In Part A of Study I, six groups of female standard mink were fed (once daily) either 5, 10, or 15 mcgm. of DES/mink/day or a forage antiestrogen extract at levels of 5, 10, or 15 gm. equivalent of alfalfa/mink/day. In Part B, seven groups of female pastel mink were fed (once daily) 15 mcgm. of DES/mink/ day prior to and at various stages of the gestation period. Also, the antiestrogen extract was again fed (once daily) at levels of 5, 10, or 15 gm. equivalent of alfalfa to three groups of female pastel mink after implantation of the fertilized egg had occurred. From the results of Part A and B of Study I it is evident that DES at levels as low as 5 to 15 mcgm/ mink/day caused complete reproductive failure. At the 15 mcgm. level it is possible to prevent or disrupt pregnancy if the hormone is administered for at least one week during the period starting one week before breeding and ending 30 days prior to parturition. The forage antiestrogen at levels between 5 and 15 gm. equivalent of alfalfa reduced the number of kits per litter from 5.8 to 1.6. The feeding of various levels of DES or the antiestrogen extract did not adhere to a dose/response relationship either in interrupting pregnancy or reducing the number of kits per litter. The DES, fed at levels of 5, 10, or 15 mcgm./mink/ day was a more potent antifertillty agent than the forage antiestrogen fed at levels equivalent to 5, 10, or 15 gm. of alfalfa. In Part A of Study II, 200 mature male and female mink of a variety of colour phases were divided into five groups. The groups were fed (twice daily) rations varying in crude protein (36.6 to 44.8%, on a d.m. basis) and gross fat (21.3 to 28.9%, on a d.m. basis). In Part B, 280 pastel and standard kits (6-7 wks. old) were fed (twice daily) rations varying in crude protein (39.0 to 54.3%, on a d.m. basis) and gross energy (5.20 to 5.52 Kcal/gm. dry feed). From the results of Part A and B of Study II it is evident that rations containing 35 to 40% crude protein and 20 to 25% fat, on a dry matter basis, are satisfactory for the late growth and maintenance requirements of mink. The mean apparent digestibility coefficients obtained in these studies for dry matter, protein, fat, and energy are 66.38, 74.05, 87.20, and 73.74%, respectively. As the apparent digestible energy (A.D.E.) was raised from 353.4 Kcal/100 gm. dry matter to 426.0 Kcal/100 gm. and as the apparent digestible nitrogen (A.D.N.) level reached 4.980 gm/100 gm dry matter, the early growth of both male and female mink was improved. Maximum early growth rate was obtained in kits when the ration contained 85.54 Kcal of A.D.E./gm A.D.N. (13.6 Kcal gross energy/gm gross protein). Also, increasing A.D.E. content in the diets had a definite protein-sparing effect. Maximum nitrogen retention was obtained when the diet contained 426.0 Kcal of A.D..E./100 gm. of dry feed. Finally the results suggest that the growing male kits (from 6-28 weeks of age) were capable of utilizing feeds more efficiently than female kits of the same age. / Land and Food Systems, Faculty of / Graduate

A study, comprised of five parts, has been carried out on seven adult, female, pastel mink. Metabolic responses to ambient temperature have shown that these mink cannot tolerate temperatures much above 29°C, but are not unduly disturbed by low temperatures around 0°C. Under sleeping conditions, and within their thermal neutral zone (25 ±2°C) , the three animals measured did not demonstrate an abnormally high metabolic rate. Under conditions of prolonged fast, these mink appeared to maintain normal activity, although they lost much bodyweight. The apparently high, daily, urinary, nitrogen excretion, when related to heat production, gave a value of 2.5 mg of urinary nitrogen per Calorie (A.D.E.). The effect of additions of fibre to a basal ration has shown an inverse relationship between this component and the time of passage of the feed. The apparent digestibility of the ash component in the ration was markedly decreased with increasing increments of dietary fibre, but that of the fat was only very slightly reduced. Under these experimental conditions, nitrogen retention appears to be always positive, possibly reflecting a constant demand for fur growth, and a constant loss of nitrogen in the form of ammonia. Maintenance energy (A.D.E.) requirements of these mink have been quantitated. The effects of a decrease in cage capacity and the additions of fibre to the ration appear to decrease the animal's energy requirements. The Caloric intake of a one kg mink is almost identical to that suggested by the N.R.C. Water intake, when related to energy (A.D.E.), is appreciably less than the 1 gm / Calorie of heat produced generally accepted for mammals. However, it is in close agreement with figures obtained for the cat and for the mouse. The addition of a non-nutritive bulk to the ration significantly increases the water intake when related to the A.D.E. of the ration / Land and Food Systems, Faculty of / Graduate

