Normal Egg Production Research Articles

Phenoloxidase Activity in the Reproductive System of Biomphalaria glabrata: Role in Egg Production and Effect of Schistosome Infection

Infection by larval trematodes often causes a cessation of egg production in its molluscan intermediate host and is referred to as parasitic castration. Because phenoloxidase (PO) has been shown to be involved in egg formation in other invertebrate species, we investigated the role of PO in normal egg production in the snail, Biomphalaria glabrata, and the effects of Schistosoma mansoni infection on the PO pathway in this snail. Our data showed that PO activity in the albumen gland (AG) is initially expressed when snails reach a size of approximately 8 mm in shell diameter and continues to increase as snails grow, indicating a developmental link between snail size and AG PO expression. Egglaying was also shown to be coincidental with the onset of PO expression in the AG, thereby supporting a direct association between PO activity and egg production. In addition, exposure of snails to diethyldithiocarbamate (DDC), a PO inhibitor, affected normal in vivo egg production, as evidenced by a significant decrease in the numbers of eggs laid in DDC-treated groups compared to nontreated groups. Normal resumption of egg-laying activity in treated snails following withdrawal of the drug indicated that inhibition was reversible. Taken together, the results of our developmental and DDC-exposure studies provide strong support for a crucial role of PO in normal egg production in this animal. Finally, AG PO activities of infected and uninfected control snails were measured over the course of S. mansoni infection. Our results showed that both total and specific enzyme activities in the AG of infected snails were significantly decreased at 28 and 33 days postinfection (PI) when compared to those of control snails. Results of subsequent experiments assessing the effects of larval infection on L-tyrosine (PO substrate) levels in AG and ovotestis revealed a significant increase in the levels of this compound in both organs over the course of infection. It is concluded that AG PO activity is functionally linked to egg formation in normal snails and that a strong association exists between parasite-mediated decrease in AG PO activity and parasitic castration. However, from the data presented, a direct causal relationship linking infection, decreased PO, and castration has yet to be established.

The Effect of Disulfiram in Egg Shell Formation in Adult Trichuris muris

The effect of disulfiram on egg shell morphology in the parasitic nematode Trichuris muris was studied in vitro and in vivo. Daily disulfiram treatment of mice infected with T. muris beginning 25 days after infection and continuing for 26 days resulted in the production of malformed eggs by adult female worms in all treated groups. In addition, significantly fewer adult worms were found at necropsy in mice treated with 5.0 or 7.5 mg/kg/day of disulfiram as compared with mice treated with 2.5 mg/kg/day or control mice. Adult worms collected from infected, untreated mice and placed in aerobic culture for 5 days in media containing 4 or 8 micrograms/ml of disulfiram released malformed eggs into the culture medium after 30 hr in culture. Oral inoculation of naive mice with malformed eggs did not result in T. muris infections in the mice. The results of these studies suggest that inhibition of phenol oxidase results in disruption of normal egg production by T. muris females and that the enzyme might be a useful target in the development of control strategies aimed at nematode parasites that rely on phenol oxidase for egg shell hardening.

Diet selection for protein by poultry

If birds can learn to associate different sensory properties of foods with different metabolic feelings caused by different protein contents, then they should be able to choose a balance of foods which makes them feel most comfortable. Broiler chickens given a choice between two foods, one containing a higher concentration of protein than required and the other a lower concentration, eat amounts of the two which will give a diet that is close to optimum for growth in terms of overall protein content. When both foods have excessive or insufficient protein the birds eat predominantly from that closer to their requirements. As broilers grow they choose a progressively lower protein diet in line with their reducing protein:energy requirements. Strains with higher potential rates of lean deposition voluntarily consume a higher ratio of high-protein to low-protein food compared with low-growth strains, while strains selected for high fat deposition eat less protein per unit of energy than lean birds. Males select higher protein diets than females. Although increases in environmental temperature would be predicted to reduce energy requirements and thus increase the protein:energy ratio in selected diets, heat-stressed birds do not increase the protein content of their diet, probably because of the high heat increment of protein metabolism. Short periods of access to one food alone are followed by a preference for the opposite food when access to both is restored. When given appropriate training, laying hens can balance their diet for protein but not as well as broilers. There is evidence that growing chicks can differentiate high-lysine from low-lysine foods but do not entirely balance their diet for lysine. Methionine-deficient broilers eat more of a methionine supplemented food than normal birds, while laying hens eat some methionine-fortified food when given a choice against a low-methionine food, but not enough to support normal egg production. It is concluded that poultry can show a great degree of ‘nutritional wisdom’ as far as protein is concerned but that they need to be allowed to differentiate between foods with different nutrient profiles by sensory means, and a lack of training might account for some of the poor results obtained.

