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Hematocrit as An Indicator of Egg Production in Turkey Breeder Hens
Hematocrit as An Indicator of Egg Production in Turkey Breeder Hens J. A. PROUDMAN and B. C. WENTWORTH Department of Poultry Science, University of Wisconsin, Madison, Wisconsin 53706 (Received for publication August 25, 2976)
Poultry Science 56:807-809, 1977
INTRODUCTION The decline in egg p r o d u c t i o n which characteristically occurs in a flock of t u r k e y breeder hens as t h e breeding season advances represents a major e c o n o m i c loss t o t h e t u r k e y breeder. Any a t t e m p t t o t e m p e r this loss t h r o u g h removal or t r e a t m e n t of u n p r o d u c t i v e hens, or to s t u d y t h e physiological events associated with cessation of egg p r o d u c t i o n , requires early identification of hens t h a t are going o u t of production b u t have n o t y e t exhibited either b r o o d y behavior or inability t o evert t h e oviduct for insemiantion. Although a n u m b e r of physiological parameters might be postulated t o reflect, and perhaps predict, t h e changing reproductive status of t h e breeder hen, only a m e t h o d which is simple, rapid a n d inexpensive will have practical value in screening large flocks of breeder hens u n d e r commercial conditions. D o m m and Taber ( 1 9 4 6 ) have observed t h a t , in t h e chicken, t h e period of highest egg p r o d u c t i o n coincides with t h e lowest red blood cell c o u n t . Bell ( 1 9 5 7 ) r e p o r t e d t h a t laying hens have a lower packed cell v o l u m e t h a n d o non-laying h e n s . Winter ( 1 9 3 5 ) f o u n d lower levels of h e m o g l o b i n in t h e blood of laying hens
Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison.
than in non-laying hens. These differences are presumably a reflection of t h e different horm o n a l states of laying and non-laying birds. Estrogen administration is k n o w n t o result in a decline in t h e h e m a t o c r i t of m a n y species, including chickens (Taber et al., 1 9 4 3 ; D o m m and Taber, 1 9 4 6 ) , quail ( W e n t w o r t h , 1 9 7 0 ) and rats (Vollmer and G o r d o n , 1 9 4 1 ) . Similar changes occur when e n d o g e n o u s estrogen secretion is stimulated by administration of g o n a d o tropins (Vollmer and G o r d o n , 1 9 4 1 ) . T h e p u r p o s e of t h e present w o r k was t o d e t e r m i n e t h e regression of egg p r o d u c t i o n associated with h e m a t o c r i t in t u r k e y breeder hens and t o assess t h e value of this determination in t h e identification of u n p r o d u c t i v e birds. MATERIALS AND METHODS Eighty spring-hatched Large White t u r k e y hens were reared as previously described (Mashaly and W e n t w o r t h , 1974). The birds were divided i n t o t w o pens of 4 0 birds each and received 1 4 hours of light per day during t h e reproductive season (January t h r o u g h May). Birds were housed in an uninsulated, pole-type structure such t h a t pen t e m p e r a t u r e s differed little from natural conditions. T r a p nesting was used t o d e t e r m i n e t h e daily egg p r o d u c t i o n for individual hens. T h e egg collection procedures e m p l o y e d t h r o u g h o u t t h e reproductive season were designed t o encourage
807
Downloaded from http://ps.oxfordjournals.org/ at University of Queensland on April 29, 2015
ABSTRACT Weekly hematocrit measurements were correlated with weekly egg production throughout the breeding season of Large White turkey hens. A highly significant negative regression of egg production associated with hematocrit was observed, occurring without regard to differences in the incidence of broodiness in the flocks under study. Approximately 20% of the total variance in egg production was accounted for by the regression on hematocrit. A high hematocrit (>45%) was a fairly accurate indicator of poor production; however, not all hens which laid poorly (<33% production) during a weekly period exhibited a high hematocrit. Virtually all hens having a hematocrit of 48% or greater were totally out of production during the weekly period surrounding the hematocrit measurement. The hematocrit may be a useful method for rapid identification of a significant proportion of the unproductive hens in a turkey breeder flock. Elimination of environmental temperature extremes may enhance the usefulness of this technique.
