Limestone particle size fed to pullets influences subsequent bone integrity of hens.

This study was conducted to evaluate limestone particle size (LPS) in 2 strains of laying hens housed in conventional cages or aviaries on bone integrity. Lohmann Brown and Bovan White pullet chicks were started in equal numbers on the floor or in battery brooders and were intermingled throughout all subsequent housing systems. At 5 wk of age, 432 floor-raised pullets were moved to 8 aviary cages. At 10 wk, 256 battery-raised pullets were transferred to 64 conventional layer cages. Pullets were given diets containing fine (LPS-FINE, 0.431 mm) or a blend of fine and coarse (LPS-BLEND, 0.879 mm) LPS from 7 to 17 weeks. Data were analyzed as a split plot factorial design with strain as subplot and with 4 replicates for each treatment combination. Body weight, feed intake, egg production, and eggshell breaking strength and percentage were measured. Tibia bone mineral density (BMD) was determined using a dual energy x-ray absorptiometry. Presence of keel indentations, curvatures, or fractures was recorded. LPS-BLEND increased BMD (0.215 vs. 0.208, P = 0.03) at 18 weeks. During the pullet phase, the odds of pullets fed LPS-FINE displaying keel curvatures were 2.8 times the odds of those fed LPS-BLEND (P = 0.04). At 54 wk, hens fed LPS-BLEND as pullets had lower odds of keel indentations (P = 0.02). Brown aviary hens fed LPS-BLEND as pullets had the lowest egg production compared to the rest of the treatment combinations (P = 0.004). Taken together, feeding LPS-BLEND to pullets improved bone mineralization at the onset of sexual maturity and reduced keel damage during the pullet and layer phases, regardless of strain; however, LPS-BLEND was associated with lower egg production in Brown hens housed in aviaries compared to all others.

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.

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.

Physiological changes to transient exposure to heat stress observed in laying hens.

Hy-Line W-36, W-98, and Brown hens lay approximately the same number of eggs/hen housed to 80 wk; however, little is known about differences in performance during heat stress (HS). Two experiments were performed. The first experiment evaluated intestinal calcium uptake (CaT), heat shock protein-70 (HSP70) liver expression, and endocrine status in the 3 strains under heat stress in response to 1 h of transient exposure to high temperature before onset of 18 h of HS. The second experiment evaluated the differences between W-36 and W-98 in acid-base status observed at 2 different ambient temperatures. The HSP70 and CaT data were analyzed as a completely randomized design (CRD) using a 3 x 2 factorial with strain as a 1 factor and preexposed and control treatments as the other. Estrogen and progesterone data were analyzed as a CRD using repeated measures in a 3 x 2 x 2 factorial with strain as a the first factor, preexposure and control treatments as the second factor, and phase of blood collection as the third factor. The data of the second experiment were analyzed as a CRD using repeated measures in a 2 x 2 x 2 factorial with strain, temperature, and phase of blood collection as the factors. The method applied in both experiments was based on the mixed model (SAS). The results show a strain effect, with the higher CaT in the W-36. The results indicated that transient exposure to HS did not induce changes in HSP70 liver expression. In the second experiment, the blood gas values did not differ between strains, except for the partial pressure of CO(2), in which the values at 22 degrees C are higher for the W-36. At 38 degrees C, there was an increase in blood pH and a reduction in HCO(3)(-) in both strains. The results indicate that endocrine, acid-base status, and Ca homeostasis represent important factors to be considered in assessing genetic differences for thermotolerance.

Activity of three-beta-hydroxysteroid dehydrogenase in granulosa cells treated in vitro with luteinizing hormone, follicle-stimulating hormone, prolactin, or a combination.

