Forced Molting Research Articles

Forced Molting in Raptors

Forced Molting in Raptors

An evaluation of low-energy feedstuffs in diets for laying hens

Rice bran (RB), alfalfa meal (AM), wheat bran (WB) and maize gluten feed (MGF) were used in layer diets containing 2500, 2600, 2700 and 2800 keal metabolizable energy kg −1 (10.46, 10.88, 11.30 and 11.72 MJ kg −1), and compared with diets based on maize and soya-bean meal (MS). Each diet was given to eight replicates of five individually caged hens, following a forced molt. Layer performance was influenced more by the source of low-energy feed than by dietary energy levels per se. Hen-day production, egg weight, feed intake, feed per dozen eggs and weight gains for AM, RB or WB diets were similar to that for MS control diets with equivalent energy content. Egg production was similar for hens fed on a low ME level of 2600 keal kg −1 with these feedstuffs and hens given higher energy diets. Increasing MGF levels significantly reduced layer performance. It appears that layer performance on the lower ME diets is highly dependent on the type of feed by-product used.

Optimal Replacement Policies for Rejuvenated Assets

AbstractThe Faustmann‐Samuelson solution for optimal asset rotation is extended to consider both asset rejuvenation and nonconstant prices. A dynamic theoretical model is developed in terms of an optimal control problem with discontinuous control variables, and numerical solution procedures are outlined. The model is applied to layer hen replacement where hen rejuvenation by forced molting is a common industrial practice. Results indicate a sensitivity between the decision to rejuvenate or replace a hen and the egg price cycle, suggesting a mixed rotation strategy.

Use of High Levels of Dietary Aluminum and Zinc for Inducing Pauses in Egg Production of Japanese Quail

The effect of using a high level of dietary aluminum (.3% Al, as aluminum sulfate) was compared with that of using dietary zinc (1.5% Zn as zinc oxide) for force molting Japanese quail hens. A basal diet (2.5% Ca and .35% available P) was fed alone or supplemented with Zn or Al for 7 days in Trial 1 and for 4 days in Trial 2. Light was maintained at 16 h light (L):8 h dark (D) in Trial 1 and reduced to 8L:16D during Days 1 to 14 in Trial 2. In Trial 1, feed intake averaged 23, 11, and 7 g/hen/day during Days 1 through 7 for the control, Al, and Zn treatments, respectively. Both the Al and Zn treatments significantly (P<.05) reduced body weight. In both trials, egg production approached 0% by Days 3 and 5 for hens in the Zn and Al treatments, respectively. In Trial 2, egg shell breaking strength was significantly (P<.05) reduced by dietary Al and Zn. Aluminum significantly reduced plasma inorganic P, measured on Day 5.In Trial 3, diets containing graded levels (0, .05, .10, or .15%) of Al were fed to Japanese quail hens for 28 days. Both .10% and .15% Al significantly (P<.05) reduced egg shell breaking strength during Days 8 through 12 and body weight at Day 28. Feeding .15% Al significantly reduced feed intake and egg production.Results demonstrated that high levels of dietary Al can negatively affect egg production of Japanese quail. If dietary Al is present in high enough amounts, it can induce pauses in egg production, possibly through its effect on feed intake, P metabolism, or both.

Changes in plasma thyroid hormones, luteinizing hormone (LH), estradiol, progesterone and corticosterone of laying hens during a forced molt

1. 1. Circulating concentrations of iodothyronines, luteinizing hormone(LH), estradiol(E2), progesterone and corticosterone were measured in hens before, during, and after a forced molt induced by fasting. 2. 2. Corticosterone increased at the onset of molt, peaked at the maximal molt and returned to pre- and post-molt levels. LH, E2 and progesterone declined during the molt, and the decline was coincident with the cessation of egg production. 3. 3. Thyroxine(T4), triiodothyronine(T3) and reverse triiodothyronine(rT3) increased during the molt. The increases of T4 and T3 were not abolished even if the forced molt was conducted in mild weather.

