Preincubation Humidity Variation Effects on Chicken Egg Hatchability

- STATION TECHNICAL BULLETIN 2 MAY 1943 Preincubation Humidity Variation Effects on Chicken Egg Hatchability WILBUR T. COONEY 9TH!`ni i? Oregon State System of Higher Education Agricultural Experiment Station Oregon State College Corvallis

Preincubation Humidity Variation Effects on Chicken Egg Hatchability By WILBUR T. COONEY* INTRODUCTION M ORE persons are probably interested in the production of poultry than in any other single agricultural enterprise. In 1939 more than\8 per cent of all farms in the United States reported poultry as a source of farm income. To take care of a part of the annual requirements for farm flock replacements the commercial hatcheries of the nation in 1941 incubated approximately 1,800,000,000 eggs from which they obtained 1,200,000,000 chicks. This represents a 67 per cent hatch for all eggs set, about 33 eggs out of every 100 set being lost as a result of infertility or embryo mortality. The failure of some 600,000,000 eggs to hatch in commercial hatcheries represents an annual monetary loss of at least $15,000,000 in addition to losses sustained in home-hatching operations and in the hatching of turkey eggs. Hence, every possible addition to our present knowledge of breeding, feeding, management of breeders, and incubation is needed to reduce these hatching losses. Successful incubation of eggs hinges on the proper application of the following four fundamentals: (1) temperature, (2) egg turning, (3) ventilation, and (4) humidity. Of these factors only temperature and egg turning have been given due consideration with respect to their effects on future hatchability of eggs prior to the time of incubation. REVIEW OF LITERATURE Investigational work of A. G. Philips in 1909 cited by H. M. Scott (9)f shows that where eggs were held at 50 F., 65 F., and 80 F. for 14 days the respective per cent hatch of the fertile eggs set was 70.4, 43.1, and 0.0. Scott's own work shows that the temperature at which eggs are held prior to incubation is a most important factor in determining hatchability and the length of time that eggs may be held. When turkey and chicken eggs were held at a temperature of 36 F. and at a relative humidity of 90 per cent over a period of time from 0 to 34 days, hatchability was 68.47 per cent for turkeys and 55.10 per cent for chickens. The holding of eggs at temperatures varying from near or above the physiological zero (60 F. to 75 F.) for prolonged periods or at rather low temperatures (36.3 F.) caused many of the embryos to die during the first few days of incubation. In this work 28 days approached the maximum length of time that eggs could be held under any conditions and still produce chicks when incubated. A comparison of the results of 2 years' ACKNOWLEDGMENT: The writer expresses his sincerest thanks and appreciation to Miss Marjorie Boothby, secretary of the Department of Poultry Husbandry, for her untiring aid in the tedious task of compiling the mass of data that made this paper possible; to Dr. C. E. Holmes, associate professor of poultry husbandry, for his invaluable assistance in analyzing and statistically treating the accumulated data; to the foregoing individuals and Professor H. E. Cosby, head of the Department of Poultry Husbandry, for their reading and constructive suggestions of the manuscript as a unit; and to Raymond Pederson, of the 5A ricultural Engineering Department, for his bell) in completing the control cabinet used in this experiment. t Reference numbers in parenthesis refer to the list of references on page 27.

4 STATION TECHNICAL BULLETIN 2 work clearly points to the necessity of controlling temperature and perhaps humidity in rooms where hatching eggs are to be held., In an effort to determine the reason for existing differences in hatchability of different hens, Bronkhorst and Hall (2) were able to show that the percentage of solids, as measured by the index of refraction of egg white, bears no relation to hatchability. Their low-hatching.hens, however, exhibited a greater variability with respect to the solid content of the yolk and albumen than the high-hatching hens. A. B. Godfrey (3) in studying the effect of egg weight, quantity of total albumen per egg, and quantity of thick albumen per egg on hatchability found a low but significant negative linear correlation between hatchability and weight of total albumen per egg, and hatchability and weight of thick albumen per egg. There was no correlation between hatchability and percentage thick albumen of total albumen per egg. G. O. Hall and A. Van Wagenen (4) in investigating the association of certain measures of interior egg quality with hatchability found that low hatchability was associated with a poor condition of the firm albumen and high hatchability with a good condition of the firm albumen. It is of interest that of the four measures of interior egg quality employed-(i) the score of the condition of the firm albumen, (2) the percentage firm albumen, (3) the percentage outer thin albumen, and (4) the yolk index-only the score of the condition of the firm albumen showed any significant association with hatchability. W. J. Rudy and D. R. Marble (8) in the study of the interrelationship of physical measurements of eggs and their effects upon hatchability found no relationship between egg weights, shell weights, yolk weights, albumen heights, yolk color, the relative tenacity of cohesive quality of firm albumen, and percentage of firm albumen to total albumen, and the percentage hatch of fertile eggs Ṫhough there seems to be little evidence of a relationship between hatchability and egg quality, the value of high humidity in egg storage rooms for the purpose of maintaining egg quality has been amply demonstrated both at the Ohio Agricultural Experiment Station (6) and Oregon State College. N. L. Bennion and F. E. Price (1) reported on results obtained with commercial eggs held under three different temperature and humidity conditions. Under each of the three holding conditions, with a duration of approximately 6 days each, three separate lots of eggs were held. With an average relative humidity of 52 per cent and an average maximum temperature of 80 F. only 23.4 per cent of the eggs graded U.S.-AA. Where the Lt. average relative humidity was 60 per cent and the average maximum temperature 70 F., 34 per cent of the eggs graded U.S.-AA. When the relative humidity was raised to an average of 83 per cent and the average maximum temperature lowered to 66 F., 63 per cent of the eggs graded U.S.-AA. F. P. Jeffry and V. Darago (5) found in their study of the effect of high humidity on egg quality during short holding periods that the percentage dehaps the most outstanding factor in egg quality as viewed by crease in albumen height is closely related to temperature but bears little or no relation to relative humidity. The only effect of humidity on eggs that they could detect was that the higher levels tend to reduce loss in egg weight during holding periods. This reduction in loss of weight retards the enlargement of air cells and hence improves the quality of eggs as judged by commercial candlers in that a great deal of emphasis is normally placed on size of air cells when determining egg grades. It has been shown, however, that size of air cell is not necessarily a reliable index of albumen height, which in turn is perconsumers.

