Molting In Hens Research Articles

Effects of different litter substrates and induced molt on production performance and welfare quality parameters of white Leghorn hens housed in multi-tiered aviary system.

More than 90% of the commercial egg production in the United States is pledged to be in cage-free systems by 2025. Management practices like induced molting and litter area management have come under scrutiny because of the housing system change. The aim of this study was to determine the welfare and production implications of different litter substrates and also evaluate induced molting of hens in a cage-free system. Bovan White hens were housed in a multi-tier aviary system with daily access to open litter area of either Astroturf (AT), wood shavings (SH), or straw (ST) and bare concrete floor (CO) serving as control. At 68 wk of age, molt was induced in half of the hens whereas the other half continued without molting to 116 wk. Production and welfare parameters were measured periodically throughout first and second cycles. Litter substrate did not influence hen-day production and case-weight measurements. However, CO had the lowest total number of eggs produced during the first cycle (P < 0.05). Hen-day percentage was approximately 14% greater in molted hens during the second cycle with egg case weight being heavier in non-molt hens toward the end of second cycle (P < 0.05). The only welfare parameter influenced by litter substrate during the first cycle was a greater crop feather loss in AT than ST at mid-lay (P < 0.05). Keel deformations increased with age irrespective of the litter substrate with 91.5% of palpated hens having keel deformations at the end of first cycle (P < 0.05). Molting did not influence the keel palpation and footpad scores whereas frequency of moderate comb wound was greater in molt hens during molt (P < 0.05). Severe feather loss was seen in non-molt hens during the second cycle (P < 0.05). Litter substrate does not affect production and physical parameters of welfare of hens in a multi-tier aviary system. Additionally, induced molting can be successfully carried out in the multi-tier cage-free system.

Comparison of fatty acid, cholesterol, vitamin A and E composition, and trans fats in eggs from brown and white egg strains that were molted or nonmolted

The impact of egg color, hen strain, and molting on the nutritional composition of eggs is limited. Therefore, this study compared nutritional composition and component percentages of cage-produced shell eggs with respect to egg color, hen strain, and molt. Four strains were selected from the North Carolina Layer Performance and Management Test: Hy-Line Brown (HB) and Bovans Brown (BB), and Hy-Line W-36 (HW) and Bovans White (BovW) were selected. Two groups from each strain were selected and 2 groups of molted HW and BovW were selected and compared with their nonmolted counterparts to examine the molt's impact. Two sets of eggs from each replicate were collected simultaneously at 101 wk of age. One sample of eggs was broken into a 12-egg pool stomached for 3 min (n = 12 samples), then divided into six 50-mL tubes, sealed, and frozen to be sent for cholesterol, n-3 fatty acids, saturated fat, monounsaturated fats, polyunsaturated fats, β-carotene, vitamin A, and vitamin E analyses. The other set of 12 eggs was then assessed for component percentages. The HW eggs had a greater (P < 0.05) percentage of yolk than the BovW eggs of 28.12 versus 27.00%, respectively; however, the BovW eggs had 1.0% more albumen. The HB and BB egg components were not different. Brown eggs were heavier (P < 0.01) than white eggs. White eggs had greater (P < 0.0001) percent yolk and the brown eggs had greater (P < 0.0001) percent albumen. The eggs from molted hens had a greater (P < 0.001) percent shell. Total fat content in the samples was (P < 0.05) higher in white eggs by 0.70% than brown eggs due to increased saturated and polyunsaturated fats. The molting of hens reduced (P < 0.01) saturated fats by 0.21% in the egg. Vitamin A levels were higher (P < 0.0001) in white eggs, and vitamin E was higher (P < 0.0001) in brown eggs. Strain and molt appear to influence nutrient composition and component percentages in eggs produced from laying hens.

The effects of a short-term molt method using cassava meal, broken rice, or corn on ovarian regression, bone integrity, and postmolt egg production and quality in older (95 week) laying hens

