Nutrient requirements in early gestation aren’t much greater than maintenance requirements (unless the cow is lactating), but as the fetus grows, the cow’s nutrient needs increase. Dr. Travis Mulliniks (beef cattle nutritionist, range production systems specialist, University of Nebraska – Lincoln) says there’s been a lot of research on supplementation in late gestation, and during lactation, and it mainly boils down to environment.
“In some environments forage quality is high enough to meet those requirements, whereas semiarid and arid environments may only have quality forages for three months of the year.” This makes a difference in how we manage cows, what type of cows we have and what our calving season might be.
“Understanding nutrient requirements and timing of forage quality in your production system is important – fine-tuning a good nutritional plan throughout gestation. Research starting in the 1960s focused on providing adequate nutrients for pregnant cows, making sure they had enough body condition to make it through [the] stress of winter,” he says.
Then people started thinking about the calves cows were carrying and not just the cows. In Idaho, there was research in the 1970s on weak calf syndrome due to low protein levels in cows’ winter diets. “And now we talk about fetal programming, and maybe put too much emphasis on that idea,” says Mulliniks.
“When you look at the data, and [a] large number of production studies, there’s not much difference in calf performance hinging on maternal nutrition. But we do see what happens with extreme weather events. We had a ‘bomb cyclone’ [a rapidly intensifying storm associated with a sudden significant drop in atmospheric pressure] two years ago in the spring; weather was extremely cold and extremely wet. This can have a big negative impact on the fetus, and on baby calves,” he says.
“From a nutritional standpoint, providing correct nutrients to the fetus is like an insurance policy against poor growth, poor health response or deficiencies.” Also, make sure you’re setting up the cow to deal with calving and to recover quickly enough to get pregnant in a timely manner, and do it in a cost-effective way.
You don’t want to overfeed and have cows too fat, since that can have a negative effect. Cows in body condition score 6 or 7 usually will lose weight after they calve; they often have the lowest pregnancy rates next breeding season. “Nutrient requirements for a cow in body score 7 are much higher than a cow in body condition score 5,” Mullinicks explains. A cow losing weight after calving is less apt to cycle and breed back than if she’s holding her own or slightly gaining.
“Monitor your cows; know their body condition and where you are headed. Know your forage and feed quality and how much time you have left between now and when a big increase in requirement will occur, with lactation. Allow enough room to not get too far behind that you can’t afford to catch up – when requirements are high and you don’t have quality feeds,” he says.
Check body condition and consider weaning early if necessary, so cows can start regaining condition before a bad winter. “If you always wean on a certain date, you might not be able to afford to put enough energy into thin cows to get them caught up before calving,” he explains.
Feed tests
“Producers can run into wrecks thinking their forage is higher quality than it is; their cows are slowly slipping and becoming thinner,” says Mullinicks.
Janna Block, a livestock systems specialist at the Hettinger Research Extension Center, North Dakota State University, says that in drought years, feed testing and nutrient analysis becomes even more important.
“Make sure you know exactly what you’ve got, in terms of nutrient quality, and carefully monitor body condition. Also, check their manure. If it’s firm and dry, they aren’t getting enough protein. They could utilize dry forage better if they had a protein supplement,” she says.
Small grains like sorghum-sudan, canola and other alternative forages might help fill the gap, but many of these are nitrate accumulators, especially in drought. Always check nitrate levels as well as nutrients before feeding these to pregnant cows. “Abortion is a common consequence of nitrate toxicity; it shuts off oxygen supply to the developing fetus,” says Block.
“Evaluate forage and feed resources and make a plan, especially for young cows that are still growing; it’s harder to meet their needs for growth and lactation. They don’t have as much rumen capacity as mature cows and need higher-quality feed. This is why it’s important to do feed tests and get a nutrient analysis – and make a plan for different age groups,” says Block.
A cow in midgestation needs feed that’s at least 50% total digestible nutrients (TDN) and a minimum of 7% crude protein (CP). A cow in late gestation needs 54% to 55% TDN and 8% to 9% protein. After she calves and is lactating, she needs about 58% to 59% TDN and 9% or 10% protein. “But we don’t feed percentages, we feed pounds. Always figure that out. It’s also good to have a mineral analysis when checking forage quality,” she says.
“If you have your forages analyzed, you’ll know where you might be short, and can save your best feed for late pregnancy/lactation and feed lower-quality forages to dry cows in earlier gestation on a maintenance ration,” she says.
Importance of protein
Dr. Jim Sprinkle, extension beef specialist at the University of Idaho Nancy M. Cummings Research and Education Center, says forage quality in the fall may be lower this year in many regions, and there may be less quantity.
“Without protein supplement on dormant pastures, you can expect mature cows to lose about 0.9 pounds per day, and about twice that much loss with younger cows. Crude protein in forage sampled is often below the cow’s requirements,” Sprinkle says.
“Cows can select around that, if they have adequate pasture and keep rotating to new pastures,” he explains. “They seek out high-quality plants and eat those first. If they have to stay in that pasture very long, however, the best feed is soon gone,” he says.
“We did a research trial with late season grazing and four different treatments. One group of cows stayed in the same pasture the entire period [45 days] without any protein supplement. Another group stayed in a different pasture but were provided protein. Two groups got to rotate at least once during that time period – and one group got supplement and the other did not,” Sprinkle says.
The cows that stayed the whole time in the same pasture with no supplement lost a little weight, and all the other groups gained weight. “The cows that did not get any supplement but were rotated to new pasture partway through the 45 days gained a little weight, but not quite as much as the supplemented groups.” There was enough protein in some of the plants in the new pasture that they were able to select an adequate diet.
“Going to new pasture is like going to the salad bar at a restaurant,” says Sprinkle. When you first get there – and you are the first ones there – selection is good, but once it’s picked over, the selection is not as good.
It pays to provide a supplement or let cows go to new pasture often enough to find what they need. “Otherwise, you’re trying to put weight back on those cows later – when weather is colder, they are in a later stage of pregnancy and requirements are higher – and it’s more expensive to do it. It costs about three times as much to put weight back on than to keep it on and prevent weight loss,” he explains.
Cows in the last trimester that are on hay stubble regrowth or fed relatively good-quality hay for a month or so will generally gain about half a pound per day. They can make up some of the weight lost while lactating. “But if they drop one or two body condition scores, it’s more difficult. You must add 10 to 20 percent grain/concentrate to the ration. It’s more efficient to provide protein supplement on dormant-season grazing and try to prevent the weight loss.”
