sive behavior of chickens should benefit ani- mal welfare and husbandry [l, 2, 3). The common procedure used to reduce aggressive pecking and cannibalism is ...
01997 Applied Pouluy Science, Inc
CONTACT LENSES FOR LAYING HENS G. GVARYAHU’ and N. SNAPIR Department of Animal Science, Faculty of Apiculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovof 76100, Israel Phone: 972-8-9481397 F a : 972-8-9465763 E. GROSSMAN Extension Service, Ministry of Agriculture, Rehovot, Israel
Primary Audience: Egg Producers, Animal Welfare Researchers, Extension Workers
and are well versed in the useful aspects of DESCRIPTION OF PROBLEM such a product. Periodically one of those Any manipulation that decreases aggressive behavior of chickens should benefit animal welfare and husbandry [l, 2, 3). The common procedure used to reduce aggressive pecking and cannibalism is to trim the birds’ beaks [2]. Another way is to restrict their vision [l].Over the last 20 yr several companies have developed contact lenses for chickens in order to decrease their aggressiveness. Business school students [4] have been exposed to this idea for at least as many years 1
To whom correspondence should be addressed
students attempts to apply the idea of the lenses to the chicken industry. Animalens, Inc. [5l developed red contact lenses that restrict vision of the chickens by exposing them to red light only because red light was found to have a significant, positive effect on egg production [6]. Animalens, Inc. reported that their lenses increase egg production by 1%,decrease mortality by4%, and decrease feed cost by 8%. Above all, chickens with lenses are docile and easily handled. These results appear to be advantageous.
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CONTACT LENSES FOR LAYING HENS
However, it is surprising that the majority of producers chose not to adopt the lens concept. Adams [7], however, found that red plastic contact lenses which were fitted for hens either 12 or 16 wk of age caused considerable mortality attributable to the birds’ inability to find food. In preliminary observations with hens in their second laying period (81, we didn’t find any differences in mortality or egg production. The concept of contact lenses is still alive among business school students and it is important to clarify scientifically their actual value vis a vis production and behavior-welfare.
relative fearfulness. The maximum score was 240 sec. If birds righted themselves in more than 240 sec, it was assumed (for statistical analysis) that they did so in 240 sec. Immediately after the TI test the same chickens were weighed and killed by cervical dislocation. Because heart weight is known to be an indicator of the existence of long term stress (101, the chest cavity was immediately opened and the heart was carefully removed. The pericardial sac was removed from the heart and heart vesicles were trimmed to the musculature. The heart was then cut longitudinally, drained of excess blood, blotted dry, and weighed to the nearest tenth of a gram. Egg production data was transformed to arcsine d% values. Heart weights were expressed as a percentage of live body weights. Statistical analysis was carried out using the one-way ANOVA for the somatic results [ll] and Mann-WhitneyU-tests for the TI test [ 121.
MATERIALS AND METHODS ’ b o hundred White Leghorn chickens (PBU-Yarkon) in their second laying period (76 to 104 wk of age) were used in this study. Chickens were placed in an open shed house within conventional cage facilities (48.5 x 45.5 cm, with five birds per cage) with both natural and artificial light. All the birds were subjected to 14 hr of light/day as radiated by 60 W incandescent bulbs. Chickens consumed feed (standard commercial feed, automatic feeder) and water ad libitum. Four cages constituted one experimentalunit. Experimental and control units were series of cages distributed in alternate order. Red contact lenses (ABL-1) were implanted, according to Animalens, Inc. instructions, in the eyes of 100 chickens, whereas the other 100 chickens served as controls. DATA COLLECTION All data was collected for seven %-day periods from the 76th until the 104th wk of the hens’ life. Daily records for egg production and mortality were collected on the basis of each experimental unit. Egg weights were determined by l day collection of eggs from each experimental unit during each 28-day period. Because an automatic feeder was used, feed intake was not measured. At 105 wk of age, the fearfulness of six randomly selected chickens from each group (control and experimental) was determined. It was assessed by means of the tonic immobility (TI) test [9]. In order to induce the state of immobility, birds were restrained on their back. The amount of time, in seconds, required for each bird to right itself from this state of immobilitywas used as the measure of
RESULTSAND DISCUSSION Some of the chickens (10 to 20%) with the lenses in the present study developed eye irritations within 2 wk after the beginning of the experiment. Animalens, Inc. (5l did not disclose the possibility of this side effect, Researchers assumed that the experimental chickens had become used to the lenses and would recover, but during the experiment we found additional eye irritations. In spite of that, we decided to continue with the test in order to report a phenomenon which was never previously published. After 7 months a large portion (over 60%) of the experimental hens appeared to have eye irritations in both eyes. Normal hens in cages tend to react adversely to approaching humans [13]. Chickens with lenses didn’t respond to hand movement in front of their eyes and behaved like chickens in the dark or as if blind. At that point we decided to conclude the experiment so as not to cause additional discomfort to the chickens. Egg production, egg weights, egg mass, and mortality for both experimental and control groups appear in Table 1.No differences in those parameters were found between control birds and those with contact lenses. No differences were found in body weights (Table 2). Adams [7] found that control buds laid more eggs and had less mortality than did birds with lenses. It is possible that our results differ from those of Adams because of differ-
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GVARYAHU et al.
