Infrared beak treatment method compared with conventional hot-blade trimming in laying hens

Infrared beak treatment method compared with conventional hot-blade trimming in laying hens R. L. Dennis,* A. G. Fahey,* 1 and H. W. Cheng* 2 *Livestock Behavior Research Unit, USDA-Agricultural Research Service, West Lafayette, IN 47907; and Purdue University, Department of Animal Sciences, West Lafayette, IN 47907 ABSTRACT Infrared lasers have been widely used for noninvasive surgical applications in human medicine, and their results are reliable, predictable, and reproducible. Infrared lasers have recently been designed for the express purpose of providing a less painful, more precise beak-trimming method compared with conventional beak trimming. This study was designed to examine the potential of the infrared (IR) beak treatment to provide a welfare-friendly alternative to the conventional hot-blade method for chickens. The birds were beak trimmed by IR at the hatchery or by hot blade at 7 to 10 d of age in a commercial production setting, in accordance with standard procedures. The beak morphology and associated physiological characteristics, including production and aggressive behavior of the birds, were analyzed at 30 wk of age. There was no difference in egg production or bird BW between the 2 beak-trimming treatments. Birds also exhibited no difference in stress physiology measured in the study, such as fluctuating asymmetry and heterophil and lymphocyte profiles. However, birds receiving the IR treatment showed a superior feather condition and reduced aggressiveness under high light intensity, even though they had longer beak stumps. The results may indicate that the IR beak treatment may reduce the damage done by aggressive pecking and feather pecking. Indeed, IR trimming may provide a more welfare-friendly alternative to conventional beak trimming without compromising productivity. Key words: infrared beak treatment, hot-blade beak trimming, stress, production, hen 2009 Poultry Science 88:38 43 doi:10.3382/ps.2008-00227 INTRODUCTION Beak trimming (also termed debeaking, beak mutilation, or partial beak amputation) is a routine husbandry procedure practiced in the commercial poultry industry, particularly in broiler breeders and laying hens. The purpose of beak trimming is to reduce or inhibit feather pecking and aggressive pecking. Damage caused by pecking often leads to cannibalism in untrimmed flocks in all types of housing facilities (Appleby and Hughes, 1991; Craig and Muir, 1996; Glatz, 2001). Until recently, conventional hot-blade beak trimming (HB) has been the preferred method used in the United States and in numerous other countries. It typically involves the removal of part of the upper and lower mandibles with a heated blade to cut and cauterize the beak tissue of chicks between 1 and 10 d of age. 2009 Poultry Science Association Inc. Received June 4, 2008. Accepted August 24, 2008. 1 Current address: University College Dublin, School of Agriculture, Food Science and Veterinary Medicine, Belfield, Dublin 4, Ireland. 2 Corresponding author: Heng-wei.Cheng@ars.usda.gov Worldwide, HB solicits a great deal of debate pertaining to the relative impact of the practice on bird well-being. Although the benefits bestowed in reduced damage from aggression, feather pecking, and cannibalism may indeed favor improved welfare in beak-trimmed birds, there is a considerable body of morphological, neurophysiological, and behavioral evidence demonstrating that HB may cause acute and chronic pain, especially in adult birds (Breward and Gentle, 1985; Gentle et al., 1997a,b). As the Farm Animal Welfare Council (2007) recently indicated, beak trimming is a most undesirable mutilation but if injurious pecking cannot be controlled by beak trimming or other means, then there may be significant adverse consequences if a ban on beak trimming is introduced by December 2010. An obvious solution to HB is to introduce an alternative method that reduces acute pain and prevents chronic pain by limiting the tissue damage and inflammation associated with trimming before breeders are able to make selected nonpeck bird strains commercially available. Recent technological advances now allow beak trimming to be performed by laser. Infrared (IR) beak treatment (Nova-Tech Engineering Inc., Willmar, MN) 38

