Liver blood flow and metabolic clearance rate of progesterone in sheep

To study the inverse relationship between feed level and concentrations of peripheral plasma progesterone, 36 ovariectomised ewes were fed rations at levels calculated to maintain liveweight (M). On the seventh day, the ewes were given an intravenous infusion of progesterone and the metabolic clearance rate (MCR) was calculated. The ewes were then randomly allotted to receive either , M or 2M rations for seven days at which time the infusion and blood sampling schedules were repeated. The mean (SE) MCR of infused progesterone in ovariectomised ewes fed either , M or 2M rations for seven days was 7·1 (0·59), 9·9 (1·64 and 13·0 (1·19) litre h⁻¹ kg⁻¹ of liveweight, respectively. Differences in MCR of progesterone between ewes fed and 2M rations were significant (P<0·05). The inverse relationship between level of feed intake and plasma progesterone concentration was attributed to differences in clearance rate of progesterone rather than to changes in the entry rate of the hormone into the blood.     

Strategies for Using eFSH for Superovulating Mares

The standard treatment for superovulation of mares is to administer equine follicle-stimulating hormone (eFSH) for 4 to 5 days to stimulate multiple follicles and human chorionic gonadotropin (hCG) to induce synchronous ovulations. Objectives of this study were: (1) to determine whether a short-term (3-day) eFSH treatment protocol would result in similar ovulation and embryo recovery rates compared with the standard eFSH protocol; (2) to determine the efficacy of a decreasing dose of eFSH (step-down protocol) on ovulation rate and embryo recovery; (3) to compare the efficacy of hCG and recombinant equine luteinizing hormone (reLH) for inducing ovulation in FSH-treated mares; and (4) to compare embryo recovery rates and embryo size when mares are flushed at 6.5 or 7.0 days after ovulation. Forty light-horse mares were used in 2005 (experiment 1) and 20 different mares were used in 2006 (experiment 2). In experiment 1, mares were randomly assigned to one of three treatment groups: (1) untreated controls, (2) standard eFSH treatment (12.5 mg intramuscularly twice daily), and (3) 3-day eFSH treatment. In experiment 2, mares were randomly assigned to one of four treatments: (1) untreated controls, (2) standard eFSH protocol, (3) 3-day eFSH treatment, and (4) step-down eFSH treatment (12.5 mg twice daily day 1, 8.0 mg twice daily day 2, 4.0 mg twice daily day 3). Within each treatment, mares were given either hCG (2,500 IU) or equine LH (750 mg, EquiPure LH; reLH) to induce synchronized ovulations. Embryo recovery was performed either 6.5 or 7.0 days after ovulation. In experiment 1, numbers of preovulatory follicles and ovulations were less for mares in the 3-day treatment group than the standard group, but were greater than for controls. Embryo recovery per flush was higher in the standard group (2.6) than the 3-day eFSH treatment (0.8) or control groups (0.8). In experiment 2, the number of preovulatory follicles and number of ovulations were greater in the standard and 3-day treatment groups than in control and step-down groups. The percent embryo recovery per ovulation and mean embryo grade were similar for all groups; however, the embryo recovery per flush was higher for mares in the standard treatment than controls (1.3 vs 0.6) but was similar to the 3-day (1.1) and step-down (0.8) treatments. Embryo recovery was similar for flushes performed on days 6.5 and 7.0 post-ovulation. The percentage of control mares ovulating within 48 hours in response to hCG or reLH was similar. In contrast, a higher percentage of eFSH-treated mares ovulated within 48 hours in response to reLH than hCG (92% vs 71%). In both years, the 3-day eFSH treatment protocol resulted in a greater number of preovulatory follicles and a greater number of ovulations than untreated controls. Unfortunately, the increased ovulation rate for mares administered eFSH for 3 days did not result in a greater number of embryos recovered per flush in either year. Use of a step-down eFSH treatment protocol resulted in fewer preovulatory follicles, fewer ovulations, and fewer embryos as compared with the standard eFSH treatment. In conclusion, the standard eFSH treatment resulted in a greater embryo recovery rate per cycle than either the 3-day or step-down treatment protocols. Recombinant equine LH was more effective than hCG in causing ovulation in eFSH-treated mares.     

