Erratic Oviposition and Egg Defects in Broiler-type Pullets

417

T E M P E R A T U R E AND ASCORBIC A C I D

effect of environmental conditions on body temperature of fowls. British Poultry Sci. 5: 235-244. Lee, D. H. K., K. W. Robinson, N. T. M. Yeates and M. I. R. Scott, 194S. Poultry husbandry in hot climates, experimental enquiries. Poultry Sci. 24: 195-207. Perek, M., and J. Kendler, 1962. Vitamin C supplementation to hens' diets in hot climate. Poultry Sci. 41: 677-678. Roy, R. N., and B. C. Guha, 1958. Species differences in regard to the biosynthesis of ascorbic acid. Nature, 182: 319-320. Scrimshaw, N . S., R. L. Goodland and F. B. Hutt, 1949. Variations in the ascorbic acid blood levels of hens. Poultry Sci. 28: 45-51. Sealock, R. R., and R. L. Goodland, 1951. Ascorbic acid, a coenzyme in tyrosine oxidation. Science, 114: 645-646. Sealock, R. R., and H. E. Silberstein, 1940. The excretion of homogentisic and other tyrosine metabolites by the vitamin C deficient guinea pig. J. Biol. Chem. 135: 251-258. Snedecor, G. W., 1956. Statistical Methods. 5th Ed. Iowa State University Press, Ames, Iowa. Thornton, P. A., 1961. Increased environmental

temperature influences on ascorbic acid activity in the domestic fowl. Fed. Proc. 20: 210A. Thornton, P. A., 1962. The effect of environmental temperature on body temperature and oxygen uptake by the chicken. Poultry Sci. 4 1 : 10531060. Thornton, P. A., and S. S. Deeb, 1961. The influence of thyroid regulators on blood ascorbic acid levels in the chicken. Poultry Sci. 40: 1063-1067. Thornton, P. A., and R. E. Moreng, 1958. The effect of ascorbic acid on egg quality factors. Poultry Sci. 37:691-698. Thornton, P. A., and R. E. Moreng, 1959. Further evidence on the value of ascorbic acid for maintenance of shell quality in warm environmental temperature. Poultry Sci. 38: 594-599. Warren, D. C , and R. L. Schnepel, 1940. The effects of air temperature on egg shell thickness in the fowl. Poultry Sci. 19: 67-72. Wilhelm, L. A., 1940. Some factors affecting variations in egg shell quality. Poultry Sci. 19: 246253. Yeates, N. T. M., D. H. K. Lee and H. J. O. Hincs, 1941. Reactions of domestic fowls to hot atmospheres. Proc. Roy. Soc. Queensland, 53: 105128.

Erratic Oviposition and Egg Defects in Broiler-type Pullets R. G E O R G E J A A P AND F O R E S T V. M U I R

Ohio Agricultural Research and Development Center, Columbus, Ohio 43210 (Received for publication June 19, 1967)

T

H E females which produce

chicks

for broiler production h a v e changed

changes

in

appearance

and

behavioral

activity. E x t e r n a l and behavioral differ-

greatly during the past 15 to 20 years.

ences are more readily observable

Broiler chickens were twice as large a t 8

those which are internal and physiological

weeks of age in 1965 as those of the same

than

T h e following report records observa-

age in 1952 (Maine Broiler T e s t Reports,

tions

1952-1965). T h e mothers of broiler chicks

p a t t e r n s and t h e high incidence of egg

now reach an adult b o d y weight of 3 1/2

defects

to 4 kilograms. D u r i n g this s a m e period

strains. Irregularities of oviposition time

concerning in

these

non-rhythmic large-bodied

laying broiler

(1950-1965), egg-type females have been

and the accompanying defects appear to

reduced from a b o u t 2.2 kilograms adult

be much more frequent t h a n those pre-

body weight to approximately 1.9 kilo-

viously reported. A recent s u m m a r y con-

grams. This d r a m a t i c difference in body

cerning the n o r m a l p a t t e r n s of egg pro-

size between broiler- and egg-type females

duction m a y be found in Sturkie's book

has been accompanied

(1965).

by many

other

418

R.

