How low to go when selecting bulls for birth weight
As producers select their bull battery for the upcoming breeding season, one question that may come to mind is how low is too low when selecting bulls for birth weight. There isn’t a rancher out there who wants to pull a calf, but is there a point when selecting a bull with too low of a birth weight is going too extreme?
The short answer is there is no perfect answer. Producers have to consider their own management goals, the environment and cow size, among other things. “I see cow size continuing to increase as an industry,” said Jerry Connealy of Connealy Angus. “In the Angus industry, and particularly in our own business, we are struggling to hold cow size, and even decrease it from what it was in the 80s, when we were selecting those taller frame bulls.”
As an industry, cow size may continue to increase unless there is a joint effort to select replacement heifers that aren’t on top or even at the higher middle end for size. “We need to select the smaller heifers,” Connealy said. “The problem is, it is easy to say, but when you are standing out there selecting your replacements, it is very hard to do.”
University of Nebraska Lincoln Extension beef genetics specialist Matt Spangler, pointed out conversations he has had with ranchers looking to decrease the size of their cows. “A lot of the time, I talk to the rancher who wants to moderate his cowherd, and I walk him through what he needs to buy for a bull,” Spangler said. “Then, at load out, I see him loading up the highest growth, heaviest muscled bull on the sale. The problem is in part what these guys put on offer, but it is also having the discipline to go to the sale and say ‘I may buy the bull that is below the breed average for milk, or above the breed average for birth weight, because I plan to use him for my cows’.”
“In the end, the key is having the discipline to buy what you truly need,” he said. “That is what will have the most tremendous impact on where we go from here with cow size.”
Birth weight and yearling weight are highly correlated traits. “When generations upon generations spread bulls with heavy birth weight or light birth weight stacked upon each other, we have defeated those antagonisms. That correlation is still real, and it’s still there. In the Angus breed, we have conquered a lot of that,” Connealy said.
“In this industry, we are guilty of being plungers. We can’t moderate,” he continued. “We think if a lighter calf is good, then an even lighter one is better. We have to stop somewhere. I think we are pushing that more than we need to. A cow can have a calf that weights 85-90 pounds, and we can still use the natural correlation between birth weight and yearling weight to our advantage. Heifer bulls need to be used as heifer bulls, even if we don’t like to pull calves.”
Connealy said he wouldn’t recommend to anyone stacking light birth weight on top of light birth weight, or piling negative upon negative. “You will eventually get a finer boned, frailer calf that will be a less rugged animal in the end,” he said.
Too light a calf can also have more health issues. “There is certainly some buzz out there that short gestation calves have less developed lungs, causing us to see more sickness and other negative ramifications,” Connealy said.
Loren Berger of Berger’s Herdmasters suggests producers should select bulls for birth weight, based on what the end point is for their cattle. “I visited several feedlots who wanted to feed my cattle, and they all told me they want to take the Continental cross cattle to 1,450 to 1,500 pounds. Most 65 pound birth weight calves will struggle to get to that, and still have an acceptable yield grade,” he said.
Berger encouraged producers who are concerned about birth weight to make some adjustments in their herd. “I think those producers need to separate the cows from the heifers. A cow can give birth to a heavier calf, have the calf get up and nurse right away, and do all this in a harsh environment,” he said. “If these cows are limited to giving birth to a 65 pound calf, in my mind, that calf is a loss. I think 85-90 pounds may be more ideal, in most situations. I feel most producers are making a big sacrifice if they take low birth weight to the extreme in the mature cows.” ❖
— Clark is a freelance livestock journalist from western Nebraska. She can be reached by email at firstname.lastname@example.org.