Vaccination of feral pigs (Sus scrofa) using iophenoxic acid as a simulated vaccine.

OBJECTIVES: To develop an encapsulation method for delivery of vaccines to feral pigs, and quantify the effect of iophenoxic acid on captive feral pig blood iodine concentrations to assist in investigation of factors affecting vaccine uptake. DESIGN AND METHODS: Feral pigs were administered iophenoxic acid by oral gavage, and consumption was assessed for different encapsulation methods in baits. Blood iodine concentrations were monitored for eight days after consumption. The relationship between dose rate, time since dosing and blood iodine concentration was assessed for gavaged and baited captive feral pigs. Wild feral pigs were baited with PIGOUT baits containing 20 mg of encapsulated iophenoxic acid to simulate a vaccination program. Using knowledge from the pen studies, bait uptake and factors affecting bait uptake were investigated. RESULTS: Bait-delivered iophenoxic acid led to variable and inconsistent changes in blood iodine concentrations, in contrast to pigs receiving iophenoxic acid by gavage. This precluded accurate assessment of the quantity consumed, but still allowed a conservative determination of bait uptake. Iophenoxic acid in smaller capsules was consumed readily. Increasing baiting intensity appeared to increase bait uptake by wild feral pigs, and pigs of varying sexes, ages and weights appeared equally likely to consume baits. CONCLUSIONS: Encapsulated liquids can be delivered to feral pigs within baits, should the need to vaccinate feral pigs for fertility or disease management arise. High baiting intensities may be required.

Field evaluation of melatonin implants to advance the breeding season in 1-year-old farmed red deer hinds.

The efficacy of controlled-release melatonin implants to advance the onset of the breeding season was assessed in 1-year-old red deer hinds on five commercial deer farms in various localities in the North Island of New Zealand. Between 44 and 60 hinds in each of six herds were equally divided among treatment and control groups at each site. Melatonin treatment commenced between 27 November and 16 December and was achieved by the subcutaneous administration of two 18 mg melatonin implants. Three doses were given at about 30 day intervals. Two adult stags for each hind group were treated with three 18 mg melatonin implants concurrently on either two or three occasions. On each property, treated and control hinds were joined as one herd to treated stags commencing 30 January-10 February and concluding 15 May-2 June. The hinds in the four experimental herds underwent rectal ultrasound examination May-June to estimate conception rate and foetal age. Calving dates, hind and calf mortalities, weaning weights, and the antler growth cycle and harvesting data were recorded. Overall, treatment with melatonin resulted in an average advance of the median calving date of 22 days (range 12-36 days) when compared with untreated controls in the same herds. Pregnancy rates were 91.3-100% in treated hinds and 63.6-100% in untreated hinds. There were no differences in calf mortality or calf sex ratio between treated and untreated groups. No hind deaths could be attributed to melatonin treatment. The weaning weights of calves were 5.68 kg and 4.43 kg heavier for the male and female offspring of treated hinds respectively, compared with those of control hinds. Treated stags commenced rutting behaviour earlier than normal and the antler casting and growth cycle was advanced. Treatment resulted in advancement of the seasonal pattern of coat changes in hinds and stags, but no untoward side effects of the melatonin treatments were observed.

Effects of subcutaneous melatonin implants on reproductive seasonality of farmed fallow deer (Dama dama).

A total of 18 fallow does, including pubertal, non-pregnant and pregnant adult does (6 per class), each received a single subcutaneous implant containing 18 mg melatonin on 4 occasions at 29-30-day intervals from 10 November 1986 (approximately 120-day treatment period). A further 18 contemporary does served as herd-mate controls. Two adult fallow bucks were treated the same and were run with the does until 16 March. Thereafter, 1 of 4 control bucks was run with the does until 1 June. Of the 6 pregnant does receiving implants within the last 40 days of their gestation, 4 failed to lactate after parturition in December 1986. The remaining 2 does successfully reared their fawns, as did the 6 contemporary controls. Mean (+/- s.e.m.) dates of first oestrus in 1987 were 27.6 February (+/- 3.0 days) and 22.9 April (+/- 0.8 days) for all treated and all control does respectively (P less than 0.001). Pubertal does were generally later to exhibit first oestrus than were older does within their respective treatment groups. Return oestrus occurred only in 2 pubertal does (1 treated and 1 control) with remaining does conceiving to their first oestrus, as verified by plasma progesterone profiles. However, 5 (28%) of the treated does and 3 (17%) of the control does failed to maintain pregnancy and fawn in 1987. The mean (+/- s.e.m.) 1987 fawning date of the remaining does was 22.4 October (+/- 2.7 days) for the treated group (N = 13) and 13.1 December (+/- 0.8 days) for the control group (N = 15; P less than 0.001). Mean (+/- s.e.m.) gestation length of treated does (238.9 +/- 0.6 days) was significantly longer than that of control does (234.5 +/- 0.4 days; P less than 0.001). Of 13 fawns born to treated does, 4 (31%) died within 24 h of birth (mainly due to hypothermia) whereas all 15 fawns born to control does survived to weaning. Melatonin-treated bucks exhibited a marked advancement of neck muscle hypertrophy during the treatment period and displayed normal rutting activity (e.g. vocalization) in response to early oestrus in the treated does.

