Does heifer size really matter?

Some recent research conducted at the University of Nebraska – Lincoln shows that when managed correctly, larger heifers can be more profitable than smaller heifers.
UNL ag economist Matt Stockton tells producers that larger heifers require more days of age and higher levels of nutrition to develop so they can maximize profitability. “Specific combinations of heifer age and potential size change the nutritional regimes needed to optimize heifer profitability,” he explains. “However, the potential for loss is greater for large heifers that are not fed enough, compared to small heifers fed too much.”
Ideally, Stockton says producers should work toward developing a homogeneous group of heifers that can be managed all the same to maximize profitability. “Ideally, if they are all diverse, they will all need to be managed differently because each one has a different response to the same management inputs,” he emphasizes.
The cattle market shows bias toward bigger animals, whether it is culls or breeding cattle, or even feeder cattle. Most animal scientists will say a small cow is more efficient, but Stockton questions how efficiency relates to profitability. “It can sometimes, but that isn’t an assumption you should automatically make,” he tells producers. “Don’t ever assume efficiency is equal to profitability.”
The economist also questions how producers can determine when the optimal time is to breed a heifer. “We have been told over and over again that a heifer should be bred when she reaches 65 percent of her mature bodyweight,” he says. “How do you know what that is when you can’t observe her as a mature cow?”

Estimating maturity

Most producers use the herd average as a basis of determining bodyweight, but Stockton says that is really just an educated guess. “What happens if that heifer is from a smaller dam? We might have underestimated her maturity. If she comes from a large dam, we may have overestimated her maturity,” he states.
Birthweight is also an important consideration. If you have a cow that gives birth to a 120-pound calf and another cow that gives birth to a 70-pound calf, when both of these heifers reach a breedable age, the 120-pound heifer will actually be less mature than the 70-pound heifer at the same breeding weight, he explains. The 120-pound heifer will actually need to be heavier to breed. “Birthweight is important because it is a great predictor of the actual size of the animal,” he notes.
Armed with the right information, Stockton says producers should be able to look at two heifers in a pasture that are the same size and forecast how mature they are. Maturity can also influence the probability of pregnancy, he notes. If a heifer is from a bigger cow and weighs 600 to 700 pounds, she is considered 55 percent of her mature size. “Her probability of becoming pregnant is only 79 percent, compared to a heifer out of a smaller cow who may be at 90 percent,” he explains.
Dystocia is also a concern. “As maturity goes down, dystocia goes up,” Stockton states. “Many producers focus on getting the heifer bred the first time, but dystocia is a major factor in second pregnancies. It can cause up to a 20 percent reduction in second pregnancies.”
Nutrition also plays a role in mature size. Stockton studied cows at the Gudmundsen Sandhills Laboratory in Whitman, Nebraska, and found that older calves from smaller dams didn’t need as much nutrition as their younger counterparts. “If they were overfed, the probability of pregnancy and profitability goes down,” he says. “The smaller, mature heifers don’t need as much nutrition. They could be roughed out and still make money,” he notes. “The younger, larger heifers receiving a lower level of nutrition during this study were not deemed profitable. However, the ones that were fed the proper plane of nutrition made the producer the most money,” he says.
The point of this study, Stockton says, is to show that all cattle are not created equal, and size does make a difference. “If I had 20,000 head, I would use a maturity index, sort the cattle and manage them differently to be more profitable,” he says. “If I was a smaller operator, I would be looking for ways to individually manage my cattle that wouldn’t cost me anything. That technology may not be available yet, but it does exist,” he states.
Stockton questions whether the beef industry is ready to move toward utilizing precision agriculture. “With precision agriculture, the field is managed in pieces, not as a whole,” he says. “The question is, can we do that in the cattle business?”  
Gayle Smith is a freelance writer from Potter, Nebraska.
PHOTO: Most animal scientists will say a small cow is more efficient, but Stockton questions how efficiency relates to profitability. Staff photo.




Fuente: http://www.progressivecattle.com/topics/reproduction/7559-does-heifer-size-really-matter

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