LENGTH OF GESTATIONS IN JERSEY COWS* LYNN COPELAND Register of Meri~ Department, American Jersey Cattle Club, New York City Duration of pregnancy is a problem ever confronting breeders of dairy cattle, for it is absolutely essential in the management of livestock for the owner Or herdsman to have a definite knowledge as to when his pregnant cows are due to calve. The length of the gestation period is therefore of interest not only to the student of embryology but to every farmer who owns or cares for livestock. It is regrettable in view of the importance of the subject that the literature pertaining to the length of gestations is very meagre. In recent years very few results of investigational work dealing with gestations in dairy cattle have appeared in print. Numer- ous gestation charts or tables have been published showing easy methods of Oguring the "approximate" calving date. These tables do not all agree, some being based on gestations of 40 weeks, some on the basis of 282 days and others for shorter periods of time. In 1817~ M. Tessier (1) studied 575 eases and reported a varia- tion from 241 to 321 days. The average was 282.2 days and 95 per cent of the calves were carried from 270 to 299 days. In a more extensive tabulation made by the Earl of Spencer (2) in 1840, the period varied between 220 and 313 days for calves born alive. The average was 283.3 days for 764 cases, including 23 twin births which averaged 277.2 days. About two-thirds (67 per cent) were from 280 to 289 days, 90 per cent were from 275 to 294 days and 95 per cent from 270 to 299 days. None born under 242 days were raised. C. B. Bement (3), in 1845 found the variation to range between 276 and 299 days except for one short period of 213 days and a long one for 336 days. The average was 286 days (288 for 36 bull calves, and 283 for 26 heifers). Various breeds, Shorthorns, * Received for publication November 25, 1929. 257
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`2 5 8 LYNN COPELAND Devons, Herefords, Ayrshires, and grades were included. L.F. Allen (4) in 1868, reported a study of 50 cows of different breeds showing an average gestation of 284 days, with a range of 268 to 291 days. H. H. Wing (5) tabulated 182, cases, mostly Holsteins and Jer- seys. The range in the length of the gestation periods was from 264 to 296 days. The average found was lower than reported by the Earl of Spencer or Tessier being 280 days for 97 Holsteins and 279 days for 56 Jerseys. Five twin births averaged 275 days. Fitch, McGilliard and Drumm (6) in a study including four dairy breeds reported that the breeds varied in length of gestation as follows: days Jersey --100 gestations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.3 Guernsey--103 gestations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283.0 Ayrshire --113 gestations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.0 Holstein --220 gestations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281.0 The average length of all the gestations studied was 282.4 days. The bull calves were carried 283.2 days and the heifers 281.9 days. INVEBTIGATIOI~AL When a Register of Merit record is completed a calving affida- vit is sent to the owner. It is retained by him and if the cow drops a living calf after finishing her test period, he fills in both the service and calving dates. The accuracy of these dates and the fact that the calf was alive at birth must be attested before a notary and then the affidavit is returned to the Breed Association office. If the cow does not calve within a certain length of time or if the calf is not alive at birth no affidavit is necessary. This study concerns the records accepted by the American Jersey Cattle Club during 1927 for which calving affidavits were returned swearing that living calves were dropped. It included 1075 gestabions, all of which were apparently normal, if a living calf can be assumed as evidence of normality. The length of each of these gestation periods was determined and also the sex of the calf in all cases where the progeny had been registered. In
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`LENGTH OF GESTATIONS 259 computing the length of the gestation period the day on which the calf was born was included in the total number of days, but not the day of service. For example, if a cow was served on January 12 and calved on October 18 the length of the period of preg- nancy would be considered as 279 days. These gestations were then grouped according to the age of the dam at the time of calv- ing. In table 1, are presented the data covering this phase of the investigation. The shortest gestation reported was for 228 days and the long- est for 312 days. Approximately 62 per cent of all the periods T A B L E 1 Effect of age in length of gestation ~eriods AGE Yearlings and Jr. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S r . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J r . 3 ................................................ S r . 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J r . 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S t . 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 years and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NUMBER OF CABEB 141 46 195 124 111 100 142 89 58 27 17 12 6 7 A ~ R A G E LEI~GTH OF GESTATIONS 278.51 277.96 278.34 278.63 278.38 278.80 278.73 277.45 279.26 277.56 280.35 280.58 277.67 281.43 Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,075 278.51 fall between limits of 275 and 283 days and 81 per cent come be- tween 271 and 285 days. The average length of all the gestation periods was 278.51 days. However, only 68 of the 1075 calves were born on the 278th day of pregnancy, and the data indicate that there is almost an equal chance of the calf being born on any day after 271 days have elapsed and until the 285th day is reached. Table 2 iUustrates how these gestations group them- selves when arranged according to their length.
