The effects of conventional versus cage housing and inorganic versus organic selenium on feathering in broilers

It has been suggested that in the not too distant future broilers will be produced in cages (Smith, 1972). From the mid-1960s to the early 1980s, many attempts were made to design cage facilities for the rearing of broiler chickens from hatch to market age. Unfortunately, none of these early cage systems allowed economical broiler production because there were high incidences of downgrades (Lloyd, 1969), breast blisters (Andrews and Goodwin, 1973), soft, distorted and broken bones (Merkley, 1976), poor feathering (Andrews et al., 1975; Bayer et al., 1976) and overall poor performance (Andrews and Goodwin, 1973; Andrews et al., 1975; Bayer et al., 1976).

Andrews and Goodwin (1973) reported that the primary cause for lack of success in rearing broilers in cages was due in part to the lack of proper materials for the development of cages. Recently, a cage rearing system was designed (Broilermatic® Cage System, Farmer Automatic of America) that appears to have eliminated many of the early problems associated with cage rearing of broilers (Havenstein et al., 1998). This caging system is gaining popularity around the world but many questions have been raised concerning production and performance of broilers reared in the system.

Selenium supplementation of poultry rations is a routine procedure. Sodium selenite has been the traditional source of supplementation (Leeson and Summers, 1991). Recently, organic selenium from yeast (Sel-Plex, Alltech Inc.), a more active form of selenium in chickens than selenite (Cantor et al., 1975; Collins et al., 1993), has become widely used in several countries, e.g., Japan, Switzerland, and Finland to name but a few. Thompson and Scott (1969), Scott et al. (1982) and Leeson and Summers (1991) have shown that selenium is required for maximum performance of chickens.

Edens (1996, 1998) reported that feathering rate of auto-sexed, slow feathering males was enhanced significantly with dietary supplementation of organic selenium (Sel-Plex). Enhanced feathering with Sel-Plex compared to sodium selenite at levels of 0.1, 0.2, or 0.3 mg/kg of diet was observed in trials conducted in both the spring and summer seasons. These observations were unexpected even though it had been reported that selenium apparently was involved in feathering and feather development (Thompson and Scott, 1969; Supplee, 1966). Since poor feathering has been associated with production of broilers in cages (Andrews et al., 1975; Bayer et al., 1976), an investigation was conducted to determine if organic selenium as Sel-Plex could influence the feathering rate of both females and slow feathering males reared either in a Broilermatic Cage System or in a conventional litter covered floor, curtain sidewall rearing environment.


MATERIALS AND METHODS

A summer experiment used feather-sexable broiler chickens (Arbor Acres X Arbor Acres) placed in litter covered floor pens or in pens in the Broilermatic® Cage System at standard stocking densities. Males and females were reared separately in this experiment.

The diets were supplemented with two selenium sources: sodium selenite and selenium yeast (Sel-Plex, Alltech, Inc) at a level of 0.2 mg/kg of feed for each of these two selenium forms. Brooding temperature and light management within the Broilermatic® Cage System (Havenstein et al., 1998) and the conventional houses were consistent with current broiler management practices. The litter in the conventional broiler house consisted of pine wood shavings top-dressed over built-up litter. The experimental diets consisted of the North Carolina Agricultural Research Service starter diet: 3154 kcal/kg metabolizable energy (ME), 21% crude protein (CP) (1-3 weeks); grower diet: 3135 kcal ME/kg, 18.1% CP (4-5 weeks), and finisher diet: 3172 kcal ME/kg, 15.4% CP (6 weeks).

Body weights and feed conversions (FCR) were determined at 3 and 6 weeks of age (6 week data are presented here), and mortality was recorded on a daily basis. At 2, 3, 4, 5 and 6 weeks of age, feather tracts on the back (interscapular cape, dorsal, pelvic, dorsal caudal tracts combined), breast (pectoral and sternal tracts combined), thigh (femoral tract- rear body and lower thigh, combined), neck (dorsal cervical and ventral cervical combined), tail (greater and lesser sickle feathers), and wings (upper coverts) were scored subjectively on the basis of feather size and skin surface covered. Feathering scores ranged from 0 (poorest) to 5 (best) for each tract. The regional feathering scores were determined, and scores for the different feather tracts were averaged for a whole body feathering score. Data on feathering were partitioned by sex, dietary selenium source and housing environment.

