Effects of Declawed Males on Laying Performances, Egg Quality Characteristics and Feather Cover of Layer Breeders in the Mating Cage

Yan Li1, Kai Zhan1,*, Junying Li1, Wei Liu1, Ruiyu Ma1, Shengnan Liu1, Haijun Cui1 and Xin Zhang2

1Institute of Animal Husbandry and Veterinary Medicine, Anhui Academy of Agricultural Sciences, Nongkenan Road No. 40, Hefei, 230031, China

2Jiangxi Huayu Poultry Breeding Co. Ltd., Yichun, 336299, China

ABSTRACT

This study aimed to investigate the effects of declawed males on laying performances, egg quality characteristics and feather cover of layer breeders in the mating cage. Ninety-six 230-day-old Hy-line Brown roosters were randomly split into four groups. Group 1 chicks served as intact control. Trimming of claw of group 2 chicks was performed by the method of partial amputation of the third toe (along the distal phalanx) at day of hatch; the first and third toes were declawed in the group 3, while the second and fourth ones were trimming in group 4. They were caged with the same batch of non-declawed hens. Compared with intact control, laying rate was significantly increased in groups 3 and 4, while percentage of defective eggs was visibly decreased in group 3. Hatching experiment showed a considerable depression in egg fertility and hatchability of setting eggs in group 4. Egg quality analysis demonstrated the significant increases in shell thickness among declawed treatments and yolk color in group 2. Overall feather score of layer breeders was not a significant difference, but the neck region had the lowest feather score in all groups. Preferential trimming methods were the removal of the first and third or second and fourth toes of day-old chicks in Hy-Line strain.

Article Information

Received 16 January 2017

Revised 02 March 2017

Accepted 25 March 2017

Available online 17 August 2018

Authors’ Contribution

KZ conceived and designed the entire experimental plan. JL, WL, RM and SL participated in egg quality analysis and scoring of the plumage. HC and XZ provided essential experimental animals and site. YL performed the animal trails, finished the statistical analysis and drafted the manuscript.

Key words

Laying performance, Declawed

male, Egg quality, Feather cover, Mating cage.

DOI: http://dx.doi.org/10.17582/journal.pjz/2018.50.5.1903.1908

* Corresponding author: zhankai633@126.com

0030-9923/2018/0005-1903 $ 9.00/0

Copyright 2018 Zoological Society of Pakistan

Introduction

 

Chicken claw, a curved and pointed appendage at the end of a toe, can grow to be greater with the increase of age. Its excessive growth could cause many deleterious effects on chicken grown and production, including stress, physical injury (sores and scratches) or death of the bird, excoriation on the feeder’s hands and inconvenience of feeding and management. One of the potential solutions is the prevention or restriction of claw growth.

Toe claw removal, alternately termed declawing, claw trimming or claw reduction, is usually done in combination with debeaking using a hotblade debeaker or microwave energy at one day of age. There is increasing evidence that effective declawing may be beneficial to chicken production performances. Hill (1975) and Hansen (1976) reported that claw trimming abated physical injury to the female during mating. Compton et al. (1981) and Gildersleeve et al. (1981) demonstrated that claw reduction ameliorated stress and reduced hysteria, and claw-trimmed birds had been found to be less fearful. Martin et al. (1976) and Compton et al. (1981) noted that claw reduction significantly increased rate of egg production, elevated feed conversion and enhanced livability. Moreover, other researchers also stated that claw removal promoted sexual maturity, ameliorated the feather condition (Compton et al., 1981; Ruszler and Quisenberry, 1979) and decreased contamination of eggs (Tauson, 1986). From this body of data it appears that claw reduction has a positive influence on productive and other performances. However, few studies were reported on the effects of declawed male on laying performances, egg quality characteristics and feather cover of layer breeder in the mating cage. Accordingly, the purposes of the current study were to investigate the declawing effects on layer breeders to make an objective evaluation of the management practice.