TABLE 1. Simple means of egg production, egg weight, egg mass, and mortality for contact lenses hens and controls ImeanskSE) ~~
GROUP
EGG PRODUCTION*
EGG WIG&
EGG
MASS^
MORTALITY~
% Hen Housed
g
kg Hen Housed
%
Control hens
59.0 k 1.9
66.9kO.S
7.720.3
10.0k4.8
Hens with lenses
60.5 k2.3
66.3k0.4
7.920.3
9.0k3.2
BODY WEIGHT
HEART WEIGHT
HEART WEIGHT
TI
kg
g
% per BW
sec
GROUP Control hens
1.7720.11
7.4 k0.3
0.42 kO.01
158 (25-240)
Hens with lenses
1.78r+0.11
10.3*k1.1
0.59*k0.06
66* (15-125)
heavier heart weights expressed as a percentage of body size. Additional clarification is required to discover the cause of the increased heart weight among the chickens with the lenses: stress, infections, discomfort, etc. The TI test revealed that birds with contact lenses are less fearful than the controls. These results are in accordance with the claim of Animalens, Inc. that chickens with contact lenses are docile and easily handled. Our assumption is that birds with contact lenses are less fearful because of impaired vision.
ences in ages. Young hens, unlike our hens which spend almost 2 yr in their cages before the experiment, are not used to the feeders and drinkers. Installing lenses just before moving the birds to the layer facility could explain the hens' inability to find the feed and thus to produce less and exhibit higher mortality. Chickens with lenses had significantly heavier hearts than did the controls (Table 2). Cunningham et al. [lo] suggested that stress that increases metabolic rates may increase heart size and found that hens of low rank as well as hens housed at high stocking rates had
CONCLUSIONS AND APPLICATIONS 1. Contact lenses have no beneficial effect on egg production and mortality. 2. Contact lenses appear to be associated with increase in eye irritations and thus their
application is discouraged.
REFERENCES AND NOTES ment object that reduces aggressiveness and mortality in caged laying hens. Physiol. Behav. 55:313-316.
1. Arbi, A, R.B. Cumming, and M. WodzickaTomaszewska, 1983. Effects of vision-restricting "polypeepers" on the behavior of laying hens during adaptation, feeding, on general activity, a onistic behavior, and pecking damage. Br. Poultry Sci. 84371-381. 2. Appleby, M.C., B.O. Hughes, and H.A. Elson, 1992. Social Behavior: Cannibalism. Pages 153-157 in: Poultly Production Svstems Behavior. Management and Welfare. CAB Intern&onal. Wallingford,
Uc.
3. Gvaryahq G., E Ararat, E, E Asat, M. Lev, J.I. Weller, B. Robiozon, and N. Snapir, 1994. An enrich-
4. Wise, R and D.C. Clarke, 1983. CASE Optical Distortion, Inc. Harvard Business School Case 9-575-072, Harvard Business School, Harvard, (TI'.
I
5. Animalens, Inc., One Hollis Street, Wellesley, MA 02181,
6. Pyrmk, R, N. Snapir, G. Goodman, and M. Perek, 1987. T h e effect of light wavelength on the production and uality of eggs of domestic hen. Theriogennol. 28:948-960.
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CONTACT LENSES FOR LAYING HENS
7. AdaR L , 1992. Effect of red plastic lenses on egg production, feed per dozen eggs, and mortality of laying hens. J. Appl. Poultry Res. 1:212-220.
11.Brounlee, Kk,1965. StatisticalTheory and Methodolo in Science and Engineering. 2nd Edition. John Wileysew York. NY.
8. Grossman, E and G. Gvaryahu, 1989. Environmental enrichment and contact lenses in laying hens. Page 68 in: Proc. 27th Ann. Conv. World Poultry Sci. Assn., Israel Branch, Zichron Ya'akov, Israel.
12. Siegcl, S., 1956. Nonparametric Statistics for the Behavioral Sciences. McGraw-Hill, New York, NY.
Faure, 1981.Tonic immobility 9. Jones,RB. and J.M. (righting time) in la 'ng hens housed in cages and pens. Appl. Anim. Ethol. r369-372. 10. Cunningham, D.L., A. van Tienhoven, and G. Gvaryahu,1988. Population size, cage area, and dominance rank effects on productivityand well-being of laying hens. Poultry. Sci. 67399406.
13. Jones, RB., 1J.H. Duncan,and B.O. Hughes, 1981. The assessment of fear in domestic hens exposed to a looming human stimulus. Behav. Proc. 6121-133.
ACKNOWLEDGEMENT The authors gratefully acknowledge the support of Jerry Hollander of Sun Valley, CA.
