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Effect of Ventilation Rate on the Response of Chicks Inoculated with Infectious Bronchitis Virus and Housed at 49°F.1
1512
T. G. TAYLOR AND F. HERTELENDY
Taylor, L. W., and I. M. Lerner, 1939. Inheritance of eggshell thickness in White Leghorn pullets. J. Agric. Res. 58: 383-396. Tyler, C , 1956. The metabolic significance of variations in the shell calcium: retained calcium re-
lationship between individual laying hens. J. Agric. Sci. 48: 171-174. Tyler, C , and F. H. Geake, 1961. Critical appraisal of various methods of assessing shell thickness. J. Sci. Fd Agric. 12 : 281-289.
Effect of Ventilation Rate on the Response of Chicks Inoculated with Infectious Bronchitis Virus and Housed at 49°F.1 R. P. PRINCE, 2 L. D. MATTERSON,3 R. E. LUGINBUHL" AND T. W. Storrs (Connecticut) Agricultural Experiment Station, Storrs
CHOMIAK4
(Received for publication February 19, 1962)
E
XPERIMENTS conducted by Hudson (1931) with bronchitis virus infected chicks showed that mortality was 60 percent for those group maintained at 66°F. as compared to 32 percent for the 100°F. groups. In an experiment conducted at 75°F. involving infectious bronchitis virus and ventilation rates of f and 2 cfm. per bird, Prince et al. (1962) found that infected chicks four to eight weeks of age gained significantly less weight and consumed significantly less feed than the noninfected groups. Differences in weight gain and feed consumption due to ventilation rate were not significant. Differences in feed efficiency and mortality due to disease and/or ventilation rate were not significant. This experiment was designed to measure the performance of chicks as affected by infection bronchitis virus and ventilation rate. It was conducted in the same manner as the previous one, Prince et al. (1962), except that the temperature on all groups averaged 49°F. 1 This study was conducted as a part of a contributing project to Regional Research Project, NE-8 entitled, "Essentials of Poultry Housing in the Northeast." 2 Agricultural Engineering Department. 3 Poultry Science Department. 4 Animal Diseases Department.
MATERIALS AND METHODS
The schematic diagram in Figure 1 shows the arrangement of control devices and pattern of air flow for each of four environmental cabinets used in this experiment. Two cabinets were located in each of two temperature controlled rooms. The cabinets which measured 4 feet wide by 4 feet high by 8 feet long were constructed of plywood and insulated. The floor space allocation for 20 birds per cabinet was about 1.1 square feet per bird. Air flow measurements were made at the intake of each plenum chamber and the flow was regulated with fan speed and sharp-edged orifice plates. Electric heaters and electronic thermostats were used to maintain cabinet temperatures. For each of four trials, conducted between October 25, 1960 and April 7, 1961, 125 White Plymouth Rock day-old male chicks were obtained from a local hatchery and raised under isolation for four weeks in battery brooders. Eighty chicks in the central weight range were selected and assigned to four 20-bird groups. The chicks of two groups were then inoculated intranasally with 10° chicken infective doses of infectious bronchitis virus (Massachusetts type). Chicks of the other two groups were not inoculated. Two groups were
1513
D I S E A S E AND V E N T I L A T I O N
I50W 250 W 250 W
T *
3 5
-
150' . WATT HEATER
50 W PLEN
EXHAUST
DUCT
THERMOHM THERMISTOR
StNSING ELEMENT
/ WALL MOUNTED
THERMOCOUPLE
\ FEED WATER
JK
-52-
m
FIG. 1. Schematic diagram of environmental cabinet showing equipment arrangement and location of controls.
