Ruminal Fat Digestion and Metabolism

Transcription

1 Ruminal Fat Digestion and Metabolism Charles J. Sniffen Fencrest, LLC, Holderness, NH Introduction We have been using ether extract for the formulation of rations for many years. With NRC 2001, we moved to recognition that there was a need to move beyond ether extract. There is a correction for the non-lipid components extracted by ether. The general correction is: FA (%) = EE (%) 1. This corrects for both the pigments, other ether soluble but non lipids and glycerol which is the backbone of the fat, but is not fatty acids. We have always been feeding fat to dairy cows. Historically we have fed it mostly from the feedstuffs that we normally feed to cows our forages, corn or barley and SBM. We started feeding higher fat products about 20 years ago. Cottonseed, roasted beans, tallow became common. I remember about 15 years ago when tallow tanks were popular in Michigan. We then began to talk about being careful, feeding too much vegetable fat. We did talk about unsaturated fat. Spartan has vegetable fat as a % of the EE. With the introduction of Ca salts of fatty acids from the research done at Ohio State, the whole technology of feeding fat moved ahead. It is that technology that we are going to discuss. The lipid sub model will be used that is in the platform of CPM dairy which uses the CNCPS model as the basis for its calculations. Lipid Basics When you put tallow in the ration, you should know a few things about the tallow you purchase. The non-nutritive value is called the MIU and is comprised of unsoponifiables polymers of oxidized fatty acids, cholesterol, and impurities such as bone and hair. The MIU should be less than 2-3% (personal communications, Palmquist, 2005). Moisture should be less than 1%. The iodine value (IV) is a measurement of the degree of unsaturation. IV s over 60 have a high ruminal activity. Fats with an IV less than 30 have lower digestion in the small intestine and are not ruminally active. Glycerides with an IV of 50 is suggested to be optimal for the ruminant (Palmquist), however fat mixtures with a IV of 15 can be well digested. The bottom line, if you are going to put tallow or vegetable tallow blends in the ration know your qualities, your moisture and the IV. What are lipids? Lipids range from 40 to 98% of the EE in feedstuffs that we are routinely feeding. The lipid itself is in the form of what we call a glyceride. This is a glycerol with one, two or three fatty acids attached. The chain length and the degree of unsaturation characterize these fatty acids. The major feedstuffs that we feed are vegetable in nature and have lipids that are highly unsaturated. Table 1 is a typical fatty acid analysis of feeds fed in a high producing ration. First you will note that the Total Fatty Acid (TFA) analysis as a %DM and as a % of EE are variable, ranging from 50% to 100% of EE. Next, note that the glycerol and pigment is variable. The glycerol is a function of the TFA and the pigment will be a function of the feed but that shown in Table 1 is the EE (TFA + Glycerol). The FA s are a percentage of the total TFA, %DM. The FA symbols provide information on carbon numbers and degree of unsaturation. For instance, C18 means that there are 18 carbons in the FA. C18:0 means that there are no double bonds in the molecule. C18:2 means that there are 2 double bonds in the

2 96 Table 1. Typical fatty acid analysis of feeds fed in a high producing ration. Feed Name EE TFA dm TFA ee Glycerol Pigment C12:0 C14:0 C16:0 C16:1 C18:0 C18:1T C18:1C C18:2 C18:3 Other AlfSil20Cp40Ndf17LNdf CrnSilPr30Dm45NdfCrse AlfHy20Cp40Ndf17LNdf WhtStr5Cp79Ndf16LNdf CornGrainGrndFine SoybeanHullsPellet MolassesCane CottonseedWhlwLint Megalac MegalacPlus SoybeanML47.5Solv CornDistEthanol CornGlutMeal60% SoyPLUS BloodMeal Porcine SeaLac Mepron MinVit