AN ALTERNATIVE METHOD FOR BEAK TRIMMING IN HENS 39 is an automated process carried out at the hatchery on the day of hatch. Chicks are immobilized by a head restraint and infrared energy is focused on the area of the beak requiring trimming. High-intensity (radiant) heat penetrates down through the corneum layer of the beak to the corneum-generating basal tissue and inhibits further germ layer growth. After treatment, the corneum layer remains intact until 7 to 10 d posttrimming, after which the tip of the beak begins to soften and erode away with use. Some important advantages of IR over HB appear to be 1) that open wounds are eliminated (Bloomquist, 2001; Chapman et al., 2008); 2) that changes in beak length and shape occur gradually over a 2-wk period; 3) that multiple stressors, such as catching, mixing, transfer, and handling, are reduced; and 4) that it potentially provides a precise and reliable treatment of the beak while minimizing operator error and inconsistency. One recent study by Gentle and McKeegan (2007) reported that, compared with HB, IR caused fewer behavioral changes and less variability in beak length in broiler breeder chicks up to 6 wk posttrimming. However, little additional research is available on the effectiveness of IR trimming as an alternative method for use in production. This study was a unique comparison of these 2 beak-trimming methods under commercial production conditions. Our aim was to determine the potential for IR beak treatment as a welfare-friendly alternative to conventional HB trimming, without compromising production standards and while improving bird well-being. MATERIALS AND METHODS All procedures were approved by the Purdue Animal Care and Use Committee. Layer Room Bovans White laying hens were caged in 5-bird cages at a commercial egg farm (Akron, IN). Each cage had dimensions of 40.64 50.80 cm, to give a cage density of 412.90 cm 2 per bird. Cages were kept in tiers 5 cages high, and each cage row was 136.54 m. The layer room had a total of 30,150 cages, with a potential capacity of 150,750 hens. The layer room contained birds that had been beak trimmed by 2 different methods, HB or IR. Feed and water were provided ad libitum. Overhead lights were on daily from 0400 until 2000 h (16L:8D). Measurements were taken from 1 bird per cage at 30 wk of age. Two rows of cages were used (one upper row and one lower row), with 15 cages per row per beak treatment (n = 30 birds per beak treatment for all measures except behavior, where n = 27). In an attempt to reduce variability caused by the microenvironment, the cages used were selected from 1 region of the house. The sampled bird within the cage was chosen by a random number generator. The birds were assigned numbers (1 through 5) as follows: the bird in the back left corner on first approach was bird 1, and the remaining birds were numbered sequentially, with bird 5 being the farthest from the back left corner. On removal of birds from the cage for physiological measurements, birds were marked on the tail with blue livestock marker for identification for behavioral measures. Beak-Trimming Treatments Hot-blade beak trimming was conducted on farm by a trained team when the birds were 7 to 10 d old. Infrared beak treatment was performed at the hatchery (Centurion Poultry MidAmerica Hatchery, Beaver Dam, WI) by using equipment developed by Nova-Tech Engineering. BW and Egg Weight Body weights were collected from 30 birds per treatment when the birds were 30 wk old. Egg weights were taken for 30 eggs from the birds in each treatment. Feather Score Feather scoring was used to assess the quality of feather coverage of each chicken. Feathers were scored on a scale of 0 to 5, with the best score being 0 and the worst score being 5 (Table 1). Seven body regions were assessed, and an average of these was taken as the total average feather score for each bird. To eliminate interobserver variation, feather score data collection was conducted by the same trained person. Beak Morphology A digital image of each beak was recorded by using the same method and equipment as outlined by Fahey et al. (2007). Briefly, images of each beak were captured with a 5.1 megapixel Nikon digital camera (Nikon Inc., Melville, NY). Beak dimensions were determined by using MCID image analysis software (version 4.0, Imaging Research Inc., Ontario, Canada) to examine the length of the upper and lower mandibles of the beaks at several points along the mandible. To achieve this, images were imported into MCID before being individually calibrated (number of pixels per horizontal and vertical centimeter) by using a background reference scale incorporated into each image. Table 1. Feather score guidelines Feather score Description 0 Smooth, complete plumage 1 Ruffled, with no bare spots 2 Small bare spots (up to 5 cm wide at the widest part) 3 Large bare spots (greater than 5 cm wide) 4 Area completely bare 5 Area completely bare with injury to skin

