Rumen Transformations of Lipid – Dr. Tom Jenkins
July 27, 2012
Dr. Tom Jenkins of Clemson University covers the dramatic changes that rumen microbials have on lipids, the role of biohydrogenation as a key pathway to preserving rumen digestion, and the impact that secondary metabolites produced through rumen lipid metabolism have on production efficiency.
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Rumen Transformation of Lipids Q&A
- Can you give an example or two of feeding conditions that causes the CLA shift from cis-9, trans-11 to the alternate pathway producing trans-10, cis-12 that has a negative impact on milk components?We are still in the process of studying the rumen environment and conditions that cause this shift, but there is well documented evidence that low pH can change the pathways of biohydrogenation and the mixture of the CLA’s produced. Another example is excessive amounts of unsaturated fatty acids… polyunsaturated fatty acids are especially known to cause this shift and because of this we need to limit the amount of unsaturated fat that we feed to cows so it doesn’t overly inhibit the microbial population and cause a shift. Another example is excessive grain or starch in the diet. Evidence suggests that especially in the case of rapidly degradable grain or starch sources, excessive amounts can cause this shift. These are three examples in literature to support there has been a shift in the type of CLAs produced.
- What are the methods to create bypass EFAs of flax lipids?There is some interest in getting some Omega-3 fatty acids that are in flax past the rumen so we can supply more to the tissues to support reproductive performance and other systems. We are limited in those technologies right now. You can feed flax and it does offer some natural rumen protection by the nature of its hard outer seed coat, but it is not fool proof: the animal does chew and creates breaks in the seed coat and we process it which can cause some changes which can expose the internal fatty acids to biohydrogenation. Other than mixing oil seeds together and somehow pelleting them in some manner to provide more protection for that hard outer seed coat, we are very limited in what we can do with flax or oils. We are at the mercy of how much the animal is going to chew it and the rumen characteristics if these oil seeds can get through or not and actually deliver more essential fatty acids to the tissues.
- What are the upper limits of PUFAs to avoid detrimental effect?We will get into more depth into this topic in succeeding webinars. We are all hoping that there is some magic number or single number that we can apply here that is going to make it easy for us to follow some guideline. In later webinars, I will talk to you in more detail about ration characteristics and the exact nature of fatty acids that are in these PUFA fat sources that we are using in order to make that decision. I will have some equations that I will share later that help give me some guidance. We’re looking at not being able to feed much more than 6%, 7% or 8% total fat in a dairy cow diet before we’re going to run the risk of running into problems. How it breaks down into PUFAs and other fat sources depends on a number of ration characteristics. Stay tuned for future webinar segments so we can discuss this topic in greater detail.
- If essential fatty acids are limiting from biohydrogenation, can this be overcome simply by feeding more fat?Feeding more essential fatty acids from flax seed, cotton seed, corn oil or soybean oil:most of it does undergo biohydrogenation and limits the supply but some does get through and the more you feed the more gets through. The problem is the risk of inhibiting rumen function and you don’t want to cross that line. Feeding more just for the sake of getting more essential fatty acids may be counterproductive if you’re feeding so much as to limit cellulose digestion in the rumen or limit intake of the animal or adversely affect milk components. We have to find that line where we don’t feed too much poly unsaturated fatty acids. Today’s webinar was more background information and we will take this basic information and pull these practical applications together in succeeding webinars.
- What should an Omega-6 to Omega-3 ratio be?The dairy cow diet it is quite skewed towards Omega-6s to low amounts of Omega-3s. What’s important is what comes out of the rumen and what we get to the body tissues. There is a big push that Omega-3s and Omega-6s should be more in balance and a push to get more Omega-3s delivered. What we need in cows and humans is to get as close as we can to a 1:1 ratio is ultimately the goal. For cows, it is very much limited by the process of biohydrogenation. We will pinpoint this number and give it more detail later on.
Dr. Tom Jenkins
Professor, Department of Animal & Veterinary Sciences
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