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`260 LYN~ COPELAND At the time this study was made, only 683 of the progeny had been registered in the Herd Books of the American Jersey Cattle Club. Of this number 297 were bull calves, 382 heifers and 4 sets of twins. On the basis of sex, the gestation periods of the 297 bull calves averaged 279.48 days and the 382 heifers averaged 278.64 days. The 4 sets of twins showed an average gestation of 275.50 days. It was also of interest to find that while 63 per cent of the 1075 calves were registered, that of the 26 carried for 265 days or less only 11 or 42 per cent were registered while the 44 calves carried TABLE $ Frequency table grouping gestations according to length C L A ~ FREqUenCY 250 days and below 251 to 255 256 to 260 2{}1 to 265 266 to 270 271 to 275 276 to 280 281 to 285 286 to 290 291 to 295 296 to 300 Over 300 days 5 4 10 7 46 206 384 325 61 19 6 2 288 days or longer, 30 or 68 per cent were registered. Of the 5 calves carried for less than 250 days only one was raised, and of the 8 carried for 296 days or more, 5 were raised. This would indicate that those calves resulting from abnormally long geso tations have a better chance of living than do those born pre- maturely. Another question is whether certain cows do not possibly have a habit of carrying their calves either for shorter or longer period of time than the average for the breed. That is, if a heifer drops her first calf at 270 days, should the owner expect her following gestations to be shorter than usual. Twelve of those cows show- ing gestation periods longer than 290 days had at least 2 additional
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`LENGTH OF GESTATIONS 261 recorded progeny and the same was tree of 13 of the cows with gestations of 265 days or less. The life time breeding records of TABLE 3 NAME OF COW hm o~ ~m Zm m~ NAME OF COW ~m ZM ~o Progeny records of twelve cows carrying at least one calf for an abnormally long gestation period Flying Chief's Golden Beauty 480952 Tom's Lady Capitan 345664 Able Fox's Rainbow 566179 Miss Dumont's May 566269 Fomasa's Irene 550669 dQys 275 281 276 28O 282 291 28O 280 279 28O 280 28O 299 281 278 273 275 280 293 28U 279 28C 289 31¢ 28~ F° M. M. F. M. M. M° F. M. F. M. F. $ M. M. F. F. M. M. F. ! F. F. M. M, F ° F. $ Queen Ladette of Bryan 628569 Oxford's Royal Nora 595773 Design's Dsirylike Ildg 663202 Campanfle's Pansy 585974 Belle's Huckleberry 521868 { f Knight's Dolly Dimple J 51O442 L Sir Owl's Jewel's Julia 64O298 dalta 281 284 295 279 287 286 290 273 276 299 28O 281 M 291 279 2'I4 296 289 282 gl 292 F . M. M. M ° M. M. F. S . F. F. F . F. F. F. M . F. $ F. M. M. F. F. M. * Not registered.
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`262 LYNN COPELAND TABLE 3---Oo~inued NAME OF COW °~ D~ m NAME OF COW Progeny records of thirteen cows carrying at least one calf for an abnormally short gestation period Passport's Jap's Princess 616755 f The Kid of Ohio's Gusta ] 6548O7 Hildegarde { Majesty's 558997 Sovictor Lenore 543955 Dolly's Milkmaid 575423 Star's Jolly T. A. 598467 f Jewel's Majestic Betsy J 588297 days 281 266 261 279 259 278 279 278 228 279 285 264 279 284 265 282 278 282 281 256 2731 285 257 F° M. F. F . M. F . F. M . M. F. M° F. M. M° F. F. F. F. F . F. F. Jap's Poetess 460418 Prince's Louise M 494446 1 GoldenDo 664077F°ntaine You'll t Imp. Beaulieu Comtesse l 692510 Tiddledywink'SEva 645558 Princess { r Owl Knight's Lady 526650 I days 283 281 29O 237 279 290 231 280 28O 265 283 275 251 282 256 280 280 281 281 239 279 F° F. F. $ M° M. F° M. M ° M. M. M. F. F. F. M. F. Jersey one-thousand-pound fat producers with four or more registered progeny AbigMl of Hillside ,1,57241 284 M. Rmda's Insie 2"11 F. 282 M. 565559 278 F. 277 M. 276 M. * Not registered.