ventilated at a rate of 2 cfm. per bird and the other two at f cfm. per bird. Assignment of inoculated and ventilation treatments to the cabinets was made according to a Magic Latin square design which assured that the two inoculated groups were housed in cabinets located in the same room. All cabinet and room thermostats were adjusted to maintain a temperature of 45°F. on all treatments. However, after the first week cabinet temperatures began to increase in the low ventilated cabinets due to heat production by the chicks and at the end of the four-week period a temperature of 55°F. had been reached. All cabinets were kept in this adjustment so as to follow the same path of temperature increase for each trial. Thus the average environmental temperature for the four-week period was about 49 °F. Initial and final bird weights and total feed consumption were obtained for each treatment. From these data and a mortality record, the feed efficiency of each group was calculated. Statistical analyses of the
weight gain, feed consumption and feed efficiency data were made according to Federer (19SS). Three birds were selected at random from each cabinet at the end of each trial. These birds were bled and the samples checked for infectious bronchitis virus antibodies. About three-eighths inch of dry screened sand was used as litter in each cabinet and remained undisturbed throughout each trial. Water was provided by an automatic float-operated container located near the service door in each cabinet. Twenty-four lighting was insured by using two 15-watt light bulbs. A practical type starter and broiler ration was mixed on the University poultry farm and a sufficient quantity was on hand from one mix for each trial. Separate bulk feed containers and utensils were used with a staggered schedule of feeding the infected and noninfected groups to minimize the chance for contamination between groups. Sterile boots and coveralls were used when caring for both groups. One 6 inch wide by 6 feet long feeder was pro-
1514
R. P. PRINCE, L. D. MATTERSON, R. E. LUGINBUHL AND T. W. CHOMIAK
TABLE 1.—A verage eight-week weight of chicks following a four-week treatment, pounds
In each trial the infected treatments showed uniform respiratory signs within 48 hours of inoculation, whereas no respiratory signs appeared in the noninfected treatments. Results of blood samples checked for infectious bronchitis virus antibodies showed no contamination between
treatments (1,000 VND considered positive) . The average chick weights at the end of each trial are given in Table 1. Differences in the four to eight week weight gains due to ventilation rate were not significant (Tables 2 and 5). However, chicks in the infected groups gained an average of 0.33 pounds per bird less weight than the noninfected groups. This difference due to the bronchitis virus infection represented a 16 percent decrease in average weight gain and was highly significant. The analysis of variance (Table 5) indicated a significant difference in weight gain among trials which may have resulted from differences among hatches of chicks and variations in ingredients used in the various mixes of the ration. Feed consumption of chicks in the infected groups averaged 0.66 pounds per bird less than in the noninfected groups (Table 3). This difference due to the bronchitis virus infection was highly significant (Table 5) and amounted to a 11.4 percent decrease in feed intake of the infected chicks as compared to the noninfected chicks. Differences in feed consumption due to rate of ventilation were not significant.
TABLE 2.—Average weight gain of chicks as affected by infectious bronchitis virus and ventilation rate, pounds
TABLE 3.—Average feed consumption of chicks as affected by infectious bronchitis virus and ventilation rate, pounds
Ventilation rate j cfm. per bird
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
1 2 3 4
Average Average
Infected
3.439 3.204 2.938 3.254
2.896 2.925 2.617 2.903
3.209
2.835
3.444 3.096 2.847 3.124
2.985 2.872 2.502 2.977
3.128 3.169
2.834 2.835
Average
3.022
2.981 3.002
vided for each cabinet and was fitted with a piece of turkey wire, 1 inch by 2 inch mesh, to minimize feed wastage. The height of each feeder was adjusted preiodically so as to keep the top edge level with the bird's back. RESULTS AND DISCUSSION
Ventilation rate f cfm. per bird.
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
Average Average
1 2 3 4
T - . , Infected
.
Avera
§e
2.260 2.079 1.872 2.254
1.715 1.821 1.536 1.895
2.116
1.742
2.261 1.998 1.769 2.124
1.809 1.772 1.430 1.972
2.038
1.746
1.892
2.077
1.744
1.911
Ventilation rate | cfm. per bird
1.929
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
Average Average
1 2 3 4
T , , , Infected
.
