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Effects of Cage Population on the Productive Performance of Layers1
Effects of Cage Population on the Productive Performance of Layers1 J. B. CAREY2 and F. L. KUO Department of Poultry Science, Texas A&M University, College Station, Texas 77843-2472 K. E. ANDERSON
ABSTRACT Two commercial layer strains (3,456 hens total) were used to examine the effects of bird population on productive performance. Four cage population sizes (6,8,12, and 24 birds per cage) were compared. All cages were 35.7 cm deep and varied in width (61.2, 81.6,122.4, and 244.8 cm). Floor space per bird was 364.1 cm2 and feeder space per bird was 10.2 cm in each cage configuration. Egg production and egg quality were measured from 20 to 72 wk of age. Strain differences were detected in hen-day egg production, egg mass, feed consumption, cracked egg percentage, Grade A eggs, Grade B eggs, peewee eggs, and large egg yield. There were no interactions between strain and cage population size. Cage population had no influence on hen-day egg production, mortality, feed conversion, egg size (peewee, small, medium, large, extra large), egg mass, lost eggs (by meat or blood spots), and percentage Grade B eggs. Percentage Grade A eggs, cracked egg percentage, and feed consumption were significantly influenced by cage population size. Hens housed at eight birds per cage had a greater percentage of Grade A eggs and a lower percentage of cracked eggs than those at other populations. Feed consumption was significantly greater for hens housed at 12 and 24 birds per cage compared with those at 6 and 8 birds per cage, respectively. (Key words: hen, cage population, strains, egg production, feed consumption) 1995 Poultry Science 74:633-637
1987; Davami et al, 1987; Cunningham et al, 1988; Brake and Peebles, 1992). RobinIt is well known that crowding birds son (1979) reported that smaller floor generally decreases egg production (Wil- space significantly reduced production son et al,, 1967; Adams and Jackson, 1970; only within small population size cages Al-Rawi et al, 1976; Cunningham, 1982; (two birds per cage). Adams and Craig Ouart and Adams, 1982; Roush et al, 1984; (1985) reviewed research on the effect of Hester and Wilson, 1986; Patterson and cage density on layer performance and Muir, 1986; Cunningham and Gvaryahu, concluded that egg production declined as bird density increased. Other aspects of cage design (cage depth, cage width, and feeder space) will Received for publication July 21, 1994. also affect layer productive performance Accepted for publication December 1, 1994. 1 The use of trade names in this publication does not (Adams and Jackson, 1970; Robinson, imply endorsement by the Texas Agricultural Experi- 1979; Ouart and Adams, 1982). Among ment Station or the North Carolina Agricultural Research Service, nor criticism of similar ones not men- these factors, cage population size has been infrequently studied and often has tioned. 2 To whom correspondence should be addressed. been confounded with other factors. Wells INTRODUCTION
633
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-5527
634
CAREY ET AL.
MATERIALS AND METHODS
A total of 3,456 birds were housed in 144 experimental units providing 1,728 birds of each strain with nine replicates at each of the four cage configurations. At 126 d, pullets were moved to a lightcontrolled layer house. Laying house experimental units consisted of 24 hens with no more than 12 hens originating from the same pullet house experimental unit. Hens were distributed among replicate groups randomly. Cage configurations were distributed randomly within all levels and rows of the three-level, four-row cage systems. All experimental units were the same depth (35.7 cm). Experimental units were partitioned into four cage widths of 61.2, 81.6,122.4, and 244.8 cm with 6, 8,12, and 24 birds per cage, respectively (Figure 1). This provided uniform floor space (364.1 cm2) and feeder space (10 cm) per bird. Because the cage width was modified to accomplish different cage population sizes, water space ranged from 2.6 to 3.4 birds per nipple. Nipple drinkers were located at the top of the cage near the
3SAS Institute Inc., Cary, NC 27511-8000.
