Variations in plasma prolactin, thyroid hormones, gonadal steroids and growth hormone in turkeys during the induction of egg laying and moult by different photoperiods.

1. Concentrations of prolactin, growth hormone, testosterone, progesterone, thyroxine and triiodothyronine were measured in the blood plasma of female turkeys during successive periods of egg laying, a decline in lay, a moult induced by a short photoperiod (6 light: 18 dark) and a resumption of egg laying induced by a long photoperiod (16L:8D). 2. Concentrations of prolactin, growth hormone, testosterone and progesterone were higher in laying birds than in birds which were moulting or not laying. 3. The concentration of testosterone, but not of the other hormones studied, increased significantly during the period of profuse moult. 4. Concentrations of the thyroid hormones did not change with the varying physiological condition of the birds. However, the concentration of thyroxine was depressed by the long photoperiod.     

Skin blackening during the cooking of spent laying fowls

1. Blackening of the skin in factory processed cooked hens has been associated with elevated copper levels.

2. The degree of blackening was not directly related to copper content although the latter level was always higher than in control hens.

3. Simulated factory procedures, using scald water at 53 °C or 60 °C containing 50 mg Cu²⁺/1 and 50 mg C1₂/1, produced blackened skins of varying intensity on cooking.

4. It is suggested that the problem arose from a malfunction of the chlorination plant which produced excessive levels of chlorine and low pH, followed by erosion of copper from water pipes and subsequent interaction of copper and chlorine with the chicken skin.     

Some effects of feeding lathyrogens to laying fowls

The lathyrogen semicarbazide inhibited egg‐laying in fowls. The primary target of the drug appeared to be the pituitary gland. Ovulation and normal egg production were resumed soon after withdrawal. The eggs laid during administration appeared to be normal except that their shell membranes were heavier and less pigmented. Amino acid composition of the membranes from treated birds was normal, but they yielded more soluble hydroxyproline‐containing material when autoclaved for 5 h. Prolonged (20 h) autoclaving of membranes from both treated and control birds produced a soluble material very rich in hydroxyproline. Deprivation of dietary calcium did not influence the observed effects of semicarbazide. Plasma‐free hydroxyproline assays indicated that in laying birds semicarbazide produced labilisation of body collagen, but in pre‐laying birds it caused lack of appetite to the point of inanition.     

Plasma concentrations of corticosterone and thyroid hormones in laying fowls from different housing systems

Plasma concentrations of corticosterone, thyroxine (T4) and triiodothyronine (T3) were measured in representative mature female domestic fowls from three housing systems: cages, covered strawyard and range. There were no between-system differences for T4 but T3 was lower in birds from range than in those from cages. Corticosterone concentrations were lower in birds from strawyards than in those from range and cages. In the strawyards there were no differences in corticosterone concentrations between normal and low-ranking hens. The latter were selected on the basis that they remained apart from the flock, were under-weight, poorly feathered and unable to feed at will. Low-ranking hens had significantly higher plasma concentrations of T3 and T4 than normal birds. This was attributed mainly to the poor feather covering of most low-ranking birds. It was concluded that, in the assessment of different housing systems, plasma corticosterone and thyroid hormones were not useful measures of long-term stress or welfare. Different factors relevant to welfare may have contrary effects on the plasma concentrations of these hormones.     

Regulation of pulsatile LH secretion by ovarian steroids in the heifer

Two experiments were conducted to evaluate relationships among luteinizing hormone (LH), estradiol-17 beta (E2) and progesterone secretion during the preovulatory period in the heifer after prostaglandin F2 alpha (PGF2 alpha)-induced regression of the corpus luteum. A second objective was to elucidate the effects of E2 in regulating LH secretion. In Exp. 1, LH, E2 and progesterone concentrations were determined in serial samples collected during the preovulatory period after PGF2 alpha-induced luteal regression in five Red Angus X Hereford heifers. Progesterone declined to 1 ng/ml by 12 h after the second injection of PGF2 alpha. Frequency of LH pulses increased linearly (P less than .01), whereas no change in amplitude of LH pulses was detected before the preovulatory LH surge. This resulted in a linear increase (P less than .01) in mean LH concentrations. Estradiol also increased in a linear manner (P less than .01), and the rise in E2 was parallel to the increase in mean LH concentrations. In Exp. 2, 12 Angus X Hereford heifers were ovariectomized and administered either 13.5- or 27-cm silastic implants containing E2 at ovariectomy. Four heifers served as nonimplanted controls. Thirty-one days after ovariectomy all heifers were bled at 12-min intervals for 6 h. Frequency of LH pulses declined linearly (P less than .03) while mean LH (P less than .09) and pulse amplitude (P less than .01) increased linearly as E2 dose increased. These results indicate that a reduction in progesterone increases the frequency of LH pulses during the follicular phase of the estrous cycle in cattle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative histomorphological and ultrastructural study of the luminal epithelium of the isthmus in laying and moulting domestic fowls (Gallus domesticus)

