Mohammad A. JALAL
Sheila E. SCHEIDELER
Department of Animal Science
University of Nebraska
Lincoln, NE, U.S.A.
Introduction
Most laying hens are placed into cages in today's commercial egg industry. The aim of such practice is to reduce housing, equipment and labor costs per hen and keep the eggs cleaner. It is commonly believed that decreasing cage space per hen will increase the number of eggs per cage, thus offsetting the negative effects of crowding on productivity of the individual hen, thereby increasing profitability (Adams and Craig, 1985). This view started to change in the last decade of the twentieth century, with more emphasis on animal welfare issues (Anderson et al., 1995).
Cage effects on the performance of commercial laying hens are well documented. Reduced cage space allowance has been reported to decrease egg production (EP), egg weight (EW), feed intake (FI) and to increase mortality (Bell, 1981; Cunningham, 1982, Sandoval et al., 1991).
Few researchers have investigated the combined effect of cage space allowance and diet caloric content on hen and pullet performance. Jackson and Waldroup (1988) found that increased dietary nutrient density helped overcome the effects of limited feeder space associated with crowded cages, but the influence of diet was minimal when shallow cages were used and feeder space increased. Owings et al. (1967) reported decreased EP caused by reduced cage space allowance was partially overcome by increased dietary protein. More recently Brake and Peebles (1992) studied the effect of varying cage space allowances and lysine levels on laying hen performance. They reported no consistent effect of cage space allowance on production parameters and detected no interaction between lysine levels and cage space allowance.
New animal welfare guidelines put forth by United Egg Producers (UEP 2001) recommended a cage space allowance of 67 sq. inches per hen for smaller White Leghorn hens compared to current industry practice of 52-54 sq. inches per hen. As result of these new welfare guidelines, the objective of our research was to assess the effects of varying cage space allowances on a commercial laying hen strain fed differing levels of dietary ME.
Experimental Design
Four cage allowances (53, 64, 80 and 107 square inches per bird) were assigned to Single Comb White Leghorn hens from 50 to 65 weeks of age. Each cage space allowance was combined with three dietary ME treatments (2800, 2850, and 2900 kcal/kg) in a 3 x 4 factorial arrangement. Each treatment was randomly allotted to 6 replicate pens for a total of 72 pens. Individual pens were designated as experimental units and had varying numbers of hens; 3 (107 sq. inch), 4 (80 sq. inch), 5 (64 sq. inch), or 6 (53 sq. inch) for a total of 324 hens. Experimental pens (cages) dimensions were 16 x 20 inches in a stacked deck manure belt system. The experimental design was a randomized complete block design with 6 blocks and 12 pens per block.
Diets were formulated according to the recommendation of the Hy-Line W-36 breeders' manual and to meet National Research Council (1994) nutrient requirements of laying hens for all nutrients with the exception of energy (Table 1). Diets were standard corn-soybean meal diets, isonitrogenous, and containing three varying levels of ME (2800, 2850, 2900 kcal/kg). Animal vegetable blended fat was the source used to increase dietary energy. The intermediate diet was obtained via blending high and low ME diets.
Measurements included daily feed intake, ME intake (MEI) and egg production, weekly egg weights and egg mass (EM), and biweekly hen weights (HW) and body weight change (BWC).
Data was analyzed using the Repeated Measures Analysis of SAS software (Proc Mixed, SAS Institute, 1998) for a randomized complete block design and a 3 x 4 factorial arrangement.
Results
Variation in cage space allowance had a significant effect on feed intake (Table 2). Hens given 107 sq. inch significantly (P<0.001) had a greater feed intake than those housed at 64 and 53 sq. inch, but not significantly higher than those housed at 80 sq. inch. Dietary metabolizable energy level had no significant effect on feed intake. A similar effect can be observed with MEI (Table 2). Hens housed at 107 sq. inch had significantly (P<0.001) higher MEI than hens housed at 64 and 80 sq. inch by differences of 18.14 and 17.91 kcal/hen/day respectively.
