Effect of Supplemental Nutrition on Embryo Survival and Pregnancy Rate in Beef Heifers

View the project final report

Commodities

• Animals: bovine

Practices

• Animal Production: livestock breeding

Reproductive efficiency is the most important factor contributing to the economics of the beef industry. Beef heifer development is a complicated and management intensive practice. Beef heifers in the north central United States are occasionally developed on native range. However, the range conditions in many areas do not permit heifers to reach 65% of mature body weight by breeding time. This may lead to reproductive failure caused by embryonic death and low pregnancy rates. Supplementation of cows with a source of protein and fat increased pregnancy rate by 80% over the unsupplemented controls. However, research in heifers is contradictory and inconclusive. It appears that supplementation of heifers is more beneficial in a nutritionally challenging situation, such as a range development system. Supplementation does increase cost of production in a low input range management system. However, supplementation with a co-product feed source such as dried distillers grain (DDG) is very attractive due to the low cost and ready supply. DDG is a by-product of the ethanol industry that is an excellent source of supplemental protein and an adequate supplier of dietary fat. Supplementation of beef heifers with DDG not only improves the sustainability of a range development system, but it also improves the sustainability of the ethanol industry by providing an outlet for the co-product. The long-term goal of this project is to interact with other practices to increase calves weaned per cow exposed. However, in the short term, we hope to prove the benefit of DDG supplementation on embryo survival to d 18 and subsequent 60 d pregnancy rates. This project will not only help improve economic survivability of livestock operation, but also improve the sustainability of a rangeland management system for developing beef heifers.

Reproductive efficiency is the most important factor contributing to the economics of the beef industry. The long-term goal of our research is to improve reproductive efficiency and calves weaned per cow exposed. However, the short-term outcomes of this project are very focused in scope and scale. The nutritional status of the dam immediately before and after breeding impacts embryonic survival and subsequent pregnancy rates. This project will reinforce the concept that elevated energy status is essential to reproductive success in developing heifers. Increasing the plane of nutrition immediately prior to and following breeding is beneficial and cost effective.

Intermediate outcomes for this project will potentially influence how producers manage heifers. While beef cows are traditionally managed in an extensive system, heifers require added inputs to ensure a productive lifespan. Separation of cows and heifers is necessary to allow economical supplementation. Whether it is range supplementation or dry lot feeding, the information gathered from this project may motivate ranchers to incorporative a more intensive feeding program for beef heifers. In addition to supplementation, we hope to demonstrate the advantage of increased energy two weeks prior to and two weeks following artificial insemination. The addition of a high-energy source of supplementation during this period, i.e. flushing, such as fat, may improve embryonic survivability and subsequent 60 d pregnancy rates.

While this project will have only direct short and intermediate outcomes, it will also contribute to long-term management changes in heifer development. Long term, these results may effect how females, potentially both beef and dairy, are managed prior to the breeding season. The periods immediately before and after breeding are novel in a heifer’s development and represents new nutritional demands. Moving livestock producers to a system that promotes a well-timed, cost effective supplementation program could improve pregnancy rate and economic success. While the results of this project may not effect revolutionary change, it could provide evidence to promote further study. Through further study and improved knowledge, heifer management on rangeland could be altered to improve reproductive efficiency. Furthermore, this short-term flushing system could be incorporated into any management system, not only rangeland systems, but also a more intensive, drylot management style.