The raccoon dog has only recently been farmed, for its fur, in Finland from stock originating by capture of wild animals. Knowledge of the reproduction of the raccoon dog is limited (Asdell, 1964) and its breeding still involves several problems. Since the raccoon dog is a member of the family Canidae, its mating features can be expected to resemble those of the dog and fox whose reproductive physiology is fairly well known (Harrop, 1960; Venge, 1959). However, more information about the oestrous cycle and gestation in the raccoon dog is needed for adapting this naturally monogamous species to the polygamous mating used in the fur industry. In this study which lasted three seasons, starting in 1974, 20 female raccoon dogs were used in the first two seasons and 14 in the third. All the animals were housed at Helve's Research Farm, Veikkola.

Cattle were injected with PMS, bred and slaughtered 3, 30, 45, 60 and 90 days after ovulation and the genital tracts dissected. From 30 to 90 days of pregnancy the percentage increase in the weight of single embryos was 85 times as much as the increase in crown-rump length. The volume of amniotic fluid increased 580 times in the second month of pregnancy and increased twice during the third month of pregnancy. The allantochorion did not lengthen between 60 and 90 days of pregnancy. At 30 days of pregnancy there was no significant difference in the crown-rump length or the weight of embryos of singles, twins, triplets, quadruplets or quintuplets. The volume of placental fluid per embryo was higher in singles than in twins and triplets; the volume of placental fluids per embryo decreased further in quadruplets and quintuplets. The weight of the placental membranes per embryo was heavier in singles than in twins, triplets and quadruplets; the weight of membranes was markedly decreased in quintuplets. The effects of overcrowding in utero on the conceptus was more pronounced at 60 days than at 30 days and in quintuplets than in triplets and quad- and Reece, '53). Interlocking between the chorion and the maternal cotyledons does not begin until the fortieth to fiftieth day (Chang, '52). Before that time, the relationship between the chorion and the endometrium is more or less of a diffused epitheliochorial placenta; during the second month this begins to change to a cotyledonary placenta.The development of the allantochorion in the cow is of particular interest. Essentially, the chorion is formed by elongation of the trophoblast, which becomes invested with a layer of endodenn followed by the lateral development of the mesoderm. The allantois develops as an outgrowth of the hind end of the gut, and rapidly elongates and closely invests the chorion. The vascularized allantois brings its blood vesseIs in close opposition with the chorion, so 303

No abstract

Cytological and histological characteristics of normal and freemartin gonads have been studied in 45-, 60-, and 90-day bovine fetuses during gonadotropin-induced multiple pregnancy. In both sexes of 45-day fetuses the second proliferation of germinal epithelium was not developed whereas the primary tunica albuginea was well developed. Fetal testes showed higher cell activity than fetal ovaries. Mitotic activity seemed slower in 60-day freemartin gonads than in normal fetal ovaries. The chromosomal stages prophase, metaphase, anaphase and telophase corresponding to oogonia were less numerous than in normal fetal ovaries. The cytological appearance of freemartin gonads in 60-day fetuses was unaffected by the ratio of male: female fetuses. The freemartin gonad was characterized by an irregular distribution of cortex and primary tunica albuginea. In the ovaries of 90-day fetuses the last chromosomal stage observed in the oocytes was the pachytene stage. The first establishment of primordial follicles was observed.

Changes in the concentrations of ovarian steroid hormones during oestrus and pregnancy in the dog have recently received much attention by several investigators (, b). The fox seems to be the only other canine species for which any information on the endocrine changes associated with the oestrous cycle is available (M\l=o/\ller,1973;Austad, Lunde & Sjaastad, 1976). As part of a study of the reproductive physiology of the raccoon dog Nyctereutes procyonoides (Valtonen, Rajakoski & M\l =a"\kel \l =a"\, 1977), it was decided to investigate the levels of oestradiol-17\g=b\ and progesterone in the plasma during oestrus and pregnancy.The six female raccoon dogs used in this study were housed in couples with male dogs at Helve's Research Farm, Veikkola. The course of oestrus was determined from vaginal cytology and close inspection of behaviour. Blood samples were collected from the saphenous vein two or three times a week from the first signs of approaching oestrus until 1 week after the end of oestrus and thereafter only once a week. The concentration of pro¬ gesterone was determined by radioimmunoassay using highly specific antisera according to the method of Thorneycroft & Stone (1972), except that iodohistamine-steroid was used as a tracer instead of [3H]progesterone. The sensitivity of the assay was 25 pg/ml. The concentration of oestradiol-17ß was determined by radioimmunoassay according to the method of Edqvist «fc Johansson (1972) again using iodohistamine-steroid as a tracer instead of [3H]oestradiol-17ß. The sensitivity of the assay was 5 pg/ml. Because of the individual differences in the lengths of pro-oestrus and oestrus, all data concerning the levels of progesterone and oestradiol-17ß were timed relative to the time of coitus (Fig. 1). Because sampling was infrequent, no statistics could be presented. The level of oestradiol-17ß reached a maximum (highest individual value 55 pg/ml) during pro-oestrus or at the beginning of oestrus. After coitus, the concentration of oestrogen fell rapidly to a low or undetectable level and remained low during early pregnancy. The level then rose slightly between days 13 and 26 of gestation and declined again towards term.The concentrations of progesterone were low during pro-oestrus. During oestrus, the concentrations increased rapidly and rose to a maximum (highest value measured 23-4 ng/ml) during the first half of pregnancy. From the middle of pregnancy the level of prog¬ esterone fell steeply to less than 5 ng/ml and values measured after parturition were below 1 ng/ml. The level of progesterone in non-pregnant female raccoon dogs rose similarly during oestrus and early metoestrus (M. Valtonen, E. Rajakoski & P. Lähteenmäki, unpublished observations).The concentration of oestrogen in the raccoon dog during oestrus is the same range as in the domestic dog, which is low compared with other domestic animals and man. The