Three-beta-hydroxysteroid dehydrogenase (3beta-HSD) is a key enzyme in the pathway that produces progesterone. Hy-Line hens (W36, W98, and Brown) were subjected to mild heat stress [36 degrees C for 24 h (acute heat stress, AHS) or 2 wk (chronic heat stress, CHS)] or maintained at 22 degrees C (thermoneutral, TN). Granulosa cells (GC) from the 3 largest follicles were isolated, dispersed, and incubated with luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), a combination, or no hormone (control), and then with pregnenolone nitro blue tetrazolium to determine 3beta-HSD activity. Treatment by LH (TN, P = 0.04; AHS, CHS, P < 0.0001) and by LH+FSH (TN, AHS, CHS, P < 0.0001) resulted in increased enzyme activity compared with the respective controls. In TN and CHS, LH+FSH increased the activity to a greater extent than LH alone (TN, P = 0.02; CHS, P = 0.0004); in AHS the increase was not significant (P = 0.29). Treatment with FSH, PRL, or LH+PRL decreased (TN, AHS) or had no effect (CHS) on 3beta-HSD activity. In TN and AHS cells, FSH and PRL reduced enzyme activity (P = 0.006 and 0.0580, respectively). When LH was added to PRL, suppression by PRL was mitigated somewhat. When LH and FSH were added to PRL, 3beta-HSD activity in AHS and CHS cells actually increased compared with the respective controls (P = 0.052 and 0.003) but remained below the activity of cells incubated with LH+FSH or LH alone. This suggests that gonadotropic actions of LH and LH+FSH are countered by the antigonadotropic action of PRL and, conversely, that PRL reduces the stimulatory action of LH and FSH. Strain differences in GC response to hormones were observed primarily in the CHS-treated birds; generally, W98 was highest; Browns showed the weakest response, and W36 was intermediate. In earlier studies, HS reduced circulating LH and GC progesterone and 3beta-HSD activity in vitro and increased circulating PRL. The results suggest a mechanism by which reduced activity of 3beta-HSD and progesterone by GC during HS might be explained, particularly with the differences in strains observed.

Exogenous estrogen boosts circulating estradiol concentrations and calcium uptake by duodenal tissue in heat-stressed hens.

In the hen, heat stress (HS) disrupts shell calcification and reproductive processes, including hormone synthesis and egg production. Two studies were conducted to investigate palliative effects of exogenous estrogen or dietary vitamin D3 on Ca homeostasis and reproductive physiology during HS. Study 1: Hy-Line W36 hens were randomly assigned to thermoneutral (TN) or HS treatments and to 1 of 7 estrogen treatments: zero (control) or one Compudose 200 implant given 1, 2, 3, 8, 9, or 10 d before onset of HS. With no implant, HS reduced plasma estradiol (E2) and total Ca absorbed (CaT) by duodenal cells (P < 0.05). In TN hens with implants, plasma E2 tripled within 24 h (P < 0.05) and remained elevated (P < 0.05) through d 9. In HS hens with implants, plasma E2 rose 6-fold (P < 0.05) to equal TN+E2 concentrations and remained elevated through d 10. In TN and HS hens with implants, the rate of Ca absorption (CaTR) and CaT increased dramatically; the responses were quadratic and essentially identical. Study 2: Hy-Line W36 hens were provided diets formulated either according to NRC requirements (NRC, 1994), or with the addition of 22,000 IU/kg vitamin D3 (+VD hens). A 24-h HS episode was imposed 2 wk after initiation of the dietary regimen. Duodenal samples were collected for Ca absorption assays after the 24-h HS episode. Both CaTR and CaT in +VD hens were approximately 3-fold higher than in hens in the NVD group (P = 0.102). The results lead to the conclusion that exogenous estrogen, high levels of dietary vitamin D, or both, before a HS episode, are efficacious in alleviating at least some of the effects of HS and should be further investigated.

Role of estrogen in avian osteoporosis.

One of the difficulties associated with commercial layer production is the development of osteoporosis in hens late in the production cycle. In light of this fact and because of hens' unique requirements for Ca, many studies have focused on the regulation of Ca and the role of estrogen in this process. The time course of estrogen synthesis over the productive life of hens has been well documented; increased circulating estrogen accompanies the onset of sexual maturity while decreases signal a decline in egg production prior to a molt. Numbers of estrogen receptors decrease with age in numerous tissues. The parallel changes in calcium-regulating proteins, primarily Calbindin D28K, and in the ability of duodenal cells to transport Ca, are thought to occur as a result of the changes in estrogen, and are also reversible by the molt process. In addition to the traditional model of estrogen action, evidence now exists for a possible nongenomic action of estrogen via membrane-bound receptors, demonstrated by extremely rapid surges of ionized Ca in chicken granulosa cells in response to 17beta-estradiol. Estrogen receptors have also been discovered in duodenal tissue, and tamoxifen, which binds to the estrogen receptor, has been shown to cause a rapid increase in Ca transport in the duodenum. In addition, recent evidence also suggests that mineralization of bone per se may not explain entirely the etiology of osteoporosis in the hen but that changes in the collagen matrix may contribute through decreases in bone elasticity. Taken together, these studies suggest that changes in estrogen synthesis and estrogen receptor populations may underlie the age-related changes in avian bone. As with postmenopausal women, dietary Ca and vitamin D are of limited benefit as remedies for osteoporosis in the hen.

