ABSTRACT

This study examined the effects of infrared beak treatment (IR-BT) and hot blade beak trimming (HB-BT) on beak length and production in laying hen pullets. Seventy-two 1-d-old birds were randomly assigned to the HB-BT, IR-BT, or control group. Birds were pair housed by treatment, and beak images and production indices were obtained posttreatment at fixed intervals for 10 wk. Immediately after treatment, HB-BT beaks were shorter than control or IR-BT beaks (P < 0.01), whereas control and IR-BT beaks remained comparable in length until the onset of tissue degeneration and erosion of the IR-BT beaks at 1 to 2 wk posttreatment. At wk 2 posttreatment, beaks were longest in control birds, intermediate in IR-BT birds, and shortest in HB-BT birds (P < 0.01). Thereafter, an increase in beak length in all treatments was observed over time (P < 0.01), but HB-BT beaks had the greatest regrowth. The beak length of birds in the HB-BT group was similar to that of birds in the IR-BT group from wk 3 to 8, and then grew longer at wk 9 and 10 posttreatment (P < 0.01). The effects of treatments on BW emerged at d 5 posttreatment. The BW of birds in the HB-BT group was suppressed up to and including wk 9 posttreatment compared with that of control birds (P < 0.05) and was significantly lower than that of birds in the IR-BT group between 2 and 4 wk posttreatment (P < 0.05). Birds in the IR-BT group did not differ from control birds after wk 3 posttreatment (P < 0.05). By the final week of the study, differences in BW across treatments were no longer apparent (P > 0.05). For the most part, feed intake was higher in control birds, intermediate in birds in the IR-BT group, and lowest in birds in the HB-BT group until wk 9 posttreatment (P < 0.05). Similarly, feed waste was generally higher in control birds and least in birds in the HB-BT group (P < 0.05). The IR-BT treatment appeared to be more effective at inhibiting beak regrowth, with a less pronounced effect on feed intake than the HB-BT treatment in laying hen pullets.

INTRODUCTION

Beak trimming is a routine husbandry procedure practiced in the poultry industry, including on laying hens, broiler breeders, turkeys, and ducks. The purpose of beak trimming is to reduce or inhibit interbird pecking, aggression, and cannibalism. As with most invasive husbandry procedures, beak trimming has elicited a great deal of debate and research from an animal well-being perspective (Farm Animal Welfare Council, 2007). The beak of the chicken is a complex, functional organ with an extensive nerve supply (Gentle and Breward, 1986; Gentle, 1989; Cheng, 2005; Kuenzel, 2007). After beak trimming, several anatomical, physiological, and biochemical changes occur in cut peripheral nerves and damaged tissues (Cheng, 2005; Kuenzel, 2007). A considerable body of morphological, neurophysiological, behavioral, and production research has demonstrated the emergence of several markers of acute and chronic pain [e.g., persistent lethargy and guarding behaviors, reduced feed intake (FI), and development of neuromas] caused by trimming (Eskeland, 1981; Gentle, 1986; Gentle et al., 1990, 1991). Nevertheless, the reported effects of beak trimming on behavior, physiology, and production are at times paradoxical. This may be due in part to inconsistency in the type and degree of beak trimming performed (e.g., hot blade vs. cold blade, one third vs. one-half of the beak removed), together with differences in bird strain or breed, as well as variations in the age at which the procedure is performed and what parameters are observed, which has been addressed in a recent comprehensive review (Hester and Shea-Moore, 2003).

Hot-blade beak trimming (HB-BT) is a routine method for preventing feather pecking and its associated cannibalism in laying hens in the United States. However, it is anticipated that consumer pressure to ban or modify beak trimming will increase, to improve bird well-being. In response to welfare concerns, several management techniques, such as reducing light intensity or modifying housing environments, have been used to prevent feather pecking and aggression. However, these methods have limited success and provide no guarantee of controlling feather pecking. Currently, feather pecking can occur in all housing systems, including cage, barn, organic, and free-range systems (Appleby and Hogarth, 1991; Glatz, 2000). These issues compel poultry industry members to investigate alternatives to conventional HB-BT. One such substitute is an infrared beak treatment (IR-BT), which is purported to have a less negative effect on well-being than HB-BT in broiler breeder chicks (Gentle and McKeegan, 2007; Henderson et al., 2009). One of the perceived advantages of this method of trimming relative to HB-BT is the elimination of open wounds and potential bleeding sites that may lead to inflammation, infection, and pain. Furthermore, because the posttreatment changes in beak length and shape occur gradually, this procedure may facilitate better adaptation of beak-related functions (e.g., feeding behavior) after treatment.