This study describes ciliated, nonciliated and mitochondrial luminal epithelial cells of the isthmus in laying and moulting domestic fowls using histological and ultrastructural techniques. The ciliated cells were nonsecretory, while numerous electron‐dense secretory granules were present in the nonciliated cells of laying birds. Mitochondrial cells, occurring in two morphologically distinct forms, constituted the third type of epithelial cell present in the isthmus. The SEM study showed that the luminal epithelium was dominated by ciliated cells, the cilia of which partially obscured adjacent nonciliated cells. The involution of the luminal epithelium in moulting birds occurred via autophagy, apoptosis and necrosis. Autophagic inclusions, which included autophagosomes and autolysosomes, were present in the early degenerative phases of ciliated, nonciliated and mitochondrial cells. Nonciliated cells underwent degeneration via apoptosis, which was characterized by nuclear and cytoplasmic condensation. Apoptotic and necrotic ciliated cells were evident during the intermediate and advanced stages of regression. The presence of apoptotic cell death was confirmed using the TUNEL assay. Loss of cilia via the formation of cilia packets was observed using TEM and SEM. Necrotic cell death occurred in mitochondrial cells during the intermediate and late stages of degeneration. In conclusion, the findings of the study on isthmus involution in moulting birds suggest that autophagy is a process confined to the early stages of degeneration, while apoptosis and/or necrosis occur in the terminal stages of regression.     

Effects of sex and gonadal steroids on arginine vasotocin and mesotocin in the pineal gland and neurohypophysis of White Leghorn fowls

1. Pineal and neurohypophysial arginine vasotocin (AVT) and mesotocin (MT) were measured in White Leghorn hens, cockerels and castrated males treated with either testosterone propionate (TP) or oestradiol benzoate (EB) (n = 10/group). The lighting regimen was 14 h light: 10 h dark, supplied by natural diffused sunlight and incandescent bulbs. 2. Both AVT and MT were detected in the pineal gland of all the chickens. 3. There was no significant effect of either sex or treatments on pineal MT. 4. Females had about 4 times more pineal AVT than males, regardless of their treatment. There was no effect of the treatments on pineal AVT in the males. 5. No sexual difference in neurohypophysial AVT was detected, but the neurohypophysis of the castrated males treated with EB contained less AVT than the neurohypophysis of the intact males. 6. Intact males had about twice as much MT in the neurohypophysis as females. Castrated males treated with either TP or EB had similar concentrations of neurohypophysial MT, which were lower than that of the intact males, but higher than that of the females.     

Effect of metyrapone on the timing of oviposition and ovarian steroidogenesis in the laying hen

1. The purpose of this study was to observe the effects of metyrapone on the time of oviposition and LH-stimulated steroidogenesis by granulosa cells and small yellow follicles. 2. In experiment 1, White Leghorn hens were injected for 11 d with 240 mg metyrapone 5 h before 'lights off'. Control hens were injected with 1 ml of vehicle (PEG-400). Metyrapone treatment resulted in a 28% decrease in the rate of lay and the modal frequency of the time of oviposition was phase-shifted by 15 h. 3. In experiment 2, hens were injected with 240 mg metyrapone 5 h before 'lights off' or at 'lights on'. While metyrapone treatment reduced the rate of lay, a clear phase-shift in the distribution of oviposition was not observed. Basal and LH-stimulated progesterone synthesis by the granulosa cells of the largest follicle and oestradiol synthesis by small yellow follicles was significantly reduced. 4. Metyrapone treatment significantly reduced basal, but not LH-stimulated output of androstenedione by whole small yellow follicles compared to that observed in control hens. 5. The addition of metyrapone in vitro to isolated granulosa cells from the three largest preovulatory follicles inhibited LH-stimulated progesterone production in a dose-specific manner. 6. The results of this study suggest that the ability of metyrapone to perturb the open-period is a pharmacological effect mediated through inhibition of ovarian and adrenal steroidogenesis.     

