Effects of high dietary crude protein on the characteristics of preovulatory follicles in dairy heifers

Ovarian activity and oocyte quality associated with the biochemical profile of serum and follicular fluid from Girolando dairy cows postpartum

This study was designed to evaluate the influence of heat stress (HS) on the metabolic profile of serum and follicular fluid (FF), ovarian follicle development, and oocyte quality of Girolando dairy cows. Oocytes, blood, and FF (follicles ≥9mm) samples were obtained at 30, 45, 60, 75, and 90 days postpartum in the summer and winter seasons. During transvaginal follicular aspiration, rectal temperature (RT), body condition score (BCS), number of ovarian follicles, and quality of oocytes were recorded. The ambient air temperature (AT) and relative humidity (RH) were also recorded to calculate the temperature humidity index (THI). Glucose, total cholesterol (TC), triglycerides (TG), urea, sodium (Na), potassium (K), and calcium (Ca) concentrations were determined using serum and FF samples. The RT, THI, and BCS loss were greater (P<0.01) in the summer; however, glucose, Na, and K serum concentrations decreased in the same season (P<0.05). Degenerated oocytes were positively associated (P<0.05) with THI (r=0.14) and AT (r=0.13), and negatively associated with glucose (r=-0.12) and K (r=-0.11) serum concentrations. HS induces metabolic changes, which compromise the number of ovarian follicles and the follicular environment, thus resulting in morphologically damaged oocytes.

Effect of prenatal programming on heifer development

In beef cattle, the main factors influencing nutrient partitioning between the dam and fetus include age of the dam, number of fetuses, production demand, and environmental stress. These factors play a critical role in programming the fetus for its future environment and available resources. Fetal programming reportedly affects neonatal mortality and morbidity, postnatal growth rate, body composition, health, and reproduction. Two main mechanisms responsible for fetal programming include DNA methylation and histone modifications. Alterations in the genome can be passed through multiple generations. Maternal environment (nutrition, age, physiologic status) can program progeny heifer growth and reproductive performance.

Epigenetics: Setting Up Lifetime Production of Beef Cows by Managing Nutrition

Longevity of cattle is correlated to reproductive success. Many studies in different species report the influence of maternal nutrition on progeny performance, health, and reproduction. Maternal nutrient status can cause epigenetic alterations to the genome of the developing fetus, which potentially can impact future generations. This review discusses fetal programming mechanisms as well as maternal nutrition’s impact on placental development and progeny heifer performance and reproduction owing to nutrient restriction, age, or production status. Furthermore, we discuss how early neonatal nutrient intake and type can influence future productivity in the beef and dairy cow. Understanding how these factors influence progeny performance will enable cattlemen to produce replacement females better adapted to their environment through maternal nutrient regulation by stimulating fetal programming.