808
PROUDMAN AND WENTWORTH
TABLE l.—Mean weekly percent egg production for groups of Large White turkey hens exhibiting a high or a low incidence of broodiness
Production week
broodiness group
High broodiness group
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
49.3 61.8 61.8 60.8 62.3 59.7 48.0 48.7 54.6 51.6 44.7 45.9 48.0 42.2 48.1 45.5 43.6 42.5 42.1 38.6
45.4 61.5 56.8 56.0 48.7 41.0 37.4 31.1 36.6 43.8 37.8 31.7 30.5 31.3 32.4 30.1 26.3 22.4 23.2 23.0
Low
formed prior to regression analysis, including transformation of each variable to its log, square root and inverse, and transformation of both variables to logs and square roots. These preliminary calculations showed that the greatest proportion of the total variance in the data could be accounted for by the regression of egg production on the inverse of the hematocrit. RESULTS AND DISCUSSION
The weekly mean percent egg production for each pen throughout the reproductive season is presented in Table 1. It is apparent that the management practices employed in egg collection exerted a marked effect upon the incidence of broodiness, as reflected in percent egg production. Regression analysis of egg production on the inverse of hematocrit for hens showing the lower incidence of broodiness indicated a highly significant (P<.001) positive correlation between these traits (r = +0.446). Approximately 19.9% of the total variance in the egg production of this group was accounted for by the regression on hematocrit. A higher incidence of broodiness did not alter the results of regression analysis: the correlation coefficient of the high-broodiness group was +0.452, accounting for 20.5% of the total variance in egg production. It should be emphasized that the positive correlation is between egg production and the inverse of the hematocrit; the correlated response of the traits involved is negative, meaning that as egg production rises, the hematorcrit values fall. Hematocrit values ranging from 32% to 56% were observed in this experiment. By solving the regression equations for hematocrit values within this range, a table of predicted weekly TABLE 2. Expected egg production for various hematocrit values in flocks exhibiting a relatively high or low incidence of broodiness Expected % egg production Hematocrit
% 32 35 40 45 50 56
High broodiness 71.4 67.1 35.7 20.0 7.1 0
Low
broodiness 80.0 77.1 47.1 32.8 21.4 10
Downloaded from http://ps.oxfordjournals.org/ at University of Queensland on April 29, 2015
a high incidence of broodiness in one pen while minimizing the incidence of broodiness in the other pen. In the high-broodiness pen, hens were released from the trap nests every four hours, the nests were left open during the night, and at least one "nest egg" (an empty egg shell filled with wax) was left in each nest at all times. In the low-broodiness pens, hens were released from the nests every two hours, the nests were closed at night, and no eggs were left in the nests between collections. Broody birds were left untreated in both pens. Commencing six weeks after the onset of egg production (coinciding with the appearance of broodiness in the high-broodiness pen), the hematocrit of each bird was determined weekly using the microhematocrit technique. Blood was obtained from a small needle puncture of the wing vein. All determinations were made in duplicate and the results averaged. Egg production data were summarized for each bird for the period extending from three days before to three days after the day of hematocrit determination. The correlation between the total egg production for this seven day period and the hematocrit was determined for each pen by computerized linear regression analysis. Nine separate transformations of the data were per-
HEMATOCRIT AND PRODUCTION
These results indicate that while hematocrit is significantly correlated with the level of egg production of turkey breeder hens, caution must be exercised in interpreting individual hematocrit readings. A substantial portion of the variation observed among individuals in the number of eggs laid during a relatively short period is not reflected in changes in hematocrit. This is to be expected, since egg production is influenced by many factors which could be assumed to be independent of hematocrit. Similarly, hematocrit is influenced by factors which may have a different correlation (or no correlation at all) with egg production. Olson (1937) observed that the number of erythrocytes in the blood of hens increased
significantly during cold weather. Huston (1960, 1965) found that the packed cell volume of chickens in controlled temperature environments increased in the colder environmental temperatures. In the present experiment, temperatures within the pens differed little from outside temperatures, which ranged from —27 C. to 31 C. during the course of the experiment. The lower temperatures occurred at the time of highest egg production, while the highest environmental temperatures coincided with declining production. Thus, the influence of environmental temperature on hematocrit was opposing the influence of egg production. It might be expected that turkey breeder hens maintained in a more controlled environment would demonstrate less variability in the response of hematocrit to changes in egg production than was observed in the present experiment. REFERENCES Bell, D. J., 1957. The distribution of glucose between the plasma water and the erythrocyte water in hen's blood. Q. Fl. Exp. Physiol. 42:410-416. Domm, L. V., and E. Taber, 1946. Endocrine factors controlling erythrocyte concentration in the blood of the domestic fowl. Physiol. Zool. 19:258-281. Huston, T. M., 1960. The effects of high environmental temperatures upon blood constituents and thyroid activity of domestic fowl. Poultry Sci. 39:1260. Huston, T. M., 1965. The influence of different environmental temperatures on immature fowl. Poultry Sci. 44:1032-1036. Mashaly, M. M., and B. C. Wentworth, 1974. A profile of progesterone in turkey sera. Poultry Sci. 53:2030-2035. Olson, C, 1937. Variations in the cells and hemoglobin content in the blood of the normal domestic chicken. Cornell Vet. 27:235-263. Taber, E., D. E. Davis and L. V. Domm, 1943. Effect of sex hormones on the erythrocyte number in the blood of the domestic fowl. Amer. J. Physiol. 138:479-487. Vollmer, E. P., and A. S. Gordon, 1941. Effect of sex and gonadotropic hormones upon the blood picture of the rat. Endocrinol. 29:828-837. Wentworth, B. C, 1970. Sterility and reproductive inhibition of Japanese quail induced by mestranol ingestion. Poultry Sci. 49:1477-1484. Winter, A. R., 1935. Influence of egg production on hemoglobin content of chicken blood. Poultry Sci. 14:316.