The effect of ovarian steroids on the pharmacokinetics of Terguride in the rat uterus

The incorporation of 3H-17-beta oestradiol (3H-E2) and 3H-Tergurid (3H-Te) in the uteri of sexually immature rats was monitored for 16 hours following the treatment of the animals with Tergurid, a semisynthetic ergot alkaloid [chemically acid N-(D-6-methyl-8-isoergolin-I-yl)--N',N'-diethylurea maleate; VUFB-6638]. The differences in the incorporation of 3H-Te in relation to the presence of ovarial steroids (E2 and progesterone) were investigated for the same period of time in the adult ovariectomized rats. In all the time intervals under study, the average values of 3H-E2 activities in the uteri of juvenile rats treated with Tergurid were lower than in the controls. This decrease was statistically significant (P less than 0.05) eight hours after treatment. The time course of the incorporation of 3H-Te in the uteri of the experimental and control animals was about the same. The activities of incorporated 3H-Te in the uteri of adult rats treated with E2 were higher in all the intervals, the difference being statistically significant after two hours and 16 hours (P less than 0.05) and after four hours (P less than 0.01). Progesterone did not induce any significant differences in the incorporation of 3H-Te. These results suggest that the increased incorporation of Tergurid in the uteri of adult rats is due to a direct influence of E2. It has been demonstrated by trials on juvenile rats that Tergurid does not combine with oestrogenic receptors. As suggested by the decreased weights of the uteri of juvenile rats treated with Tergurid, the uterine cells are unable to react to exogenous administration of E2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sex steroids level in blood plasma and ovarian follicles of the chimeric chicken

The study was performed to determine the hormonal status of mature germline chimeras obtained by blastodermal cell transfer from chicken embryos of a donor breed [Green-legged Partridgelike breed (GP) x Araucana (AR)] to those of a recipient breed [White Leghorn (WL)] being at the same stage of embryonic development. The egg-laying chimeras and WL hens (control) of the same age were used in the experiment. At first, blood samples were taken from each bird at 0.5, 5, 12.5 and 18.5 h following oviposition. Subsequently, the chimeras and the WL hens were decapitated 1-2 h after ovulation. A stroma and the following follicles were isolated from the ovary: white normal (1-4, 4-6 and 6-8 mm), white atretic and yellow preovulatory follicles (F4-F1). Sex hormones, progesterone (P4), testosterone (T) and oestradiol (E2) in blood plasma and ovarian follicles were determined radioimmunologically. The activity of the 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the granulosa and theca layers of the follicles was analysed histochemically. In chimeric chickens, a higher level of T in blood plasma during the ovulatory cycle was noticed. However, in the stroma, white prehierarchical and medium-size preovulatory ovarian follicles the level of T was significantly lower. With respect to E2, its elevated levels were found both in blood and in the ovarian follicles. There were no significant differences in P4 concentrations in blood plasma while in ovarian follicles a higher level was observed only in white 6-8 mm follicles. 3beta-HSD activity in granulosa and theca layers of the ovarian follicles in chimeras was not different from that in the WL hens. In conclusion, the results obtained indicate that germline chimeras exhibit significant alterations in sex hormone levels in the ovary and blood plasma, which in turn may affect their reproductive abilities.     

Comparison of dietary hydrated copper sulphate,dietary zinc oxide and a direct method for inducing a moult in laying hens

1. The experiment lasted for seven 28‐d periods. Laying hens of two breeds were allocated to 10 treatments. For the first 28‐d period all birds were offered the control diet and then the following dietary treatments applied: a control group not moulted, one group moulted traditionally, 4 groups moulted using CuSO₄‐ and 4 using ZnO‐containing diets. After the moulting treatments the hens were offered the control diet for the remainder of period 2 and for a further five 28‐d periods.

2. The treatments applied during period 2 significantly reduced food intake, body weight, egg number, total egg weight and efficiency of food conversion. On returning to the control diet, there were no significant differences in cumulative food intake (periods 3 to 7). Body weight had returned to the same value as the control group by the end of period 3. Dietary treatments significantly reduced the efficiency of food utilisation during periods 3 to 7 and 1 to 7 inclusive.

3. For periods 1 to 7 inclusive the birds force‐moulted using CuSO₄ and ZnO gave on average greater egg numbers and total egg weights than those moulted traditionally.

4. The Haugh unit score was significantly improved after moulting. Egg Zn concentrations were increased by the 14‐d ZnO treatments.

5. The use of a diet containing CuSO₄ (2 g added Cu/kg for 7 d) was as effective as one containing ZnO (20 g added Zn/kg for 14 d) and both were superior to a traditional force‐moulting technique.