Western immunoblotting in avian shell gland sample immunoblotting methods.

Avian shell gland tissue was subjected to Western blot analysis using anti-human estrogen receptor-alpha antibody H222. Initial attempts to obtain consistent, high-quality blots were unsuccessful because, as it turned out, excessive lipid in tissue preparations interfered with protein separation. Incremental additions of acetone eventually proved to be the critical step in solubilizing lipids and allowing consistent separation of bands on gels. A detailed description of the methodology is presented.

Estrogen receptor-alpha populations change with age in commercial laying hens.

Older hens in production lay larger but fewer eggs than younger birds, and the incidence of soft and broken shells is greater in older hens than younger. These changes are attributable at least in part to changing hormone profiles and diminished ability of the hen to transport calcium at the duodenum. In further exploration of this relationship, a study was conducted with three ages of Hy-Line W-36 birds: prelay pullets (PL; 19 wk, 0% production), peak-production hens (PP; 29 wk, approximately 93% production), and late-stage hens (LS; 71 wk, approximately 80% production). Hens from the PP and LS groups were palpated for presence of an egg in the shell gland; hens were then euthanized and tissues (kidney, shell gland, hypothalamus) were removed for quantification of estrogen receptor-alpha (ERalpha) populations via immunocytochemical and Western blot analyses. Localization of ERalpha by immunostaining in the shell gland showed differences among age groups; however, no differences were noted in localization of ERalpha between age groups in the kidney and hypothalamus. In both the kidney and the shell gland there was a decrease in the amount of ERalpha, as detected by immunoblotting, in the LS hens compared to PL and PP birds (P < 0.05). The results suggest that failure of calcium regulating mechanisms with age may be mediated at least in part through the reduced populations of estrogen receptors in certain critical tissues.

Value-added animal agriculture: inclusion of race and gender in the professional formula.

The Morrill Act establishing the land grant university system created public higher education institutions and paved the way for women and racial minorities to access them. Today women are -50% of the undergraduate population in animal science (AS) departments at the original land grant state universities, but racial minorities lag far behind, in part because the schools created under the 1890 legislation provided a diversion away from the state universities. Demographic trends from the U.S. Census and the Bureau of Labor Statistics indicate increasing positive growth in nonwhite workforce participation, with concurrent decreases in non-Hispanic male participation; men and women will be nearly equally represented by early in the 21st Century. In the faculties of AS departments, both women and minorities are seriously under-represented; causative factors underlying this phenomenon are similar. Although, historically, adherence to role stereotypes and divisions of labor explain some of the under-representation, these assumptions do not hold across all economic classes. Other factors contributing to the scarcity of women and faculty of color in AS include assumptions and mechanisms of scientific research itself; the very neutrality and disinterestedness of researchers, inherent in the scientific method, prevent recognition that values and personal biases affect decisions of hiring selections and mentoring effectiveness. We explore the cultural factors that underlie these values and biases that are common not only to agriculture but also to science more broadly.

Nutritive value of high-oil corn grown under semi-arid conditions and its impact on broiler performance and carcass composition.

A series of experiments was conducted to evaluate nutritive value of a high-oil corn (HOC) cultivar, grown under semiarid conditions, and its impact on performance and carcass characteristics of male broilers raised to market age. Conventional corn (CC) and HOC used in this research were produced under similar semi-arid conditions. By using a glucose containing reference diet in Experiment 1, the AMEn of CC, as determined on 11-d-old male broilers, was lower (P < 0.05) than that of HOC (3,541 vs. 3,669 kcal/kg DM). The TME, TMEn, and true amino acid availability of CC and HOC were determined in Experiment 2 through individual precision feeding of eight intact mature roosters per ingredient. The TMEn of HOC was significantly higher than that of CC (4,126 vs. 3,870 kcal/kg DM), but true availability of amino acids was comparable for both cultivars. By using the CP and TMEn values determined in Experiment 2, two corn soybean meal starter and grower diets, containing no added fat, were prepared in Experiment 3, in which HOC replaced CC. Diets were provided ad libitum in five replicates to 5-d-old male broilers with eight birds per replicate until market age. Broiler performance, carcass yield, and carcass composition were comparable between both corn cultivars. Birds on HOC diet, however, deposited more (P < 0.05) abdominal fat (0.695%) than those on CC diet (0.575%). The results indicated that the extra calories derived from HOC could have been funneled primarily toward abdominal fat pad deposition rather than increased growth.