PREINCUBATION HUMIDITY EFFECTS ON EGG HATCHABILITY 5 The only evidence thus far presented and undisputed with respect to egg quality and its influence on hatchability is that presented by Hall and Van Wagenen in which they found a relationship between the score of the condition of the firm albumen and hatchability. Godfrey's findings with respect to hatchability and weight of total albumen per egg and weight of thick albumen per egg cannot be disregarded in considering the effect of humidity on egg quality and, ultimately, egg hatchability. A lengthened holding period and high temperatures adversely affect the score of the condition of firm albumen in eggs and other conditions commonly tested in egg quality measurements, but little or no evidence has been presented showing a direct relationship between egg quality, as consumers think of it, and relative humidity. Egg quality, nevertheless, has been shown to be maintained by the use of high relative humidity in egg storage rooms, though the effect may be indirect. Regardless of whether egg quality is directly or indirectly affected by humidity, and of whether there is any relationship between egg quality and hatchability, it was deemed desirable to test the effect of humidity on eggs being held for incubation. The work reported in this paper was started on April 1, 1941, and concluded in July of the same year. In the month of March when facilities were being prepared for this work, Mack O. North (7) of the Wyoming Agricultural Experiment Station reported favorably on the use of high relative humidity in rooms where eggs were being held for future incubation. His work showed that raising the humidity of the air surrounding eggs during the holding period to approximately 50 per cent was of benefit, particularly if the eggs were held more than a week. Eggs held for 10 days hatched about 4 per cent better when additional humidity was provided during the holding period. METHODS AND PROCEDURE The eggs used in this experiment were produced by S. C. White Leghorn hens and S. C. Rhode Island Red pullets. The Leghorn hens were hatched in September 1939 and came into production in February 1940. They had been in continuous production from that date. The R. 1. Red pullets had been in production for approximately 6 months. No effort was made to segregate the eggs from these two breeds of chickens during either the holding or hatching period. Hence all data presented cover results obtained from eggs of both breeds. The R. I. Red pullets were confined to a single pen, while the Leghorn hens were in five separate pens and at the time were being used in nutritional experiments. The Leghorn males used were purchased from an Oregon poultryman. The R. I. Red males were carried over from the previous hatching season and were the sires of the pullets to which they were mated in this work. To minimize the influence of heredity upon hatchability of the various lots of eggs, the Leghorn males were paired and moved every other day from pen to pen. Eggs gathered from each of the six pens were divided as evenly as possible into four lots. The eggs were gathered a minimum of three times a day and taken to a well-insulated but unhumidified egg room for holding until evening, at which time the various lots of eggs were made up and weighed to the closest hundredth of a pound. The lots were then moved to their respective holding quarters.

5 STATION TECHNICAL BULLETIN 2 Three of the quarters used were comparable to those commonly employed throughout the country for storing hatching eggs prior to incubation. Lot 1 eggs were placed in a standard egg case and held in an open feed room located at one end of an O.S.C.-type laying house (Figure 1). Lot 2 eggs were handled as those in Lot 1 except they were held in an insulated egg room located on the first floor of a two-story laying house (Figure 2). The ventilators in Figure 1. Eggs in Lot I. this room were left open at night and were closed during the day. Lot 3 eggs were cooled for 24 hours on a wire tray located in an insulated, egg-storage room equipped with a cooler and humidifier, which is described in Oregon State College Station Circular 138 (1940), and then were cased and held under the same environmental conditions (Figures 3 and 4). Eggs in Lot 4 were held on wire trays in a specially constructed egg cabinet (Figure 5). This cabinet was of double-wall construction insulated with shavings and equipped with a reostatically controlled fan and radiator through which cold water could be circulated at will. This equipment was constructed to control temperature on a group of eggs without the presence of a high relative humidity. The temperature within this cabinet was maintained at as near as possible the same level as that prevailing in the humidified egg room. All eggs were turned daily throughout the holding period.

Figure 2. Eggs in Lot 2. Figure 3. Eggs being cooled on wire tray 7

00 STATION TECHNICAL BULLETIN 2 Temperature and humidity readings were recorded in each of the four holding quarters at 9:00 a.m., 4:00 p.m. and between 10:00 and 11:00 p.m. Maximum and minimum temperature readings were taken at 4:00 p.m. Settings were made on the fifteenth day from the date the first eggs of each hatch were gathered. Figure 4. Eggs in Lot 3. Five savings of eggs were used in the experiment. The first hatch consisted of eggs saved for 7 consecutive days. In this hatch the oldest eggs were 14 days old when set and the youngest 7 days old. In the remaining four groups, eggs were gathered for 10 consecutive days, thus making the oldest eggs 14 days old when set and the youngest only 4 days old. All eggs were incubated in an electric, forced-draft, cabinet incubator. Each day's eggs (sublots) from all four lots were incubated on the same tray.

PREINCUBATION HUMIDITY EFFECTS ON EGG HATCHABILITY 9 During this period the eggs were turned daily at 3 hour intervals, commencing at 7:00 a.m. and ending at 10:00 p.m. On the eighteenth day of incubation all sublots of eggs were again weighed and weight losses for the incubation period computed. Eggs were individually candled and those with live embryos transferred to pedigree trays in a separate hatcher. Each day's eggs were hatched Figure 5. Eggs in Lot 4.