Birds per cage
Cage Width (cm)
6
I
8
I
12
I
24
j
6 I 6 I 6 I 6 8
I 12
8 I
I
8 12
24
I
61.2
I
81.6
I
122.4
I
244.8
FIGURE 1. Experimental design of cage configurations. Cage depth was 35.7 cm for all cages.
front. Mash feed was provided for ad libitum consumption. During the laying period, daily nutrient intake was equal to or greater than the breeder's recommendations. Crude protein, metabolizable energy, calcium, and total phosphorus in layer rations were analyzed to be 17.1%, 3,002 kcal/kg, 4.1%, and .65%, respectively. Photoperiod increased from 13 h at 18 wk of age to 16 h at 24 wk of age and thereafter remained constant at 16 h. Production data were collected from 20 to 72 wk of age. Egg production, feed consumption, and mortality were monitored daily. Egg quality, egg weight, and egg grade were measured biweekly. Statistical calculations were processed by computer using SAS® Version 5.3 Data were analyzed with main effects being strain and cage population size. The model also evaluated the interaction of strain and cage population size. Mean differences were separated by the PDIFF (pair-wise t tests) option of the General Linear Models (GLM) procedure. RESULTS
Strain significantly affected egg production (Table 1). Strain A had lower hen-day egg production, egg mass, and feed consumption than Strain B (P < .01). However, feed conversion and mortality were not different between strains. Egg quality traits were also different between strains (Table 2). Strain A produced significantly fewer cracked eggs, more Grade A eggs, and fewer Grade B eggs than Strain B. Strain A produced significantly more peewee eggs and sig-
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
(1971) reported no effect of cage population size on egg production when feeder space and floor space were kept constant by widening the cage for larger colony size. The cage depth and bird density used in the study (Wells, 1971) were not similar to current industry standards (depth 45.7 cm, with two, three, four, and six birds per cage). Robinson (1979) also reported that birds in colonies of three, four, or six laid and survived equally well when floor space per bird and feeding space per bird were constant. These results indicated that further investigation was needed on how cage population size influences performance. We hypothesize that larger cages containing more birds but with constant floor and feeder space may be an alternative for egg producers. The present study was designed to examine the effects of cage population size on the productive performance of laying hens with uniform floor and feeder space.
CAGE POPULATION AND LAYER PERFORMANCE
635
TABLE 1. Effect of strain on performance statistics (20 to 72 wk) Strain
Hen-day production
Feed consumption
Egg mass
Feed conversion
Ir- fhrn Ml
(%) (g egg g ) .40 77.8B 43.8B 108.7B .40 48.5* 120.3* 84.7* .24 .77 .003 .36 AB ' Means within columns with no common superscript differ significantly (P < .01). ;
feed
A B SEM
Mortality (%) 10.8 11.1 .72
TABLE 2. Effect of strain on egg quality1 (20 to 72 wk) Strain
Grade A egg
Grade B egg
A B SEM
96.3* 94.9B .18
2.1b 2.6" .15
•
a b
(%)
Cracked egg
Loss egg
LIB 1.9* .11
.57 .68 .09
-
- Means within columns with no common superscript differ significantly (P < .05). *
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
nificantly fewer large eggs than Strain B influenced feed consumption agrees with (Table 3). the results of Wells (1971), although in Hen-day egg production, egg mass, that study there was only a trend for feed conversion, and mortality were not increased feed consumption as colony size affected by cage population size (Table 4). increased. The reasons for increased conBirds housed 6 and 8 birds per cage sumption in the present study could be consumed significantly less feed than due to behavioral differences and cage those housed 12 and 24 birds per cage. dimensions. Al-Rawi et al. (1976) reported Significant differences were detected that birds in larger groups interacted more among cage population sizes in percent- with each other. More birds in a cage age cracked eggs (Table 5). Birds housed 8 could cause more competition for feeding birds per cage had significantly fewer space and more bird activity, potentially cracked eggs than those housed 6 and 12 causing more energy expenditure and feed birds per cage, whereas birds housed 24 wastage. This could explain why birds birds per cage were intermediate. Loss eggs (by meat or blood spots) and percent- housed 12 and 24 birds per cage conage Grade B eggs were not affected by sumed significantly more feed than those cage population. Hens housed 8 birds per housed 6 and 8 birds per cage. However, cage produced significantly more Grade A Ouart and Adams (1982) and Cunningham eggs than those housed 12 and 24 birds and Gvaryahu (1987) indicated that as per cage, with 6 birds per cage intermedi- cage population group size increased feed consumption decreased. These two studies ate. Egg size was not affected by cage disagreed with the present study, but they population size (data not shown). Within were conducted with fewer birds per cage each egg size (peewee, small, medium, and floor space per bird was different large, extra large), no differences were among population sizes. Feed conversion was not affected by observed among cage population sizes. cage population size whereas feed consumption differed significantly. This could DISCUSSION be because the increase in feed consumpThe results shown herein demonstrat- tion resulted in a small increase in egg ing that cage population size significantly mass and a tendency toward a higher
636
CAREY ET AL. TABLE 3. Effect of strain on egg size 1 (20 to 72 wk)
Strain
Peewee
Small
Medium
Large
Extra large
43.9 b 45.5 a .53
17.6 18.9 .64
"".,}
A B SEM
4.7* 3.0B .18
6.5 6.4 .20
27.3 26.3 .68
a b
- Means within columns with no common superscript differ significantly (P < .05). - Means within columns with no common superscript differ significantly (P < .01). According to USDA weight class definitions.