Effects of vitamin E and C supplementation on performance, in vitro lymphocyte proliferation, and antioxidant status of laying hens during heat stress.

Vitamin E (dl-alpha-tocopheryl acetate) was evaluated for its effects on performance, lymphocyte proliferation, and antioxidation in layers during heat stress. In Trial 1, 25, 45, or 65 IU of vitamin E/kg were fed to four replicated pens (five hens/cage) of DeKalb Delta or Hy-Line W-36 per treatment starting at 20 wk of age. At 34 wk of age, hens were heat-stressed at diurnal temperature ranging from 21 C to 35 C for 3 wk. The performances of hens not exposed to heat stress were not influenced by supplemental vitamin E. Supplemental vitamin E did not affect egg production; however, egg mass was greater (P < 0.05) with supplementation of 65 IU of vitamin E/ kg during heat stress. Egg yolk was significantly increased (P < 0.04) when hens were fed 45 and 65 lU/kg compared with the control vitamin E level (25 lU/kg). Haugh units were higher (P < 0.01) for hens fed 65 IU of vitamin E/kg compared to 25 and 45 lU/kg. Lymphocyte proliferative responses to concanavalin A (Con A) and Salmonella typhimurium lipopolysaccharide (LPS) were greater (P < 0.0001) in hens fed 45 and 65 IU of vitamin E/kg during heat stress. Strain had no effect on any of the parameters measured. In Trial 2, a 2 x 2 factorial was designed to test effects of vitamin C in drinking water (0 and 1,000 ppm) and dietary vitamin E (25 and 65 IU/kg). Eight replications per treatment with four hens per replication cage were heat-stressed at constant temperature of 35 C for 3 wk. Egg production and egg mass were higher when hens were fed 65 IU of vitamin E/kg than when hens were fed 25 lU/kg (81.5 vs. 75.9%, P < 0.03 and 48.2 vs. 44.6 g, P < 0.03, respectively). Yolk solids weight for the 65 IU vitamin E/kg group was higher (P < 0.01) compared to the 25 IU/kg group. ConA and LPS mitogenic responses were greater in hens fed 65 IU of vitamin E (P < 0.001 or P < 0.003, respectively) or 1,000 ppm of vitamin C (P < 0.001 or P < 0.002, respectively). The combination of 65 IU vitamin E/kg and 1,000 ppm vitamin C showed the highest ConA and LPS mitogenic responses among the treatments. No interaction effects of the two vitamins on production measurements or lymphocyte proliferative responses were observed. TBA values in egg yolk and plasma of hens fed 65 IU of vitamin E/kg were lower (P < 0.0001) than those of hens that received 25 IU of vitamin E/kg. These results suggest that vitamin E supplementation at 65 IU/kg diet may enhance production, induction of in vitro lymphocyte proliferation by ConA and LPS, and antioxidant properties of egg yolks and plasma of White Leghorn hens during heat stress and that supplementation of 1,000 ppm vitamin C may further enhance in vitro lymphocyte proliferative responses of hens during heat stress.

Double immunocytochemistry of vasoactive intestinal peptide and cGnRH-I in male quail: photoperiodic effects.

Reproduction in Japanese quail is primarily regulated by photoperiod. Vasoactive intestinal peptide (VIP) has been suggested as a transducer of environmental information, especially photoperiodic cues, to the hypothalamo-pituitary-gonadal axis. To investigate the possible interaction of VIP and the reproductive (gonadotropin-releasing hormone, GnRH) system, double-immunocytochemical staining for VIP and cGnRH-I was conducted in sexually mature male quail held under a long-day photoperiod (16L:8D; LD) and in sexually quiescent males held under a short-day photoperiod (8L:16D; SD). VIP-immunoreactive (ir) cells were found primarily in three locations: lateral septal organ (LSO) in nucleus accumbens (Ac), ventral hypothalamus, and infundibular area. VIP-ir cells in LSO displayed characteristics typical of cerebrospinal fluid (CSF)-contacting cells, and co-existed with cGnRH-I-ir cells and beaded fibers. In contrast, VIP-ir cells in the infundibular area did not co-exist with cGnRH-I-ir structures. The number of visible VIP-ir cells in the infundibular area of SD males was significantly lower than that of LD males, while the number of visible VIP-ir cells in Ac/LSO was not altered by photoperiod. A cluster of cGnRH-I-ir cells in the caudalmost septal area was heavily innervated by VIP-ir fibers, which appeared to contact cGnRH-I-ir cells directly at this location. Both VIP- and cGnRH-I-ir fibers heavily innervated the external layer of the median eminence (ME). These data suggest that Ac/LSO, the caudalmost septal area, and ME are possible sites of interaction between the VIP and the GnRH systems.