G. J A A P AND F . V.

MATERIALS AND METHODS T h e broiler-type pullets were nonselected samples from seven populations of synthetic origin used in growth selection experiments. These strains were identified (Jaap, 1963) by the symbols A, G, AG, AG1, RG, GRL and WG2. AGl and WG2 were randombred control populations maintained by restricted random breeding. T h e other five populations were reproduced each generation from 20 to 2 5 % of the population having the greatest body weight a t eight weeks of age. Two egg-type populations have been sampled for comparisons. These were synthetic populations originating from pooling the inheritance of the N . C . Regional Leghorn and a strain selected for large weight of the bursa of Fabricus a t hatching. These egg-type populations have been designated BLC and BLS by Muir and J a a p (1967). No feed restriction was practiced dur-

MUIR

i n g the brooding, rearing or laying periods Artificial light has been used to maintain a 14-hour daylength during the laying period. Each observation group of pullets was housed in individual 3 0 X 4 6 cm. laying cages at the commencement of lay between 18 and 24 weeks of age. ERRATIC SEQUENCE OF EGG LAYING Figure 1 reproduces the daily egg sequences of the first twelve pullets starting to lay in a non-selected sample of 400 broiler-type pullets from strains A, G, AG, and AGl. They were placed in the laying cages at 118 days of age. T h e records in Fig. 1 were those collected during the first 75 days after the first pullet started to lay of J a n u a r y 10, 1965. The first twelve pullets starting to lay were selected for illustration in order to provide, as nearly as possible, an unbiased sample.

FIG. 1. Daily egg laying patterns for 12 broiler-type pullets from the beginning of lay, January 10, through March 25, 1965. Pullet identification number

Egg laying pattern

l»33

1 0 1 0 1 0 S 1 1 1 1 S 0 0 1 1 0 0 0 0 0 0 S 0 0 0 1 1 S 0 1 M 1 0 1 0 0 1 D 1 1 1 S 0 1 1 0 1 1 0 0 1 1 0 0 1 1 0 1 1 0 1 1 1 1 0 1 1 0 1 1 1 1 0 0

5143

1 0 1 1 0 1 0 0 0 1 0 0 0 0 2 0 1 1 1 1 0 0 1 0 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 1 0 1 0 2 1 1 0 0 0 0

239

1100S11101111S00011100DOS0110D0111110S1111100001110010MOOD0011D101MDOD1110

M

2U 3ltl

100101101011100111010011100010011001100200001001101001200111

1,0 1 0 0 1 1 0 0 1 1 0 0

1000000010110110010111011101110111011110110001101100100001001001001011101

220

11011110101011010111011101H1101011

518

11000101000000000010000110100M000011011001101110111110001

1000100100100110110100111011000001110 0 1101000010001

21

110010101000010100110000001011100010001001001100100M1011100011011101010

86

10000000001110001110110101001000000101010001002101001111100100110111100

104

101001010101100110110H011000100110110011000001110000100000011111100001 S M 111S1O1O110O0111O1101101111011101O11O1111011D00O2011OO02OD10201M01O1O1 H S 11O1OOO011101ODOO11011OM00001O11HOOO2OO111OH01OOMS011102O1S10O111OO11

110 203

i=normal egg, M=shell-less egg, 5 = soft -shelled egg, Z)=double-yolked egg, and 2 = two normal eggs laid the same day.