A B
ham, 1982; Cunningham and Ostrander, 1982; Cunningham and Gvaryahu, 1987; Brake and Peebles, 1992). However in this study, hens housed 8 birds per cage produced significantly lower cracked egg percentage than those 6 and 12 birds per cage. Higher incidence of cracked egg percentage in cages with 12 and 24 birds per cage could be the result of increased bird activity. The higher incidence of percentage cracked eggs of hens housed at six birds per cage is unexplained. Hens housed 8 birds per cage produced significantly more Grade A eggs than those at 12 and 24 birds per cage. This could be accounted by having a significantly lower cracked egg percentage and slightly reduced Grade B eggs even though incidence of Grade B eggs was not different. Due to equivalent floor support mechanisms, these differences are not due to differences in floor rigidity. These effects may be due to different levels of bird movement within the cage. That egg sizes were not influenced by cage population size is supported by Al Rawi et al. (1976). This further indicates
TABLE 4. Effect of cage population size on performance statistics (20 to 72 wk) Cage population
Hen-day production
(birds per cage) 61 8 12 24 SEM
(%)
AB J
80.7 81.2 81.6 81.5 .51
E
gg mass
Feed consumption — (g/hen/d)
45.6 46.0 46.5 46.6 .34
113.0B 112.1" 116.7* 116.2* 1.11
-
Feed conversion (g e gg : g
feed
Mortality )
.40 .41 .40 .40 .004
' Means within columns with no common superscript differ significantly (P < .01). Cage width 61.2, 81.6, 122.4, and 244.8 cm, respectively; all cages 35.7 cm deep.
(%) 10.1 10.1 11.0 12.8 1.02
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
percentage of extra large eggs produced by larger cage populations, although these were not influenced by cage population size. The higher feed consumption among larger group sizes could account for the improvement in egg weight. Hen-day egg production was not affected by cage population size, which is consistent with results of Wells (1971) and Craig and Milliken (1989). These results contrast with the results of Cunningham et al. (1988), who reported that increasing cage population from four to six birds per cage resulted in a reduction of 2.1% in hen-day egg production. However, this was a result of birds that were among the lower dominance ranks in the cage. Robinson (1979) reported that mortality was not influenced by cage population size. Wilson et al. (1967) found that higher mortality in larger groups was primarily the result of cannibalism. In this study, causes of mortality were not determined. Egg quality traits such as egg weight, egg grade, and lost eggs are usually not affected by cage density (Wilson et al, 1967; Adams and Jackson, 1970; Cunning-
CAGE POPULATION AND LAYER PERFORMANCE
637
1
TABLE 5. Effect of cage population size on egg quality (20 to 72 wk) Cage population (birds per cage) 62 8 12 24 SEM
Grade A egg
Grade B egg
Cracked egg
Loss egg
1.6* l.lb 1.8» .5 a b .16
.54 .70 .64 .61 .13
(%) 95.6AB 96.3* 95.0" 95.5 B .25
2.3 1.9 2.6 2.5 .21
a b
- Means within columns with no common superscript differ significantly (P < .05). ' Means within columns with no common superscript differ significantly (P < .01). ^According to USDA grading standards. 2 Cage width 61.2, 81.6, 122.4, and 244.8 cm, respectively; all cages 35.7 cm deep. A B
REFERENCES Adams, A. W., and J. V. Craig, 1985. Effect of crowding and cage shape on productivity and profitability of caged layers: A survey. Poultry Sci. 64:238-242. Adams, A. W., and M. E. Jackson, 1970. Effect of cage size and bird density on performance of six commercial strains of layers. Poultry Sci. 49: 1712-1719. Al-Rawi, B., J. V. Craig, and A. W. Adams, 1976. Agonistic behavior and egg production of caged layers: Genetic strain and group-size effects. Poultry Sci. 55:796-807. Brake, J. D., and E. D. Peebles, 1992. Laying hen performance as affected by diet and caging density. Poultry Sci. 71:945-950. Craig, J. V., and G. A. Milliken, 1989. Further studies of density and group size effects in caged hens of stocks differing in fearful behavior, productivity and behavior. Poultry Sci. 68:9-16. Cunningham, D. L., 1982. Cage type and density effects on performance and economic factors of caged layers. Poultry Sci. 61:1944-1949.
