UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA The Effect of Current Interruption in Electrical Incubation L. W. TAYLOR, C. A. GUNNS, AND B. D. MOSES BULLETIN 550 JANUARY, 1933 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://www.archive.org/details/effectofcurrenti550tayl THE EFFECT OF CURRENT INTERRUPTION IN ELECTRICAL INCUBATION ^-^ L. W. TAYL0E,3 C. A. GUNNS,4 and B. D. MOSESs The successful operation of electrically heated incubators is com- monly supposed to depend upon a power supply which is either uninter- rupted or interrupted only at noncritical stages of chick development. While incubation literature reports some experimental work on chilling produced by failure in the source of heat, no work has been done on losses obtained under commercial conditions involving large numbers of carefully selected hatching eggs. The experiment reported herein was planned to determine some of the specific effects of prolonged failure in heat supply during incubation on the hatchability of hen's eggs. REVIEW OF LITERATURE Broca (1862) observed a case where the broody hen died on the 17th day of incubation. Approximately 15 hours after the death of the first hen a second was substituted. The chicks hatched between the 22nd and 26th days of incubation. He pointed out that when incubation was sus- pended not only did the rate of development become slower during the period of interruption but future development was retarded when nor- mal incubation temperatures were resumed. Kaestner (1895) cooled eggs at various stages of incubation to 21°, 10°, and 5° Centigrade (69.8°, 50°, and 41° Fahrenheit). He observed that the first period of sensitivity to cold appeared at approximately 36 hours of incubation ; a further period was found from the 6th to the 7th day. Embryos changed directly from incubation temperature to 5°C, (41° P) died in 1 to 2 hours. However, if placed for 2 hours under room temperatures before subjecting them to 5°C, (41°F) they were 1 Received for publication November 2, 1932. 2 This publication is the ninth of a series reporting results of investigations conducted by the California Agricultural Experiment Station in cooperation with the California Committee on the Relation of Electricity, to Agriculture. 3 Assistant Professor of Poultry Husbandry and Assistant Poultry Husbandman in the Experiment Station. 4 Technician in the Division of Poultry Husbandry. 5 Associate Professor of Agricultural Engineering and Associate Agricultural Engineer in the Experiment Station. 4 University of California — Experiment Station not killed. Apparently an abrupt change of temperature was more fatal to the embryo than a gradual change to the same degree of coldness. Kaestner also noted that eggs which had been cooled did not start development immediately on return to the incubator. Later, Kaestner (1896) reported that interruption of incubation and chilling to approximately 21 °C (69.8°F) caused death only after an extended period of time. Embryos so treated at the very beginning of incubation survived as long as three weeks at this temperature ; 6-day embryos survived to 72 hours ; 9-day stages to 48 hours ; and embryos of the second half of the incubation period, to 24 hours. While normal development was usually resumed when the eggs were replaced in the incubator and proper heat supplied, occasionally malformations were induced, particularly in 1 or 2-day embryos subjected to room tempera- ture for a period of 4 to 7 days. Lamson (1918) stated that the effect of subnormal temperatures was dependent on the vitality of the embryo, which varied in eggs from different hens. After 24 hours of incubation, embryos from strong stock were able to withstand 4 to 5 hours at 50°F ; at 10 to 12 days incubation this limit was increased to 15 hours ; but after 17 days incubation more than 6 hours chilling caused death before the hatching time. Bucciante (1931) stated that eggs incubated for several days and then placed in refrigeration at 0°C (32°F) for 1 or 2 hours did not resume development on return to the incubator. He further stated that similar results occurred when the eggs were left 12 hours at room tem- peratures varying from 15° to 20°C (59° to 68°F). By use of tissue- culture methods, however, it was found that most of the embryonic tissues retained the ability to develop for several days following death of the embryo. Also, different tissues were found to have different surviva- bilities. While tissues preserved at 0°C (32°F) survived better than at the range of 15° to 20° C (59° to 68° F) , the embryos survived longer at the higher temperatures. CONDITIONS OF THE EXPERIMENT During this experiment the electric incubator was operated in a heated basement room of the Poultry Research Laboratory at Berkeley. Room temperatures and minimal incubation temperatures were higher than are found in many hatcheries. Since 70 °F represents an ideal room temperature for incubation and is within the range