COWS' NUTRITIONAL NEEDS VARY DUE TO CIRCUMSTANCES

by: Heather Smith Thomas

Nutritional needs of cows may vary considerably, depending on age (young and still growing, or mature, or old with poor teeth), size, breed, whether or not the cow is lactating and/or pregnant, whether the weather is warm or cold. Cattle can do well on many types of forage and feeds as long is it contains sufficient nutrients to meet their needs and is provided in adequate amounts. Several basic groups of nutrients are important—energy (sugars and starches found in grains, and the complex carbohydrates of cellulose and other fibers that are broken down and digested by fermentation in the rumen), proteins, vitamins, minerals (which include calcium and phosphorus, along with salt, and the trace minerals that are crucial for a healthy immune system, reproduction, etc.) and water.

Make sure pregnant cattle have an adequate and well balanced diet with no vitamin or mineral deficiencies. Proper levels of trace minerals are crucial for a healthy immune system and optimal reproduction capabilities. Different regions may vary greatly in soil minerals; feeds in some areas may be deficient in certain elements. It's always wise to take soil and feed samples to know how best to supplement the cattle when planning your mineral program.

The nutrient requirements for protein and energy for pregnant cows will vary, depending on whether the cow is young and still growing or nursing a calf. Even though the nutrient demands for the fetus itself do not increase much until the final trimester of gestation when the fetus is growing fastest, the cow's demands in early pregnancy will still be great if she is feeding her present calf.

Heifers pregnant with their first calves need good feed. The demands of pregnancy are not great, but the heifer must be able to reach adequate size and maturity before calving. Cattle nutritionists generally recommend feeding heifers enough protein and energy between weaning and calving that they will reach at least 65 percent of their mature weight by breeding time, and 80 to 85 percent of their projected mature size and weight by the time they calve as two year olds. If the heifer will mature at 1,100 to 1,200 pounds, she should weigh at least 715 to 780 pounds when bred and 935 to 1,020 pounds when she calves.

Reproduction -- Adequate levels of various nutrients are especially important for reproduction, since the body always takes care of its other needs first. Reproduction is a luxury that won't take place unless the body's maintenance needs are met. A thin cow or heifer will not settle as readily as an individual in good flesh; if she is too thin she won't even be cycling.

Spring calving pregnant cows must be in good flesh through winter. Cows that are thin at calving take longer to start cycling again. Monitor body condition closely through winter to make sure your feeding program is on target; the easiest time to put flesh back on a cow if she's pulled down after summer lactation is in the fall after weaning her calf — before weather gets cold. A pregnant dry cow should be able to gain weight on pasture alone, with just a protein supplement if the grass is overly mature with low protein content.

If a cow is thin at calving, it is very hard to pick up her weight after she starts lactating. She puts the extra energy into milk instead of body weight. A fat cow can coast through winter and even lose a little weight without detrimental effects, whereas a thin cow needs to gain weight through winter if you expect her to breed back. You don't want cows to be losing weight just before or after calving. Even if two cows have the same body condition at calving, if one is losing weight and the other is gaining, the cow gaining weight is better programmed for fertility than the cow losing weight. Studies have shown that each 10 percent of weight lost before calving can delay the first heat cycle by about 19 days. So you want your cows in good flesh at calving.

In some instances, however, too much nutrition can be as detrimental as too little. For instance, a cow or heifer that is too fat may also have fertility problems, or difficulty calving because she has too much fat in the pelvic area. Fat takes up some of the space and makes it harder for the calf to come through easily, and a fat cow or heifer will also tire more readily during labor—requiring assistance to deliver the calf in timely fashion.

Cows consuming really high levels of protein will also have problems, according to Ron Skinner, DVM (veterinarian and seedstock producer near Hall, Mont.). Beef cows do not need second and third cutting alfalfa hay, for instance, unless it's small amounts, used as a supplement to augment low-protein pastures or poor quality hay.

“High protein is an enemy, I've come to realize in the past 10 years. I do a lot of AI and embryo transplants and it's been interesting to watch what happens with the number of eggs you get, quality of the eggs, and fertilization of eggs, when cows are on different rations. This also plays a role in conception rates in AI programs,” he says.

