WBIA Current News
Does your new herd bull have enough help lined up?
Let's start with the premise that a producer has a herd of 35 cows. His old bull handles the breeding quite well by himself, but he's been around long enough that it's time to replace him. The producer goes out and buys a yearling bull to fill the vacancy. This producer knows the bull to cow ratio for young bulls in a sixty-day breeding season is generally one cow per month of bull age measured at the time of turnout. If the new bull is sixteen months old at turnout, he should be expected to successfully breed about sixteen cows. So, the producer decides to lower the bull to cow ratio by utilizing a round of artificial insemination. Better yet, with all of the timed AI protocols available today, he won't have to spend hours heat detecting. He's expecting 50 percent conception from AI, leaving about 18 cows for the yearling to pick up. At the end of the season, the cow herd is still showing heats, cows are open, and he doesn't think the yearling bull is even heat detecting. What went wrong?
On its face the math here seems correct. The bull in this example should be capable of managing the task. But if we chart his workload, the problem quickly becomes clear. In the system the old bull worked in, the cows calved over the course of sixty days. After a period of anestrus and recovery, they would be expected to begin cycling in roughly the same order they calved, with the first calvers cycling earliest, the later calvers later in the season. Even if the old bull serviced thirty percent of the cows twice, it's entirely possible that he serviced cows fewer than 50 times in the sixty-day season, or less than one per day. It's quite likely there were some days when he serviced more than one cow, but equally likely he had some days with no cows in heat and rested.
In the situation described here, our young bull doesn't stand a chance. Timed AI protocols are designed to speed the return to estrus in post partum cows, the goal being getting semen into every cycling cow. Beyond that, the goal is to have every cow in heat simultaneously to maximize efficiency of labor. But let's not forget the bull. Now instead of easing into the breeding season, he's dumped into a herd of mid-cycle cows. And no matter how often our producer checks on him, he's never seen following cows. Well, at least for the first ten days. With a normal estrus cycle being 17 to 24 days, we are about to have an event. If the target of 50 percent conception was hit, eighteen cows should be returning to heat in roughly a seven day period, with the majority of them hitting on or near day 21. On average, 2.5 cows per day for a week. More likely, one or two cows early, four or five daily for two or three days, and one or two daily to round out the week. The vision conjured up is similar to a young terrier at the bottom of a corncrib: so many rats, so little time, and no idea where to start. Add some weather stress, fertility and libido decreases in both the cows and bull. If AI conception was 40 percent, or maybe 30 percent, our problem is magnified. The young bull stands in the shade for 17 days without appearing to heat detect, then the scenario repeats. He may service some cows, he may even settle some. But our thumb rule of sixteen cows per bull has been shot through the head. The young bull is overworked and over whelmed and is likely to give up or suffer an injury. Mr. Producer buys a second bull, but next years calves are late, and the young bull becomes the goat.
A classic case of unintended consequences. It was reasonable to reduce the bull to cow ratio, but the method used did not consider the intensified workload for the bull. Take some time to discuss your plans with other producers, your seed stock supplier and other professionals.
One hundred and twenty bulls have completed 35 days on test at the 55th annual Wisconsin Beef Improvement bull test. They are averaging 4.41 pounds of daily gain with an average weight per day of age at 3.28 pounds. A complete report is on the web at www.wisconsinbeef.com. Printed reports available on request at 800-297-5747. Sale is April 7, 2012, at the UW-Platteville Pioneer Farm.
PO Box 955 | New Glarus, WI 53574 | 1-800-297-5747 | wbia@utelco.tds.net