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Influence of Avian Pneumoencephalitis on Subsequent Egg Quality
Influence of Avian Pneumoencephalitis on Subsequent Egg Quality F. W. LORENZ AND W. E. NEWLON Divisions of Poultry Husbandry and Agricultural Extension, Davis and Berkeley, University of California (Received for publication October 30, 1943)
F
* Dr. J. R. Beach, Division of Veterinary Science, University of California, made the diagnoses.
and eggs were candled. Three types of egg abnormality were observed in varying' numbers; these were (1) air bubbles (as described above) including a few eggs with bubbles in addition to an air cell, (2) poor shells, (3) apparently weak albumens (as estimated by candling). Eggs were obtained from birds that had first shown symptoms of the disease from 7 to 36 days previously. The incidence of air bubbles varied from 0 to 10 percent of individual groups of birds, and, altogether, about 4 percent of all of the approximately 4,000 eggs examined on the 3 ranches were bubbly. The average shell quality of the eggs examined on these 3 ranches was considerably worse than is usual for pullet flocks, and a number of eggs were observed with definitely imperfect shells. These included eggs with normal air cells as well as bubbly eggs. There seemed to be only a slight association between the occurrence of bubbles and poor shell quality, for a large number of the bubbly eggs had perfect shells but when more accurate data were obtained an association was found to exist. About 12 percent of the shells of the bubbly eggs were checked or cracked. A certain minimum time after the start of the disease seemed to be necessary for the production of bubbly eggs. T h e few eggs obtained as early as the seventh day after the first observed symptoms were almost free of the bubbly condition; however, over 6 percent of the eggs from the same group of birds 10 days later were
[193]
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
IELD reports have recently called the attention of the authors to an abnormality of fresh-laid eggs that in each instance was stated to have followed an outbreak of avian pneumoencephalitis. Such flocks were reported to produce a moderately large percentage of eggs containing no true air cell but instead an accumulation of small free-floating air bubbles. An exceptionally large number of eggs with poor shells was also reported produced by these flocks. Other reports have been received of flocks producing eggs with unexplainably poor albumen quality. A few of these reports that could be followed up yielded a history of a respiratory disease in the flock. Avian pneumoencephalitis "is characterized by a sudden onset and extremely rapid spread through a flock" (Beach, 1942) and often almost as rapid spread from flock to flock through a region. Adult mortality is usually low but egg production declines sharply and may cease entirely within a week after the first symptoms appear and only gradually returns to normal. In order to investigate the influence of this disease on subsequently produced eggs, two separate studies were made. In the first (or preliminary) study, three ranches were visited (2 twice and 1 three times) where the flocks were known to be recovering from an outbreak of disease diagnosed* as avian pneumoencephalitis,
194
F. W. LORENZ AND W. E. NEWLON
pen the onset of symptoms was sudden and complete. Many of the birds were prostrated and the floor was littered with soft-shelled eggs. Egg production dropped abruptly and by the third day no eggs were produced. All birds remained out of production for at least 7 days (except for 3 that produced one abnormal-shelled egg each during this period); 4 birds returned to lay on the eleventh day, and egg production was back to its former level about a month after the symptoms were first observed. Only 8 of the 100 birds had not returned to production by the end of the observation period. TABLE 1.—Summary of egg types laid by 92 birds after infection with pneumoencephalitis No. eggs
Percent of all eggs
81 83 27
6.26 6.42 2.09
Total abnormal Total normal
137 1157