The results of comparative effects of IR-BT and one-third HB-BT on White Leghorn chicks have been reported previously (Marchant-Forde et al., 2008). Traditionally, HB-BT involves the removal of one-third to one-half of the upper and lower mandibles by using a hot blade that both cuts and cauterizes the beak tissue. The objective of this work was to compare the effects of IR-BT and one-half HB-BT at 1 d of age on subsequent beak morphology and growth of layer chicks from 1 to 10 wk of age.

MATERIALS AND METHODS

Housing and Husbandry

Seventy-two 1-d-old White Leghorn female chicks were randomly assigned to 1 of 3 treatment groups: IR-BT, HB-BT, and sham trimming (control). To avoid isolation stress, the chicks (24/treatment) were randomly paired within treatment and housed in identical cages (30.5 × 30.5 cm) within an environmentally controlled room. They had ad libitum access to water and standard feed appropriate for their stage of development and were kept at a constant 16L:8D photoperiod. Temperature was initially maintained at 95°F during the first week, and then lowered by 5°F weekly until an ambient temperature of 70°F was reached at 5 wk of age.

Treatments

All treatments were applied at the hatchery by skilled operators immediately before the chicks were transported for 2 h to the animal housing facilities at Purdue University. Twenty-four (12 pairs, n = 12) of the chicks were trimmed by a trained person using a hot-blade trimmer (200 F, Lyon Electric Co. Inc., San Diego, CA) to attain a reduction in length of both the upper and lower mandibles of approximately one-half. A second batch of 24 chicks (12 pairs, n = 12) were trimmed using an automated infrared beak treatment system (NOVA-Tech Engineering Inc., Willmar, MN) preset to trim both mandibles at a hatchery. The remaining 24 chicks were picked up and handled to somewhat simulate the handling stress being experienced by the chicks in the other 2 treatment groups, but their beaks remained untrimmed.

Beak Data

To evaluate treatment-related differences in beak lengths and regrowth rates, individual photographs of the beak of each chick were taken immediately posttreatment (d 0) and then at d 2 and 4 posttreatment. Thereafter, beaks were photographed on a weekly basis until the chicks reached 10 wk of age. This method was reported previously (Marchant-Forde et al., 2008).

Production and Physical Parameters: Feed Intake, Feed Waste, and BW

Feed intake and feed waste (FW) were determined on a weekly basis for the birds in each cage from 3 wk of age onward by using a 3-d protocol reported previously (Paterson et al., 2000; Pohle and Cheng, 2009). Feed intake data were presented on a bird × day basis, that is, total intake during the period divided by bird × day (Lewis et al., 2000). Body weight was measured on d 0, 1, 2, and 5, and then once per week thereafter.

Statistical Analysis

All data were checked for normality and homogeneity of variance. Nonnormal data were transformed using λ values generated by Box-Cox transformations. Repeated measures ANOVA (GLM) were then used to evaluate the effects of the different treatments over time. The model was as follows: 

xijk = m + i (treatment) + j (i) (cage) + k (time) + ik (treatment × time) + eijk,
where xijk is beak length and eijk is residual error.

Where significant F-values were noted, Tukey’s honestly significant difference tests were used to determine where these differences existed. Where the outcome of transformations was unsatisfactory, Kruskal-Wallis and Mann-Whitney U-tests in each time were used in place of parametric approaches. The Minitab V12.1 statistical package was used for data analysis, and results were considered significant when P < 0.05 and are expressed, where appropriate, as the mean ± SEM.