10 STATION TECHNICAL BULLETIN 2 on the sane tray. Unfortunately the eggs candled out and recorded as infertile were not broken out and checked at least macroscopically for infertility. The possible effect of such an error will be brought out later. In the procedure followed all eggs received the same treatment during the incubation and hatching periods. Chicks obtained were individually handled at hatching time for physical defects and grouped into three grades. Those that were well finished with navels healed and moving about normally and freely were considered No. chicks and are listed as salable chicks in the following tables. The electricity was off for varying periods of time on three of the sets. The only set noticeably- affected, however, was No. 2. In this case the electricity was off during the eighteenth day of incubation for 11.5 hours. DISCUSSION Tables 1, 2, 3, 4, and 5 show the more pertinent facts obtained in this study. Table 6 is a composite table of totals and averages of the first five tables. Figure., 6, 7, 8, 9, and 10 give the reader a comprehensive insight into the average relative humidity fluctuations and daily maximum temperatures during the five holding periods in the four different holding quarters. The minimum temperatures are not shown because the lowest temperature recorded in any one of the quarters during the entire period covered in this paper was 40 F. This temperature is not considered injurious to eggs being held for incubation. From an experimental standpoint it is unfortunate that the outside maximum temperatures were not greater, as none of the lots of eggs was subjected lc temperature ranges that would he considered particularly damaging to eggs held for incubation. It is true that all lots in the last four hatches were exposed to temperatures above the physiological zero for eggs, but these represent maximum temperatures reached each day rather than averages. It is quite possible that these maximum temperatures were reached and held for only short periods of time. Hence the internal contents of the eggs and more specifically the genes did not have time enough to assume the new environmental temperature and therefore were not adversely affected. This possibility is strongly indicated in Hatch V (Figure 10). It will be noted that with the exception of 3 days the maximum daily temperatures recorded for the holding quarters of Lot 4 eggs were 70 F. or above, and for 2 of the 3 excepted days the maximum temperature was 69 F., which is still above the physiological zero. The other three lots of eggs were not subjected to maximum temperatures above 67 F. until the last 3 days of the holding period when the temperature reached 69 F. on June 28 and 71 F. on June 30. Yet, when the hatchability of eggs in Lot 1 is compared with that of Lots 2 or 4 the advantage is in favor of the former. In all instances there is a good relationship between the relative humidity curves and the actual per cent weight losses for the respective lots during the holding periods. On the other hand, there is no significant difference in per cent weight losses between lots during the incubation periods. This is as it should be since all corresponding sublots were uniformly treated in the incubator. From a careful study of the tables and curves one is forced to conclude that if there are any significant differences in hatchability between treatments (lots) they will be due solely to environmental humidity during the holding periods. As mentioned previously, the apparent fertility in a large majority of the sublots was somewhat higher for those eggs randomly placed in Lot 3. For

11 Table 1 HATCH I Number of eggs gathered Time eggs were held' Loss of original weight I Date eggs were gathered Lot :1 Lot 2 Lot 3 Lot 4 Lot I 'Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3' Lot 4 Days Days Days Days Per Per Per Per cent cent cent cent April 1, 1941 35 35 35 35 14 14 14-14 0.81 April 2, 1941... 1.12... -- -... 0.00 0.93 36 36 37 36 1.3 13 13 13 0.95 April 3, 1941 0.95 0.40 1.24 33 33 33 33 12 12 12 12 0.38 April 4, 1941......---- ----- --... 2.57 0.65 0.64....-... 1 1. 11...-..-...... 38 38 37 38 11 1.00 April 1.11 5, 1941 0.13 0.64..._... 35 34 34 34 10 10 10 10 0.55...... 0.00 April 6, 1941 0.00 :-...... 1.79 33 34 33 33.9 9 9. J 0.74 April 7, 1941......:..._-----... 0.84 0.16 0.61 35 35 34 34 8 8 s s 0.70 0.69 0.29 0.45 Totals and averages...-......---- -------..._. 245 245 2 43 2443 I... _ 0.74 1.04 0.23 0.9I Table 1 HATCH I-Continued Weight loss during Number of apparent Per cent salable chicks Number of eggs set incubation fertile eggs to apparent fertile eggs Date eggs were gathered Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot I Lot 2 Lot3 Lot 4 Lo. t. Lot 2 Lot 3 Lot 4 Per Per Per Per cent cent cent cent April 1, 1941... 35 34 35 35 12.37 11.57 11.16 1 2.57 24 24 25 April 26 2, 1941 58.8... 66 7 36 36 64 0 35 69 2 35 11.98 12.40 12.14 1 2.35 21 22 2I 26 April 3, 1941 52.4 59 1... 65 2 33 33 33 33 61 5 13.39 12.73 12.19 1 258 21 19 22 18 April 81.0 4, 1941... 73 7 38 38 63 7 37 61 1 38 12.07 13.67 12.76 1 2.27 23 25 25 24 73.9 April 5, 1941... 800 720 35 34 958 34 34 12.40 12.32 12.58 1 1.85 26 22 23 April 26 73.1 77 3 78 3 76 9 April 6, 1941 +k 7, 1941...... 33 34 33 32 12.40 35 35 34 34 13.20 12.27 14.96 12.26 1.3.19 1 3.16 20 24 21 13 tin-)) 708 667 652 1 3.58 23 20 24 25` 78.3 70 0 83-3 80 0 Totals and averages...... 245 244 241 241 12 53 12 88 12 33 1 2:61 1.58 156 163 1 16& 70.9 7L2 70.6 73.2 " Includes day eggs were gathered ti t

ay" Table 2. HATCH II May 3, 1941......... May 4, 1941......... _...--- May 5, 1941...---------- _.. May 6, 1941... -- ---...... May 7, 1941...... fay 8, 1941... -... May 9, 1941...... May 10, 1911...._...-... May 11, 1941... -......-------- May 12, 1941......----......---- Number of eggs gathered Time eggs were held* Loss of original weight Date eggs were gathered Lot I Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot I Lot 2 Lot 3 Lot 4 Totals and averages.......... Days Days Days Days Per Per Per Per cent cent cent cent 30 30 30 30 14 14 14 14 1.30 1.42 0.48 2.65 30 30 30 30 13 13 13 13 1.45 1.26 0.46 0.95 30 30 30 30 12 12 12 12 1.27 0.97 0.31 1.12 28 28 28 28 11 11 11 11 1.21 0.00 0.36 0.85 32 32 32 32 10 10 10 10 1.19 1.21 0.32 0.90 27 27 27 27 9 9 9 9 1.22 0.89 0.17 0.87 29 30 30 30 8 8 8 8 1.31 0.80 0.51 0.64 30 30 30 30 7 7 7 7 0.94 1.00 0.34 0.62 27 27 27 27 6 6 6 6 1.66 0.75 0.17 0.53 27 27 27 27 5 5 5 5 0.55 0.69 0.00 0.33 290 291 291 291 1.21 0.91 0 32 0.96 Table 2 HATCH II-Continued Weight loss during Number of apparent Per cent salable chicks to Number of eggs set incubation fertile eggs apparent fertile eggs Date eggs were gathered Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot I Lot 2 Lot 3 Lot 4 Per Per Per Per cent cent cent cent May 3, 1941------------------ ----- 30 30 30 29 12.50 12.59 12.16 12.69 25 23 23 22 44.0 47.8 39.1 31.8 46 2 42 9 May 4, 1941 ------------------------ 30 30 30 30 11.90 12.89 12.84 12.67 20 25 26 21 70.0 64.0.. May 5, 1941... 30 30 30 30 12.26 11.75 12.38 14.12 22 24 23 22 59.1 58.3 56.5 45.5 May 6, 1941.... 27 28 28 28 10.73 12.51 11.84 13.51 24 24 24 19 45.8 62.5 58.3 57.9 May 7, 1941 32 29 32 31 12.67 13.79 13.14 12.35 26 24 28 27 57.7 70.8 57.1 66.7 May 8, 1941... 27 27 27 27 12.43 11.75 11.45 13.18 22 23 23 22 59 1 65.2 65.2 50.0 May 9, 1941... 28 30 30 30 13.08 13.25 11.38 13.25 23 27 27 26 65.2 51.9 70.4 38.5 May 10 1941... 30 30 30 30 12.62 13.37 12.16 11.91 27 25 27 26 63.0 52.0 66.7 76.9, May 11, 1941... 27 27 27 27 9.21 12.56 12.61 12.61 22 22 24 22 68.2 77.3 79.2 59.1 May 12, 1941...... 27 27 27 26 12.50 11.29 12.64 12.84 23 23 25 23 60.9 56.5 88.0 78.3 Totals and averages - 288 288 291 288 12 02 12 60 12 27 12 91 234 240 250 230 59 0 60 4 62.8 55 2 * Includes day eggs were gathered.