Avera
§e
5.933 5.702 6.016 5.652
5.000 5.100 5.204 5.106
5.826
5.103
6.081 5.723 5.805 5.600
5.354 5.198 5.069 5.163
5.802
5.196
5.499
5.814
5.150
5.482
5.465
1515
DISEASE AND VENTILATION TABLE 4.—Average feed efficiency of chicks four to eight weeks of age as affected by infectious bronchitis virus and ventilation rate, pounds of gain per pound of feed Ventilation Rate J cfm. per bird
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
1 2 3 4
Average Average
. , T c Infected
.
Avera
§e
0.381 0.365 0.311 0.399
0.343 0.357 0.295 0.371
0.364
0.342
0.372 0.349 0.305 0.379
0.338 0.341 0.282 0.382
0.351
0.336
0.344
0.358
0.339
0.349
0.353
The absence of a ventilation X disease interaction indicates that the differences due to disease in weight gain and feed consumption were consistent at each ventilation rate. Feed efficiency was significantly lower for the infected groups than for the noninfected ones as indicated in Tables 4 and 5. The differences amounted to 0.02 pounds of gain per pound of feed for the four to eight week period. This effect was not observed by Prince et al. (1962) in a similar experiment where the temperature was maintained at 75°F. It is postulated that
the added stress created by the disease was more severe at the 49°F. environment which resulted in a prolonged recovery period. The analysis of variance indicated a significant effect for ventilation rate on feed efficiency. A similar yet a more complex effect was observed by Prince et al. (1961) in an experiment involving chicks of the same breed and age. These observed effects tend to support the theory that low temperature and high ventilation rates are not conducive to maintaining body temperature at a normal metabolic rate. The highly significant effect among trials as indicated by the analysis of variance for feed efficiency may have resulted from variations in ration ingredients from mix to mix and differences among chicks even though all chicks were obtained from the same hatchery and the same formula was fed in each trial. Mortality records showed that 4 chicks died of the 160 infected with infectious bronchitis virus and 2 died of an equal number of non-infected chicks. The records show that 4 and 2 chicks died of the 160 exposed to each of f and 2 cfm. per bird respectively. Differences among the number of mortality were not significant in either case.
TABLE 5.—Analysis of variance of weight gain, feed consumption and feed efficiency of chicks four to eight weeks of age Weight gain Degrees Source of variation of freedom Trails Cabinets Ventilation (V) Disease (D) Squares (VXD) Interaction Error
3 3 1 1 1 1 5
Mean Squares X10-3 133.169 2.829 5.513 444.556 28.645 6.765 4.705
* Significant at the 0.05 level. ** Significant at the 0.01 level. *** Significant at the 0.001 level.
F-Value
Feed consumption Mean squares
xio~ 28.30** 94.49***
3
35.735 11.727 4.899 1,767.570 75.350 13.689 12.675
Feed efficiency
F-Value
Mean squares XIO-*
139.45***
509.042 7.301 34.225 144.400 30.625 4.900 4.160
F-Value 122.37*** 8.23* 34.71** 7.36
1516
R. P. PRINCE, L. D. MATTEESON, R. E. LUGINBUHL AND T. W. SUMMARY
For each of four trials, four groups of twenty 4 to 8 week-old White Plymouth Rock male chicks were raised in four environmental cabinets maintained at an average temperature of 49°F. Two groups were inoculated with infectious bronchitis at four weeks of age and ventilated at J and 2 cfm. per bird, respectively. The other two groups received the same ventilation treatments but were not inoculated. Weight gain of chicks in the infected groups was significantly lower than in the noninfected groups. The difference amounted to 0.33 pounds per bird for the four-week period. Differences in weight gain due to ventilation rate were not significant. Feed consumption was significantly lower in the infected than in the noninfected groups and amounted to 0.66 pounds per bird. Differences in feed consumption due to ventilation rate were not significant.
