Comb Growth Research Articles

Precocious puberty in tamoxifen‐treated cockerels: Hypothalamic gonadotrophin‐releasing hormone‐I and plasma luteinising hormone, prolactin, growth hormone and testosterone

1. The administration of the anti-oestrogen, tamoxifen (TAM) to juvenile chicks results in precocious puberty. In the present study the effects of TAM administration (1 mg/kg body weight on alternate days from 12 d of age) on testicular function, hypothalamic chicken gonadotropin-releasing hormone (cGn-RH-I), plasma luteinising hormone (LH), growth hormone (GH), prolactin (PRL) and testosterone were studied in juvenile White Leghorn cockerels. 2. The increase in hypothalamic GnRH-I content which occurs during sexual development was advanced in TAM-treated birds, in association with precocious testicular development, an early rise of plasma testosterone content and enhanced comb growth. 3. Plasma LH concentrations behaved similarly and were higher in the TAM-treated than in control birds, during most of the experimental period. Plasma PRL concentration, which is high at hatching, decreased more quickly in TAM-treated than in control birds; plasma GH values were not consistently affected by TAM treatment. 4. Both the growth and the involution of the bursa of Fabricius in the TAM-treated cockerels preceded that in the control chicks. 5. It is concluded that TAM treatment induces precocious puberty in the cockerel by blocking the negative feedback action of aromatised testicular androgens on the hypothalamus.

The Effect of Testosterone Propionate on Growth of Broiler Chickens

The effects of testosterone propionate (TP) on body weight, tissue percentages of body weight, serum IgM, and rectal temperature (2 h postinjection) of male and female broiler chickens were investigated at 28 and 48 days posthatching. Testosterone propionate was dissolved in sesame oil and was injected at 2 mg/kg of body weight every other day, and controls were treated with sesame oil at similar volume, starting Day 7 posthatching. Administration of TP reduced (P < .05) body weight and percentages of liver, testes, and bursa of Fabricius at 28 and 48 days of age. At 28 and 48 days of age, muscle percentage and comb growth of TP-treated birds increased (P < .05) but ovarian weight was unaffected. Concentrations of IgM in serum of TP-injected birds was unchanged at Day 28, but increased (P < .05) at Day 48. Testosterone propionate did not affect percentages of bone or abdominal fat in either sex. Rectal temperature was depressed (P < .05) by TP treatment in both sexes at both ages.

Tamoxifen advances puberty in the White Leghorn hen.

1. Tamoxifen (TAM) administration advances puberty in cockerels. In the present study the effect of TAM administration on the sexual development of White Leghorn hens was studied. 2. Two-week-old White Leghorn females were injected intramuscularly with TAM on alternate days at doses of 0.1 mg (0.1 TM), 1 mg (1TM), 5 mg (5TM) and 10 mg/kg body weight (10TM) respectively, while the controls were injected with maize oil (vehicle). The experiment was terminated at 23 weeks of age, when all the control hens laid eggs. Sample autopsies were made on chicks of 6, 14 and 23 weeks of age. 3. Body growth was not affected by any of the treatments. 4. Comb growth was accelerated by all doses of TAM, while hematocrit increased in the 1TM, 5TM and 10TM hens. 5. Egg laying advanced in the 0.1TM and 1TM birds, was delayed in 5TM hens and did not occur at all in the 10TM females. 6. TAM caused a precocious increase in plasma oestrogen and androgen, suppressed adiposity in a dose-related manner and, at low doses, advanced the development of the gonadal system. 7. At 23 weeks of age, when the gonadal system of the controls was fully active, TAM caused a dose-related depression in abdominal fat, liver, ovary, and oviduct weights, plasma total lipids and calcium concentrations and a dose-related increase in plasma oestrogen and androgen titres, and comb weight. 8. It seems that TAM increased gonadotropic activity and its androgen stimulating action, but suppressed peripheral signs of the elevated plasma oestrogen titres. Low doses of TAM enhanced gonadotropic activity and egg laying but the antioestrogenic effect depressed development of the gonadal system, suppressing egg production when high doses were administered. It therefore seems that oestrogens are necessary for normal ovarian development in hens.