Table 3. HATCH III Number of eggs gathered Time eggs were held" Loss of original weight Date eggs were gathered Lot I Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Days Days Days Days Per Per Per Per cent cent cent cent May 19, 1941...... 31 31 31 31 14 14 14 14 1.83 1.39 0.60 1.71 May 20, 1941... --......-----.. 27 27 27 27 13 13 13 13 1.54 1.46 0.71 1.82 May 21, 1941... ------------------..._... 26 26 26 26 12 12 12 12 1.44 1. 30 0.35 1. 83 May 22, 1941...... 29 29 29 29 11 11 11 11 1.42 1.29 0.50 1.33 May 23, 1941... ----- -------------------- 26 26 25 26 10 10 10 10 1.29 1.27 0.41 1.14 May 24, 1941 28 28 29 28 9 9 9 9 0.85 1.04 0.19 0.86 May 25, 1941...... 26 26 26 26 9 8 8 8 0. 73 0. 73 0.00 0. 91 May 26, 1941 --......---...-----... -----... 27 27 27 27 7 7 7 7 0.71 1.04 0.35 0.89 May 27, 1941......... 27 27 27 27 6 6 6 6 1.23 0.73 0.34 0.86 May 28, 1941... -... ---... 29 29 29 29 5 5 5 5 0.64 0.65 0.16 0.82 'Totals and averages... _...w»... 276..76 276 276.--. 1.18 1.09 0.36 1.22 Table 3. HATCH III-Continued Date eggs were gathered Number of eggs set Lot I I Lot 2 Weight loss during incubation Per Per Per Per cent cent cent cent May 19, 194 1... 31 31 31 28 12.76 10.92 11.37 12.60 25-25 25 22 May 20, 1941....... 27 27 27 27 11.21 11.66 11.75 12.88 22 25 24 23 May 21, 194... 26 26 26 26 10.99 11.96 10.81 12.99 23 20 23 23 May 22, 1941 ------ -- ------------ 29 29 29 29 11.63 11.76 12.52 11.72 21 25 23 24 May 23, 194 1...... 26 26 25 26 12.62 10.65 11.45 12.10-13 23 23 24 May 24, 194... 1 28 28 28 28 10.91 11.51 11.26 11.83 24 23 24 24 May 25, 194 1...... 26 26 26 26 10.89 11.80 11.43 11.11 21 24 24 21 May 26, 194 1......------ 27 26 27 27 11.46 12.21 11.84 11.74 21 21 24 23 May 27, 1941.... 27 27 27 27 11.88 11.96 12.43 11.36 22 25 25 25 May 28, 194 1...... 29 29 29 29 11.71 11.18 10.96 11.84 27 24 25 23 Totals and averages... 276 275 275 273 11.62 11.55 11.59 1 12.01 1229 2 ' 240 232 Includes day eggs were gathered Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Number of apparent fertile eggs Lot 3 Lot 4 Per cent salable chicks to apparent fertile eggs Lot I 68.0 50.0 73.9 61.9 78.3 87.5 76.2 52.4 63.6 81.5 69.9 Lot 2 52.0 64.0 60.0 72.0 65.2 82.6 79.2 71.4 80.0 87.5 71.5 Lot 3 Tot 4 56.0 70.8 82.6 73.9 73.9 66.7 70.8 91.7 64.0 92.0 74.2 54.6 52.2 78.3 70.8 79.2 87.5 85.7 78.3 72.0 65.2 72.4

Table 4. HATCH IV une June June June June June June June June June, 4, 5, 6, 7, 8, 9, 10, 11, 12, 941 1941 1941 1941 1941 1941 1941 1941 1941 1941 Date eggs were gathered Lot 1 Lot 2............................................_...------...--------....... _...----...-----......... -- --......... Number of eggs gathered Time eggs were held* Loss of original weight 30 30 24 24 26 26 26 27 27 27 29 29 24 24 27 27 25 25 27 27 Lot 3 Lot 4 30 30 24 22 26 26 27 27 27 27 29 29 24 24 27 27 25 25 27 27 Totals and averages 265 266 266 264... 1.46 1 26 0 42 1.31 Lot 1 Days 14 13 12 11 10 9 8 7 6 5 Lot 2 Days 14 13 12 11 10 9 8 7 6 5 Lot 3 Days 14 13 12 11 10 9 8 7 6 5 Lot 4 Days 14 13 12 11 10 9 8 7 6 5 Lot I Per cent 1.91 2.22 1.44 1.49 1.53 1.63 1.17 1.23 1.31 0.70 Lot 2 Per cent 1.90 1.61 1.65 1.19 1.26 1.17 0.95 1.05 0.76 1.04 Lot 3 Per cent 0.48 0.80 0.57 0.34 0.34 0.50 0.42 0.34 0.18 0.20 Lot 4 Per cent 1.58 1.83 1.60 1.41 1.42 1.32 1.18 1.04 0.76 0.88 Table 4. HATCH IV-Continued Number of eggs set Weight loss during incubation Number of apparent fertile eggs Per cent salable chicks to apparent fertile eggs Date eggs were gathered Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Per Per Per Per cent cent cent cent June 3, 1941... 30 30 30 30 7.31 14.42 11.80 11.65 27 24 28 25 40.7 62.5 85.7 56.0 June 4, 1941... 23 24 24 24 11.91 11.62 11.70 11.67 21 19 19 18 52.4 84.2 79.0 66.7 June 5, 1941... 26 26 26 26 10.25 11.54 11.57 12.89 24 21 22 20 79.2 66.7 86.4 75.0 June 6, 1941... 26 27 27 26 11.18 10.96 11.37 11.31 24 20 24 22 79.2 70.0 87.5 72.7 June 7, 1941... 27 27 26 27 11.09 11.29 11.67 10.62 21 24 22 23 66.7 91.7 81.8 60.9 June 8, 1941... 28 29 29 29 10.98 11.43 11.42 11.64 25 26 25 24 68.0 76.9 84.0 75.0 June 9, 1941......... 24 23 24 24 11.57 10.66 11.85 10.70 21 18 23 18 57.1 66.7 78.3 72.2 June 10, 1941....... 27 26 27 27 10.32 11.92 11.25 11.20 22 23 24 24 77.3 87.0 83.3 87.5 June 11, 1941... 24 25 25 25 10.38 11.98 11.98 10.60 18 21 21 19 77.8 61.9 71.4 84.2 une 12, 1941... 26 27 27 25 10.99 11.39 11.70 10.38 19 22 22 20 63.2 77.3 86.4 90.0 Totals and averages... 261 264 265 263 10 53 11 75 11 62 11 28 222 218 230 213 74 8 82 6 73.7 " Includes day eggs were gathered