commonly recom- mended by incubator manufacturers, temperatures were controlled as closely as possible to this degree. BuL. 550] Effect of Interrupted Incubation 5 A period of 12 hours current interruption was arbitrarily chosen as being probable under extreme conditions in rural localities. Records of several utility companies in California made available to the writers did not show any period of interruption in excess of this length of time. Eggs for this work were obtained from the purebred Single Comb White Leghorn flock of the Poultry Division, University of California. In each of the two years of the experiment approximately 250 pullets were mated with a full-brother family of cockerels. Hatching eggs pro- duced for this project were marked with band number of the dam and the date laid. Hatches were set from 7 to 10 days apart ; the maximum length of time between laying and beginning of incubation was 10 days. Each hatch consisted of two to three experimentally chilled lots, a check lot, and a supplementary lot. The eggs in the check and chilled lots were so distributed that the check lot had an egg from each pullet which had an egg in each chilled lot. The distribution of eggs from the various pullets was so rotated that all check and chilled lots had eggs averaging the same time of holding previous to incubation. The surplus eggs from each hen were placed in the supplementary lot. The check and supplementary lots received uninterrupted incubation at temperatures normal for the sectional type of incubator used, namely, 101°-102°F for the first week, 102°-103° for the second week, and 103°-104° for the final week of incubation. Temperature readings were taken with thermometers so placed that the center of the bulb was two inches above the bottom of the egg tray. Chilled lots were incubated under normal conditions except for 12 hours when chilled. A Newtown compartment type of incubator in which electric heating elements had been substituted for water pipes was used in this experiment. Ventilation and moisture supply were practically uniform for all lots. Trays were removed and exchanged daily from one compartment to another in regular rotation to minimize the efi'ect of possible uncon- trolled differences between compartments. During this exchange the eggs cooled slightly but not longer than 10 minutes at any stage of incubation. When the eggs were candled they were removed from incu- bation temperatures not longer than 15 minutes for each test. All lots were turned three times daily, except chilled lots when under current interruption. Recording thermometers were used to obtain continuous records of temperatures in the room, in the normal incubation compartments, and in the compartment where chilling was accomplished. Recording volt- meters were set in the circuits supplying the incubator to ascertain 6 University of California — Experiment Station whether the current had been interrupted at any time other than that provided for in the experiment. In all cases where chilling was effected, the tray of eggs was moved to the chilling compartment of the incubator and maintained at normal incubation temperatures for at least one hour. Then the current was turned off and the eggs remained undisturbed until a normal incubating temperature was restored after the 12-hour period of interruption. All infertiles and dead germs candled out were removed from the shell and the development, if any, compared to a normal standard for each day of incubation. In this way it was possible to segregate death at stages of development preceding the current interruption from death at later stages. Physiological abnormalties and malformations and mal- positions of the embryo were recorded as observed without the aid of the microscope. The hatches were grouped into three complete series. The first was run in the fall of 1929, the second in the winter of 1929-30, and the third in the fall of 1930. When it was found that poor hatchability in lots chilled on certain days of incubation was possibly significant, two special series including repetitions of chilling on these days were run in the winter of 1930-31. RESULTS Current Failures. — Only one current failure, which lasted not longer than three minutes, was recorded by the voltmeter. Since records taken in the incubating compartments at this time showed no temperature below the normal range, this failure was regarded as having no effect upon the eggs then incubating. Room Temperature and Minimum Incubator Temperature During Chilling. — Room temperatures prevailing during the current interrup- tions in different series were highest in the first series and lowest in the second (table 1). The relation of minimum incubator temperature to room temperature during chilling indicated that after 12 hours of in- terruption the insulation of the machine was still able to maintain a temperature in the compartment a few degrees above that of the room (fig. 1). Also in every