Aliakbar Ahmadzadeh

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The effects of energy balance on hormonal secretion patterns and the structure of recovered oocytes were evaluated in 20 lactating Holstein cows during two trial periods. Cows were randomly assigned to one of two dietary treatments formulated so that dry matter consumption was 3.6% of body weight (high energy; 1.78 Mcal/kg) or 3.2% of body weight (low(More)
The objective of this study was to evaluate the effect of clinical mastitis and (or) other diseases on reproductive performance in lactating Holstein cows. Cows (n=967) from a commercial dairy farm were divided into four groups retrospectively: cows with clinical mastitis and other diseases (MD, n=54), clinical mastitis only (M, n=154), other diseases only(More)
The role of dopamine in regulating glucocorticoid and prolactin secretion was investigated in lactating Holstein cows by characterizing serum cortisol and prolactin responses to fluphenazine, a dopamine receptor antagonist. Twelve anovulatory cows received an intravenous bolus injection of either saline (n = 6) or 0.3 mg of fluphenazine/kg of body weight (n(More)
The objectives of this study were to determine 1) the effect of simultaneous thawing of multiple 0.5-mL straws of semen and sequence of insemination (first, second, third, or fourth) on conception rates in dairy cattle, 2) whether the conception rates achieved following AI by professional AI (PAI) technicians and herdsman-inseminators (HI) differed, and 3)(More)
Two experiments were conducted to determine the effect of estradiol cypionate (ECP), when incorporated into a conventional GnRH-PGF(2alpha)-GnRH timed artificial insemination protocol (Ovsynch), on systemic estradiol (E(2)), time and incidence of ovulation, luteal development, and conception rate in Holstein cows. Our objective was to determine if(More)
The objectives of this study were to determine the effect of administration of exogenous GnRH 5days after artificial insemination (AI) on ovarian structures, serum progesterone concentration, and conception rates in lactating dairy cows. In experiment 1, 23 Holstein cows were synchronized using the Ovsynch protocol. Five days after AI (day 0) cows were(More)
Endocrine changes and recovered oocytes were evaluated during 16 wk of ultrasound-guided transvaginal follicular aspiration (TVFA) and prior to and following administration of GnRH at the cessation of aspiration. Nonlactating previously aspirated (PAC, n = 4) and non-aspirated, (AC, n = 4) Holstein cows were subjected to 16 wk of twice-weekly aspiration.(More)
The objectives were to evaluate the effect of synchronization protocols on follicular development and estradiol 17-beta (E(2)) and progesterone (P(4)) concentrations in dairy heifers. In experiment 1, 36 heifers were assigned to 1 of 6 synchronization protocols in a 3 x 2 factorial design: presynchronization with GnRH on study d -6 or -9 [study d 0 =(More)
The objective of this study was to describe early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry. Cows (n=50) were continuously monitored for behavioral estrus with a radiotelemetric system, HeatWatch II (CowChips LLC, Manalapan, NJ), from d 14 to approximately d 49 postpartum. Blood collection for analysis of(More)
This experiment was conducted to investigate the effect of naloxone (NAL), an opioid receptor antagonist, on pituitary LH secretion in anovulatory Holstein cows during the early postpartum period when cows were expected to be in negative net energy balance. Twenty-three cows (11 primiparous) received either saline (n = 12) or 1 mg/kg BW NAL i.v. (n = 11) on(More)