Effects of Thyroidectomy on Egg Production, Molt, and Plasma Thyroid Hormone Concentrations of Turkey Hens , ,

Lien, R. J.; Siopes, T. D.

doi:10.3382/ps.0681126

Cited by 37 publications

(17 citation statements)

References 27 publications

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“…The blood plasma was analyzed for thyroid hormone content and blood plasma glucose concentration. Both T 4 and T 3 concentrations were determined using the radioimmunoassay 8 of Lien and Siopes (1989). All blood plasma samples from hens or embryos were analyzed in one assay so there was no interassay variation; the intraassay coefficients of variation for the hen samples were 17.3 and 18.3% for the T4 and T3 assays, respectively.…”

Section: Methodsmentioning

confidence: 99%

Influence of Diet-Mediated Maternal Thyroid Alterations on Hatchability and Metabolism of Turkey Embryos

et al. 1991

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Large White turkey breeder hens from a strain exhibiting poor hatchability were fed thyroid-altering diets. The following dietary treatments were fed to randomized groups of hens for 15 wk of egg laying: 1) 16.5% protein turkey breeder diet (control), 2) the control diet containing 2.1 ppm supplemental iodine, 3) the control diet containing .1% thiouracil, and 4) the control diet containing .5 ppm triiodothyronine (T3). Blood samples were taken from hatching embryos from hens fed each diet. Embryonic hearts and livers were weighted prior to and during pipping as well as after hatching. Blood plasma was analyzed for thyroxine (T4), T3, and glucose. Livers were assayed for glucose-6-phosphatase activity. Supplemental maternal dietary iodine elevated embryonic T4 concentrations prior to pipping. Dietary T3 and iodine increased hepatic glucose-6-phosphatase activity and blood plasma glucose concentration prior to pipping. Feeding thiouracil increased embryonic liver weights but decreased heart and body weights. Blood plasma T4 was elevated in embryos from hens fed thiouracil but blood glucose levels were depressed because of a lack of increased glucose-6-phosphatase activity. Feeding iodine decreased the enzyme activity at internal pipping. It is suggested from the data that maternal thyroid metabolism may influence hatchability via embryonic thyroid and carbohydrate metabolism during hatching.

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Section: Methodsmentioning

confidence: 99%

Influence of Diet-Mediated Maternal Thyroid Alterations on Hatchability and Metabolism of Turkey Embryos

et al. 1991

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“…3. HY + T 4 and TN (22°C): beginning on d 1 of HS, a group of thiouracil-treated birds was given a normal diet that contained 0.5 mg/kg of T 4 as a thyroid hormone replacement (B. C. Wentworth, personal communication;Newcomer, 1957;Raheja and Snedecor, 1970;Péczely et al, 1980;Lien and Siopes, 1989). 4.…”

Section: Study 2-hypothyroid-mediated Hs Effectsmentioning

confidence: 99%

“…Mitchell and Goddard (1990) suggested that HS effects on thyroid could be mediated through reduced utilization of T 3 or reduced activity of hepatic deiodinase. Because of the involvement of the thyroid during the onset of puberty and reproductive function in birds (Decuypere and Kühn, 1988), a disruption of thyroid activity by HS would be expected to have an effect on reproductive status of the hen, as indeed surgical thyroidectomy has been shown to have done (Péczely et al, 1980;Lien and Siopes, 1989).…”

Section: Introductionmentioning

confidence: 98%

Reproductive hormones, hepatic deiodinase messenger ribonucleic acid, and vasoactive intestinal polypeptide-immunoreactive cells in hypothalamus in the heat stress-induced or chemically induced hypothyroid laying hen

