Dr. Richard A. Mackey

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Nutrition is a major factor affecting cow reproductive efficiency. Long-term moderate or chronic dietary restriction results in a gradual reduction in dominant follicle (DF) growth rate, maximum diameter and persistence. Animals become anoestrus when they lose on average 22-24% of their initial body weight. There is evidence of significant animal-to-animal(More)
High reproductive efficiency in the dairy cow requires a disease-free transition period, high submission rates to AI and high pregnancy rates per service. A key risk factor that causes increased incidence of metabolic disease is low negative energy balance (NEB) in the periparturient and early postpartum periods. Low NEB decreases LH pulse frequency, growth(More)
A comprehensive database was established on the milk production and reproductive performance of dairy cows in 19 selected herds in Northern Ireland, varying in size, management system and genetic merit. Data were obtained for 2471 cows, 1775 of which calved in a second year, and 693 were culled from the herd for specific reasons. The estimated mean rate of(More)
Relationships between genetic merit for milk production and animal parameters and various parameters of reproductive performance were examined using multilevel binary response analysis in a study of 19 dairy herds for three successive years, representing approximately 2500 cows per year. The proportion of cows intended for rebreeding that were back in-calf(More)
The effects of acute nutritional restriction on follicular dynamics, incidence of anovulation, and periovulatory estradiol and gonadotropin concentrations were studied in two replicates using beef heifers exhibiting regular estrous cycles. Heifers fed a diet supplying 1.2 maintenance (1.2 Mn) were synchronized using an intravaginal progesterone-releasing(More)
The effects of acute nutritional change on endocrine and ovarian characteristics were studied in cyclic (intact; n = 20) and long-term ovariectomized (ovx; n = 18) heifers being fed 1.2 x maintenance (1.2M). On d 7 of an 8-d progesterone and estradiol treatment, intact and ovx heifers were randomly allocated to diets providing .4, 1.2, or 2.0M until(More)
This report is based on a demonstration project in which outpatient psychiatric and counseling agencies available to residents of Prince George's County, Maryland, were surveyed by mail questionnaire every 3 months over a 15-month period. The purpose of the project was to review current services available in each agency. All agencies offering their services(More)
The effects of calf isolation and restricted suckling on LH pulse characteristics and interval to first ovulation (postpartum interval) were studied in 52 multiparous beef cows, with or without exogenous progesterone. At 30 d postpartum, cows were randomly allocated to one of four treatments (n = 13/treatment): 1) Ad lib, ad libitum access of cows to(More)
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