Feeding Fat to Cows

1 Feeding FAT to Cows Feeding vegetable fats during lactation can increase the number of cows that are cycling by breeding season. B Y H E A T H E R S M I T H T H O M A S. C ow nutrition is dependent upon adequate energy, protein, vitamins and minerals in a balanced diet, make progesterone, Williams continues. It can't synthesize enough of its own to sustain itself. At NDSU, he and his colleagues were Williams continued his research with beef cattle when he moved to Texas A&M 16. years ago. but research is showing that fat content in a studying that progesterone relationship, cow's diet can enhance rebreeding success. A thinking they could enhance its function. Enhancing follicular growth number of studies, some still ongoing, have We did elevate circulating levels of The crux of the matter is that, when you been done on various aspects of Feeding fat.

2 Progesterone during the luteal phase (or feed a vegetable oil (a polyunsaturated fat) to Gary Williams, reproductive physiologist middle of the cycle) when we fed fat a ruminant in this case a cow you at Texas A&M University, was one of the first continually to cattle, but while it was create several metabolic changes, he says. to look into how Feeding fat would affect interesting information, it didn't necessarily For example, you change rumen beef cow reproduction. answer everything we wanted to know, and fermentation patterns to favor propionic While on the faculty at North Dakota it wasn't that earth-shattering, he admits. acid, a volatile fatty acid. You also elevate the State University insulin, which is (NDSU), Williams involved in carbohydrate started examining how and glucose metabolism. Feeding fat affected The cow doesn't use reproduction.

3 At that very much glucose; her time, the focus was on circulating glucose levels the cholesterol are fairly low compared metabolism of dairy with monogastric heifers. animals (like humans), . During lactation, Williams explains. The cholesterol cow relies more heavily concentrations in the on fatty acids produced cow's blood go very high in the rumen, though from a baseline of the central nervous around 100 milligrams system has to have per deciliter to maybe as glucose to function.. high as 300 milligrams But, he adds, insulin per deciliter, Williams has direct effects on says. There are some reproductive tissues, metabolic mechanisms particularly the ovary. unique to the cow that Insulin-like growth are probably driving this. factor (IGF-I) a It's not seen in other hormone involved in the animals, and certainly development of ovarian not seen in humans.

4 Follicles' CL function . When a cow is fed also is elevated within dietary fat, more the ovary when cows are cholesterol is synthesized fed vegetable oils long and produced, Williams term. Growth hormone explains. So if you feed is elevated in studies PHOTOS BY SHAUNA ROSE HERMEL. it during lactation, you with beef cattle. not only have the The bottom line, lactation effect in the however, is that you cow, but you have a fat enhance the growth of effect. ovarian follicles when One of the structures Feeding vegetable fats, . on the ovary that is Williams says. We've present after ovulation, measured all these the corpus luteum (CL), hormonal and is dependent on Research indicates Feeding vegetable fat to cows after they calve will improve follic- metabolic changes. cholesterol in the blood to ular development and increase the number cycling at the start of breeding season.

5 We've taken ovaries out 40 ANGUSJ ournal February 2001. and grown the cells in culture and done all kinds of fancy things to document the physiology, but the end result is that, if you feed fat to cows in marginal body condition [body condition scores (BCS) of 4 or higher on a scale of 1 to 9], you will generally be able to derive a reproductive benefit. You will enhance ovarian follicular development. If you are Feeding this during the rebreeding period, or from the time of calving until the onset of the breeding period, you will see more cows cycling.. Not just energy Williams says it is important to realize the difference between the energy value and the metabolic effects of fat. While dietary fat can provide energy to an animal in poor condition, that's not the effect he is describing. He provides this example: If you feed one group of cows a starch-based supplement (corn) containing the same amount of energy and equal calories as a second group of cows receiving fat, you will see all of the metabolic changes and the enhancement in the fat-supplemented animals that you don't see in the control Generally the most difficult to get rebred, first- and second-calf heifers usually benefit most from a fat supplement before their breeding season.

6 Group. So it is the metabolic effects of fat and the hormonal changes you create that seem For a mature, 1,100-pound (lb.) cow, that or higher, Williams recommends to be driving these changes at the level of the equals about , which supplementing fat beginning a month ovary and not just the energy, he says, translates to about lb. of whole before the breeding season starts and adding that the phenomenon has been cottonseed or lb. of high-oil-sunflower continuing for at least a month into the confirmed in several other studies in the seed. Commercial feed companies also breeding season. United States and abroad. promote high-fat supplements. Whole It takes at least three weeks of Feeding to Williams also notes a greater benefit with soybeans will work, but soybean meal or get the changes to be able to measure polyunsaturated fats (vegetable oil) than cottonseed meal won't because the oil has metabolic, hormonal and ovarian changes.

7 With saturated fats or highly been lost in processing. Williams says. And it takes six to seven polyunsaturated fats In discussing weeks to maximize those benefits.. (like fish oil), though he supplements, he says Depending on the time of year, says there is a benefit to everything boils down to continuing for a month into the breeding Feeding saturated fat. economics. Cows calving season might not be feasible. If you have a With saturated fat in excellent body lot of green grass, the cows may not eat the you'll get similar effects condition or grazing supplement. If they won't eat it, they don't on growth hormone, good forage where they need it, Williams says. but since it's more of a are not going to lose Generally the most difficult to get rebred, bypass fat (not acted on condition won't need the first- and second-calf heifers usually benefit in the rumen), you are supplement.

8 Most from a fat supplement before their not going to have much Fat supplements are breeding season. effect on rumen intended for situations If you want to intensify your breeding fermentation processes where you are definitely management and get as many cows cycling unless you simply going to be as early as possible, the fat addition to the overload the rumen supplementing anyway, supplement for a limited period of time is and disrupt the Williams says. beneficial, Williams says. We're not digestion process, he Don't ignore promoting that anybody go out and feed explains. everything that's known high levels of fat to cattle year-round; it's just To date, researchers haven't been able to about supplementing cattle on pasture, he a limited window of time that it might be use the metabolic effect of fat to reduce age warns. Supplements are generally used to beneficial.

9 At puberty in heifers or to increase allow cattle to utilize a lower-quality product superovulation rates, Williams says. or forage. They've got to contain protein, and perhaps some vitamin-mineral Feeding recommendations supplement, to allow cattle to do that. He recommends Feeding cows or heifers To gain the reproductive benefits fat levels of about 4% of total dry matter. indicated in his research for cows of BCS 4. February 2001 ANGUSJ ournal 41.