CHOMIAK
Feed efficiency of chicks in the infected groups was significantly lower than in the noninfected groups. Differences in mortality due to disease or rate of ventilation were not significant. ACKNOWLEDGMENTS
Gratitude is expressed to D. G. Gosslee, Station Biometrician, for assistance in experimental design and analysis of the data. REFERENCES Federer, W. T., 19SS. Experimental Design. The Macmillan Company, New York, 478-482. Hudson, C. B., 1931. The influence of environmental temperature on the mortality in chicks inoculated with the virus of infectious bronchitis. Poultry Sci. 10: 391. Prince, R. P., L. M. Potter and W. W. Irish, 1961. Response of chicks to temperature and ventilation environments. Poultry Sci. 40: 102-108. Prince, R. P., L. M. Potter, R. E. Luginbuhl and T. Chomiak, 1962. Effect of ventilation rate on the response of chicks inoculated with infectious bronchitis virus. Poultry Sci. 4 1 : 268-272.
A Rapid Method for Evaluating the Strength of the Vitelline Membrane of the Hen's Egg Yolk* Departments
DANIEL FROMM AND GENNARD MATRONE of Food Science and Animal Industries, North Carolina Agricultural Experiment Station, Raleigh, North Carolina (Received for publication February 19. 1962)
P
REVIOUS methods for determining the strength of the vitelline membrane of the hen's egg yolk have involved the rupturing of the vitelline membrane to the extent that the yolk is no longer intact after measurements have been made. Haugh (1933) used the direct application of pressure to the yolk until rupturing of the membrane occurred. Munro and Rob* Published with the approval of the Director of Research as Research Paper No. 1418 of the Journal Series.
ertson (1935) employed a vacuum principle wherein the yolk contents were removed and the force in mm. Ffg required to rupture the membrane in a given section was determined. Moran (1936) placed the yolk into an isotonic sucrose solution and introduced a tube onto the surface of the yolk. As pressure was applied by lowering the tube, the membrane rose in the tube until rupturing occurred. By use of physical constants, the height of the membrane in the tube immediately prior to bursting
T. G. TAYLOR AND F. HERTELENDY
Taylor, L. W., and I. M. Lerner, 1939. Inheritance of eggshell thickness in White Leghorn pullets. J. Agric. Res. 58: 383-396. Tyler, C , 1956. The metabolic significance of variations in the shell calcium: retained calcium re-
lationship between individual laying hens. J. Agric. Sci. 48: 171-174. Tyler, C , and F. H. Geake, 1961. Critical appraisal of various methods of assessing shell thickness. J. Sci. Fd Agric. 12 : 281-289.
Effect of Ventilation Rate on the Response of Chicks Inoculated with Infectious Bronchitis Virus and Housed at 49°F.1 R. P. PRINCE, 2 L. D. MATTERSON,3 R. E. LUGINBUHL" AND T. W. Storrs (Connecticut) Agricultural Experiment Station, Storrs
CHOMIAK4
(Received for publication February 19, 1962)
E
XPERIMENTS conducted by Hudson (1931) with bronchitis virus infected chicks showed that mortality was 60 percent for those group maintained at 66°F. as compared to 32 percent for the 100°F. groups. In an experiment conducted at 75°F. involving infectious bronchitis virus and ventilation rates of f and 2 cfm. per bird, Prince et al. (1962) found that infected chicks four to eight weeks of age gained significantly less weight and consumed significantly less feed than the noninfected groups. Differences in weight gain and feed consumption due to ventilation rate were not significant. Differences in feed efficiency and mortality due to disease and/or ventilation rate were not significant. This experiment was designed to measure the performance of chicks as affected by infection bronchitis virus and ventilation rate. It was conducted in the same manner as the previous one, Prince et al. (1962), except that the temperature on all groups averaged 49°F. 1 This study was conducted as a part of a contributing project to Regional Research Project, NE-8 entitled, "Essentials of Poultry Housing in the Northeast." 2 Agricultural Engineering Department. 3 Poultry Science Department. 4 Animal Diseases Department.