This study was conducted to determine the ability of different molt diets to induce molt in 95-wk-old hens. The hens were randomly assigned to 4 treatments of 60 birds each: 1) molted by full feeding with broken rice (BROK), 2) corn (CRN), 3) cassava (CASS), or 4) nonmolted control (CONT) for 14 d. At 15 d, all hens were fed a layer diet (17% CP), and production performance was measured for 20 wk. Feed intake was depressed (P < 0.05) in the CASS treatment compared with BROK and CRN treatments during the 14 d. The most significant BW loss occurred in the CASS treatment (21.9%), whereas BROK and CRN treatments were 7.6 and 9.3%, respectively. The CASS treatment resulted in total cessation of egg production within 7 d, whereas those of BROK and CRN treatments decreased to 3.7 and 8.7%, respectively. Ovary weights, oviduct weights, and oviduct lengths of the CASS treatment were not significantly different from those of BROK and CRN treatments (P > 0.05). The weight of spleen and thymus glands, blood heterophil:lymphocyte ratios, bone parameters, and mortality during the 14-d treatment were not affected by treatments. No significant differences were found among treatments for postmolt cumulative egg production, egg weight, feed intake, and mortality. Significant (P < 0.05) improvements in albumen quality were observed in the CASS treatment, although shell thickness of this treatment was reduced (P < 0.05) compared with the CONT treatment in wk 2 after the 14-d treatment. With respect to shell ultrastructural traits, the palisade layer of CASS eggs was shorter (P < 0.05) than that of CONT eggs determined in wk 2 after the 14-d treatment. In addition, evidence of abnormal mammillae was detected in an egg produced by the CASS hens. This research indicates that cassava diets can induce molt in hens. Nonetheless, the technique needs to be adjusted to improve postmolt egg production and shell quality.

Alfalfa as a nutritive modulator in maintaining the innate immune response during the molting process

Forced molting of laying hens increases enteric foodborne pathogens in the reproductive tract, leading to contaminated eggs and progeny of infected hens. Currently, we lack a complete understanding of how conditions such as molting affect the immune system. Previous reports have shown that alfalfa is effective in inducing a molt as well as in producing protection against Salmonella Enteritidis organ invasion. Our laboratory has also shown that immune functions are significantly reduced during molting. The present investigation evaluates a specific parameter of immune function, heterophil function, during an induced molt in hens fed alfalfa. Three replicate experiments used hens older than 65 wk of age that were divided into 6 groups of 12 hens each and placed in individual laying cages. Two weeks before dietary changes, hens were placed on an 8L:16D photoperiod that continued for the 12-d experiment. Peripheral blood samples were taken from hens on d 0, 2, 6, and 12 of molt. Hens were randomly placed into 3 treatment groups: nonfed hens, fully fed hens, and alfalfa-fed hens. To evaluate heterophil functions, the production of an oxidative burst as well as cellular degranulation assays were performed. In addition, total and differential peripheral blood leukocyte counts were performed. When compared with the nonfed control, alfalfa-fed birds showed significantly (P < 0.05) higher oxidative burst and degranulation activities. The data confirm previous observations that heterophil functions are significantly decreased in nonfed birds and the data show that birds fed alfalfa had numerically increased heterophil functions over a 12-d molting period when compared with heterophils of nonfed controls. Commercial integrators should consider using alfalfa when developing new molting programs.

Effect of melengestrol acetate as an alternative to induce molting in hens on the expression of yolk proteins and turnover of oviductal epithelium

Inducing hens to molt increases egg quality, egg production and extends the productive life of hens. It has been previously demonstrated that melengestrol acetate (MGA), an orally active progestin, decreased gonadotropic support for the ovary, which decreased the steroidogenic support for the oviduct and resulted in the cessation of lay. Estradiol produced by the theca cells of small follicles stimulates the production of the yolk proteins vitellogenin II and apolipoprotein II by the liver and supports the oviductal epithelial cells. The objective of the present experiment was to determine gene expression for yolk proteins and oviductal epithelial cell turn-over in response to a MGA-induced molt. Hy-Line W-36 laying hens were fed either 0 or 8 mg MGA per day for 28 days in a balanced diet and then returned to a standard layer ration until day 36. Four birds per treatment on days 1, 8, 16, 28 and 36 were euthanized and the liver was removed and snap frozen in liquid nitrogen until RNA was extracted. Expression of vitellogenin II and apolipoprotein II genes was determined using real-time RT-PCR. A portion of the magnum was removed to determine proliferation and programmed cell death for secretory and ciliated luminal epithelium. Vitellogenin II and apolipoprotein II gene expression was reduced in hens fed 8 mg MGA compared to those fed 0 mg MGA. There was no effect of day on gene expression of either yolk protein. Cell proliferation was increased in the ciliated epithelial cells of the oviduct in hens receiving 8 mg MGA compared to those receiving 0 mg. However, programmed cell death of the ciliated epithelial cells was not different between controls and MGA treatment. Programmed cell death and proliferation increased in the secretory epithelial cells in hens receiving 8 mg MGA compared to controls. Therefore, utilizing MGA as an alternative method to induce molt results in some, but not all, of the physiological changes previously described for hens molted by feed withdrawal. These findings lead us to suggest that some of the observed physiological changes resulting from feed withdrawal are required to increase egg quality and egg production following molt and other changes are not necessary, but are just a result of nutrient deprivation.