RESULTS AND DISCUSSION

Beak Data

Visual assessment of wound-healing rates indicated that visible wounds and necrotic beak tissue were still present 2 to 3 wk after HB-BT, with upper mandibles healing more rapidly than lower ones, which was similar to the findings reported previously (Marchant-Forde et al., 2008). No occurrence of open wounds was recorded for birds in the IR-BT treatment, consistent with earlier reports (Honaker and Ruszler, 2004; Marchant-Forde et al., 2008). The different trimming methods resulted in different beak lengths (Figure 1a and 1b; P < 0.01) and different rates of regrowth (P < 0.01). Temporal assessment of beak length highlighted an overall effect of time and a treatment × time interaction for beak regrowth (Figure 1b; P < 0.01). For the most part, the regrowth rate of beaks increased over time in all 3 groups (P < 0.01), consistent with what one would expect to see in normally growing birds and in line with beak trimming data published elsewhere (Kuo et al., 1991; Gentle et al., 1997).

Figure 1

Treatment-related differences in beak length in White Leghorn chicks trimmed at 1 d of age. a) Change in beak length in control birds and birds in the infrared beak treatment (IR-BT) group from immediately posttreatment to 1 wk posttreatment. b) Different beak regrowth rates after hot-blade beak trimming (HT-BT) and IR-BT from wk 1 to 10. Data are presented as mean ± SEM (n = 12). d = day posttreatment; wk = week posttreatment.

Figure 1

Treatment-related differences in beak length in White Leghorn chicks trimmed at 1 d of age. a) Change in beak length in control birds and birds in the infrared beak treatment (IR-BT) group from immediately posttreatment to 1 wk posttreatment. b) Different beak regrowth rates after hot-blade beak trimming (HT-BT) and IR-BT from wk 1 to 10. Data are presented as mean ± SEM (n = 12). d = day posttreatment; wk = week posttreatment.

Immediately after beak trimming, birds in the HB-BT group has statistically shorter beaks relative to birds in the control and IR-BT groups (Figure 1a; P < 0.01). The beak lengths were similar for birds in the control and IR-BT groups until the onset of the treatment-related degeneration and erosion of tissue in the IR-BT beaks. This erosion was first noticeable between the second and fourth day after treatment, and it became increasingly prominent until the second week after treatment, which is in agreement with the erosion times reported by Honaker and Ruszler (2004) and Marchant-Forde et al. (2008). From d 1 to wk 2 posttreatment, the beak length was consistently greater in birds in the control group, intermediate in birds in the IR-BT group, and shorter in birds in the HB-BT group, but by the end of the study, the beak lengths of birds in the HB-BT group became longer than that those of birds in the IR-BT group (Figure 1; P < 0.01). Compared with birds in the IR-BT group, faster regrowth of beaks was found in birds in the HB-BT group, beginning at wk 7 and thereafter and becoming statistically significant at wk 9 and 10 posttreatment (Figure 1b; P < 0.01). The current and previous findings (Marchant-Forde et al., 2008) indicate that IR-BT suppresses beak regrowth more than HB-BT. A similar pattern of beak regrowth after HB-BT was also reported by Gentle et al. (1997). In their study, early differences in beak length between intact birds and birds receiving HB-BT dissipated within 5 wk after the procedure. The results of the present study offer further evidence that beak regrowth is of concern when the beaks of chicks are trimmed by HB-BT at earlier than 7 to 10 d of age (Hester, 2005). Birds at this stage that undergo HB-BT are often exposed to a second, more permanent trim later in age.

The long-term efficacy of IR-BT at inhibiting beak regrowth is unknown. It could be that the infrared beam (high-intensity heat) penetrates down into the corneum-generating basal tissue and causes less posttrimming inflammation. Those effects inhibit further germ layer growth, resulting in a shortened beak after the treatment. The healing appearance after IR-BT may be similar to the findings in mammals after infrared procedures. For example, infrared-associated changes in biological processes in tissue accelerate wound healing and reduce scar formation (Oron et al., 2001; Capon and Mordon, 2003).