10.59 89.42
Total eggs
1294
Abnormal shells Bubbly eggs Less duplication
100.0
A total of 1,294 eggs were laid by 92 birds during the observation period after the onset of the disease (Table 1). Of these, 83 or 6.4 percent were bubbly. All of the birds were not equally responsible for the production of this type of egg; in fact, 66, or 80 percent, of all bubbly eggs were produced by just 8 birds, and another 12 birds laid the remaining 17 (Table 2). Thus only 21.7 percent of the flock produced any eggs with this abnormality. No regularity was observed in the production of bubbly eggs by the birds that laid less than 4 such eggs each. These eggs apparently occurred at random anywhere between the first and last egg laid during the observation period after the onset of the disease. Among the birds that laid a
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
bubbly. Between 19 and 29 days after the onset of symptoms, from 2 to 10 percent of the eggs from individual groups had bubbles, and 30 to 39 days after the start of the disease, 0 to 4.6 percent were bubbly. The incidence of bubbles bore no direct relation to the severity of the disease. In fact, the greatest percentage of bubbly eggs were obtained from a group of birds that showed relatively mild symptoms, while the flock that had the severest epidemic with the highest mortality produced only a moderate number of bubbly eggs. The latter flock, however, did produce a larger number of eggs with apparently weak albumen than was observed on the other ranches. The second study was made; when the opportunity- offered, in order to obtain data under somewhat better controlled conditions. Eggs were acquired from a trap-nested breeding flock, as yet uninfected but known to be in immediate danger of infection from its proximity to infected flocks. One hundred pullets from two trap-nest pens were selected for study; several days' egg production was obtained and examined before symptoms of the disease were observed. Unfortunately, due largely to the commercial nature of the establishment, the observations had to be terminated sooner than was desired and material was not available for histological study. However, all eggs produced by these birds up to 45 days after the start of the epidemic were candled. In addition, the eggs produced on two consecutive days each week were broken for albumen height measurement (Wilgus and Van Wagenen, 1936). All such eggs were broken the day they were laid. The course of the disease was typical. Four days elapsed between its inception in the first and second pen, but within each
INFLUENCE OF AVIAN PNEUMOENCEPHALITIS ON SUBSEQUENT EGG QUALITY
195
TABLE 2.—Distribution of abnormal egg production (Birds classified according to type of abnormal eggs laid after infection.) Data on birds that produced eggs No abnormal eggs
Bubbly eggs (no abnormal shells) 1 1
Few bubbly eggs
1 4
2 4
1 6
16.3
11.3
12.5
14.3
13.3
21
16.7
20.2
16.0
12.0
11.0
20
15.3
17.7
14.5
1.8
3.3
2 24
1 17
2 11
20
19.3
12.6
18.3
13
12.9
11.9
17.8
12.1
12.9
11.9
16.4
10.4
1.4
1.7 1
'
1.3
2 2
Many bubbly eggs
2 3
1 20
majority of the bubbly eggs, however, a definite pattern was evident; 6 of the 8 returned to lay reasonably early and produced 2 or 3 eggs with normal air cells before pausing again for 9 to 13 days. They then resumed production, laying bubbly eggs only (or at most one or two with normal air cells toward the end of the observation period). The seventh bird showed a similar pattern except that the first egg laid was bubbly; this was followed immediately by 5 eggs with normal air cells and then by an 11-day pause after which all eggs but one were bubbly. The eighth bird returned to lay late and all eggs produced during the observation period were bubbly. Those birds which laid bubbly eggs returned to production nearly a week earlier, on the average, than did those that produced only normal eggs. The average rate of production was about the same in each group. The production of eggs with abnormal shells followed a pattern different from
Both bubbly eggs and abnormal shells
1.0
0
0.8
0.8
1.0
0.5
5.8
5.3
0.5
1.0
3.8.
