The Role of Thyroidal Materials and of Synthetic Goitrogens in Animal Production and an Appraisal of their Practical Use

Blaxter, K. L.; Reineke, E. P.; Crampton, E. W.; Petersen, W. E.

doi:10.2527/jas1949.83307x

Cited by 84 publications

(17 citation statements)

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“…The earlier work of Koger and Turner [1943], Blaxter et al [1949] and Maqsood and Reineke [1950] showed similar findings, i.e. mild hyperthyroidism accelerated growth in young animals of several species.…”

Section: Body Weightsupporting

confidence: 66%

Pituitary-testicular function changes in hypo-and hyperthyroid male rats

Amin¹,

Elsheikh²

1977

Cells Tissues Organs

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The influence of thyroid deficiency and the administration of thyroxine on pituitary-testicular function were studied in male albino rats from weaning age (22 days old) up to 82 days of age. The results showed that the hyperthyroid state induced by a daily injection of 2.5 or 5 µg L-thyroxine resulted in acceleration of growth, a comparative increase in size and number of spermatogenic and interstitial cells, an increase in the STH cells, particularly at the earlier age (42 days old), and in a decrease in the number and size of TSH cells. Gonadotrophic FSH and LH and prolactin cells exhibited an increase in their granular content. The hypothyroid state induced by thyroidectomy or thiourea feeding, at the levels of 0.1 and 0.2%, resulted in the depression of growth rate, destructive changes of the spermatogenic and interstitial cells and also in the lumen of the seminiferous tubules. A decrease in the STH, gonadotrophic FSH and LH and prolactin cells and hypertrophy of TSH cells accompanied by degranulation were also observed.

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Section: Body Weightsupporting

confidence: 66%

Pituitary-testicular function changes in hypo-and hyperthyroid male rats

Amin¹,

Elsheikh²

1977

Cells Tissues Organs

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“…It is postulated that reduction in thyroid function is due to a relative iodine deficiency resulting from the large losses of iodine in milk which may be a limiting factor in the maintenance of lactation. The reduction in prolactin production in the absence of adequate T4 (Chen & Meites, 1969;Matsuzaki, 1970) may partly explain why lactation can be enhanced by the administration of thyroactive substances in ruminants (Blaxter, Reineke, Crampton & Peterson, 1949). Two objectives of the present study were to determine the effects of prolonged lactation on serum T4 and its relationship to lactational performance.…”

Section: Introductionmentioning

confidence: 99%

EFFECTS OF EXTENDED LACTATION AND 9α-Fluoroprednisolone ACETATE ON SERUM THYROXINE AND LACTATIONAL PERFORMANCE

Lorscheider¹,

Mears²

1973

Journal of Endocrinology

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The effects of extending lactation up to 48 days on serum thyroxine (T4), and its relationship to lactational performance, were studied with rats fed a ration containing 1\m=.\0 \g=m\gI\m=-\/g of feed. The effects of chronic administration of 9\g=a\-fluoroprednisolone acetate on serum T4 during prolonged lactation were also determined. Lactation was prolonged by substitution of foster litters at 8-day intervals. Serum T4 was measured by a competitive protei n\x=req-\ binding assay.Chronic administration of 9\g=a\-fluoroprednisolone acetate up to 32 days resulted in a significant increase in serum thyroxine in non-lactating rats. In saline-treated rats lactating up to 48 days, serum T4 was initially reduced by 30% at 16 days, but progressively increased as lactational performance (expressed as gain in weight of pups) decreased. This inverse correlation was attributed to a progressive decline in mammary gland competition for iodine and to a progressive depletion of corticosterone which may have exerted an antithyroid effect initially. Rats treated with 9\g=a\-fluoroprednisolone acetate and lactating up to 48 days, had serum T4 levels which were lower than values for corresponding saline-treated lactating rats, but were similar to those levels observed in saline-treated non-lactating rats. This may indicate a higher rate of thyroid hormone utilization in lactating rats treated with 9\g=a\-fluoroprednisolone acetate and may also explain the ability of these rats to maintain a better lactational performance than saline-treated lactating rats. Comparisons of each 8-day extended lactation period showed that in all cases lactational performance was greater for mothers treated with 9\g=a\-fluoroprednisoloneacetate; up to 113% more from 16 to 24 days lactation, up to 153% more from 24 to 32 days lactation, 146% more from 32 to 40 days lactation, and 317% more from 40 to 48 days lactation, despite the fact that by day 48 maternal body weight of lactating rats treated with 9\g=a\-fluoroprednisolone acetate was not different from that of saline-treated lactating rats. A hypothesis proposed for the hormonal maintenance of lactation suggests that the maintenance of euthyroid levels of serum T4 due to treatment with 9\g=a\-fluoroprednisolone