The effect of a bisphosphonate on bone volume and eggshell structure in the hen

Bisphosphonates, used in the prevention and treatment of osteoporosis, in man, can prevent bone loss in experimental models of osteoporosis in mammals. In egg-laying hens there is a high incidence of bone fractures which are due to osteoporosis. Alendronate, a bisphosphonate, was given to three groups of hens in mid-lay. Different doses of alendronate were given to each group and group 4 was a control. The birds were killed after 2 weeks of treatment. The hens receiving the highest dosage of alendronate (1 mg/kg every 2nd day) ceased laying and had reduced serum calcium concentrations. Lower dosages of alendronate (0.1 and 0.01 mg/kg every 2nd day) resulted in normal egg production and serum calcium concentrations. Egg shells with ultra-structural features indicative of reduced shell quality were produced by hens on the two higher dosages, but the egg shells from the controls and from the hens on the lowest dosage were considered normal. When alendronate was administered to hens in mid-lay there was no effect on trabecular bone volumes, but there was a reduction in mean medullary bone volume in some groups. In a second experiment, pullets were treated with alendronate (0.01 mg/kg twice a week) before the onset of lay. The pullets were killed after laying their first egg. In the pullets treated with alendronate, this protocol resulted in a significantly greater volume of trabecular (structural) bone at the onset of lay.

Selection for Body Weight at Eight Weeks of Age.: 20. Production Traits and the B and C Alloantigen Systems

The current study evaluated influence of genotypes of the B and C alloantigen systems on production traits in lines of White Plymouth Rock chickens. Lines had been selected previously for high (HWS) or low (LWS) 8-wk BW and after 27 generations of selection, a random sample of each selected line was used to initiate subpopulations in which selection was relaxed. For the present study, blood typing was used to identify allelic frequencies for the B and C systems for five consecutive generations of selection (Generations 30 through 34) and three consecutive generations of relaxation (Generations 5 through 7). Haplotypes for the B complex were assigned designations B32, B33, B34, and B35 and alleles of the C system were assigned C8, C9, C10, and C11. Production traits for males were BW at 4 and 8 wk of age, and for females were BW at 4, 8, and 38 wk of age, age and BW at production of first egg, percentage of normal eggs, and percentage of normal hen-day egg production. There were no differences in production traits among B genotypes or among C genotypes, although some time trends in gene frequencies suggested that more subtle effects may be present.

ExperimentalSalmonella enteritidisphage type 4 infection and egg transmission in Japanese quails

Japanese quails were inoculated orally with 1 x 10(10) colony-forming units of Salmonella enteritidis phage type 4 isolated from chicks to obtain information concerning S. enteritidis infection and egg transmission. The inoculation resulted in a bacteraemic infection with seeding of the liver, spleen, intestine, peritoneum, ovule, ovary and oviduct. Some infected birds showed diarrhoea, ruffled feathers, depression, loss of appetite and death. However, most infected birds remained clinically normal with normal egg production. Salmonella enteritidis was isolated from the albumen of 7, yolk of 15, shell of 13, and shell membrane of 15 of 164 eggs. The experiment suggests that S. enteritidis phage type 4 is invasive for Japanese quails and the infected eggs laid by S. enteritidis infected quails are probably the result of transovarian infection.

