Effect of copulation on estrus duration, LH response, and ovulation in Boer goats.

The objectives of this investigation were to determine the effect of copulation on estrus duration, LH response and ovulation in Boer goats. A controlled randomized study, with two replicates, in which does were divided at each replicate in treatment (COP; n = 12) and control (CON; n = 12) groups was performed. All the does were pluriparous and estrus synchronized with CIDR (progesterone 300 mg) maintained in the vagina for seven days, and received 50 μg of GnRH at device insertion and 5 mg of natural prostaglandin F-2 im at CIDR removal.

Pubertal Escape From Estradiol Negative Feedback in Ewe Lambs Is Not Accounted for by Decreased ESR1 mRNA or Protein in Kisspeptin Neurons.

In this study, we investigated whether decreased sensitivity to estradiol negative feedback is associated with reduced estrogen receptor α (ESR1) expression in kisspeptin neurons as ewe lambs approach puberty. Lambs were ovariectomized and received no implant (OVX) or an implant containing estradiol (OVX+E). In the middle arcuate nucleus (mARC), ESR1 messenger RNA (mRNA) was greater in OVX than OVX+E lambs but did not differ elsewhere.

Nutritional programming of accelerated puberty in heifers: alterations in DNA methylation in the arcuate nucleus.

High rates of body weight gain during the juvenile period appear to program molecular events within the hypothalamus, leading to advancement of puberty. Methylation of DNA, an epigenetic mechanism that controls gene expression, is associated with metabolic programming events and is proposed to play a role in the pubertal process. In this study, DNA methylation was assessed in genomic DNA obtained from the arcuate nucleus (ARC) of juvenile heifers fed to gain body weight at low (0.

Onset of luteolytic action of exogenous prostaglandinF-2α during estrous cycle in goats.

The objectives of these two experiments were to determine the day of onset of luteolysis after exogenous PGF-2α administration during the estrous cycle and the fertility of this synchronized estrus in goats. In the first experiment, during the breeding season, 48 Nubian does were estrous synchronized, using intravaginal sponges impregnated with a progestin, and estrus was detected by vasectomized bucks. The does were divided at random into three groups of 16 does each to be treated at days 2, 3, and 4 of the estrous cycle (estrus = day 0).

κ-Opioid Receptor Is Colocalized in GnRH and KNDy Cells in the Female Ovine and Rat Brain.

Kisspeptin-neurokinin B-dynorphin (KNDy) cells of the hypothalamus are a key component in the neuroendocrine regulation of GnRH secretion. Evidence in sheep and other species suggests that dynorphin released by KNDy cells inhibits pulsatile GnRH secretion by acting upon κ-opioid receptors (KOR). However, the precise anatomical location and neurochemical phenotype of KOR-expressing cells in sheep remain unknown.

Continuous presence of male on estrus onset, estrus duration, and ovulation in estrus-synchronized Boer goats.

The objectives of the present study were to assess the effect of permanent contact of teasers without copulation on the interval from controlled internal drug release (CIDR) removal to estrus onset, estrus duration, ovulation time, number of ovulations, and interval from CIDR removal to ovulation time on estrus-synchronized Boer goats. During the fall season, a controlled randomized design experiment with two groups, control (CON; n = 18) and treatment (TRE; n = 18), was performed. The TRE group was maintained permanently in a pen with an aproned buck immediately after CIDR removal.

Effect of copulation on estrus duration and ovulation time in goats.

The objective of the present study was to evaluate the effect of copulation on estrus duration and ovulation in goats. During the fall season, 14 multiparous Boer does were estrous synchronized with controlled internal drug release (300 mg), maintained in the vagina for 7 days, and received 50 μg of intramuscular GnRH device insertion and 5 mg of natural intramuscular PGF2α at device removal. The does were randomly divided into two equal groups: a treatment group (TRE; n = 7) and a control group (CON; n = 7).

Elevated body weight gain during the juvenile period alters neuropeptide Y-gonadotropin-releasing hormone circuitry in prepubertal heifers.

Increased body weight (BW) gain during the juvenile period leads to early maturation of the reproductive neuroendocrine system. We investigated whether a nutritional regimen that advances the onset of puberty leads to alterations in the hypothalamic neuropeptide Y (NPY) circuitry that are permissive for enhanced gonadotropin-releasing hormone (GnRH) secretion. It was hypothesized that NPY mRNA and NPY projections to GnRH and kisspeptin neurons are reduced in heifers that gain BW at an accelerated rate, compared with a lower one, during the juvenile period.