1.8
that observed for bubbly eggs. Altogether 81 eggs had some observable shell abnormality. These were produced by 44 birds, and no bird produced more than 4 such eggs. The occurrence of abnormal shells was fairly evenly distributed throughout the observation period. A total of 27 eggs had both abnormal shells and bubbles, as compared with 54 having abnormal shells as the sole defect and 56 having bubbles but normal shells. Thus the twot conditions are at least partially independent. That they are not completely independent, however, is evident from the excess of doubly abnormal eggs over the number expected from chance alone (5.2). If more restricted groups of birds are considered, such an excess is still found, and even if the produce of the 8 birds that laid mostly bubbly eggs is considered alone there is still an excess of two eggs (22 as compared with 20 expected). There is thus some association between the production of the two • types of defect.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
Pen No. of birds Average date resumption of production, October Average number of eggs per bird Average number normal eggs per bird Average number eggs with abnormal shells per bird Average number bubbly eggs per bird Average number eggs with both bubbles and abnormal shells per bird
Abnormal shells (no bubbles)
196
F. W. LORENZ AND W. E. NEWLON TABLE 3.—Average albumen height decrease at various dates after infection Date (October)*
Pen 1
Pen 2
9
8
16
15 8
11 ,
1 No. of eggs Ave. decrease in albumen height, mm. 3.52 P
3 1.22 0.23
1.72 0.005
1.27 0.005
No. of eggs Ave. decrease in albumen height, mm. P
2
7
4
3.85 0.36
2.27 0.013
1.60 0.053
22 14 0.84 0.004 13 1.14 <0.001
23 17 1.13 0.002 16
28 21 1.07 <0.001 18
1.51 1.30 <0.001 " <0.001
29 22 0.98 <0.001 21 1.69 <0.001
* First symptoms of the disease were observed on September 23 in Pen 1 and on September 27 in Pen 2.
existence of a relation between the amount of loss of albumen quality and the production of other egg abnormalities. In order to test the existence of such a reflation, the birds were grouped according to type of egg abnormality produced (Table 4) and the average albumen height losses of the various groups were computed separately. Eggs of birds that produced some bubbly eggs but no abnormal shells had an average albumen height loss of 0.93 mm., those from birds that produced some abnormal shells but no bubbles lost 1.20 mm., while birds that produced neither lost 1.04 mm. None of these averages differ significantly, but eggs from birds that produced both abnormal shells and bubbles lost an average of 2.51 mm., and this value is significantly larger than any of the other averages. All the 8 birds that produced the majority of bubbly eggs were in the latter group, and eggs from these birds lost an average of 2.70 mm., as compared with a loss of 2.40 mm. in eggs from the rest of the birds in that group. These two values are not significantly different, however. Thus there seems to be no relation between the amount of loss of albumen height and the incidence of either shell defects or bubbles, nor any significant relation with intensity of egg defect production. The only relation seems to be in the limitation of those
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
The effect of this disease on albumen height of subsequently laid eggs was estimated by comparing the albumen height of each such egg measured with the average value for the same bird obtained immediately before the onset of the disease. Measurements that could be so compared were obtained on 178 eggs from 64 birds (32 in each pen). The results of the albumen height measurements are recorded in Table 3. If days on which less than 4 eggs were obtained are ignored as not constituting an adequate sample, the drop in albumen height on any day varied from 0.84 to 2.27 mm., and each such drop was statistically highly significant. The magnitudes of the decreases from day to day showed little evidence of a trend during the period studied. With a single exception, the average albumen height of eggs from each of the birds was lower after the disease than before, and the greatest average loss was 4.32 mm. The distribution of average losses was apparently bimodal, with one mode between 0.51 and 0.75 mm. and the other between 2.26 and 2.50 mm. The average losses for those birds that also produced both abnormal shells and bubbly eggs were clustered around the higher mode only; the other groups of birds had representatives around both modes. Such a distribution as this suggests the
INFLUENCE OF AVIAN PNEUMOENCEPHALITIS ON SUBSEQUENT EGG QUALITY
197"
TABLE 4.—Albumen height decrease of birds classified according to other egg abnormalities (Each value is an average of measurements obtained from both pens on all dates on which eggs were broken.) Data on birds that produced eggs No abnormal eggs No. of eggs Ave. decrease in albumen height, mm. P
77 1.04
Bubbly eggs and abnormal shells Abnormal shells 60 1.20
DISCUSSION