Wheat Middlings as an Alternate Feedstuff for Laying Hens

Three long-term experiments were conducted to evaluate the possibility of using wheat middlings (WM) for laying hens and to study the responses of six strains of commercial laying hens fed WM diet. In Experiment 1, 320 layers maintained in floor pens were fed diets containing 45% WM with .25 or .75% salt, or 89% WM with .25% or 1.5% salt. Salt supplementation did not show any beneficial effect on egg production. Hen-day egg production by hens fed the 45% WM diet was significantly higher for hens fed 45% WM than for those fed the 89% WM diet (79 versus 67.5%, 44-wk period). Feed, limestone, and water intakes were increased by the 89% WM diet. Yolk color, Haugh units, hen livability, and reproductive parameters were not different among the dietary treatments.In Experiments 2 and 3, laying hens from six commercial strains (four strains each experiment, 240 hens per strain) were maintained in laying cages in each year, and fed either a corn and soybean meal (CSM) or a 25% WM diet. Results show that neither diet nor strain had effects on hen-day egg production; however, egg weights from Strains A, C, and F were heavier than those from Strains B, D, and E. Feed intakes and feed utilizations were similar among the strains. The 25% WM diet increased egg weight, feed intake, and feed utilization compared with the CSM diet. Livability of hens was 93.8 to 97.5% and was not affected by either strain or diet. It is concluded that commercial strains of laying hens can be fed diets containing 25 to 45% WM and still have normal hen-day egg production although feed utilization will be poorer.

Genetic analyses of Bantam and selected low-weight White Plymouth Rock chickens and their crosses. II. Onset of sexual maturity and egg production

Summary - Two generations of crosses between a population of White Plymouth Rock Bantams and a line of White Plymouth Rocks selected for low body weight for 31 generations were produced. Characteristically, the Bantams had produced a high proportion of normal eggs, but hen-day normal egg production in this population was low. The hens selected for low body weight also produced a high proportion of normal eggs, but age at sexual maturity had been greatly delayed as a correlated response to selection. In the 16 populations involving parental lines and crosses (Fi, F and backcrosses), age at onset of sexual maturity and egg production traits were measured. Comparisons of these populations suggested that age at sexual maturity was influenced by sex linkage, by one or more genes with major effects and by other genes with lesser effects. When compared to performance of the parental populations, some measures of reproductive fitness were improved by crossing (age at first semen production, age at first egg, hen-day normal egg production). Other traits were not changed by crossing (percent normal eggs, duration of fertility). selection / Bantam / chickens / sexual maturity / egg production

Complete life cycle of the canid tapeworm, Echinococcus multilocularis , in laboratory rodents

Mongolian gerbils, Meriones unguiculatus, when treated at intervals of 2-6 days with prednisolone tertiary butyl acetate, sustained infection with adult Echinococcus multilocularis in the small intestine, with the tapeworm exhibiting normal strobilation and egg production as in the natural canid host. Host age is critical for the survival of the tapeworm in normal gerbils; parasites survive for only 2 days in 20-wk-old animals, 4 days in 4-wk-old animals, but at least 7 days in 3-wk-old animals. The host age dependence in parasite recovery between days 28-37 postinfection was not affected by treatment from around the day of infection. Starting the treatment before infection (on day -17 relative to infection) remarkably improved the tapeworm's survival within the intestine of older animals. Eggs produced in this rodent model system 28 days postinfection were infective to rodents such as Mongolian gerbils and gray red-backed voles, Clethrionomys rufocanus bedfordiae, by oral or intraperitoneal inoculation. The E. multilocularis/Mongolian gerbil system can replace the natural canid hosts as a new way to obtain infective eggs and to analyze host-parasite interactions. The development of an alternative definitive host for zoonotic tapeworms may accelerate experimentation in this field.

