Molting Treatments Research Articles

The effect of pre- and postmolt diets high in n-3 fatty acids and molt programs on skeletal integrity and insulin-like growth factor-I of White Leghorns

This study investigated changes in bone integrity and circulating concentrations of insulin-like growth factor-I (IGF-I) of hens subjected to 2 distinct molting regimens and fed pre- and postmolt diets high in n-3 or n-6 fatty acids. A dual-energy x-ray absorptiometer determined bone mineral density (BMD) of the tibia and humerus of 45 live hens from 62 to 76 wk of age. Densitometric scans were also conducted in excised tibia and humerus at 66, 71, and 76 wk of age. Concentrations of IGF-I were monitored using an homologous RIA at the same ages. The molting treatments consisted of 10 d of fasting + cracked corn for 7 d + pullet developer diet for 10 d or a nonfasting molt (wheat-middlings-based diet for 27 d). Five weeks prior to and after either molt treatment, birds were fed 1 of 2 diets containing dietary n-6/ n-3 fatty acids ratios of 0.6 or 8.0. At the end of the molt (71 wk of age), tibial BMD decreased 30% in fasted and 11% in nonfasted molt regimens, and the fatty acid content of the premolt diet had no effect on the decline in BMD. The BMD of the humerus also decreased during molt with the exception of hens subjected to a nonfasted molt and fed n-3 fatty acid diets in which their BMD values were similar to or greater (at 73 wk of age) than those of controls during the entire experimental period (treatment by bone by age, P < or = 0.0001). Induced molt affected circulating IGF-I concentrations (treatment by age interaction, P < or = 0.0001), and the response was the same regardless of molt regimen (fasting vs. nonfasting) or diet (n-3 vs. n-6 fatty acids). A decrease in IGF-I 54 h postmolt was noted; however, from 13 to 43 d postmolt, all molted birds had elevated IGF-I as compared with controls. In conclusion, a nonfasted molt as compared with fasted molt was less detrimental to bone mineralization; dietary n-6/n-3 fatty acid ratios in the pre- and postmolt diets had little effect on the decline of skeletal integrity during molt, and circulating IGF-I concentrations were affected by molt.

The effect of an induced molt using a nonfasting program on bone mineralization of white leghorns

To determine changes in bone mineralization during molt, 66-wk-old White Leghorns were assigned to either a fasted molting regimen using feed removal for 10 d, followed by the ad libitum consumption of cracked corn for 7 d and a pullet developer diet for 10 d or a nonfasted molting regimen lasting 27 d that included the ad libitum consumption of a diet containing 71% wheat middlings and 23% corn. Both molting regimens restricted light to 8 h/d, and water was provided ad libitum. At 28 d postmolt, hens from both molting treatments were returned to a regular egg-laying diet and 16 h/d of photoperiod. Control hens consumed a regular egg laying diet and were kept on 16 h/d of light throughout the study. Using dual-energy x-ray absorptiometry, bone mineral density (BMD) and bone mineral content (BMC) of the left tibia were measured in 7 live hens per treatment immediately prior to, during, and following the molt. Results showed that by 28 d postmolt, BW loss was 22 and 18% in the fasted and nonfasted molting regimens, respectively (P < or = 0.0001). Compared with premolt values, tibial BMD at 28 d postmolt decreased 35 and 18% in the fasted and nonfasted molt groups, respectively (treatment x age interaction, P < or = 0.0001). Similarly, tibial BMC values decreased 39 and 27% in the fasted and nonfasted molt groups, respectively (treatment by age interaction, P < or = 0.01). The tibial BMD and BMC of controls at 28 d postmolt were similar to premolt values. Recovery in tibial BMD and BMC of fasted and nonfasted hens occurred by 126 d postmolt with values similar to controls. These results suggest that a nonfasted molting regimen is less deleterious to tibial BMD and BMC than a fasted molting regimen.