40 Dennis et al. Table 2. Ethogram of behavioral observations Behavior Eating Drinking Walking Aggressive behavior Aggressive peck Threat Other Feather peck Cage peck Description Head extended toward the feeder and appears to be manipulating feed Pecking at water nipple Taking one or more steps Forceful downward peck at the head or neck of a conspecific Bird standing in front of a conspecific looking at the other bird with neck raised and feathers erect Includes other overt aggressive behaviors such as fights, fight with pecks, and chase and grip Pecking at the feathers of a conspecific; can include gentle nibbling or severe pecking in which the feather is disturbed or removed Pecking at the floor, walls, or ceiling of the cage; does not include pecks to the feeder trough Additional Physiological Data Fluctuating asymmetry (FA) was determined as described in Palmer and Strobeck (1997). Right and left shank length and width of birds of each treatment were measured using digital calipers (graduations: 0.01 mm). Fluctuating asymmetry was calculated by the equation FA i = LW i RW i + LL i RL i, where FA i is the FA of the ith chicken; LW i is the width of the left shank of the ith chicken; RW i is the width of the right shank of the ith chicken; LL i is the length of the left shank of the ith chicken; and RL i is the length of the right shank of the ith chicken. Blood smears were prepared from unheparinized blood samples by using a cover glass technique and were stained within 1 h of preparation with Wright s stains (Campbell, 1988). A double blind design was used in the cell counts. Two hundred leukocytes on each slide were examined at 2,000 magnification. Heterophils and lymphocytes were identified based on the characteristics described by Campbell (1988), from which the heterophil-to-lymphocyte (H:L) ratio was calculated. Behavioral Data Direct 10-min focal observations were taken of a single marked bird per cage (n = 27). Total time spent inactive and the duration of time spent engaged in eating, drinking, and walking were recorded. Aggressive behaviors, feather pecks, and cage pecks were recorded as the number of incidents or the frequency per 10 min. The behaviors recorded are described in Table 2. Statistical Analysis Production and physiology data were checked for normality with the aide of histograms, quantile-quantile plots, and formal statistical tests with the UNI- VARIATE procedure of SAS, version 9.1 (SAS Institute Inc., Cary, NC). Body and egg weights had a normal distribution; however, FA required a log 10 transformation. Feather scores were ranked and then analyzed by using a mixed model. The data were analyzed by using the MIXED procedure of SAS. Cages were analyzed by beak-trimming method (HB and IR) as well as the interaction between treatment and area of the room (front, middle, or back) and row (top or bottom) to account for the effect of the microenvironment within the house. Interactions with P-values greater than 0.50 were removed from the model. The model used to analyze BW, FA, and ranked feather scores was Y i = µ + T j + T j A k + c i (T j A k ) + ε ijkl, where Y i is the BW, FA, or ranked feather score of the ith chicken; T j is the fixed effect of the jth treatment; T j A k is the fixed effect of the interaction of the jth treatment with the kth area (front, middle, or back of the room); c i (T j A k ) is the random effect of the ith chicken within the jth treatment and the kth area; and ε ijkl is the residual error term. The model used to analyze egg weight and behavior was Y i = µ + T j + T j R k + c i (T j R k ) + ε ijkl, where Y i is the egg weight and behavior of the ith chicken; T j is the fixed effect of the jth treatment; T j R k is the fixed effect of the interaction of the jth treatment with the kth row (top or bottom); c i (T j R k ) is the random effect of the ith chicken within the jth treatment and the kth row; and ε ijkl is the residual error term. Beak Length RESULTS Beak length was significantly shorter in HB-treated birds compared with IR-treated birds (Table 3). Upper beak length showed the greatest difference between treatments, with a difference of the means of 0.26 cm. The lower beak length was an average of 0.10 cm shorter in HB-treated birds. Beak stumps with scar tissue were found in HB-treated birds only (5:0 HB:IR; Table 3).