Effects of Induced Molting on the Well-Being of Egg-Laying Hens

Induced molting in egg-laying hens is an important method for maximizing hen egg production and quality as well as hen health in commercial settings; however, there is growing societal concern over its effects on hen well-being. Using individual hens as their own controls, this research examined the behavior of hens subjected to different treatments of induced molting under premolt, molt, and postmolt conditions. Cage pecking increased in fast-induced subjects and aggression increased in fast-induced and nonfast-induced subjects during the molt. Gakel calling and several aspects of its acoustic structure were much higher during the molt condition in fast-induced subjects only. These data suggest that nonfast-induced molting treatments provide an effective method for inducing molting in hens and improving their well-being by minimizing discomfort due to food deprivation. In addition, these data further support that gakel vocalizations in hens may serve as an effective indicator for assessing well-being in a species otherwise behaviorally stoic in expressing stress or discomfort.

Changes in eggshell mechanical properties, crystallographic texture and in matrix proteins induced by moult in hens

1. The effect of moult on eggshell mechanical properties, on composition and concentrations of organic matrix components and on eggshell microstructure was investigated. The observed changes were studied to understand the role of organic matrix and eggshell microstructure in eggshell strength. 2. Moult was induced by zinc oxide (20 g zinc/kg diet) in 53 ISA Brown laying hens at 78 weeks of age. No difference was observed for egg or eggshell weights after moult. In contrast, moult improved the shell breaking strength (28·09 vs 33·71 N). 3. After moult, there was a decrease in the average size of calcite crystals composing the eggshell and in their heterogeneity, whereas crystal orientation remained basically the same. 4. After moulting, the total protein concentration in eggshell increased slightly. The comparisons of SDS-PAGE profiles of the organic matrix constituents extracted before and after moulting showed changes in staining intensity of certain bands. After moult, bands associated with main proteins specific to eggshell formation (OC-116 and OC-17) showed higher staining intensity, while the intensity of the egg white proteins (ovotransferrin, ovalbumin and lysozyme) decreased. ELISA confirmed the decrease in ovotransferrin after moult. Its concentration was inversely correlated with breaking strength before moult. 5. These observations suggest that changes in eggshell crystal size could be due to changes in organic matrix composition. These changes may provide a mechanism for the improvement in shell solidity after moulting.

Changes in the mRNA Expression of TGF&amp;beta; Receptor Types II and III in the Anterior Pituitary during Induced Molting in Hens

The goal of this study was to determine whether TGFβ receptors mRNA were expressed in the chicken anterior pituitary, and their expressions were changed during induced molting by the regulation of feeding. White Leghorn laying hens were subjected to induced molting. The anterior pituitary tissues were collected from hens of pretreatment (PT), 3d after withdrawal of feeding (3DWF), 1d and 5d after the resumption of feeding (1DRF and 5DRF, respectively), and on the day of resumption of egg-laying (RL). They were processed for semi-quantification of TGFβ receptors type II (TβRII) and type III (TβRIII) mRNA expressions by reverse transcription-polymerase chain reaction (RT-PCR). The TβRII and TβRIII mRNA expressions were observed in the anterior pituitaries in all groups of hens. The expression of TβRII and TβRIII βmRNA significantly declined in the 1DRF hens and recovered by the resumption of laying. These results suggest that TGFβs may play role as a local regulator of the glandular cell population and/or differentiation during induced molting.

Cell proliferation in the process of oviducal tissue remodeling during induced molting in hens

Tissue remodeling and calcium binding protein-D28K (CaBP-D28K) dynamics were examined in the oviduct relative to induced molting. The oviducal tissues of premolting, 7, 10, 13, and 16 d after cessation of laying, and postmolting hens were examined. Frequency of proliferating cells and immunoreactive CaBP-D28K molecules were identified by immunocytochemistry for proliferating cell nuclear antigen (PCNA) and Western blot for CaBP-D28K. The relative frequency of PCNA-positive cells in the mucosal epithelium of the magnum, isthmus, and shell gland was low in premolting and 7 d after the cessation of egg laying. In the magnum and isthmus it was markedly increased in 10 and 13 d after cessation, followed by a slight decrease at 16 d after cessation. The frequency in the shell gland was kept high 10, 13, and 16 d after cessation. The frequency of PCNA-positive cells in each segment was decreased when the birds resumed laying. In the stroma of magnum and isthmus where the tubular glands were located, the frequency of PCNA-positive cells was significantly increased 10 d after the cessation of egg laying relative to premolting and 7 d after cessation. In postmolting hens and in hens 16 d after cessation, the frequency was decreased to a same level to that of premolting hen. In the shell gland, the frequency of PCNA-positive cells was high at 10, 13, and 16 d, and diminished in postmolting hen. Single immunoprecipitate band for CaBP-D28K was observed in the shell gland of premolting, postmolting, and younger hens, whereas the density of bands was greater in postmolting hens and younger hens than in premolting hens. We suggest that the oviducal tissues are remodeled by replacing the old glandular cells with new ones that are derived from the mucosal epithelium and uninvoluted glandular cells. Such rejuvenation of shell gland tissue may lead the improvement of CaBP-D28K induction.