Downloaded from http://ps.oxfordjournals.org/ at University of Queensland on April 29, 2015
egg production values (converted to percent production) may be obtained for hens exhibiting either a relatively high or relatively low incidence of broodiness (Table 2). This table would indicate, for instance, that in a normal flock of turkeys (relatively low incidence of broodiness), a hen exhibiting a hematocrit of 45% or greater may be expected to be laying at a rate of production of 33% or less during the week in which the hematocrit is taken. Examination of individual production and hematocrit records indicated that of the 77 cases in which hematocrits in this range were observed, the assumption of weekly egg production less than 33% was correct 75% of the time. However, the converse was not true—of the 152 instances in which individual weekly percent production was below 33%, the hematocrit measurement reflected this low production in only 38% of the cases. Thus, it would appear that a high hematocrit is a fairly accurate reflection of poor egg production. In 95% of the instances observed, extremely high hematocrit values (48% or above) indicated that the hen had not laid at all during the seven day period surrounding the hematocrit measurement. However, it was possible to have poor egg production within this weekly period without a correspondingly high hematocrit reading. Further, a low hematocrit (35% or less) was a relatively poor indicator of superior egg production.
809
Poultry Science 56:807-809, 1977
INTRODUCTION The decline in egg p r o d u c t i o n which characteristically occurs in a flock of t u r k e y breeder hens as t h e breeding season advances represents a major e c o n o m i c loss t o t h e t u r k e y breeder. Any a t t e m p t t o t e m p e r this loss t h r o u g h removal or t r e a t m e n t of u n p r o d u c t i v e hens, or to s t u d y t h e physiological events associated with cessation of egg p r o d u c t i o n , requires early identification of hens t h a t are going o u t of production b u t have n o t y e t exhibited either b r o o d y behavior or inability t o evert t h e oviduct for insemiantion. Although a n u m b e r of physiological parameters might be postulated t o reflect, and perhaps predict, t h e changing reproductive status of t h e breeder hen, only a m e t h o d which is simple, rapid a n d inexpensive will have practical value in screening large flocks of breeder hens u n d e r commercial conditions. D o m m and Taber ( 1 9 4 6 ) have observed t h a t , in t h e chicken, t h e period of highest egg p r o d u c t i o n coincides with t h e lowest red blood cell c o u n t . Bell ( 1 9 5 7 ) r e p o r t e d t h a t laying hens have a lower packed cell v o l u m e t h a n d o non-laying h e n s . Winter ( 1 9 3 5 ) f o u n d lower levels of h e m o g l o b i n in t h e blood of laying hens
Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison.