Inhibin secretion by the sheep ovary.

An in-vitro bioassay for inhibin based on FSH content or release by rat pituitary cells was validated for measuring inhibin activity in ovine plasma and lymph. Dose-dependent increases in inhibin activity were detected in peripheral plasma of 4 ovariectomized ewes 1 min after i.v. injections of ovine follicular fluid, and the half-life of inhibin in plasma for 2 ewes was 45 and 50 min, respectively. Inhibin was detected in ovarian lymph but not in ovarian or jugular venous plasma, even after treatment of ewes with PMSG to induce folliculogenesis. Destruction of visible follicles (greater than 0.5 mm diameter) on the ovaries of 4 PMSG-treated ewes by electrocautery was followed by a rapid and sustained decline in secretion of inhibin in ovarian lymph for up to 4 h. Ovarian lymph flow rates were either unchanged or slightly increased after cautery. Oestrogen concentrations in peripheral venous plasma declined within 15-30 min of cautery, but concentrations remained well above baseline. There was a significant decrease in peripheral progesterone concentrations in these same samples, but not until 2-3 h after cautery. FSH in peripheral plasma was depressed or non-detectable in PMSG-treated ewes and neither FSH nor LH concentrations in peripheral plasma were significantly altered up to 4 h after cautery of ovarian follicles. It is concluded that (a) antral follicles (greater than 0.5 mm) are the source of inhibin present in ovarian lymph, and (b) the ovarian lymphatic system is a route by which inhibin could reach the peripheral circulation, particularly in the luteal phase when ovarian lymph flow rates are high.

Structural requirements for steroid inhibition of sheep lymphocyte mitogenesis in vitro.

The inhibitory effects of different steroids and related compounds on sheep peripheral blood lymphocytes (PBL) during exposure to the mitogen, phytohemagglutinin (PHA), have been measured by the reduction of [3H]thymidine incorporation into DNA. Dose-response curves showed that a maximum (or near maximum effect) was achieved at a steroid concentration of 12.5 microM. At this dose 19 of 41 compounds significantly reduced thymidine incorporation by activated PBL (P less than 0.01 to P less than 0.001). The greatest reduction was observed with 17-hydroxyprogesterone (-59%, i.e. reduced by 59% compared with vehicle control, 100%) greater than androstenedione greater than epitestosterone greater than estradiol-3-methyl ether greater than 20 alpha-dihydroprogesterone greater than medroxyprogesterone acetate greater than 5 beta-pregnane-3,20-dione greater than 5 alpha-pregnane-3,20-dione (-24%). Among the steroids which showed the greatest inhibitory effect, 6 had a 4-en-3-one group in ring A, 4 had a saturated ring A (pregnane or androstane) and one had a 3-methyl ether group and a phenolic ring A. The wide range of structures represented by these inhibitory steroids suggests that inhibition of lymphocyte mitogenesis involves more than one mechanism.

Migration of leucocytes into the uterus after acute removal of ovarian progesterone during early pregnancy in the sheep.

The effects of acute deprivation of progesterone during early pregnancy on the occurrence of maternal leucocytes in uterine tissues was studied in sheep. Ovariectomy on day 21 of pregnancy resulted in a rapid influx of polymorphonuclear (PM) leucocytes into both caruncular and intercaruncular (glandular) endometrium but not into the myometrium. The infiltration had commenced by 24 hours after ovariectomy when the fetal membranes appeared histologically normal. By 72 hours after ovariectomy infiltration of PM leucocytes and degradation of the fetal syncytium were severe and extensive. The effect was specifically due to progesterone deprivation in pregnant animals since it was not seen in progesterone-treated ovariectomized pregnant animals or in non-pregnant animals ovariectomized in the mid luteal phase of the oestrous cycle. The PM leucocyte influx was not associated with changes in the number of intra-epithelial lymphocytes, the occurrence of which was only slightly reduced at the time of attachment. The results implicate maternal progesterone as a local anti-inflammatory agent within the gravid uterus and also show that total expulsion of lymphocytes from uterine epithelia at implantation is not a mechanism for immunoprotection of the sheep fetal allograft.