3 molecule. The more carbons without a double bond the higher the melting point. The more double bonds the lower the melting point. Butter made from cows eating pasture in the summer will have a lower melting point, because more FA with double bonds reach the mammary gland. We also will experience lower fat tests in these cows and better reproduction. We will come back to that. It is noted above that a high percent of the TFA in feeds from vegetable sources is C18:2, C18:3 and higher. Tallow from ruminants although not shown above is very low while porcine tallow will be high. If you contrast SeaLac with Porcine blood meal, you will note that SeaLac, a fishmeal is low in 18:2 but high in other FA. The other FA are C20 FA with 3 double bonds or more, making a low melting point. We call these FA s the Omega 3 FA, which have been shown to biologically important in humans and they think in cows. We assume that the FA in feeds is in the form of triglycerides. Remember, we did note above that there can be a high MIU where there has been an excess of oxidized fatty acids formed (cows will avoid) in the tallow s received at the mill. In order for these FA to be active in the rumen, they need to be separated from the glycerol in the rumen to form free FA and glycerol. This process is called lipolysis. This happens very quickly except for heat-treated soy products which will be lower. Ingredients with a low lipolysis rate will have more of the lipid escaping rumen action. The free unsaturated FA will be rapidly biohydrogenated to a higher saturation state. For example C18:2, Linoleic, will go to C18:1 then to C18:0, Stearic. Formulation Results The Fatty Acids consumed from the feeds in Table 1 ration is also in Table 2. The table shows the individual FA from each feed the total individual FA for the ration and the total FA for each feed and for the ration. Even though the fat content of the forages is low, the FA consumed is significant. Note the high amount of C18:2 and C18:3 consumed in Table 2. When these FA become too high then there can be negative effects in the rumen. You will also note the low amount of C18:0 consumed. This is not untypical. We can increase this significantly through feeding beef tallow or hydrogenated fat. Also, note that there is a significant 18:2 and 18:3 from the forages and the corn. We are not going to change these feeds because of the need for forages and energy, if we are concerned about the level of unsaturated FA in the rumen. This will bring us, usually to about 3% EE in the ration. The same format as shown in Table 2 is also in Table 3 for the predicted flow of FA to the duodenum. Note the significant changes in the FA appearing at the duodenum in Table 3. C18:0 has increased significantly and the unsaturated FA decreased. The FA that we watch is the C18:1T. This is a surrogate for the FA that the group under the leadership that Dr. Bauman have identified as being responsible for milk fat depression in dairy cows. The FA that has been identified is trans-10, cis-12 CLA. As little as 3 to 5 g/day can elicit a 20% depression in milk fat. This is occurring at the mammary gland. The Cornell group continues to study other trans acids to identify the additional acid that could be depressing milk fat. We have found that if this number goes above 100 g/ day that we need to restructure the ration. Moving the cottonseed to 3 or 4 lbs plus adding 2 to 3 lbs of distillers will drive this FA over 100 g/day. By bringing this below 100 g we have seen as much as 0.3 to 0.4 % increases in milk fat. Admittedly, this is only a beginning estimate, but it is better than what we were using before. A step ahead, with better fine-tunes to come. One of the areas that we did not discuss earlier is the Ca salts of FA. You will note that there is not any glycerol. The Ca makes the FA non-reactive in the rumen. If the rumen ph goes very low then the Ca dissociates and the FA can become reactive. One of the original concepts that the Ohio team under the leadership of Dr. Palmquist, Ohio State, put forth is that the Ca salts provide more flexibility in meeting the energy requirements of the cow, requiring less starch and better controlling rumen ph. If this concept is followed then the Ca salts will be relatively inert in the rumen. You will note in tables above that the Ca salts are not very inert. The final discussion is the digestibility of the FA. There is a fair amount of controversy surrounding this area. There is a significant amount of research that demonstrates that the higher the C18:0 or stearic acid is in the duodenal mix the lower the lipid digestibility. Table 4 is a summary of the earlier tables. This shows the variability in the digestibility of the FA. This is based on the published controlled studies conducted with lactating cows and is of course 97

4 98 Table 2. Intake of Fatty Acids. Fatty Acids - Intake (g/d) C12:0 C14:0 C16:0 C16:1 C18:0 C18:1T C18:1C C18:2 C18:3 Other Total AlfSil20Cp40Ndf17LNdf CrnSilPr30Dm45NdfCrse AlfHy20Cp40Ndf17LNdf WhtStr5Cp79Ndf16LNdf CornGrainGrndFine SoybeanHullsPellet MolassesCane CottonseedWhlwLint Megalac MegalacPlus SoybeanML47.5Solv CornDistEthanol CornGlutMeal60% SoyPLUS BloodMeal Porcine SeaLac Mepron MinVit

