Fat supplements for dairy

The debate as to the effectiveness of various forms of fat supplements in supplying the energy deficit to lactating dairy cows in early lactation is live. It is perhaps refreshing to review the general properties of the commercially available rumen-protected/inert fats.

Designated digestive characteristics

Fat supplements generally carry the label of "rumen-protected/inert" if they are designed to:

1) Resist biohydrogenation by rumen microbes

2) Enhance postruminal flow of fatty acids

3) Minimise negative impact on rumen fermentation

4) Have no rious effect on dry matter intake.

5) Deliver specific fatty acids to target tissues such as mammary gland

Intended Benefits of protected fats

For rumen protection technology to be effective and beneficial to the dairy cow it must:

1) Offer consistent and predictable enhancement of unsaturated fatty acid flow to the intestines above background levels

2) Provide adequate release and absorption of fatty acids postruminally

3) Have minimal adverse effects on rumen fermentation

4) Present least problems with dry matter intake

5) Enhance microbial protein yield

6) Be palatable

On a global scale there are available a variety of commercial fat supplements the main ones of which are hydrogenated fats, calcium soaps and dryfats. The first two have been in the market for a long while and have been studied widely with certain limitations identified.

Drawbacks of Protected Fats

Calcium Soaps

Many of the fatty acids of calcium salts are low in palatability and stable in the rumen at pH greater than 6.5. They are released from calcium salts primarily by acidic dissociation in the abomasum and intestine. However, the rumen conditions in high concentrate fed dairy cows hardly ever attain such pH levels to guarantee adequate protection of the calcium soaps. Indeed, several researchers Van Nevel and Demeyer (1996), Ferlay et al. (1993) and Wu et al. (1991) have found calcium salts of fatty acids to be extensively biohydrogenated (up to 57%). This demonstrates that calcium salts are not as rumen protected as claimed and may instead be rious to rumen fermentation and to dry matter intake. Similar observations were confirmed by Weiss and Wyatt (2004) when they fed calcium soap at a typical rate of 3.4% and recorded reduced dry matter intake by 5%. Associated with the decreased DMI is the decline in the yield microbial protein.

Hydrogenated Fats

Hydrogenated fats like palmitic acid are saturated and as such have minimal negative effects on rumen microbial growth and function. They have a melting point close to 60º C which is well above the rumen temperature rendering them inert to rumen fermentation. Unfortunately, the same process severely reduces their digestibility and potential for value in lactating dairy cow rations. According to Elliott et al. (1994; 1999), resistance to intestinal digestion is a major factor contributing to poor digestibility of highly saturated fats. Because of the low digestibility, oil slick in the dung is a common problem when C16 is fed.

From the feeding trials in Gernany ( J. Voigt et al., 2006) it was calculated that net energy for lactation were only 2.4, 10.1 and 16.4 MJ/kg DM or 4.0, 16.8 and 27.3 MJ/kg ME for hydrogenated triacylglyceride from palm oil, fractionated trilglyceride from palm oil and calcium soap from palm oil respectively.

Reduced Dry Matter Intake

As an example, a reasonable intake of metabolizable energy for a high yielding dairy cow consuming 24kg dry matter per day of a typical lactation ration (12.5 ME MJ/kg) would be 300 MJ/day. If 0.5kg of this diet is replaced with fat from calcium soap, the intake of ME would be expected to increase to 310.25 MJ/day. However, a reduction by 5% in dry matter intake by the calcium soap would depress overall energy intake in this example by 15 MJ and there will be concomitant ME loss of 4.75MJ. This equates to a loss in milk production by one litre.

Dryfats

Dryfats are processed on the premise that when hard and soft oils are blended together in a given ratio at a pre-determined temperature and applied on a dry carrier the outcome is a slow release and friable product. The technology enhances embedment of the oils into the matrix of the carrier material mimicking the natural protection of oils in forage. Dryfats therefore have a set of unique nutritional advantages over the other forms of fat supplements:

1. Palatable with no negative effect on dry matter intake

2. Oil blends with optimal ratio of unsaturated to saturated fatty acids

3. Synergistic effect of oil blend on digestibility, energy yield and functionality

4. Slow and steady release, not rious to rumen fermentation

5. Adequate release and absorption of fatty acids postruminally

6. Improves yield of microbial protein

Apart from the cost, the most important factors to consider when choosing a fat supplements are palatability, digestibility, and effect on dry matter intake. Do not forget, however, the cow is the final judge!

References:

Elliott, J.P., T.R. Overton and J.K. Drackley 1994. Digestibility and effects of three forms of mostly saturated fatty acids. J. Dairy Sci. 77:789-798.

Ferlay, A.,J. Chabrot, Y. Elmeddah, and M. Doreau. 1993. Ruminal lipid balance and intestinal digestion by dairy cows fed calcium

Weiss, W. P. Wyatt, D. J. 2004. Digestible energy values of diets with different fat supplements when fed to lactating dairy cows. J. Dairy Sci. 87, 1446-1454.

Wu, Z., O. A. Ohajuruka, D. L. Palmquist. 1991. Ruminal synthesis, biohydrogenation, and digestibility of fatly acids by dairy cows. J. Dairy Sci. 74:3025-3034.

Van Nevel, C. J.and Demeyer, D. I. (1996) Control of Metanogenesis. Environ Monit Assess 77-101