Cunningham, D. L., and G. Gvaryahu, 1987. Effects on productivity and aggressive behavior of laying hens of solid versus wire cage partition and bird density. Poultry Sci. 66:1583-1586. Cunningham, D. L., and C. E. Ostrander, 1982. The effects of strain and cage shape and density on performance and fearfulness of white Leghorn layers. Poultry Sci. 61:239-243. Cunningham, D. L., A. van Tienhoven, and G. Gvaryahu, 1988. Population size, cage area, and dominance rank effects on productivity and well-being of laying hens. Poultry Sci. 67: 399-406. Davami, A., M. J. Wineland, W. T. Jones, R. L. Ilardi, and R. A. Peterson, 1987. Effects of population size, floor space, and feeder space upon productive performance, external appearance, and plasma corticosterone concentration of laying hens. Poultry Sci. 66:251-257. Hester, P. Y., and E. K. Wilson, 1986. Performance of white Leghorn hens in response to cage density and the introduction of cage mates. Poultry Sci. 65:2029-2033. Ouart, M. D., and A. W. Adams, 1982. Effects of cage design and bird density on layers. 1. Productivity, feathering, and nervousness. Poultry Sci. 61:1606-1613. Patterson, D. L., and W. M. Muir, 1986. Magnitude of genetic influence, cage type, and genotype by cage-type interactions on soft-shell and shellless egg production. Poultry Sci. 65:26-33. Robinson, D., 1979. Effects of cage shape, colony size, floor area and cannibalism preventatives on laying performance. Br. Poult. Sci. 20:345-356. Roush, W. B., M. M. Mashaly, and H. B. Graves, 1984. Effect of increased bird population in a fixed cage area on production and economic response of single comb white leghorn laying hens. Poultry Sci. 63:45-48. Wells, R. G., 1971. Studies on stocking arrangements for caged layers. World's Poult. Sci. J. 27: 361-366. Wilson, H. R., J. E. Jones, and R. W. Dorminey, 1967. Performance of layers under various cage regimes. Poultry Sci. 46:422-425.
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
that cage population has no influence on egg weight when floor space is kept constant. These data demonstrate that strain differences exist in productive performance statistics and that productive performance and livability of laying hens was not reduced by large cage populations. High feed consumption associated with larger cage populations could be addressed commercially by management factors such as light intensity, house temperature, and feed formulation. There may be commercial situations under which cage designs similar to this study may be desirable. The impact of these large cages on the ethology of hens warrants further investigation.