The exact cause of the egg changes following an outbreak of pneumoencephalitis remains to be determined. The disease is known to attack different parts of the body, and virus has been isolated from several organs such as the lungs, spleen, and brain (Beach, 1942); thus there is no reason to suppose that it might not also attack the oviduct, with resulting effects on its functioning. Histopathological
11
Few bubbly eggs 19
0.93 2.40 All less than 0.001
Many bubbly eggs 11 2.70
studies would be necessary to establish the point. If the defects are produced by such a mechanism, however, the evidence presented suggests that the isthmus and the uterus may be affected independently of each other. The functioning of the magnum of all or nearly all of the birds seems to have been affected, as judged by the change in albumen height even in eggs of birds that produced no other defect. The extent of the effect on the egg albumen was apparently greater in birds in which the entire oviduct was involved, however. The effect of pneumoencephalitis on albumen quality is especially interesting, for this is the first agent, other than age of bird, that has been demonstrated to modify the albumen height of fresh-laid eggs. The two influences are not to be confused; whereas the change due to bird . age is gradual and progressive and, according to Hunter, Van Wagenen and Hall (1936), operative primarily during the spring and summer, the sequela reported here was sudden and severe, occurred during October and did not progress. The severity of the effect was noteworthy; oh the eggs of a number of the affected birds it was such that the inferior albumen quality would have been noticed readily in the course of ordinary commercial handling.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
birds that produced eggs with all three types of defects to the more severe stage of albumen height loss. Since the possibility was not ruled out that part or all of the loss in albumen quality was directly due to the pause in production rather than to a specific effect of the disease, a test of the effect of pause was obtained from previous quality records of the Poultry Division egg quality breeding flock. The bird records used were those that included measurements on at least 2 eggs before and 2 eggs after a winter pause (8 consecutive days or more out of production during November or December). Records of 12 such birds were chosen at random. The average albumen height of eggs of these birds (on a bird average basis) was 6.81 mm. before and 6.91 mm. after the pause. Thus no loss could be attributed to the pause per se.
Bubbly eggs
198
NEWS AND NOTES SUMMARY
REFERENCES
Beach, J. R., 1942. Avian pneumoencephalitis. Proc. 46th Ann. Meeting U. S. Livestock Sanitary Assn., 203-223. Hunter, J. A., A. Van Wagenen, and G. 0 . Hall, 1936. Seasonal changes in interior egg quality of Singfe-Comb White Leghorn hens. Poultry Sci. 15:115-118. Wilgus, Jr., H. S., and A. Van Wagenen, 1936. The height of the firm albumen as a measure of its condition. Poultry Sci. 15:319-321.
News and Notes E. P. Singsen (B.S. Rhode Island State College '38), (M.S. North Carolina State College '40) has been appointed Assistant Professor of Poultry Husbandry at the University of Connecticut. Mr. Singsen will devote full time to research in poultry nutrition. At the time of his appointment, Mr. Singsen was associated with the University of Illinois as an Assistant in Animal Husbandry working on the doctorate program. G. P. Goodearl a graduate of Connecticut in the class of 1922 and formerly associated with Montana State College, but more recently the North Dakota Agricultural Experiment Station, joined the staff as Assistant Professor, January 1944. Mr. Goodearl will assume the supervisoryship of the Storrs Egg Laying Test, the research work in turkeys and assist with the teaching program.
Dr. Alfred M. Lucas has resigned as Associate Professor of Zoology at Iowa State College to accept a position as Cytopathologist at the U. S. Regional Poultry Research Laboratory, East Lansing, Mich. Dr. Harris D. Webster, veterinarian at the Regional Poultry Research Laboratory, reported for military duty on March 29. Dr. Webster is a first lieutenant in the Veterinary Corps. Capt. James H. Bywaters was promoted to the rank of Major effective March 8. At present he is stationed in Washington, D. C. Capt. George E. Cottral is now serving in the Veterinary Corps somewhere in India. Dr. L. E. Card has called attention to the fact that July 1 is the deadline for entries for either The Poultry Science Research Prize or The Borden Award.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
Eggs laid by chickens up to 45 days after an outbreak of avian pneumoencephalitis were examined. The following observations were made: (1) Up to 10 percent of the eggs produced during this period failed to form normal air cells; air present in the egg was in free-floating bubbles. Most of such eggs were produced by relatively few birds. (2) A considerable number of eggs with abnormal shells were produced. Their production by affected birds was more evenly distributed than the production of bubbly
eggs; abnormal shells were produced by the majority of the flock, yet no bird produced more than four. (3) Albumen quality was decreased in nearly all eggs produced.