This study was undertaken to investigate the ultra-structure, cytochemistry and maturation changes of mink spermatozoa which are important in biological research and in their relevance to artificial insemination. Mature standard dark mink were used in this study. Spermatozoa were released from the testis and epididymis (caput, corpus and cauda) of the male mink, and were also collected from the vagina of female mink immediately after mating. Conventionally prepared thin sections were observed under a transmission electron microscope. Enzymes were cytochemically localized in spermatozoa. The mink spermatozoon head showed six swellings on the dorsoventral aspects: two connected hump-like structures at the anterior border of the equatorial segment of the acrosome, and one at the postacrosomal sheath on each side. These swellings, which show a strong acid phosphatase activity, appeared to be a species-specific structural feature which might be necessary for the recognition of the ovum or for sperm-ovum attachment in fertilization. The occurrence of the postacrosomal swelling in spermatozoa was significantly increased (p < 0.01) during the passage of spermatozoa through the reproductive tract. Although the total length of the head did not change significantly during the passage of spermatozoa down the reproductive tract, the anterior acrosomal length was significantly decreased (p < 0.001), while the postacrosomal length was significantly increased (p < 0.05). The cell membrane on the peripheral part of the acrosome, with the exception of the tip of the acrosome, was significantly separated (p < 0.05) during the passage of spermatozoa through the reproductive tract. The neck appeared to show dorsoventrally continuous but laterally separated capitulum which was followed by two major and five minor columns, forming at first a striated ring and then joining with the dense fibers.of the axial fiber bundle. Some axoneme remnants were found in the interior of the column bundle. The shape of the annulus was triangular in longitudinal sections. The occurrence of the cytoplasmic droplet was significantly decreased (p < 0.001) during the passage of spermatozoa through the test is and epididymis. The motility of spermatozoa was significantly increased (p < 0.05) as spermatozoa passed the successive parts of the reproductive tract. The activities of acid and alkaline phosphatases, ADPase, ATPase and DOPA oxidase were found to be distributed in the head, middle and principal pieces of epididymal spermatozoa. Glucose-6-phosphatase, 5-nucleotidase, non-specific esterase, malate, succinate, lactate and isocitrate dehydrogenases, and NADH diaphorase activities were seen to be confined to the middle piece, while the esterase and malate dehydrogenase activities extended to the head base. The activity of 6-phosphogluconic dehydrogenase was not detected. Although most enzyme activities of spermatozoa were enhanced during the passage of spermatozoa through the reproductive tract, several enzyme activities (acid and alkaline phosphatases, ADPase, ATPase, and malate dehydrogenase) were distinctly reduced in spermatozoa from ejaculated semen recovered from female mink following mating. The presence of enzyme inhibiting factors in the seminal plasma or female reproductive tract was discussed. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.

Graduation date: 1996

This thesis is about olfactory communication in mink (<i>Mustela vison</i>) and how it may relate to their social behaviour. The sources of mammalian social odours and studies of scent marking by carnivores were discussed. The possible functions of scent marking in territories were also discussed, with particular reference to Gosling's scent matching hypothesis. The distribution of faeces (scats) in a coastal population of mink was ddtermined on a monthly basis. Most scats were found in the months December to April, which includes the mating season. Although scats tended to occur singly, they had a clumped distribution because single scats tended to be deposited around certain features in the enviornment. Scats were found around the same features over a number of months. The areas where scats were deposited also tended to have a clumped distribution when data from all months were considered. A trained male mink was able to discriminate between the faeces of mink irrespective of their sex or degree of association with the experimental animal. Over a 48 hour period, male mink over-marked faecal samples from other mink with their own faeces. Females normally only over-marked faeces from females kept in neighbouring cages. During lactation and in August and September the females over-marked faeces from unknown males and females. When testing the immediate response of mink to faeces, both male and female mink spent more time sniffing at faeces from other mink than at their own faeces. Males also spent more time sniffing at faeces from females during the reproductive period than they did outside the reproductive period. During their immediate response to faeces, the males tended to produce trails of urine on top of or beside samples of faeces from unknown males and females. While in reproductive condition, mink spent more time sniffing and produced more urine trails in response to samples of urine collected from females that were likely to be in oestrus than at samples collected from females unlikely to be in oestrus. Outside the reproductive period both males and females produced urine trails in response to urine from unknown males and females. Male mink produced more scent marks in response to samples of old (24 hours) anal sac secretion than to fresh anal sac secretion. Female mink produced few scent marks in response to either sample. Anal sac secretion when sprayed from a model mink, caused both mink and potential predators of mink, to back away from the model. The presence of the major constituent of the anal sac secretion, 2,2-dimethylthietane was shown to reduce the 'trapability' of mink and small rodents, and to cause feeding suppression in rabbits over a 24 hour period. Experiments designed to test predictions of Goslings hypothesis could not support or refute the hypothesis.

No description available.

No description available.

These studies were conducted to determine the mechanisms by which prolactin (PRL) exerts its luteotropic effects on the mink corpus luteum (CL). Three experimental models were developed and utilized in these studies. In the first model, the ovaries from pregnant mink were collected at regular intervals throughout gestation, half the animals were treated with the dopamine agonist 2-bromo-$ alpha$-ergocryptine (bromocryptine), to suppress their endogenous PRL levels, and half were exposed to their endogenous PRL levels. The second model consisted of treating anestrous animals with exogenous gonadotropins to induce follicular development and ovulation, half the animals were then treated with PRL while the other half were left as untreated controls. In the third model, CL were collected from mink at several stages of mink gestation. The cells were enzymatically dispersed, placed in culture and incubated with different concentrations of PRL, luteinizing hormone (LH), follicle stimulating hormone (FSH) and (Bu)$ sb2$cAMP. Using these 3 models, the effects of PRL on P450 side chain cleavage (P450scc), 3$ beta$-hydroxysteroid dehydrogenase (3$ beta$-HSD), steroidogenic acute regulatory protein (StAR), luteinizing hormone receptor (LHr) and prolactin receptor (PRLr) mRNA were determined. Messenger RNA levels for P450scc did not vary significantly over the course of mink gestation and treatment of animals with bromocryptine did not alter the abundance. In the anestrous model, treatment of mink with PRL reduced P450scc mRNA levels below that of the untreated control, while treatment of cultured mink luteal cells with increasing concentrations of PRL had no effect on the abundance of P450scc mRNA. The abundance of 3$ beta$-HSD mRNA varied over the course of mink gestation. Levels were low during embryonic diapause, increased during CL reactivation and peaked during post-implantation gestation. Treatment of mink with bromocryptine prevented the pre-implantation rise in 3$ bet