Plasma concentrations of luteinising hormone and body weights during somatic maturation in intact and castrated Australorp cockerels from a line of hens selected for increased ovulation rate

1. Plasma concentrations of luteinising hormone (LH), comb size and body weight were measured between 46 and 208 d of age in intact and castrated cockerels from lines of selected and control Australorp domestic chickens. The selected line had been selected for increased rate of lay by reducing oviposition intervals within sequences. The cockerels were reared and maintained on 15.25 h light/d. 2. Concentrations of plasma LH in the intact control cockerels were low in the 'immature' phase (less than 100 d old) and increased during the 'mature' phase (older than 175 d) with a peak occurring when the testes are beginning to grow at the onset of the 'mature' phase. In comparison with the control line of cockerels, the selected line had significantly higher plasma LH concentrations at the onset of the 'mature' phase. Selection had no effect on the mean concentration of plasma LH in either the immature phase or a few weeks after the onset of the mature phase. 3. There was no effect of selection in sibling females for higher rates of lay on changes in comb size or body weight during sexual maturation in the intact cockerels. 4. Castration at 45-46 d of age resulted in increased plasma LH concentrations and no comb growth. Plasma LH concentration increased progressively between 40-208 d. There was no difference between the two lines of cockerels in plasma LH concentration or rate of body growth after castration. 5. It is concluded that selection of females for a change in the rate of egg production has resulted in increased plasma LH concentrations in sibling males around the onset of sexual maturation. Selection appears to have caused this effect by altering an unidentified component of the inhibitory feedback mechanism which controls the tonic secretion of LH.

Mathematical model of building behavior of Apis mellifera

Following experimental observations on the building techniques of Apis mellifera , a model describing the construction of parallel combs in beehive is proposed. The model assumes as the essential elements in building activities the bee-wax and bee-bee interactions coupled by means of a feedback mechanism. The construction is represented by a set of dynamical non-linear partial differential equations for the density of bees and the quantity of wax distributed in the hive. Using linear stability analysis the conditions for growth of the coherent spatially ordered inhomogeneous structure are derived. Numerical simulations depicting growth process in the nonlinear regime have been performed, illuminating the role of the competition between bees and the bee-wax interaction. The model reproduces the beginning of the growth of parallel and equidistant combs satisfactorily.

Genetic and morphological studies on the right gonad of ovariectomized chickens.

The present study was conducted to cause sex-reversal in chickens whose genetic sex has been confirmed by the modern karyotyping techniques. The sex-reversed chickens induced by ovariectomy, were classified into three categories on the basis of secondary sex characteristics. Two chickens were classified as High degree of masculinity, eleven as Middle degree and fourteen as Low degree of masculinity. When the left ovary was removed, the right gonad began to develop. Though there was gonadal variation in structure, they were also classified into three categories; two classified as testicular gonad, thirteen as ovo-testis and twelve as ovary-like gonad. The degree of masculinity as determined from the secondary sex characteristics, especially comb growth which was almost commensurate with the masculinization of the right gonad.

The effect of tamoxifen on the reproductive traits in white Leghorn cockerels

Fifty White Leghorn male chicks were divided into five equal groups of ten chicks each. Beginning at two weeks of age they were injected on each alternate day as follows: corn oil as a vehicle control or 0.5, 1.0, 5.0, or 10.0 mg tamoxifen/kg/b.wt. The whole experimental period lasted until twelve weeks of age. The two lowest doses of tamoxifen (TAM) enhanced comb growth, while the highest dose suppressed it. The two lowest doses of TAM also caused an earlier increase in sexual activity of the chicks, and precocious production of semen. At nine weeks of age the 0.5 and 1.0 mg doses of TAM increased plasma testosterone to a level three times higher than in the controls. This effect was not observed with the highest dose of TAM. At 12 weeks of age the chicks treated with 1 mg TAM had larger testes than the controls and produced three times more sperm per ejaculation. At this stage chicks treated with the highest dose of tamoxifen produced less sperm than the control and had smaller testes and adenohyphyses.

