Space and exercise could be almost as important as food and water for the successful development of beef heifers reared in dry pens, and quantifying this importance is the goal of a study planned by a researcher in the Department. of Animal Sciences from Texas A&M University of the College of Agriculture Life Sciences.
The reproductive development of replacement heifers dictates the overall efficiency of cow-calf operations. In order to maximize efficiency and minimize the use of resources, replacement heifers in the beef industry are increasingly housed in dry pens. Although the practice is less common in Texas than in other parts of the country, land use trends suggest it may become more prevalent, said Reinaldo Cooke, Ph.D., associate professor of production. of Texas A&M Beef Cattle.
“As an example, Houston, Navasota, and College Station will soon become a large metropolitan area,” Cooke said. “We are going to have fewer grass resources for livestock, competing with urban development and agricultural production. I don’t think the whole industry will move to contained operations, but we need to find management systems to make sure we maintain or promote production efficiency and promote animal welfare.
That is why, he said, management and stocking density guidelines for heifers raised in dry areas are urgently needed. Optimal nutritional programs have been developed and disseminated, but not those for aspects of heifer welfare, including stocking density. These stocking density guidelines exist for poultry, pigs and dairy cows, but there is a dearth of information regarding stocking density for beef cattle, Cooke said.
He will address this critical need with a team from the Texas A&M Department of Animal Science comprised of animal welfare specialist Courtney Daigle, Ph.D., and reproductive physiologists Ky Pohler, Ph.D., Rodolfo Cardoso, Ph.D., and Cliff Lamb. , Ph.D., who is also director of the department.
The team received a $ 500,000 grant from the U.S. Department of Agriculture, USDA, National Institute of Food and Agriculture to examine stocking density and determine whether management of stocking density can prevent the development of reproductive pathways necessary for the heifer to reach puberty.
In typical American spring calving herds, replacement heifers are weaned in the fall and exposed to their first breeding season the following spring at around 15 months of age. In late fall and winter, heifers are often moved to dry land systems to ensure adequate feed for growth, paying special attention to their nutritional regimen.
“Also, it’s becoming more and more common in the western United States, especially where cows and calves graze on public land, in October to wean the calves and bring them to a dry yard system. to feed for the winter. Even on farms with normal grazing, when winters are severe, heifers are moved to dry land to facilitate management and feeding. It usually begins during a critical period of growth around seven to nine months. “
Cooke said his research group is the first to investigate and describe the potential drawbacks that result from this management program to heifer welfare and reproductive development.
Current storage and spacing recommendations relate primarily to feedlot cattle and are not adaptable to cow-calf systems, he said. With more and more farms opting to raise heifers in dry areas to meet environmental challenges and limited resources, producers need specific guidelines regarding stocking density.
Cooke said his previous studies found that butcher’s heifers moved to dry pens had lower reproductive efficiency than expected.
“Whenever we have heifers locked in a confined environment, their reproductive efficiency is lower than that of open pasture heifers which have poorer quality feed,” he said. “Dry heifers gained more weight with better feed, but no reproductive efficiency. “
Cooke said that by reviewing the literature to understand what was going on, he found that no one had studied the reproductive differences between pasture-fed and dry-raised heifers.
“This prompted us to launch this project to find out why puberty is blocked. “
Theory: Heifers need room to move
Cooke said heifers in arid parks don’t have a lot of opportunity to exercise, which is important for their hormonal well-being. Thus, the design of their study will help determine whether providing voluntary exercise areas and more resting space mitigates the negative effects of dry land housing.
“We know that exercise zones are often set up in confined dairy farms to allow cows to exercise voluntarily, with positive results for their well-being and productivity,” he said. declared. “So we believe that providing heifers with the opportunity to exercise will mitigate the detrimental effects of high stocking density on their well-being and reproductive responses. “
In addition, the Texas A&M team will compare different stocking densities or sizes of dry land. Their theory: The increased dimensions of dry land can accommodate larger groups, which also promotes physical activity and alleviates social stressors.
“We will have 30 minutes of exercise per day and heifers that do not exercise to determine if their reproductive inefficiency is due to being confined or lack of exercise. Our second and third goals will look at stocking densities – how many animals in the pens. “
The only density guidelines they can use come from feedlots, but even those date back to the 1980s, Cooke said. The Federation of Animal Science Societies recommends about 15 square meters per heifer in dry, unpaved terrain.
“We’re going to start with the minimum space they suggest and work to see when we reach the same level of reproduction as the grazing heifers,” he said.
Stocking density is a management decision that significantly affects livestock, Cooke said. The results of this study will help develop guidelines to promote the welfare and productivity of beef heifers reared in dry pen systems.