506 D E S J A R D I N S A N D H A F S

Figure 2. Pho tomic rog raphs (X290) of ov iducts ( top) and uter i (bo t tom) at 5 too. ( left) and 12 too. ( r ight ) . Oviducal epithel ia possessed secondary folds at 5 too. and ter t iary folds by 12 months . Note densely stained bodies which appear to be nuclei ext ruded f rom the epi thel ium at 12 too. (upper r ight ) . Endomet r i um of uterus at 12 too. was sect ioned t h r o u g h the wal l of the neck and t h rough the l umen of the basal por t ion of a gland.

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B O V I N E F E M A L E G E N I T A L I A 507

TABLE 6. HEIGHT OF THE VAGINAL EPITHELIAL CELL LAYER AND OF

THE CERVICAL, UTERINE AND OVIDUCAL EPITHIAL CELLS

FROM BIRTH TO 12 MO. OF AGE

Epithelial height

Age Vagina Cervix Uterus Oviduct

~Om Birth 1 4 . 7 + 0 . 4 a 1 9 . 1 ~ 0 . 7 20'.9+-0.7 22.8+_0.7

1 6 . 1 + 0 . 3 7 . 9 + 0 . 2 2 0 . 8 ~ 0 . 8 1 5 . 5 + 0 . 3 2 5 . 4 ~ 0 . 3 8.7+_0.2 1 6 , 2 ~ 0 . 6 30.5-4-0.3 3 8 . 9 + 0 . 6 9 .4~0: .2 I7,1-;-0.3 3 0 . 6 + 0 . 3 4 1 5 . 3 1 1 . 3 11 ,5+0, .5 3 1 . 4 + 0 . 3 5 18.2-t-0.8 1 1 . 6 + 0 . 3 1 6 . 5 ~ 0 . 6 30 .2~-0 .3 6 12.5___+0.5 1 0 . 2 ~ 0 . 3 10.7___+0.2 29,9 _+0.3 7 1 5 . 6 + 0 . 5 1 2 , 1 + 0 . 3 2 0 . 1 + 0 . 8 30.9-4-0.3 8 1 6 . 2 5 0 . 5 12.0+--0.3 14.8+__0.4 2 9 . 6 + 0 . 2 9 1 7 . 8 ~ 0 . 5 l S . l 2 4 . 3 ~ 0 . 6 3 1 . 1 ~ 0 . 4

10 2 0 , 0 ~ 0 . 5 2 4 . 8 + 0 . 6 2 7 . 9 ~ 0 , 5 3 0 . 1 ~ 0 , 4 11 2 5 . 7 2 4 . 1 ~ 0 , 7 2 9 . 3 ~ 0 . 4 29.2+_0.2 12 25.4_+1.1 2 3 . 3 ~ 0 . 6 3 3 . 0 ~ 0 . 6 2 8 . 4 + 0 . 2

~ .~gean i~ m~crons+standard error.

6 mo. of age. The oviducal epithelium was always ciliated, even in heifers a t birth. How- ever, subjective examinations suggested fewer cilia existed before than after first estrus. Similarly, microscopic inspection led to the conclusion tha t secretion blebs at the luminal extremities of oviducal cells were much more common in animals af ter first estrus.

Both superficial and basal uterine glands were absent unti l 5 too. of age, bu t they be- came progressively larger and the epithelial cells lining them became more columnar af ter 6 mo. of age (figure 2). The cervical epi- thelium was pseudostrat if ied at all ages, but numerous secretion blebs became especially conspicuous only during and af ter rapid pu- beral development between 6 and 10 too. of age.

These micromorphological observations, in agreement with the biochemical and gross anatomical measurements, support the conclu- sion that rapid puberal growth begins during the seventh month of age in Holstein heifers. Several cri teria plateaued and some were even reduced after 10 mo., suggesting tha t this age may mark the end of rapid puberal develop- ment.

Summary Sixty-five Holstein heifers were killed at

monthly age intervals in groups of five from bir th through 12 too. of age to determine morphological and biochemical cri teria of their reproductive organs. Ovar ian weight increased 2.7 times faster than bodyweight. While no ovarian follicles were visible macroscopical ly a t bir th, their numbers increased to a maxi- mum at 4 mo., decreased to 8 mo. of age and

remained relat ively constant thereafter. Gross anatomical and biochemical cri teria of uteri, cervices and vaginae increased a t rates similar to ra te of body growth until 6 too. of age, but shifted to more rapid growth thereafter. These changes in rates of reproduct ive growth were most pronounced for organ weights, R N A content and protein content and less marked for D N A content.

Height of the luminal epi thel ium of the tubular genital ia was s t imulated at bir th and regressed by 1 or 2 mo. of age. Thereaf ter , increases in height of epithelia in vaginae, cervices and uteri were most rapid after 6 mo., similar to changes in organ weights. Fur ther , secretion blebs on oviducal and cervical epi- thelia and bodies similar to nuclei apparen t ly extruded from oviducal epithelial ceils became more abundant after 6 too. of age.

These da ta indicate tha t rap id puberal growth in Holstein heifers commences during the seventh month of age and is largely termi- nated by 10 too. because several of the meas- ured cri teria increased at reduced rates after this age.

L i t e r a t u r e C i t e d

Asdell, S. A. 1964. Patterns of Mammalian Repro- duction. (2nd ed.) Comstock Publishing Associ- ates, Ithaca, N.Y.

Desjardins, C. and H. D. Hafs. 1968. Levels of pitui- tary FSH and LH in heifers from birth through puberty. J. Animal Sci. 27:472.

Desjardins, C., K. L. Macmillan and H. D. Hafs. 1958. Reproductive organ DNA and RNA of male and female rats from birth to 100 days of age. Anat. Rec. 161:17.

Gornall, A. G., C. J. Bardawill and M. M. David. 1949. Determinations of serum proteins by means of the biuret reaction. J. Biol. Chem. 177:75I.

Haekett, A. J. and H. D. Hafs. 1969. Biochemical and morpholo~cal changes in bovine tubular geni- talia during the estrous cycle. J. Animal Sci. 28: in press.

Macmillan, K. L. and H. D. Hafs. 1968. Pituitary and hypothalamic endocrine changes associated with reproductive development of Holstein bulls. r. Animal Sci. 27:1614.

Mellin, T. N., R. E. Erb and V. L. Estergreen, Jr. 1966. Urinary excretion of estrogen by the bovine before and after parturition. J. Animal Sci. 25~955.

Roberts, J. D. and J. C. Warren. 1964. Steroid bio- synthesis in the fetal ovary. Endocr. 74:846.

Sorensen, A. J., W. Hansel, W. H. Hough, D. T. Armstrong, K. McEntee and R. W. Bratton. 1959. Causes and prevention of reproductive failures in dairy cattle. I. Influence of underfeeding and over- feeding on growth and development of Holstein heifers. Cornell Univ. Agr. Exp. Sta. Bul. 935.

Tucker, H. A. 1964. Influence of number of suckling young on nucleic acid content of lactating rat mammary glands. Proc. Soc. Exp. Biol. Med. 116: 218.

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