F
* Dr. J. R. Beach, Division of Veterinary Science, University of California, made the diagnoses.
and eggs were candled. Three types of egg abnormality were observed in varying' numbers; these were (1) air bubbles (as described above) including a few eggs with bubbles in addition to an air cell, (2) poor shells, (3) apparently weak albumens (as estimated by candling). Eggs were obtained from birds that had first shown symptoms of the disease from 7 to 36 days previously. The incidence of air bubbles varied from 0 to 10 percent of individual groups of birds, and, altogether, about 4 percent of all of the approximately 4,000 eggs examined on the 3 ranches were bubbly. The average shell quality of the eggs examined on these 3 ranches was considerably worse than is usual for pullet flocks, and a number of eggs were observed with definitely imperfect shells. These included eggs with normal air cells as well as bubbly eggs. There seemed to be only a slight association between the occurrence of bubbles and poor shell quality, for a large number of the bubbly eggs had perfect shells but when more accurate data were obtained an association was found to exist. About 12 percent of the shells of the bubbly eggs were checked or cracked. A certain minimum time after the start of the disease seemed to be necessary for the production of bubbly eggs. T h e few eggs obtained as early as the seventh day after the first observed symptoms were almost free of the bubbly condition; however, over 6 percent of the eggs from the same group of birds 10 days later were
[193]
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
IELD reports have recently called the attention of the authors to an abnormality of fresh-laid eggs that in each instance was stated to have followed an outbreak of avian pneumoencephalitis. Such flocks were reported to produce a moderately large percentage of eggs containing no true air cell but instead an accumulation of small free-floating air bubbles. An exceptionally large number of eggs with poor shells was also reported produced by these flocks. Other reports have been received of flocks producing eggs with unexplainably poor albumen quality. A few of these reports that could be followed up yielded a history of a respiratory disease in the flock. Avian pneumoencephalitis "is characterized by a sudden onset and extremely rapid spread through a flock" (Beach, 1942) and often almost as rapid spread from flock to flock through a region. Adult mortality is usually low but egg production declines sharply and may cease entirely within a week after the first symptoms appear and only gradually returns to normal. In order to investigate the influence of this disease on subsequently produced eggs, two separate studies were made. In the first (or preliminary) study, three ranches were visited (2 twice and 1 three times) where the flocks were known to be recovering from an outbreak of disease diagnosed* as avian pneumoencephalitis,
194
F. W. LORENZ AND W. E. NEWLON
pen the onset of symptoms was sudden and complete. Many of the birds were prostrated and the floor was littered with soft-shelled eggs. Egg production dropped abruptly and by the third day no eggs were produced. All birds remained out of production for at least 7 days (except for 3 that produced one abnormal-shelled egg each during this period); 4 birds returned to lay on the eleventh day, and egg production was back to its former level about a month after the symptoms were first observed. Only 8 of the 100 birds had not returned to production by the end of the observation period. TABLE 1.—Summary of egg types laid by 92 birds after infection with pneumoencephalitis No. eggs
Percent of all eggs
81 83 27
6.26 6.42 2.09
Total abnormal Total normal
137 1157
10.59 89.42
Total eggs
1294
Abnormal shells Bubbly eggs Less duplication
100.0
A total of 1,294 eggs were laid by 92 birds during the observation period after the onset of the disease (Table 1). Of these, 83 or 6.4 percent were bubbly. All of the birds were not equally responsible for the production of this type of egg; in fact, 66, or 80 percent, of all bubbly eggs were produced by just 8 birds, and another 12 birds laid the remaining 17 (Table 2). Thus only 21.7 percent of the flock produced any eggs with this abnormality. No regularity was observed in the production of bubbly eggs by the birds that laid less than 4 such eggs each. These eggs apparently occurred at random anywhere between the first and last egg laid during the observation period after the onset of the disease. Among the birds that laid a
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
