Effects of short day (16L:8D) length on broilers: some physiological and welfare indices

Transcription

1 Effects of short day (16L:8D) length on broilers: some physiological and welfare indices S. ÖZKAN *, S. YALÇIN, Y. AKBAŞ, F. KIRKPINAR, Y. GEVREKÇİ, and L. TÜRKMUT Faculty of Agriculture, Department of Animal Science, Ege University, Izmir, Turkey. * corresponding author: sezen.ozkan@ege.edu.tr The aim of the present study was to evaluate the effects of continuous or short day length on body weight, plasma melatonin, triiodothyronine (T 3 ), and thyroxine (T 4 ) levels, H:L ratios, walking ability, and duration of tonic immobility in broilers. Day-old male broilers (176 chicks) were reared at floor pens in two identical rooms (4 pens/room) with a density of 16 chicks/m 2. Two lighting schedules were applied; continuous (C) (24 L) or short day (16L:8D) (SD), to chicks from 2 to 42 d. Body weights (BW) were recorded at 0, 21, and 42 d. Blood samples were obtained to measure melatonin concentration at 21 and 42 d at the middle of the light and dark periods. During the day-time (light) sampling, blood was also withdrawn to measure T 3, T 4, H:L ratios. Tonic immobility was obtained on the same days. SD significantly reduced early (21 d) growth (P<0.05). The difference between treatments was not significant at 42 d, despite numerically lower BW was observed in SD (2569 g) than C (2641 g). Sampling time had a significant effect on plasma melatonin and there was significant lighting by sampling time interaction (P<0.05) at both ages. Broilers reared at SD had significantly higher plasma melatonin concentration at mid-night (dark) ( and pg/ml for 21 and 42 d, respectively) than day-time (13.32 and 4.18 pg/ml for 21 and 42 d, respectively) while this diurnal melatonin rhythm was not existent in broilers from C. This result confirmed that continuous lighting disturbed the melatonin rhythm. T 3 and T 4 hormones did not differ with treatment with an exception of higher T 3 concentration of broilers under SD at 21 d than C (P<0.05). Lighting did not affect TI duration and H:L ratios of broilers suggesting that H:L and TI measurements did not give an evidence of reduced stress and fear levels of broilers under SD. This result might be due to low stocking density and moderately high light intensity (>20 lux) used in the experiment. However, SD resulted in lower lameness as reflected by birds with gait score 0 (P<0.05) at 42 d. In conclusion, SD resulted in reduced body weight at 21 d, however broilers attempted to compensate growth retardation by 42 d of age. It could be concluded that a clear diurnal rhythm of melatonin, when taking together with reduced lameness, was welfare advantage of SD. Keywords: broiler; lighting; melatonin; thyroid hormones; welfare Introduction Genetic selection for fast growth rate closely related with several physiological, behavioral and immunological problems such as skeletal and metabolic disorders and changes in behaviors in broilers. Photoperiodic regimens have a potential to reduce early growth and have welfare and performance advantages, especially those have an uninterrupted dark period, in broiler production compared to conventional continuous lighting (Gordon, 1994, Özkan et al., 2000, Stub and Vestegaard, 2001, Prescott et al., 2004). Because of daily light/dark schedules synchronize the endogen rhythms of birds, they had a great attention especially in animal-friendly production systems (Bessei, 2005). Continuous light may increase physiological stress by disturbing sleep and cause deprivation (Blockhuis, 1983). However, studies investigated the relations between lighting schedule and physiological stress

