Endocrine changes from birth to puberty in the heifer

Dodson, Sara E.; McLeod, B. J.; Haresign, W.; Peters, A. R.; Ge, Lan

doi:10.1530/jrf.0.0820527

Cited by 49 publications

(42 citation statements)

References 23 publications

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“…A high sensitivity of 0.1 ng/mL was obtained when 20 mL of plasma was taken for estimation. The sensitivity of the present RIA is higher than those reported in other ruminants [16,20] and comparable to extraction RIA [17,21] and to direct RIA. [8,22] The level of plasma progesterone recorded in mithun cows during the estrous cycle is in accord with other bovines.…”

Section: Discussionsupporting

confidence: 57%

Development and Validation of a Sensitive Radioimmunoassay for Progesterone Estimation in Unextracted Mithun (Bos frontalis) Plasma

Mondal

Prakash

Rajkhowa

et al. 2005

Journal of Immunoassay and Immunochemistry

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The objective of the study was to develop and validate a simple, reliable, and highly sensitive radioimmunoassay (RIA) for progesterone determination in mithun (Bos frontalis) plasma. The RIA was carried out in 20 microL unextracted mithun plasma. The progesterone standards ranging from 2 to 500pg/20 microL/tube were prepared in charcoal-treated hormone-free plasma. The sensitivity of the RIA procedure was 2 pg progesterone/20 microL/tube, which corresponds to 0.1 ng/mL; the 50 percent relative binding sensitivity was seen at 32pg/20 microL/tube. Plasma volumes for the RIA, viz. 10 and 20 microL, did not influence the shape of standard curve, even though a slight drop in the counts was seen with higher plasma volumes. For the biological validation of the assay, three cyclic, three in early pregnancy, and two in late pregnancy mithuns were used. Blood samples collected at weekly intervals for 42 days, from all animals, were assayed for plasma progesterone. The peak level of progesterone was registered at day 14 (day 21 of sampling) of the estrous cycle and the lowest at estrus; the progesterone concentrations increased and decreased gradually as sampling time advanced, in early and late pregnancy, respectively, which confirm the biological validation of the RIA. The RIA avoids the troublesome and laborious plasma extraction procedures. In conclusion, the RIA developed for progesterone determination in mithun blood plasma is sufficiently reliable, simple, and sensitive enough to estimate progesterone in all physiological variations in mithun.

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Section: Discussionsupporting

confidence: 57%

Development and Validation of a Sensitive Radioimmunoassay for Progesterone Estimation in Unextracted Mithun (Bos frontalis) Plasma

Mondal

Prakash

Rajkhowa

et al. 2005

Journal of Immunoassay and Immunochemistry

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“…Schams et al (1981) describe prepubertal basal concentrations of gonadotrophins as exhibiting a biphasic profile, a rise and fall in LH and FSH occurring between birth and 20 weeks of age. However, Dodson et al (1988) considered that serum LH and FSH concentrations decreased from birth to 15 and 19 weeks, respectively, and then increased to 39 weeks of age. Our data (Fig.…”

Section: Discussionmentioning

confidence: 99%

Effects of naloxone on circulating gonadotrophin concentrations in prepubertal heifers