Comparisons of molting diets on skeletal quality and eggshell parameters in hens at the end of the second egg-laying cycle

A study was conducted to evaluate skeletal quality and eggshell parameters of molted hens at the end of the second laying cycle. Sixty Single Comb White Leghorn hens were used for this study. There were 2 controls and 4 molting treatments: full-fed control 1 (82 wk old; FF1), full-fed control 2 (122 wk old; FF2), feed withdrawal (FW), 100% alfalfa (A100), 90% alfalfa/10% layer ration (A90), and 70% alfalfa/30% layer ration (A70). At the end of the second laying cycle (approximately 122 wk of age), hens were euthanized by CO2. Tibia and femur were collected. There were no differences in bone parameters between FF1 and FF2 (P > 0.05) hens. There were no differences in bone parameters among the different molting dietary treatments (P > 0.05). In the eggshell parameters, the FF2 hens exhibited heavier egg weights than the FF1 (P < 0.05), whereas the percentage shell and egg production of the FF1 birds were significantly higher than those of the FF2 birds. Shell weights of the FW and A90 birds were significantly heavier than that of the A100. The correlation analysis showed that overall bone parameters were negatively correlated with eggshell parameters. Bone parameters were highly correlated with each other. Shell weight, percentage shell, and shell thickness were positively correlated with each other, whereas egg weight was negatively correlated with percentage shell. These results suggest that age of hens and molting dietary treatments influence egg parameters, and eggshell formation is closely related to bone metabolism in laying hens.

The response of laying hens to induced molt as affected by strain and age

Molt was induced in 502-d-old Lohmann, Hy-Line W-77, Yafa, and Yarkon strains of laying hens (Experiment 1), and at different ages during the 1st yr of production in the Lohmann strain (Experiment 2). The induced molt treatment included an 8-d feed withdrawal period followed by a 22-d rest period during which the birds received 60 or 70 g/d of a low-nutrient maintenance diet, in both experiments, respectively, and a reduced duration of daylight. In both experiments, induced molt resulted in an increase in postmolt egg production rate and a diminution of the rate of decline of production with age. The first eggs during the postmolt period were smaller than those of the unmolted birds but egg size increased rapidly to control levels. Egg breakage was markedly reduced by induced molt and its rate of increase with age was diminished. Postmolt feed intake was higher than that of the unmolted birds and body weights reached values higher than those of the controls. Those responses were not different among strains but the ranking among the strains in the molted group was similar to that of the unmolted controls, for all production traits. The postmolt rate of production approached that of first cycle peak and was not affected by treatment age. Shell quality as reflected by the percentage of breakage during the postmolt period was similar to that of the unmolted controls approximately 3 to 4 mo earlier.

Effect of Two Different Molting Procedures on a Salmonella enteritidis Infection

Previous studies have shown that inducing a molt using feed removal exacerbated an intestinal infection by Salmonella enteritidis (SE). The current study was conducted to determine whether inducing a molt using a molt diet would still cause a pause in egg laying but not exacerbate an intestinal SE infection. In Experiments 1 and 2, hens were either provided ad libitum access to layer feed (control), fed 45 g molt diet (molt-feed) daily, or deprived of feed for 14 d (molted), and were orally infected with 1 × 107 SE on Day 4 of molt. Egg lay ceased in hens subjected to both molt treatments. The percentage of hens shedding SE did not differ among treatment groups in Experiment 1, whereas in Experiment 2 the molted hens had significantly higher shed rates than the controls on Days 10, 17, and 24 postinfection and the molt-feed hens on Days 17 and 24 postinfection. Compared with both fed groups of hens, the molted hens shed significantly more SE in Experiment 1 on Day 10 postinfection, and in Experiment 2 the molted hens shed significantly more SE on all 4 sampling days. In Experiment 3, subgroups of hens within each treatment group received serial 10-fold dilutions of SE and intestinal shedding of the organism in each subgroup was determined 7 d later. The 50% infectious dose (ID50) was calculated for each treatment group from these shedding results. The ID50 was 2.7 × 103 SE, 5.2 × 102 SE, and 1.3 SE for control, molt-feed, and molted hens, respectively, indicating that feed removal substantially increased the susceptibility of hens to an SE infection and the molt diet decreased this susceptibility. Little difference was observed in the pH of alimentary samples or of cecal contents from hens in each treatment group, indicating that increased severity of SE infection was not due to alterations of intestinal pH. Histologically, the molted hens exhibited more extensive inflammation of the intestinal tract at Day 4 postinfection compared with the unmolted group. Intestinal inflammation in the molt-feed hens was intermediate between the two. These results indicated that molt induction, using a molt diet, will not put hens at risk for the severe intestinal infection observed in birds subjected to feed removal.