Energy Metabolism of Broiler Breeder Hens.: 1. The Partition of Dietary Energy Intake

The partitioning of AME intake (MEI) and recovered energy (RE; defined as MEI minus heat production) was investigated on Hubbard broiler-breeder hens (BB) by using indirect calorimetry and energy balance. The regression of RE on MEI was linear (R2 = .96; P<.01) with a slope of .817 ± .024 (SE) and a y-intercept of −238.3 ± 10.7 (SE). The maintenance energy requirement was 292 kilojoule (kJ) per kg per day (367 kJ per kg.75 per day). The regression of body RE, defined as RE minus egg energy, on MEI was linear (R2 = .96; P<.01) with a slope of .799 ± .045 (SE) and a y-intercept of −344.9 ± 19.7 (SE). Therefore, an MEI of 432 kJ per kg per day was required by BB hens to maintain body energy equilibrium when they were laying at approximately 85% production. At an MEI of less than 432 kJ per kg per day, body energy was used for egg production. The AME cost of depositing 1 kJ of body, egg, protein, or fat energy was (x̄ ± SE) 1.21 ± .06, .91 ± .32, 1.96 ± .71, and 1.05 ± .15 kJ, respectively. The results indicate that individually caged BB hens between 28 and 36 wk of age in a thermal-neutral environment (21 C) require approximately 1.6 megajoule (MJ) of AME per bird per day for normal growth (3 g/per day) and egg production (85%).

Pathogenesis of Salmonella enteritidis Infection in Laying Chickens. I. Studies on Egg Transmission, Clinical Signs, Fecal Shedding, and Serologic Responses

Laying hens were inoculated orally, intracloacally (IC), or intravenously (IV) with Salmonella enteritidis phage type 8 isolates from a human (E700-87) eggs (Y-8P2), or the ovary of a hen (27A). Oral or IV inoculation of 2 x 10(8) to 4 x 10(8) colony-forming units (CFU) of E700-87 caused depression, anorexia, reduced egg production, diarrhea, and some mortality. Lower doses resulted in milder clinical signs. S. enteritidis was cultured from the shells of a few eggs but not from egg contents. Fecal shedding persisted for up to 6 weeks in some birds. Isolate Y-8P2 (10(6) CFU) also caused anorexia, diarrhea, and a drop in egg production. Hens inoculated orally or IC were less severely affected than those inoculated IV. Fecal shedding was intermittent and lasted up to 18 days. Eggshells from the IC-inoculated birds had the highest rate of contamination, and S. enteritidis was isolated from the albumen of 11 and yolk of three of 726 eggs. Oral inoculation of 10(6) CFU of isolate 27A resulted in a bacteremic infection with seeding of the liver, spleen, peritoneum, ovule, and oviduct. However, the birds remained clinically normal with normal egg production. S. enteritidis was cultured from the yolk and albumen of a small number of eggs until 11 days postinfection. Antigen prepared from S. enteritidis detected antibody in more sera than did commercially available S. pullorum antigen in agglutination tests.

Effect of flubendazole on the number of first-stage larvae of Angiostrongylus cantonensis released in the faeces of treated rats

The effect of flubendazole orally administered at 10 mg/kg/day for 5 consecutive days (the 11th, 20th or 40th post-infection) on the number of first-stage larvae (L1) of Angiostrongylus cantonensis released in the faeces of rats each infected with 40 third-stage larvae was determined. Faecal examination for 5 months, the period from medication to dissection of rats, showed that L1 release ceased in all the rats of medicated groups by about 1 week after the termination of dosing and resumed 1-2 months later in 86% of the rats which were dissected at the end of experiments with the recovery of adult worms of both sexes. Throughout the period of 5 months, about 2-4 x 10(4) L1/gram of fresh faeces was recorded in non-medicated control groups. There was a 38-79% reduction in adult worms at the dissection. Microscopic examination of the uteri of the remaining adult worms and lung tissues of rats confirmed no normal egg production in the adult worms from rats of medicated groups, except the rats with the resumption of faecal L1 release.

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

Turkey hens were thyroidectomized at different ages and phases of their reproductive cycles. Egg production, primary remige molting, and plasma thyroxine (T4) and triiodothyronine (T3) concentrations were monitored during each of three experiments.Thyroidectomy of hens (26 and 30 wk of age) prior to photoinduction of egg production prevented subsequent egg production and molting. Thyroidectomy of adult hens (36 wk of age) early in the egg production cycle caused a gradual termination of egg laying without the occurrence of molting. Thyroidectomy of mature hens (66 wk of age) during the light restriction period prior to their second egg production cycle prevented subsequent egg laying and molting. All successful thyroidectomies reduced plasma T4 and T3 to concentrations below the sensitivity levels of the assays. Feeding 1 ppm T4 to thyroidectomized hens resulted in resumption of normal egg production and molting. These results indicate that the thyroid is essential for the initiation and maintenance of egg production and for molting in turkey hens.