MATERIALS AND METHODS
The schematic diagram in Figure 1 shows the arrangement of control devices and pattern of air flow for each of four environmental cabinets used in this experiment. Two cabinets were located in each of two temperature controlled rooms. The cabinets which measured 4 feet wide by 4 feet high by 8 feet long were constructed of plywood and insulated. The floor space allocation for 20 birds per cabinet was about 1.1 square feet per bird. Air flow measurements were made at the intake of each plenum chamber and the flow was regulated with fan speed and sharp-edged orifice plates. Electric heaters and electronic thermostats were used to maintain cabinet temperatures. For each of four trials, conducted between October 25, 1960 and April 7, 1961, 125 White Plymouth Rock day-old male chicks were obtained from a local hatchery and raised under isolation for four weeks in battery brooders. Eighty chicks in the central weight range were selected and assigned to four 20-bird groups. The chicks of two groups were then inoculated intranasally with 10° chicken infective doses of infectious bronchitis virus (Massachusetts type). Chicks of the other two groups were not inoculated. Two groups were
1513
D I S E A S E AND V E N T I L A T I O N
I50W 250 W 250 W
T *
3 5
-
150' . WATT HEATER
50 W PLEN
EXHAUST
DUCT
THERMOHM THERMISTOR
StNSING ELEMENT
/ WALL MOUNTED
THERMOCOUPLE
\ FEED WATER
JK
-52-
m
FIG. 1. Schematic diagram of environmental cabinet showing equipment arrangement and location of controls.
ventilated at a rate of 2 cfm. per bird and the other two at f cfm. per bird. Assignment of inoculated and ventilation treatments to the cabinets was made according to a Magic Latin square design which assured that the two inoculated groups were housed in cabinets located in the same room. All cabinet and room thermostats were adjusted to maintain a temperature of 45°F. on all treatments. However, after the first week cabinet temperatures began to increase in the low ventilated cabinets due to heat production by the chicks and at the end of the four-week period a temperature of 55°F. had been reached. All cabinets were kept in this adjustment so as to follow the same path of temperature increase for each trial. Thus the average environmental temperature for the four-week period was about 49 °F. Initial and final bird weights and total feed consumption were obtained for each treatment. From these data and a mortality record, the feed efficiency of each group was calculated. Statistical analyses of the
weight gain, feed consumption and feed efficiency data were made according to Federer (19SS). Three birds were selected at random from each cabinet at the end of each trial. These birds were bled and the samples checked for infectious bronchitis virus antibodies. About three-eighths inch of dry screened sand was used as litter in each cabinet and remained undisturbed throughout each trial. Water was provided by an automatic float-operated container located near the service door in each cabinet. Twenty-four lighting was insured by using two 15-watt light bulbs. A practical type starter and broiler ration was mixed on the University poultry farm and a sufficient quantity was on hand from one mix for each trial. Separate bulk feed containers and utensils were used with a staggered schedule of feeding the infected and noninfected groups to minimize the chance for contamination between groups. Sterile boots and coveralls were used when caring for both groups. One 6 inch wide by 6 feet long feeder was pro-
1514
R. P. PRINCE, L. D. MATTERSON, R. E. LUGINBUHL AND T. W. CHOMIAK
TABLE 1.—A verage eight-week weight of chicks following a four-week treatment, pounds
In each trial the infected treatments showed uniform respiratory signs within 48 hours of inoculation, whereas no respiratory signs appeared in the noninfected treatments. Results of blood samples checked for infectious bronchitis virus antibodies showed no contamination between
treatments (1,000 VND considered positive) . The average chick weights at the end of each trial are given in Table 1. Differences in the four to eight week weight gains due to ventilation rate were not significant (Tables 2 and 5). However, chicks in the infected groups gained an average of 0.33 pounds per bird less weight than the noninfected groups. This difference due to the bronchitis virus infection represented a 16 percent decrease in average weight gain and was highly significant. The analysis of variance (Table 5) indicated a significant difference in weight gain among trials which may have resulted from differences among hatches of chicks and variations in ingredients used in the various mixes of the ration. Feed consumption of chicks in the infected groups averaged 0.66 pounds per bird less than in the noninfected groups (Table 3). This difference due to the bronchitis virus infection was highly significant (Table 5) and amounted to a 11.4 percent decrease in feed intake of the infected chicks as compared to the noninfected chicks. Differences in feed consumption due to rate of ventilation were not significant.