Parasagittal hypothalamic knife cuts in male chicks: advancement of reproductive function and changes in plasma concentrations of luteinising hormone and androgen.

Advancement of reproductive function occurred in male domestic chicks after lateral hypothalamic deafferentation (bilateral knife cuts extending from the preoptic to the mamillary region) at 2 weeks of age. Five out of 24 chicks showed sexual precocity as shown by accelerated comb growth after surgery. The 5 chicks had significantly higher concentrations of plasma luteinising hormone (LH) and androgen (A) than 5 sham-operated controls. Maximum concentrations of plasma LH and A were observed 3 and 4 weeks respectively after surgery. It is concluded that in the male domestic chick gonadotropin secretion is inhibited by extrahypothalamic influences.

The development of photorefractoriness in willow ptarmigan ( Lagopus lagopus lagopus) after the suppression of photoinduced LH release with implants of testosterone

Photosensitive willow ptarmigan, held on short days (6L, 18D), were implanted with Silastic capsules containing testosterone propionate and after 4 weeks were transferred to continuous light. The implants were removed from one group of birds at the onset of photostimulation and from further groups at 4, 10, and 16 weeks following photostimulation. When the implants were removed at the onset of and 4 weeks following photostimulation, LH secretion was stimulated and the growth of supraorbital combs continued. LH levels subsequently declined and returned to baseline values 8 weeks after the implants had been removed: this fall in LH was followed by a regression of the supraorbital combs. In contrast, LH secretion remained low and the supraorbital combs began to regress immediately following the removal of testosterone implants after 10 and 16 weeks of photostimulation. These results suggest that photorefractoriness develops in willow ptarmigan as a consequence of prolonged exposure to long days per se rather than as a consequence of a preceding period of photoinduced gonadotrophin secretion. We therefore conclude that photorefractoriness is unlikely to be caused by some form of “exhaustion” of the hypothalamo-hypophyseal unit.

The Effect of Permanent Short Days and Castration on Plumage and Comb Growth in Male Willow Ptarmigan (Lagopus lagopus)

The Effect of Permanent Short Days and Castration on Plumage and Comb Growth in Male Willow Ptarmigan (Lagopus lagopus)

Testosterone metabolism and sexual behavior in the chick

A series of experiments was performed to study the behavioral and physiological activity of testosterone (T) metabolites which are produced by neural tissues of male chicks, i.e., mainly 5α- and 5β-dihydrotestosterone (5α-, 5β-DHT), 5α- and 5β-androstan-3α, 17β-diol (5α-,5β-diol), and 4-androstene-3,17-dione (Δ4). It was found that 5β-reduced androgens alone or in combination with estradiol stimulate juvenile copulation in the chick while they have no detectable effect on all somatic variables which are recorded (testicular weight, plasma LH) with the exception of comb size. On the contrary, comb size was increased by T, Δ4, 5α-DHT, and 5α-diol while testis growth was prevented by T and Δ4 only. There is a good correlation between the anatomical localization of the enzymatic activities which metabolize T and the hormonal dependence of the biological responses: The comb converts T into 5α-reduced compounds which affect comb growth. 5β-Reduction is high in the hypothalamus, a fact which can be related to the sensitivity of sexual behavior to 5β-reduced androgens. This suggests that T metabolism is a very important step in the expression of this hormone's physiological effects.

Hormonal Activity in Poultry Excreta Processed for Livestock Feed

Experiments were conducted to determine the kind and amount of endogenous hormonal activity present in various sources of poultry excreta processed for use as livestock feed. These experiments were conducted to determine: 1) the presence of both androgenic and estrogenic activity in poultry excreta; 2) the amount of activity found; and 3) the effect of processing methods, such as dehydration, upon the level of hormonal activity. Experiments in which chick comb growth was bioassayed showed that caged laying hen excreta processed by house fly larvae contained androgenic activity that ranged from 2.18 to 9.36 μg. of testosterone equivalents per gram of dried excreta. This activity was not present in fresh excreta and was not affected by drying times or temperatures up to 48 hr. at 100°C. In rat uterine growth assays, fresh, dried caged laying hen excreta contained up to 1.6 μg. of estradiol equivalents per gram of dried excreta. Holding excreta for 5 to 7 days under wither aerobic or anaerobic conditions reduced estrogenic activity, but drying temperatures up to 100° C. did not appear to affect the level of these hormones in excreta.

