AMH and Fertility, August 2017 - May 2019
Anti-Mullerian Hormone or AMH is produced by the granulosa cells of pre-antral or early follicles on the ovary in females. These follicles have already been recruited from the follicular pool to continue growth and become a viable follicle for ovulation. AMH is a dimeric glycoprotein member of the transforming growth factor β superfamily. The glycoprotein hormone enters the blood stream after being synthesized and secreted by the granulosal cells.
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It was originally discovered for its role in fetal sex differentiation, as it is also produced by the Sertoli cells in the testis of males. When an oocyte is fertilized with sperm carrying male DNA, the Y protein of the XY chromosomal pair has a region known as the Sex Determining Region on the Y chromosome (SRY). This region coordinates synthesis of SRY protein by the sex cords within the primitive gonad, which in turn drives development of testes. The Sertoli cells of the testes secrete AMH, which causes degeneration of the paramesonephric duct, also known as the Mullerian duct. Thus, this process is the manner by which Anti-Mullerian Hormone came to have this name.
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Prior to AMH sampling, it was previously established that the Antral Follicle Count (AFC) of a mature animal is directly and positively correlated with the superstimulatory response in cows. In addition, it has been determined that the number of follicles on the ovary 3 mm or greater in diameter is maintained during both the ovulatory and nonovulatory follicular waves of individual animals. Thus, ultrasound determination of AFC has widely been used to determine optimal animals for superstimulation, with the potential for a large number of ovulated follicles, as it can be done at any point of the animal’s estrous cycle with a great amount of accuracy and reliability. However, variations in ultrasound operators and operator-defined criteria for counting antral follicles has led the search for an equally reliable yet more user friendly means of determining candidates for superstimulation.
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We are exploring the use of AMH as a tool for predicting reproductive success of heifers and a tool for fetal sex determination in gestating animals. In addition, we are investigating the variation in AMH level over the lifetime of an animal, including how life events may impact AMH level.
Presence of Mastitis and Teat End Score, August 2015 - May 2016
To date, there has very little evidence to correlate a relationship between the presence of mastitis and the condition of the teat end. UGA College of Agricultural and Environmental Sciences funded a research proposal to study this relationship. We theorized that lactating dairy cows with a poor teat end condition (elevated teat end score) are more likely to have a mastitic infection present and are also more likely to have an elevated somatic cell count when compared to cows with good teat end condition (normal teat end score).
Teat ends were scored based on the degree of hyperkeratosis present. Hyperkeratosis is a thicening of the skin surrounding the teat orifice and inside the teat canal. Normal levels are to be expected from the pressure applied to the teat end during milking, however elevated levels are indicative of faulty milking equipment or a select other factors. This thickening of the skin and increased tissue presence has cracks and crevices that allow bacteria to fester adn is difficult to sanitize. In addition, this thickened skin in the teat canal prevents complete closure of the sphincter, which normally prevents bacterial entry. With the sphincter open, bacteria have direct access to the mammary gland.
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For this trial, 130 lactating dairy cows were sampled 1X a month for 5 months and their teat end was scored. In addition to a milk sample, a teat canal swab sample was collected to determine if bacteria can become trapped in the thickened skin of the teat canal, but not necessarily enter the mammary gland and cause a mastitic infection. Our results did not show a correlation between teat end score and presence of infection or somatic cell count. We did see a strong correlation between teat end score and age, indicating that teat end condition naturally deteriorates with age. In addition, we also saw a relationship between teat end score and the type of bacteria present. More aggressive bacterial mastitic agents were found in quarters that also had elevated teat end scores. For this trial, r-square values were lower than acceptable, indicating other factors that were at play that were not evaluated. Future research needs to be conducted to evaluate this data.
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Heifer Secretions and Mastitis Prevention, May 2015 - May 2016
For this project, udder secretion samples were collected from pregnant, late gestation heifers. The samples were plated and allowed to incubate to determine bacterial presence via presumptive identification. In addition, a Somatic Cell Count was run. Then, bacterial presence and elevated somatic cell count indicating a mastitic pathogen presence quarters were treated with 1 of 4 treatments which were randomly assigned. No treatment, antibiotic, teat seal, and antibiotic + teat seal. Results from the trial are still being collected and analyzed, however, a very high cure rate has been seen in quarters that had mastitis and were treated with the antibiotic, and the antibiotic + teat seal. In addition, quarters that were not treated at all calved in with mastitis, or did not become a functioning quarter. It was also determined that an elevated fly load on the farm negatively impacted the number of quarters on heifers that had a mastitic infection pre-calving. Flies were biting the teats of heifers and transferring bacteria from one teat to another.
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OmniGen, May 2015 - May 2016
Multiple research trials were run at the same time involving OmniGen-AF. OmniGen-AF is a powder that is produced by Phibro Animal Health and is mixed with the ration. It is designed to provide a boost in the immune system and ultimately result in fewer health events, a lower somatic cell count, and fewer cases of mastitis and metritis. Our research focused on its effects on mastitis and somatic cell count.
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For the portion of the trial I was involved with, 6-9 month old Holstein heifers were fed OmniGen daily for a period of 45-60 days. Blood samples were pulled and analyzed for immune function. After being bred and confirmed pregnant and before calving, milk secretions were collected for analysis as well as blood drawn. The milk secretions were plated and allowed to incubate to determine bacterial presence via presumptive identification. In addition, a Somatic Cell Count was run on the samples, API tests were conducted, gram-staining was performed when necessary, and differentials were run on all milk samples via microscope. Data for this trail is still ongoing and long term.
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MLV and Cyclicity in Heifers, Jan 2015 - May 2016
The purpose of this project was to determine the impact of a modified live respiratory vaccine on the reproductive parameters of virgin heifers. 24 Holstein heifers were synchronized for estrus using a 7-day CIDR protocol with 2 injections of PGF2, one at CIDR removal and one 16 hours later. All animals were calf-hood vaccinated with an available BRDC vaccine with a MLV IBR component. Heifers were observed for their 1st heat after synchronization, and at heat 2 after synchronization, half of the heifers were vaccinated with the same MLV IBR vaccine, and the other half were vaccinated with a killed IBR component.
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The IBR Modified Live vaccine has previously been known to cause reproductive issues in pregnant animals, but in 2004, a modified live IBR vaccine was approved for use in pregnant animals. However, the stipulation was added that the animals to be vaccinated with this must have seen the vaccine 60 days before being bred. The effects of this vaccine on cyclicity could impact the heifers' follicular pool and impact her ability to become pregnant when bred 60 days later.
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For this project, blood samples were pulled regularly to monitor progesterone, estrogen, and anti-mullerian hormone levels. In addition, animals were ultrasounded every other day to track ovarian structures. Finally, titers were collected both pre and post vaccination.
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Results showed that there was no difference in post-vaccination titers and the vaccination had no impact on progesterone concentration, luteal tissue area, peak estradiol production, or estrous cycle length. However, a reduction in AMH concentration was seen between cycle 1 and 2 and cycle 1 and 3, which could indicate a reduction of the follicular pool as a result of vaccination with an IBR MLV. There was no difference in post-vaccination titers, and vaccine type had no significant effect on any of the cell types or circulating lymphocytes.
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Further research is necessary to confirm results from this study, particularly because a small sample size was used for this project.