 

Materials and Methods

 

Animals and experimental design

A sufficient number of birds (Hy-Line Brown parent stock breeders) employed in this study were obtained from Jiangxi Huayu Poultry Breeding Co. Ltd. (Yichun, Jiangxi Province). All birds were debeaked and weighed at one day of age. The male chicks of similar body weight were divided equally into four groups. Group 1 chicks served as intact control. Trimming of claw of group 2 chicks was performed by the method of partial amputation of the third toe (along the distal phalanx) using a hotblade debeaker; in group 3 chicks, the first and third toes; in group 4, the second and fourth toes. Selection of toes for claw removal was based on those completely removed in male chicks. At 90 days (normal age for caging breeder), all roosters and the same batch of non-declawed hens were transferred to 3-tier mating cages (240 cm length × 120 cm width × 80 cm height) and each cage contained 52 breeders (male/female ratio, 1:12). 6 cages in each group were selected to measure performance parameters of the layers. Feed was supplied in mash form and dietary nutrient concentration was presented in Table I. The entire experiment was started at day 230 and lasted for 40 consecutive days. All birds were managed according to the guidelines in the Hy-Line parent stock Management Guide. Animal care protocols and experimental procedures in this study were approved by the Animal Care and Use Committee of the Anhui Academy of Agricultural Sciences (approval number A11-CS06; date of approval 21 September 2011).

 

Table I.- Dietary nutrient concentration for production period.

Ingredients	Nutrient concentration
Metabolizable energy (MJ/kg)	12.14
Crude protein (%)	17.48
Lysine (%)	0.87
Methionine (%)	0.43
Methionine+cystine (%)	0.71
Isoleucine (%)	0.67
Threonine (%)	0.66
Tryptophan (%)	0.20
Arginine (%)	0.89
Valine (%)	0.77
Linoleic acid (%)	0.97
Calcium (%)	3.98
Phosphorus (%)	0.45
Sodium (%)	0.17
Chloride (%)	0.17

 

Measurements of laying performances and mortality

The performances of laying hens including hen-day egg production, defective eggs (misshapen eggs, grosscracked, broken, softshell and shell-less eggs, excessively small or large eggs) and the number of dead birds were recorded by cage daily. Laying rate, percentage of defective eggs and mortality were calculated by recorded performance parameters. Afterwards, freshly qualified eggs were collected and incubated in commercial layer hatcheries under the same incubation conditions. Qualified eggs were accepted with the criteria as: similar in size and shape, clean and smooth surface, oval shape with a small end and a big end. The number of fertilized eggs and live chicks and day-old weight were counted for calculation of hatchability of fertile eggs, percentage of healthy pullets, male-to-female ratio, rate of water loss and average chick hatching weight.

Egg quality analysis

Given the nutritional and economic importance of egg quality, major quality parameters of eggs were measured in 30 eggs per group at the end of the experiment: egg weight, egg shape index, shell color, shell strength, shell thickness, shell weight, albumen height, Haugh units, percentage of yolk, yolk color. Egg weight, albumen height, yolk color and Haugh units were measured using automatic egg multitester equipment (EMT-5200, Robotmation Co. Ltd., Tokyo, Japan) according to the manufacturer’ s instructions. Shell color was determined on the large end, equatorial region, and small end, respectively, using a reflectometer (PRS-Evans Electroselenium Ltd., Halstead, Essex) on a scale of 0 (black) to 79.9 (white). The average of the 3 measurements was used as an eggshell color. Length and width (mm of each egg were gauged with a digital vernier caliper (LRY1202, Shanghai LiangRen Tools Co., Ltd., Shanghai, China) and egg shape index were calculated as a percentage according to the formula: [(egg width /egg length × 100]. Shell strength was measured using an Eggshell Force Gauge (EGG-0503, Robotmation CO., Ltd, Tokyo, Japan) and shell thickness using a shell thickness meter (ESTG-1, ORKA Food Technology Co. Ltd. Ramat Hasharon, Israel) with three measurements made from locations at the bottom, top and middle of each egg. Yolk was separated and weighed for calculation of percentage of yolk.