419

OVIPOSITION AND EGG DEFECTS

The following codes are used in Fig. 1 and throughout this report: 1. The number 1 indicates an egg gathered and " 0 " no egg laid during each consecutive day. 2. The number 2 indicates that two eggs of normal appearance were collected on that specific day. 3. The symbol M is used for a membrane egg, lacking visible shell deposition. 4. The letter S is used for a soft-shelled egg obviously deficient in amount of shell, being cracked or readily broken at gathering. 5. Double-yolked eggs, D, were identified by size only. Periodic checks by candling indicated that all D eggs were double-yolked. When pedigreed eggs were sorted according to hen, it appears that approximately one egg in fifty classified as normal actually contained two yolks, the egg not being large enough to be readily identified. None of the pullets (Fig. 1) exhibited what might be designated as a normal sequence or rhythm of days on which an egg was laid or missed. Days of laying were scattered haphazardly during the observation period for each pullet. Complete records for this 75-day period were available for 378 pullets. Ovipositions appeared to be equally arhythmic for those starting to lay at older ages. In Fig. 1, the letter M or S above the number 1 indicates oviposition of a normal and an abnormal egg during the same day. When two ovipositions occur within 24 hours they may consist of one egg obviously deficient in shell or two eggs which appear normal. Some of the dual ovipositions appear to have resulted from two ovulations occurring in less than 24 hours. Two ovipositions recorded on the same day were observed more frequently in broiler-type than in egg-type pullets. During 1965, broiler strains AG1, WG2,

TABLE 1.—Frequency of defective eggs and two ovipositions during the same day for broiler-type pullets A, G, AG and AG1 between 118 and 193 days of age

Strain

No. of hens

A G AG AG1

93 93 98 94

Average Defective ovipositions as no. of percentage of total yolks yolks ovulated per pullet S M D 2's 24.3 26.5 27.9 23.4

3.2 5.9 2.8 2.6

3.1 5.9 3.6 3.4

6.4 5.0 6.2 7.5

3.5 3.8 2.5 5.1

RG and GRL were reared and housed about the same time as egg-type pullets from BLS and BLC strains. Feeding and management was similar. Of the eggs laid prior to the 28th week of age, 3.7% of the eggs from the broiler types and 0.5% of 'the eggs from the egg-types were double ovipositions within a 24-hour period. FREQUENCY OF DEFECTIVE EGGS

Data on the frequency of S, M, D and 2 egg daily gatherings between 118 and 193 days of age for broiler-types A, G, AG and AG1 during the early spring of 1965 are summarized in Table 1. The average number of yolks ovulated per hen per strain during this period ranged from 23.4 to 27.9. Eggs lacking shell (M) or shell so defective they could not be gathered (S) varied from 6.3% in strain A to 11.8% in strain G. Double-yolked eggs (D) accounted for a minimum of 5.0% of the strain G yolks to 7.5% of the yolks ovulated by AG1 pullets during this period. Yolks laid as two normal appearing eggs (2) ranged from 2.5% in strain AG to 5.1% in strain AG1. Data will be presented later which indicates that many of these eggs, although normal in appearance, were defective in shell formation. The percentages of hens from which no defective eggs were observed during a six-month period were 16, 10, 15 and 18 for strains A, G, AG and AG1, respectively

420

R. G. JAAP AND E. V. M U I R

TABLE 2.—Egg production summaries during a 12week period (Dec. 7 through Feb. 24, 1967) beginning at 21 weeks of age Strains AG1 ercent peak of yolk production o. of ovulations sampled > of sample: M

sD M+S+D ouble ovipositions

WG2

RG

GRL

65.7

74.6

69.5

75.4

2,018

2,506

843

2,282

2.3 2.3 5.6

1.7 2.0 5.0

2.6 2.7 9.3

3.8 3.2 12.5

10.2

8.7

14.6

19.5

6.4

4.8

1.6

4.6

Therefore, 82 to 90% of the pullets laid some defective eggs. It is possible that cage management might be conducive to a higher frequency of defective eggs than floor or litter management of broiler-type pullets. However, all of the S and M eggs would be readily broken on the floor, or in the nests, under floor management. Recent observations of Wood-Gush (1963) indicate that a hen which lays a M egg lacks the normal nesting behavior, laying these eggs on the floor where they would be quickly eaten by other members of the flock. The S-eggs were so deficient in shell that most of them would have been broken if laid in a nest. Therefore, it is probable that most of the M and S eggs are broken and eaten by the hens and not observed under floor layer management. Additional data have been obtained by 3 day per week recording of eggs laid by 393 broiler-type pullets from strains AG1, WG2, RG and GRL during a 12-week period from December 7, 1966, through February 24, 1967. These pullets were 21 weeks of age at the beginning of the recording period. Data on their performance are summarized in Table 2. The peak production of yolks during a 3-day recording period ranged from 65.7% for AG1 to 75.4% for GRL. The percentage of M and S eggs laid by the