Skinner consults with ranchers on nutrition and mineral programs, and also helps them resolve breeding issues. Some ask for help when they have low conception rates, such as 50 percent with embryos or only 60 percent with AI. “When we make changes in the rations, these rates improve,” he says.

“When I started doing embryo work in my own herd 30 years ago, I thought I could really help those cows by putting them on high quality alfalfa hay. I learned several things—first that they eat too much of it because it goes through them so fast and they really like it. One of the problems with feeding a high protein diet is that it builds up a too-high urea level in the uterine fluids, blood stream, and changes the pH, and this really hurts your conception rates,” says Skinner.

He learned to adjust the protein level in diet to a lower, more optimum level. “Now if we flush six cows we'll get 100 good eggs or more. The national average is seven eggs per cow on a flush. Our average is around 15 to 18 eggs per cow. Our AI conception rate is in the low 80's and we get well over 70 percent conception rate on embryos. We were not able to do that until the last few years, and it was partly because we changed our nutrition management on cows in the period we're giving shots, etc, three weeks before the flush. This taught me that some of the nutrition programs are off base and that all the alfalfa hay we were using in beef cattle now may be doing us more harm than good,” he says.

Stockmen in some regions have increased the production on their hay ground, going to sprinkler systems instead of flood irrigation, which enables them to grow (and keep) good stands of alfalfa. They can raise five to six tons per acre, where they used to raise two to three tons per acre. If a ranch grows a lot of good alfalfa hay the rancher is tempted to feed more alfalfa to the cows, but this can be detrimental.

Dairy quality alfalfa is usually cut before bloom stage, for maximum protein levels, but alfalfa for beef cows can be cut a little later -- to get more tonnage and slightly lower protein levels. One rule of thumb for alfalfa is to cut it when about 15 percent is blooming, to get good nutrient levels, but for beef cows you can cut it even later, as more of it is blooming, and still have plenty of protein. A mixed alfalfa grass hay is usually very adequate for beef cows, with more protein than they actually need, says Skinner.

One of the most important aspects of nutrition for beef cows is to make sure trace mineral levels are adequate, since many regions are short on crucial minerals like copper, zinc and selenium. It pays to check hay for mineral levels every few years, if it's hay from your own place. These may be low, or may be rendered unavailable to cattle if tied up by other minerals. “Three things that can tie up trace minerals are iron, sulfur and molybdenum. If you have excessive amounts of these, it will interfere with the body's absorption of trace minerals,” says Skinner. “This can cause weight loss, delay in puberty for heifers, and create health issues.”

Adequate levels of trace minerals in the diet of a beef cow are especially important in the 60 days before calving, and also after calving—through breeding. “Nearly 70 percent of the U.S. is copper deficient, and about 50 percent is zinc deficient,” says Skinner. Certain geographic areas are also very selenium deficient. You need to know what your soils and feeds contain, so you can make adjustments if needed.

“I don't think we should go overboard on trace minerals, but there are times in the beef cow's year that we really need them, such as in late gestation to help build a healthy immune system in the fetus,” he says.

Alfalfa Is Best As A Supplement -- Rich alfalfa hay can create health problems for young calves (including more scours and instances of enterotoxemia) if their mamas are milking too heavily during the first couple months of lactation. If calves are born early and cows are still being fed hay when the calf is young, good grass hay is much more healthy for the herd than alfalfa.

“We are now selling some of our 2nd cutting alfalfa and buying back grass hay for the cows. Our hay crop is 75 percent alfalfa, so we have a management problem. We bale at night and put it up with the leaves still on, so it's excellent quality (since 60 to 70 percent of the protein is in the leaves)—and too rich for beef cows. A diet of 11 to 12 percent protein for those cows is excellent, but 16 percent is too high,” says Skinner.

“Before calving, we run our cows on pasture and may keep them out there until it snows under. In these situations we supplement dry pasture with second cutting alflalfa. It works as well or better as a supplement than a lick tub, to give them the protein they need when forage levels are low. A little alfalfa every other day is very adequate to supplement these pastures, along with trace minerals. This way we can stockpile fall feed and use it to reduce the costs of feeding the cows. Alfalfa hay, used as a supplement, is the cheapest protein supplement you can buy, even when alfalfa hay is high priced. But you certainly don't want cows on a straight alfalfa hay,” says Skinner. One round bale of alfalfa, rolled out for 100 cows every other day, will do the job.







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