case the minimum machine temperature was slightly above the physiological zero of cliick embryo development which was determined by Edwards (1902) to be about 68 °F. This means that the temperature in the chilling compartment was still above the degree at which embryonic development would be completely arrested. For the most part the embryos did not possess the ability to maintain a body temperature higher than that of the incubator compartment. BuL. 550] Effect of Interrupted Incubation TABLE 1 EooM Temperatures and Minimum Incubator Temperatures During Current Interruption ; Degrees Fahrenheit Incu- First series Second seriss Third series Special series Special series bation day chilled Room temper- ature Incuba- tor temper- ature Room temper- ature Incuba- tor temper- ature Room temper- ature Incuba- tor temper- ature Room temper- ature Incuba- tor temper- ature Room temper- ature Incuba- tor temper- ature 1 72 75 70 76 70 75 2 75 79 70 73 70 74 .... 3 71 74 67 73 71 78 70 74 .... .... 4 74 77 70 76 71 74 .... .... 5 72 76 67 73 71 74 .... .... 6 74 75 66 70 70 75 70 74 .... 7 74 76 66 70 70 76 .... 8 74 78 68 70 71 73 .... 9 73 77 70 76 71 75 71 74 71 75 10 76 80 73 77 71 75 11 71 74 70 77 68 74 71 75 71 75 12 74 78 68 77 69 75 13 73 75 68 75 72 76 71 75 71 75 14 75 80 70 79 71 74 15 75 79 76 78 71 76 73 75 16 75 82 74 86 71 76 17 72 76 71 85 72 78 18 71 79 66 82 73 78 73 77 72 76 19 78 84 68 74 72 78 20 74 79 68 78 71 76 21 69 75 68 85 71 86 71 84 70 81 Aver- age 73.4 77.5 69.2 76.7 70.8 76.0 71.3 76.0 71 76.4 /05 ■C; 95 \ ■^ 90 St, 85 i 75 In L- 1 1 1 1 1 1 1 1 Norma/ /ncubotion te/vperoture'7 (Put \ R, / - Off Z30 /i.M. \ / X ^ ^ Chi///np comportmer temperature It / .^ 7j / f?( lom temp erati ire -n . f ._. _. ... h--^. r^ -^. __ .. _- - ' 1 _.^ -__. 6 AM. 7 e /£ /P.M. 2 /£ Fig. 1. — A typical record of temperatures in the chilling compartment and in the room where eggs were chilled during the first week of incubation. After being transferred to the chilling compartment, the eggs were maintained at the normal incubation temperature for one hour preceding current interruption. Following interruption they were returned to the regular incubation compartments when a normal incubating temperature had been regained. Even after a 12-hour interrup- tion, the temperature of the chilling chamber did not reach that of the room. University of California — Experiment Station J 1 'i^jijiq'Buoi'Bq afq'BJ'BcIuioQ 103.4 88.1 103 100.0 103.9 sj^oiqo Jfoaqo ! M i i i : ;g ;g :S : ! : iS§ i :S5 i sjioiqo painqo : i : : : i : !S iS ;§ M : :S i iS oo ;o{ qo'Ba ui s3§9 aiq^JBduiOQ ::::::::■* :co :-H ::: :co : :o ::::::::05:05:oo::::cO::>0 o 1 «3 'Aqiq^qoi^q afq'Bj'Bduio^ KC ioiqo J^oaqo ! IS : ;S : ;g ;S iS !§:!?:: :g 1 s>ioiqo painqO : ;g : iS ; :S i^ ilJ; !JS i :§ : :S o ■\o\ qoBa UI sSSa ajq'BJ'BduioQ N§ Ms Ms is ;s ;s Ms 1 IS i u IS ^^U90 J8d 'A^iqiqBqDcj'Bq afq'BJ'BduiOQ 050lCTft-HOiO-<»ioiqo iioaqo gS§§^§g§J^?S?2S§SSSS^J5S^S s>,oiqo pailiqo §§s?2Sgss;?2§sss^^^sss§^j;; 05 CO iO[ qoBa ut sSSa ajqBJ'BduioQ irOT^C^— (00O0005OO5OO50500O50000t0«D-<*ICD .1 1 ;^^U8D J8d 'Aiqiqeqo^Bq afqBJ'BduioQ COOOlOT-HlM-HMCOfOOlOOOiTff-^-H-^-^-HO CO SS^SSSSSiSSSsSsSSSSSSSS s>ioiqa >ioaqo ^?:^Sp:slSSSS^§SSSJSS§gs^^ 1 s^oiqo painqo IM — COOe<500C«5lC^ooc*:t<05'— iC^OOO>COS-^"5lO 05ooo20500oor-oo«ooocoioooooooo(Moocoe^ 1 Incu- bation day chilled '-lCC|C0-«J<'0CDt^00CT>O— i(MCOTj<»OCOt^QOC»0-^ 3 e2 :§ 5 5 -^2 BuL. 550] Effect of Interrupted Incubation 9 Only in the case of hatched chicks in lots chilled on the 21st day was there a definite maintenance of body temperature. This was reflected by the chilling-compartment temperatures in all series except the first, in which no chicks had hatched at the time the current was interrupted. These results were in agreement with the conclusions of Pembrey, Gordon, and Warren (1894-1895) that the transition from a cold to a warm-blooded reaction on the part of chicks takes place on the 21st day of incubation. Hatchahility of Comparable Eggs. — In analyzing hatchability data only those eggs were used in the calculation in which the embryos reached developmental stages equal to the normal for the day of incu- bation chilled. A further requirement was that these eggs come from the same hens which had live embryos amongst eggs of the check lot of the same hatch on the day when chilling took place. Thus, comparable eggs were eggs originating from the same hen and bearing living embryos on the day of current interruption — each q^^ in a chilled lot having a similar and comparable e^g in the check lot. Comparable hatchability was calculated as the percentage of chilled chicks in relation to check chicks, from comparable eggs (table 2). Considerable variation was found between comparable hatchabilities for the same day of chilling in the different series. This was expected since the number of comparable eggs was relatively small in every case. These data, however, generally failed to indicate any