Space and movement can be critical to the reproduction of dry beef heifers
July 21, 2021
Space and movement could be almost as important as food and water to the successful development of cattle heifers raised in dry plots, and quantifying that importance is the goal of a planned study by a researcher at the College of Animal Science at Texas A&M University of Agriculture and Life Sciences, writes Kay Ledbetter.
The reproductive development of surrogate heifers determines the overall efficiency of the cow-calf farm. To maximize efficiency and minimize resource consumption, heifers for the beef industry are increasingly being kept in dryer sections. Although the practice is less common in Texas than other areas of the country, land use trends suggest it could be more common, said Reinaldo Cooke, Ph.D., professor of beef cattle production at Texas A&M.
“Houston, Navasota and College Station, for example, are about to become one major metropolitan area,” Cooke said. “We will have fewer grass resources for cattle and we will compete with urban development and crop production. I don’t think the entire industry will switch to limited operations, but we need to find management systems to ensure that we maintain or promote production efficiency and promote animal welfare. “
For this reason, guidelines for the management and stocking density of heifers raised in dry sections are urgently required. Optimal feeding programs have been developed and disseminated, but not those for heifer welfare aspects, including stocking density. These stocking density guidelines exist for poultry, pigs and dairy cows, but there is a lack of information on 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 consisting 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 a professor.
The team received a $ 500,000 grant from the U.S. Department of Agriculture, USDA, National Institute of Food and Agriculture to study stocking density and determine whether stocking density management can prevent the development of the reproductive pathways that the heifer needs to reach Puberty needed.
Search for answers
In typical US spring calf herds, surrogate heifers are weaned in the fall and given their first breeding season in the following spring at around 15 months of age. In late fall and winter, heifers are often placed in drylot systems to ensure adequate feeding for growth, with special care being taken with their feeding regime.
“It is also becoming more common in the western United States for cows and calves to graze on public land in October, to wean the calves in October and put them in a drywall system for the winter. Even on farms with normal grazing, when the winters are severe, the heifers are moved to drying areas for easier management and feeding. This usually starts during a critical growth phase of around 7-9 months. “
Cooke said his research group was the first to examine and map out the potential adversities arising from this management scheme for heifers’ welfare and reproductive development.
The current stocking and spacing recommendations relate primarily to beef cattle and are not applicable to cow-calf systems, he said. As more and more farms choose to raise heifers in dry plots to meet environmental challenges and limited resources, producers need specific guidelines on stocking density.
Cooke said his previous studies showed that heifers moved to dry plots had lower reproductive efficiency than expected.
“Any time we have heifers in an enclosed environment, their reproductive efficiency is less than that of open pasture heifers who were poorly fed,” he said. “The drylot heifers gained more weight with better feed, but not with reproductive efficiency.”
Cooke said while looking through the literature to understand what was going on, he found that no one had studied the reproductive differences between the heifers raised in pasture and dry stall.
Theory: Heifers need freedom of movement
Cooke said heifers don’t get much exercise in dry houses, which is important for their hormonal well-being. So, your study design will help determine whether providing areas for volunteer exercise and more space to lounge around will mitigate the negative effects of drywall.
“We know that exercise areas are often set up on closed dairy farms to allow the cows to move around voluntarily, which has a positive impact on their wellbeing and productivity,” he said. “We therefore believe that the adverse effects of high densities on their welfare and reproductive responses are mitigated by allowing heifers to move around.”
In addition, the Texas A&M team compares different stocking densities or Drylot dimensions. Her theory: Larger drylot dimensions accommodate larger group sizes, which also encourages physical activity and alleviates social stressors.
“We’re going to exercise for 30 minutes a day and not exercise heifers to see if their reproductive inefficiency is a fact of being restricted, or lack of exercise. Our second and third goals will deal with the stocking density – how many animals are in the bays. “
The only density guidelines they can use are from feedlots, but even those are from the 1980s, Cooke said. The Federation of Animal Science Societies recommends around 15 square meters per heifer in unpaved dry plots.
“We’ll start with the minimum room they suggest and work our way up to see when we get to the same level of reproduction as the heifers in the pasture,” he said.
Stocking density is a management decision that has a significant impact on livestock, Cooke said. The results of this study will help develop guidelines to promote the welfare and productivity of cattle heifers reared in drylot systems.
“That’s what led us to do this project to find out why puberty is blocked.”