Changes in immunoreactivity to anti-cGnRH-I and -II are associated with photostimulated sexual status in male quail.

In sexually active males exposed to long-day (LD) photoperiod, perikarya in the olfactory bulb, lobus parolfactorius, n. accumbens, and preoptic region were immunoreactive (ir) to an antiserum against gonadotropin-releasing hormone (anti-cGnRH-I), and a cluster of ir-perikarya was found in the caudal-most septal area. Ir-perikarya in these brain areas of sexually inactive short-day (SD) males were located within more discrete areas than those in LD brain, which were more scattered in appearance. Absolute cell numbers were similar between LD and SD brains. Ir-fibers in LD brains were mostly in the external median eminence, along the lateral ventricle to septum (especially in and about the n. accumbens), in the septal-preoptic area, along the third ventricle, and at the n. commissure palli. There were fewer ir-fibers in SD brain. Many small dark ring-like ir-structures were found in the hyperstriatum, hippocampus, and n. taeniae. Interpreted as being ir-terminals on non-ir perikarya, these were not observed in SD males. cGnRH-II ir-perikarya were observed in only two areas regardless of reproductive status: (1) ventral to the substantia grisea centralis and caudal to the oculomotor complex, and (2) scattered in and about the lateral hypothalamus. Ir-fibers occurred in the habenular area, hyperstriatum, hippocampus, parahippocampal area, cortex piriformis, and n. taeniae. cGnRH-II ir-fibers occurred in the external median eminence but were less intensely stained than cGnRH-I ir-fibers. These fibers in SD males were similar except in the diencephalon, where scattered swellings were observed. Thus, the appearance and distribution of anti-cGnRH-I and -II ir-structures change with the sexual status of male quail, but changes in immunoreactivity to anti-cGnRH-I appear to be more widespread.

Eating disorders in patients with cystic fibrosis.

This study was designed to examine rates of eating disorders and psychopathology in patients with cystic fibrosis (CF). Fifty-eight CF patients and 43 healthy control participants were evaluated using structured psychiatric interviews and rating scales. Two control participants and no CF patients were diagnosed with an eating disorder. Additionally, 11 CF patients were diagnosed with one or more psychiatric disorders. Group means on the rating scales did not show clinically meaningful elevations in either group. These data indicate no evidence for elevated rates of eating disorders in CF patients. Similarly, rates of other psychiatric disorders in the CF group were not greater than the prevalence reported in the general population.

Laying hen behavior. 1. Effects of cage type and startle stimuli.

The well-being of commercial laying hens plays an important role in egg production. Behaviors such as pacing, displaced preening, increased aggression, and redirected activities have been associated with stress in poultry. This study was conducted to determine whether two strains of commercial layers, reported to differ in level of excitability, behave differently in two types of commercial cages. DeKalb Delta and Hy-Line W36 hens, 40 to 45 wk of age, were housed six to eight per cage in open or solid-sided cages, at an equal density between cages. For each strain, there were six cages per cage type for a total of 24 cages. In the first five experiments, behavioral data were obtained at a distance of 1 m by instantaneous or scan sampling. These experiments included hen behavior in both types of cages with and without the presence of frustrating or startle conditions. Some significant differences in behavior existed within experiments but not consistently among all experiments. Sampling method did not affect reliability of data collection. Two trials were then conducted to determine whether the length of time to return to normal activity after a startle stimulus is influenced by the cage type or strain. In the first startle experiment, DeKalb hens returned to normal activity more quickly than did Hy-Line hens (P = 0.07); this strain difference was not found when the experiment was repeated. Cage type did not appear to affect the behavior of birds adversely, although neither cage type appeared to confer an advantage. No clear differences were found in behavior by strain or by strain within cage.

The effect of dietary wheat middlings and enzyme supplementation II: apparent nutrient digestibility, digestive tract size, gut viscosity, and gut morphology in two strains of leghorn hens.

