Kristina Odensvik

THE USAGE OF VETERINARY ANTIBACTERIAL DRUGS FOR MASTITIS IN CATTLE IN NORWAY AND SWEDEN DURING 1990-1997

The prescribing patterns and annual incidence of use of antibacterial drugs for the treatment of mastitis in cattle in Norway and Sweden during the period 1990-1997 were estimated from drug wholesaler statistics. Although the drugs included in this study are also used in other species and/or other indications, mastitis in cattle is by far the most-common indication for their use. We used these sales figures to evaluate trends in the use of antibacterial drugs and changes in the incidence of treatment in bovine mastitis in Norway and Sweden. To facilitate comparisons (correcting for differences in activity and dosage) between the relative proportions of antibacterial drugs used in bovine mastitis, we introduced defined daily dose cow (DDDcow) as unit of measurement. Tentative DDDcow for the various injectable drugs were derived from doses recommended in Norway and Sweden. For intramammary drugs administered in the form of single-dose applicators, one applicator was defined as the DDDcow. The prescribing patterns of antibacterial drugs in bovine mastitis in Norway and Sweden during the study period seemed to be influenced by treatment policies, substances and formulations approved and treatment cost; length of the withdrawal period also seemed to play a role.

Utero-ovarian relationships during the bovine postpartum period

Abstract During the postpartum period in the cow a massive PGF 2α release occurs. This release is negatively correlated to uterine involution in normal cows and positively correlated in cows with uterine infections. The PG release seems to inhibit ovulation/corpus luteum formation. By treatment with PGF 2α the uterine involution can be promoted. No effect, or a slight positive effect, is seen after treatment with prostaglandin synthesis inhibitors on the speed of uterine involution. Resumption of ovarian activity is positively correlated to uterine involution. Prostaglandin F 2α can also stimulate onset of ovarian cyclicity.

The effect on luteolysis by intensive oral administration of flunixin granules in heifers

The objective of the study was to investigate whether oral administration of flunixin meglumine (FM) in the form of granules could prolong the functional life of the corpus luteum in heifers. Previous studies have shown that intensive, i.e. four times daily parental administration of FM can postpone luteolysis. Twelve heifers received an oral dose of 2.2 mg flunixin per kg body weight. Three dosing regimes were used; twice (n = 2), thrice (n = 4) and four times daily (n = 6). The 9-day-treatment period started on Day 14/15 of the oestrous cycle. Blood samples were collected twice daily during the entire experimental period. Frequent samples were withdrawn from Day 14/15 for 10 and 15 days in the control and treatment oestrous cycles, respectively, at 0600, 0800, 1000, 1200, 1400, 1600, 1800 and at 2000 h. The plasma was analysed for the content of the main metabolite of PGF2 alpha, i.e. 15-ketodihydro-PGF2 alpha, and progesterone. A control cycle preceded the treatment cycle so that each heifer acted as its own control. The length of the oestrous cycle was significantly increased when FM was administered thrice, from 18-22 days to 20-24 days (P < 0.05), and four times daily, from 18-21 days to 25-27 days (P < 0.01), but not in the twice daily dosing regime (one-way ANOVA). When FM was administered twice and thrice, luteolysis occurred during treatment. However, when the four times daily regime was used, luteolysis was obtained when the treatment had terminated. No changes in progesterone levels were recorded, although the luteal phase increased when the oestrous cycle length was prolonged. The number of PG-pulses decreased significantly, from 6-12 pulses to 0-3 pulses (P < 0.01), when FM was administered four times daily. A reduction was also observed when heifers received the drug thrice, but the decrease was not significant. The oral route of administration was found to be as effective as the parental one to affect the mechanism responsible for luteolysis in heifers. However, to inhibit and postpone luteolysis, administration of FM four times daily is a necessity. Our results show that oral administration of FM in the bovine species can be of value both in research as well as in the clinic, e.g. to support the luteal function.

Effect of flunixin during asynchronous embryo transfer in the heifer

Abstract Flunixin meglumine (FM), a potent non-steroidal anti-inflammatory drug, was administered to heifers during asynchronous embryo transfer (i.e. Day 7 embryos were transferred non-surgically to Day 10 recipients). Flunixin was injected during a 10 day period, beginning on Day 14 (Day 0 was the first day of standing oestrus). The dose was 2.2 mg kg −1 injected intramuscularly, either twice daily (FM×2) ( n = 5) or four times daily (FM×4) ( n = 6). The control group ( n = 5) was not treated with FM. The flunixin treatment resulted in decreased synthesis of prostaglandin (PG) F 2 α , which was seen as a reduction of the PG-metabolite level (15-ketodihydro-PGF 2 α ) close to the limit of detection. The synthesis of PGF 2 α was affected, but never totally suppressed, not even when the intensive dosage was used. The pulsatile PG release pattern was impaired but present in the FM×2 group and luteolysis occurred. In the FM×4 group only sporadic peaks were seen during treatment and luteolysis was postponed. After the treatment, PG pulses appeared and luteolysis was accomplished. In addition, the oestrous cycle was prolonged, as a consequence of the intensive treatment. The ultrasonographic examinations of the uterus showed non-echogenic areas from Day 17 onwards, indicating embryonic tissue. These areas disappeared after 1–3 days. Thereafter, no non-echogenic areas could be detected until oestrus occurred 5–8 days later. Our results show that Day 7 embryos transferred to an advanced uterus (+3 days) survive initially, but are unable to implant, despite the inhibition of luteolysis and prolongation of the oestrous cycle by flunixin.

Endogenous prostaglandin secretion during cloprostenol-induced abortion in mares

Abstract Repeated administration of prostaglandin is the treatment of choice for the termination of pregnancy in mares more than 40 days pregnant. Even though it is well documented that PGF-2α or analogue needs to be administered every 12–24 h for successful induction of abortion, little is known about the underlying endocrine changes and the mechanism by which abortion occurs. The aim of this study was to characterize the changes in PGF-2α, progesterone and estrogen secretion during prostaglandin-induced abortion. Six mares, 82–102 days pregnant, were treated daily with 250 μg cloprostenol, blood was collected at 1-h intervals until fetal expulsion and pregnancy examination was performed daily. Four mares, 92–97 days pregnant, received no treatment but were subjected to the same hourly blood collections and daily genital examinations described for cloprostenol-treated mares for 3 days. Mean time from first cloprostenol administration until fetal expulsion was 48.6 ± 5.6 h and required 2.8 ± 0.2 cloprostenol administrations. In all mares, progesterone concentrations decreased in a near linear manner after the first cloprostenol administration and were invariably low (1.3 ± 0.2 ng ml −1 , mean ± SEM) at the time of fetal expulsion. Mean estrogen secretion remained unchanged until 5 h before fetal expulsion and then decreased rapidly to non-pregnant levels. Endogenous PGF-2α secretion rate increased with each cloprostenol administration and culminated in sustained PGF-2α secretion which persisted until fetal expulsion was completed. From these results we conclude that cloprostenol-induced abortion is associated with endogenous PGF-2α secretion, fetal expulsion coincides with sustained PGF-2α secretion and low progesterone concentrations and plasma estrogen concentrations remain unchanged until hours before fetal expulsion.