bubbly. Between 19 and 29 days after the onset of symptoms, from 2 to 10 percent of the eggs from individual groups had bubbles, and 30 to 39 days after the start of the disease, 0 to 4.6 percent were bubbly. The incidence of bubbles bore no direct relation to the severity of the disease. In fact, the greatest percentage of bubbly eggs were obtained from a group of birds that showed relatively mild symptoms, while the flock that had the severest epidemic with the highest mortality produced only a moderate number of bubbly eggs. The latter flock, however, did produce a larger number of eggs with apparently weak albumen than was observed on the other ranches. The second study was made; when the opportunity- offered, in order to obtain data under somewhat better controlled conditions. Eggs were acquired from a trap-nested breeding flock, as yet uninfected but known to be in immediate danger of infection from its proximity to infected flocks. One hundred pullets from two trap-nest pens were selected for study; several days' egg production was obtained and examined before symptoms of the disease were observed. Unfortunately, due largely to the commercial nature of the establishment, the observations had to be terminated sooner than was desired and material was not available for histological study. However, all eggs produced by these birds up to 45 days after the start of the epidemic were candled. In addition, the eggs produced on two consecutive days each week were broken for albumen height measurement (Wilgus and Van Wagenen, 1936). All such eggs were broken the day they were laid. The course of the disease was typical. Four days elapsed between its inception in the first and second pen, but within each
INFLUENCE OF AVIAN PNEUMOENCEPHALITIS ON SUBSEQUENT EGG QUALITY
195
TABLE 2.—Distribution of abnormal egg production (Birds classified according to type of abnormal eggs laid after infection.) Data on birds that produced eggs No abnormal eggs
Bubbly eggs (no abnormal shells) 1 1
Few bubbly eggs
1 4
2 4
1 6
16.3
11.3
12.5
14.3
13.3
21
16.7
20.2
16.0
12.0
11.0
20
15.3
17.7
14.5
1.8
3.3
2 24
1 17
2 11
20
19.3
12.6
18.3
13
12.9
11.9
17.8
12.1
12.9
11.9
16.4
10.4
1.4
1.7 1
'
1.3
2 2
Many bubbly eggs
2 3
1 20
majority of the bubbly eggs, however, a definite pattern was evident; 6 of the 8 returned to lay reasonably early and produced 2 or 3 eggs with normal air cells before pausing again for 9 to 13 days. They then resumed production, laying bubbly eggs only (or at most one or two with normal air cells toward the end of the observation period). The seventh bird showed a similar pattern except that the first egg laid was bubbly; this was followed immediately by 5 eggs with normal air cells and then by an 11-day pause after which all eggs but one were bubbly. The eighth bird returned to lay late and all eggs produced during the observation period were bubbly. Those birds which laid bubbly eggs returned to production nearly a week earlier, on the average, than did those that produced only normal eggs. The average rate of production was about the same in each group. The production of eggs with abnormal shells followed a pattern different from
Both bubbly eggs and abnormal shells
1.0
0
0.8
0.8
1.0
0.5
5.8
5.3
0.5
1.0
3.8.
1.8
that observed for bubbly eggs. Altogether 81 eggs had some observable shell abnormality. These were produced by 44 birds, and no bird produced more than 4 such eggs. The occurrence of abnormal shells was fairly evenly distributed throughout the observation period. A total of 27 eggs had both abnormal shells and bubbles, as compared with 54 having abnormal shells as the sole defect and 56 having bubbles but normal shells. Thus the twot conditions are at least partially independent. That they are not completely independent, however, is evident from the excess of doubly abnormal eggs over the number expected from chance alone (5.2). If more restricted groups of birds are considered, such an excess is still found, and even if the produce of the 8 birds that laid mostly bubbly eggs is considered alone there is still an excess of two eggs (22 as compared with 20 expected). There is thus some association between the production of the two • types of defect.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
Pen No. of birds Average date resumption of production, October Average number of eggs per bird Average number normal eggs per bird Average number eggs with abnormal shells per bird Average number bubbly eggs per bird Average number eggs with both bubbles and abnormal shells per bird
Abnormal shells (no bubbles)
196
F. W. LORENZ AND W. E. NEWLON TABLE 3.—Average albumen height decrease at various dates after infection Date (October)*
Pen 1
Pen 2
9
8
16
15 8
11 ,
1 No. of eggs Ave. decrease in albumen height, mm. 3.52 P
3 1.22 0.23
1.72 0.005
1.27 0.005
No. of eggs Ave. decrease in albumen height, mm. P
2
7
4
3.85 0.36
2.27 0.013
1.60 0.053
22 14 0.84 0.004 13 1.14 <0.001
23 17 1.13 0.002 16
28 21 1.07 <0.001 18
1.51 1.30 <0.001 " <0.001
29 22 0.98 <0.001 21 1.69 <0.001
* First symptoms of the disease were observed on September 23 in Pen 1 and on September 27 in Pen 2.
