Overview of the EAAP (ASAS Sponsored) Symposium focusing on the relationship between nutrition and reproduction in cattle

ASAS and EAAP are long term partners. In September of 2022, ASAS Sent 14 speakers to give presentations at the 2022 EAAP meeting.

Highlights from speakers and ASAS Sponsored symposia are as follows:

Globally, cattlemen face many challenges during a single year of production. However, 50 to 70% of input costs are associated with feed; therefore, strategic manipulating of nutrition can make operations more profitable. Knowing when to supplement and what form of supplement will work in a given operation at a given time is often clouded by what feedstuffs a producer has available. 

Insufficient intake of energy, protein, vitamins, and micro- and macrominerals have all been associated with suboptimal reproductive performance.  Therefore, the symposium addressed many of the inter-relationships between nutrition and reproduction. Key outcomes are summarized here:

• Strategic feeding to obtain ideal body condition scores can be achieved by understanding the production cycle of the cow. The period of greatest nutritional need is shortly after calving, but opportunities exist to have impacts during gestation that have positive impacts on fetal and subsequent calf performance, in addition to fertility. 
• Understanding the impacts of maternal environment on placental function and fetal development is a relevant consideration for cattle producers. Cattle raised for red meat production spend as much as 33% of their life being nourished by the placenta. Developmental programming through nutritional interventions can be adopted that more effectively improve subsequent performance of their calves.
• Post-weaning management of bulls is critical to attainment of puberty, but also has significant impact on semen quality, such as morphology and motility. In addition, post-weaning management likely impacts embryo developmental viability.  as long as bulls receive suitable minimum dietary requirements. Other factors may also play a role in semen quality, such as pH of the rumen, stress, and climate.
• Micro most likely to impact fertility in grazing herds are: copper (Cu), zinc (Zn), selenium (Se), manganese (Mn), and iron (Fe). Prior to simply supplementing a mineral it is important to determine what minerals may be deficient in the diet. Since the diet is the most significant contributor to the trace mineral nutrition of grazing beef cattle, it is important to consider a feed analysis to determine what mineral deficits may be present and how they may impact the performance of the cattle consuming them. 

Specific speakers and topic highlights below:

Rodolfo Cardoso: Approximately 5 million beef heifers enter the U.S. cow herd annually and their lifetime productivity is heavily dependent upon their ability to attain puberty and produce a calf by 24 mo of age. However, a significant proportion of heifers within existing U.S. production systems fail to achieve these goals, particularly in southern regions where Bos indicus-influenced cattle predominate. Our research in Bos indicus-influenced heifers demonstrate that Increased BW gain between 4 and 9 mo of age facilitates pubertal development by programming hypothalamic centers that regulate gonadotropin releasing-hormone (GnRH) secretion. Finally, our recent findings suggest that maternal nutrition during gestation can also induce neuroendocrine changes in the offspring that are likely to persist and influence reproductive performance throughout adulthood in cattle.

Reinaldo Cooke: Supplementing beef cows with Ca salts of soybean oil after artificial insemination favors incorporation of omega-6 fatty acids into maternal and embryonic tissues, which enhances interferon-tau synthesis by the conceptus and increases pregnancy rates in Bos indicus and B. taurus beef cows.

Philipe Moriel: Beef offspring growth, immune response, and reproduction can be optimized by altering maternal nutritional management during gestation, including supplementation of protein and energy, polyunsaturated fatty acids, trace minerals, frequency of supplementation, specific amino acids, and feed additives. Specific outcomes to on offspring performance remain variable and require further investigations. Nonetheless, fetal programming can potentially become a strategic tool to increase beef cattle production efficiency and beef quality.

George Perry: Impact of nutritional changes pre and post breeding on reproduction: Changes in nutritional intake can be the result of drought, changes in diet or movement to new locations. When nutrient intake was restricted (≤90% NEm) for 33-36 days before insemination, embryo development was stunted (P=0.05), fewer females exhibited estrus (P=0.02), and subsequent progesterone concentrations were decreased (P=0.02) compared to non-restricted (≥139% NEm) females. When nutrition intake was restricted post breeding (6 to 7 days), embryo stage (P<0.01), grade (P=0.02), total number of cells (P=0.03), and percentage of cells alive (P=0.01) were decreased compared to non-restricted females. Special considerations should be made prior to and during the breeding season to keep nutrient intake consistent and animals on a positive plane of nutrition.

Ky Pohler: Pregnancy loss in cattle causes both management and economic challenges to a producer. Recent studies have been conducted to quantify reproductive failures that occur during fertilization, early embryonic development, and late embryonic/early fetal development periods of gestation in beef cattle. Minimizing reproductive inefficiency, specifically embryonic mortality (EM) is vital. The focus of my talk was to highlight the maternal vs paternal contributions to pregnancy development and loss. Understanding and decreasing reproductive inefficiency in cattle is critical to develop sustainable production systems moving forward.

Joao Vendramini: Cattle adapted to tropical and subtropical regions likely have warm-season perennial grass as the predominant component of the diet. Temperature is the main factor dictating the presence of warm-season grasses in specific regions. Increasing global temperatures may favor the spreading of warm-season grasses throughout the world. A reliable, fast, and practical method to estimate digestibility and intake in different warm-season perennial grass species is still unknown. Grazing land management practices intended to mitigate GHG emissions, promote C sequestration, increase productivity and make systems more resilient to climate variation. There is a need to find alternative sources of N fertilization to promote production and persistence of grazing lands and decrease dependence on commercial fertilizer.