Restricted Feeding in Early and Late-Feathering Chickens.: 2. Reproductive Responses

Reproductive traits of females from a broiler-breeder parent stock segregating for early and late feathering were measured under four feeding regimens. Feeding regimens consisted of ad libitum (AL, feed was always available), ad libitum restricted (ALR, feed restricted daily to control body weight), and skip-one-day and skip-two-days (SOD and STD, given two or three times ALR allowance on Day 1 and not fed on the next 1 or 2 days, respectively). At 160 days of age, pullets on SOD and STD were changed to ALR feeding, and daily feed allowances were increased to 135 g by Day 180 and 138 g by Day 250.Early and late feathering chickens responded similarly, except that hen-day ovulation rates, relative egg shell weights, and incidences of extracalcified and compressed eggs were greater for the former than the latter. For most traits measured, differences among restricted feeding regimens were minor, but considerable differences were noted between them and the AL regimen. Females fed AL reached sexual maturity approximately 60 days earlier than those whose feed intake was restricted. Also, body weights at onset of lay were about 1,200 g greater for AL than for feed-restricted females. Percentages of hen-day ovulation, normal egg production, and duration of fertility were lower, whereas incidence of defective eggs was higher for AL than for feed-restricted chickens.

Comparative susceptibility of the copepod Acanthocyclops vernalis to a microsporidian parasite, Amblyospora connecticus, from the mosquito Aedes cantator

The comparative susceptibility of each developmental stage of the copepod Acanthocyclops vernalis to Amblyospora connecticus, a microsporidian parasite of the mosquito Aedes cantator, was determined in laboratory transmission tests. Adult female and juvenile copepodid stage A. vernalis were found to be susceptible, while adult male and larval nauplii stages were not. Parasite development is restricted to the median ovary and paired lateral oviducts, which become swollen and noticeably distended in host female copepods. Ovarian infection interferes with normal egg production and appears to explain the differential susceptibility of each host developmental stage to infection. Observations of naturally acquired infection in field populations of A. vernalis were consistent with the laboratory studies. No infections were detected in adult males or gravid females and only female copepods without egg sacs (20%, n = 613) were found to be infected.

Time of lay in hens exposed to intermittent lighting.

1. Two short-term trials are described in which laying hens were exposed to 8 h light followed by 8 one-min pulses of light at hourly intervals followed by 8 h darkness (8L:8i:8D). The effect of varying the intensity of illumination during the one-min pulses and the effect of placing the intermittent lighting before the 8 h photoperiod (8i:8L:8D), were studied. 2. Normal egg production was maintained by the 8L:8i:8D system when the light pulses were at 20 lux, but not at 5 lux. This suggests a minimum threshold for illumination with short light pulses higher than that needed for continuous lighting. 3. Time of lay under 8L:8i:8D was the same as with 8L:16D in relation to the beginning and ending of the 8 h main photoperiod, but with 8i:8L:8D mean time of lay was 2 to 3 h earlier. Thus the hourly pulses caused a phase advance when placed before the normal photoperiod but did not cause a phase delay when placed after the normal photoperiod.

Starvation survival of the stored product pest Liposcelis bostrychophilus Badonnel (Psocoptera, Liposcelidae)

The parthenogenic booklouse Liposcelis bostrychophilus Badonnel, a domestic pest of farinaceous foods, tolerated long periods without food in laboratory experiments. Survivorship was enhanced by lower temperatures and higher humidities. Even in conditions (20°C and > 60% r.h.) similar to those in households, these liposcelids lived for up to two months without food. Starved individuals recommenced normal egg production within a week when provided with food and a favourable environment. The implications of these findings in relation to the dispersal and control of this pest are discussed.