than in non-laying hens. These differences are presumably a reflection of t h e different horm o n a l states of laying and non-laying birds. Estrogen administration is k n o w n t o result in a decline in t h e h e m a t o c r i t of m a n y species, including chickens (Taber et al., 1 9 4 3 ; D o m m and Taber, 1 9 4 6 ) , quail ( W e n t w o r t h , 1 9 7 0 ) and rats (Vollmer and G o r d o n , 1 9 4 1 ) . Similar changes occur when e n d o g e n o u s estrogen secretion is stimulated by administration of g o n a d o tropins (Vollmer and G o r d o n , 1 9 4 1 ) . T h e p u r p o s e of t h e present w o r k was t o d e t e r m i n e t h e regression of egg p r o d u c t i o n associated with h e m a t o c r i t in t u r k e y breeder hens and t o assess t h e value of this determination in t h e identification of u n p r o d u c t i v e birds. MATERIALS AND METHODS Eighty spring-hatched Large White t u r k e y hens were reared as previously described (Mashaly and W e n t w o r t h , 1974). The birds were divided i n t o t w o pens of 4 0 birds each and received 1 4 hours of light per day during t h e reproductive season (January t h r o u g h May). Birds were housed in an uninsulated, pole-type structure such t h a t pen t e m p e r a t u r e s differed little from natural conditions. T r a p nesting was used t o d e t e r m i n e t h e daily egg p r o d u c t i o n for individual hens. T h e egg collection procedures e m p l o y e d t h r o u g h o u t t h e reproductive season were designed t o encourage
807
Downloaded from http://ps.oxfordjournals.org/ at University of Queensland on April 29, 2015
ABSTRACT Weekly hematocrit measurements were correlated with weekly egg production throughout the breeding season of Large White turkey hens. A highly significant negative regression of egg production associated with hematocrit was observed, occurring without regard to differences in the incidence of broodiness in the flocks under study. Approximately 20% of the total variance in egg production was accounted for by the regression on hematocrit. A high hematocrit (>45%) was a fairly accurate indicator of poor production; however, not all hens which laid poorly (<33% production) during a weekly period exhibited a high hematocrit. Virtually all hens having a hematocrit of 48% or greater were totally out of production during the weekly period surrounding the hematocrit measurement. The hematocrit may be a useful method for rapid identification of a significant proportion of the unproductive hens in a turkey breeder flock. Elimination of environmental temperature extremes may enhance the usefulness of this technique.
808
PROUDMAN AND WENTWORTH
TABLE l.—Mean weekly percent egg production for groups of Large White turkey hens exhibiting a high or a low incidence of broodiness
Production week
broodiness group
High broodiness group
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
49.3 61.8 61.8 60.8 62.3 59.7 48.0 48.7 54.6 51.6 44.7 45.9 48.0 42.2 48.1 45.5 43.6 42.5 42.1 38.6
45.4 61.5 56.8 56.0 48.7 41.0 37.4 31.1 36.6 43.8 37.8 31.7 30.5 31.3 32.4 30.1 26.3 22.4 23.2 23.0
Low
formed prior to regression analysis, including transformation of each variable to its log, square root and inverse, and transformation of both variables to logs and square roots. These preliminary calculations showed that the greatest proportion of the total variance in the data could be accounted for by the regression of egg production on the inverse of the hematocrit. RESULTS AND DISCUSSION
The weekly mean percent egg production for each pen throughout the reproductive season is presented in Table 1. It is apparent that the management practices employed in egg collection exerted a marked effect upon the incidence of broodiness, as reflected in percent egg production. Regression analysis of egg production on the inverse of hematocrit for hens showing the lower incidence of broodiness indicated a highly significant (P<.001) positive correlation between these traits (r = +0.446). Approximately 19.9% of the total variance in the egg production of this group was accounted for by the regression on hematocrit. A higher incidence of broodiness did not alter the results of regression analysis: the correlation coefficient of the high-broodiness group was +0.452, accounting for 20.5% of the total variance in egg production. It should be emphasized that the positive correlation is between egg production and the inverse of the hematocrit; the correlated response of the traits involved is negative, meaning that as egg production rises, the hematorcrit values fall. Hematocrit values ranging from 32% to 56% were observed in this experiment. By solving the regression equations for hematocrit values within this range, a table of predicted weekly TABLE 2. Expected egg production for various hematocrit values in flocks exhibiting a relatively high or low incidence of broodiness Expected % egg production Hematocrit
% 32 35 40 45 50 56
High broodiness 71.4 67.1 35.7 20.0 7.1 0
Low
broodiness 80.0 77.1 47.1 32.8 21.4 10
Downloaded from http://ps.oxfordjournals.org/ at University of Queensland on April 29, 2015
