Pending CRIS Projects:

3655-31000-017-02R Glen Broderick

IMPROVING THE EFFICIENCY OF RUMINAL AMMONIA NITROGEN UTILIZATION FOR MILK PROTEIN SYNTHESIS AND REDUCING NITROGEN LOSSES IN DAIRY COWS

Objectives: There is evidence that rumen protozoa impair protein utilization by dairy cows. Feeding medium-chain fatty acids, such as lauric acid, has been found to suppress protozoa numbers, and reduce ammonia levels in the rumen. The objective of this research is to test the effectiveness of lauric acid, when fed at a dietary concentration that was established in related research, to reduce protozoal numbers and improve protein efficiency of lactating dairy cows.

Approach: Forty-eight dairy cows from the Dairy Forage Research Center herd will be placed in 12 groups of 4 (2 groups with rumen cannulas). Cows will be fed a control diet (40% grain) for a 4-week covariate period, then randomly allotted to: a control diet or a diet with 60% of grain replaced by pectins and sugars, or these same two diets with added lauric acid. Diets will be fed for 12 weeks. Milk yield and feed intake will be measured daily. Milk composition will be determined every 2 weeks during the 4-week covariate and the 12-week experimental periods. Spot urine and fecal samples will be taken to estimate urinary excretion of purine derivatives (an estimate of rumen microbial protein) and apparent digestibility of dietary nutrients. Every 4 weeks during the 12-week experimental period, rumen-cannulated cows will be sampled to determine protozoal numbers and concentrations of ammonia and volatile fatty acids. Increased nitrogen efficiency and urinary purine derivatives, plus reduced levels of rumen protozoa and ammonia, would indicate that lauric acid suppresses protozoa, thus improving nitrogen utilization.