Hemostatic profile during late pregnancy and early postpartum period in mares

Hemostasis is a physiological process that prevents excessive blood loss and represents a protective mechanism at the time of delivery. Peripartum hemorrhage is a recurring hazardous condition to mare's health; therefore, we aimed to study mares' hemostatic profile to investigate whether physiological adjustments occur during late pregnancy and early postpartum. Fifteen pregnant mares have been monitored from the 34th week of pregnancy until the third week after foaling. Fifteen nonpregnant mares were used as control group. Jugular blood samples were analyzed for platelet count (Plt), prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen (Fb). Platelet count showed significant changes at foaling (P < 0.05) and a negative correlation (r = −0.968; P = 0.032) with postpartum. Prothrombin time changed (P < 0.05) showing a significant correlation (r = 0.675; P = 0.016) with late pregnancy. Fibrinogen concentrations changed throughout the experimental period (P < 0.0001). The linear regression model revealed a positive correlation (r = 0.9210; P < 0.0001) between Fb and late pregnancy and a negative correlation (r = −0.9583; P = 0.042) between Fb and early postpartum. The shortening in PT recorded in the imminence of parturition along with the increase in Plt and Fb at foaling might reflect a physiological hypercoagulable state that constrains excessive bleeding, enhancing mares' odds of surviving. Our research improves the knowledge about blood coagulation in periparturient mares providing specific information on routine coagulation tests that may support in monitoring mare's hemostatic profile during late pregnancy and early postpartum.     

Role of PGF2α in luteolysis based on inhibition of PGF2α synthesis in the mare

The effects of inhibition of PGF2α synthesis on luteolysis in mares and on the incidence of prolonged luteal activity were studied in controls and in a group treated with flunixin meglumine (FM), a PGF2α inhibitor (n = 6/group). The FM was given every 8 hours (1.0 mg/kg) on each of Days 14.0 to 16.7. Concentration (pg/mL) of PGF2α metabolite averaged over 8 hours of hourly blood sampling at the beginning of each day, was lower in the FM group than in the controls on Day 14 after ovulation (6.7 ± 1.3 vs. 13.8 ± 2.9, P < 0.05), Day 15 (15.0 ± 3.9 vs. 35.2 ± 10.4, P < 0.10), and Day 16 (21.9 ± 5.7 vs. 54.7 ± 11.4, P < 0.03). Concentration (ng/mL) of progesterone (P4) was greater in the FM group than in the controls on Day 14 (10.1 ± 0.9 vs. 7.7 ± 0.9, P < 0.08), Day 15 (9.2 ± 1.0 vs. 4.3 ± 1.0, P < 0.008), and Day 16 (5.6 ± 1.6 vs. 1.2 ± 0.4, P < 0.02). The interval from ovulation to the beginning of a decrease in P4 and to the end of luteolysis (P4 < 1 ng/mL) was each delayed (P < 0.03) by ∼1 day in the FM group. Intervals involving the luteal phase were long (statistical outliers, P < 0.05) in two mares in the FM group, indicating prolonged luteal activity. Results supported the hypotheses that (1) inhibition of PGF2α synthesis interferes with luteolysis in mares and (2) inhibition of PGF2α at the expected time of luteolysis may lead to prolonged luteal activity.     

Doppler sonography of the uterine and ovarian arteries during a superovulatory program in horses