Feather score

Feather score was evaluated using an established 4-point scale (Tauson, 1986). The best feather score was defined as 4 and the nearly denuded skin as 1. The scoring system was applied to the neck, breast, back, wings and tail as follows; score 4, for a part of the body with smooth and perfect plumage; score 3, for a part of the body where feathers have slightly damaged, but with no or only very small denuded spots; score 2, for a part of the body that displayed larger denuded spots or with serious deterioration; score 1, for a part of the body having heavily destroyed feathers with denuded spots with injury to skin. At the end of the experiment, a total of 30 (15 male and 15 female) birds per group were randomly scored. Finally, the average feather score for each individual part of the body and an overall average score were calculated.

Statistical analysis

Statistical analysis was carried out using Origin Pro 8.0 software (OriginLab Corporation, Northampton, USA). All data were analyzed with one-way analysis of variance (ANOVA) followed by the Tukey’ s post hoc test for multiple comparisons. The results were presented as mean ± standard error of the mean (SEM). Means with different superscript letter are significantly different (P<0.05).

 

Results

 

Laying performances and mortality

Laying performances and mortality in all four groups were presented in Table II. Compared with intact control, laying rate was significantly increased in groups 3 and 4, while the percentage of defective eggs was visibly decreased in group 3 (P < 0.05). However, no remarkable differences were found in mortality (P > 0.05). Moreover, hatching experiment showed a considerable depression in egg fertility and hatchability of setting eggs in group 4 (P < 0.05), but other parameters did not change substantially in terms of hatchability of fertile eggs, percentage of healthy pullets, male-to-female ratio, rate of water loss and average chick hatching weight (P > 0.05).

 

Table II.- Effects of declawed males on laying performances and mortality of Hy-Line Brown layers in the mating cage.

Parameters	Group 1	Group 2			Group 3		Group 4
Laying performances
Laying rate (%)	83.32±0.62a	85.12±0.52a		87.62±0.60b		89.92±0.68c
Defective eggs (%)	1.36±0.13a	1.13±0.11a		0.95±0.09b		1.40±0.12a
Mortality
Rooster (%)	0.00±0.00a		0.00±0.00a		0.00±0.00a		0.00±0.00a
Hen (%)	0.35±0.35a		0.35±0.35a		0.69±0.44a		1.04±0.71a
Hatchability performances
Fertility (%)	95.11±0.29a		94.38±0.22a		95.27±0.22a		92.47±0.32b
Hatchability of setting eggs (%)	91.35±0.35a		90.09±0.37a		91.10±0.35a		88.65±0.40b
Hatchability of fertile eggs (%)	96.04±0.22a		95.47±0.32a		95.62±0.23a		95.87±0.25a
Percentage of healthy pullets (%)	95.94±0.50a		96.96±0.45a		96.55±0.50a		95.87±0.51a
Male-to-female ratio (%)	103.03±3.06a		100.99±3.47a		102.00±3.24a		99.57±2.62a
Rate of water loss (%)	12.15±0.19a		12.12±0.2a		12.01±0.27a		12.42±0.55a
Average chick hatching weight (g)	41.99±0.17a		41.80±0.18a		41.35±0.28a		41.88±0.22a

All roosters and the same batch of non-declawed hens were reared to 3-tier mating cages and each cage contained 52 breeders (male/female ratio, 1:12). 6 cages in each group were selected to measure laying performances and mortality of the layers. The entire experiment was started at day 230 and lasted for 40 consecutive days. Means with different superscript letters are significantly different (P < 0.05).

 

Table III.- Effects of declawed males on egg quality characteristics of Hy-Line Brown layers in the mating cage.