Pausa forzada y postura subsiguiente en gallinas de huevo marrón

En el Centro de investigación y Desarrollo de Lajas se hizo un estudio con gallinas ponedoras de peso mediano y huevo marrón de la línea Hisex para averiguar cómo diferentes sistemas de pausa forzada después de 10 meses de postura las afectaban en el segundo ciclo (año). La postura del segundo año, peso del huevo, transformación de alimento a huevo y pesos inicial y final no mostraron diferencias significativas (P=.05) entre los cuatro tratamientos. El T-4, con el que se forzó la pausa al retirar el agua 2 días y el alimento 12 días consecutivos, tuvo los resultados más pobres, pero casi idénticos a los del T-2, en el que consumieron alimento concentrado con 25,000 ppm de óxido de cinc 6 días consecutivos. El grupo testigo (T-1), el cual consumió alimento para ponedoras todo el tiempo, tuvo una postura y una transformación del alimento casi tan buenas como el T-3, con el que la pausa se forzó al retirar el agua 1 día y el alimento 6 días consecutivos. Todos los grupos aumentaron casi lo mismo de peso en el segundo ciclo (0.35 kg/año), a pesar de que a las gallinas se les restringió el alimento a la cantidad recomendada para gallinas ligeras Liornas Blancas, 114 g. (4 oz.) por día. Esta cantidad fue suficiente para sostener una buena y eficiente postura en gallinas de peso mediano y cascarón marrón en un ambiente tropical.

A Comparison of the Effect of Two Force Molting Methods on Performance of Two Commercial Strains of Laying Hens

A low-sodium diet (.08% Na) was used to force molt 409 hens. Another 421 hens were force molted by conventional water and feed restrictions. Birds were 68 weeks of age at that time, and two strains were about equally represented in each treatment group. These strains were: A, DeKalb; and B, Hisex. The low-sodium diet and water were provided ad libitum to the first group for the entire period of molt (42 days). The second group received no water for 3 days, and no feed for 4 days, after which incremental amounts of whole oats were provided as the only feed until Day 18. After Day 18, incremental amounts of a regular laying mash and decremental amounts of whole oats were provided through Day 26, when laying mash only was given ad libitum. Both treatment groups were in the same building and received the same lighting program during the force-molt period. This program consisted of: Days 1 to 3, no light; Days 4 to 18, 8 hr/day; Days 19 to 25, 9 hr/day; Day 26, 10 hr; then, light was increased 30 min weekly until 14 hr daily was attained. The low-sodium group ceased laying after 28 to 31 days, lost 8.7% of their premolt body weight, reduced feed consumption by 35%, and decreased egg production from 62.3% (in the 28 days preceding the molt) to 19% in the 42 days of molt; their mortality rate was 3.4%. The feed- and water-restricted group receiving oats ceased laying after 11 to 12 days, lost 17% of their premolt body weight, reduced feed consumption by 81%, and decreased egg production from 59.3% (in the 28 days preceding the molt) to 4.0% in the 42 days of molt; their mortality rate was 5%. Nearly all of the birds assigned to the feed and water restriction lost their feathers during the first 2 weeks; in contrast, hens receiving the low-sodium treatment lost their feathers at a much slower rate. No significant differences were observed between the two treatment groups in egg production, egg weight, interior egg quality, or shell quality during 10 subsequent, 28-day postmolt periods.Strain B stopped laying earlier and had a higher mortality rate than Strain A during the force-molt period. However, Strain B had a significantly higher (P<.05) egg production rate during the postmolt period of 280 days.

Feed Restriction During the Growing Period, Forced Molt, and Egg Production

An experiment was conducted to examine postmolt laying performance of White Leghorn hens that had been subjected to feed restriction from 8 to 20 weeks of age.During the postmolt period, birds in all forced-molt (FM) groups consistently had higher percent hen-day egg production than the control birds. Within the FM groups, birds that had previously been restricted fed during the growing period at the rate of 70% of the control group's consumption (R70 -FM) consistently had higher percent hen-day egg production during most of the postmolt period than the nonrestricted fed birds (Ad lib.-FM). Significant (P<.05) improvements in albumen height and shell thickness were observed 4 weeks after the FM period. When premolt, molt, and postmolt periods were combined, R70-FM birds had the highest percent henday egg production and the best feed efficiency of any group.

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.