The aim of the present study was to investigate the effects of a gonadotropin treatment to induce superovulation on ovarian and uterine blood flow and its relationship with steroid hormone levels and ovarian response in mares, using color Doppler sonography. Each of six mares were examined sonographically in five cycles for 3 d (t1 to t3) during the follicular development phase (FDP) beginning at a follicle size of ≥ 22 mm, and for 4 d (D-4 to D-1; D0 = Ovulation) in the preovulatory phase (POP). After each examination, total estrogens (E_tot) and progesterone (P₄) levels were determined in peripheral plasma. Cycles 1, 3, and 5 (c₁, c3, c5) were unstimulated cycles (USC); in c2 and c4, the mares were stimulated (SC) with eFSH and inseminated when in estrus at 12 and 24 h after hCG administration. Embryo recovery was performed 6.5 d post ovulation. Cycle 5 c5 was an unstimulated cycle with hCG treatment, insemination, and embryo recovery. Ovarian and uterine blood flow was quantified by the blood flow volume (BFV) and the pulsatility index (PI) in ovarian and uterine arteries. The mean number of ovulations and developing CL was 1.3 ± 0.4 in USC and 4.4 ± 3.1 in stimulated cycles (SC) with no difference (P ≥ 0.05) between the ovaries within mares. No difference (P > 0.05) was observed in utBFV and utPI during FDP between USC and SC, but during POP, utPI was lower (P < 0.05) and utBFV higher (P < 0.001) in SC than USC. The ovBFV was higher (P < 0.01) and ovPI lower (P < 0.05) in SC compared to USC. All uterine and ovarian blood flow parameters were related to the number of developing follicles in SC. Parameters utPI (r = −0.67; P < 0.001) and ovPI (r = −0.53; P < 0.001) were negatively correlated with the number of ovulations on t3, and with the number of collected embryos on t3 (utPI: r = −0.81; P < 0.001), D-4 (utPI: r = −0.64; P < 0.0001), and D-1 (ovPI: r = −0.41; P < 0.01). P₄ levels were not positively correlated with utBFV (P > 0.05), but E_tot concentrations (D-4: r = 0.790; D3: r = 0.639; P < 0.001; D-1: r = 0.48; P < 0.001) and ovBFV from D-4 to D-1 (r = 0.64; P < 0.001) in SC were. The results of the present study show that in mares treatment with gonadotropins to induce superovulation is associated with a marked increase in uterine and ovarian perfusion, concurrent with the development of multiple follicles and an increase in E_tot levels. The increased blood flow seems to be related to the effectiveness of ovarian response to stimulation.     

Fenugreek (Trigonella foenum-graecum L.) as an alternative forage for dairy cows

Fenugreek is a novel forage crop in Canada that is generating interest as an alternative to alfalfa for dairy cows. To evaluate the value of fenugreek haylage relative to alfalfa haylage, six, second lactation Holstein cows (56 ± 8 days in milk), which were fitted with rumen cannulas (10 cm i.d., Bar Diamond Inc., Parma, ID, USA) were used in a replicated three × three Latin square design with 18-day periods. Diets consisting of 400 g/kg haylage, 100 g/kg barley silage and 500 g/kg concentrate on a dry matter (DM) basis were fed once daily for ad libitum intake. The haylage component constituted the dietary treatments: (i) Agriculture and Agri-Food Canada F70 fenugreek (F70), (ii) Crop Development Center Quatro fenugreek (QUAT) and (iii) alfalfa (ALF). DM intake (DMI), milk yield and milk protein and lactose yields were higher (P < 0.001) for cows fed ALF than fenugreek (FEN, average of F70 and QUAT). Milk fat of cows fed FEN contained lower concentrations of saturated, medium-chain and hypercholestrolemic fatty acids (FAs; P < 0.05) than that of cows fed ALF. Apparent total tract digestibility of DM and nutrients was not affected by treatments. Similarly, individual ruminal volatile FA concentrations and rumen pH (5.9) were not affected by treatments. Rumen ammonia-N concentration was higher for FEN than ALF (P < 0.001). Estimates of neutral detergent fiber (NDF) passage rate (P < 0.05) and NDF turnover rate (P < 0.001) in the rumen were higher for ALF than FEN. Our results suggest that although the digestibility of the FEN diets was not different from that of the ALF diet, fenugreek haylage has a lower feeding value than ALF for lactating dairy cows due in part to lower DMI and subsequently lower milk yield.     

Effects of body condition and leptin on the reproductive performance of Lusitano mares on extensive systems

The aim of this study was to investigate the effects of body condition (BC), BC changes, and plasma leptin concentrations on the reproductive performance of Lusitano broodmares on extensive systems. Data from 119 mares (ranging from 4 to 22 years of age) were collected over a period of four consecutive breeding seasons. Each case was considered as one foaled mare bred in 1 year. Body condition changes at conception (ΔBCScon) showed a strong effect on fertility at the first two postpartum estrous cycles and a significant interaction with body condition score at conception (BCScon) was observed (P < 0.01). The best fertility results were obtained with positive and greater ΔBCScon. The best predictive value of fertility (91%) was achieved when the BCScon was 3.0 and ΔBCScon was 0.375. Global foaling rate for the 4-year period was 74.5%. Mean foaling interval and gestation length were, respectively, 368.0 ± 2.8 and 340.3 ± 1.0 days. Gestation length was influenced by the month of foaling (P < 0.05) and decreased as mares got older (P < 0.01). The number of estimated estrous cycles per live foal was 1.78 ± 0.12, including foal heat ovulation. Leptin was correlated with BCS (0.41; P < 0.001), but in the present study, plasma leptin concentrations on late gestation and early lactation did not influence fertility results. At 90 days of age, lower growth performances were obtained in foals which dams presented negative BCS changes on the first 3 months of lactation (P < 0.05). In conclusion, BC changes at early postpartum period influence the reproductive efficiency of broodmares and the growth of their suckling foals. These findings are important to help breeders on management options concerning feeding strategies in the Lusitano production systems and others under similar conditions.     