randombred control strain AG1 was 4.6% for this 12-week period versus 6.0% for the 75-day sample from the same strain collected the previous year (Table 1). In Table 2, strain WG2 produced the fewest M and S eggs (3.7%) while GRL produced the highest percentage (7.0%). The percentage of yolks laid as double-yolked eggs ranged from 5.0% in strain WG2 to 12.5% in strain GRL. The estimated loss of yolks in eggs unsuitable for hatching (M, S and D) ranged from 8.7% in WG2 to 19.5% in strain GRL. In Table 2, the frequency of yolks recorded as two ovipositions during the same day was least in strain RG accounting for 1.6% of the yolks, and greatest with 6.4% of the yolks in strain AG 1. The term "double ovipositions" in Table 2 included all cases where the two yolks were in separate membranes whether M, S or apparently normal eggs. SHELL QUALITY OF DOUBLE OVIPOSITIONS

Although they appear normal, many of the eggs collected as pairs from the same hen in one day were defective in shell formation. Some of these were observed to have a rough sandpaper-like shell to the touch. During the spring of 1965, pairs of eggs laid during the same day were collected from A, G, AG and AG1 pullets whose egg defects early in the laying period were summarized in Table 1. All eggs laid by each hen which had produced one of the 72 pairs of eggs TABLE 3.—14-day evaporation weight loss of eggs laid as pairs during the same day compared with a random sample of eggs

Total no. of eggs Percent rough shell Percent weight loss: All eggs Rough eggs Smooth eggs

Pairs

Controls

144 26.7%

518 5.4%

9.11 4.96 10.47

7.47 4.91 7.61

421

OVIPOSITION AND EGG DEFECTS

were collected during the week following the collection of a pair of eggs in one day. This provided a control sample of 518 eggs from hens which had previously laid two eggs in one day. Observations from these pairs and control eggs are summarized in Table 3. Rough-shelled eggs were observed to be about five times as frequent (26.7% versus 5.4%) among those eggs gathered as pairs on the same day. All eggs were weighed and placed in an incubator for 14 days after which their weight loss was measured. T h e eggs laid as pairs lost 9 . 1 1 % of their weight versus 7.47% for the control sample from the same hens. T h e incubation weight loss of the eggs with rough surfaces was below t h a t of the controls and about the same amount whether gathered as pairs or as single controls. Weight loss for eggs with the normal (smooth) shell texture was greater for those members of pairs (10.47%) than for the controls (7.61%). T h e more deficient shelled eggs among the pairs could have resulted from one or both eggs leaving the shell gland prematurely. T h e reason for the low incubation weight loss for those eggs classified as having a rough texture to the touch has not been explored at this time. PERSISTENCE OF EGG DEFECTS

Most of our observations have been made during the first three months of lay when defective ovipositions are most frequent in the broiler-type female. Comparable d a t a were available for egg production of pullets between the 23rd and 52nd week of age for 700 egg-type and 400 broiler-type pullets during 1965. During this period the .S and M eggs were not separately identified. These d a t a summarized in Table 4 include all eggs from 3-day records each week. T h e y are summarized in three-week intervals because the egg-type (BLS and BLC) pullets

TABLE 4.—Percent of defective eggs and 2-eggs-per-day among egg- and broiler-type pullets during the first six months of lay Percentage of yolks laid as: Weeks