AN ALTERNATIVE METHOD FOR BEAK TRIMMING IN HENS 41 Table 3. Different effects (least squares means ± SE) of beaktrimming methods on beak length Treatment Hot blade Infrared Upper beak length (cm) 1.24 ± 0.04 b 1.50 ± 0.04 a Lower beak length (cm) 1.14 ± 0.04 b 1.24 ± 0.04 a Beak stump with scar tissue 5 0 a,b Within a row, different letters denote significant differences, P < 0.05. Production and Physiological Measures No differences were found in egg weight or BW between treatments (Table 4). Degree of asymmetry, as measured by the FA of the shank length and width, did not differ by beak-trimming treatment (Table 4). Percentage of heterophils, percentage of lymphocytes, and H:L ratio were also not significantly different between the IR- and HB-treated birds (Table 4). In contrast, feather scores were significantly worse on the head and back of HB-trimmed birds compared with IR-trimmed birds (Table 5). Feather scores from the neck tended to be worse on HB-trimmed birds compared with IRtrimmed birds (P = 0.07). No difference was found in feather scores for the other body regions. Behavior A significant row treatment interaction was determined in the analysis of aggressive behaviors. In the top row, HB-treated birds showed significantly more aggression than IR-treated birds (Figure 1). No difference was found between the treatments in the lower row. No differences were determined between the treatments in the other behaviors recorded. DISCUSSION The practice of beak trimming has received much criticism for being a painful procedure with potentially harmful long-term negative effects, such as neuroma formation and associated pain (Gentle et al., 1995, 1997b). However, the conventional alternative of leaving birds untrimmed has been shown to result in greater instances of cannibalism (Appleby and Hughes, 1991; Craig Table 5. Feather scores 1 (least squares means ± SE) for hotblade and infrared beak-trimmed chickens Body region Hot blade Infrared Head 1.40 ± 0.12 a 1.10 ± 0.12 b Neck 1.67 ± 0.15 c 1.40 ± 0.15 d Abdomen 1.53 ± 0.13 1.20 ± 0.13 Breast 1.67 ± 0.15 1.43 ± 0.15 Tail 2.20 ± 0.15 2.33 ± 0.15 Back 1.80 ± 0.14 a 1.23 ± 0.14 b Wings 1.77 ± 0.10 1.63 ± 0.10 Average 1.72 ± 0.08 c 1.48 ± 0.08 d a,b Within a row, different letters denote significant differences, P 0.05. c,d Within a row, different letters denote significant differences, P 0.10. 1 Best score = 0 and worst score = 5. Average feather score is the arithmetic mean of all body regions. and Muir, 1996; Glatz, 2001). Infrared beak trimming may offer a more welfare-friendly method of beak trimming. In this study, we investigated production- and stress-related traits in HB- and IR-trimmed birds in a production setting, and found no adverse effects of IR trimming on production. In fact, some positive effects were found in traits that may directly and or indirectly improve production and bird well-being. External and internal stressors have been shown to alter egg lay by altering egg numbers or egg weight (Muir and Craig, 1998; Bollengier-Lee, 1999; Sahin et al., 2002). However, we observed no difference in egg production between IR-trimmed and HB-trimmed birds in the same house. Similarly, BW can be greatly affected by stressful and painful stimuli (Gross and Siegel, 1980, 1986) and, in turn, BW can alter long-term production capability (Summers and Leeson, 1994). However, IR beak trimming does not affect bird BW. Here, we observed no direct impact of IR on egg production in an actual industry setting, which was similar Table 4. Effects of beak treatment on BW, egg weight, fluctuating asymmetry (FA) of the shank bone, and blood profiles as assessed by the percentage of heterophils, the percentage of lymphocytes, and the heterophil-to-lymphocyte ratio (H:L; least squares means ± SE) Treatment Hot blade Infrared BW (kg) 1.454 ± 26 1.467 ± 26 Egg weight (g) 56.4 ± 0.97 55.2 ± 0.97 Absolute FA (length, mm) 1.25 ± 0.19 0.75 ± 0.21 Absolute FA (width, mm) 0.34 ± 0.07 0.45 ± 0.07 Heterophils (%) 38.20 ± 3.80 35.30 ± 3.64 Lymphocytes (%) 58.70 ± 4.04 63.70 ± 3.87 H:L ratio 0.83 ± 0.17 0.59 ± 0.16 Figure 1. Different effects of beak-trimming methods on aggressive behaviors of birds. A significant row treatment interaction was determined in displaying aggressive behaviors in birds. Hot-blade beaktrimmed birds in the top row were observed showed significantly more aggression than infrared beak-trimmed birds in the same row. Data are presented as least squares mean number of pecks given per bird in 10 min (n = 14 per treatment in the top row, and n = 13 per treatment in the bottom row). a,b Different letters denote a significant difference between beak treatments (P < 0.05).