Susceptibility to persistent breeding-induced endometritis in the mare: relationship to endometrial biopsy score and age, and variations between seasons

The objectives were to: (1) investigate the associations of age and endometrial biopsy score with uterine fluid retention after insemination; and (2) determine if a strict classification of susceptibility to persistent breeding-induced endometritis (PBIE) based on biopsy score, endometrial cytology, and fluid retention after inseminations, is consistent over subsequent breeding seasons. In Experiment 1, 57 mares were inseminated with 10⁹ freeze-killed sperm during estrus and evaluated for uterine fluid retention 48 h and 96 h after insemination. Comparisons were made between fluid retention and biopsy score or age. In Experiment 2, a subset of 14 mares was classified for susceptibility to persistent breeding-induced endometritis in two subsequent breeding seasons. Biopsy score and age were associated with fluid retention (P < 0.001). In addition, age was related to biopsy score (P < 0.001). Of the mares examined for susceptibility, 36% (5 of 14) changed status during subsequent seasons. Three mares changed to a more severe classification (intermediate to susceptible, or resistant to intermediate), whereas two mares changed to a less severe classification (susceptible to intermediate).     

Comparison of muscle fatty acid composition and lipid stability in lambs stall-fed or pasture-fed alfalfa with or without sainfoin pellet supplementation

Currently, consumers are increasingly interested in obtaining high-quality and healthy lamb meat. Compared to grain-based diets, dietary forage legumes such as alfalfa and condensed tannin (CT)-rich sainfoin increase the levels of polyunsaturated fatty acids (PUFAs) that are beneficial for health in lamb meat thanks to their high content in PUFA and/or their impact on ruminal biohydrogenation. However, they can therefore adversely affect its oxidative stability. Thus, the impact of dietary forage legumes on lamb longissimus thoracis (LT) muscle FA composition and their stability to peroxidation was studied in 36 Romane lambs grazing alfalfa (AF; n = 12) or alfalfa plus daily supplementation with CT-rich sainfoin pellets (AS; n = 12; 15 g DM/kg BW, 42 g CT/kg DM) or stall-fed concentrate and grass hay indoors (SI; n = 12). Lambs were slaughtered at a mean age of 162 ± 8.0 days after an average experimental period of 101 ± 8.1 days. Forage legumes-grazing lambs outperformed SI lambs in LT nutritional quality, with more conjugated linoleic acids and n-3 PUFAs, especially 18:3n-3, eicosapentaenoic and docosahexaenoic acids (P < 0.001), and thus lower n-6 PUFA/n-3 PUFA and 18:2 n-6/18:3 n-3 ratios (P < 0.001). Peroxidizability index was higher (P < 0.001) in LT muscle of forage legumes-grazing lambs. Concurrently, two endogenous antioxidant enzyme activities, superoxide dismutase and glutathione peroxidase, were, respectively, similar and lower (P < 0.001) for forage legumes-grazing compared with SI lambs. A lower vitamin E level in SI lambs compared with forage legumes-grazing lambs (1.0 v. 3.8 mg/g, P < 0.001) could explain that malondialdehyde content, a marker of lipid oxidation intensity, was 0.63 µg/g in SI after 8 days in aerobic packaging conditions, whereas it remaining steady at 0.16 µg/g in forage legumes-grazing lambs. Dietary forage alfalfa thus improved FA composition of lamb LT muscle and their stability to oxidation when compared to SI lambs. However, supplementation of alfalfa-grazing lambs with CT-rich sainfoin pellets did not affect the nutritional quality of LT muscle FAs.     

Production of a mitochondrial-DNA identical cloned foal using oocytes recovered from immature follicles of selected mares