An experiment was conducted with two strains of Leghorn hens, DeKalb Delta (D) and Hisex White (H), to investigate the effect of a commercial poultry enzyme preparation (EZ; xylanase plus protease) on the digestibility of protein, fat, Ca, and P and to determine any changes in the relative size of the digestive tract, gut morphology, and gut viscosity (GV) of birds fed wheat middlings (WM) over an 18-wk period. Three hundred birds (150 birds per strain) were randomly assigned to six diets: Diet 1, control (corn-soybean); Diets 2 and 3, 8% and 16% WM, respectively; Diet 4, 8% WM and 0.1% enzyme (EZ); and Diets 5 and 6, 16% WM and 0.1% and 0.2% EZ, respectively. There were five replicates per diet per strain. At 50 wk, protein digestibility increased significantly with supplementation of EZ, but, at 60 wk, all responses were similar. Protein digestibility was greater in DeKalb Deltas for WM with EZ compared with Hisex on the same treatment. Fat digestibility was greater for Diet 1 than the other diets at 50 wk but showed a similar response at 60 wk. The H strain showed a reduction in fat digestibility with WM diets with EZ. The control diet showed greater Ca digestibility than the other diets at 50 wk but did not differ at 60 wk. Phosphorus digestibility increased significantly for WM diets with or without EZ at 60 wk. Intestinal weight was significantly higher for WM with or without EZ at 50 wk, but was equal to the control diet at 60 wk. At 60 wk, gizzard weights (GW) were also lower in birds fed WM and WM with EZ compared with birds fed the control, but GV was not affected by dietary treatments. Histological observations on jejunum of birds fed WM without EZ showed shortening, thickening, and atrophy of the villi, all of which improved when EZ was included in the diet. Availability of some nutrients in WM diets was improved with supplementation of enzyme. Gastrointestinal (GI) tract and organ size were increased, and gut morphology appeared to be improved.

Neural sites and pathways regulating food intake in birds: a comparative analysis to mammalian systems.

The paper reviews hypotheses explaining the regulation of food intake in mammals that have addressed specific anatomical structures in the brain. An hypothesis, poikilostasis, is introduced to describe multiple, homeostatic states whereby the regulation of metabolism and feeding occur in birds. Examples are given for both wild and domestic avian species, illustrating dynamic shifts in homeostasis responsible for the changes in body weights that are seen during the course of an annual cycle or by a particular strain of bird. The following neural structures are reviewed as each has been shown to affect food intake in birds or in mammals: ventromedial hypothalamic nucleus (n.), lateral hypothalamic area, paraventricular hypothalamic n., n. tractus solitarius and area postrema, amygdala, parabrachial n., arcuate n. and bed n. of the stria terminalis. Two neural pathways are described which have been proposed to regulate feeding. The trigeminal sensorimotor pathway is the most complete neural pathway characterized for this behavior and encompasses the mechanics of pecking, grasping and mandibulating food particles from the tip of the bill to the back of the buccal cavity. A second pathway, the visceral forebrain system (VFS), affects feeding by regulating metabolism and the balance of the autonomic nervous system. Wild, migratory birds are shown to exhibit marked changes in body weight which are hypothesized to occur due to shifts in balance between the sympathetic and parasympathetic nervous systems. Domestic avian species, selected for a rapid growth rate, are shown to display a dominance of the parasympathetic nervous system. The VFS is the neural system proposed to effect poikilostasis by altering the steady state of the autonomic nervous system in aves and perhaps is applicable to other classes of vertebrates as well.

The use of the chicken embryo screening test and brine shrimp (Artemia salina) bioassays to assess the toxicity of fumonisin B1 mycotoxin.

Chicken embryos and brine shrimp naulpii were utilized in short-term toxicity bioassays to assess their sensitivity to the mycotoxin fumonisin B1 (FB1). Fertile chicken eggs (Cobb x) were dosed with FB1 on day 2 of incubation by the injection of 100 microliters of aqueous solution into the air space of each egg. Eggs were incubated with mechanical rotation until hatch, at which time mortality was assessed. Probit transformation of the mortality data produced a linear line of best fit (P < 0.05), from which an LD50 of 52 micrograms FB1/egg, equivalent to a concentration of 1.3 microns hatched in artificial seawater and exposed to FB1 in an optimized 96-well plate assay with a 48 hr mortality endpoint. Probit transformation of the mortality data resulted in an LC50 of 1.7 microns FB1, or 1.2 micrograms FB1/ml. Thus, at the cellular level, both bioassays appeared sensitive to FB1; however, from the standpoint of use as a screening assay, the chicken embryo bioassay is limited by the relatively high dose of FB1 required per egg. It is anticipated that the design and simplicity of the brine shrimp bioassay will accommodate screening for FB1 toxicity in contaminated samples.