A study on ghrelin and LH secretion after short fasting and on ghrelin levels at perioestrual period in dairy cattle

Abstract

In two experiments, we studied (a) the changes of LH secretion in heifers under different feeding schedules and (b) total ghrelin concentration at oestrus in cows and heifers. In experiment one, synchronized heifers were allocated in three groups (R, regularly fed controls; F, fasted; and F-F fasted-fed). One day after the completion of the oestrous induction protocol, group F and F-F animals stayed without feed for 24 hr; thereafter, feed was provided to R and F-F cattle; 2 hr later, GnRH was administered to all animals. Blood samples were collected for ghrelin, progesterone, LH and cortisol concentrations. Fasting caused increased ghrelin concentrations in groups F and F-F, while in response to GnRH, LH surge was significantly attenuated in groups F and F-F compared to R. In experiment 2, lactating cows and heifers were used. On day 9 of a synchronized cycle, PGF2α was administered, and blood samples were collected twice daily until the third day after oestrus and analysed for progesterone, estradiol, ghrelin, glucose and BHBA concentrations. No difference was recorded between groups in steroids and BHBA concentrations. In comparison to mid-luteal values, ghrelin concentrations significantly increased at perioestrual period in cows, but not in heifers. This study provides evidence that starving-induced elevated ghrelin concentrations can have suppressing effect on LH secretion, even after ghrelin's restoration to basal values and that during oestrus, ghrelin secretion is differently regulated in cows and heifers, likely being independent from oestradiol concentrations. Further research is required to identify the determining factors that drive the different regulation of ghrelin secretion in cows and heifers.

Ghrelin antagonist overrides the mRNA expression of NPY in hypothalamus in feed restricted ewes

“…Moreover, others have reported that ghrelin concentration increased and LH concentration decreased when feed restricting cows and heifers but blood progesterone concentration did not change [33]. The restricted period implemented by Chouzouris et al [33] was shorter than the period used in Experiment I; but it had a similar time period as Experiment II. It is possible that in the bovine and ovine, blood progesterone concentration is not associated with plasma ghrelin concentration.…”

“…The supraphysiological doses of ghrelin used in this study, however, may have contributed to the decrease in plasma progesterone concentration in the rats [ 32 ]. Moreover, others have reported that ghrelin concentration increased and LH concentration decreased when feed restricting cows and heifers but blood progesterone concentration did not change [ 33 ]. The restricted period implemented by Chouzouris et al [ 33 ] was shorter than the period used in Experiment I; but it had a similar time period as Experiment II.…”

Metabolismo De Ruminantes Em Lactação No Estado De Jejum: Regulação Hormonal, Formação De Corpos Cetônicos E Produção De Leite

“…Foi verificado que durante períodos de redução a matéria seca, a expressão do gene da grelina foi regulado positivamente (TENA-SEMPERE, 2007). Em um estudo com novilhas em jejum foi verificado que elevadas concentrações de grelina induzidas por situações de restrição alimentar podem afetar negativamente a secreção de LH, mesmo após a restauração da grelina aos valores basais (CHOUZOURIS et al, 2018). Embora a ação de neuropeptídios estejam relacionadas a ação da grelina, mais pesquisas precisam ser realizadas para melhor elucidar esse mecanismo.…”

Metabolic Profile of Steers Subjected to Normal Feeding, Fasting, and Re-Feeding Conditions

“…The hypothalamus, especially through its centers of hunger and satiety, controls ingestion by modulating various hormones, blood concentrations of various metabolites, and the autonomic nervous system. The causes of anorexia are the most diverse, and they can generate changes in the blood metabolic profile, which is frequently used in veterinary clinical diagnosis [ 4 , 5 , 6 ].…”