Cloned animals possess mitochondria derived from the host ooplast, which typically differ genetically from those of the donor. This is of special concern to horse breeders, as maternal lines are prized and athletic performance is a key factor in genetic value. To evaluate the feasibility of producing mitochondrial-identical cloned foals, we collected oocytes from immature follicles of two mares, BL and SM, maternally related to the donor stallion. In vitro matured, enucleated oocytes were treated with roscovitine-synchronized donor cells and blastocysts were transferred transcervically to recipient mares. In Mare BL, 10 aspiration sessions yielded 45 oocytes, of which 12 matured and seven were successfully recombined. One blastocyst was produced, which did not yield a pregnancy. In Mare SM, three aspiration sessions yielded 53 oocytes, of which 27 successfully recombined. These were assigned to either Scriptaid or Scriptaid plus Vitamin C treatments for the first 12 to 16 hours of embryo culture. Two blastocysts were produced from each treatment. One pregnancy was established after transfer from the Scriptaid treatment. This resulted in a viable foal whose genomic DNA and mitochondrial DNA matched to those of the donor animal. These results indicate that production of mitochondrial-identical cloned foals can be achieved using oocyte recovery from a very small number of selected mares. Despite mitochondrial homogeneity, the results varied with mare; Mare BL yielded both significantly fewer oocytes per aspiration session (P < 0.001) and significantly fewer reconstructed oocytes per oocyte recovered ( P < 0.001) than did Mare SM.     

Effects of prostaglandin F2α, cloprostenol and fenprostalene on uterine clearance of radiocolloid in the mare

Uterine clearance of radiocolloid was measured by scintigraphy in 5 reproductively normal mares and in 4 mares exhibiting a delay in uterine clearance (DUC) after administration of PGF_2α, cloprostenol or fenprostalene. Scintigraphy studies were performed on the second or third day of estrus during 3 consecutive estrous cycles. Drugs, PGF_2α (5 mg IM), cloprostenol (CLO; 2mg IM) or fenprostalene (FEN; 250 μg subcutaneously) were given in random order, with only 1 drug given each estrus. Treatment response curves were generated, and the effect of each drug on uterine clearance of radiocolloid was compared to the clearance of radiocolloid when no drug was given and between treatments. In reproductively normal mares, CLO and PGF caused a rapid clearance of radiocolloid within 60 min (P < 0.01), with <25% of the initial dose of radiocolloid (% IDR) remaining by 120 min. Mean percentage of IDR at 120 min when no drug was given was 39% ± 4. Response of reproductively normal mares to FEN varied, with 3 mares clearing > 85% and 2 mares clearing <35%. In mares exhibiting DUC, all 3 drugs (CLO, PGF and FEN) caused rapid clearance of radiocolloid from the uterus by 60 min (P < 0.0001). Mares cleared significantly more colloid after treatment with CLO at 60 and 120 min than after PGF (P < 0.001). In conclusion, CLO appears to be the best drug of the 3 tested for stimulating clearance of intrauterine fluid since variation in response was observed following treatment with PGF and FEN.     

Changes in cortisol release and heart rate and heart rate variability during the initial training of 3-year-old sport horses

Based on cortisol release, a variety of situations to which domestic horses are exposed have been classified as stressors but studies on the stress during equestrian training are limited. In the present study, Warmblood stallions (n = 9) and mares (n = 7) were followed through a 9 respective 12-week initial training program in order to determine potentially stressful training steps. Salivary cortisol concentrations, beat-to-beat (RR) interval and heart rate variability (HRV) were determined. The HRV variables standard deviation of the RR interval (SDRR), RMSSD (root mean square of successive RR differences) and the geometric means standard deviation 1 (SD1) and 2 (SD2) were calculated. Nearly each training unit was associated with an increase in salivary cortisol concentrations (p < 0.01). Cortisol release varied between training units and occasionally was more pronounced in mares than in stallions (p < 0.05). The RR interval decreased slightly in response to lunging before mounting of the rider. A pronounced decrease occurred when the rider was mounting, but before the horse showed physical activity (p < 0.001). The HRV variables SDRR, RMSSD and SD1 decreased in response to training and lowest values were reached during mounting of a rider (p < 0.001). Thereafter RR interval and HRV variables increased again. In contrast, SD2 increased with the beginning of lunging (p < 0.05) and no changes in response to mounting were detectable. In conclusion, initial training is a stressor for horses. The most pronounced reaction occurred in response to mounting by a rider, a situation resembling a potentially lethal threat under natural conditions.     

Preference by sheep for endophyte-infected tall fescue grown adjacent to or at a distance from alfalfa