... Number of eggs gathered Time eggs were held' Loss of original weight Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 1 1....---_.--------- _-----------. 1 1 -.....------------------------- ----- -_-...--... 1. 1 1 1 1...-------------- _..._.--... --... 1 1._..._...-......--.-_-. I 1 I._..-_------------ ---------..,..._..._...-._...... Totals- and averages......_.........:.::...., I II June 17, 1941.._... June IS. 1941..._.._..._... 19, 1941...... Tune 20, 1941...,June 21, 1941... June 22, 1941._....- June 23, 1941... June 24, 1941...... june 25, 1941... )uric 26, 1941... Totals and averages... 3

Fable 6. COMPOSITE TABLE OF TOTALS AND AVERAGES Average loss of original Number of eggs gathered Average weight loss during weight while held Number of eggs set incubation Hatch number Lot 1 Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 Lot I Lot 2 Lot 3 Lot 4 Lot 1 Lot 2 Lot 3 Lot 4 1 Per Per Per Per Per Per Per Per cent cent cent cent cent cent cent cent I... 245 245 243 243 0.74 1.04 0.23 0.91 II------------------------------------------ 245 244 241 290 241 291 291 12.53 12.88 12.33 12.61 291 1.21 0.91 0.32 II----------------------------------------- 0.96 288 288 291 276 276 288 12.02 276 12.60 12.27 12.91 276 1.18 1.09 0.36 1.22 276 275 275 273 IV ----------------------- ---------- -... 265 266 11.62 266 11.55 11.59 12.01 264 1.46 1.26 0.42 1.31 261 V------------------------------------------ 264 265 241 241 263 10.53 241 11.75 11.62 11.2k 241 1.21 1.05 0.24 0.96 241 240 241 239 10.91 9.75 11.39 10.84 Totals and averages 1,317 1,319 1,317 1,315 1 17 1.07 0 32 1.07 1,311 1,311 1,313 1,304 11.53 11.73 11.84 11.9( Table 6 COMPOSITE TABLE OF TOTALS AND AVERAGES-Continued......... II... --- ----...--------...-- --... III--. -- -... -----... -----... iv---...... ----------...._ V......---... Totals and averages Hatch number..............---...--- Lot I 158 2:14 229 222 199 1,042 Number of apparent Per cent salable chicks Per cent salable chicks to fertile eggs to apparent fertile eggs total eggs set Lot 2 156 240 235 218 194 1,043 Lot 3 162 250 240 230 197 1,080 Lot 4 148 iu 23`1 213 202 1,045 Lot I Lot 2 70.9 71.2 59.0 60.4 69.9 71.5 65.8 74.8 78.9 76.8 68.7 70.8 Lot 3 70.6 62.8 7.1.2 82.6 82.2 74.7 Lot 4 73.2 55.2 72.4 73.7 73.3 69.2 Lotl 45.7 47.9 58.0 55.9 65.2 54.4 Lot 2 66.1 Lot 3 45.5 47.7 51.1 50.4 54.0 44.1 61.1 64.7 61.6 61.7 71.7 59.9 62.1 67.2 61.9 61.1 Lot 4 55.4

1 I PREINCUBATION HUMIDITY EFFECTS ON EGG HATCHABILITY 17 K all sublots combined the apparent fertility was 79.9 per cent. To test for possible treatment effect on apparent fertility the X2 test for homogeneity was applied to the data (10). If no treatment effect on apparent fertility existed the relative proportions in the two classes (apparent fertility and apparent infertility) should be 9the same for each lot except for sampling fluctuations. Summary of this test is given in Table 7. 4 too i AVERAGE RELATIVE HUMIDITY IF 90 0. n 5 s t 8 9 J ri DATE (APRIL) i. 1O. 12 13 MAXIMUM TEMPERATURE 100 90 0 0,I 40 DATE 8 9 I 0 A? 13 14 (APRIL) LOT 1 LOl 2 LOT 3 ------- LOT 4 HUMO01TY ANO TEMPERA'TORE CURVES FOR OATCN 1 I

1$ STATION TECHNICAL BULLETIN 2 The total for all lots in the five hatches does not give too good a fit to expectancy since a somewhat low value for P exists, suggesting a possible treatment effect. By omitting Lot 3 a much lower value of X2 and a much higher value of P are obtained showing that without including Lot 3 a very good fit to expectancy of apparent fertility exists in Lots 1, 2, and 4. Homogeneity tends to be upset by including Lot 3 and tends to be restored -by omitting AVERAGE RELATIVE HUMIDITY 100 7M' 15 s 7 9 10 II 12 13 14 15 DATE (MAY) MAXIMUM TEMPERATURE loo 0 80 70 W 60 I- 50 4 5 LOT LOT LOT 3 LOT 4 I 7 8 9 :0 li 12 DATE (MAY) 16 F10 T NUI DITT wd TEYREA tijre CURVES for MATCH 1.

ti PREINCUBATION HUMIDITY EFFECTS ON EGG HATCHABILITY 19 Lot 3. Owing to the tendency of treatment effect (Lot 3) further analysis is suggested. Hence an analysis of variance and comparisons of the means of the apparent fertilities were made. This analysis is presented and summarized in Tables 8 and 9. AVERAGE RELATIVE HUMIDITY 1Oo 90 Z 80 w 5-70 CL 60 z 50 23 24 25 26 27 28 29 30 DATE (MAY-JUNE) 00 90 60 MAXIMUM TEMPERATURE LL 70 60 F, 50 i 40 20 21 22 23 24 25 26 27 28 29 30 DATE (MAY-JUNE) bl LOT I LOT 2 LOT 3 LOT 4 FIG HUMIDITY AND CU tcd TIIRC CURVES FOR WATCH I I