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“…De acordo com Blaxter et al (1949), Burroughs et al (1958), Miller et al (1974, Kennedy et al (1977), Schillo (1992), Owens e Goetsch (1993) e Bernal et al (1999), o hipotireoidismo reduziu o tempo de passagem dos alimentos pelo trato digestivo dos animais e aumentou a digestibilidade da matéria seca, colocando mais energia à disposição do organismo, em especial, por causa do aumento da presença do ácido propiônico no rúmen, aumentando também a docilidade dos animais. Além disso, o metabolismo corporal torna-se reduzido em animais hipotireóideos (Blaxter et al, 1949;Miller et al, 1974;Kennedy et al, 1977;Rumsey et al, 1990;Thrift et al, 1999a;Thrift et al, 1999b). Esses fatores citados favorecem a hipótese de maior ganho de peso nos animais hipotireóideos, mas não foi o que se observou no presente estudo, provavelmente por serem animais em crescimento e com bom potencial para ganho de peso, o que minimizou essas diferenças.…”

Section: Resultsunclassified

Efeito do hipotireoidismo induzido na resposta superovulatória em novilhas de corte mestiças

Bettini

Moraes²,

Rigolon

et al. 2006

Acta Sci. Anim. Sci.

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RESUMO. Estudou-se o efeito do hipotireoidismo induzido sobre a resposta ovariana à superovulação, à atividade do corpo lúteo e ao ganho de peso em novilhas de corte mestiças (½ Bos TaurosxBos Indicus). Nas análises estatísticas realizadas, não foi observada a influência dos tratamentos sobre a variação de peso (P>0,05). Os níveis de T 3 , T 4 e TSH foram, respectivamente, 1,31+0,77, 16,71+0,44 e 10,35+5,74 para o grupo tratado e 2,08+0,77, 57,46+0,44 e 2,08+5,74 para o controle (P<0,05). O número de embriões viáveis e de estruturas totais colhidas foi, respectivamente, de 2,52 e de 4,86 nos animais hipotireóideos e de 2,67 e 5,60 nos controles, não havendo diferença (P>0,05). Desse modo, concluiu-se que o hipotireoidismo não afetou a resposta superovulatória, a atividade do corpo lúteo e a variação de peso.Palavras-chave: embrião, ganho de peso, hipotireoidismo, novilhas, função reprodutiva.ABSTRACT. Induced hypothyroidism on the superovulatory response in crossbred beef heifers. This study was aimed at the effect of hypothyroidism induced on the ovarian superovulation response, corpus luteum activity, and the weight gain in crossbred heifers (½ Bos taurosxBos indicus). The data showed that the females weight remained the same (P>0.05) even after the treatment. The levels of T 3, T 4 e Tsh values were respectively 1.31+0.77, 16.71+0.44 and TSH 10.35+5.74 to treated animals, and 2.08+0.77, 57.46+0.44 , 2.08+5.74 to control group (P<0.05). There was no difference between them (P>0.05) considering the number of viable embryos and total number of structures 2.52 and 4.86 for the induced animals, and 2.67 and 5.60 for the control group respectively. Therefore, the results demonstrated that the hypothyroidism did not affect the superovulatory response, the corpus luteum activity, or the weight variation.Key words: embryo, weight gain, hypothyroidism, heifers, reproductive function. IntroduçãoExiste uma possível relação entre a atividade da tireóide e a atividade reprodutiva em vacas Brahman, durante o outono. Provavelmente, os padrões de sazonalidade da reprodução em Bos taurus indicus são mediados, parcialmente, por meio da atividade da tireóide e de suas relações indiretas com outros fatores, incluindo status nutricional e fotoperíodo (Moraes et al., 1998).As estações do ano e os meses dentro de cada estação apresentam grandes efeitos sobre a secreção dos hormônios da tireóide em vacas de leite (Mixner et al., 1962;Capuco et al., 2001;Pezzi et al., 2003). Essass mudanças, todavia, podem ser amenizadas em animais submetidos ao hipotireoidismo induzido (Dawson et al., 1985) e isso pode indicar um efeito direto dos hormônios da tireóide sobre a resposta ovariana às gonadotrofinas. A hipótese seria a de que o hipotireoidismo poderia melhorar a resposta ovariana à superovulação, aumentando a sensibilidade do ovário ao hormônio folículo estimulante (FSH). Stewart et al. (1994b) afirmaram que, em bovinos, os hormônios tireoideanos podem estar envolvidos com a secreção de gonadotrofinas. Não têm sido encontradas funções es...

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The Role of Thyroidal Materials and of Synthetic Goitrogens in Animal Production and an Appraisal of their Practical Use

Cited by 84 publications

References 0 publications

Pituitary-testicular function changes in hypo-and hyperthyroid male rats

Pituitary-testicular function changes in hypo-and hyperthyroid male rats

EFFECTS OF EXTENDED LACTATION AND 9α-Fluoroprednisolone ACETATE ON SERUM THYROXINE AND LACTATIONAL PERFORMANCE

Efeito do hipotireoidismo induzido na resposta superovulatória em novilhas de corte mestiças

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