By Jessica L. Sperber
Heifers that are not retained as replacement females for breeding often find their home in the feedlot, with heifers comprising approximately 37% of total cattle on feed in the US during a normal cattle cycle. The US is currently experiencing a tightening beef cow herd due to the ongoing drought conditions experienced by many of the cow/calf producing states. Not only has the US culled nearly 10% of the cow herd since 2020, but replacement heifer retention is low, with an elevated number of heifers making their way into the feedlot, representing nearly 40% of cattle on feed (USDA National Agricultural Statistics Service). With greater heifer placement in the feedlot, managing feedlot heifers to ensure their health, well-being, and optimal growth is key for feedlot sector profitability.
There are many factors to consider when feeding heifers, including nutrition, animal health, pregnancy management, and growth enhancing technology use. Providing a balanced and nutritionally complete diet that meets the nutrient requirements of growing and finishing heifers is key for optimizing growth and performance. Monitoring feed intake and adjusting the ration based on heifer weight and frame may improve feed efficiency and increase rate of gain. There is no indication that heifers respond to varying feedstuffs (grains, roughages, or byproducts) different than steers, however, it is well established that heifers gain less and are less efficient than steers. Like managing steers, including appropriate pen space (this varies based on geographical location), bunk space (9” to 12”), and providing access to clean water is critical when managing heifers in a feedlot.
Pregnancy prevention and/or management is the most critical difference when comparing management of heifers vs. steers in the feedlot. It is estimated that 2 to 15% of intact heifers that enter the feedlot are pregnant. There are always increased costs associated with heifers that enter the feedlot pregnant, regardless of pregnancy management method. To properly manage pregnancy in a feedlot, pregnant heifers should be identified upon arrival. At the time of receiving or initial processing, heifers should be pregnancy tested via rectal palpation, ultrasound, or blood test. If the pregnancy check is positive, producers have the option to remove the pregnant heifer from the feeding group or consult with their veterinarian regarding abortifacients. Selection of an abortifacient should be determined by the stage of pregnancy of the heifer. The most common abortifacient utilized in the US for pregnant heifers is an injection of prostaglandin, commonly Lutalyse (Zoetis) or Estrumate (Merck Animal Health), which may be used in combination with dexamethasone depending on stage of pregnancy. For feedlot producers that choose an abortifacient as their pregnancy management method, it is recommended to monitor the health and behaviour of heifers for up to 1 week post abortifacient administration. It is important to keep in mind that both the drug protocols used and the stress of delivering the fetus are immunosuppressive, therefore, it is common to modify bovine respiratory disease (BRD) prevention and monitoring protocols for heifers during this period as they are at increased risk of respiratory outbreak. One final consideration is to be aware that protocols for pregnancy termination are not always 100% successful. Depending on the management and resources of the individual yard, evaluation of the termination success rate in groups with high pregnancy rates may be advantageous to ensure that there are no surprises later on in the feeding period.
If a pregnancy is unknown or the producer chooses to retain a pregnant heifer in the feedlot, an outlined standard operating procedure (SOP) should be in place for the possibility of calving in a feedlot. This SOP should include guidelines on sanitation, dystocia support, calf health and well-being, and heifer management post-calving, keeping in mind that dystocia support and neonatal calf management can be two of the greatest challenges for ensuring animal welfare in yards that feed a large population of heifers.
Although some feedlot producers may choose to retain a confirmed pregnant heifer through the feeding period and market her prior to expected parturition, this management method is not economical when compared to feeding a non-pregnant heifer. Although the live body weight of a full-term pregnant heifer will be heavier than a non-pregnant heifer, this difference in live body weight is due to the fetus, enlarged uterine, and excess fluid from pregnancy. On a carcass-adjusted basis, heifers that are pregnant at slaughter have reduced average daily gain (when adjusted for pregnancy weight), worse feed conversion, and lower dressed yield compared to non-pregnant heifers. In general, the further along in gestation that a heifer is at the time of harvest, the lower the carcass dressed yield will be. If a feedlot regularly markets pregnant heifers to the packing plant, this may result in a lower price at the time of sale or potential marketing challenges for the yard further down the road.
Aside from pregnancy testing upon feedlot arrival, feedlots have the option to purchase spayed heifers or hire veterinary assistance to complete the spay procedure at the time of heifer processing. Spaying is a surgical procedure which involves removal of the ovaries, rendering a heifer sterile, for prevention of pregnancy. Removing the ovaries eliminates the hormonal fluctuations associated with the estrus cycle, which can impact heifer behavior. Even when purchasing spayed heifers, feedlot operators are encouraged to pregnancy test new arrivals, as the spay procedure may have failed, and heifers could be pregnant. Although dated, research shows that when comparing non-implanted spayed heifers to non-implanted intact heifers, spayed heifers gained less. However, when implants were administered to spayed heifers compared to intact heifers, spayed heifers had a significant improvement in rate of gain over intact heifers.
The separation of sexes in the feedlot pen or avoiding “mixed pen” feeding is one of the best ways to avoid unplanned breeding in the feedlot. There is always the possibility that a steer retained a testicle during the castration process, so if choosing to feed in mixed pens, performing a testicle check during receiving is highly recommended. When separating sexes into separate pens, the feedlot has the option to include a Type A Medicated Article known as Melengestrol Acetate or “MGA” in the diet. For heifers fed in confinement for slaughter, MGA is utilized to suppress estrus, preventing pregnancy, and subsequently increasing rate of gain and improving feed conversion. Estrus suppression also reduces behaviors associated with estrus, including mounting, riding, and standing heat behavior, all of which can be an energy loss for the animal. Unnecessary mounting can result in severe bruising, which may result in a carcass-weight loss for cattle sold on a carcass basis due to excess trim at the packer.
The use of growth enhancing technologies, such as implants and beta-agonists, are labeled for use in both steers and heifers fed in confinement for slaughter. Growth promoting implants have the greatest return-on-investment of any animal health-related technology utilized in the feedlot sector. To achieve the full weight gain advantage from implant administration, a proper plain of nutrition must be offered to the cattle. Feedlot producers should work closely with their veterinarian and nutritionist and follow recommended guidelines for growth enhancing technology use. In general, steers exhibit a greater gain response to growth enhancing technologies than heifers. This difference in response is largely due to the naturally circulating level of estrogen in intact heifers, which may increase impetus for fat deposition. Since steers typically have a greater potential for lean muscle mass compared to heifers, and implants stimulate the deposition of lean muscle tissue, steers respond more robustly to implants than heifers due to their inherent muscle development capacity. That being said, there are still additional pounds to be gained by utilizing growth promoting implants in feedlot heifers, and the profitability of these technologies should not be overlooked.
One advantage of finishing heifers is their ability to deposit intramuscular fat, known as marbling. Estrogen and progesterone play a major role in the synthesis and deposition of lipids, which cause heifers to have a natural impetus for the deposition of fat. This can become a challenge when feeding heifers for extended days on feed, as excessive fat deposition can cause heifers to qualify for USDA Yield Grade (YG) 4 and 5 discounts. However, feedlot producers may have an opportunity to gain a premium for USDA Quality Grade (marbling score) when feeding heifers and selling on the grid, pending that YG 4s and 5s can be managed and their discount does not outweigh the marbling premium. When it comes to optimal management of heifers in the feedlot, nutritional status, heifer health, pregnancy management, and growth technology use are all key considerations, and when managed correctly, can be profitable for a feedlot operation.
Source : unl.edu