AVERAGE -RELATIVE HUMIDITY 00 90 z W u 0. 70 60 SO 5 6 8 9 10 11 12 13 14.16` 16 DATE (JUNE) MAXIMUM TEMPERATURE loo 90 Flp 60 40 S 6 9 10 1 12 13 14 15 16 DA!E (JUNE) LOT LOT 2 LOT 3 LO' I EID y NUYIDTY L)&D 'EYi'EI LIU9C CURVES E0R rif Dr IV 20

--- AVERAGE RELATIVE HUMIDITY t I TEMPERATURE PERCENT chi Is 19 20 21 MAXIMUM TEMPERATURE.j 29 40 i Is 19 20 21 22 23 24 20 26 27 28 29 30 DATE (JUNE) CURVES MATCH 21

Lot I...... 2 ------------------------ 3... 4... Total... Total omitting lot 3... cn C euweu-w 1 oa,10 * rrrr r" oo Q rrrr m m.- Cn-400`1 '>,265 I 951 1 to,w on, ryb [0 0000 amaa 010000,210 3,130 c91 rrrr N N C) '0 ry W.ry 275 276 237 270 1,058 821 r w [ 00 H Tl rrr X to. R. N N or, r Nwtv m'n a -.,,. NmW Ma w ti 1051.6 263.4 b b II 0WtO 11 V] 0)0)0) W rv W (C -J N to 3 ng a 00 owoo [000101 (: 000010 -.l 0)--0Or v a NO0a0) CD Q)eD0 00.25 /.a, CC gs v Aa a AAAAAWWC..0> W w cw w w0nn N N N N N NN t+ u t r.r VOvCAW Ni-+Op ODVOtnAWNt+O000VOcnAwN+O.D 000 Qv.AwNt+O000V OtnAWNu Sum... -,W CO v m llmm 00..1 CO 0000 N--1 m 00 m--l CD 00001000 m-.1m 0000) m 0000000<O mm mm mmq)t 1000000) o wen mnoaoro ON m wen r74 coy NtO r OwrNOCn m w oor Oen F-oNrrmwmwcnoaowmm 0 00 WOF+C)T.l l to coax oa CnNNWea O.+oC-aa-1NNaaaa O>r w+orc N00W O>c.9 1 C)W Cn Q>W 01 00 0 wonr00-.1o 0ooooooenoorrooocooorrnroomencooooaoocneow-0wrreowpw-a N > a Ww00000000 0000010)Q)t000000)00 1ra0)r000Den000000000 OIr OW-oa1Drt000rcD» 0) X10000 --10000--l-l00000000-.lmmNm--00000000000000000 NtOmmm medmmmm m--l Cn l O)0)Cn 0)N 00 OWtn 00 W:P )rn00 F+.P 00 0000. OCDOWN0 N[0 mtl)o)noucr WOCn NCnO WO)NOatn lr0 V en 00000lVOT000 'OaOa000000 Nr 0-a00-.1Wrapotoen00>aCOr-I-IOWOIr00-o-o CnrCn w 00 b 00 N 0000 1N0000t0 10000mme000000 00 1e000CD00t000C0 100m000O00COCOmmml001.10000)0)1 0 0) Cn0W0TOr00000ra00Cn0)a00a COWOW00NC t,000000tco000oet -.100000OC>C.1 0enr D r OW0boco- 0Coraaem00NTm0)r0NCn00W-JOWa000Cn0OOre -)ooo 00oo Cno-1a m 00000000--1wr10000COWr NCON--1wr0000rr0P.&000 T0000OOC0Or--1-1N10afnv-lrw W w oroma mf om omop rocmit mpw-;oop Cml o cmn twv-,tmv' w,cmn oo,omornmnwocnww w 0) Cn 00000000000000000000 1 I-+00000000011-+ Wlaren)Pa00)a N00 w 00000ma0-`VCNN 0 -.0 W H t0000000000tvn00r00c0 300000.0)000. O00000000000.-10 000000 rn w to wwwcuwwwwwwwwwcwwcvwwweawwwwww[w0wwww0wenwwtnt0to[nne0 rnnwnwr aaarr aooawwwt0aa0nwaw0)naan0n W0na0Wt000r00 0001a0n0O 0) Wa0000)OWOripoco-0)o-o )00-lao 00N0)0DroNm0rWOmwmmwTNOCTW-1t Coa r anrac0--1 0 00 0 0e0NCn00a000 001b00rtVNOwrCnaw000w0)rw0 0010-.1r Oaa00 00 wn0)wwmar ltoao WCOtO0otoao000nw0)- ooco000tvwworar-lw-100-jnnfnaa00 JO --1 O0mm00m100000NV0omm000o0000mm0O00omto0om00 00 00 00 00 00 00 00 0X1-.1 X100-.1000-1 0 mrnnrnvicp Cl 0)totOTa0)aaar 0)01 1Wo)apoo1 X70 1WN0WaNC10)m0)0)OaPar :D ONQO)tDaNµeD r00 00QOWWrCnm WO jcnormw0110 000)0 mor-10)--1 L00)O0N i en enu um wam i mab+enau lawmwe0 wenawawammmumro 22