Two experiments were conducted to assess preference by sheep for endophyte-infected tall fescue growing in monoculture at least 5 m away from alfalfa (fescue-middle (FM)) over endophyte-infected tall fescue growing adjacent (0.2 to 1 m; fescue–alfalfa (FA)) to alfalfa (FA), and the effect of legume scent on preference for endophyte-infected tall fescue. In Experiment 1, 10 six-month-old lambs were offered for 12 days a choice of freshly harvested FA and FM. On days 13 and 14, lambs were offered the same choice, except cages (to allow access only to scent) containing freshly harvested alfalfa were put in the feeders containing FA, whereas cages containing freshly harvested FM were included with the feeders containing FM. Forage intake was measured 1 h after feeding and at three consecutive 2-h intervals thereafter. FA contained greater (P<0.002) concentrations of the alkaloid ergovaline (360±27 ppm) and CP (8±0.4%) than FM (219±27 ppm and 6±0.4%, respectively). Lambs preferred (P<0.05) FA to FM during the 1^st hour of feeding, but the differences became smaller and disappeared in later feeding periods (P<0.005). Lambs offered FA with alfalfa scent or FM with FM scent preferred (P<0.05) FA but only on the 2^nd day. In Experiment 2, 10 six-month-old lambs were offered a choice of FM with cages (to allow access only to scent) containing freshly harvested alfalfa or FM for 8 days. During the following 4 days, FM in the cages was replaced with freshly harvested sainfoin. Preference was greater (P<0.05) for FM offered with alfalfa scent than for FM offered with FM scent only on days 4 and 8. When lambs were offered FM with alfalfa or sainfoin in cages, they preferred (P<0.05) tall fescue with sainfoin scent over fescue with alfalfa scent, but intake was variable across hours and days (P<0.001). It is concluded that (1) lambs adjusted their intake of and preference for FA and FM over successive feeding bouts within each day, likely owing to an attempt to balance intakes of nutrients and alkaloids and (2) olfactory cues influenced preference, but to a lesser extent than nutrients and alkaloids in endophyte-infected tall fescue.     

Administration of sulpiride or domperidone for advancing the first ovulation in deep anestrous mares

Since results with using sulpiride and domperidone are conflicting and since both have not been tested at the same time, the aim of this study was to compare the efficacy of these substances for the induction of ovulation in deep anestrous mares in the same experimental conditions and to determine their fertility after artificial insemination (AI) at the induced estrus. Twenty-six non-pregnant, non-lactating standardbred anestrous mares were randomly assigned to three groups and treated daily for 25 days (from February 3rd to February 28th) with either sulpiride (1 mg/kg of body weight im SID, n = 10), or domperidone (1 mg/kg po SID, n = 10); 6 animals were used as control. The beginning of the transition period and the first ovulation were hastened in sulpiride (16.4 ± 0.8 days) but not in domperidone (46.0 ± 3.3 days) treated mares (P < 0.05). The diameter of the largest follicle was affected by treatment, time and interaction of treatment-by-day (P < 0.05) and significantly increased in the sulpiride group (P < 0.05). Although a main effect of treatment on plasma LH concentration was not observed (P = 0.06), time and interaction of treatment-by-day were statistically significant (P < 0.05). The interval from the beginning of treatment to first ovulation was shorter (P < 0.05) in the sulpiride group (36.9 ± 2.5 days) than in the domperidone (74.7 ± 3.3 days) and control (81.4 ± 3.1) groups. The establishment of pregnancy was significantly (P < 0.05) hastened in sulpiride (61.0 ± 35.2 days) but not in domperidone (83.0 ± 44.0 days) treated mares. Treated mares not pregnant after the first AI, showed normal estrous cycles with regular interovulatory intervals (P > 0.05). It was concluded that sulpiride is effective in advancing the beginning of transition period and the first ovulation whereas domperidone is successful only in some mares.     

In vitro embryo production in goats: Slaughterhouse and laparoscopic ovum pick up–derived oocytes have different kinetics and requirements regarding maturation media