Evans¹,

Currie²,

Rawlings³

1992

Reproduction

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The pattern and opioidergic control of the secretion of gonadotrophins in prepubertal heifer calves were examined. Ten age-matched Hereford heifer calves were weighed and a blood sample was taken every 2 weeks from 2 to 25 weeks of age and then weekly until 60 weeks of age. At 60 weeks, a fertile bull was introduced and at 75 weeks of age pregnancy diagnosis was performed by transrectal ultrasonography. At 4, 12, 18, 24 and 32 weeks of age, the opioid antagonist naloxone was injected (i.v., n = 5; 1 mg kg-1 body weight) each hour for 12 h. Control heifers received sterile saline at the same ages. Blood samples were collected every 12 min for the 12 h treatment and serum samples were analysed for luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Samples taken once every 2 weeks from 2 to 60 weeks were analysed for LH, FSH and oestradiol, and weekly samples were taken for progesterone determination. There was no effect of naloxone on the age at puberty, which was 56.2 +/- 0.7 weeks at a body weight of 388.5 +/- 8.0 kg. The mean age at conception was 63.4 +/- 0.5 weeks. On the basis of samples taken every other week, serum concentrations of LH were high at 10 weeks and between 40 and 60 weeks of age. From the periods of intensive blood collection, the early rise in mean serum concentrations of LH appeared later at 12 and 18 weeks of age and was caused by a rise in LH pulse amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Puberty is the first spontaneous estrus/ovulation that occurs following a process where the endocrine function of the hypothalamus, pituitary, ovaries and uterus become synchronized (Dodson et al 1988;Del Vecchio et al 1992). It has been well established in cattle and sheep that puberty or postpartum resumption of estrous cycles is dependent upon synchronization of gonadotrophin-releasing hormone, luteinizing hormone and estradiol secretion among the hypothalamus, pituitary and ovaries (Gonzalez-Padilla et al 1975a;Dodson et al 1988).…”

Section: Effects Of Bull Exposurementioning

confidence: 99%

“…It has been well established in cattle and sheep that puberty or postpartum resumption of estrous cycles is dependent upon synchronization of gonadotrophin-releasing hormone, luteinizing hormone and estradiol secretion among the hypothalamus, pituitary and ovaries (Gonzalez-Padilla et al 1975a;Dodson et al 1988). The occurrence of standing heat and elevated progesterone a week later were evidence of this synchrony to cause a follicle to ovulate and luteinize.…”

Section: Effects Of Bull Exposurementioning

confidence: 99%

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

Small

Vecchio²,

McCaughey³

et al. 2000

Can. J. Anim. Sci.

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. 2000. The effects of bull exposure and lasalocid on the development of replacement beef heifers. Can. J. Anim. Sci. 80: [615][616][617][618][619][620][621][622][623][624]. 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, sirebreed and body weight to one of two similar winter housing facilities (with or without sterilized bulls), and to one of two foragebased (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 PGF 2α ) 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 PGF 2α response rate. Bull exposure advanced puberty in winterborn 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. Anim. Sci. 80: 615-624. Lors du sevrage à l'automne, des génisses croisées (n = 224) nées soit á l'hiver (janvier-février) ou au printemps (mars-avril) dernier étaient réparties par catégorie d'âge et selon la race paternelle et le poids vif, entre deux installations semblables de logement d'hiver, en présence ou non de taureaux stérilisés et deux régimes alimentaires à base de fourrages grossiers (87 %), avec ou sans administration de lasalocide à raison de 220 mg j -1 dans chaque installation. La détection des chaleurs se faisait deux fois par jour. Pour la première mise à la reproduction, à l'âge de 14 mois, on utilisait l'IA programmé, soit 66 h après traitement de PGF 2α . Les concentrations plasmatiques de progestérone servaient de base pour la confirmation de l'oestrus et de l'ovulation et pour établir le taux de réponse à la PGF 2α . La présence des taureaux accélérait la venue de la puberté chez les génisses d'hiver, mais la retardait chez les génisses de printemps (P ≤ 0,029). Ces dernières avaient, par ailleurs, un taux de gravidité après IA plus élevé en l'absence qu'en présence de taureau, soit 27,1 contre 59,1 ± 4,7 % (P < 0,001), alors que l'inver...

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Endocrine changes from birth to puberty in the heifer

Cited by 49 publications

References 23 publications

Development and Validation of a Sensitive Radioimmunoassay for Progesterone Estimation in Unextracted Mithun (Bos frontalis) Plasma

Development and Validation of a Sensitive Radioimmunoassay for Progesterone Estimation in Unextracted Mithun (Bos frontalis) Plasma

Effects of naloxone on circulating gonadotrophin concentrations in prepubertal heifers

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

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