Identifying lympholytic and androgenic effects of androgenic steroids

Is the lympholytic effect of androgenic steroids separate from the androgenic effect? To answer this question we compared testosterone propionate, a steroid known to cause bursa regression and stimulate comb growth in baby chicks, with two androgenic compounds, Wy 6343 and Wy 4355, possessing a high anabolic/androgenic ratio and a third androgen, androstendiol, which had been reported previously to be without significant influence on bursa growth. Our results revealed that androgenic steroids may be lympholytic without exhibiting androgenic activity. However, the androgenic effect appears to enhance the lympholytic and immunosuppressive parameters of the steroid.

Suppression of precocial copulation by progesterone implants in the male chick forebrain.

Precocial copulation in 2-wk.-old male chicks, described behaviorally as free mount, tread, posterior contact, waggle, peek, and seize, was developed through hand-training experience and androgen treatment. Crystalline progesterone was then implanted in various forebrain or midbrain regions. Results indicated that progesterone inhibited copulatory behavior when placed in the periventricular areas of the preoptic-hypothalamic continuum. Progesterone implants in the preoptic lateral forebrain bundle regions also suppressed precocial copulation. Forebrain implants of cholesterol did not result in copulatory inhibition. The suppression of copulatory behavior was not accompanied by loss of weight or deficits in general activity or comb growth. These data indicate that brain regions responsible for progesterone-induced copulatory inhibition are similar in neuroanatomical distribution to those involved in testosterone-induced copulatory activation.

Effect of thyroid extract combined with theophylline on comb growth in chickens

Effect of thyroid extract combined with theophylline on comb growth in chickens

Age-dependent effects of 5-methoxytryptophol and melatonin on testes and comb growth of the white leghorn (Gallus domesticus L.).

Testes weights of white leghorns of the same age or of equal body weight vary considerably. Experiments on the effects of pinealectomy, administration of pineal extracts or indolic compounds on the testes weights therefore require better parameters. Cockerels having a similar initial comb size prove to have testes of similar weights. Experiments using this parameter permit a more exact comparison of control and experimental animals.

The Effect of Clomiphene Citrate in Chickens: 1. Androgenic and Estrogenic Activity

INTRODUCTIONCLOMIPHENE citrate is a synthetic, non-steroidal compound (Palopoli et al., 1961) which has been found useful as an ovulation inducing agent in anovulatory and oligo-ovulatory women (Greenblatt and Mahesh, 1970). The compound consists of a mixture of cis and trans isomers (Fig. 1).Clomiphene has been reported to possess no androgenic or anti-androgenic activity but does exhibit estrogenic as well as anti-estrogenic activity in laboratory animals (Holtkamp et al., 1966).The work reported herein was undertaken to determine if clomiphene, cisclomiphene or transclomiphene are androgenic, anti-androgenic, estrogenic or anti-estrogenic in chickens.MATERIALS AND METHODSA. Androgenic activity. The androgenic and anti-androgenic activities of clomiphene, cisclomiphene and transclomiphene were studied using chick comb growth and capon comb growth as indicators.Three chick comb assays were conducted using day-old Single Comb White Leghorn male chicks. The drugs were dissolved in dimethylsulfoxide and were applied in a volume of .01 ml. directly…

Effect of Oral Administration of Methallibure (I.C.I. 33, 828) in Growing Cockerels