ABSTRACT Two commercial layer strains (3,456 hens total) were used to examine the effects of bird population on productive performance. Four cage population sizes (6,8,12, and 24 birds per cage) were compared. All cages were 35.7 cm deep and varied in width (61.2, 81.6,122.4, and 244.8 cm). Floor space per bird was 364.1 cm2 and feeder space per bird was 10.2 cm in each cage configuration. Egg production and egg quality were measured from 20 to 72 wk of age. Strain differences were detected in hen-day egg production, egg mass, feed consumption, cracked egg percentage, Grade A eggs, Grade B eggs, peewee eggs, and large egg yield. There were no interactions between strain and cage population size. Cage population had no influence on hen-day egg production, mortality, feed conversion, egg size (peewee, small, medium, large, extra large), egg mass, lost eggs (by meat or blood spots), and percentage Grade B eggs. Percentage Grade A eggs, cracked egg percentage, and feed consumption were significantly influenced by cage population size. Hens housed at eight birds per cage had a greater percentage of Grade A eggs and a lower percentage of cracked eggs than those at other populations. Feed consumption was significantly greater for hens housed at 12 and 24 birds per cage compared with those at 6 and 8 birds per cage, respectively. (Key words: hen, cage population, strains, egg production, feed consumption) 1995 Poultry Science 74:633-637
1987; Davami et al, 1987; Cunningham et al, 1988; Brake and Peebles, 1992). RobinIt is well known that crowding birds son (1979) reported that smaller floor generally decreases egg production (Wil- space significantly reduced production son et al,, 1967; Adams and Jackson, 1970; only within small population size cages Al-Rawi et al, 1976; Cunningham, 1982; (two birds per cage). Adams and Craig Ouart and Adams, 1982; Roush et al, 1984; (1985) reviewed research on the effect of Hester and Wilson, 1986; Patterson and cage density on layer performance and Muir, 1986; Cunningham and Gvaryahu, concluded that egg production declined as bird density increased. Other aspects of cage design (cage depth, cage width, and feeder space) will Received for publication July 21, 1994. also affect layer productive performance Accepted for publication December 1, 1994. 1 The use of trade names in this publication does not (Adams and Jackson, 1970; Robinson, imply endorsement by the Texas Agricultural Experi- 1979; Ouart and Adams, 1982). Among ment Station or the North Carolina Agricultural Research Service, nor criticism of similar ones not men- these factors, cage population size has been infrequently studied and often has tioned. 2 To whom correspondence should be addressed. been confounded with other factors. Wells INTRODUCTION
633
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-5527
634
CAREY ET AL.
MATERIALS AND METHODS
A total of 3,456 birds were housed in 144 experimental units providing 1,728 birds of each strain with nine replicates at each of the four cage configurations. At 126 d, pullets were moved to a lightcontrolled layer house. Laying house experimental units consisted of 24 hens with no more than 12 hens originating from the same pullet house experimental unit. Hens were distributed among replicate groups randomly. Cage configurations were distributed randomly within all levels and rows of the three-level, four-row cage systems. All experimental units were the same depth (35.7 cm). Experimental units were partitioned into four cage widths of 61.2, 81.6,122.4, and 244.8 cm with 6, 8,12, and 24 birds per cage, respectively (Figure 1). This provided uniform floor space (364.1 cm2) and feeder space (10 cm) per bird. Because the cage width was modified to accomplish different cage population sizes, water space ranged from 2.6 to 3.4 birds per nipple. Nipple drinkers were located at the top of the cage near the
3SAS Institute Inc., Cary, NC 27511-8000.
Birds per cage
Cage Width (cm)
6
I
8
I
12
I
24
j
6 I 6 I 6 I 6 8
I 12
8 I
I
8 12
24
I
61.2
I
81.6
I
122.4
I
244.8
FIGURE 1. Experimental design of cage configurations. Cage depth was 35.7 cm for all cages.
front. Mash feed was provided for ad libitum consumption. During the laying period, daily nutrient intake was equal to or greater than the breeder's recommendations. Crude protein, metabolizable energy, calcium, and total phosphorus in layer rations were analyzed to be 17.1%, 3,002 kcal/kg, 4.1%, and .65%, respectively. Photoperiod increased from 13 h at 18 wk of age to 16 h at 24 wk of age and thereafter remained constant at 16 h. Production data were collected from 20 to 72 wk of age. Egg production, feed consumption, and mortality were monitored daily. Egg quality, egg weight, and egg grade were measured biweekly. Statistical calculations were processed by computer using SAS® Version 5.3 Data were analyzed with main effects being strain and cage population size. The model also evaluated the interaction of strain and cage population size. Mean differences were separated by the PDIFF (pair-wise t tests) option of the General Linear Models (GLM) procedure. RESULTS
Strain significantly affected egg production (Table 1). Strain A had lower hen-day egg production, egg mass, and feed consumption than Strain B (P < .01). However, feed conversion and mortality were not different between strains. Egg quality traits were also different between strains (Table 2). Strain A produced significantly fewer cracked eggs, more Grade A eggs, and fewer Grade B eggs than Strain B. Strain A produced significantly more peewee eggs and sig-
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
(1971) reported no effect of cage population size on egg production when feeder space and floor space were kept constant by widening the cage for larger colony size. The cage depth and bird density used in the study (Wells, 1971) were not similar to current industry standards (depth 45.7 cm, with two, three, four, and six birds per cage). Robinson (1979) also reported that birds in colonies of three, four, or six laid and survived equally well when floor space per bird and feeding space per bird were constant. These results indicated that further investigation was needed on how cage population size influences performance. We hypothesize that larger cages containing more birds but with constant floor and feeder space may be an alternative for egg producers. The present study was designed to examine the effects of cage population size on the productive performance of laying hens with uniform floor and feeder space.