existence of a relation between the amount of loss of albumen quality and the production of other egg abnormalities. In order to test the existence of such a reflation, the birds were grouped according to type of egg abnormality produced (Table 4) and the average albumen height losses of the various groups were computed separately. Eggs of birds that produced some bubbly eggs but no abnormal shells had an average albumen height loss of 0.93 mm., those from birds that produced some abnormal shells but no bubbles lost 1.20 mm., while birds that produced neither lost 1.04 mm. None of these averages differ significantly, but eggs from birds that produced both abnormal shells and bubbles lost an average of 2.51 mm., and this value is significantly larger than any of the other averages. All the 8 birds that produced the majority of bubbly eggs were in the latter group, and eggs from these birds lost an average of 2.70 mm., as compared with a loss of 2.40 mm. in eggs from the rest of the birds in that group. These two values are not significantly different, however. Thus there seems to be no relation between the amount of loss of albumen height and the incidence of either shell defects or bubbles, nor any significant relation with intensity of egg defect production. The only relation seems to be in the limitation of those
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
The effect of this disease on albumen height of subsequently laid eggs was estimated by comparing the albumen height of each such egg measured with the average value for the same bird obtained immediately before the onset of the disease. Measurements that could be so compared were obtained on 178 eggs from 64 birds (32 in each pen). The results of the albumen height measurements are recorded in Table 3. If days on which less than 4 eggs were obtained are ignored as not constituting an adequate sample, the drop in albumen height on any day varied from 0.84 to 2.27 mm., and each such drop was statistically highly significant. The magnitudes of the decreases from day to day showed little evidence of a trend during the period studied. With a single exception, the average albumen height of eggs from each of the birds was lower after the disease than before, and the greatest average loss was 4.32 mm. The distribution of average losses was apparently bimodal, with one mode between 0.51 and 0.75 mm. and the other between 2.26 and 2.50 mm. The average losses for those birds that also produced both abnormal shells and bubbly eggs were clustered around the higher mode only; the other groups of birds had representatives around both modes. Such a distribution as this suggests the
INFLUENCE OF AVIAN PNEUMOENCEPHALITIS ON SUBSEQUENT EGG QUALITY
197"
TABLE 4.—Albumen height decrease of birds classified according to other egg abnormalities (Each value is an average of measurements obtained from both pens on all dates on which eggs were broken.) Data on birds that produced eggs No abnormal eggs No. of eggs Ave. decrease in albumen height, mm. P
77 1.04
Bubbly eggs and abnormal shells Abnormal shells 60 1.20
DISCUSSION
The exact cause of the egg changes following an outbreak of pneumoencephalitis remains to be determined. The disease is known to attack different parts of the body, and virus has been isolated from several organs such as the lungs, spleen, and brain (Beach, 1942); thus there is no reason to suppose that it might not also attack the oviduct, with resulting effects on its functioning. Histopathological
11
Few bubbly eggs 19
0.93 2.40 All less than 0.001
Many bubbly eggs 11 2.70
studies would be necessary to establish the point. If the defects are produced by such a mechanism, however, the evidence presented suggests that the isthmus and the uterus may be affected independently of each other. The functioning of the magnum of all or nearly all of the birds seems to have been affected, as judged by the change in albumen height even in eggs of birds that produced no other defect. The extent of the effect on the egg albumen was apparently greater in birds in which the entire oviduct was involved, however. The effect of pneumoencephalitis on albumen quality is especially interesting, for this is the first agent, other than age of bird, that has been demonstrated to modify the albumen height of fresh-laid eggs. The two influences are not to be confused; whereas the change due to bird . age is gradual and progressive and, according to Hunter, Van Wagenen and Hall (1936), operative primarily during the spring and summer, the sequela reported here was sudden and severe, occurred during October and did not progress. The severity of the effect was noteworthy; oh the eggs of a number of the affected birds it was such that the inferior albumen quality would have been noticed readily in the course of ordinary commercial handling.