a high incidence of broodiness in one pen while minimizing the incidence of broodiness in the other pen. In the high-broodiness pen, hens were released from the trap nests every four hours, the nests were left open during the night, and at least one "nest egg" (an empty egg shell filled with wax) was left in each nest at all times. In the low-broodiness pens, hens were released from the nests every two hours, the nests were closed at night, and no eggs were left in the nests between collections. Broody birds were left untreated in both pens. Commencing six weeks after the onset of egg production (coinciding with the appearance of broodiness in the high-broodiness pen), the hematocrit of each bird was determined weekly using the microhematocrit technique. Blood was obtained from a small needle puncture of the wing vein. All determinations were made in duplicate and the results averaged. Egg production data were summarized for each bird for the period extending from three days before to three days after the day of hematocrit determination. The correlation between the total egg production for this seven day period and the hematocrit was determined for each pen by computerized linear regression analysis. Nine separate transformations of the data were per-
HEMATOCRIT AND PRODUCTION
These results indicate that while hematocrit is significantly correlated with the level of egg production of turkey breeder hens, caution must be exercised in interpreting individual hematocrit readings. A substantial portion of the variation observed among individuals in the number of eggs laid during a relatively short period is not reflected in changes in hematocrit. This is to be expected, since egg production is influenced by many factors which could be assumed to be independent of hematocrit. Similarly, hematocrit is influenced by factors which may have a different correlation (or no correlation at all) with egg production. Olson (1937) observed that the number of erythrocytes in the blood of hens increased
significantly during cold weather. Huston (1960, 1965) found that the packed cell volume of chickens in controlled temperature environments increased in the colder environmental temperatures. In the present experiment, temperatures within the pens differed little from outside temperatures, which ranged from —27 C. to 31 C. during the course of the experiment. The lower temperatures occurred at the time of highest egg production, while the highest environmental temperatures coincided with declining production. Thus, the influence of environmental temperature on hematocrit was opposing the influence of egg production. It might be expected that turkey breeder hens maintained in a more controlled environment would demonstrate less variability in the response of hematocrit to changes in egg production than was observed in the present experiment. REFERENCES Bell, D. J., 1957. The distribution of glucose between the plasma water and the erythrocyte water in hen's blood. Q. Fl. Exp. Physiol. 42:410-416. Domm, L. V., and E. Taber, 1946. Endocrine factors controlling erythrocyte concentration in the blood of the domestic fowl. Physiol. Zool. 19:258-281. Huston, T. M., 1960. The effects of high environmental temperatures upon blood constituents and thyroid activity of domestic fowl. Poultry Sci. 39:1260. Huston, T. M., 1965. The influence of different environmental temperatures on immature fowl. Poultry Sci. 44:1032-1036. Mashaly, M. M., and B. C. Wentworth, 1974. A profile of progesterone in turkey sera. Poultry Sci. 53:2030-2035. Olson, C, 1937. Variations in the cells and hemoglobin content in the blood of the normal domestic chicken. Cornell Vet. 27:235-263. Taber, E., D. E. Davis and L. V. Domm, 1943. Effect of sex hormones on the erythrocyte number in the blood of the domestic fowl. Amer. J. Physiol. 138:479-487. Vollmer, E. P., and A. S. Gordon, 1941. Effect of sex and gonadotropic hormones upon the blood picture of the rat. Endocrinol. 29:828-837. Wentworth, B. C, 1970. Sterility and reproductive inhibition of Japanese quail induced by mestranol ingestion. Poultry Sci. 49:1477-1484. Winter, A. R., 1935. Influence of egg production on hemoglobin content of chicken blood. Poultry Sci. 14:316.
Downloaded from http://ps.oxfordjournals.org/ at University of Queensland on April 29, 2015
egg production values (converted to percent production) may be obtained for hens exhibiting either a relatively high or relatively low incidence of broodiness (Table 2). This table would indicate, for instance, that in a normal flock of turkeys (relatively low incidence of broodiness), a hen exhibiting a hematocrit of 45% or greater may be expected to be laying at a rate of production of 33% or less during the week in which the hematocrit is taken. Examination of individual production and hematocrit records indicated that of the 77 cases in which hematocrits in this range were observed, the assumption of weekly egg production less than 33% was correct 75% of the time. However, the converse was not true—of the 152 instances in which individual weekly percent production was below 33%, the hematocrit measurement reflected this low production in only 38% of the cases. Thus, it would appear that a high hematocrit is a fairly accurate reflection of poor egg production. In 95% of the instances observed, extremely high hematocrit values (48% or above) indicated that the hen had not laid at all during the seven day period surrounding the hematocrit measurement. However, it was possible to have poor egg production within this weekly period without a correspondingly high hematocrit reading. Further, a low hematocrit (35% or less) was a relatively poor indicator of superior egg production.
809