TABLE 2.—Average weight gain of chicks as affected by infectious bronchitis virus and ventilation rate, pounds
TABLE 3.—Average feed consumption of chicks as affected by infectious bronchitis virus and ventilation rate, pounds
Ventilation rate j cfm. per bird
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
1 2 3 4
Average Average
Infected
3.439 3.204 2.938 3.254
2.896 2.925 2.617 2.903
3.209
2.835
3.444 3.096 2.847 3.124
2.985 2.872 2.502 2.977
3.128 3.169
2.834 2.835
Average
3.022
2.981 3.002
vided for each cabinet and was fitted with a piece of turkey wire, 1 inch by 2 inch mesh, to minimize feed wastage. The height of each feeder was adjusted preiodically so as to keep the top edge level with the bird's back. RESULTS AND DISCUSSION
Ventilation rate f cfm. per bird.
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
Average Average
1 2 3 4
T - . , Infected
.
Avera
§e
2.260 2.079 1.872 2.254
1.715 1.821 1.536 1.895
2.116
1.742
2.261 1.998 1.769 2.124
1.809 1.772 1.430 1.972
2.038
1.746
1.892
2.077
1.744
1.911
Ventilation rate | cfm. per bird
1.929
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
Average Average
1 2 3 4
T , , , Infected
.
Avera
§e
5.933 5.702 6.016 5.652
5.000 5.100 5.204 5.106
5.826
5.103
6.081 5.723 5.805 5.600
5.354 5.198 5.069 5.163
5.802
5.196
5.499
5.814
5.150
5.482
5.465
1515
DISEASE AND VENTILATION TABLE 4.—Average feed efficiency of chicks four to eight weeks of age as affected by infectious bronchitis virus and ventilation rate, pounds of gain per pound of feed Ventilation Rate J cfm. per bird
Trial NonNo. infected 1 2 3 4
Average 2 cfm. per bird
1 2 3 4
Average Average
. , T c Infected
.
Avera
§e
0.381 0.365 0.311 0.399
0.343 0.357 0.295 0.371
0.364
0.342
0.372 0.349 0.305 0.379
0.338 0.341 0.282 0.382
0.351
0.336
0.344
0.358
0.339
0.349
0.353
The absence of a ventilation X disease interaction indicates that the differences due to disease in weight gain and feed consumption were consistent at each ventilation rate. Feed efficiency was significantly lower for the infected groups than for the noninfected ones as indicated in Tables 4 and 5. The differences amounted to 0.02 pounds of gain per pound of feed for the four to eight week period. This effect was not observed by Prince et al. (1962) in a similar experiment where the temperature was maintained at 75°F. It is postulated that
the added stress created by the disease was more severe at the 49°F. environment which resulted in a prolonged recovery period. The analysis of variance indicated a significant effect for ventilation rate on feed efficiency. A similar yet a more complex effect was observed by Prince et al. (1961) in an experiment involving chicks of the same breed and age. These observed effects tend to support the theory that low temperature and high ventilation rates are not conducive to maintaining body temperature at a normal metabolic rate. The highly significant effect among trials as indicated by the analysis of variance for feed efficiency may have resulted from variations in ration ingredients from mix to mix and differences among chicks even though all chicks were obtained from the same hatchery and the same formula was fed in each trial. Mortality records showed that 4 chicks died of the 160 infected with infectious bronchitis virus and 2 died of an equal number of non-infected chicks. The records show that 4 and 2 chicks died of the 160 exposed to each of f and 2 cfm. per bird respectively. Differences among the number of mortality were not significant in either case.