23-25 26-28 29-31 32-34 35-37 38-40 41-4.3 44-46 47-49 50-52

S&M

D

2 per day

Egg

Broiler

Egg

Broiler

Egg

Broiler

1.9 1.1 0.7 0.7 0.9 0.7 0.9 1.0 1.1 1.3

5.7 5.9 3.3 3.9 3.2 2.8 1.8 1.5 3.2 4.6

3.4 2.5 1.0 0.3 0.2 0.1 0.2 0.1 0 0.2

4.9 8.1 4.3 2.9 1.7 1.8 0.9 0.2 0.4 0

1.4 1.3 2.0 1.2 0.7 2.0 1.6 1.3 0.1 2.0

6.2 3.6 3.6 2.6 3.2 2.7 1.7 0.8 2.6 3.0

were composed of two hatches differing in age by three weeks. T h e percentage of yolks laid as 5 and M defects (Table 4) tended to decrease slightly with increasing age until the 47-49 week period when S and M defects showed evidence of increasing. T h e latter p a r t of the observation period was in late July and August. An increase in M and 5 at this time may have been attributable to stress of summer temperatures. In the egg-type pullets M and S eggs accounted for 0.7 to 1.9% of the yolks in any threeweek period versus 1.5 to 5.9% of the yolks from the broiler-type females. T h e frequency of double-yolked eggs rapidly decreased in both types accounting for only 0 . 3 % of the ovulated yolks from eggs types in the 32-34 week period. The broiler-types did not reach this low a frequency of double yolked eggs until about 12 weeks later, during the 44-46 week age period. The frequency of two normal appearing ovipositions per day followed a similar trend to t h a t of the S and M eggs, decreasing until the late July and August periods. This defect of two eggs in one day continued to be more frequent in the broiler-type pullets. DISCUSSION

T h e d a t a presented demonstrate t h a t the lower egg production of these broiler strains appears to differ from low egg production in non-broiler strains b y erratic

422

R. G. J A A P AND F. V.

oviposition timing and the frequency of defective eggs. The resulting disturbance of the rhythmic sequence of daily ovipositions (Fig. 1) does not appear to be a characteristic of non-broiler populations. Regardless of the rate of egg production, most strains of chickens exhibit a more or less rhythmic sequence of laying or nonlaying on successive days (Sturkie, 1965). These observations pose the question: Has the rapid change in growth rate in broiler populations affected the precision of ovulation timing in these strains? The arhythmic ovipositions of the broiler-type female have been accompanied b y a great increase in improperly formed eggs. Selection for rapidity of growth rate in broiler strains may have favored birds which were less responsive to circadian rhythms of light and dark, activity and inactivity, etc. This lack of sensitivity to daily rhythmic changes in the environment could affect ovulation timing, shell formation and the time of oviposition. Should this theory be correct, the broiler which is least affected b y the circadian r h y t h m of its environment is most apt to grow most rapidly. Low sensitivity to environmental rhythms of circadian nature could have produced the m a n y idiosyncrasies of oviposition recorded in this report. Our first assumption was t h a t ovulation timing might have been responsible for all of the abnormalities described. Curtis (1914) and Conrad and Warren (1940) have demonstrated t h a t the majority of double-yolked eggs result from ovulations occurring simultaneously or at least less t h a n one half hour apart. Should a second ovulation occur two or more hours later than the previous one, this second yolk might follow the first through the oviduct. Since the period of shell formation in the uterus is approximately 20 hours, it would be logical to expect t h a t

MUIR

the second yolk in the isthmus might cause premature expulsion of the first egg from the uterus. This could explain the occurrence of some of the membrane, M', eggs as well as those deficient in shell formation. In this case, M and 5 eggs should be followed by a normal egg on the following day. A count of the sample laying patterns in Fig. 1 shows 19 of the M and S eggs were followed by another egg laid during the next day. However, 11 of the M or S eggs did not precede a day in which a normal egg was laid. Therefore, it is doubtful t h a t erratic ovulation is the only source of these defective eggs. Scott (1940) described a condition where a flattened surface was observed as a result of a shell egg being retained for an abnormally long period due to disturbances of hens at oviposition time. Also, a flattened area on the membrane egg was described b y Scott and attributed to interference between the shelledegg in the uterus and the following egg in the isthmus. In our broiler strains, the appearance of an egg with a flattened thin-shell area was very rare. No evidence of abnormality of the M eggs was observed, although only a small percentage of these have been plumped in water to carefully examine their shape. The time of oviposition of 20 pairs of eggs has been observed b y recording eggs each hour between 9 a.m. and 4 p.m. Although one or both of the members of each pair m a y have been deficient in shell, they appeared to be normal in shape and not sufficiently deficient to be given the 5 classification. I n all of these 20 pairs, the second egg was recorded within seven hours after the first egg was recorded. In two cases, the pair of eggs were observed at the same hour; 10 a.m. for one pair and 4 p.m. for the other pair. I t is highly improbable t h a t two eggs could have been in the shell gland a t the same