Effect of oral administration of Methallibure (I.C.I. 33, 828) upon body weight, feed intake, comb growth and testicular development in 4-18 weeks old cockerels were examined at the two dosages, 0.0015% (E1) and 0.003% (E2).(1) Body weight was suppressed by the administration of this drug. This suppression in body weight gain should be ascribed to reduced appetite in the treated birds, since firstly no difference was observed between E2 and an appropriate control group (C2) which was not treated but received the same amount of feed consumed one day before by E2 group, and secondly there was no difference between two treated groups with difference levels of administration. Appetite was strongly suppressed in the first week after the normal ration was changed to the experimental one, and thenafter, it returned to the normal level proportionally to their body weight gain.(2) Testicular weight in the treated group was smaller than in the control. This was more evident at the 10th week of age than at the 19th week. Spermatogenesis was somewhat inhibited by the drug but almost normal in sperm formation by the age of 19 weeks. It was suggested that the levels of administration used in this study were not sufficient to inhibit their gonadal activity as the cockerels approached to their full maturation.(3) Comb weight in 0, 003% methallibure administred cockerels was significantly smaller than the controls, which suggests that androgen secretion was inhibited markedly in the treated group. The activity of thyroid was accelerated in the treated group. Other organs such as liver, spleen, pancreas and kidney were not affected much but adrenal was smaller in the treated groups.(4) Water content in feces of treated groups was 6 to 12% higher than in the control.(5) Both fertility and hatchability by the use of those treated cockerels after 22 weeks were not affected at all. This suggests that the effect of the drug may not persist for a long period after withdrawal of the agent.

Effect of hypophysectomy of young cockerels, with particular reference to body growth, liver weight, and liver glycogen level

Several end-points were examined after hypophysectomy of cockerels at approximately 3 weeks of age. The final body weight and combined length of the shank and middle toe of hypophysectomized cockerels in preliminary experiments (Series 1) were 58 to 88% and 70 to 82%, respectively, of the control values at 3 to 8 weeks after pituitary removal. In later experiments (Series 2), the increases in body weight and shank-toe length of hypophysectomized cockerels were about 75 and 50%, respectively, of the control values during a 12-day period after operation when hypophysectomized cockerels consumed 22–23% less food ad libitum. When hypophysectomized cockerels were force-fed enough food to cause the same or greater body weight gains as controls fed ad libitum, there was still a considerable reduction in bone growth. Growth was observed in one experiment during two consecutive 12-day periods after removal of the pituitary. Hypophysectomy resulted in a 17% lesser body weight gain and a 32% lesser shank-toe increase than controls during the first 12-day period but the bone growth of hypophysectomized cockerels during the 13–24-day period was considerably less than during the 1–12-day period. Thyroxine stimulated bone growth of hypophysectomized cockerels during the first 12-day period to such a degree that the shank-toe increase was not different from intact controls but had a much lesser effect during the second 12-day period. The liver weights (as percentage of the body weight) of controls and hypophysectomized cockerels fed ad libitum were the same at 12 days after hypophysectomy, while the liver glycogen levels were more than doubled in the pituitaryless birds. Hypophysectomized cockerels force-fed enough food to cause the same or greater body weight gains as controls fed ad libitum had liver weights 55–56% greater than ad libitum controls and liver glycogen levels as much as 4.5 times the controls. Gonad weight, thyroid weight, and comb growth were all drastically less for hypophysectomized cockerels than for controls.

Response of Testis and Comb of the Radiothyroidectomized Chick to PMS

THE purpose of this experiment was to learn if pregnant mare serum (PMS) could stimulate gonad and comb growth in the chick in the absence of thyroid hormone. Breneman (1945) and Dorfman et al. (1948) adequately demonstrated that, in the normal chick, PMS caused both testis growth and comb enlargement.Snedecor and Camyre (1966) showed that five-week-old chicks which had been radiothyroidectomized (RTx) at age six days had greatly reduced testis and comb weights. This corroborated the results of Payne (1944) and Morris (1951) with surgically thyroidectomized chicks. Like Morris (1951), Snedecor and Camyre (1966) noted a synergistic effect of thyroid hormone and androgen on the comb in hormone replacement studies in thyroidectomized castrates. Either hormone was able to promote but limited comb growth in the absence of the other. From the results following RTx, however, it was not possible to know whether the reduction of testis size was due .