Egg production was significantly (P<0.0001) improved for hen housed at 107 sq. inch compared to other densities and across all energy levels (Table 2). An interaction between dietary ME and cage space allowance was close to significance (P<0.08), with hens fed low ME and housed at 107 sq. inch having highest EP value of 89.78%. Egg mass exhibited a similar trend to egg production, as hens with greater cage space having a significantly (P<0.0001) larger EM value than those housed at 80, 64 and 53 sq. inch (Table 2). There were no significant treatment effects observed on egg weight (Table 2).
There were no significant effects of either dietary ME or cage space allowance on hen body weight (Table 3), however, there was a significant interaction effect on change in body weight (Table 3). Hens housed at 80 sq. inch/hen and fed low ME diet exhibited the greatest weight gain and were significantly (P<0.05) higher those fed other levels of ME at the same density. Hens fed the intermediate level of ME had greater BWC (P<0.05) than those fed high and low ME when housed at 64 sq. inch, while BWC was highest for those fed high ME at 53 sq. inch/hen.
ME efficiency of egg production (MEEP) was significantly (P<0.05) affected by cage space (Table 4). Hens housed at 107 and 80 sq. inch had greater (MEEP) in contrast to hens housed at 64 and 53 sq. inch, respectively, and across all diets. Digestible available ME (AME) was significantly affected by dietary ME level in the diet (Table 4). Hens fed high ME had significantly greater digestible AME than those fed intermediate and low ME, with differences of 107 and 118 kcal ME/kg, respectively. There were no significant effects of either cage space allowance and/or energy level on maintenance energy intake of laying hens.
Conclusions
It is evident that increasing cage space allowance and decreasing number of birds per pen had a positive overall effect on performance. Cage density reduction significantly increased production parameters such as feed intake, ME intake, egg production, egg mass, and improved energetic efficiency of laying hens. There was no effect of ME levels on laying hen performance at varying cage space allowances except on digestible AME, which as highest for hens fed the high ME, levels.
References
Adams, A. W., and J .V. Craig, 1985. Effects of crowding, and cage shape on productivity and profitability and caged layers: A survey. Poultry Sci. 64:238-242.
Anderson, K. E., G. B. Havenstein, and J. Brake, 1995. Effects of strain and rearing dietary regimens on brown-egg pullet growth and strain, rearing dietary regimens, density, and feeder space effects on subsequent laying performance. Poultry Sci. 74:1079-1092.
Bell, D., 1981. Cage selection and management. Feedstuffs 53(9):20-24.
Brake, J. D., and D. Peebles, 1992. Laying hen performance as affected by diet and cage density. Poultry Sci. 71:945-950.
Cunningham, D.L., 1982. Cage type, and density effects on performance and economic factors of caged layers. Poultry Sci. 61:1944-1949.
Jackson, M. E., and P. W. Waldrup, 1988. The effect of dietary nutrient density and number of hens per cage on layer performance in two different cage types. Nutr. Rep. Int. 37:1027-1035.
National Research Council, 1994. Nutrient Requirements of Poultry, 8th rev. ed. National Academy Press, Washington, DC.
Owings, W. J., S. L. Balloun, W. W. Marion, and J. M. J. Ning, 1967. The influence of dietary protein level and bird density in cages on egg production and liver fatty acids. Poultry Sci. 46:1303.(Abstr.)
Sandoval, M., R .D. Miles, and R. D. Jacobs, 1991. Cage density and house temperature gradient effects on performance of white leghorn hens. Poultry Sci. 70 (Suppl. 1):103.(Abstr.)
United Egg Producers, 2001. Tell United Egg Producers they need more to do to help hens. upc-online.org/ spring2001.
From Proceedings of the "Midwest Poultry Federation Convention", St. Paul, Minnesota, U.S.A.