Data were subjected to statistical analysis using the General Linear Models Procedure of SAS (1994). Analysis of variance was conducted for each parameter, and the level of significance was set at a minimum at P<0.05.


RESULTS AND DISCUSSION

Body weights were equivalent between sodium selenite and Sel-Plex fed broilers in both the conventional and cage house (Table 1). Broilers in the cage house tended to be slightly, but not significantly, heavier than those in the conventional house. Feed conversion ratios (FCR) were equivalent for birds within a housing environment even though there were very small increases in FCR for those birds given Sel-Plex (Table 1). However, the major difference in FCR was between housing environments with the birds in the cage house showing an improvement in FCR of 80 points. There were no mortality differences between housing environments or selenium forms (Table 1). These observations on performance were consistent with earlier observations on the performance of broilers given either sodium selenite or Sel-Plex (Edens, 1996, 1998).




The data from this experiment showed that Sel-Plex induced more rapid whole body feathering in the slow feathering males as well as in the normal feathering females (Figure 1). This influence of selenium yeast was evident at three weeks of age and persisted through six weeks of age. These data show that the females had a greater feathering rate than the males throughout the six weeks of the experiment. Females approached full feathering at five weeks of age, but males were still lagging behind females even at six weeks of age.

Datawere partitioned to study the feathering rate on different body regions (Figures 2-7). There was an effect of Sel-Plex on female back feathering at only three weeks of age (Figure 2). At five weeks of age, nearly complete feathering of the backs of females was evident in groups given either sodium selenite or Sel-Plex. In males, back feathering was very slow in comparison to females (Figure 2). However, there was a significant Sel-Plex effect causing faster back feathering in males from three weeks of age through six weeks of age. Full back feathering in males with Sel-Plex supplementation was evident at six weeks, but those males given sodium selenite were not fully back feathered even at six weeks of age.







Breast feathering was slower than back feathering (Figure 3). The slower feathering rate on this body surface possibly may be related to the fact that the birds spend a great deal of their time resting on sternal feathers and may actually suffer a feather loss on this region due to increased contact with the cage or litter floor. Pectoral feathering, which was not scored separately, developed rapidly in females and in many males. There was, however, a Sel-Plex stimulation of faster feathering in both males and females (except at four weeks of age) when comparisons were made with the sodium selenite effect on feathering. However, breast feathering, even with Sel-Plex, was still slower in males than in females.




Thigh feathering was slower than back feathering but faster than breast feathering in both males and females (Figure 4). Nevertheless, Sel-Plex in both males (except at two weeks of age) and females caused more rapid thigh feathering than did sodium selenite through six weeks of age.

Feathering of the wings was faster in Sel-Plex treated females and males than in birds given sodium selenite (Figure 5). This increased feathering rate was evident at three weeks of age and persisted through six weeks of age. As seen in other regions of the body surface, females feathered their wings faster than did the males.
Neck feathering was delayed until three weeks of age in both males and females when the first growth of feathers in this region became evident (Figure 6). Females feathered the neck faster than did the males. At three weeks of age the females showed a significantly increased feathering of the neck, but from four through six weeks of age, there were no differences between feathering rates of sodium selenite and Sel-Plex supplemented birds (Figure 6). By five weeks of age, neck feathering was nearly complete in the females, but even at six weeks of age the males had not attained complete neck feathering.

Tail feathering rates in females (Figure 7) was stimulated by Sel-Plex as early as two weeks of age and persisted through six weeks of age. Tail feathering in females was significantly faster than feathering of the tail in the males (Figure 7). Even though feathering in the males was significantly slower in males than females, there was still a significant stimulation of feather growth at three and four weeks of age in the males given Sel-Plex.




There was also a significant housing effect on feathering rate. Generally, whole body feathering was stimulated more by Sel-Plex in females reared in the conventional broiler house (Figure 8). Even in females given sodium selenite, there was an increase in feathering rate in those birds in the conventional house compared with those in the cage house.