Reciprocal changes in leptin and NPY during nutritional acceleration of puberty in heifers.

Feeding a high-concentrate diet to heifers during the juvenile period, resulting in increased body weight (BW) gain and adiposity, leads to early-onset puberty. In this study, we tested the hypothesis that the increase in GnRH/LH release during nutritional acceleration of puberty is accompanied by reciprocal changes in circulating leptin and central release of neuropeptide Y (NPY). The heifers were weaned at 3.

Hypothalamic distribution, adenohypophyseal receptor expression, and ligand functionality of RFamide-related peptide 3 in the mare during the breeding and nonbreeding seasons.

RFamide-related peptide 3 (RFRP3), the mammalian homologue of avian gonadotropin-inhibitory hormone, has been shown to negatively regulate the secretion of LH and may contribute to reproductive seasonality in some species. Herein, we examined the presence and potential role of the RFRP3-signaling system in regulating LH secretion in the mare during the breeding and nonbreeding seasons. Hypothalamic NPVF mRNA (the precursor mRNA for RFRP3) was detected at the level of the dorsomedial nucleus and paraventricular nucleus, but expression did not change with season.

Neuroendocrine pathways mediating nutritional acceleration of puberty: insights from ruminant models.

The pubertal process is characterized by an activation of physiological events within the hypothalamic-adenohypophyseal-gonadal axis which culminate in reproductive competence. Excessive weight gain and adiposity during the juvenile period is associated with accelerated onset of puberty in females. The mechanisms and pathways by which excess energy balance advances puberty are unclear, but appear to involve an early escape from estradiol negative feedback and early initiation of high-frequency episodic gonadotropin-releasing hormone (GnRH) secretion.

Reduced progesterone concentration during growth of the first follicular wave affects embryo quality but has no effect on embryo survival post transfer in lactating dairy cows.

Fertility of lactating dairy cows is associated with reduced progesterone (P(4)) concentration compared with nonlactating animals. The objective of the current study was to determine whether P(4) during growth of the first follicular wave (FFW) affects embryo quality. Lactating Holstein cows at 33±3 days post partum were allocated to one of three treatments.

Dynorphin immunoreactive fibers contact GnRH neurons in the human hypothalamus.

Dynorphin, an endogenous opioid peptide, mediates progesterone-negative feedback on gonadotropin-releasing hormone (GnRH) neurons in other species. The role of dynorphin in humans is unclear. The objective of this study was to determine if dynorphin fibers have close contacts with GnRH neurons in humans.

Orphanin FQ: evidence for a role in the control of the reproductive neuroendocrine system.

Orphanin FQ (OFQ), also known as nociceptin, is a member of the endogenous opioid peptide family that has been functionally implicated in the control of pain, anxiety, circadian rhythms, and neuroendocrine function. In the reproductive system, endogenous opioid peptides are involved in the steroid feedback control of GnRH pulses and the induction of the GnRH surge. The distribution of OFQ in the preoptic area and hypothalamus overlaps with GnRH, and in vitro evidence suggests that OFQ can inhibit GnRH secretion from hypothalamic fragments.

Expression of leptin receptor and suppressor of cytokine signaling-3 genes in adenohypophysis of normal-fed and fasted cows.

Expression of leptin receptor (LR) and suppressor of cytokine signaling (SOCS)-3 genes was investigated in normal-fed and fasted cows. Fasting did not affect LR mRNA, but increased SOCS-3 mRNA in the adenohypophysis, suggesting that heightened responsiveness of fasted cows to leptin is not dependent upon alterations in LR or SOCS-3 mRNA in the adenohypophysis.

Divergent effects of leptin on luteinizing hormone and insulin secretion are dose dependent.

We have shown recently that fasting permits leptin to modulate both luteinizing hormone (LH) and insulin secretion in cows. In rodents, leptin causes divergent effects on LH and insulin release that are dose dependent. To test the hypothesis that leptin effects on LH and insulin secretion in fasted cows are dose related, we examined the effects of various doses of recombinant ovine leptin (oleptin) in mature cows.