A total of 3427 goat oocytes were used in this study to identify possible differences during in vitro embryo production from slaughterhouse or laparoscopic ovum pick up (LOPU) oocytes. In experiment 1, one complex, one semi-defined, and one simplified IVM media were compared using slaughterhouse oocytes. In experiment 2, we checked the effect of oocyte origin (slaughterhouse or LOPU) on the kinetics of maturation (18 vs. 22 vs. 26 hours) when submitted to semi-defined or simplified media. In experiment 3, we determined the differences in embryo development between slaughterhouse and LOPU oocytes when submitted to both media and then to IVF or parthenogenetic activation (PA). Embryos from all groups were vitrified, and their viability evaluated in vitro after thawing. In experiment 1, no difference (P > 0.05) was detected among treatments for maturation rate (metaphase II [MII]; 88% on average), cleavage (72%), blastocyst from the initial number of cumulus oocyte complexes (46%) or from the cleaved ones (63%), hatching rate (69%), and the total number of blastomeres (187). In experiment 2, there was no difference of MII rate between slaughterhouse oocytes cultured for 18 or 22 hours, whereas the MII rate increased significantly (P < 0.05) between 18 and 22 hours for LOPU oocytes in the simplified medium. Moreover, slaughterhouse oocytes cultured in simplified medium matured significantly faster than LOPU oocytes at 18 and 22 hours (P < 0.05). In experiment 3, cleavage rate was significantly greater (P < 0.001) in all four groups of embryos produced by PA than IVF. Interestingly, PA reached similar rates for slaughterhouse oocytes cultured in both media, but improved (P < 0.05) the cleavage rate of LOPU oocytes. Slaughterhouse oocytes had acceptable cleavage rate after IVF (∼67%), whereas LOPU oocytes displayed a lower one (∼38%), in contrast to cleavage after PA. The percentage of blastocysts in relation to cleaved embryos was not affected by the origin of the oocytes (P > 0.05). Therefore, slaughterhouse oocytes developed a greater proportion of blastocysts than LOPU ones, expressed as the percentage of total cumulus oocyte complexes entering to IVM. Vitrified-thawed blastocysts presented similar survival and hatching rates between the oocyte origin, media, or method of activation. In conclusion, slaughterhouse and LOPU derived oocytes may have different IVM kinetics and require different IVM and IVF conditions. Although the IVM and IVF systems still need improvements to enhance embryo yield, the in vitro development step is able to generate good quality embryos from LOPU-derived oocytes.     

The reproductive performance of Thoroughbred mares treated with intravaginal progesterone at the start of the breeding season

The objective of this study was to investigate the effects of intravaginal progesterone on the reproductive performance of transitional Thoroughbred mares on commercial stud farms. Two hundred twenty-seven (227) non-lactating transitional Thoroughbred mares aged between 4 and 18 y (mean 9.4 ± 3.2 y) located on three stud farms in the Waikato region of New Zealand were used in the study performed during four consecutive breeding seasons (2007-10). Mares were age-matched in pairs and either treated with an intravaginal progesterone releasing device (Cue-Mare, 1.72 g progesterone, 10% w/w) for up to 10 d (Treated; n = 126) or left untreated (Control; n = 101). In both groups, 1,667 iu of hCG was given IV when an ovarian follicle ≥35 mm was detected (in conjunction with estrous behavior) and each mare was bred by natural service. Treated mares were served earlier in the breeding season (mean ± SD interval to first service was 13.9 ± 3.0 vs 26.7 ± 13.2 d for Treated and Control groups, respectively; P < 0.001). In the Treated and Control groups, 95.2 and 42.6% of mares were served within the first 21 d of the season (P < 0.001). Treated mares conceived earlier in the breeding season (mean number of days to conception 37.5 ± 14.2 vs 50.8 ± 21.3 d, P = 0.01). There was no difference between groups in the first service pregnancy rates (53.9 and 50.5% for Treated and Control mares, P = 0.89). Treatment with an intravaginal device increased the number of mares conceiving by the end of the breeding season (91.3 vs 82.3% for Treated and Control groups, P = 0.04). Therefore, this treatment protocol appeared to offer a convenient, economical and reliable method for managing transitional mares on commercial Thoroughbred stud farms.     

Uterine vascular degeneration is present throughout the uterine wall of multiparous mares. Colinearity between elastosis, endometrial grade, age and parity

Vascular degeneration is present in endometrial vessels of multiparous aged mares. The lesions associated with vascular degeneration consist of enlargement, duplication and splitting of the membrana elastica interna and perivascular deposits of elastin. However, there are no similar data available for deep myometrial vessels and the vascular layer. The objectives of the present study were to characterize the status of vasculature in full-thickness uterine necropsy samples and to correlate these findings to endometrial grade, age, and parity. Elastosis was present in myometrial vessels, as well as in large arteries and veins located between the circular and longitudinal myometrial layers. Vascular degeneration was associated with number of foals (P < 0.001) and endometrial grade (P < 0.05), but not with mare age (P > 0.05). Endometrial grade was associated with age (P < 0.001) and vascular grade (P < 0.05), but not with number of foals (P > 0.05). The presence of elastosis in the myometrial vessels was related to problems associated with chronic uterine infection (CUI) and delayed uterine clearance (DUC) of infertile mares. Uterine contractility was impaired in mares affected by CUI and/or DUC and could be related to a lack of myometrial blood flow. Additionally, degeneration of large vessels in the vascular layer may indicate a general compromise in uterine blood flow and fertility. The main conclusions were the presence of vascular elastosis in large deep myometrial vessels as well as in endometrial vessels, and that the factor with the strongest association with vascular degeneration was number of foals (P < 0.001), followed by endometrial grade (P < 0.05), but no association with mare age.     