2 responses in birds are limited and there had been contradictory results (Blair et al, 1993; Zulkifli et al., 1998). Blair et al. (1993) reported that an increasing light schedule was beneficial in broiler resulting lower mortality (reduced SDS and ascites) and leg deformities. However, they did not find any difference in stress status among lighting treatments which was shown by similar H:L ratios. Zulkifli et al. (1998) observed greater H:L ratio and longer TI durations in broilers received continuous light than those kept under natural light 12L:12D conditions. Recently, Sanotra et al. (2002) suggested that light-dark schedules (16L:8D) either an increasing pattern or constant from 2 d of ages might be useful in reducing not only leg problems but also chronic fear. Melatonin is a neural hormone and secreted mainly by pineal gland in chicken and its production is associated with light-dark cycles (Zeman et al., 2004). Agapito et al. (2000) reported that a peak level of melatonin observed in chicks after 4 h of darkness under 12L:12D lighting program. Melatonin affects thermoregulation mechanism, reproductive and cardiopulmonary systems and behaviors of birds (Zeman, et al., 1993; Pang et al., 1996; Apeldoorn et al., 1999). An enhancement in immune response of broilers under light-dark cycles has also been shown by several workers (Kirby and Froman, 1991; Kliger et al., 2000). Antioxidative properties of melatonin has been reviewed by Reiter et al. (2001). This study was conducted to investigate the effect of constant short day length schedule (16L:8D) from 2 d of ages on body weight (BW), plasma melatonin and thyroid hormones, tonic immobility duration, H:L: ratio and walking ability in male broilers. Material and Method 176 day-old male chicks were randomly distributed to the floor pens with a stock density of 16 chicks/m 2 in two identical rooms (4 pens/room) varied with lighting program. 1) Control ( C ): birds were reared under continuous light (24 h), and 2) Constant short day (SD): 16L:8D lighting were applied to chicks from 2 d of ages till the end of the experiment. At 16L:8D schedule, lights turned off between and h. A gradual change in light intensity was applied to mimic down and dusk. Fluorescent lamps were used with homogenous light intensity among pens at birds level over 20 lux. Birds were fed to standard commercial diets. Individual body weights were recorded on d 0, 21 and 42. Blood samples of 10 birds from each group were obtained at 21 and 42 days of ages in the middle of light period and dark period (at 4 th h of darkness, and 8 th h of light) for melatonin analysis. Thyroid hormone analyses were performed only in the samples taken during lighting period and blood smears were prepared from day time samples to count white blood cells to estimate H:L ratios. Blood samples immediately centrifuged and plasma samples were kept at -20 C until analyzed. Melatonin concentration of plasma analyzed with RIA procedure using commercially available melatonin kits (Labor Diagnostika Nord GmbH & Co. KGAm Eichenhain Nordhorn, Germany) according to the manufacturers instructions. Plasma samples were radioimmunoassayed for T 3 and T 4 hormones using commercial kits (Coat-A-Count Canine T 3 and T 4 kits, DPC Corporation, CA, USA). The T 3 assay was performed according to manufacturer s instructions. However, 100-μl plasma sample was used in the T 4 analysis. At 21 and 42 d of ages, 12 birds per treatment were used for TI measurements. After body weight records on day 42, birds were evaluated for walking ability (Kestin et al., 1992). Body weight, weight gain, and thyroid hormone data were analyzed by ANOVA using JMP 5 statistics package (SAS Inst., 2002). Plasma melatonin concentrations were analyzed using GLM procedure of JMP testing lighting treatment and sampling time (dark/light) effects and two way interaction between them. Since there was a small number of birds with gait score>0, the effect of lighting treatment on the frequency of broilers either normal (gait score = 0) or impaired walking ability (gait score > 0) within treatments were tested by Chi-square test. TI duration and H:L ratios were analyzed by Kruskall-Wallis test. Significance level was based on P<0.05. Melatonin and thyroid hormone data were subjected to natural logarithm and square root transformation before ANOVA, respectively. However, back transformed means were presented on the tables.

