Pregnant cows need different protein levels at different stages of gestation. Nutrient requirements in early gestation are similar to maintenance requirements, but as the fetus grows, the cow’s nutrient needs increase. A lactating cow needs a much higher level of protein and energy than when she’s pregnant.  

Mary Drewnoski, beef systems specialist, University of Nebraska-Lincoln, says there’s also a fetal programming factor; the amount of protein a cow gets during gestation affects fetal development. “Research data suggests that for cows on dormant range pastures (mature grass) we’ll see negative effects on their progeny if they don’t receive adequate protein; it has long-term consequence on those calves,” she says. 

These cows need supplemental protein. “This could be about 2 pounds daily of distillers or cake, which is usually about 25 to 30 percent crude protein. We can also feed it every other day, doubling the amount. Research indicates this can be a viable option for protein but it doesn’t work so well for energy (cows need an adequate energy level daily in their diet).” 

Increasing the protein helps ruminants digest mature forage, but it doesn’t need to be daily. “They can recycle some of that nitrogen back to the rumen, but they need at least 7 percent crude protein in the diet. If forage is lower than that in protein, cattle start decreasing intake.” Digestion slows and they can’t eat enough to maintain themselves and they start losing weight. Pregnant cows need adequate protein so they can eat enough and have enough energy.  

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“What’s interesting is that we don’t see these same effects when grazing corn residue. Protein levels in those residues is below that 7 percent threshold yet cows maintain body condition, and we don’t see the fetal programming effects. My theory is that this is because digestibility of what they select when eating corn residue is higher, and they can continue eating an adequate amount. Corn husks can be up to 65 percent TDN.” The cows don’t decrease intake, since it’s so palatable and digestible. 

“As long as producers use recommended stocking rates, mature dry cows grazing cornstalks don’t need supplement. This doesn’t hold true for first-calf heifers, however. They are still growing and need higher protein level. On cornstalks they may need as much as 3.5 pounds per day of distillers to meet energy and protein requirements,” says Drewnoski. 

Jeremy Martin, PhD, ruminant nutritionist and reproduction manager, Great Plains Livestock Consulting says cows and heifers are very different in their needs. “Weather can be a significant factor, and was a major factor in most regions this past year, but stage of gestation and ability to consume feed is enough different that a heifer calf or pregnant heifer is a much different animal to feed than a mature cow.” 

Drewnoski says you can’t skimp on heifers; they may need to be fed separately. “Some people may not have enough room to do that, but could put them with their replacement heifers. This would be better than leaving them with the mature cows. The diet and amount of feed most people give replacement heifers would be closer to what those first-calf heifers need,” she says. 

“Here in Nebraska some people have replacement heifers on dormant range, with a fairly low rate of gain, and might only be feeding a couple pounds of distillers or cake. That’s appropriate for weaned heifers and a little light for pregnant first-calf heifers, but closer to what they need,” she says. 

BODY CONDITION 

“It’s important to provide protein to enable cattle to get full feed intake (and therefore adequate energy) but we also need to monitor body condition,” says Drewnoski. “If body condition is not maintaining, you may need to increase the protein, to increase feed intake. Body condition is a good gauge but some people don’t look at this until it’s too late and cows have already lost a lot of weight,” she says. It’s crucial to assess body condition at least three months before calving. That’s your last chance to do something to correct it because it’s hard to make a change after they calve. 

Weaning time is a good time to check body condition scores of cows, since as soon as lactation requirement is removed we can drop the protein requirements. “Those cows will be better able to regain lost body condition,” according to Janna Block, North Dakota State University livestock systems specialist.  

“We need to look at the thin cows or young cows because most people don’t think about using a supplement before winter. Many cows pick back up on green regrowth of cool season grasses and do well, but we need to pay attention to young cows and any cow that might be really thin. For those it might be worthwhile to separate them from the herd and feed them more, before they calve again. It’s cost-prohibitive and sometimes not possible from a physiological standpoint to try to get more condition on cows during late gestation or after they calve,” says Block. 

“Some producers get into calving and have a wreck because condition was not assessed earlier. The goal is to have mature cows calve in body condition score five, so we need to get them to that point prior to late gestation–then maintain body condition, rather than still trying to pick them up,” she says. 

SELECTING PROTEIN 

Jeremy Martin recommends pricing protein supplements on a cost-per-unit-of-crude-protein basis, always looking at this on a dry-matter basis, particularly with liquid supplements. “This is the best comparison. Alfalfa hay is usually competitive in price, if available. In some areas distillers products and soybean meal are feasible options. Some years, and this may be one, whole soybeans may be very competitive in price, on a cost per pound of crude protein basis,” he says. 

It often comes down to availability and freight costs, or ability to handle and feed a certain type of supplement. “Soybeans are cheap in central Nebraska but there are not many grown in western cow country. Depending of freight and whether or not you are set up to feed them, they may or may not work,” Martin says. 

When comparing/selecting a protein supplement, it should be at least 18 to 20 percent protein. “Below that, it’s hard for that product to compete as a protein supplement because it requires so much volume that it won’t be cost-effective,” he says. 

HOW MUCH? 

Janna Block, North Dakota State University Livestock Systems Specialist, says protein requirements vary based on body weight, age, environment, temperature, how far the cows have to walk to water, etc. “Most mature cows in mid-gestation will need about 1.5 pounds of protein per day. In late gestation they probably require closer to 2 pounds per day. When lactating, their requirements are even higher and will vary depending on the level of milk production,” she says.  

Cow size also makes a difference. “A 1300-pound cow in early lactation producing 10 pounds of milk requires a little over 2.25 pounds of protein and this would increase to almost 3 pounds if you add another 10 pounds of milk. She’d also need more energy.” The amount of milk produced makes a big difference; it takes a lot more protein and energy to feed a lactating dairy cow than to feed most beef cows, and some beef cows give more milk than others, and must be fed accordingly. 

“It’s challenging today to find beef cows with moderate milk EPD. The production target has been moved a lot, in the past 20 years,” says Block. Thus today’s beef cows require more energy and protein—and more total feed—than their counterparts a few decades ago, and unfortunately producers don’t always have the environment/feed resources to support that much milk; ranchers often have cows that are drawn down in body condition, trying to crank out a lot of milk on a diet that is insufficient. Most of these cows have trouble breeding back again on schedule.