The Effect of Feed and Water Withdrawal on Body Weight and Carcass Characteristics of Molted Turkey Breeders

In Experiment 1, turkey breeder hens from a randombred control line (RBC1) and a subline of RBC1 selected for increased egg production (E line) were exposed to one of four molting treatments: 1) decreased photoperiod and a shift from a breeder diet to holding diet, Control; 2) decreased photoperiod and no feed on Days 1, 2, 4, and 5, No Feed; 3) decreased photoperiod and no water on Days 1 and 2, No Water; 4) decreased photoperiod and a combination of Treatments 2 and 3, No Feed or Water. Control hens continued to lay following the molt but hens in each of the other treatments ceased egg production. Each feed withdrawal treatment resulted in a nonsignificant decrease in BW immediately postmolt, whereas hens in the Control and No Water treatments exhibited no change or a slight increase in postmolt BW. In both lines, the No Water treatment resulted in an increase in the relative amount of abdominal fat and in E-line hens this treatment also increased relative liver weight. The relative weight of the oviduct was significantly decreased by the No Feed and No Feed or Water treatments compared with the Control and No Water treatments. The loss in oviduct weight was accompanied by a significant decrease in oviductal protein concentration with no change in dry matter content.In Experiment 2, commercial turkey hens were deprived of feed for 7 days with ad libitum access to water. There were no differences in BW at the start of the molt (PRE) in comparison to 14 days following a return to ad libitum feeding (POST). In comparison to the PRE sampling, liver weight was increased and abdominal fat and oviduct weights were decreased at the POST sampling. At second cycle photostimulation, BW and liver weight were increased compared with the PRE sampling whereas abdominal fat did not change. The oviduct did not return to premolt size until 28 days following second cycle photostimulation.

Research Note: Induced Molt Increases Eggshell Quality and Calbindin-D28k Content of Eggshell Gland and Duodenum of Aging Hens

Aged laying hens, which were induced to molt by fasting to a 30% loss of their original body weight or by administration of a diet containing 2% zinc as zinc oxide, experienced reproductive involution and cessation of egg production. Both of the molting treatments resulted in improvement of eggshell density by time of oviposition of the 10th egg after the return to egg production postmolt. Both molting treatments significantly increased the amount of calbindin in the shell gland and duodenum of molted hens as compared with control hens at the 10th egg after return to egg production postmolt.

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.

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.

Starvation and Its Effect on Semen Quality

THE practice of force molting hens has been studied over a long period of time and under various molting programs. Most of these programs employed some form of starvation.A review of the literature does not indicate that force molting procedures have been tried with the male. The object of these trials was to determine the effect of starvation on semen production, sperm quality, and feather molt.METHODS AND PROCEDUREIn the first of two trials, three groups of White Plymouth Rock males, 3, 2, and 1 year of age, were maintained in single bird cages (61 × 61 × 61 cm.) in a house with natural daylight. A randomized complete block design, with families (usually full sibs) as blocks, was used with the control and force molt treatments assigned at random to each age group within a family. A total of 10 families was used.At the beginning of…