Production Parameters: Feed Intake, Feed Waste, and BW

Feed intake and growth are key indices presented in the literature as gauges of the effect on bird well-being after various stressors, including beak trimming. The predominant finding after beak trimming is that moderate trimming, particularly at the earlier ages, reduces FI and subsequent growth (Glatz and Lunam, 1994; Gentle et al., 1997; Davis et al., 2004), with minimal residual effects on time to reach sexual maturity and subsequent egg production (Andrade and Carson, 1975; Craig and Lee, 1989; Craig and Lee, 1990; Kuo et al., 1991; Struwe et al., 1992). Both FI and FW were somewhat predictably influenced by trimming and the trimming method in this study. Average daily FI was highest in the control group and lowest in the HB-BT group during the observation period, namely, from wk 3 to 6 posttreatment (Table 1). At wk 3 and 4, birds in both the HB-BT and IR-BT groups consumed less feed on a daily basis than control birds (P < 0.05). Depressed FI disappeared at wk 5 and thereafter for birds in the IR-BT group, whereas it remained from wk 5 to 6 (P < 0.05) for birds in the HB-BT group (Table 1). Similar to the current findings, after HB-BT at 1 d of age, the reduced FI of birds has been shown to persist from several weeks to several months (Andrade and Carson, 1975; Glatz, 1990; Lee and Craig, 1990; Craig 1992; Cunningham 1992). Marchant-Forde et al. (2008) also reported that FI was depressed for 3 to 4 wk for birds in an IR-BT treatment that were trimmed at 1 d of age. In contrast, Honaker and Ruszler (2004) reported a depression in FI for 18 wk in birds in an IR-BT treatment compared with control birds and birds trimmed by HB-BT at 7 d. It is difficult to determine the underlying reasons for these divergent results, but they may due in part to variations in bird genetics, housing environments, or other differences in experimental conditions between these studies. In the study by Honaker and Ruszler (2004), birds of different genetic origins were housed in a much more competitive environment (larger group size and higher stocking density), and any or all these factors may have contributed to the more pronounced reduction in intake exhibited by these birds.

Treatment-related differences in feed intake (g/bird per day)1

Table 1
Treatment-related differences in feed intake (g/bird per day)1
Time Control HB-BT IR-BT 
Week 3 16.8 ± 0.7a 13.5 ± 0.7b 14.7 ± 0.7b 
Week 4 19.2 ± 0.9a 14.6 ± 0.6c 17.3 ± 0.4b 
Week 5 24.4 ± 1.0a 19.0 ± 0.7b 22.8 ± 0.9ab 
Week 6 27.2 ± 0.8a 23.1 ± 1.0b 26.4 ± 0.9ab 
Week 7 29.8 ± 1.2 25.9 ± 1.5 29.2 ± 1.2 
Week 8 31.7 ± 0.7 28.4 ± 0.7 32.3 ± 0.7 
Week 9 33.6 ± 0.9 30.4 ± 0.9 33.0 ± 1.2 
Time Control HB-BT IR-BT 
Week 3 16.8 ± 0.7a 13.5 ± 0.7b 14.7 ± 0.7b 
Week 4 19.2 ± 0.9a 14.6 ± 0.6c 17.3 ± 0.4b 
Week 5 24.4 ± 1.0a 19.0 ± 0.7b 22.8 ± 0.9ab 
Week 6 27.2 ± 0.8a 23.1 ± 1.0b 26.4 ± 0.9ab 
Week 7 29.8 ± 1.2 25.9 ± 1.5 29.2 ± 1.2 
Week 8 31.7 ± 0.7 28.4 ± 0.7 32.3 ± 0.7 
Week 9 33.6 ± 0.9 30.4 ± 0.9 33.0 ± 1.2 

a–cMeans within rows with different superscripts are significantly different (P < 0.05).

1Data presented as mean ± SEM (n = 12). HB-BT = hot-blade beak trimming; IR-BT = infrared beak treatment.