Composition of Eggs by Commercial Size Categories: Effects of Genetic Group, Age, and Diet

Effects of genetic group, age, and dietary protein level on composition of eggs within the commercial size categories were studied in two Leghorn control strains formed in 1950 and 1958, two corresponding strains selected for high egg production and related traits, their reciprocal crosses, and a commercial Leghorn stock.Mean hen-housed egg production to 385 days was 154, 184, 197, and 191 eggs, and 385-day egg weight was 59.4, 63.1, 64.4, and 62.0 g for the control strains, selected strains, strain crosses, and commercial stock, respectively. In the eggs graded as large, wet and dry yolk weights, percent of yolk, and dry yolk/albumen ratio increased while wet albumen weight and percent of albumen decreased as dietary protein level increased from 15 to 19%. No such effects were observed in the medium or extra large eggs.Within each egg size category, wet and dry yolk weight and percent of yolk increased and wet and dry albumen weight, percent of albumen, albumen percent solids, and shell weight decreased with age. These trends were reversed by forced molting between the sixty-fourth and seventy-first weeks of age but they resumed afterwards.There was no heterosis for any egg composition trait and no genetic group effects on yolk percent solids. Within the same commercial size category, eggs of the control strains had lower albumen percent solids than those of selected strains or the commercial stock and contained more yolk and less albumen and shell. These differences reflect changes in the composition of the eggs from hens that have been under selection for increased production since the control strains were formed.

The Effects of Forced Molt Treatment on Blood Biochemicals in Hens

A study was conducted to determine the effects of an environmentally induced force molt treatment on concentrations and daily variations of selected serum biochemicals during early molt.Laying hens were placed into two environmental control chambers. In one chamber, control (Con) laying hens were maintained on long photoperiods of 19 hr of light daily to maintain egg production. In the other chamber, early molt (EM) hens were exposed to short photoperiods of 6 hr of light daily to decrease egg production. After 2 weeks in the chambers, feed was withdrawn from EM hens for 2 days to initiate molt. Three days after feed was restored, hens from both groups were blood sampled every 2 hr for 2 days for selected serum biochemical analyses.Serum concentrations of calcium (Ca), inorganic phosphate (P), glutamic pyruvic transaminase (GPT), and albumin (Alb) were depressed in EM hens. Serum concentrations of alkaline phosphatase (Alk P), lactic acid dehydrogenase (LDH), glutamic oxaloacetic transaminase (GOT), glucose (Glu), cholesterol (Chol), and globulin (Glob) were elevated in EM hens.Daily temporal rhythms of Ca, Glu, total protein (TP), and Alb were found in both hen groups. These temporal changes were independent of force molt treatment.Serum GOT was positively correlated with nuclei free liver corticosteroids (LCS) and negatively associated with plasma corticosterone in Con hens. Serum GOT was positively correlated with nuclei free LCS in EM hens.

Influence of Premolt Production on Postmolt Performance with Explanation for Improvement in Egg Production Due to Force Molting

Performance of force-molted hens as influenced by premolt production was determined in two experiments using 720 Babcock hens. Hens selected to be laying at a low (41%), average (59%), and high (75%) rate of production were divided into two groups. One half of the hens were force molted (FM) and the other half served as controls (CON). On completion of the fasting period, blood was collected for chemical analyses from 10 hens per group. These hens were then necropsied and weights of the ovary, oviduct, liver, and fat pad determined. During the last 4 weeks of the postmolt period, dietary calcium was increased from 3.5 to 4.5% in half of each group.Postmolt production was directly related to premolt production. The hens laying the highest rate premolt showed no improvement, whereas those laying at the lowest rate showed the greatest improvement. The FM hens exhibited a lower incidence of shell-less eggs than CON hens. Premolt production appeared to have little influence on postmolt egg weight, organ weights, and blood constituents. However, shell weight and egg specific gravity were significantly improved by force molting. Increasing dietary calcium had no significant influence on shell weight and specific gravity in FM hens in either experiment but significantly increased specific gravity and shell weight of CON hens during Experiment 2.It was concluded that most of the improvement in production in force-molted hens was caused by a reduction in shell-less eggs and not by an increase in ovulation. Also, only a portion of the improvement in shell quality could be explained by an increase in feed intake (calcium intake) after molting due to the increase in production. An improvement in calcium metabolism was postulated to be a major cause of improved shell quality.

