn, also the use of meat meal as RUP source may be more economical and can be effective feeding strategy to recommended for diets of lactating dairy cows receiving high concentrate diets.