Selection for Body Weight at Eight Weeks of Age.: 19. Influences of Heterozygosity and Dwarfism on Early Egg Production and Associated Traits

Body weight, body components, and reproductive traits were compared during the first 60 days after onset of lay in pullets from lines of White Plymouth Rocks selected for high or low juvenile body weight, their reciprocal F1 crosses, an F2 cross, and dwarfs from the parental lines. Absolute and relative body weight gains were less for dwarf than for nondwarf pullets in the high weight line. In the low weight line, there were differences in absolute but not relative weight gains. Among nondwarfs, both relative and absolute changes in body weight during the first 60 days of lay were similar for crosses and the high weight parental line, and considerably less for the low weight parental line. Numbers of ovulation were the same for the crosses and the high weight parental line, however, more normal eggs were produced by F1 crosses than either parental line. Rate of production was influenced mainly by variation in body weight at onset of lay in the high weight nondwarfs and low weight dwarfs, and by age at first egg in low weight nondwarf pullets. None of the independent variables had a significant association with normal egg production in crosses and high weight dwarf populations.

Essentiality of Vitamin D3and its Metabolites in Poultry Nutrition: A Review

SummaryVitamin D (cholecalciferol) is one of the most important dietary factors responsible for normal growth, egg production, shell quality and reproduction in fowls. Unlike other vitamins, 7-dehydrocholesterol in the skin is converted to vitamin D3 in the presence of ultra-violet radiation. In the modern poultry industry where the birds are raised mostly indoors, the essentiality of vitamin D is important for profitable egg and meat production.Cholecalciferol undergoes two sequential hydroxylations; the first in the liver to form 25 hydroxyvitamin D3, and the second in the kidney to form the active metabolite 1,25 dihydroxyvitamin D3. The latter metabolite is a steroid hormone which plays a major role in bone mineral mobilization and active intestinal absorption of calcium and phosphorus, accommodating the increased calcium demands by maintaining calcium homeostasis through the vitamin D endocrine system in the laying hen.Due to the continuing problems of poor egg shell quality in the poultry industry, scientists have been investigating the value of feeding vitamin D3 and its metabolites. Most research supports the National Research Council's recommended laying hen requirement of 500 ICU of vitamin D3/kg of diet. However, evidence suggests that the 25 hydroxyvitamin D3 metabolite is 2.0 to 2.5 times more active than vitamin D3 for normal egg production and shell quality. The most active 1, 25 dihydroxyvitamin D3 metabolite has an antirachitic activity 10 times that of vitamin D3. However, feeding laying hens 1, 25 dihydroxyvitamin D3 as their sole source of vitamin D produced eggs that had a high incidence of embryonic mortality prior to hatching. Improvements in hatchability of these eggs were observed when several forms of vitamin D3 were injected into the eggs. It appears that 1, 25(OH)2 D3 is not transferred or stored in the egg yolk or the vitelline membrane may be lacking specific receptors for 1,25 (OH)2 D3. Which of these possibilities is correct will undoubtedly become apparent with continued investigation.

Control of Spodoptera littoralis through moth and eggs treatment with Bacillus thuringiensis

The effectiveness of Bacillus thuringiensis var. galleriae HD-129 against the moths and egg masses of the cotton leafworm, Spodoptera littoralis , has been demonstrated in laboratory experiments. The longevity and egg production were significantly affected when the moths were fed on a sucrose diet containing 17.2 × 10 3 IU of the tested formulation/mg or higher rates. At lower concentrations (4.4−8.7 × 10 3 IU/mg), the females gave normal egg production, but the longevity was adversely affected. Investigations show that a formulation with spores alone affects the egg production and hatching, while a formulation with active crystals alone had no effect on egg production. Sprays of B. thuringiensis combined with sucrose on flowering cotton plants seem to affect the biology of the moths released on it. Egg masses sprayed with B. thuringiensis hatched normally, but the survival of the hatched larvae was reduced when treatment was made shortly before egg hatching. Based on the results obtained, B. thuringiensis showed a promising effect in the control of the moth S. littoralis as well as an ovicide larvicide agent.