In males, Sel-Plex caused a faster feathering rate than did the sodium selenite (Figure 9). A difference between conventional and cage rearing in feathering rate was not evident until five weeks of age, and this advantage persisted through six weeks of age. Overall, whole body feathering was fastest in the conventional house in birds given Sel-Plex.







The mechanism associated with increased feathering rates of broiler chickens supplemented with Sel-Plex in their diets has not been established. Improvement in feathering with Sel-Plex was seen as early as three weeks of age, and this improvement was evident through six weeks of age.

In this case, for summertime feathering, Sel-Plex produced better feathering than did sodium selenite. These data suggest that the improved feathering was directly related to the improved retention of organic selenium, and that selenoamino acids such as selenomethionine or selenocysteine were used for keratin synthesis in feather production thereby sparing the cysteine pool in liver andmuscle glutathione which is normally used (Goto and Okamoto, 1965; Murphy and King, 1985). Since organic selenium is retained in tissues to a greater degree than is selenite selenium (Cantor et al., 1975; Collins et al., 1993), it stands to reason that during times when there is a demand for feather synthesis, selenium yeast would be a better source of selenium than selenite. Sel-Plex feed supplementation was reported to facilitate better feathering rates during both cool and hot seasons in slow feathering males (Edens, 1996; 1998), and currently we find that not only males but females feathered better when fed Sel-Plex.

Selenium is a structural component of the glutathione peroxidase system which acts as an antioxidant decreasing numbers of intracellular reactive oxygen metabolites (Tappel, 1987). In order for selenium to be effective in the activation of this enzyme system, the selenite and selenate forms must be converted to the selenide form before selenoproteins are synthesized. Cysteine must combine with selenide to form selenocysteine via a tRNA-mediated process, and this is a very limiting process in mammals (Esaki et al., 1979). Selenocysteine then serves as the active precursor of selenoproteins including glutathione peroxidase. Therefore, it is possible that the improved feathering rate in broilers supplemented with Sel-Plex organic selenium may be related to improved antioxidant activity, but this remains to be elucidated.

The improved feathering rate in broilers, especially in the slow feathering males, suggested that organic selenium might be modifying gene action. Slow feathering is regulated by a dominant sex-linked K gene whereas the k+ recessive allele regulates rapid feathering found in females. The slow feathering K gene is expressed in feather-sexed male broiler chickens and the slow feathering trait in these birds is evident for several weeks after hatch. The slow feathering trait in broilers apparently does not affect performance in well maintained flocks (Dunnington and Siegel, 1986; Lowe and Merkley, 1986; Merkley and Lowe, 1988).

Therefore, the supplementation of organic selenium, a more active form of selenium than sodium selenite (Cantor et al., 1975; Collins et al., 1993), may suppress the expression of aKgene product or it may be facilitating a k+ gene product releasing the birds to show more rapid feathering. If this is the case, selenium from the organic selenium Sel-Plex source also could be affecting the expression of other genes. Additional studies are required to elucidate the mode of action of selenium yeast on feathering rates in poultry.


SUMMARY

Performance parameters such as feed conversion ratios, body weights, and mortality were unaffected by selenium source. However, Sel-Plex induced more rapid whole body feathering in the slow feathering males as well as in the normal feathering females. This influence of Sel-Plex was evident at three weeks of age and persisted through six weeks of age. Females had a greater feathering rate than the males throughout the 6 weeks experiment.

Females approached full feathering at five weeks of age, but males were still lagging behind females even at six weeks of age. Feathering of broilers in the conventional house was slightly better than the feathering of broilers in the cage house. The mechanism for improved feathering rate in normal feathering females and slow feathering males given Sel-Plex has not been determined. However, Sel-Plex may be decreasing oxidative stress, or organic selenium may be a required component of a biochemical pathway involved in feathering that may be blocked by the presence of the K gene on the w chromosome.


REFERENCES

Andrews, L. D., and T. L. Goodwin. 1973. Performance of broilers in cages. Poultry Sci. 52:723-728.

Andrews, L. D., G. S. Nelson, G. C. Harris, Jr. and T. L. Goodwin. 1975. Performance of five strains of broilers in a four tier cage system with plastic floors. Poultry Sci. 54:54-58.