In general, however, changes in FI after beak trimming in poultry, irrespective of the trimming method or bird age, may indicate a decrease in motivation to feed that has been attributed to an increase in the presence of pain and discomfort caused by tissue, nerve, and or sensory receptor damage (Breward and Gentle, 1985; Gentle, 1986; Cheng, 2005). Reduced intake may also result from greater mechanical difficulties in feeding caused by anatomical changes in beak shape, the loss of beak sensitivity, or both that may arise after trimming, particularly in hens trimmed as adults (Gentle et al., 1982; Workman and Rogers, 1990). The current findings generally agree that trimming reduces FI, but compared with HB-BT, IR-BT had less effect on FI. The mechanisms could be related, at least in part, to the following advantages of IR-BT over HB-BT: 1) the elimination of open wounds and potential bleeding sites that lead to inflammation, infection, and pain, and 2) better adaptation of beak-related functions (e.g., feeding behavior) facilitated by a gradual change in beak length and shape posttreatment. The effect that beak trimming has on FI, such as how much IR-BT affects FI and for how long, depends somewhat on the age at trimming, the severity of trimming, the diet composition, and individual study characteristics. In the current study, the overall differences in intake for birds in the IR-BT and HB-BT groups suggest that IR-BT may be a bird-friendly alternative to HB-BT in day-old chicks.

Feed waste, compared with that of control birds, was numerically lower in birds in the HB-BT group for the entirety of the study, and statistically so during wk 3, 4, 5, 6, 8, and 9 posttrimming. During wk 6 and 8, the FW of birds in the IR-BT group was also significantly lower than that of control birds (Table 2; P < 0.05). Compared with birds in the IR-BT group, those in the HB-BT group had less FW at wk 5, 6, and 8 (P < 0.05). Decreased FW in trimmed birds has been observed in several earlier studies and is a likely a consequence of a trimming-related suppression in feeding as well as alterations in feed-directed beak behaviors that contribute to a reduction in feed spillage (Gentle, et al., 1982; Blokhuis et al., 1987; Lee and Craig, 1990; Craig et al., 1992). Reduced FW may be an important factor from the perspective of producers because feed represents a large proportion of the costs associated with egg production.

Treatment-related differences in feed waste (g/bird per day)1

Table 2
Treatment-related differences in feed waste (g/bird per day)1
Time Control HB-BT IR-BT 
Week 3 13.6 ± 1.5a 8.9 ± 1.3b 11.3 ± 1.5ab 
Week 4 11.4 ± 1.4a 6.3 ± 0.7b 9.1 ± 1.3ab 
Week 5 15.5 ± 1.7a 10.2 ± 1.2b 14.5 ± 1.8a 
Week 6 18.0 ± 0.7a 9.1 ± 1.5c 15.1 ± 1.5b 
Week 7 12.2 ± 0.9 8.9 ± 1.1 11.4 ± 1.9 
Week 8 14.4 ± 0.9a 7.5 ± 0.6c 11.0 ± 0.8b 
Week 9 18.7 ± 1.0a 14.6 ± 0.8b 16.5 ± 0.7ab 
Time Control HB-BT IR-BT 
Week 3 13.6 ± 1.5a 8.9 ± 1.3b 11.3 ± 1.5ab 
Week 4 11.4 ± 1.4a 6.3 ± 0.7b 9.1 ± 1.3ab 
Week 5 15.5 ± 1.7a 10.2 ± 1.2b 14.5 ± 1.8a 
Week 6 18.0 ± 0.7a 9.1 ± 1.5c 15.1 ± 1.5b 
Week 7 12.2 ± 0.9 8.9 ± 1.1 11.4 ± 1.9 
Week 8 14.4 ± 0.9a 7.5 ± 0.6c 11.0 ± 0.8b 
Week 9 18.7 ± 1.0a 14.6 ± 0.8b 16.5 ± 0.7ab 

a–cMeans within rows with different superscripts are significantly different (P < 0.05).

1Data presented as mean ± SEM (n = 12). HB-BT = hot-blade beak trimming; IR-BT = infrared beak treatment.

No differences in BW were found at the onset of the study. By d 5, however, an overall effect of trimming on BW was seen, irrespective of the method used (Table 3; P < 0.05). Body weight remained depressed at weekly weighings up to wk 3 in birds in the IR-BT group and up to wk 9 in birds in the HB-BT group (P < 0.05). From wk 2 through to the end of the study, BW was greater for birds in the IR-BT group relative to those in the HB-BT group from wk 2 to 4 (Table 3; P < 0.05), whereas the difference between birds in the IR-BT treatment and control birds disappeared from wk 4 to the end of the study (P > 0.05). Several earlier studies provide evidence of reduced BW subsequent to trimming, particularly when HB-BT is performed on young chicks (Blokhuis et al., 1987; Glatz and Lunam, 1994; Gentle et al., 1997). This depression in BW can persist for several weeks to several months, again depending on the timing and severity of trimming performed (Glatz, 1987; Craig and Lee, 1990; Lee and Craig, 1990, 1991). In contrast, compared with birds treated with HB-BT, faster growth was reported previously in birds treated with IR-BT (Marchant-Forde et al., 2008). The present and previous data indicate that IR-BT and HB-BT cause different responses in trimmed birds earlier posttreatment, at least in BW and FI.

