Photoperiod effects on the development of beef heifers

2003 ◽  
Vol 83 (4) ◽  
pp. 721-730 ◽  
Author(s):  
J. A. Small ◽  
N. D. Glover ◽  
A. D. Kennedy ◽  
W. P. McCaughey ◽  
D. R. Ward
Keyword(s):  
Body Weight ◽  
Body Weight Gain ◽  
Prolactin Secretion ◽  
Outdoor Environment ◽  
Serum Prolactin ◽  
Beef Heifers ◽  
Serum Progesterone ◽  
Ambient Temperatures ◽  
Natural Photoperiod ◽  
Sire Breed

Crossbred beef heifers (n = 144) were assigned at weaning (187 ± 14 d of age) by body weight (225 ± 23 kg) and sire breed (British/Continental) to one of two photoperiod treatments from 21 Decem ber 1998 (0 wk) until 10 May 1999 (20 wk): natural photoperiod (NP) that gradually increased from 8.1 h (0 wk) to 15.2 h (20 wk) and, extended photoperiod (EP) that consisted of natural + supplemental light (400 lx, 1 m above ground) to extend photoperiod to 16 h. Rations were formulated for two-steps of body weight gain (0.6 and 1.2 kg d-1) to achieve 60% of mature weight at 18 wk. Visual observations of estrus behavior were made twice daily and confirmed by serum progesterone. Body weight, backfat and serum prolactin data were determined for each 4-wk period. Ambient temperatures averaged -12.2 ± 6°C in winter (0 to 12 wk) and 4.2 ± 5°C in spring (12 to 20 wk). Gain in body weight was greater (P < 0.05) and backfat lower (P < 0.05) for EP than NP treatments from -2 to 6 wk and only 1% of heifers had attained puberty during this period. However, as yearlings at similar (P > 0.05) body weight and backfat, more (P < 0.05) EP than NP heifers had attained puberty (84.7% vs. 69.4%). Prolactin was greater (P < 0.05) for EP than NP treatments from 2 to 6 wk (10.3 vs 5.5 ± 1.2 ng mL-1). Management of photoperiod influences attainment of puberty and prolactin secretion in beef heifers housed in an outdoor environment. Key words: Photoperiod, puberty, estrus, beef heifers, prolactin

The effects of bull exposure and lasalocid on the development of replacement beef heifers

2000 ◽  
Vol 80 (4) ◽  
pp. 615-624 ◽  
Author(s):  
J. A. Small ◽  
R. P. Del Vecchio ◽  
W. P. McCaughey ◽  
D. R. Ward ◽  
W. P. Sutherland
Keyword(s):  
Body Weight ◽  
Response Rate ◽  
Body Weight Gain ◽  
Management Tool ◽  
Delayed Puberty ◽  
Beef Heifers ◽  
Plasma Progesterone ◽  
First Time ◽  
Sire Breed ◽  
Housing Facility

At weaning in the fall, crossbred heifers (n = 224), born in either the winter (January–February) or spring (March–April), were assigned on the basis of age, sire-breed and body weight to one of two similar winter housing facilities (with or without sterilized bulls), and to one of two forage-based (87%) diets (with or without lasalocid, 200 mg d−1) within each housing facility. Observations for estrus were made twice daily. Timed AI (66 h after PGF2α) was used to breed heifers for the first time at 14 mo of age. Plasma progesterone concentrations were used to confirm estrus/ovulation and to determine the PGF2α response rate. Bull exposure advanced puberty in winter-born heifers, but delayed puberty in spring-born heifers (P ≤ 0.029). Similarly, timed AI pregnancy for winter-born heifers was higher with than without bull exposure (58.9 vs. 32.5 ± 5.3%; P = 0.017) while the opposite occurred for the spring-born group (27.1 vs. 59.1 ± 4.7%; P < 0.001). Bull-exposed spring-born heifers were the oldest at calving, the latest to calve, and their calves had the slowest growth and lowest weaning weight means (P < 0.027). Lasalocid did not influence puberty (P ≥ 0.273), had a small effect on body weight gain (P ≥ 0.033) that did not limit attainment of optimal body weight or condition at AI, but enhanced response rate for spring-born heifers (P = 0.075) and conception rate for winter-born heifers (P = 0.047). The efficacy of bull exposure and lasalocid is dependent upon the proximity of heifers to the attainment of puberty when the treatments are introduced; further research is required to determine the most appropriate use of either management tool for developing beef replacement heifers. Key words: Puberty, heifer development, bull exposure, ionophore, estrus, conception

scholarly journals Cordycepin Modulate Body Weight by Reducing Prolactin via an Adenosine A1 Receptor