Opioid regulation of luteinising hormone and prolactin release in the horse—identical or independent endocrine pathways?

In order to determine if endogenous opioids regulate luteinising hormone (LH) and prolactin secretion via a common, gonadotropin-releasing hormone (GnRH) dependent pathway in the horse, effects of the opioid antagonist naloxone (300 mg) and the GnRH agonist buserelin (20 μg) on prolactin and LH secretion were investigated in stallions (n = 22), long-term castrated geldings (n = 15) and non-lactating mares during the luteal phase of the oestrous cycle (n = 16). Blood samples for determination of LH and prolactin concentrations were withdrawn at 15 min intervals for 120 min. After 60 min of sampling, animals were treated with either naloxone, buserelin or saline. In stallions, naloxone significantly increased LH as well as prolactin release (P < 0.05), indicating an opioid inhibition of both hormones, whereas in mares, naloxone stimulated only LH secretion (P < 0.05). No changes in plasma LH or prolactin concentrations after injection of naloxone were found in geldings. In all animal groups, buserelin induced a significant release of LH (P < 0.05) without affecting prolactin. We conclude that endogenous opioids inhibit LH and prolactin release in the horse but the regulation of these two hormones involves independent opioid pathways. These are activated differentially in stallions, geldings and mares. The opioid regulation of prolactin secretion is not mediated via GnRH.     

Tannin-rich sainfoin pellet supplementation reduces fat volatile indoles content and delays digestive parasitism in lambs grazing alfalfa

Lambs grazing alfalfa or white clover are prone to flavour taint which can be an impediment to consumer acceptance. Here we investigated whether condensed tannin (CT)-rich sainfoin pellet supplementation of lambs grazing alfalfa influences meat sensory quality. Using three groups of 18 male Romane weaned lambs, we compared three feeding regimes: alfalfa grazing (AF), alfalfa grazing + daily supplementation with CT-rich sainfoin pellets (15 g dry matter (DM)/kg live weight, AS) and stall feeding with concentrate and grass hay indoors (SI). We also investigated the potential interest of sainfoin pellet supplementation for controlling digestive parasitism. The sainfoin pellets contained 42 g of CT/kg of DM and they represented on average 36% of the diet in AS lambs. Skatole and indole were detected in most of the AF and AS lambs, whereas in very few SI lambs. Skatole and indole concentrations in perirenal and dorsal fat were lower in the AS lambs than the AF lambs (P < 0.025 to P < 0.001), but the intensity of ‘animal’ odour and ‘animal’ flavour of the chops did not differ between both forage-grazing groups. Longissimus thoracis et lumborum muscle lightness was lower in the AF and AS lambs than the SI lambs (P < 0.001) with the other muscle colour coordinates being unaffected by the treatment and between-treatment group differences in muscle colour coordinates remaining constant throughout the 9-day display period. Subcutaneous fat colour coordinates were not influenced by the treatment. The number of individual anthelmintic drenches necessary to keep nematode faecal egg count below a threshold of 550 eggs/g of faeces was lower in the AS than the AF lambs (0.94 per lamb v. 1.63 per lamb; P < 0.001). Faecal oocyst count was lower in the AS than the AF lambs for the first measurement made 56 days after the beginning of the experiment (P < 0.001) and was not significantly different between both forage-grazing groups thereafter. The use of CT-rich sainfoin pellets to supplement lambs that are concurrently grazing alfalfa reduced fat volatile skatole and indole concentrations and delayed the onset of both helminth and coccidian infections.     

Effect of prior ingestion of glucose or fructose on the performance of exercise of intermediate duration

The metabolic responses induced by the ingestion of a beverage containing glucose (G), fructose (F) or placebo (W) 30 min before exercise of high intensity and intermediate duration have been investigated; in these conditions the energy processes are mostly dependent on aerobic reactions. A group of 11 male recreational sportsmen ran on a treadmill, at an intensity corresponding to 82% of peak oxygen consumption, until exhaustion on three different occasions (after ingestion of a beverage containing 75 g of G, 75 g of F or W). Plasma glucose, insulin, and lactic acid concentrations were determined just prior to the ingestion of the beverages, 30 min afterwards and 10 and 30 min after completion of the exercise. The mean endurance time was 644 (SD 261) s after the ingestion of G, 611 (SD 227) s after the ingestion of F and 584 (SD 189) s after the ingestion of the W (P < 0.05 between G and W). No differences in the oxygen uptake, respiratory quotient or lactate concentrations between the three trials were observed. Both plasma glucose and insulin concentrations determined in samples obtained immediately before the onset of exercise were higher when G was ingested than when F (P < 0.05 andP < 0.05, respectively) or W (P < 0.001 and P < 0.005, respectively) were ingested. These findings would suggest that the ingestion of G prior to an effort of intermediate duration may improve physical performance.     

