Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/6/2012
Publication Date: 1/15/2013
Publication URL: http://handle.nal.usda.gov/10113/56872
Citation: Faciola, A.P., Broderick, G.A., Hristov, A., Leao, M.I. 2013. Effects of lauric acid on ruminal protozoal numbers and fermentation pattern and milk production in lactating dairy cows. Journal of Animal Science. 91:363-373. Interpretive Summary: The dairy cow has a symbiotic relationship, one that is mutually beneficial with the microbes living inside her rumen (the large first compartment of the stomach). The cow provides adequate living conditions to the microbes, while the microbes provide nutrients for the cow. Microbes supply about two-thirds of the amino acids (protein building blocks) needed by the cow to make the protein in milk and her body. There are three major groups of microbes in the rumen: bacteria, protozoa, and fungi. The fungi help to digest fibrous feeds such as hay and silage, but produce very little protein. Bacteria are the major contributors of protein amino acids; however, protozoa feed on the bacteria, limiting the amino acid supply to the cow. Therefore, reducing protozoa in the rumen may increase the contribution of bacterial protein to the cow. Protozoa are known to aid in feed digestion, so their complete elimination might be undesirable. The goal of this research was to find a practical approach that farmers could use to control protozoal populations and consequentially increase bacterial amino acid supply and protein efficiency in the cow. Relatively small amounts of certain oils, such as coconut oil, have been found to suppress protozoa without negatively affecting the bacterial population and the cow’s health. Our objective was to test lauric acid, a component of coconut oil, as a practical protozoal suppressant. In experiment 1, lauric acid was dosed directly into the rumen of six cows; we found that giving 160 grams of lauric acid once a day was enough to suppress the protozoal population by 90% within two days. This dose did not reduce feed consumption and/or negatively affect digestion. In experiment 2, lauric acid was mixed into the total diet, not dosed directly into the rumen. In this trial, we found that yield of milk and milk components was not improved at any level of lauric acid, and that the concentration of lauric acid needed in the diet to suppress protozoa was much higher than that required when dosed directly into the rumen (as in experiment 1). From the results of experiment 1, we concluded that lauric acid can be an effective protozoal suppressant; we also learned that protozoa suppression has the potential to increase protein utilization by the dairy cow, which could reduce the cost of feeding and therefore improve farmers’ profitability. However, results from experiment 2 showed that, when mixed into the diet, lauric acid must be included at much higher concentrations than when dosed directly into the cow’s rumen. Further research is necessary to determine an appropriate level to feed, or to find an effective means to deliver, lauric acid for suppressing protozoa in the rumen to improve protein efficiency in dairy cows.
Technical Abstract: The objectives of this study were to evaluate lauric acid (LA) as a practical agent to suppress ruminal protozoa (RP), and to assess the effects of RP suppression on fermentation patterns and milk production in dairy cows. In experiment 1, six Holstein cows fitted with ruminal cannulae were used in a randomized complete block design trial. Cows were fed a basal TMR containing (DM basis): 15% alfalfa silage, 40% corn silage, 30% rolled high-moisture shelled corn, and 14% solvent soybean meal. Each cow was assigned to one of three treatments: 1) Control, 2) 160 g/d LA, or 3) 160 g/d of sodium laurate, all given as a single dose into the rumen via cannulae prior to feeding. Both agents showed high anti-protozoal activity when pulse-dosed at 160 g/d via ruminal canulae, reducing RP by 90% within a few days of treatment. Lauric acid reduced ruminal ammonia concentration by 60% without significantly reducing DMI. Both agents reduced ruminal free AA concentration, and LA did not affect ruminal pH or reduce total ruminal VFA concentration. In experiment 2, fifty-two Holstein cows (8 with ruminal cannulae) were used in a randomized complete block design trial. Cows were randomly assigned to one of the four diets and fed only that diet throughout the study. The four experimental diets were similar except that part of the finely ground dry corn was replaced with LA in stepwise increments from 0 to 0.97% of dietary DM, which provided 0, 83, 164, and 243 g/d of LA. The TMR contained (DM basis): 29% alfalfa silage, 36% corn silage, 14% rolled high-moisture shelled corn, and 8% solvent soybean meal. Consumption of LA mixed in the TMR did not reduce DMI, and did not affect ruminal pH and ruminal traits; moreover, milk production also was not improved. Lauric acid consumed at 164 and 243 g/d in the TMR reduced the RP population by only 25 and 30% respectively, showing that these levels, when fed in the diet, were not sufficient to achieve a concentration within the rumen that promoted the anti-protozoal effect of LA.