Changes in the population of proliferating cells in chicken anterior pituitary during induced molting: an immunocytochemical analysis for proliferating cell nuclear antigen

The goal of this study was to determine whether cell proliferation is increased in the anterior pituitary during an induced molting period in chickens. The anterior pituitaries were collected from: 1) laying hens before initiation of an induced molt (control hens), 2) molting hens 2 to 16 d after cessation of lay, and 3) second cycle laying hens 1 d after returning to lay. Pituitary cephalic and caudal lobes were processed for immunocytochemistry of proliferating cell nuclear antigen (PCNA), and positive cells were counted by an image analyzer using light microscopy. In cephalic and caudal lobes, a small number of positive cells were observed in controls and molting hens 2 d after cessation of lay. The frequency of PCNA-positive cells started to increase from 7 d after cessation of lay (3 d after refeeding), and a significantly higher frequency of positive cells was observed in both lobes of molting hens 13 d after cessation of lay when compared to control hens, molting hens 2 d after cessation of egg lay, and second cycle laying hens. The frequency of PCNA-positive cells in second cycle laying hens decreased to a similar level to that of control hens. These results suggest that anterior pituitary tissue may be remodeled partially by a proliferation of cells during induced molting in hens.

Effect of Induced Molting on the Course of Infection and Transmission of Salmonella enteritidis in White Leghorn Hens of Different Ages

Previous work in the authors' laboratory had shown that inducing molt using a 2-wk feed removal protocol in 58- to 84-wk-old White Leghorn hens increased the severity of intestinal infection by Salmonella enteritidis (SE). As susceptibility to infection can be influenced by age, a study was conducted to compare the effect of the feed removal on infection by SE in 20-, 40-, and 74-wk-old hens. Birds were orally infected with 5 to 10 × 106 SE on Day 4 of fast and were sampled for SE shedding 3, 10, 17, and 24 days later. Significantly higher numbers of SE were shed in fasted birds on Day 3 (20 and 40 wk of age), Day 10 (40 and 74 wk of age), and Day 17 (74 wk of age). Transmission of SE to uninfected, contact-exposed birds was observed in all three trials for both the fed and fasted groups. However, significantly more fasted contact-exposed birds became positive for SE on Day 3 (20-wk-old), Day 10 (74-wk-old), and Day 17 (74-wk-old). Significantly more SE was also shed in these fasted contact-exposed birds on Day 3 (20-wk-old), Day 10 (all age groups), and Day 17 (74-wk-old). The current results indicate that the fasting conditions used to induce a molt in hens increase the shedding of SE in direct-infected and contact-exposed hens and this effect does not appear to be affected by age.

The Effect of Clomiphene Citrate in Chickens: 2. Gonadotropic Activity

Clomiphene is a synthetic, non-steroidal compound composed of a mixture of the cis and trans isomers.Experiments were conducted to determine the gonadotropic activity of clomiphene, cisclomiphene and transclomiphene in Single Comb White Leghorn chickens.Clomiphene significantly increased comb size in immature pullets and increased testes weight in immature cockerels when injected for 8 weeks. It produced no significant comb stimulating effect in cockerels or ovariectomized pullets. These results indicated the necessity of the ovary for clomiphene to exert its comb stimulating effect in pullets.Clomiphene significantly increased early egg production in pullets when fed for approximately 8 weeks prior to the beginning of production. High dietary levels administered for 1 week produced a severe reduction in egg production and a heavy molt in hens. Clomiphene appeared capable of either stimulating or inhibiting gonadotropic activity in chickens depending on the level administered. It is believed that clomiphene probably acts at the hypothalamic-pituitary level.Neither cisclomiphene nor transclomiphene was as effective as clomiphene in producing gonadotropic effects in chickens under the conditions of these experiments.

Effect of 2-Acetamido-5-Nitrothiazole on Egg Production, Fertility, Hatchability, and Weight Gains in Chickens

WITH the increasing economic importance of enterohepatitis in chickens, it was considered important to determine the activity in this species of agents currently used in turkeys. Hudson and Pino (1952) reported sexual suppression and regression in chickens during administration of 2-amino-5-nitrothiazole, and found (1953) that approximately 10 weeks were required for recovery from drug effects. These studies were carried out in the laboratory, in birds held individually in cages. The drug was fed to 12-or 13-week-old birds at concentrations of 0.1 percent continuously for 2 weeks and 0.05 percent for the third week, or at 0.05 percent continuously throughout a 25-week experiment. Robblee and Clandinin (1954) found that the drug induced moult in hens that had reached the end of their first laying year when fed at a level of 0.1 percent for “a suitable period of time.” However, mortality and loss of body weight were reduced and subsequent egg …