Treatment-related differences in BW (g/bird)1

Table 3
Treatment-related differences in BW (g/bird)1
Time Control HB-BT IR-BT 
Day 0 37.56 ± 0.64 38.91 ± 0.54 38.24 ± 0.62 
Day +1 38.27 ± 0.50 38.62 ± 0.54 38.29 ± 0.47 
Day +2 41.60 ± 0.70 40.60 ± 0.60 40.02 ± 0.61 
Day +5 52.16 ± 0.84a 46.65 ± 1.01b 48.56 ± 0.73b 
Week +2 68.08 ± 1.51a 57.13 ± 1.37c 62.33 ± 1.41b 
Week +3 111.50 ± 2.83a 97.23 ± 1.47c 102.04 ± 1.46b 
Week +4 166.73 ± 5.10a 150.99 ± 3.91b 165.29 ± 3.40a 
Week +5 236.58 ± 7.53a 221.23 ± 5.66b 232.50 ± 7.01ab 
Week +6 323.55 ± 11.60a 291.77 ± 7.54b 310.80 ± 8.07ab 
Week +7 422.35 ± 13.30a 391.99 ± 7.31b 418.19 ± 11.20ab 
Week +8 514.27 ± 16.10a 472.63 ± 10.90b 495.36 ± 13.80ab 
Week +9 601.86 ± 16.10a 566.66 ± 11.10b 593.68 ± 10.80ab 
Week +10 660.23 ± 19.50 642.62 ± 13.10 654.90 ± 16.20 
Time Control HB-BT IR-BT 
Day 0 37.56 ± 0.64 38.91 ± 0.54 38.24 ± 0.62 
Day +1 38.27 ± 0.50 38.62 ± 0.54 38.29 ± 0.47 
Day +2 41.60 ± 0.70 40.60 ± 0.60 40.02 ± 0.61 
Day +5 52.16 ± 0.84a 46.65 ± 1.01b 48.56 ± 0.73b 
Week +2 68.08 ± 1.51a 57.13 ± 1.37c 62.33 ± 1.41b 
Week +3 111.50 ± 2.83a 97.23 ± 1.47c 102.04 ± 1.46b 
Week +4 166.73 ± 5.10a 150.99 ± 3.91b 165.29 ± 3.40a 
Week +5 236.58 ± 7.53a 221.23 ± 5.66b 232.50 ± 7.01ab 
Week +6 323.55 ± 11.60a 291.77 ± 7.54b 310.80 ± 8.07ab 
Week +7 422.35 ± 13.30a 391.99 ± 7.31b 418.19 ± 11.20ab 
Week +8 514.27 ± 16.10a 472.63 ± 10.90b 495.36 ± 13.80ab 
Week +9 601.86 ± 16.10a 566.66 ± 11.10b 593.68 ± 10.80ab 
Week +10 660.23 ± 19.50 642.62 ± 13.10 654.90 ± 16.20 

a–cMeans within rows with different superscripts are significantly different (P < 0.05).

1Growth rate (%) = BW at each time point/BW at d 0. Data presented as mean ± SEM (n = 12). HB-BT = hot-blade beak trimming; IR-BT = infrared beak treatment.

The findings of this study demonstrate that IR-BT was more effective at reducing beak regrowth and resulted in less effect on FI and BW than one-half HB-BT. However, both trimming methods affected these production parameters. Feed intake was lower for birds in the HB-BT treatment during the entire experimental period. Body weight was also decreased for birds in the HB-BT group until wk 10. Even though HB-BT resulted in the least FW, IR-BT also reduced FW compared with the control treatment and was not different from the HB-BT treatment for much of the experimental period, which is a favorable outcome for producers because feed represents a major portion of egg production costs.

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