Percent Hen-day Egg Production Research Articles

Physiological Profile of Caged Layers During One Production Year, Molt, and Postmolt: Egg Production, Egg Shell Quality, Liver, Femur, and Blood Parameters

A longitudinal study of a flock of Single Comb White Leghorn pullets was initiated at 19 weeks of age (preproduction) and continued through a production year, a forced molt, and for 4 months of postmolt production. A representative sample of hens was obtained at 12-week intervals during the first year and at subsequent selected times. Liver lipid, femur weight, femur volume, femur density, egg weight, shell weight, percent shell, milligrams shell/square centimeter of shell surface area, serum calcium, serum phosphorus, and serum alkaline phosphatase were determined.Percent hen-day production peaked at 90% and then declined by .6 to .7% each week during the first production year. After molting, percent hen-day egg production peaked at 80% and declined .9% per week over the subsequent 20 weeks. Egg weight increased continually during the first production year. Shell weight was greatest immediately postmolt; thereafter it declined. Shell thickness was greatest at 31 weeks of age and declined throughout the first year. After molting, the shell thickness of 83-week-old hens was similar to values of hens about 37 weeks of age. Serum calcium and phosphorus of laying hens were influenced by age, feed intake and environmental temperature. The lowest values occurred during hot weather. Liver lipid was lowest in nonlaying hens (17 to 20%) and was approximately 42% of dry weight in laying hens. Femur density was greater in laying than nonlaying hens.

Correlated responses of chickens to selection for production of antibodies to sheep erythrocytes.

A bidirectional selection experiment was conducted to measure 5-day antibody titers to sheep erythrocytes in White Leghorn chickens. There was an immediate response to selection with significant differences between lines for the selected trait found in the S1 and all subsequent generations. Comparisons of S6, S7 and S8 generation females revealed differences between lines in disease resistance and in certain reproductive traits such as age at first egg, percentage hen-day egg production, percentage fertility and duration of fertility. The implications of these correlated responses are important to selection programs for general disease resistance.

Effects of Forced Molt Period on Postmolt Performance of Leghorn Hens

Sixty-four-week-old Single Comb White Leghorn (SCWL) hens were subjected to the following treatments: 1) no forced molt (control); 2) forced molt for 4 weeks (FM4); 3) forced molt for 6 weeks (FM6): and 4) forced molt for 8 weeks (FM8). Molt was induced by restricting feed, water, and photoperiod. Data were analyzed at the 5% level of probability.During the early postmolt period (72 to 76 weeks of age), birds in all FM groups consumed significantly more feed and had significantly higher hen-day egg production than birds in the control group. Albumen height and shell thickness measured at 76 weeks of age were significantly improved by all FM treatments.During the postmolt period (72 to 124 weeks of age), hens in the FM8 group had the highest hen-day egg production and best feed efficiency, whereas birds in the control group had the lowest hen-day egg production and poorest feed efficiency. However, these differences were not statistically significant. Percent hen-day egg production was positively and significantly correlated with FM period. Mortality rate during this period was significantly lower for the FM4 and for the FM8 groups as compared to the control group. Egg shell thickness was significantly improved in two out of the three FM treatments.

Residual Activity of Selected Pesticides on Laying Hens Treated for Northern Fowl Mite Control by Dipping ,

Aqueous suspensions of malathion, stirofos, Ravap, and carbaryl formulations (.25 to 1.0%) were tested as dips for control of the northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini and Fanzago), on caged White Leghorn hens. Hens treated with Ravap showed symptoms of organophosphorus insecticide poisoning soon after treatment and some died as a result of the dip; however, dipping with the other insecticides did not result in any apparent toxic effects. Malathion gave residual control of mites for about 4 weeks posttreatment, but both stirofos and carbaryl dips gave complete control for at least 6 weeks against repeated challenges with the NFM. There were no significant differences in the percent hen-day egg production, feed consumption, or body weight of the hens that could be attributed to any of the chemical treatments.

Effects of Dietary Calcium Sources and Particle Size on Laying Hen Performance

A total of 462 high producing commercial type laying hens were used to determine the effects of various calcium sources and particle size on egg shell quality and laying hen performance. Neither calcium source, particle size, nor level of calcium had a statistically significant effect on egg weight, percent hen-day egg production, or feed conversion among individual treatments. The results indicate that the addition of large particle oyster shell does significantly improve egg shell quality when substituted for a portion of the pulverized calcium source, even though the hens are consuming adequate calcium (>3.75 g/hen/day), with improvement being significantly greater after 24 weeks of lay. It was also concluded that the calcium from oyster shell, in any form, is more available than that of limestone for egg shell formation. Aragonite was shown to support performance equal to that of pulverized limestone at the 3.5% calcium level.

Effect of Diurnal Programs of Nutrient Intake on Performance of Broiler-Breeder Hens

The daily rations for two strains of broiler breeder hens on a restricted feeding program were divided among 1, 2, or 3 feeding times per day and the diet was provided either by a single medium-protein feed-mix or by dual low-protein and high-protein feed-mixes each day.Increasing the frequency of feeding to 3 times from once daily increased egg weight, decreased 36-week body weight and, during the first 10 weeks of lay, increased percent hen-day egg production. Separate provision of low- and high-protein feeds increased egg weight and decreased grams of feed per gram of egg. The effect on body weight of feeding frequency and the use of dual protein levels was greater for one strain than the other. Increasing feeding frequency increased mortality of one strain of hens. The modification of diurnal feeding pattern increased efficiency of feed utilization. Changes in the partitioning of nutrients for synthesis of egg versus body tissue may be responsible for this improvement.

Changes in Unselected Traits Accompanying Long-Term Selection for Four-Week Body Weight in Japanese Quail

The changes in unselected traits following long term selection for high 4-week body weight were evaluated in two Japanese quail lines. Means of these traits (16-week body weight, age at first egg, egg weight, egg production, fertility, and hatchability) of breeders were also used to obtain estimates of trends across generations by regressing line means on generation number.Differences between lines for all traits except percentage hen-day egg production were significant. Body weights and egg weights of the selected lines were larger than corresponding measurements in the nonselected line, whereas fertility and hatchability measurements were larger in the nonselected line.

Influence of Fusarium-Infected Corn and F-2 on Laying Hens

Diets containing either Fusarium-infected corn supplying 25 and 100 p.p.m. of F-2 (zearalenone) or of purified F-2 at these levels did not adversely influence the reproductive performance of laying hens. In trial 1, no deleterious effects were observed for 20- and 36-week body weights, age at first egg, egg weight, albumen height, shell deformation, fertility or hatchability when Fusarium-infected corn was fed to 20-week-old pullets for 28 days. Percent hen-day egg production of birds fed Fusarium-infected corn supplying 25 and 100 p.p.m. of F-2 was superior (P ≤ .05) to egg production of nontreated controls.In trial 2, three replications of ten adult Leghorn hens were evaluated under five dietary treatments: (1) 16.7% protein basal; (2) basal plus Fusarium-infected corn (25 p.p.m. of F-2); (3) basal plus 25 p.p.m. of (purified) F-2; (4) basal plus Fusarium-infected corn (100 p.p.m. of F-2); (5) basal plus 100 p.p.m. of (purified) F-2. Difference between dietary treatments for 14-day pre-treatment, treatment and post-treatment periods were nonsignificant for 42- and 44-week body weights, egg production, egg weights, fertility and hatchability. Body weights of chicks from hens fed F-2 diets were not significantly different from those of chicks from hens fed the basal diet.