5 Table 3. Duodenal of Fatty Acids. Fatty Acids - Duodenal (g/d) C12:0 C14:0 C16:0 C16:1 C18:0 C18:1T C18:1C C18:2 C18:3 Other Total AlfSil20Cp40Ndf17LNdf CrnSilPr30Dm45NdfCrse AlfHy20Cp40Ndf17LNdf WhtStr5Cp79Ndf16LNdf CornGrainGrndFine SoybeanHullsPellet MolassesCane CottonseedWhlwLint Megalac MegalacPlus SoybeanML47.5Solv CornDistEthanol CornGlutMeal60% SoyPLUS BloodMeal Porcine SeaLac Mepron MinVit Ration

6 100 Table 4. Fatty Acids Summary. Fatty Acids- Summary Intake Lipolysed Duodenal Absorbed Fecal Digested g/d g/d g/d g/d g/d % Duodennal C12: C14: C16: C16: C18: C18:1T C18:1C C18: C18: Other Ration meant as a first stage moving beyond ether extract. It is recognized that with all of the active research that is now going on that there will be changes in this model. The exciting thing is that it provides the beginning platform for formulating for individual FA. With time, we will be able to expand beyond the C18 FA to the C20+ FA. The analytical methodology is better now. We will also have more data on the trans FA so we will be able to expand here also, so that we may not need to use the surrogate 18:1T. Our understanding of the importance of the absorbed FA is just beginning. Our focus has been on meeting the energy requirement of the cow. We now know that the FA appearing at the mammary gland not only affects the milk composition but the synthesis of milk fat. Relative to milk composition the CLA in milk fat has been shown to be powerful anticarcinogens. We need to understand better how to influence this through ration formulation. They are now discovering that the unsaturated FA absorbed might be influencing reproductive performance. They are just at the beginning in understanding that. We are at the beginning of a completely new era of opportunity in ration formulation. Formulation Summary In the mean time, what do we do now? I formulate rations in levels. If the EE is at 5%, I look very closely at the sources of fat in the ration. I do use CPM routinely, so I have access to the lipid sub model in CPM. I do check the duodenal 18:1T. Most people do not use CPM. What do you do? Look at your FA sources. If you have FA coming from bakery products, distillers (check fat in the distillers you are using), cottonseed and other fat products such as tallow blends. I manipulate these to about 4% in the ration. I then can use either Ca salts and or tallow. I will use only beef tallow and then only if there are the assurances of quality with lab analyses. Earlier I indicated that stearic has a lower digestibility. Tallow is high in stearic. The price needs to be low enough on tallow to offset the lower digestibility versus using Ca salts. I think that the hydrolyzed fats are an alternative but, again they will be lower in digestibility. In short, we can get into a discussion in ration space, and the cost of absorbed FA. Remember above feeding pasture cows was mentioned. This came together in Australia. Some Australian pasture samples had been analyzed for EE and for FA. The EE was over 8% DM. The

7 unsaturated FA as a percentage of TFA was very high, with a lot of it being C18:3. The cows on lush pasture suffer low milk fat but seem to improve on reproductive performance. As we walked these pasture it hit us that a lot of trans acids must be produced (remember the CLA content of milk is highest from cows on pasture). Also the C18:1T must be high. Why is there reproductive performance enhancement? Well we theorized that the cows are taking a lot of liquid in with the pasture consumption, which might be increasing ruminal liquid turnover, washing out more Linoleic and Linolenic which have been implicated in the reproduction area. Sound familiar? Maybe a bit of a stretch, but interesting at any rate. 101 References Chalupa, W The Cornell, Penn, Miner Dairy model: 3.07a. University of Pennsylvania. Fox, D.G., L.O. Tedeschi, T.P. Tylutki, J.B. Russell, M.E. Van Amburgh, L.E. Chase, A.N. Pell, T.R. Overton. The Cornell Net Carbohydrate and Protein System model for evaluating herd nutrition and nutrient excretion. Anim. Feed Sci. & Tech. 112:29 Moate, P. J., W. Chalupa, T.C. Jenkins, and R.C. Boston A model to describe ruminal metabolism and intestinal absorption of long chain fatty acids. Anim. Feed Sci. & Tech. 112:79