3 Results and Discussion Body weights obtained in two lighting programs according to ages are given in Table 1. Constant short day schedule reduced body weight at 21 d. It seems that the birds in constant short day program, compensated their growth at 42 d of ages. However, the advantage of 8 h darkness on growth in broilers, as reported by Stub and Vestegaard (2001), was not the case in our study. Table 1. Body weights of broilers reared either C or SD light schedule Lighting Treatment Body weight (g) Day 0 C (24L) 43.4± ±9 2641±29 SD (16L:8D) 43.5± ±9 2569±28 P values < Results of melatonin levels are given in Table 2. Higher melatonin levels measured in the samples obtained in dark phase than in day time in both ages. Night time samples from the birds in 16L:8D schedule, have drastically higher melatonin levels than the samples from continuous light program which is consistent with the previous studies (Agapito et al., 2000; Zeman et al., 2004). Table 2. Effect of lighting regimen and blood sampling time on plasma melatonin concentration (pg/ml) of broilers Blood Sampling Time C (24L) SD (16L-8D) C (24L) SD (16L:8D) Mid-Day (Light) 23.10±1.52 a 13.32±1.52 a 11.82±1.46 a 4.18±1.69 a Mid-Night (Dark) 27.11±1.03 a ±1.34 b 17.64±1.32 a 48.91±1.26 b Variation Sources P values Lighting Blood Sampling Time Lighting X Time a,b Means within same age with no common superscript differ significantly (P<0.05) Plasma T 3 and T 4 concentrations are given in Table 3. Plasma T3 level of broilers reared under SD was significantly higher than C at 21 d of age. T4 levels did not change by treatments at both ages. This result agrees with the reports of Renden et al. (1994). They reported higher T 3 but lower T 4 during photoperiod under 18L-6D lighting schedule in broilers at 13 d of ages. T 3 hormone is known to be closely associated with feeding which is also a key factor influencing conversion of T 4 to T 3 with a diurnal pattern as reviewed by McNabb (2000). Higher T3 level also associates increased protein deposition (Decuypere and Buyse, 1988). Therefore the high level of T 3 hormone in SD group on d 21 probably relates food intake during the light period. Table 3. Plasma T 4 and T 3 concentration of broilers reared at either C or SD Lighting Treatment T4 (ng / ml) T3 (ng / ml) T4 (ng / ml) T3 (ng / ml) C (24L) 8.58± ± ± ±0.15 SD (16L:8D) 7.98± ± ± ±0.14 P values Tonic immobility durations measured in the experiment are given in Table 4. TI durations and H:L ratios did not differ with lighting treatment at both ages. This result is not in agreement with some of the previous studies (Zulkifli et al., 1998, Sanotra et al., 2002). However Stub and Vestegaard (2001) did not find a difference in TI durations between continuous lighting and 8 h of darkness as we found in this experiment.

4 Table 4. Tonic Immobility duration (s) and H:L ratio of broilers reared either at C or SD Lighting Treatment TI (s) H:L ratio TI (s) H:L ratio C (24L) 189± ± ± ±0.01 SD (16L:8D) 111± ± ± ±0.01 χ 2 P χ 2 : chi-square value The number of broilers with Gait score >0 was higher under C lighting (6/74) than under SD lighting (1/76) (χ 2 :4.279, P=0.038). Overall number of broilers with gait score >0 was very low (7 birds) in the experiment compared to some previous reports (Sanotra et al. 2002). This could be probably related to low stocking density and moderately high light intensity used in the experiment which may improve skeletal development by increasing activity (Gordon and Thorp, 1994). Results from this study clearly showed that the C lighting disturbs the melatonin rhythm in broilers. Higher T3 concentration of broilers at 21 d of age under SD schedule probably related to the increased feeding activity during light periods. In conclusion, SD resulted in reduced body weight at 21 d, however broilers attempted to compensate growth retardation by 42 d of age. H:L ratio and TI durations did not differ with lighting regimen, indicating that stress and fear levels of broiler were similar in both groups. However, short day lighting resulted in lower lameness as reflected by the lower number of birds with gait score >0. It could be concluded that a clear diurnal rhythm of melatonin, when taking together with reduced lameness, was welfare advantage of SD. References Agapito, M.T., Redondo, I., Plaza, R., Lopez-Burillo, S., Recio, J.M., and Pablos, M.I. (2000) Relationships between melatonin, glutathione peroxidase, glutathione reductase, and catalase. Endogenous rhythms on cerebral cortex in Gallus Domesticus. in Melatonin after Four Decades:An assesment of its Potential.