Project : USDA ARS

ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Research Project #433077

Research Project: Improving Livestock Production by Developing Reproductive and Precision Management Technologies

Location: Livestock Bio-Systems

2021 Annual Report

Objectives
Objective 1: Apply developmental programming to improve production efficiency of beef cattle. Objective 2: Improve swine production by identifying factors contributing to prenatal piglet development and survival and postnatal preweaning mortality. Objective 3: Increase productivity and longevity of replacement gilts by identifying and defining physiological and environmental factors underlying developmental and reproductive processes. Objective 4: Enhance sow performance and retention within the breeding herd by identifying physiological and environmental features at critical periods throughout life that contribute to production and longevity. Objective 5 (new): Develop precision management technologies for livestock to automate measuring production traits.

Approach
Beef heifers that conceive early in their first breeding season have greater reproductive longevity and enhanced lifetime productivity. We reported that this is due, in part, to an increase in the number of antral follicles in their ovaries without any difference in Reproductive Tract Score or age at puberty. In the previous project period, we applied developmental programming (i.e., nutritional modifications at key stages of development) to heifers to increase the percentage that conceived early in their first breeding season and to increase the numbers of primordial follicles in their ovaries. The current project plan will determine if this resulted in increased reproductive longevity for these heifers and validate models that report the use of developmental programming to improve carcass characteristics in steer progeny (Objective 1). In Objective 2, we will investigate how nutrition and hormonal environment can impact the function of the genome during early embryonic development to better understand the factors contributing to fetal programming. In Objective 3, we will examine the maternal contributions to developmental programming by examining the influence of uterine function on conceptus development and the age of the dam on progeny performance. This research is critical to understand how early life events can impact adult traits and how we can harness developmental programming to improve the efficiency of beef production.

Progress Report
Calf performance measurements were collected for experiments in Objectives 1 and 3. Performance of heifers in Objective 1 was analyzed. Nutritional programming in the dry lot during the development phase improved ovarian function and reproductive longevity of these heifers compared to control heifers developed using standard methods. The final replicate of Objective 2C was cancelled because of Covid-19 and will be completed in fall 2021. The third replicate of data was collected for Objective 3A, examining the influence of size of the ovarian reserve on conceptus development. This places this experiment a year behind because the 2020 replicate was cancelled.

Accomplishments
1. Heifers developed on native range have better ovarian function than heifers developed in a dry lot. Nutritional status during the first year of life influences the development of the ovary in beef heifers. ARS researchers at Clay Center, Nebraska, developed feeding methods that increase the number of eggs in the ovary. Research with collaborators at New Mexico State University demonstrated that these benefits are 30% greater for heifers developed in a dry lot than for heifers developed on native range. This method increases reproductive longevity for heifers developed in a dry lot but may not be necessary for heifers raised on native range. Understanding the benefits of native range on ovarian development will help improve methods for developing fertile replacement heifers. Cow-calf producers can use nutritional programming to improve reproductive longevity in their herd, resulting in decreased cost of developing replacement heifers and increased profitability for the enterprise.

2. Estradiol improves nutrient transport to the developing conceptus. Estradiol is a hormone produced by the ovary during the reproductive cycle that is critical for proper uterine function and maintenance of pregnancy. ARS researchers at Clay Center, Nebraska, in collaboration with South Dakota State University investigated how estradiol influences uterine function during pregnancy in beef cows. Gene networks associated with nutrient transport were the primary targets for regulation by estradiol. Activation of these networks was associated with greater likelihood of maintaining pregnancy. Managing cows to ensure that they have initiated reproductive cycles prior to the breeding season will improve conception, leading to increased profit of $300 to $600 per pregnant cow for cow-calf producers.

3. Applying genomic markers to improve carcass traits does not negatively impact reproductive performance in replacement heifers. Selection for production traits in beef cattle can have unintended negative impact on reproductive function in the cow herd. ARS researchers at Clay Center, Nebraska, reported that genetic markers that associated with tenderness in beef steers also associated with a delayed calving date in heifers. To validate this detrimental effect on reproduction, ARS researchers at Clay Center, Nebraska, used data from steers to generate a breeding value for tenderness based on genetic markers. When used in heifers, the breeding value did not antagonize reproductive function. Cow-calf producers can apply these genetic markers to improve tenderness in steers without concern for unintended negative impact on reproductive function in replacement heifers.

U.S. DEPARTMENT OF AGRICULTURE

Livestock Bio-Systems: Clay Center, NE