Victor Enrique Gomez Leon

My Research aims are to: (1) develop/test applied strategies to enhance health, production, and reproduction; and (2) elucidate mechanisms controlling reproduction. Examples include:

Strategies to simplify and improve dairy heifer fertility:

Heifer fertility is gaining attention, and our research has the potential to have a national impact as Kansas raises heifers for other major dairy states (WI, MI, NY, etc.). Currently, heifer fertility can be predicted by genomics or parents’ average information. We aimed to associate heifer fertility (n = ~700) with phenotypic traits that are repeatable and easy to measure in the field with minimal cost. Body condition score at breeding had the strongest association with fertility among all traits we measured and evaluated.

We have also demonstrated that estrus expression is associated with greater fertility in timed embryo transfer programs (n = 700 embryo transfers). This led us to test the idea of whether administering exogenous GnRH has any benefits in heifers bred to estrus. Some herds have adopted this strategy without proper testing. Using ~6,000 breedings, we demonstrated that GnRH on estrus-bred heifers does not increase pregnancies, even with sexed semen or repeat-breeders. Avoiding this unnecessary GnRH could save >$100,000/year in large operations. In an ongoing trial with Dr. Paul Fricke (UW-Madison), we are aiming to simplify a synchronization protocol and save $10 per heifer by reducing the use of an intravaginal progesterone device.

Using recombinant bovine somatotropin in heifers (n = ~2,000), we (1) increased pregnancies per embryo transfer by ~20%, and (2) reduced pregnancy losses by ~50%. This could yield ~1,000 extra pregnancies if 300 embryos/week are transferred, as in the herd used in our study.

Improve and scale reproductive strategies on large dairy enterprises:

As dairy herds continue to consolidate and dairy cows increase in Kansas, the use of technology needs to be considered to address the challenges of managing reproduction in large dairy enterprises. Nonetheless, such technologies need to be tested at a smaller scale first, involving very intense evaluations (i.e., blood samples every 15 minutes, ultrasound every 12 hours, etc.). At the KSU Dairy Teaching and Research Center (DTRC), we validated a needle-free system for administering reproductive hormones, demonstrating effective luteolysis in cows. This can increase compliance and decrease needle-related injuries and disease transmission. In an ongoing study at the DTRC, we are validating an inline milk-sensing device for real-time measurements of milk components (fat, protein, somatic cell, and urea) and reproductive-related hormones (progesterone and pregnancy-associated glycoproteins). If validated, this technology would enable 24/7 monitoring of milk components, estrus, and pregnancy status, with transformative potential for the dairy industry. On a larger scale, we are preparing to start testing the Simple-Synch protocol in one of the largest herds in Kansas. The Simple Synch is a simplified version of an estrous synchronization that prioritizes estrus-breedings. Conducting applied research in commercial herds ensures rapid adoption of results by producers and allows students to interact with industry stakeholders.

Physiologic mechanisms controlling reproduction: Dominant follicle selection, pregnancy development, and estrous cycle:

I have conducted multiple studies to assess how hormones alter follicle dynamics and selection. To expand on that work, we performed RNA sequencing of granulosa cells to elucidate the pathways, initial stages, and triggers of dominant follicle selection. In a separate study, we demonstrated that omega-3 fatty acids have the potential to increase milk yield and quality, as well as enhance pregnancy-related physiological conditions. We are also testing the theory that prolonged estrous cycles in nonpregnant cows are associated with altered hormone and uterine receptor profiles due to high milk yield. These studies complement our applied research and have implications for human reproduction.