particularly criti- cal point in embryonic development at which the current interruption decreased hatchability. The summary of all series showed the average number of chicks produced in chilled lots to be 96.6 per cent of that of check lots (table 3) . In comparable hatchability, eggs chilled on the 11th day were lowest with a value of 92.3 per cent. Yet, in the second series (table 2) the lot chilled on the 11th day was the only one hatching better than its check. Thus, evidence of a day of chick development more sus- ceptible to death from chilling than other days of development was not definitely established in this experiment. The second series gave hatchability results lower in chilled lots than any other series and it was also run under the lowest average room tem- perature. The possible importance of slight differences in minimum room temperatures in contributing to varying mortality results was indicated by this observation. However, differences in the individual pullets which produced the hatching eggs, considered later, made the significance of this possibility questionable. When the data for the different days of incubation were summarized according to the week of incubation in which chilling took place. 10 University of California — Experiment Station TABLE 3 Hatchability op Comparable Eggs, Summary of All Series Incubation day chilled Comparable eggs in each lot Chilled chicks Check chicks Comparable hatchability, per cent* by days Comparable hatchability, per cent* by weeks 1 ... 312 321 401 318 259 346 231 256 420 239 388 218 409 256 334 248 214 310 212 154 278 195 178 251 179 169 241 158 190 278 185 253 149 310 211 268 201 164 259 191 138 252 198 173 261 187 161 259 156 196 296 191 274 148 329 209 280 211 170 271 194 146 264 98.5 102.9 96.2 95.7 105.0 93.1 101.3 96.9 93.9 96.9 92.3 100.7 94.2 101.0 95.7 95.3 96.5 95.6 98.5 94.5 95.5 ■ 2 3 98 3 5 6 8 9 10 11 95.9 12 13 14 15 16 17 18 95.9 19 20 21 Total 6,124 4,420 4,574t 96 6 96.6 * Comparable hatchability = Number of chicks in chilled lot XIOO. Number of chicks in check lot t Since the same check lot served as a control for two or three chilled lots, the totals of check chicks here given are for comparison with totals of chilled chicks and do not represent the actual number of check chicks produced. slightly lower comparable hatchabilities were found for the second and third weeks than for the first week. This indicated that chilling effected after the first week of incubation induced a slightly higher mortality than chilling during the first week. Production of Weak and Crippled Chicks. — All chicks hatched were carefully graded ; all weak and crippled chicks were rejected as being unsalable. With respect to chilled and check lots a statistical analj^sis gave the following results : Chilled Chech Difference Number of lots 76 30 Number of chicks 5,074 2,157 Number of rejected chicks 173 41 Per cent rejected chicks 3.44±:0.173 1.80±0.167 1.64±0.240 The difference was 6.83 times the probable error of the difference which proved the increase in per cent of rejected chicks produced by current interruption to be significant. Chilled lots tended to have more weak chicks, many failing to show proper closure of the abdomen after taking BuL. 550] Effect of Interrupted Incubation 11 up the yolk sac. There was little difference between check and chilled lots in the numbers of deformed chicks produced. Mortality Bates of Chilled and Check Eggs. — The mortality rates (table 4) included all eggs set in supplementary lots as well as check and chilled lots. Since all eggs in chilled lots dying previous to chilling did so under normal incubation conditions, they were classed as check mortality. In order to give a true comparison of mortality under differ- ^ — , 1 'I ' 1 / 1/ \ i Lss end Chil/ed ChecM j 1 J // ' 1 V \\ / rA / V .^ X" \ -r^^ ; 1 1 1 1 1 1 r 1 1 1 3 9/0 1/ /B /3 Dot/ of Inci/bation. 19 SO 2/ Fig. 2. — Mortality rates in chilled and check eggs. Most of the increased mortality in the chilled eggs was found before the 5th and after the 17th day of incubation. ent conditions for a certain day, the mortality rate was expressed as the percentage of all embryos surviving the previous day which died on the day of incubation in question. The results showed no striking increases in mortality rate for any par- ticular day to have been produced by chilling.'^ In general, comparison of the mortality curves (fig. 2) indicated that such mortality increase as was produced by current interruption tended to be expressed as a slightly greater loss at major peak points in the curve for normal incu- bation. 6 Both types of blastoderm without embryo were classed as death on the 1st day of incubation, while all pipped eggs were included in the 21st day mortality. 12 University of California — Experiment Station cq 5,594 422 7.54 3,860 230 5.96 00 + s 1 i - d 1 o is- ic" CO i 1 § C 5 ^ - S CO CO t^__ CO -H S5 d + ■>*< !- ^ S (N "* 00 CO ec § s " 33 "^