Effect of increasing GnRH and PGF2α dose during Double-Ovsynch on ovulatory response,luteal regression,and fertility of lactating dairy cows

Ovsynch-type synchronization of ovulation protocols have suboptimal synchronization rates due to reduced ovulation to the first GnRH treatment and inadequate luteolysis to the prostaglandin F_2α (PGF_2α) treatment before timed artificial insemination (TAI). Our objective was to determine whether increasing the dose of the first GnRH or the PGF_2α treatment during the Breeding-Ovsynch portion of Double-Ovsynch could improve the rates of ovulation and luteolysis and therefore increase pregnancies per artificial insemination (P/AI). In experiment 1, cows were randomly assigned to a two-by-two factorial design to receive either a low (L) or high (H) doses of GnRH (Gonadorelin; 100 vs. 200 μg) and a PGF_2α analogue (cloprostenol; 500 vs. 750 μg) resulting in the following treatments: LL (n = 263), HL (n = 277), LH (n = 270), and HH (n = 274). Transrectal ultrasonography and serum progesterone (P4) were used to assess ovulation to GnRH1, GnRH2, and luteal regression after PGF_2α during Breeding-Ovsynch in a subgroup of cows (n = 651 at each evaluation). Pregnancy status was assessed 29, 39, and 74 days after TAI. In experiment 2, cows were randomly assigned to LL (n = 220) or HH (n = 226) treatment as described for experiment 1. For experiment 1, ovulation to GnRH1 was greater (P = 0.01) for cows receiving H versus L GnRH (66.6% [217/326] vs. 57.5% [187/325]) treatment, but only for cows with elevated P4 at GnRH1. Cows that ovulated to GnRH1 had increased (P < 0.001) fertility compared with cows that did not ovulate (52.2% vs. 38.5%); however, no effect of higher dose of GnRH on fertility was detected. The greater PGF_2α dose increased luteal regression primarily in multiparous cows (P = 0.03) and tended to increase fertility (P = 0.05) only at the pregnancy diagnosis 39 days after TAI. Overall, P/AI was 47.0% at 29 days and 39.7% at 74 days after TAI; P/AI did not differ (P = 0.10) among treatments at 74 days (LL, 34.6%; HL, 40.8%; LH, 42.2%; HH, 40.9%) and was greater (P < 0.001) for primiparous cows than for multiparous cows (46.1% vs. 33.8%). For experiment 2, P/AI did not differ (P = 0.21) between H versus L treatments (44.2% [100/226] vs. 40.5% [89/220]). Thus, despite an increase in ovulatory response to GnRH1 and luteal regression to PGF_2α, there were only marginal effects of increasing dose of GnRH or PGF_2α on fertility to TAI after Double-Ovsynch.     

Temporal relationships of a pulse of prolactin (PRL) to a pulse of a metabolite of PGF2α in mares

Hourly blood samples were collected from 10 mares during 24 h of each of the preluteolytic, luteolytic, and postluteolytic periods. The autocorrelation function of the R program was used to detect pulse rhythmicity, and the intra-assay CV was used to locate and characterize pulses of prolactin (PRL) and a metabolite of prostaglandin F2α (PGFM). Rhythmicity of PRL and PGFM concentrations was detected in 67% and 89% of mares, respectively. Combined for the three periods (no difference among periods), the PRL pulses were 5.2 ± 0.4 h (mean ± SEM) at the base, 7.5 ± 1.5 h between nadirs of adjacent pulses, and 12.3 ± 1.5 h from peak to peak. The peaks of PRL pulses were greater (P < 0.05) during the luteolytic period (46 ± 14 ng/mL) and postluteolytic period (52 ± 15 ng/mL) than during the preluteolytic period (17 ± 3 ng/mL). Concentrations of PRL during hours of a PGFM pulse were different (P < 0.003) within the luteolytic period and postluteolytic period and were greatest at the PGFM peak; PRL concentrations during a PGFM pulse were not different during the preluteolytic period. The frequency of the peak of PRL and PGFM pulses occurring at the same hour (synchrony) was greater for the luteolytic period (65%, P < 0.01) and postluteolytic period (50%, P < 0.001) than for the preluteolytic period (17%). This is the first report in mares on characterization and rhythmicity of PRL pulses, synchrony between PRL and PGFM pulses, and greater PRL activity during the luteolytic and postluteolytic periods than during the preluteolytic period.