PREINCUBATION HUMIDITY EFFECTS ON EGG HATCHABILITY 23 Table 9. ANALYSIS OF VARIANCE OF APPARENT FERTILITY OF 188 SUBLOTS OF EGGS Source of variation Total... Within sublots......... -... ---... Treatments or lots... Discrepance (error)... Degrees of freedom Sum of squares Mean square 187 12,618.91 46 9,167.06 199.27* 3 233.69 77.891 138 3,218.16 23.32 Highly significant. Exceeds F value for.01 level. 199.27 F = or 8.5 F value (d.f., 46 and 138) for.01 level is approximately 1.70. 23.32 Exceeds F value for.05 level. 77.89 t Significant. F = -- or 3.49 F value (d.f., 3 and 138) for.05 level is approximately 2.68; 23.32 for.01 level is approximately 3.93. Since a significant treatment effect is shown, lot comparisons may be made as follows : (3,896.18-3,770.89) 2 167.02 = 167.02 F = or 7.16* 2(47) 23.32 (3,896.18-3,769.54) 2 170.50 = 170.50 F=r or 7.31* 2(47) 23.32 (3,896.18-3,789.57) 8 120.89 = 120.89 F= or 5.18f 2(47) 23.32 (3,789.57-3,770.89)' 3.71 3.71 F = or 0.159 2(47) 23.32 (3,789.57-3,769.54) 2 4.27 4.27 F = or 0.183 2(47) 23.32 (3,770.89-3,769.54) 2 0.0194 = 0.0194 F = or 0.0083 2(47) 23.32 It is thus shown that apparent fertility is influenced by treatment. Highly significant differences exist in favor of Lot 3 when compared with Lots I or 2, and a significant difference for Lot 3 is demonstrated over Lot 4. No significant differences are demonstrated in comparisons of the other three lots as indicated by the low F value. This substantiates the results obtained with the X2 test for homogeneity. * Highly significant. Exceeds F value for.01 level. F value (d.f., 1 and 138) for.01 level = 6.825. 1 Significant. Exceeds F value for.05 level. F value (d.f., 1 and 138) for.05 level = 3.915.

N N, 24 STATION TECHNICAL BULLETIN 2 The analysis of variance and comparisons of the hatchability of apparent fertile eggs in each hatch (Table 6) did not consistently show a significant treatment effect in favor of any one lot. In one hatch (Hatch IV), however, a highly significant difference between treatments was observed. A highly significant difference in favor of Lot 3 over Lot 1 and an approach to significance in favor of Lot 3 over Lots 2 and 4 were observed. In Hatch V, even though no significant variation was shown by analysis of variance, there was a significant difference in favor of Lot 3 over Lot 4 in lot comparisons. There were other cases where significant differences were approached in lot comparisons. Owing to some instances of significant treatment effect and tendencies towards significant treatment effect, further analyses are again suggested. Composite analyses of variance and comparisons were made as shown in Tables 10 and 11. Table 10. AVERAGE DAILY PER CENT HATCH of APPARENT FERTILE EGGS I 7 r Sublots Lot I Lot 3 Lot 4 Mean 1... 58.3 66.7 64 69.2 258.2 64.5 2... 52.4 59.1 65 61.5 238.2 59.5 3... 81.0 73.7 63 61.1 279.5 69.9 4... 73.9 80.0 72 95.8 321.7 80.4 5... 73.1 77.3 78 76.9 305.6 76.4 6... 80.0 70.8 66 7 65.2 282.7 70.7 7... 78.3 70.0 83 3 80.0 311.6 77.9 8... 44.0 47.8 39 1 31.8 162.7 40.7 9... 70.0 64.0 46 2 42.9 223.1 55.8 10... 59.1 58.3 56 5 45.5 219.4 54.9 11... 45.8 62.5 58 3 57 9 224.5 56.1 12... 57.7 70.8 57 66.7 252.3 63.1 13... 59.1 65.2 65 50.0 239.5 59.8 14... 65.2 51.9 70 38.5 226.0 54.5 15... 63.0 52.0 66 76.9 258.6 64.6 16... 68.2 77.3 79 2 59.1 283.8 70.9 17 60.9 56 5 88 0 78.3 283.7 70.9 18... 68.0 52.0 56 54.6 230.6 57.6 19... 50.0 64.0 70 52.2 237.0 59.2 20... 73.9 60.0 82 78.3 294.8 73.7 21... 61.9 72.0 73 70.8 278.6 69.6 22... 78.3 65.2 73 79.2 296.6 74.1 23... 87.5 82.6 66 87.5 324.3 81.1 24... 76.2 79.2 70 85.7 311.9 77.9 25... 52.4 71.4 91 78.3 293.8 73.5 26... 63.6 80.0 64 72.0 279.6 69.9 27... 81.5 87.5 92 65.2 326.2 81.5 28... 40.7 62 5 85 56.0 244.9 61 2 29... 52.4 84.2 79 66.7 282.3 70.6 30... 79.2 66.7 86 75.0 307.3 76.8 31... 79.2 70.0 87 72.7 309.4 77.4 32... 66.7 91.7 81 60.9 301.1 75.3 33... 68.0 76.9 84. 75.0 303.9 75.9 34... 57.1 66.7 78 72.2 274.3 68.6 35 77.3 87.0 83 87.5 335.1 83.8 36 77.8 61.9 71 84 2 295.3 73.8 37... 63.2 77.3 86 90.0 316.9 79.2 38... 78.3 66.7 82 57.1 284.7 71.2 39... 76.2 73.7 79 56.5 285.4 71.3 40 80 0 70.6 75 72.2 297 8 74.5 41... 68.8 61.1 88 82.4 301 2 75.3 42... 81.0 90.9 85 81.8 339.4 84.9 43... 90.9 68.4 70 83.3 312.6 78.1 44... 79.0 94.4 94. 81.0 348 8 87.2 1 t r ONlO C9 _ '-INh! Oi/WCttoD t00t0 a.o00 MOirt T:D O-O L;[-OW0040....... :.... O t-. 45... 73.7 78.3 80. 58.8 290.8 72.7 46 66.7 90 0 90 73.7 320 4 80.1 47... 90.0 70.6 77 85.0 323.4 80.8 Sum... 3,229.5 3,327.4 3,509. 3,253.1 13,319.5 68.7 70.8 7 69.2 70. 7 nv YI