TABLE 5.—Analysis of variance of weight gain, feed consumption and feed efficiency of chicks four to eight weeks of age Weight gain Degrees Source of variation of freedom Trails Cabinets Ventilation (V) Disease (D) Squares (VXD) Interaction Error
3 3 1 1 1 1 5
Mean Squares X10-3 133.169 2.829 5.513 444.556 28.645 6.765 4.705
* Significant at the 0.05 level. ** Significant at the 0.01 level. *** Significant at the 0.001 level.
F-Value
Feed consumption Mean squares
xio~ 28.30** 94.49***
3
35.735 11.727 4.899 1,767.570 75.350 13.689 12.675
Feed efficiency
F-Value
Mean squares XIO-*
139.45***
509.042 7.301 34.225 144.400 30.625 4.900 4.160
F-Value 122.37*** 8.23* 34.71** 7.36
1516
R. P. PRINCE, L. D. MATTEESON, R. E. LUGINBUHL AND T. W. SUMMARY
For each of four trials, four groups of twenty 4 to 8 week-old White Plymouth Rock male chicks were raised in four environmental cabinets maintained at an average temperature of 49°F. Two groups were inoculated with infectious bronchitis at four weeks of age and ventilated at J and 2 cfm. per bird, respectively. The other two groups received the same ventilation treatments but were not inoculated. Weight gain of chicks in the infected groups was significantly lower than in the noninfected groups. The difference amounted to 0.33 pounds per bird for the four-week period. Differences in weight gain due to ventilation rate were not significant. Feed consumption was significantly lower in the infected than in the noninfected groups and amounted to 0.66 pounds per bird. Differences in feed consumption due to ventilation rate were not significant.
CHOMIAK
Feed efficiency of chicks in the infected groups was significantly lower than in the noninfected groups. Differences in mortality due to disease or rate of ventilation were not significant. ACKNOWLEDGMENTS
Gratitude is expressed to D. G. Gosslee, Station Biometrician, for assistance in experimental design and analysis of the data. REFERENCES Federer, W. T., 19SS. Experimental Design. The Macmillan Company, New York, 478-482. Hudson, C. B., 1931. The influence of environmental temperature on the mortality in chicks inoculated with the virus of infectious bronchitis. Poultry Sci. 10: 391. Prince, R. P., L. M. Potter and W. W. Irish, 1961. Response of chicks to temperature and ventilation environments. Poultry Sci. 40: 102-108. Prince, R. P., L. M. Potter, R. E. Luginbuhl and T. Chomiak, 1962. Effect of ventilation rate on the response of chicks inoculated with infectious bronchitis virus. Poultry Sci. 4 1 : 268-272.
A Rapid Method for Evaluating the Strength of the Vitelline Membrane of the Hen's Egg Yolk* Departments
DANIEL FROMM AND GENNARD MATRONE of Food Science and Animal Industries, North Carolina Agricultural Experiment Station, Raleigh, North Carolina (Received for publication February 19. 1962)
P
REVIOUS methods for determining the strength of the vitelline membrane of the hen's egg yolk have involved the rupturing of the vitelline membrane to the extent that the yolk is no longer intact after measurements have been made. Haugh (1933) used the direct application of pressure to the yolk until rupturing of the membrane occurred. Munro and Rob* Published with the approval of the Director of Research as Research Paper No. 1418 of the Journal Series.
ertson (1935) employed a vacuum principle wherein the yolk contents were removed and the force in mm. Ffg required to rupture the membrane in a given section was determined. Moran (1936) placed the yolk into an isotonic sucrose solution and introduced a tube onto the surface of the yolk. As pressure was applied by lowering the tube, the membrane rose in the tube until rupturing occurred. By use of physical constants, the height of the membrane in the tube immediately prior to bursting