42 to the findings in a laboratory setting (Marchant-Forde et al., 2008). Measures of immunocompetence and stress physiology were assessed to investigate the potential use of IR as a welfare-friendly alternative to conventional (HB) trimming. Heterophil and lymphocyte profiles have been associated with immunocompetence in birds and are also reactive to the stress of the individual (Maxwell, 1993). Heterophilia and lymphophilia have been associated with poor immune function and poor performance. That no differences were found in the white blood cell profiles between IR- and HB-trimmed birds may indicate that the IR treatment did not negatively affect immune function compared with the conventional HB treatment. However, in this study the measurements were taken on birds at 30 wk of age, whereas beak trimming is performed during the first 10 d of age. Stressful and painful stimuli early in life can have an effect on development. These effects can be measured by determining the difference from symmetry in normally symmetrical traits, such as the length and width of the leg or shank (Leary and Allendorf, 1989; Dennis et al., 2008). Again, we found no difference in the degree of FA between IR- and HB-treated birds. Feather condition depends on many factors, including nutrition, health, environmental stressors (Carrascal et al., 1998), and social factors, such as feather pecking and aggression from conspecifics (Bilcik and Keeling, 1999). Examinations of feather condition by feather scoring revealed that IR-treated birds had a significantly better feather condition in the head and back regions and tended to have a better feather condition in the neck. This result was quite surprising; indeed, we expected to find the feather conditions of IR-treated birds to be no worse than those of HB-treated birds. Superior feather conditioning in the head, neck, and back regions may be a result of reduced social aggression and fewer severe feather pecks, as reported in previous studies (LaBrash and Scheideler, 2005) Behavior analysis revealed no difference in the frequency of feather pecking; however, no distinction was made between gentle and severe feather pecking. Previous studies have shown that severe feather pecking and aggression affect feather conditioning, whereas gentle feather pecking may not be a significant contributor to feather loss or breakage (Savory, 1995). In addition, aggressive behaviors were significantly greater in HBtrimmed birds in the higher row observed, compared with IR-trimmed birds in the same row. Differences in aggression attributable to the microenvironment may be related to different exposures to stressful stimuli, including human workers, noise from machinery, or long- or short-term differences in climate. However, it is likely that these kinds of differences in microenvironment would be more noticeable in different areas or regions of the house because exposure to workers and other stressors is more likely to be region specific than row specific. It is likely that this difference was observed only in the top row because of differences Dennis et al. in light intensity between the rows, because increased light intensity has been shown to increase aggression and overall activity in birds (Prayitno et al., 1997). Although no measures of light intensity were taken, it is known that the lower rows or decks of caged laying systems are exposed to a reduced light intensity compared with the upper row (Rozenboim et al., 1998). Superior feather condition and reduced aggression in the row with greater light intensity suggest that IR trimming may be a less stressful method, resulting in improved well-being in adult birds. Agricultural husbandry practices that have become standard operations in most facilities worldwide have recently come under close scrutiny for their welfare implications for animals. Beak trimming with the HB procedure has become one of the most controversial among animal welfare advocates. Such agencies have demanded that the poultry industry and scientists provide a better means of reducing cannibalism in their birds. Unfortunately, reliable methods to control feather pecking and cannibalism are severely lacking. The problems of cannibalism and feather pecking have been researched for decades with no clear solution, and there is no sign that breeders will be able to guarantee the non-peck layer in time (British Free Range Egg Producers Association, 2006). To face the welfare battle, an obvious solution is to work actively on developing an alternative method of beak trimming that minimizes pain and stress, yet safeguards bird well-being, and that is highly accepted by the public. 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