CAGE POPULATION AND LAYER PERFORMANCE
635
TABLE 1. Effect of strain on performance statistics (20 to 72 wk) Strain
Hen-day production
Feed consumption
Egg mass
Feed conversion
Ir- fhrn Ml
(%) (g egg g ) .40 77.8B 43.8B 108.7B .40 48.5* 120.3* 84.7* .24 .77 .003 .36 AB ' Means within columns with no common superscript differ significantly (P < .01). ;
feed
A B SEM
Mortality (%) 10.8 11.1 .72
TABLE 2. Effect of strain on egg quality1 (20 to 72 wk) Strain
Grade A egg
Grade B egg
A B SEM
96.3* 94.9B .18
2.1b 2.6" .15
•
a b
(%)
Cracked egg
Loss egg
LIB 1.9* .11
.57 .68 .09
-
- Means within columns with no common superscript differ significantly (P < .05). *
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
nificantly fewer large eggs than Strain B influenced feed consumption agrees with (Table 3). the results of Wells (1971), although in Hen-day egg production, egg mass, that study there was only a trend for feed conversion, and mortality were not increased feed consumption as colony size affected by cage population size (Table 4). increased. The reasons for increased conBirds housed 6 and 8 birds per cage sumption in the present study could be consumed significantly less feed than due to behavioral differences and cage those housed 12 and 24 birds per cage. dimensions. Al-Rawi et al. (1976) reported Significant differences were detected that birds in larger groups interacted more among cage population sizes in percent- with each other. More birds in a cage age cracked eggs (Table 5). Birds housed 8 could cause more competition for feeding birds per cage had significantly fewer space and more bird activity, potentially cracked eggs than those housed 6 and 12 causing more energy expenditure and feed birds per cage, whereas birds housed 24 wastage. This could explain why birds birds per cage were intermediate. Loss eggs (by meat or blood spots) and percent- housed 12 and 24 birds per cage conage Grade B eggs were not affected by sumed significantly more feed than those cage population. Hens housed 8 birds per housed 6 and 8 birds per cage. However, cage produced significantly more Grade A Ouart and Adams (1982) and Cunningham eggs than those housed 12 and 24 birds and Gvaryahu (1987) indicated that as per cage, with 6 birds per cage intermedi- cage population group size increased feed consumption decreased. These two studies ate. Egg size was not affected by cage disagreed with the present study, but they population size (data not shown). Within were conducted with fewer birds per cage each egg size (peewee, small, medium, and floor space per bird was different large, extra large), no differences were among population sizes. Feed conversion was not affected by observed among cage population sizes. cage population size whereas feed consumption differed significantly. This could DISCUSSION be because the increase in feed consumpThe results shown herein demonstrat- tion resulted in a small increase in egg ing that cage population size significantly mass and a tendency toward a higher
636
CAREY ET AL. TABLE 3. Effect of strain on egg size 1 (20 to 72 wk)
Strain
Peewee
Small
Medium
Large
Extra large
43.9 b 45.5 a .53
17.6 18.9 .64
"".,}
A B SEM
4.7* 3.0B .18
6.5 6.4 .20
27.3 26.3 .68
a b
- Means within columns with no common superscript differ significantly (P < .05). - Means within columns with no common superscript differ significantly (P < .01). According to USDA weight class definitions.