(J. Olcese, edt) pp: Kluwer Academic Publisher Apeldoorn, E.J., Schrama, J.W., Mashaly, M.M., and Parmentier, H.K. (1999) Effect of melatonin and lighting schedule on energy metabolism in broiler chickens. Poultry Science 78: Bessei, W. (2005) Welfare of meat producing poultry- an overwiev, in Proceedings of 7 th European symposium on poultry welfare, June, Lublin, Poland. Animal Sci. Papers and Reports Vol. 23, Supp. 1: Blair, R., Newberry, R.C. and Gardiner, E.E. (1993) Effects of Lighting Pattern and Dietary Tryptophan Supplementation on Growth and Mortality in Broilers. Poultry Science 72: Blockhuis H.J. (1983) The relevance of sleep in poultry. World s Poultry Science Journal, 39: Decuypere, E. and Buyse, J. (1988) Thyroid hormones, corticosterone, growth hormone and samotomedins in avian species: general effects and possible implications in fattening, in: LECLERCQ, B. & WHITEHEAD, C.C. (Eds) Leannes in Domestic Birds,Genetic, Metabolic and Hormonal Aspects, pp (Kent, Butterwords). Gordon, S.H. (1994) Effect of Daylength and İncreasing Daylength Programmes on Broiler Welfare and Performance. World Poultry Science Journal, Vol 50, Gordon, S.H. and Thorp, B.H. (1994) Effect on light intensity on broiler live weight and tibial plateau angle. In proceedings of 9 th European Poultry Conference, Glasgow, UK. Vol:1, Kirby, J.D. and Froman, D.P. (1991) Evaluation of humoral and delayed hypersensitivity response in cockerels reared under constant light or a twelve hours light: twelve hours dark period. Poultry Science 70: Kestin, S.C., Knowles, T.G., Tinch, A.F., and Gregory, N.G. (1992) The prevalence of leg weakness in broiler chickens and its relationship with genotype. Veterinary Records 131: Kliger, C.A., Gehad, A.E., Hulet, R.M., Roush, W.B.; Lillehoj, H.S. and Mashaly, M.M. (2000)

5 Effects of photoperiod and melatonin on lymphocyte activities in male broiler chicken. Poultry Science 79: McNabb, F.M.A. (2000) Thyroids. In Sturkie s Avian Physiology. pp: Ed. G.C. Whittow. 5 th Edition, Academic Press, CA, USA. Özkan, S., Altan, Ö. ve Yalçın S. (2000) Effects of Resticted Lighting Schedules on Broiler Preformance. WPSA Congress 2000 Montreal, Canada. Pang, S.F., Pang, C.S., Poon, A.M.S., Wan, Q.; Song, Y. and Brown, G.M.(1996) An overwiev of melatonin and melatonin receptors in birds. Poultry and Avian Biology Review 7: Prescott, N.B., Kristensen, H.H. and Wathes, C.M. (2004) Light, in: Measuring and auditing broiler welfar. (C. Weeks and A. Buttreworth, eds) pp: Cambridge: CABI Publishing. Reiter, R.J., D-xian, Tan; Manchester, L.C. and Calvo, J.R. (2001) Antioxidative capacity of melatonin, in Handbook of antioxidants, second edition. (E. Cadenas. and L. Packer, eds) pp: New York:Marcel Dekker Incorporated. Renden, J.A., Lien, R.J., Oates, S.S., Bilgili, S.F. (1994) Plasma concentrations of corticosterone and thyroid hormones in broiler provided various lighting schedules. Poultry Science, 73: Sanotra G.S., Damkjer Lund, J. and Vestergaard, K.S. (2002) İnfluence of light-dark schedules and stocking density on behaviour, risk of leg problems and occurrence of chronic fear in broilers. British Poultry Science 43: SAS Institute, (2002) JMP Statistic and Graphics Guide Version 5.1. SAS Institute, Inc., Cary, NC. Stub, C. and Vestegaard, K.S. (2001) Influence of zinc bacitracin, light regimen and dustbathing on the health and welfare of broiler chickens. British Poultry Science 42: Zeman, M., Vyboh, P., Jurani, M, Lamosova, D., Kotsal, L., Bilcik, B., Blazicek, P. and Juraniova, E. (1993) Effects of exogenous melatonin on some endocrine, behavioral and metabolic parameters in japanese quail coturnix coturnix japonica. Comp. Biochem. Physiol. Vol.105A. No.2: Zeman, M., Pavlik, P., Lamosova, D., Herichova, I. and Gwinner, E. (2004) Development of Circadian Rhythmcity: Entrainment of Rhythmic Melatonin Production by Light and Temperature in the Chick Embryo. Avian and Poultry Biology Reviews 15 (3/4), Zulkifli, I., Rasedee, A., Syaadah, O.N., Norma, M.T.C. (1998) Daylength effects on stress and fear responses in broiler chickens. Asian-Australian Journal of Animal Science 11 (6):