Egg quality	Group 1	Group 2	Group 3	Group 4
Shell strength (kg/cm2)	4.31±0.17a	4.30±0.14a	3.96±0.21a	3.91±0.19a
Shell color	25.77±0.60a	26.31±0.60a	26.01±0.49a	25.72±0.75a
Egg shape index	1.27±0.01a	1.29±0.01a	1.28±0.01a	1.27±0.01a
Shell weight (g)	7.60±0.11a	7.85±0.12a	7.42±0.14a	7.63±0.11a
Egg weight (g)	60.81±0.62a	63.01±0.89a	61.05±0.95a	61.30±0.64a
Shell thickness (mm)	0.35±0.01a	0.39±0.01b	0.38±0.01b	0.38±0.01b
Percentage of yolk (%)	25.84±0.28a	25.83±0.29a	26.24±0.33a	25.95±0.28a
Albumen height (mm)	7.66±0.12a	7.72±0.21a	7.89±0.18a	7.83±0.17a
Yolk color	7.22±0.16a	7.98±0.15b	7.47±0.12ab	7.47±0.16ab
Haugh units	87.53±0.80a	86.74±1.35a	88.41±1.06a	88.01±1.02a

Major quality parameters of eggs (shell strength, shell color, egg shape index, shell weight, egg weight, shell thickness, percentage of yolk, albumen height, yolk color and Haugh units) were measured in 30 eggs per group at the end of the experiment. Means with different superscript letters are significantly different (P < 0.05).

 

Egg quality

Table III summarizes the effects of claw removal on egg quality characteristics. The results obtained here demonstrated the significant increases in shell thickness among declawed treatments and yolk color in group 2 compared with intact control, but no differences were detected in shell strength, shell color, egg shape index, shell weight, egg weights, percentage of yolk, albumen height and Haugh units.

Feather condition

The effects of claw removal on feather condition of layer breeders were examined in the current study. As illustrated in Table IV, overall feather score of hens was not significantly different among declawed treatments and intact control. Interestingly, the feather score of the neck was significantly lower than that of any body part. Likewise, an overall feather score of roosters was largely similar to that of hens. The neck region on roosters had the lowest feather score around 3.3 points in the studied groups.

 

Table IV.- The average feather score for each individual part of the body and an overall average score of birds in the mating cage.

Parameters	Group 1	Group 2	Group 3	Group 4
Laying hens
Neck	2.94±0.11c	2.75±0.11b	3.01±0.12b	2.81±0.12b
Breast	3.68±0.04ab	3.55±0.06a	3.62±0.03a	3.55±0.06a
Back	3.77±0.03a	3.64±0.03a	3.68±0.02a	3.77±0.03a
Wing	3.70±0.05ab	3.56±0.05a	3.68±0.03a	3.73±0.03a
Tail	3.48±0.04b	3.53±0.07a	3.54±0.04a	3.61±0.07a
Overall feather	17.57± 0.16A	17.03± 0.18A	17.52± 0.13A	17.47± 0.18A
Roosters
Neck	3.36±0.11b	3.51±0.06b	3.39±0.06b	3.39±0.11c
Breast	3.65±0.03a	3.66±0.02ab	3.56±0.03ab	3.63±0.02ab
Back	3.73±0.03a	3.74±0.03a	3.73±0.03a	3.73±0.03a
Wing	3.70±0.03a	3.69±0.04ab	3.74±0.03a	3.65±0.05ab
Tail	3.61±0.04a	3.54±0.06b	3.59±0.06a	3.46±0.05b
Overall feather	18.05± 0.19A	18.14± 0.14A	18.00± 0.12A	17.85± 0.12A

A total of 30 (15 male and 15 female) birds per group were randomly scored in the current study. Finally, the average feather score for each individual part of the body and an overall average score were calculated. Means with different superscript letter are significantly different (P < 0.05). Lowercase letters are for columns and capital letters are for rows.

 

DISCUSSION

 