2018 ◽  
Author(s):  
Yuan Li ◽  
Yan Li ◽  
Xueyan Wang ◽  
Hongyue Xu ◽  
Chao Wang ◽  
...  
Keyword(s):  
Body Weight ◽  
Prolactin Secretion ◽  
Adenosine A1 Receptor ◽  
Gh3 Cells ◽  
Serum Prolactin ◽  
Prolactin Release ◽  
Adenosine A1 ◽  
A1 Receptor

Cordycepin is an extract from the insect fungus Cordyceps. militaris, which is a traditional medicine with various biological function. In previous studies, cordycepin had been reported with excellent anti-obesity effect, but the mechanism is unclear. A large quantity of evidences showed that prolactin plays an important part in body weight regulation, hyperprolactinemia can promote appetite and accelerate fat deposition. In this study, we explored the molecular mechanism of the anti-obesity effect of cordycepin by reducing prolactin release via an adenosine A1 receptor. In vivo, obese rats model was induced by high fat diet for 5 weeks, the serum and liver lipids coupling with serum prolactin were reduced by treatment of cordycepin, the results suggested that cordycepin is a potential drug for therapying obesity which could be related with prolactin. In vitro, cordycepin could inhibit prolactin secretion in GH3 cells via upregulating the expression of adenosine A1 receptor, the inhibition effect could be blocked by an antagonist of adenosine receptor A1 DPDPX, prolactin induced the upregulation of lipogenesis genes PRLR, and P-JAK2 in 3T3-L1 cells. Intriguingly, cordycepin would down-regulate the expression of prolactin receptor (PRLR). Thus, we concluded that cordycepin modulate body weight by reducing prolactin release via an adenosine A1 receptor.

Interaction of dietary energy source and body weight gain during the juvenile period on metabolic endocrine status and age at puberty in beef heifers

2017 ◽  
Vol 95 (5) ◽  
pp. 2080
Author(s):  
C. C. Allen ◽  
L. O. Tedeschi ◽  
D. H. Keisler ◽  
R. C. Cardoso ◽  
B. R. C. Alves ◽  
...  
Keyword(s):  
Energy Source ◽  
Body Weight ◽  
Weight Gain ◽  
Body Weight Gain ◽  
Dietary Energy ◽  
Beef Heifers ◽  
Juvenile Period ◽  
Endocrine Status ◽  
Age At Puberty

Opioidergic regulation of prolactin secretion during pregnancy: role of ovarian hormones

1997 ◽  
Vol 155 (1) ◽  
pp. 99-106 ◽  
Author(s):  
M Soaje ◽  
RP Deis
Keyword(s):  
Ovarian Hormones ◽  
Prolactin Secretion ◽  
High Serum ◽  
Opioid System ◽  
Serum Prolactin ◽  
Stimulatory Action ◽  
Serum Progesterone ◽  
Naloxone Administration ◽  
Ru 486 ◽  
Naloxone Treatment

We have recently demonstrated the existence of a neuromodulatory regulation of prolactin secretion by the opioid system showing a paradoxical opioid-induced prolactin suppression at the end of pregnancy. The aim of this study was to determine a possible interaction between the opioid system and ovarian hormones on the release of prolactin during pregnancy. Serum prolactin levels measured at 1800 h were significantly higher on days 3 and 6 of pregnancy when compared with the other days of gestation. These increases in serum prolactin were reduced significantly by naloxone (2 mg/kg) administered at 1730 h and by RU-486 (10 mg/kg) administered at 0800 h. The response induced by RU-486 was potentiated by naloxone only on day 3. On days 7, 13 and 16, prolactin secretion was not modified by RU-486 and/or naloxone treatment. In RU-486 pretreated rats, naloxone administration increased serum prolactin levels only on day 16 of pregnancy. Interestingly, progesterone treatment (0.5 mg/rat) on days 13, 14 and 15 of pregnancy prevented the high increase in serum prolactin induced by RU-486 and naloxone on day 16 of pregnancy. The progressive increase and decrease of serum progesterone concentration during pregnancy was not modified by naloxone treatment. The participation of oestrogen in the regulation of prolactin secretion by the opioid system on days 3, 16 and 19 was examined by treating these groups of rats with oestradiol benzoate or tamoxifen citrate. Oestradiol (2 micrograms/rat) significantly increased serum prolactin levels on day 3 and naloxone administration did not modify this increase. No effect was observed after oestradiol (5 micrograms/rat) and naloxone treatment on days 16 and 19 of pregnancy. Oral administration of tamoxifen (500 micrograms/kg) the previous day did not modify the serum prolactin concentration measured at 1800 h in oil-treated rats on days 3, 16 and 19 of pregnancy. The antioestrogen completely abolished the naloxone-induced prolactin secretion on day 16 in rats pretreated with RU-486 but no effect was observed on day 19. When tamoxifen was administered on days 14 and 15 of pregnancy, the high serum prolactin levels on day 19 induced by treatment with RU-486 and naloxone were significantly reduced. In conclusion, these results provide an important new insight into the existence of a dual neuromodulatory regulation of prolactin secretion by the opioid system during pregnancy. After a stimulatory action during the first days, there is a change to an inhibitory control at the end of pregnancy, starting around day 16. Moreover, the activation of the inhibitory modulation of the opioid system on prolactin secretion on days 16 and 19 of pregnancy seems to be mediated by changes in the oestrogen and progesterone action.