PREINCUBATION HUMIDITY EFFECTS ON EGG HATCHABILITY 25 In lot comparisons and in analysis of variance of the composite data hatchability of apparent fertile eggs is significantly affected by treatment. Highly significant differences in favor of Lot 3 are demonstrated over Lots 1 and 4, and a close approach to significance is shown for Lot 3 over Lot 2. No significant differences are demonstrated in comparison of the other three lots. Hatchability of apparently fertile eggs was demonstrated to be significantly affected by treatment previous to incubation; similarly, apparent fertility was demonstrated to be significantly influenced by treatment prior to incubation. The treatment of Lot 3 was significantly more favorable for apparent fertility and was likewise most favorable for hatchability of apparently fertile eggs. The test of treatment effect on hatchability of all eggs incubated should, therefore, be expected to show as large or even larger F value (i.e., higher signifia Table 11. ANALYSIS OF VARIANCE OF HATCHABILITY OF APPARENT FERTILE EGGS Sources of variation Total...... Within sublots...... _... Treatments or lots............ Discrepance (error)... Highly significant. Exceeds F value for.01 level. F value for.01 level=1.70. F in this case=3.96. 1 Significant. Exceeds F value for.05 level. F value for.05 level=2.67. F in this case=3.78. Degrees of Sum of Mean freedom squares square 187 30,097.79 46 16,502.29 358.74* 3 1,020.55 340.18f 138 12,574.95 90.47 Since a significant treatment effect is shown, lot comparisons may be made as follows : (3,327.4-3,229.5) 2 101.96 = 101.96 F = or 1.127 2(47) 90.47 (3,327.4-3,253.1)' 58.57 = 58.57 F = or 0.647 2(47) 90.47 (3,253.1-3,229.5) I 5.925 5.925 F =' or 0.06549 2(47) 90.47 (3,509.5-3,327.4)2 = 352 77 2(47) F = 352.77 or 3 89-90.47.. (3,509.5-3,253.1)' 699.37 = 699.37 F = or 7.73* 2(47) 90.47 (3,509.5-3,229.5) 2 834.00 = 834.00 F = or 9.28* 2(47) 90.47 cance) than in case of hatchability of apparently fertile eggs. are shown in Tables 12 and 13. These analyses " Highly significant. Exceeds F value for.01 level. F value (d.f., 1 and 138) for.01 level = 6.825. 1 Approaches significance as this F value is just under the significant F value for.05 level. F value (d.f., 1 and 138) for.05 level = 3.915.

26 STATION TECHNICAL BULLETIN 2 Table 12. AVERAGE PER CENT HATCH OF ALL EGGS INCUBATED Hatch I Lot I I_... I I... III._._.. IV... Lot 2 Lot 3 Lot 4 Sum Mean Per cent Per cent Per cent Per cent Per cent Per cent 45.7 45.5 47.7 51.1 190.0 47.5 47.9 50.4 54.0 44.1 196.4 49.1 58.0 61.1 64.7 61.5 245.3 61.3 55.9 61.7 71.7 59.7 249.0 62.2 65.2 62.1 67.2 61.9 256.4 64.1 Sum 272.7 280.8 305.3 278.3 1,137.1 Mean.. 54.5 56.1 61.1 55.6 56.8 Table 13. ANALYSIS OF VARIANCE OF HATCHABILITY OF ALL EGGS INCUBATED Sources of variation Degrees of freedom Sum of squares Mean square Total... 19 1,247.93 Within hatches... 4 996.93 249.23* Treatments or lots... 3 124.76 41.58t Discrepance (error)... 12 126.24 10.52 Highly significant. Exceeds F value for.01 level. F value for.01 level=5.41. F in this case=23.6. t Significant. Exceeds F value for.05 level. F value for.05 level=3.49. F in this case=3.95. Since a significant treatment effect is shown, lot comparisons may be made as follows : (280.8-272.7) 6.08 6.08 F = or 0.578 2(5) 10.52 (280.8-278.3)' 0.625 = 0.625 F = or 0.0594 2(5) 10.52 (278.3-272.7)2 3.14 = 3.14 F = or 0.206 2(5) 1052 (305.3-280 8) 2 60.02 = 60.02 F = or 5.70t 2(5) 10.52 (305.3-278.3)' 72.9 = 72.9 F = or 6.931 2(5) 10.52 (305.3-272.7)2 106.28 = 106.28 F = or 10.10* 2(5) 10.52 As was expected, lot comparisons and analysis of variance of per cent hatchability of total eggs incubated show a highly significant difference in favor of Lot 3 over Lot 1, and a significant difference in favor of Lot 3 over Lots and 4. No significant differences are demonstrated between the other three lots. Highly significant. Exceeds F value for.01 level. F value (d.f., 1 and 12) for.01 level = 9.33. 1 Significant. Exceeds F value for.05 level. F value (d.f., 1 and 12) for.05 level = 4.75.

PREINCUBATION HUMIDITY EFFECTS ON EGG HATCHABILITY 27 CONCLUSIONS 1. Five successive hatches were studied involving a total of 5,239 S.C.W. Leghorn and S.C.R.I. Red eggs to determine the value, if any, of a comparatively high environmental humidity for eggs prior to incubation. 2. Temperature ranges prevailing during holding periods in this study cannot be considered a factor favorably or adversely affecting the hatchability of eggs in any lot in any one of the five hatches. 3. Evidence is presented to show that a comparatively high relative humidity (Lot 3) during the holding period makes possible the development of more embryos over a longer period of time than would otherwise be the case, thus affecting the apparent fertility as judged before the light of a commercial candling machine. 4. The presence of a comparatively high relative humidity during the holding periods of hatching eggs definitely increased hatchability whether measured by per cent hatch of apparently fertile eggs or by total eggs incubated. The nearest approach of any other treatment to that of Lot 3 was approximately 4 per cent when measured on the basis of apparently fertile eggs and 5 per cent on the basis of total eggs. 5. No attempt was made in this study to determine why eggs held under relatively high environmental humidity hatch better than eggs held under similar temperature conditions but under a lower relative humidity. REFERENCES 1. Bennion, N. L., and Price, F. E. Factors affecting egg quality. Oregon State College Agricultural Experiment Station Circular 138, 1940. 2. Bronkhorst, J. J., and Hall, G. O. A physical study of eggs from high and low hatching hens. Po. Sci. 14:112-115, 1935. 3. Godfrey, A. B. The effect of egg weight, quantity of total albumen per egg, and quantity of thick albumen per egg on hatchability. Po. Sci. 15:294-297, 1936. 4. Hall, G. 0., and Van Wagenen, A. The association of certain measures of interior egg quality with hatchability. Po. Sci. 15:501-506, 1936. 5. Jeffrey, F. P., and Darago, V. Effect of high humidity on egg quality during short holding periods. U. S. Egg and Po. Mag. 47:162-163, 191, 1941. Kennard, D. C., and Chamberlin, V. D. Market egg grades as affected by humidity of farm egg storage rooms. Ohio Agri. Exp. Sta. Bimonthly Bulletin 24, No. 199, 1940. 7. North, Mack O. 'High altitude incubation of eggs. U. S. Egg and Po. Mag. 47:158-159, 184, 1941. 8. Rudy, Walter J., and Marble, D. R. The interrelationship of physical measurements of eggs and their effects upon hatchability. Po. Sci. 18:354-358, 1939. 9. Scott, H. M. The effect of age and holding temperature on hatchability of turkey and chicken eggs. Po. Sci. 12 :49-54, 1933. 10. Snedecor, George W. Statistical methods. 3rd ed. Ames, The Iowa State College Press, 1940.