Laying performances, a major productive and economic indicators in the layer industry, were investigated in the current study. Our results displayed that laying rate was significantly increased in groups 3 and 4 compared with intact control, which agreed with Kolokol’nikova et al. (2009) and Ruszler and Kiker (1975), but contradicted the conclusions that overall hen-day egg production was unaffected by claw reduction (Compton et al., 1981). This inconsistency might be caused by gender and strain differences of declawed birds used for study. Percentage of defective eggs was significantly lower in group 3 than in the control group, since percentage of defective eggs is considered to be regulated by various factors, our study may not be able to explain the phenomenon. But conceivably an indication that claw reduction apparently affected percentage of defective eggs in a group-specific manner, mortality remained unchanged for all groups of birds. These results were in conflict with the findings of Compton et al. (1981). Conversely, our findings were mostly parallel to those of Ingram and Wilson (1981) and Compton et al. (1981), who found that hen mortality was not affected by claw trimming. Hatching experiment showing that egg fertility exhibited a significant depression in group 4 was nearly identical to previously published results (Ingram and Wilson, 1981). This phenomenon was probably because roosters with the second and fourth toes declawed were not as capable of keeping their balance during the mating period. In comparison to egg fertility, we also observed a similar trend in hatchability of setting eggs in group 4. It is not surprising that hatchability of setting eggs is positively correlated with egg fertility under a fixed total number of setting eggs. Little variations were found in terms of hatchability of fertile eggs, percentage of healthy pullets, male-to-female ratio, rate of water loss and average chick hatching weight, suggesting that they were unaffected by claw reduction.

Egg quality is composed of those characteristics of an egg that is a crucial fact in the poultry industry for its reproductive and economic values (Dudusola, 2009; Onbasilar et al., 2011). Although it is well documented, there is a lack of such knowledge in the mating cage. In our study, we first measured the egg quality characteristics of laying hens mated with the declawed roosters. Statistical analysis displayed that claw trimming significantly increased shell thickness among declawed treatments and yolk color in group 2 than the control. Admittedly, calcium is the major component of eggshell and the pigment content of feed is an important factor for yolk color (Shen and Chen, 2003; Faitarone et al., 2016). Thus, the marked exaltations in shell thickness and yolk color might be associated with the absorption of dietary calcium and pigment from the gut. But, both were not readily measured in our current experiment. There were no significant differences between treatment and control groups for shell strength, shell color, egg shape index, shell weight, egg weights, percentage of yolk, albumen height and Haugh units. Egg quality may be affected by various factors such as bird strain and age, nutrition, disease, storage, stress etc. (Rroberts, 2004). The current results should be carefully guarded and extensive investigations are needed to verify the effects of claw trimming on egg quality characteristics.

Feathers are epidermal outgrowths that form distinctive external covering of the body of birds. They not only aid in thermal insulation, waterproofing and flight, but feather condition is used as a phenotypic indicator of welfare level. Feather cover of all birds was evaluated in the present work. The results demonstrated that toe amputation did not alter overall feather score in all four groups. These findings largely agreed with the results of Compton et al. (1981), Glatz (2004), Tauson (1986) and Vanskike and Adams (1983) but contradicted the conclusions proposed by Hill (1975) and Fickenwirth et al. (1986) that the reduced claw length apparently ameliorated the influence of the claws on feathers during trampling. Given that relatively young birds were selected in this study, cumulative trampling period of claw on feather may be too short to cause a severe feather loss. Thence, further studies are warranted by extension of experimental period. Additionally, the neck region on birds on all groups had the poorest plumage condition of any body part, which makes distinct contacts with the cage door while eating can explain the neck feather conditions.

 

CONCLUSIONS

 

We investigated the effects of declawed roosters on laying performances, egg quality characteristics and feather cover of the mated hens in a natural mating system. It could be concluded from overall results that claw reduction has significant effects on some laying performances and egg quality characteristics of layer breeders in a group-specific manner. Preferential trimming methods were the removal of the first and third or second and fourth claws of day-old chicks in Hy-Line strain. The rationality of declawing as a management practice must be verified by more extensive investigations in other strains.

 

ACKNOWLEDGMENTS

 

This study was jointly supported by the National System for Layer Production Technology of China (CARS-41-K19), the National Natural Science Foundation of China (31601932), the Natural Science (Youth) Foundation of Anhui Province (1508085SQC205), Nonprofit Research Project of Anhui Province (1604f0704049) and Special Fund for Talent Development of Anhui Academy of Agricultural Sciences (16F0404). We also want to express our sincere appreciation to the staffs at Jiangxi Huayu Poultry Breeding Co., Ltd for their assistance and contributions (Yichun, Jiangxi, China).

 

Statement of conflict of interest

Authors have declared no conflict of interest.

 

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