Long-term reductions in GH, insulin-like growth factor-I and body weight gain in rats treated neonatally with antibodies to rat GH

1990 ◽  
Vol 124 (3) ◽  
pp. 381-386 ◽  
Author(s):  
M. J. Gardner ◽  
D. J. Flint
Keyword(s):  
Body Weight ◽  
Weight Gain ◽  
Growth Factor ◽  
Body Weight Gain ◽  
Female Rats ◽  
Serum Prolactin ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Growth Factor I

ABSTRACT Treatment of neonatal rats on days 2–5 with antibodies against rat GH (rGH) markedly reduced body weight gain and serum concentrations of insulin-like growth factor-I for 6–8 weeks in both females and males, after which weight gain normalized without evidence of catch-up growth. There were no significant effects on serum prolactin, tri-iodothyronine or corticosterone. Testis and ovarian weights were reduced, although only in proportion to body size. In females, but not males, the treated rats, though lighter, had increased fat deposition in the parametrial depot. Pituitary weight was considerably reduced over 100 days later, as was the pituitary content of GH, but not prolactin. The response to GH-releasing factor of both male and female rats was also greatly reduced at this time. Taken together with the fact that these rGH antibodies can bind directly to somatotrophs, we propose that the long-term effects of the antibodies are induced by specific somatotroph destruction. Journal of Endocrinology (1990) 124, 381–386

The effect of bromocriptine during early pregnancy in the rat: inhibition of implantation

1980 ◽  
Vol 94 (2) ◽  
pp. 268-272 ◽  
Author(s):  
U. Müller ◽  
Th. Bauknecht ◽  
J. W. Siebers
Keyword(s):  
Body Weight ◽  
Early Pregnancy ◽  
Prolactin Secretion ◽  
Teratogenic Effect ◽  
Preimplantation Embryos ◽  
Progesterone Concentration ◽  
Serum Progesterone ◽  
Luteal Cells ◽  
Progesterone Production ◽  
Uterine Mucosa

Abstract. The increase in the number of the ovarian LH/hCG-receptors and of serum progesterone concentration during pregnancy in the rat is highly dependent on the presence of prolactin during the luteinization process. Blocking of the hypophyseal prolactin secretion by twice daily injections of 2 μg/g body weight bromocriptine into rats from the first day of pregnancy onwards prevents the increase in ovarian hCG-binding and progesterone production. Similar results are obtained by application of bromocriptine during the first three days only or either at day 1, 3 or 5 after mating. In all bromocriptine treated rats implantation of blastocysts does not occur. The failure to implant is not due to a teratogenic effect of bromocriptine onto preimplantation embryos, but is probably the consequence of changes of the uterine mucosa caused by the lack of progesterone production in the luteal cells.

A modulatory role of endogenous opioids on prolactin secretion at the end of pregnancy in the rat

1994 ◽  
Vol 140 (1) ◽  
pp. 97-102 ◽  
Author(s):  
M Soaje ◽  
R P Deis
Keyword(s):  
Time Course ◽  
Prolactin Secretion ◽  
Endogenous Opioids ◽  
Opioid Antagonist ◽  
Serum Prolactin ◽  
Serum Progesterone ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
Ru 486 ◽  
Prolactin Suppression