     

Role of loose feathers on the development of feather pecking in laying hens

1. The effect of the presence of loose feathers (on the floor) on the behaviour and plumage condition of laying hens (Lohmann Silver, LS) was studied during the rearing and laying periods. 2. From one day old, 60 birds in each of 4 straw-bedded pens (n = 240 in total) with 6.5 birds/m(2) were either kept under conventional rearing and management conditions (CT: control group with feathers on the floor; n = 120) or in pens from which the feathers were collected from the floor 4 times/week (FR: feathers removed; n = 120). Fifty birds from each of these 4 groups (n = 200 in total) were randomly selected at the age of 16 weeks and allocated to 4 identical pens in a poultry layer house (PH; with perches and 1/3 slatted floor) with access to an outside area (winter garden, WG) at a stocking density of 6 birds/m(2) in both PH and WG. 3. Observations on feather pecking and other behaviours (feeding, drinking, preening, standing, sitting, foraging, moving and dust bathing) were carried out at 8 ages: 6, 10, 15 (rearing period), 20, 25, 30, 35 and 40 weeks (laying period). Feather scoring was carried out at 15, 32 and 39 weeks of age. 4. There were no differences in feather pecking rates, forms (gentle, severe and aggressive pecks) as well as in the plumage condition between groups at the end of the rearing period. 5. Birds in the FR group exhibited lower rates and less severe feather pecking during the laying period. Accordingly, birds in the control group had worse feather condition at 32 and 39 weeks of age. Feather pecking rates within groups were, in general, greater in the afternoon compared to the morning periods. Birds in the control group were more active in walking. 6. Wings, rump, tail and back were the main targets for feather pecking. The majority of feather pecking occurred on the floor (66%) followed by feeding area (26%), perches (4%) and slats (4%). 7. Our results suggest that loose feathers on the floor may play an important role in the development and severity of feather pecking behaviour in laying hens and support the hypothesis (McKeegan and Savory, 1999) that feather pecking can be viewed as redirected foraging behaviour.     

Plasma concentrations of oxytocin,prostaglandin and ovarian steroids during spontaneous luteolysis in the cow

Fifteen, non-milking cyclic Holstein heifers and cows were used to study possible hormonal correlations during spontaneous luteal regression. Peripheral plasma samples were assayed for oxytocin, 13,14-dihydro-15-keto-prostaglandin F₂α (PGFM), estradiol-17β and progesterone. On day 9, when luteolysis does not normally occur, no significant elevation in oxytocin or PGFM values occurred in five cows sampled for 12 hr at 15 min intervals. A correlation did not exist (P>.05) between PGFM and oxytocin values nor between estradiol and oxytocin values at this time. Of 10 cows bled on day 18 or 19 for 12 hr at 15 min intervals or 34 hr at 1 hr intervals, five animals exhibited pulsatile elevations of PGFM and oxytocin. The elevations in plasma concentrations of these two hormones were coincident and significant correlation coefficients (P<.01) were calculated (range 0.62 to 0.85). No significant correlation was present in the remaining 5 cows. These results suggests that ovarian oxytocin is secreted concomitantly with uterine prostaglandin production at the time of spontaneous luteolysis in the cow.     

Bitter vetch as a single dietary ingredient for molt induction in laying hens

Molting is used to increase productivity in the second laying cycle of commercial laying flocks. We report here the applicability of whole grain of bitter vetch as an alternative method for molt induction in laying hens. A total of 120 laying hens were molted by feed withdrawal (FW), a high-Zn diet (HZn), a moderate-Zn and Ca-P-deficient diet (MZn-CaP), or whole grain of bitter vetch (BV). Egg production ceased first in FW-treated hens and last in MZn-CaP-treated hens (P < 0.05). The rest period was longer (P < 0.05) in hens exposed to the BV diet, which proved to be comparable with the FW treatment for postmolt egg production. Egg mass for 4 to 16 wk after the molting was greater (P < 0.05) for hens molted by BV than hens molted by the MZn-CaP diet. Egg weight and yolk color were not (P > 0.05) significantly different among various molting induction methods. Albumen height and Haugh unit of eggs from hens molted by BV, for the most part of the experimental period, were significantly (P < 0.05) greater than for birds on the MZn-CaP diet and unmolted hens. In conclusion, use of BV grain as a single dietary ingredient proved to be effective in molt induction and improving postmolt egg production and internal egg quality when compared with unmolted hens.     

Kisspeptin-10对蛋鹌鹑卵巢发育与内分泌的影响

为研究Kisspeptin-10(Kp-10)对禽类生殖内分泌的影响,将75羽22日龄雌鹌鹑随机分为3组,分别腹腔注射300μL生理盐水(对照组),注射0.1 nmol Kp-10(低剂量组)和1 nmol Kp-10(高剂量组),每日注射1次,连续注射3周。记录鹌鹑开产情况,并于60日龄时采集血液和卵泡组织,测定生殖激素与受体的mRNA表达。结果:与对照组相比,注射Kp-10组鹌鹑产蛋率显著提高,且大卵泡数显著增加,血液中雌激素水平显著升高;低剂量组输卵管重显著增加,但体重、肝脏重和小卵泡重无显著变化。Real-time PCR结果显示,Kp-10处理显著下调小卵泡及F1级卵泡上促黄体激素受体(LHR)、促卵泡激素受体(FSHR)和促性腺激素释放激素Ⅰ(GnRH-Ⅰ)的基因表达。