Influence of certain steroids on lymphocyte transformation in sheep and goats studied in vitro.

The effect of various steroids on lymphocyte transformation was tested with peripheral blood lymphocytes (PBL) from sheep and goats. Transformation was induced with phytohaemagglutinin, pokeweed mitogen and Concanavalin A, and by allogeneic lymphocytes (mixed lymphocyte culture). Progestagens, androgens and corticosteroids inhibited mitogen-induced transformation of lymphocytes from both species. With sheep PBL, progestagens and androgens inhibited transformation at high concentrations. Progesterone and its less active metabolites 5 alpha-pregnanedione and 20 alpha-dihydro-progesterone were equally inhibitory. Corticosteroids were more effective than other steroids at concentrations of less than 1 mumol/l. Oestrogens had relatively little effect with the exception of diethylstilboestrol which markedly enhanced sheep PBL responses to mitogen. Structural comparisons suggested that the most suppressive C-19 and C-21 steroids possessed 4-en-3-one configuration in ring A, and that inhibitory activity was enhanced by C-17 alpha substitution as in 17 alpha-hydroxyprogesterone. The steroid effects on PBL were largely unaffected by the reproductive status of the donor, were exerted during the early pre-replicative phase rather than at the time of new DNA synthesis, and were not attributable to cytoxicity nor to changes in intracellular thymidine pools. An exception was found with the non-steroidal oestrogen, diethylstilboestrol, which enhanced the response to mitogen-treated cultures of sheep lymphocytes at both early and late phases of the cell cycle. It is concluded that several naturally occurring steroids affect the responsiveness of PBL to mitogenic stimuli, and that progesterone and/or certain of its metabolites may be effective in vivo when present at the high concentrations found in the utero-ovarian lymphatic network draining the gravid uterus or at the trophoblast-maternal interface in the sheep and goat.

The influence of protein hormones and conceptus extracts on sheep lymphocyte transformation induced in vitro.

The study describes the effects of crude extracts of the fetal membranes of day 25 sheep conceptuses and of certain purified protein hormones and pregnancy-associated antigen on the mitogen-induced response of sheep peripheral blood lymphocytes (PBL) in vitro. A dose-dependent suppression of the proliferative response of PBL to phytohaemagglutinin, pokeweed mitogen and concanavalin-A was seen when cultures were supplemented with a soluble extract of fetal membranes. Preliminary characterization suggested that the suppressive agent was heat stable and dialysable. These properties distinguished the immunosuppressive component of membrane extracts from ovine pregnancy-associated antigen, which is heat labile and non-dialysable. However, both high and low molecular weight forms of ovine pregnancy associated antigen were also shown to inhibit lymphocyte transformation in vitro. In contrast, ovine luteinizing hormone, prolactin, growth hormone and human placental lactogen were inactive. The findings are consistent with the hypothesis that immunosuppressive substances are present in the gravid uterus during early pregnancy in the sheep.

Structure of trophoblast papillae on the sheep conceptus at implantation.

A study of 13-18 days old sheep conceptuses has consistently demonstrated the presence of multicellular protrusions (papillae) from the trophectoderm surface. These papillae were shown to be restricted to the embryonic region of conceptuses flushed out of the uterus. After perfusion fixation of the uterus on day 16 of pregnancy, the papillae can be observed penetrating well down into the lumina of the uterine glands. The papillae have not been observed at or after day 20. It is suggested that the papillae may play an important but transient role in anchoring the embryonic region of the conceptus against the uterine epithelium to allow the initiation of the cellular changes characteristic of implantation.

The nature and role of pregnancy-associated antigens and the endocrinology of early pregnancy in the ewe.

Depite descriptions of many of the physiological events of early pregnancy in the ewe, the way in which the immunological and endocrine adjustments are brought about is not well understood. Obviously, specific effects--for example, maintenance of the corpus luteum--are brought about by the presence of a conceptus in the uterus. This has led to a search for substances produced by the conceptus or induced by the presence of the conceptus in the uterus which could be involved in establishing pregnancy. This paper describes the presence in sheep of substances associated with pregnancy and discusses the origin and characterization of these substances and their role in ovine pregnancy.