Good management of heifers, especially during winter, can make a big difference in their success as cows. Dr. Bart Lardner, research scientist with the Western Beef Development Centre (WBDC) and adjunct professor in the department of animal and poultry science at the University of Saskatchewan says the traditional recommendation, for the past 40 years, has been to let heifers reach 65 per cent of their eventual mature body weight before breeding them.
This is why ranchers may confine heifers after weaning and push them to gain more than they would on winter pastures. Some ranchers keep more heifers than they need and then make selections the following spring regarding which ones to breed. Other ranchers raise heifers on pasture or range (feeding hay and supplement) and don’t confine them, feeling that those heifers stay fitter and healthier and make better cows, even though they don’t grow as fast as intensively fed heifers. The genetics of many cow herds have changed; some stockmen have selected for more efficient animals that can do well without grain, needing less expensive inputs for growth and production.
“The increase in cost of fossil fuel and feedstuffs, and capital investment, makes us look at rate and pattern of gain when developing heifers,” says Lardner. Today we have cattle that can do well without being pushed so much. There has been a lot of research in this area, since the concern has been that puberty would be delayed if heifers were raised with a lower rate of gain and lower per cent of mature body rate at breeding. Some of the earlier work was all about insuring that they would reach puberty and breed on time, but there has also been some work to see if there was an alternative, such as developing them to less than 65 per cent mature body rate. Studies were done looking at developing heifers to 60 per cent or maybe even just 55 per cent of mature weight as the lower end.”
“Success with this is all about genetics. British breeds might be better fit for this lower per cent than some of the continental breeds. We’ve looked at the possibility that there might not be a negative effect on reproductive efficiency — not just as a first-calver but also for the life span of that cow in the herd,” he says.
Some ranchers have developed cattle that fit their ranch environment and can thrive on the grazing resources the ranch provides, without expensive inputs during the development period, the 200 days from October-November until breeding in June or whenever breeding starts.
“Recent work at the research centre at Miles City, Montana, has evaluated developing heifers to lower weights, studying reproduction impacts and economics. Dr. Rick Funston at North Platte, Nebraska, has also evaluated heifers developed grazing winter range or residues. We put together a development program here in Saskatchewan, looking at two rates of gain for developing heifers — moderate versus high, and an extensive grazing program versus a drylot feeding program. We called these groups moderate gain in extensive grazing, high gain in extensive grazing, moderate gain in drylot and high-gain drylot,” he says.
“We wanted to expose replacement heifers to a system they would be managed in for longevity — in an extensive system where they have to go find the feed versus having it brought to them in a bunk or pen. They have to go out and graze, winter well, and then cycle during breeding season and give the producer a calf,” he says. Most ranchers want heifers that can utilize crop residues, stockpiled winter range, standing corn, or whatever the ranch can grow cheaply for winter feed.
“So we looked at the two systems and moderate versus high rate of gain and followed them through to their third calf. This gives us a better idea about whether the development system impacts reproductive longevity of the heifer. Most of the research programs simply followed heifers up to their first pregnancy diagnosis but not beyond. We followed them farther, to see their retention rates within the herd. Whatever system we develop heifers in should be for longevity and not just making sure the heifers can breed as yearlings,” he says.
“During the development program that first winter, before breeding, we had some heifers on a typical high-roughage diet — a grass/legume hay — and bale grazing. Being grown in a winter environment they needed a little extra energy, but the largest part of their diet was good-quality hay, with a little cereal grain for supplement. The moderate-gain group gained about 1.2 pounds per day. The high-gain group averaged a little over 1.5 pounds per day. At weaning, they were all about 565 pounds. The heifers with moderate gains came out at about 780, and the high-gain group weighed about 870 just before breeding,” says Lardner.
“If you go for the lower per cent of mature body weight, such as 55 versus 65 per cent, make sure the breeding pasture has good-quality forage. We saw that those few lighter-weight heifers that had not yet reached puberty coming out of winter did reach puberty during breeding season, started cycling, and did become pregnant. So if pasture quality is adequate, they do catch up,” he says.
He recommends weighing cattle to know the actual average mature body weight. Don’t guess. Know if your mature cows, five years old and above, average 1,200 pounds, 1,400 pounds, or whatever. If you use a targeted rate of gain for heifers, you need to know the mature weight.
“In that first year, with moderate-gain heifers we saw compensatory gain during breeding season. Those heifers only gained about 1.2 pounds during winter but gained about two pounds a day during breeding season and caught up. By contrast the high-gain group had static growth at about 1.5 pounds during breeding season.” They had already put on the weight they needed.
“There was no difference in first pregnancy rate; both groups ended up with similar rates of 85 to 90 per cent pregnancy rate. Then we followed them through the next couple years. The heifers with moderate gains caught up with the others by second calving and were similar as mature cows. We looked at three years of retention in the herd, comparing how they were developed. The heifers from each of the four systems were all similar; each group had about 77 per cent retention in the herd, based on normal culling practices.” Thus the moderate-gain heifers were just as able to stay in the herd as the ones with higher gain during development.
Input costs keep going up, in terms of infrastructure, fuel, feed, etc. “The difference between our groups of extensive moderate gains and drylot high-gains group was about $60 per head development costs for the first 200 days after weaning. You don’t want to cut development costs too much, if it will be detrimental and have a negative effect on the heifers,” he says.
You want to optimize a development program, without having to spend more than you need to. “A program shooting for 55 per cent mature weight won’t work everywhere. You might want to aim for 60 per cent of mature weight to fit your environment and winter. Some areas are tougher in winter, and some areas the summers are tougher; forage nutrition is more challenging during summer.” In some situations you might need to have heifers coming out of winter with a little more growth.
The second winter, when heifers are pregnant, it is important they be in adequate body condition before calving. “The six weeks prior to calving, make sure to meet their protein and energy requirements. We wintered bred heifers on a swath graze program and knew the quality of the annual cereal hay they were grazing. This extensive grazing system was cost-saving, but six weeks before they started calving we checked feed quality and gave them a little supplement in the form of a range pellet — just to make sure they were in good body condition. We didn’t want them to drop below optimum condition.”
On the other hand it is also important to not overfeed heifers as they approach calving. You don’t want them to get too fat or put too much into fetal growth at that time or there may be calving problems. “You simply give them every chance to calve with the least difficulty and hopefully come back and rebreed,” Lardner explains.
“Continue to pay attention through their second year regarding the way they are fed, to get them rebred for their second calving. That’s the next big challenge. Some operations have a lot of focus on that first breeding season but then just put the first calf heifers in with the older cows. They tend not to rebreed because they can’t compete with older cows for feed,” says Lardner.
They are still growing, so they should be kept separate from the older cows in winter so they have adequate feed for growth and can rebreed.