A B
ham, 1982; Cunningham and Ostrander, 1982; Cunningham and Gvaryahu, 1987; Brake and Peebles, 1992). However in this study, hens housed 8 birds per cage produced significantly lower cracked egg percentage than those 6 and 12 birds per cage. Higher incidence of cracked egg percentage in cages with 12 and 24 birds per cage could be the result of increased bird activity. The higher incidence of percentage cracked eggs of hens housed at six birds per cage is unexplained. Hens housed 8 birds per cage produced significantly more Grade A eggs than those at 12 and 24 birds per cage. This could be accounted by having a significantly lower cracked egg percentage and slightly reduced Grade B eggs even though incidence of Grade B eggs was not different. Due to equivalent floor support mechanisms, these differences are not due to differences in floor rigidity. These effects may be due to different levels of bird movement within the cage. That egg sizes were not influenced by cage population size is supported by Al Rawi et al. (1976). This further indicates
TABLE 4. Effect of cage population size on performance statistics (20 to 72 wk) Cage population
Hen-day production
(birds per cage) 61 8 12 24 SEM
(%)
AB J
80.7 81.2 81.6 81.5 .51
E
gg mass
Feed consumption — (g/hen/d)
45.6 46.0 46.5 46.6 .34
113.0B 112.1" 116.7* 116.2* 1.11
-
Feed conversion (g e gg : g
feed
Mortality )
.40 .41 .40 .40 .004
' Means within columns with no common superscript differ significantly (P < .01). Cage width 61.2, 81.6, 122.4, and 244.8 cm, respectively; all cages 35.7 cm deep.
(%) 10.1 10.1 11.0 12.8 1.02
Downloaded from http://ps.oxfordjournals.org/ at Northern Arizona University on May 23, 2015
percentage of extra large eggs produced by larger cage populations, although these were not influenced by cage population size. The higher feed consumption among larger group sizes could account for the improvement in egg weight. Hen-day egg production was not affected by cage population size, which is consistent with results of Wells (1971) and Craig and Milliken (1989). These results contrast with the results of Cunningham et al. (1988), who reported that increasing cage population from four to six birds per cage resulted in a reduction of 2.1% in hen-day egg production. However, this was a result of birds that were among the lower dominance ranks in the cage. Robinson (1979) reported that mortality was not influenced by cage population size. Wilson et al. (1967) found that higher mortality in larger groups was primarily the result of cannibalism. In this study, causes of mortality were not determined. Egg quality traits such as egg weight, egg grade, and lost eggs are usually not affected by cage density (Wilson et al, 1967; Adams and Jackson, 1970; Cunning-
CAGE POPULATION AND LAYER PERFORMANCE
637
1
TABLE 5. Effect of cage population size on egg quality (20 to 72 wk) Cage population (birds per cage) 62 8 12 24 SEM
Grade A egg
Grade B egg
Cracked egg
Loss egg
1.6* l.lb 1.8» .5 a b .16
.54 .70 .64 .61 .13
(%) 95.6AB 96.3* 95.0" 95.5 B .25
2.3 1.9 2.6 2.5 .21
a b
- Means within columns with no common superscript differ significantly (P < .05). ' Means within columns with no common superscript differ significantly (P < .01). ^According to USDA grading standards. 2 Cage width 61.2, 81.6, 122.4, and 244.8 cm, respectively; all cages 35.7 cm deep. A B
REFERENCES Adams, A. W., and J. V. Craig, 1985. Effect of crowding and cage shape on productivity and profitability of caged layers: A survey. Poultry Sci. 64:238-242. Adams, A. W., and M. E. Jackson, 1970. Effect of cage size and bird density on performance of six commercial strains of layers. Poultry Sci. 49: 1712-1719. Al-Rawi, B., J. V. Craig, and A. W. Adams, 1976. Agonistic behavior and egg production of caged layers: Genetic strain and group-size effects. Poultry Sci. 55:796-807. Brake, J. D., and E. D. Peebles, 1992. Laying hen performance as affected by diet and caging density. Poultry Sci. 71:945-950. Craig, J. V., and G. A. Milliken, 1989. Further studies of density and group size effects in caged hens of stocks differing in fearful behavior, productivity and behavior. Poultry Sci. 68:9-16. Cunningham, D. L., 1982. Cage type and density effects on performance and economic factors of caged layers. Poultry Sci. 61:1944-1949.
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that cage population has no influence on egg weight when floor space is kept constant. These data demonstrate that strain differences exist in productive performance statistics and that productive performance and livability of laying hens was not reduced by large cage populations. High feed consumption associated with larger cage populations could be addressed commercially by management factors such as light intensity, house temperature, and feed formulation. There may be commercial situations under which cage designs similar to this study may be desirable. The impact of these large cages on the ethology of hens warrants further investigation.