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`LENGTH OF GESTATIONS TABLE 3--Continu~d 263 NAME OF COW O NAME OF COW Jersey one-thousand-pound fat producers with four or more registered progeny---Continued Darling's Jolly Lassie 435948 Prince's Emma of H. S. F. 359390 Lady's Silken Glow 313311 St. Mawes Lad's Lady 451568 Red Lady 396118 days 285 277 277 281 286 28O 278 281 276 281 284 277 274 275 286 278 281 284 252 276 278 283 272 278 279 281 276 279 282 275 282 282 284 M° M. F. F. M. F. F. M, M . F. F. F. F. F . M. F. F. M. F° M. M. M. F. F. M. M° F. M. F. M. F. F. M. Lad's Iota 350672 Madeline of Hillside 389336 Plain Mary 268206 Vive La France 319616 Fauvic'e Star 313018 daya 292 266 275 277 272 254 274 278 280 278 284 285 282 287 284 288 268 288 274 275 285 277 276 271 286 284 273 285 280 273 259 M° M. F. F. F. F. M. F° M. M, M. M. F° F. F. M. M. M. F. M, F. M. M. F. M. M. Fo M. F, F. M.
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`264 LYNN COPELAND T A B L E ~ - 4 ~ o ~ d ~ NAME OF CO~" Z M NAMM O!? OOW h Jersey one-thousand-pound fat producers with four or more registered progeny--Concluded Princess Elise 418113 St. Mawes Lad's Pride 515044 271 ] F. 278 ] M. 276 ] F. 285 I F- 285 F. 273 F. 267 F. 272 M. 295 i M. Princess Xenia 356699 Tiddledywink's Girl 560784 l= 280 278 281 279 Quality 279 278 277 1 ~ , F. F. M. 1 ~ . F. M. M. these 25 cows were studied. Also, investigation showed that 17 of the 24 Jersey cows with butterfat records over one thousand pounds of fat were the dams of 4 or more registered calves. It was believed that the breeding records of such cows would be the most reliable obtainable and the gestation periods of their progeny are therefore given in table 3. Examination of the breeding records of the cows in these groups does not reveal any correlation between the length of pregnancies for the same individual d(cid:127)m. In fact a great deal of variation is noted in most cases. In the first group the 12 extremely long gestations averaged 295.25 days in length and the other 40 ges- tations of these same cows averaged 280.15 days. In the second group the 13 abnormally short gestations averaged only 251.46 days in length while 32 other gestations by these 13 d~m~ averaged 280.47 days. From these records it does not seem possible to predict or determine the probable length of a future gestation period even though the length of several previous periods are known. Included in the 3 preceding groups are 186 gestations. The average length of all of these gestations is 278.19 days. However, since the accuracy of the service dates of these preg-
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`LENGTH OF GESTATIONS 265 naneies have not been attested to they were not included in the 1075 gestations on which the main portion of this study was based. SUMMARY 1. The average gestation period for the 1075 cases studied was 278.51 days but there appears to be an equal chance of a cow calving anytime between the 271st and the 285th day. 2. The age Of the dam apparently has no effect on the length of gestation. 3. Bull calves were carried an average of one day longer than heifer calves, 297 bull calves being carried for an average of 279.48 days and the gestations of 282 heifer calves averaging 278.64 days. 4, The data are too scant to draw conclusions relative to twin births but the results compare with those obtained by other investigators in that the gestations of twins are usually several days shorter than the average. 5. Calves resulting from abnormally long gestations seem to have a better chance of living than do those born prematurely. 6. No correlation could be detected between the length of different gestations in the same individual d~m. Cows showing one or more short gestations also exhibited other gestations longer than the average and vice versa. REFERENCES (1) Tmssx~.R, M.: Mem. de l'Acad, des Science, Paris t 1817. (2) Rlolrr Hos. Ex~ oF SPlzNCER. " Gestations of cows. Jour. Royal Agric. Soc., 1840, i, 168. (3) Bmm~rr, C. B.: The Cultivator, 1845, p. 207. (4) ArJ.~, L. F.: American Cattle, 1868, p. 259. (5) Wi~o, H. H.: The Period of Gestation in Dairy Cows. Cornsll Bulletin, 1899, 162. (6) FITCH~ J. B., ~/~CGILLIARD, P. C., AND DRUMM, G. M. : A study of birth weight and gestation in dairy animals. Jour. Dairy Sci., May, 1924, vii, no. 3.
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