The Effects of Forced Molt Treatment on Selected Steroids in Hens

A study was conducted to determine the effects of an environmentally induced forced molt on concentrations of plasma progesterone (P), corticosteroids (CS), corticosterone binding globulin binding capacity (CBGBC), and liver corticosteroids (LCS) during early forced molt.Laying hens were placed into two environmental control chambers. In one chamber, control (C) hens were fed ad libitum and maintained on long photoperiods of 19 hr of light daily to maintain egg production. In the other chamber, early forced-molt (EM) hens were exposed to short photoperiods of 6 hr of light daily to decrease egg production. After 2 weeks of ad libitum feeding, feed was withdrawn from the EM hens for 2 days to initiate a molt. Feed was restored for 3 days to the EM hens before hens from both groups were sacrificed every 2 hr for 2 days.The EM hens had regressed ovaries, greater body weight losses, lower plasma P and CS hormone levels, lower nuclei free LCS levels, and lower CBGBC than C hens. Nuclear LCS levels were similar in EM and C hens.A single peak indicating a daily rhythm of plasma P was found only in C hens. Progesterone secretions appeared to be eposodic in EM hens.A daily rhythm with two peaks of plasma CS and nuclei-free LCS was found in the C hens. Nuclear LCS peaked thrice daily in C hens. A cascade of CS from the plasma to the liver cytosol and on to the liver nucleus was indicated. Plasma CS was negatively correlated with nuclei-free LCS.Two daily peaks of plasma CS occurred in EM hens. One peak exhibited a daily rhythm and the other did not. Daily rhythmic peaks in EM hens were less defined than in C hens. Force molt treatment in EM hens may have affected the loss of the LCS peaks as was found in the C hens. No daily rhythms of CBGBC were found in either hen group.

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.

Effect of Gibberellic Acid on Production Characteristics of Aged and Force Molted Chickens in Cages

Production characteristics of individually caged 72-week-old brown egg type hens or 86-week-old hens of a similar strain that had previously been subjected to different watering systems (continuous flow cups vs. intermittent flow troughs) and the stress and recovery of a forced molting program were evaluated in two trials over a 4 to 5-week interval following 6 alternate day subcutaneous injections (2.4 mg/bird) of gibberellic acid (GA3).Egg production and feed consumption of the 72-week-old hens maintained at constant temperature (20.0 ± 1.0 C), humidity (55%), and light intensity (10.76 lx) were significantly greater (GA3 × time, P<.05) in the GA3 treated birds and were accompanied by significantly larger eggs (GA3 × time, P<.05) with generally thinner shells. In the second trial, the 86-week-old hens responded with similar trends but the differences were less and related in part to prior watering system. No statistically significant differences were found for egg production, feed consumption, and egg weight as previously observed, but there was significantly greater shell thickness of eggs from the GA3-treated birds previously adapted to cups as compared to trough waterers (GA3 × time × waterer, P<.025). No statistically significant effects of GA3 on body weight were observed in either trial.The data suggest that the differences in response between the two trials may be related to the initial differences in egg production and, thus, the levels of circulating gonadal hormones, since GA3 has been shown to have androgenic activity in chicks, and estrogenic as well as other hormonal activity in other species.

Physiological Changes in Caged Layers During a Forced Molt: 4. Leucocytes and Packed Cell Volume

Packed cell volume and circulating leucocyte numbers in force-molted, Single Comb White Leghorn (SCWL) hens were examined. Two groups of SCWL hens, reared under commercial conditions, were subjected to force molting (FM) at 70 (Trial 2) and 72 weeks of age (Trial 1). The force molting procedure consisted of a reduced photoperiod (6 hr), feed removal for 12 days (Trials 1 and 2), and water withdrawal for 1 day (Trial 1 only). Cessation of egg production was achieved in 6 days. Control (CON) hens were maintained in each trial with no change in daylength, and feed and water were available ad libitum.The FM hens exhibited a significant increase in packed cell volume (PCV) from the time of feed removal until immediately prior to resumption of egg production. This effect was not associated with water deprivation. The FM hens exhibited numerically increased numbers of total leucocytes (TWBC) and monocytes throughout the nonlaying period. However, the increase was significant on Day 14 of both trials for TWBC and on Days 21 and 35 (Trial 1) and Days 14 and 48 (Trial 2) for monocytes. A significant eosinophilia was observed on Days 7 and 14 of both trials. Changes associated with lymphocytes, heterophils, and basophils were inconsistent. Lymphocytes were increased significantly in the FM hens of Trial 2 from Day 21 to Day 48, but no significant difference occurred in Trial 1. A heterophilia was exhibited by the FM hens of Trial 1 on Days 7 and 14, but not in Trial 2. Conversely, a significant basophilia was observed on Days 7 and 14 in Trial 2, but not in Trial 1.These data suggested that an increased PCV, eosinophilia, and possibly increased TWBC and monocyte numbers were associated with a forced molt in caged SCWL hens.