Bayer, R. C., F. V. Muir, C. B. Chawan and A. T. Bryan. 1976. Infected feather follicles in cage reared broilers. Poultry Sci. 55:1194-1200.

Cantor,A. H., M. L. Langevin , T.Naguchi and M. L. Scott. 1975. Efficacy of selenium in selenium compounds and feedstuffs for prevention of pancreatic fibrosis in chicks. J. Nutri. 105:106-111.

Collins, V. C., A. H. Cantor, M. J. Ford and M. L. Straw. 1993. Bioavailability of selenium in selenized yeast for broiler chickens. Poultry Sci. 72 (Suppl. 1):85.

Dunnington, E. A. and P. B. Siegel. 1986. Sex-linked feathering alleles (K, K+) in chicks of diverse genetic backgrounds. 1. Body temperatures and body weights. Poultry Sci. 65:209-214.

Edens, F. W. 1996. Organic selenium: from feathers to muscle integrity to drip loss: five years onward no more selenite! In: Biotechnology in the Feed Industry. Proc. of the 12th Annual Symposium. (T.P. Lyons and K.A. Jacques, eds). Nottingham University Press, Nottingham, UK. pp. 165-185.

Edens, F.W. 1998. Feathering rate affects male broiler performance. Misset- World Poultry 14(6):20-22.

Esaki, N., H. Tanaka, S. Uemura, T. Suzuki and K. Soda, 1979. Catalytic action of L-methionine-g-lyase on selenomethionine and selenols. Biochemistry, 19:407-410.

Goto, I. and S. Okamoto. 1965. Blood reduced glutathione levels and plasma protein constituents in molting hens. Japan Poultry Sci. 2:33-36.

Havenstein,G. B., J. L. Grimes, P. R. Ferket, C. R. Parkhurst, F.W. Edens, J. Brake and J. H. van Middelkoop. 1998. Recent experiences with reduced or non-litter systems for growing broilers and turkeys. In: Proceedings: 1998 National Poultry Waste Management Symposium. Springdale, AR. October 19-21, 1998. pp. 225-240.

Leeson, S. and J. D. Summers. 1991. Commercial Poultry Nutrition. University Books, Guelph, Ontario, Canada. Lloyd, R.W. 1969. Growing broilers in cages. Poultry Digest, 28:542-545.

Lowe, P. C. and J. W. Merkley. 1986. Association rate of feathering genotypes in broilers with production and carcass composition traits. 1. Effect of genotypes, sex, and diet on growth and feed conversion. Poultry Sci. 65:1853-1858.

Merkley, J. W. 1976. Increased bone strength in coop-reared broilers provided fluoridated water. Poultry Sci. 55:1313-1319.

Merkley, J. W. and P. C. Lowe. 1988. Association rate of feathering genotypes in broilers with production and carcass composition traits. 2. Effect of genotypes and diet on processing traits and lipid deposition. Poultry Sci. 67:914-919.

Murphy, M. E. and J. R. King. 1985. Diurnal variation in liver and muscle glutathione pools of molting and non-molting white-crown sparrows. Physiol. Zool. 58: 646-654.

SAS Institute. 1994. SAS User’s Guide: Statistics. SAS Institute, Cary, NC USA.

Scott, M. L., M. C. Nesheim and R. J. Young. 1982. Nutrition of the Chicken. 3rd Edition. M. L. Scott & Associates, Ithaca, NY.

Smith,W. M. 1972.Whither cages in broilers? Poultry Digest, 31:76-77.

Supplee, W. C. 1966. Feather abnormality in poults fed a diet deficient in vitamin E and selenium. Poultry Sci. 45:852-854.

Tappel, A. L. 1987. Glutathione peroxidase and other selenoproteins. In: Selenium in Biology and Medicine. G. F. Combs, Jr., O. A. Levander, J. E. Spallholz and J. E. Oldfield, ed. Van Nostrand Reinhold Co., New York, NY. pp 122-132.

Thompson , J. N. and M. L. Scott. 1969. Role of selenium in the nutrition of the chick. J. Nutri. 97:335-342.



Authors: F.W. EDENS, C.R. PARKHURST and G.B. HAVENSTEIN
Department of Poultry Science, North Carolina State University, Raleigh, North Carolina, USA