The mitigation hierarchy for sharks: A risk‐based framework for reconciling trade‐offs between shark conservation and fisheries objectives

Sharks and their cartilaginous relatives are one of the world's most threatened species groups. The primary cause is overfishing in targeted and bycatch fisheries. Reductions in fishing mortality are needed to halt shark population declines. However, this requires complex fisheries management decisions, which often entail trade‐offs between conservation objectives and fisheries objectives. We propose the mitigation hierarchy (MH)—a step‐wise precautionary approach for minimizing the impacts of human activity on biodiversity—as a novel framework for supporting these management decisions. We outline a holistic conceptual model for risks to sharks in fisheries, which includes biophysical, operational and socioeconomic considerations. We then demonstrate how this model, in conjunction with the MH, can support risk‐based least cost shark conservation. Through providing examples from real‐world fishery management problems, we illustrate how the MH can be applied to a range of species, fisheries and contexts, and explore some of the opportunities and challenges hereto. Finally, we outline next steps for research and implementation. This is important in the context of increasing international regulation of shark fishing and trade, which must lead to reductions in shark mortality, while managing trade‐offs between conservation objectives and the socioeconomic value of fisheries.     

Influence of bacterial challenge and long-term progesterone on endometritis of mares

Progress in treatment of endometritis in mares has been impeded by lack of an experimental model. This study tests the hypothesis that exposure of a mare's uterus to bacteria, while being treated with progesterone, will result in a compromised uterine defense after progesterone has been withdrawn. Ten mares were administered progesterone for 8 months and inoculated at the onset of treatment with a 5 x los colony forming units of(CFU) of Streptococcuszooepidemicus into the uterus. Mares were re-inoculated to maintain uterine infection, if necessary. Ten uninoculated mares with normal uteri served as controls. After the end of progesterone treat- ment all mares (treated and controls) experienced a normal estrous cycle and were inoculated with 5 x l0s CFU of Streptococcus zooepidemicus. Results of reproductive evalu- ations performed on days 2, 7 and 12 after bacterial inoculation were similar (P>0.05) for treated and controls. Pregnancy rates for treated and controls were also similar (P>0.05). Thus, the treatment evaluated in this study did not cause an alteration in the mare's ability to resolve endometritis.     

Effect of cooling rate and cryoprotectant on the cryosurvival of equine spermatozoa

Cryosurvival of cells is reduced if the cooling rate used is suboptimal. If cells cool too rapidly, intracellular water will freeze, causing intracellular ice crystals. However, if spermatozoa are cooled too slowly, excessive cellular dehydration occurs, causing irreversible damage to cellular compartments. In addition, cryoprotectants are added to the freezing diluent to protect cells from damage during cryopreservation. This study was conducted to determine the optimal cooling rate for stallion spermatozoa frozen in the presence of three different cryoprotectants. Spermatozoa were frozen in a skim milk, egg yolk diluent containing 4% glycerol, and ethylene glycol or dimethyl formamide at 10 different cooling rates ranging from 5°C/min to 50°C/min. The percentage of viable spermatozoa was higher for spermatozoa cooled at 10°C/min than at 50°C/min (P < .05). Spermatozoa frozen using glycerol as the cryoprotectant had higher percentages of motile and progressively motile spermatozoa compared with spermatozoa frozen using the other two cryoprotectants (P < .05). In conclusion, the cryosurvival of stallion spermatozoa is similar when cooling rates of 5°C/min to 45°C/min are used, and when 4% cryoprotectant is used, glycerol is a more effective cryoprotectant than ethylene glycol or dimethyl formamide.