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Cow Nutrition
Nutrition Tips, Pre and Post-Calving, for Cows and Heifers
By: Heather Smith Thomas

Nutritional needs of cows vary considerably, depending on age (young and still growing, mature, or old with poor teeth), size, breed, whether or not the cow is lactating and/or pregnant, and 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. 

PRE-CALVING REQUIREMENTS - 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, fetal development, and optimal reproduction capabilities.  Different regions vary greatly in soil minerals; feeds in some areas may be deficient in certain elements.  It’s wise to take soil and feed samples to know how best to supplement 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 2 year olds.  If the heifer will mature at 1100 to 1200 pounds, she should weigh at least 715 to 780 pounds when bred and 935 to 1020 pounds when she calves.

            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 2 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.  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.

            More commonly, however, young cows are thin at calving rather than too fat.  For this reason, producers should feed 2 and 3 year olds different from the way they feed the main herd.  “You need to pay close attention to body condition score, especially in these young cows,” says Shannon Williams, Lemhi County Extension Agent (Idaho).  They should be separated from the herd and fed differently, preferably before they’ve lost too much weight.

            “If an older cow is losing weight, she should also be pulled out of the herd and fed separately.  Some producers put their old, thin cows with the young cows—whatever works for their own operation,” she says.  Protein requirements for pregnant cows increases during later stages of gestation, and is even higher for young cows.  If you keep young cows (coming first and second calvers) separate, they can be supplemented with protein, if necessary, without having to supplement the whole herd. 

            “According to U. of Idaho’s Cattle Producer’s Library, Cow-Calf Management Guide, in the Nutrition section, a mature 1100-pound cow needs 7.8 percent of the diet to be crude protein during the last trimester of pregnancy.  A 900-pound yearling heifer (coming 2 year old, approaching her first calving) in her last trimester would need 9 percent crude protein in her diet.  Another thing that is different between the heifer and the mature cow is metabolizable energy.  Also the net energy for maintenance is different,” says Williams.

In years past some producers lost calves to “weak calf syndrome” and University of Idaho studies eventually showed that the primary cause was shortage of protein in the diets of the cows, especially young cows.  Calves born from protein-deficient dams were more likely to suffer cold stress and/or succumb to calfhood illnesses.

            The mature cows can often be roughed through winter and early spring (as they approach calving) much easier than the younger cows, because they are not trying to grow.  “The percent TDN for a 900 pound heifer is 65.4 percent, as compared with 53.2 percent for an 1100 pound cow during her last trimester.  This is a major difference,” she explains.  Even though some of the nutrient requirements will be similar for any pregnant cows, their age and whether they are still growing or not will make for some differences.


IMPORTANCE OF TRACE MINERALS - 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, even if it’s hay from your own place.  Mineral levels 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.  Excessive amounts of these will interfere with the body’s absorption of trace minerals. 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 Dr. Ron Skinner (veterinarian and seedstock producer at Hall, Montana).  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, and after calving when the cow is preparing to rebreed,” he says.


POST-CALVING NUTRITION -  If a cow is lactating, she needs a much higher level of protein and energy than when she is pregnant.  According to Shannon Williams, the thing producers really need to remember is that during the 60 days following calving, they are asking the cow to produce milk, repair her uterus and breed back again.  “This requires an extreme amount of energy and nutrients,” she says. 

            If a cow is in poor body condition when she calves, she doesn’t have a very good chance to prepare for rebreeding while she’s producing milk for her new calf.  She may continue to lose weight, even if you increase her nutrient levels, and fail to cycle on time.  This is a crucial phase in her production cycle, and if she is a young cow (still growing), her needs for energy and protein will be even greater than that of an older cow.

“The important things are to feed cattle appropriately for their age and stage of gestation, and make sure they have good feed during not only the last trimester but also the first 60 days after they calve.  Their demands increase tremendously at that time.” 

Even if the cows came through pregnancy in good body condition, you don’t want them to lose ground after calving.  “They can always rob a little from their backfat if they were in good flesh at calving, but you may pay for this later if you don’t catch the weight loss soon enough,” says Williams.  Don’t just turn them out to grass and stop feeding them if the grass isn’t quite ready yet.  They may lose too much weight and not breed back quickly.


SIDEBAR: REPRODUCTION - Adequate levels of various nutrients are especially important for reproduction, since the body always takes care of 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 be cycling.  Ideal body condition score for best fertility is between 5 and 7 on a scale of 9.  Thin cows and obese cows can both have fertility problems.

Cows consuming really high levels of protein will also have problems, according to Ron Skinner, DVM (veterinarian and seedstock producer near Hall, Montana).  Beef cows do not need second and third cutting alfalfa hay, for instance, unless in 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.  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 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-some 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 conception rates,” says Skinner.

            He learned to adjust protein level in diet to a lower, more optimum level.  “Now if we flush 6 cows we’ll get 100 good eggs or more.  The national average is 7 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 nutrition management on cows in the period we’re giving shots, etc, 3 weeks before the flush.  This taught me that some of the nutrition programs are off base and that all the alfalfa hay we’re using in beef cattle may be doing us more harm than good,” he says. 


SIDEBAR: 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 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,” says Dr. Skinner.  “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,” he explains.

            “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 alfalfa.  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.

Stockmen in some regions have increased 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 5 to 6 tons per acre, where they used to raise 2 to 3 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.


SIDEBAR: TEST YOUR HAY - “The only way to really determine the nutrient quality (levels of various nutrients, including minerals) of your forage is to have it analyzed,” says Williams.  Even if it’s hay from the same field as last year, it may have had different growing conditions.  Variations in water, average temperatures, rate of growth, and stage of maturity when cut—along with conditions at harvest—can make huge differences in quality.  “If you cut it a week earlier or later in terms of bloom stage, for instance, the protein level may be different.  Doing a nutrient analysis may take a little time but you can then use your hay more efficiently and know when or if you need to add a supplement,” she explains.

            “This saves money in the long run because you know which hay is best quality, to feed your 2 and 3 year olds.  You can feed lower quality hay to the cows.  If you end up with more top-quality hay than you need, you can sell it and buy cheaper, lower quality hay for the main herd.  Or, you can use less expensive forage like straw for filler,” says Williams.   Your top quality hay can be used primarily as a supplement, for mature cows, to augment a lower quality diet of winter grazing, straw, or poor quality hay. 

Knowing the nutrient levels of your hay can save money on feed, or influence the future health of your calves, or weight and percent of your next calf crop.  “If you are not feeding the cows properly this spring, you next year’s calving season may be 90 days or longer (with some lightweight calves) instead of 45 to 60 days,” says Williams.  You may also end up with a higher number of open cows.

“Everything you do during winter/spring this year will affect what happens the next year.  It boils down to long-term planning,” she says.

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