Physiological Profile of Caged Layers During One Production Season, Molt, and Postmolt: Organ Weights and Blood Constituents

Single Comb White Leghorn (SCWL) hens were sampled at 3 month intervals during a production season, a forced molt, and for 2 months postmolt. At each sampling time serum and organ weights were obtained. Body weight, liver weight, ovary weight, oviduct weight, right adrenal weight, spleen weight, adrenal cholesterol, hematocrit, hemoglobin, serum glucose, serum cholesterol, and serum total protein were determined.An increase in body weight and stable relative organ weights were observed throughout the season as well as fluctuations of blood constituents due to age, reproductive status, environmental effects, and forced molting.

Physiological Changes in Caged Layers during a Forced Molt: 3. Plasma Thyroxine, Plasma Triiodothyronine, Adrenal Cholesterol, and Total Adrenal Steroids , , ,

The effects of forced molting on plasma levels of thyroxine (T4), triiodothyronine (T3), and adrenal cholesterol and total adrenal steroid content were studied. Commercially available strains of Single Comb White Leghorn (SCWL) hens, reared and maintained under commercial conditions, were used in the three trials. The hens were moved to environmentally modified facilities prior to the forced molt which was accomplished by reducing daylength and by withdrawing feed and water. Egg production ceased within one week of initiation of this procedure. The hens were sampled either daily or on alternate days for up to 22 days beginning at the time of feed removal.Plasma T4 initially decreased upon removal of feed, but increased above control levels by the sixth day of feed withdrawal. Plasma T3 levels remained relatively constant throughout the feed withdrawal period. Resumption of feeding with a fortified ground corn ration resulted in a decrease in T4 and concomitant increase in T3. Changes in adrenal cholesterol and total adrenal steroids were not consistent. However, there was a trend toward increased total adrenal steroids during feed withdrawal, and an increase in adrenal cholesterol upon the resumption of feeding.

Body-Checked, Misshapen, and Pimpled Eggs as Influenced by Force Molting

Two experiments were conducted to determine the influence of force molting on the occurrence of pimpled, misshapen, and body-checked eggs. Approximately 15,000 Babcock (Experiment 1) and 15,000 Honegger (Experiment 2) hens, 16 months of age, were force molted. Eggs were collected from approximately 2200 hens just prior to force molting and at 8, 13, and 24 weeks postmolt. The eggs were collected at 0600 hr and discarded. The eggs were then collected at 2 hr intervals from 0600 to 1800 hr and scored for pimpling, body-checks, and misshapenness.Most of the misshapen and body-checked eggs were laid between 0600 and 1000 hr, with very few being laid after 1000 hr. Force molting did not prevent or eliminate the misshapen and body-checked eggs. The degree of egg shell pimpling was significantly reduced by force molting in both experiments. Although the degree of egg shell pimpling increased during the postmolt, it was still significantly less at the end of the 24-week postmolt than during the premolt period. The Honegger hens had significantly less pimpling during the premolt and the 24-week postmolt periods than the Babcock hens. In summary, force molting significantly reduced the severity of egg shell pimpling but appeared to have little influence on misshapen and body-checked eggs.

Physiological Changes in Caged Layers During a Forced Molt: 1. Body Temperature and Selected Blood Constituents , , ,

The effects of forced molting on body temperature and selected blood constituents were studied. Caged layers, reared under commercial conditions, were force molted successively at 72 and 104 weeks of age. This was accomplished by removing feed for up to 12 days and water for up to 3 days while simultaneously reducing the daylength to 10 hr or less. This procedure resulted in a cessation of egg production within one week of the initiation of feed removal.There was a significant increase in body temperature during feather loss and renewal. Packed cell volume and hemoglobin increased significantly immediately upon removal of feed and water and remained elevated above control levels for the duration of the pause in egg production, while plasma total calcium, and inorganic phosphate decreased significantly during the corresponding period. Plasma total protein and plasma glucose did not exhibit consistent trends. Body temperature and the levels of the measured plasma constituents returned to normal levels upon the resumption of egg production.