Vascular Endothelial Growth Factor mRNA Isoforms 120 and 164 are Differentially Regulated Prior to Ovulation

Vascular Endothelial Growth Factor (VEGF) is produced by cells surrounding the egg in the follicle prior to ovulation. If VEGF is inhibited, ovulation does not occur. The VEGF gene can be spliced to produce different protein isoforms which have specific functions. Our objective was to determine if VEGF 120 and 164 mRNA isoforms are differentially regulated in the preovulatory follicle. From our studies, VEGF isoforms are differentially regulated during both CL regression and after a simulated LH surge. Differences observed in VEGF isoform regulation may allow for manipulation of ovulation in the beef cow

Vascular Endothelial Growth Factor mRNA Isoforms 120 and 164 are Differentially Regulated Prior to Ovulation

Vascular Endothelial Growth Factor (VEGF) is produced by cells surrounding the egg in the follicle prior to ovulation. If VEGF is inhibited, ovulation does not occur. The VEGF gene can be spliced to produce different protein isoforms which have specific functions. Our objective was to determine if VEGF 120 and 164 mRNA isoforms are differentially regulated in the preovulatory follicle. From our studies, VEGF isoforms are differentially regulated during both CL regression and after a simulated LH surge. Differences observed in VEGF isoform regulation may allow for manipulation of ovulation in the beef cow

Reproductive Aging Influences Ovarian Function in Beef Cows

Anti-Müllerian Hormone (AMH) has been associated with follicle number and age of the ovary. Therefore, our hypothesiswas that AMH was a biomarker for both follicle number and ovarian function in the beef cow. Ovaries were collected by flank laparotomy. The number of follicles increased as cows aged from 1.5 to 6 years and began to decrease thereafter; however, the size of the ovary continued to increase with advanced age. Expression of the AMH gene increased with increasing follicle number in 2-year-old beef cows. These results suggest that heifers with larger ovaries will have greater numbers of follicles and greater productivity, allowing them to stay in the production herd longer. AMH could be used to identify heifers of high reproductive potential at a very young age

Marine pelagic ecosystems: the West Antarctic Peninsula

The marine ecosystem of the West Antarctic Peninsula (WAP) extends from the Bellingshausen Sea to the northern tip of the peninsula and from the mostly glaciated coast across the continental shelf to the shelf break in the west. The glacially sculpted coastline along the peninsula is highly convoluted and characterized by deep embayments that are often interconnected by channels that facilitate transport of heat and nutrients into the shelf domain. The ecosystem is divided into three subregions, the continental slope, shelf and coastal regions, each with unique ocean dynamics, water mass and biological distributions. The WAP shelf lies within the Antarctic Sea Ice Zone (SIZ) and like other SIZs, the WAP system is very productive, supporting large stocks of marine mammals, birds and the Antarctic krill, Euphausia superba. Ecosystem dynamics is dominated by the seasonal and interannual variation in sea ice extent and retreat. The Antarctic Peninsula is one among the most rapidly warming regions on Earth, having experienced a 28C increase in the annual mean temperature and a 68C rise in the mean winter temperature since 1950. Delivery of heat from the Antarctic Circumpolar Current has increased significantly in the past decade, sufficient to drive to a 0.68C warming of the upper 300 m of shelf water. In the past 50 years and continuing in the twenty-first century, the warm, moist maritime climate of the northern WAP has been migrating south, displacing the once dominant cold, dry continental Antarctic climate and causing multi-level responses in the marine ecosystem. Ecosystem responses to the regional warming include increased heat transport, decreased sea ice extent and duration, local declines in icedependent Ade´lie penguins, increase in ice-tolerant gentoo and chinstrap penguins, alterations in phytoplankton and zooplankton community composition and changes in krill recruitment, abundance and availability to predators. The climate/ecological gradients extending along theWAPand the presence of monitoring systems, field stations and long-term research programmes make the region an invaluable observatory of climate change and marine ecosystem response

Vascular Endothelial Growth Factor Inhibitory Isoform Is Regulated Prior to Ovulation

VEGF normally acts to stimulate vascular development (angiogenesis) and is necessary for ovulation of the dominant follicle. The inhibitory isoform blocks the actions of VEGF angiogenic isoforms; therefore, the objectives of the experiments were to identify the bovine inhibitory isoform, VEGF164b and to determine its expression prior to and after the LH surge. VEGF164b mRNA was upregulated prior to but did not change after the LH surge. Therefore, VEGF164b may be necessary for preparation of the dominant follicle prior to ovulation

Utilization of Dried Distillers Grains for Developing Beef Heifers

A two-year study evaluated feeding dried distillers grains (DDG) during heifer development on growth and reproductive performance. Supplements provided similar CP, energy, lipid, and fatty acids. Protein degradability of the supplements differed such that undegradable intake protein exceeded requirements of DDG heifers. Heifer pubertal development, artificial insemination (AI) pregnancy rate, and overall pregnancy rate were not affected by supplement. However, AI conception rate and AI pregnancy rate were improved by feeding DDG in the heifer development diet

Nutritional Regime and Antral Follicle Count Impact Reproductive Characteristics in Heifers

Developing heifers were offered either a modified distillers (MOD), distillers based (DDG), or corn gluten feed based (CGF) supplement while grazing pastures during development. Prior to breeding, antral follicle count (AFC), uterine horn diameter (UHD), ovarian area, and reproductive tract score (RTS) were determined via rectal ultrasonography to examine the effect of protein supplement on heifer reproductive characteristics. Heifers developed on MOD diets had greater RTS, ovarian area, and total AFC compared to DDG and CGF heifers. Small and medium follicle counts had a positive correlation with total AFC. Heifers developed on DDG and CGF had greater overall pregnancy rates compared to MOD heifers. We also conclude that there is a positive relationship between AFC and small and medium follicle counts

Feeding Melengestrol Acetate to Bulls Prior to and at Puberty Alters Body Weight, and Hormone Concentration

Melengestrol acetate (MGA), which is commonly used in the beef industry to manipulate ovarian activity of females, was fed to bulls at two times during development, prepubertal (5.5 to 7.5 months) and peri-pubertal (6.5 to 9.5 months), to determine effects on testes size, scrotal circumference, body weight, and/or hormone production. We can conclude that feeding bulls MGA during the prepubertal and peri-pubertal time can alter body weight and testosterone production

Bull Exposure, When Combined With a Seven-day MGA Synchronization, Does Not Enhance Conception Rates in Cows

The purpose of the current experiments was to determine if cows exposed to sterile bulls (epididyectomized) in combination with a 7-day MGA treatment would have an advantage in conception rates to cows not exposed to bulls. Bull exposure increased percentage of cows cycling prior to synchronization and reduced the time from calving to initiation of cycling. Overall there was not an increase in conception rates to timed TAI or in total pregnancy rates in bull exposed MGA treated cows when compared to cows not exposed to bulls

Pre and Peri-pubertal Feeding of Melengesterol Acetate (MGA) Alters Testis Characteristics in Bulls

Bulls were fed 1 mg/head/day of MGA from 5.5 to 6.5 months ; 6.5 to 9; or fed a control diet. Body weight, scrotal circumference, combined testis weight, testis composition, and testosterone concentration were measured. Feeding MGA prior to puberty increased scrotal circumference and decreased testosterone concentration at 12 months compared to controls. Thus, feeding MGA prior to puberty can alter testis characteristics in bulls