2010

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Heat stress (HS) effects on reproductive and thyroid hormones have been well documented; however, mechanisms of action are not well understood. Two studies were conducted to determine whether HS-induced and hypothyroid-induced effects are similar in the laying hen, with regard to reproductive hormones and vasoactive intestinal polypeptide (VIP)-immunoreactive cells in the hypothalamus. In study 1, thirty 32-wk-old Hy-Line W-36 laying hens, housed at 22 degrees C, were cannulated. On d 0 and then on d 1 to 5 of HS (35 degrees C, 50% RH), a daily blood sample was obtained and assayed for triiodothyronine (T(3)), thyroxine (T(4)), 17beta-estradiol (E(2)), progesterone (P(4)), prolactin (PRL), and VIP, and T(3):T(4)was calculated. On d 0, 1, 3, and 5, livers were obtained for hepatic type I deiodinase mRNA (cDI-1) determination. In study 2, eighty 32-wk-old hens were randomly assigned to 4 treatments of 20 birds each: 1) HS (36.5 degrees C, 50% RH), 2) thiouracil-induced hypothyroidism (HY), 3) HY + T(4) administration, and 4) control (22 degrees C). Beginning on d 1 of the 5-d study, daily blood samples (3.0 mL) were removed and assayed as in study 1. On d 5, brains were removed from 3 hens/treatment and immunoreactivity of VIP cells was determined. In study 1, HS reduced E(2), P(4), T(3) (P = 0.0001), T(3):T(4) ratio (P = 0.0078), and hepatic type I deiodinase mRNA (P = 0.0204) and increased T(4) (P = 0.0013); there was no effect on VIP or PRL. In study 2, HS and HY reduced T(3), T(3):T(4) ratio, and E(2) (P = 0.0001) and increased PRL (P = 0.0045); HS alone decreased P(4) (P = 0.0001). In HY + T(4), plasma E(2) and PRL were similar to control. Vasoactive intestinal polypeptide increased in plasma of HY birds, but there was no effect of HS or HY + T(4). Immunoreactive VIP cells increased (P = 0.0036) in nucleus inferior hypothalami of HS and HY brains. In HY + T(4), VIP immunoreactive cell numbers were similar to control. It appears that HY induced chemically or by HS exerts similar effects on reproductive hormones in the hen; the results suggest involvement of the VIP-PRL pathway even though peripheral blood concentrations were not consistent between studies.

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“…Little is known of similar mechanisms for programming of PR in turkeys, but long day lengths and thyroxine are required for ovarian development and PR (Lien and Siopes, 1989;Siopes, 1997). We have reported that circulating thyroid hormones immediately before and after photostimulation (−6 d to +14 d) are not indicative of a programming event for PR in turkeys (Proudman and Siopes, 2002Siopes, , 2006.…”

Section: Introductionmentioning

confidence: 84%

Exposure duration to long day lengths associated with the expression of photorefractoriness in turkey breeder hens

Siopes

Proudman

2009

Poultry Science

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In addition to inducing egg production, exposure to long days concomitantly activates processes that eventually result in photorefractoriness (PR) and cessation of egg production. Experiments were conducted to evaluate the duration of exposure to long days that result in these processes. In each of 3 experiments, we subjected Large White turkey breeder hens to long days (16 or 18 h per day) for differing lengths of time from initial photostimulation and then returned them to a photoperiod (12L:12D) that provided sufficient, but decreased, photoperiodic drive to support egg production but not induce PR. Photoresponsiveness was then evaluated by egg production after a return to a longer day length (20 h per day) late in the lay period and beyond the mean onset of PR typical for these turkey hens. Hens that have undergone any reduction in photoresponsiveness should not increase egg production in response to the increased photoperiod. From experiments 1 and 2, exposure to long days for as little as 1 d and as much as 9 wk from initial photostimulation did not result in an alteration in subsequent photoresponsiveness. This was based on an increased egg production response to a change in photoperiod from 12L:12D to 20L:4D after 20 wk of photostimulation that was similar to controls held continuously on 12L:12D and opposite to the response of controls held continuously on 18L:6D. It was clear that PR had been fully programmed by 20 wk of exposure to long days. Exposure to long days for 12 wk (experiment 3) resulted in a partial alteration of subsequent photoresponsiveness. It was concluded that programming of PR during late spring-summer season occurs after 9 wk of long day exposure, is not fully expressed by 12 wk of long days, and can be fully expressed by 20 wk of photostimulation.

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Effects of Thyroidectomy on Egg Production, Molt, and Plasma Thyroid Hormone Concentrations of Turkey Hens , ,

Cited by 37 publications

References 27 publications

Influence of Diet-Mediated Maternal Thyroid Alterations on Hatchability and Metabolism of Turkey Embryos

Influence of Diet-Mediated Maternal Thyroid Alterations on Hatchability and Metabolism of Turkey Embryos

Reproductive hormones, hepatic deiodinase messenger ribonucleic acid, and vasoactive intestinal polypeptide-immunoreactive cells in hypothalamus in the heat stress-induced or chemically induced hypothyroid laying hen

Exposure duration to long day lengths associated with the expression of photorefractoriness in turkey breeder hens

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