Abstract It is well known that the fall in serum progesterone concentrations during late pregnancy induces prolactin secretion in rats. On day 19 of pregnancy, administration of 10 mg of the antiprogesterone RU-486/kg induced a small but significant increase in serum prolactin. A lower dose (2 mg/kg) was not effective. Administration of naloxone (2 mg/kg) to pregnant rats on day 19 of pregnancy did not modify circulating prolactin but, after RU-486 treatment, a notable increase in serum prolactin was obtained 30 min after naloxone was given. The lack of effect of naloxone-methobromide in pregnant rats pretreated with RU-486 may indicate that the opioid-induced prolactin suppression acts centrally, most probably at the hypothalamic level. During day 21 of pregnancy, the time-course of prolactin secretion, measured at 0900, 1400, 1900 and 2200 h, was inversely correlated with circulating progesterone levels. At 0900 h, serum prolactin was very low with high serum progesterone concentrations but a significant increase in serum prolactin occurred at 2200 h; this was coincident with a significant decrease in the steroid. The stimulatory effect of naloxone on prolactin secretion was clearly dependent on the circulating progesterone level. Thus, at 1900 h of day 21, naloxone induced a significant increase in serum prolactin but, at 2200 h, the opioid antagonist dramatically enhanced the circulating level of prolactin. The serum prolactin increase induced by naloxone at 1900 h was prevented by the s.c. administration of 5 mg progesterone given 7 h earlier. Similarly, the large increase in serum prolactin levels at 1800 h on day 19 of pregnancy, after administration of RU-486 plus naloxone, was completely abolished by treatment with CB154. The lack of effect of RU-486 and naloxone on serum prolactin levels in virgin rats on the day of pro-oestrus demonstrates that the effect of naloxone on prolactin in pregnant rat is peculiar to the end of pregnancy. In conclusion, the attenuation of the central inhibitory action of progesterone facilitates the release of prolactin which is dramatically enhanced by naloxone treatment. These results provide an important new insight into the existence of a neuromodulatory regulation of prolactin secretion by the opioid system showing a paradoxical opioid-induced prolactin suppression at the end of pregnancy. Journal of Endocrinology (1994) 140, 97–102

Effect of prepubertal body weight gain and breed on carcass composition at puberty in beef heifers

1993 ◽  
Vol 71 (5) ◽  
pp. 1104-1111 ◽  
Author(s):  
H. W. Hopper ◽  
S. E. Williams ◽  
D. J. Byerley ◽  
M. M. Rollosson ◽  
P. O. Ahmed ◽  
...  
Keyword(s):  
Body Weight ◽  
Weight Gain ◽  
Body Weight Gain ◽  
Carcass Composition ◽  
Beef Heifers

Patterns of progesterone, melatonin and prolactin secretion in ewes maintained in four different photoperiods

1983 ◽  
Vol 97 (2) ◽  
pp. 229-242 ◽  
Author(s):  
D. J. Kennaway ◽  
L. M. Sanford ◽  
B. Godfrey ◽  
H. G. Friesen
Keyword(s):  
Pineal Gland ◽  
Endocrine System ◽  
Prolactin Secretion ◽  
Constant Light ◽  
Ovarian Activity ◽  
Dark Phase ◽  
Melatonin Secretion ◽  
Night Time ◽  
Serum Progesterone ◽  
Natural Photoperiod

Twenty-four-hour patterns of serum melatonin and prolactin levels were determined in ewes on nine occasions during a year. The sheep were maintained in four different photoperiods: room 1, simulated natural photoperiod; room 2, normal daylength extremes twice in 12 months, changes occurring in a regular fashion; room 3, alternating long (16 h) and short (8 h) days for 90 days; room 4, constant light. Cyclic ovarian activity, determined by twice-weekly determinations of serum progesterone, commenced in rooms 1, 2 and 3 after a transition from long to short daylength and terminated during long daylength. Thus in rooms 2 and 3 there were two periods of ovarian activity. In room 4 (constant light) ovarian activity began earlier than in room 1 and was of greater duration (240 days v. 190 days). Basal prolactin levels were highest (50–134 μg/l) during periods of long daylength and lowest (< 10 μ/l) in short daylength. Ewes maintained in constant light had an intermediate level (21–62 μg/l) throughout the study. Melatonin secretion was lowest during daylight (< 78 pmol/l) and highest during darkness. Night-time melatonin levels varied markedly from hour to hour and between individuals in rooms 1, 2 and 3. There was, however, no consistent seasonal change in the absolute levels of melatonin, although the duration of melatonin secretion did closely follow the length of the dark phase. There were no significant changes in melatonin levels during the oestrous cycle. Ewes kept in constant light had < 78 pmol melatonin/l throughout the period of study. If the pineal gland is involved in transmitting photoperiodic information to the endocrine system, then it is most likely to be by means of an interaction between duration of melatonin secretion and an underlying change in sensitivity of end organs to melatonin.

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