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
birds that produced eggs with all three types of defects to the more severe stage of albumen height loss. Since the possibility was not ruled out that part or all of the loss in albumen quality was directly due to the pause in production rather than to a specific effect of the disease, a test of the effect of pause was obtained from previous quality records of the Poultry Division egg quality breeding flock. The bird records used were those that included measurements on at least 2 eggs before and 2 eggs after a winter pause (8 consecutive days or more out of production during November or December). Records of 12 such birds were chosen at random. The average albumen height of eggs of these birds (on a bird average basis) was 6.81 mm. before and 6.91 mm. after the pause. Thus no loss could be attributed to the pause per se.
Bubbly eggs
198
NEWS AND NOTES SUMMARY
REFERENCES
Beach, J. R., 1942. Avian pneumoencephalitis. Proc. 46th Ann. Meeting U. S. Livestock Sanitary Assn., 203-223. Hunter, J. A., A. Van Wagenen, and G. 0 . Hall, 1936. Seasonal changes in interior egg quality of Singfe-Comb White Leghorn hens. Poultry Sci. 15:115-118. Wilgus, Jr., H. S., and A. Van Wagenen, 1936. The height of the firm albumen as a measure of its condition. Poultry Sci. 15:319-321.
News and Notes E. P. Singsen (B.S. Rhode Island State College '38), (M.S. North Carolina State College '40) has been appointed Assistant Professor of Poultry Husbandry at the University of Connecticut. Mr. Singsen will devote full time to research in poultry nutrition. At the time of his appointment, Mr. Singsen was associated with the University of Illinois as an Assistant in Animal Husbandry working on the doctorate program. G. P. Goodearl a graduate of Connecticut in the class of 1922 and formerly associated with Montana State College, but more recently the North Dakota Agricultural Experiment Station, joined the staff as Assistant Professor, January 1944. Mr. Goodearl will assume the supervisoryship of the Storrs Egg Laying Test, the research work in turkeys and assist with the teaching program.
Dr. Alfred M. Lucas has resigned as Associate Professor of Zoology at Iowa State College to accept a position as Cytopathologist at the U. S. Regional Poultry Research Laboratory, East Lansing, Mich. Dr. Harris D. Webster, veterinarian at the Regional Poultry Research Laboratory, reported for military duty on March 29. Dr. Webster is a first lieutenant in the Veterinary Corps. Capt. James H. Bywaters was promoted to the rank of Major effective March 8. At present he is stationed in Washington, D. C. Capt. George E. Cottral is now serving in the Veterinary Corps somewhere in India. Dr. L. E. Card has called attention to the fact that July 1 is the deadline for entries for either The Poultry Science Research Prize or The Borden Award.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 5, 2015
Eggs laid by chickens up to 45 days after an outbreak of avian pneumoencephalitis were examined. The following observations were made: (1) Up to 10 percent of the eggs produced during this period failed to form normal air cells; air present in the egg was in free-floating bubbles. Most of such eggs were produced by relatively few birds. (2) A considerable number of eggs with abnormal shells were produced. Their production by affected birds was more evenly distributed than the production of bubbly
eggs; abnormal shells were produced by the majority of the flock, yet no bird produced more than four. (3) Albumen quality was decreased in nearly all eggs produced.