423

OVIPOSITION AND EGG DEJECTS

time and certainly abnormal shell and membrane formation would be expected even when one egg was in the isthmus and one in the uterus (Scott, 1940). Recently, Dr. Glyde Marsh, while performing a postmortem examination on some pullets from another experiment, observed a membrane egg in the uterus and a normal egg in the vagina of the same hen. Apparently this is the first time this phenomenon has been observed. Therefore, it may be possible for a hen to retain a completed egg in the vagina while another is in the uterus for shell formation. The present information regarding idiosyncracies of oviposition and egg formation in these broiler pullets have not provided explanation of the causal factors. Erratic ovulation timing appears to be involved in the syndrome. Whether the time of ovulation of successive yolks is the major causal factor remains a question which will be difficult to answer. Since all seven of the broiler-type populations from widely varying origins exhibit these idiosyncracies of ovipositions, the reduction in egg production which has accompanied gain in growth rate appears to be considerably different from the equally low egg production patterns of unimproved strains. A knowledge of the physical as well as physiological bases for these defective ovipositions should aid in solving the problem of declining egg production in broiler-type strains. SUMMARY

Broiler-type pullets from seven different populations have been observed to exhibit arhythmic sequences in their daily egg laying patterns. During the first three months of lay 9 to 20% of their

ovulations resulted in defective eggs: 3.7 to 7.0% were soft-shelled or shell-less, 5.0 to 12.5% were laid as double-yolked eggs, and 1.6 to 6.4% were observed as two ovipositions per hen within 24 hour periods. During the first six months of lay, yolks laid as shell-less or soft-shelled eggs varied from 1.5 to 5.9% from broilerversus 0.7 to 1.9% from egg-type pullets which were reared and housed under similar conditions. Two eggs laid during the same day accounted for 0.8 to 6.2% of yolks from broiler- versus 0.1 to 2.0% from egg-type pullets. Double-yolked eggs were twice as frequent and the frequency of yolks laid as double-yolked eggs did not drop to 1% until the 21st week of lay in broiler- versus the 9th week for egg-type pullets. REFERENCES Maine Broiler Test Reports 1952-1965. Division of Animal Industry, Maine State Dept. Agric, Augusta, Maine. Curtis, M. R., 1914. Studies on the physiology of reproduction in the domestic fowl. XVI. Double eggs. Biol. Bull. 31:181-213. Conrad, R. M., and D. C. Warren, 1940. The production of double-yolked eggs in the fowl. Poultry Sci. 19: 9-17. Jaap, R. G., 1963. Selection for rapid growth rate in chickens. Poultry Sci. 42: 1393-1397. Muir, F. V., and R. G. Jaap, 1967. A negative genetic correlation between bursa weight at hatching and post-hatching body growth of chickens. Poultry Sci. 46: 1483-1488. Scott, H. M., 1940. A note on abnormal shape of eggs. Amer. Nat. 74: 185-188. Sturkie, P. D., 1965. Avian Physiology, 2nd edit., Comstock. Cornell University Press, Ithaca, New York. Wood-Gush, D. G. M., 1963. Control of the nesting behaviour of the domestic hen. 1. The role of the oviduct. Animal Behavior, 11: 293-299.

OCTOBER 8-10. NEPPCO POULTRY SHOW AND EXPOSITION, FARM SHOW BUILDING, HARRISBURG, PENNSYLVANIA