Characterization of Doayo and Kapsiki taurine cattle breeds of Cameroon in their natural environment

Data were collected on live weight (LW), heart girth (HG), height-at-withers (HW), trunk length (TL), age, sex, and coat color of 207 taurines cattle—122 of the Doayo (Namchi) breed and 85 of the Kapsiki (Kirdi) breed. The animals, aged 1 to 20 years, were selected from 60 herds randomly selected from villages of Poli of Faro and Mokolo of Tsanga, divisions of the North and Far North Regions of Cameroon. The data were analyzed using the SAS program with a linear model, applying standard tests. Results indicated no breed effect (P > 0.05) in the growth trends of LW, HG, HW, and TL. HG and TL were highly significantly (P < 0.0001) related to LW. The growth pattern for the two breeds was the same since the linear contrast of least square means for the traits at various age groups did not differ (P > 0.05) significantly. The breeds attained maturity as from 4 years. In the absence of breed effect (P > 0.05), a single regression equation was established for the estimation of live weight as thus LW = - 244.42 ( ±22.57 ) kg + 2.49 ( ±0.23 ) HG + 1.04 ( ±0.25 ) TL {\hbox{LW}} = - {244}.{42 }\left( {\pm {22}.{57}} \right){\hbox{ kg}} + {2}.{49 }\left( {\pm 0.{23}} \right){\hbox{ HG}} + {1}.0{4 }\left( {\pm 0.{25}} \right){\hbox{ TL}} , with HG contributing up to 70% of total variation and TL, 2%. This equation could be used to develop a measuring band useful in the rural environment for commercial and clinical veterinary purposes.     

Plasma serotonin levels in Italian Fresian dairy cows

The aim of this work was to investigate the metabolism of plasma serotonin or 5-hydroxytryptamine (5-HT), an important neurotransmitter, in Fresian dairy cows, a breed of zootechnical interest, using high-performance liquid chromatography with electrochemical detection. The subjects under study were at the stage of early lactation (n = 10; \( {\hbox{mean body weight}} \ 375\pm 50 \ {\hbox{kg}} \); average age of 3 years; body condition score 2.5), bred in a farm at an altitude of 150 m a.s.l. To evaluate animal welfare on this farm, which is closely connected to an animal’s physiological status, tryptophan and cortisol levels (measured by enzyme-linked immunosorbent assay), together with levels of certain blood components [total proteins (TP), albumin, creatinine, glucose (Glu), triglycerides, phospholipids, total cholesterol, and aspartate transaminase, measured by spectrophotometry] were analyzed. The results obtained are discussed in comparison with reference values, taking into account the environmental living conditions. Measured plasma serotonin concentrations, which were lower than values reported for Brown Swiss dairy cows of a comparable age and diet, appeared to be affected by breed, temperature, blood sampling season, and altitude. Additional differences between the levels of plasma tryptophan, the amino acid precursor of serotonin, of the two breeds were comparable. Negative correlations between plasma tryptophan and plasma cortisol levels (r = −0.83, P < 0.005), plasma serotonin and plasma TP levels (r = −0.72, P < 0.05), or Glu levels (r = −0.77, P < 0.05) highlight the existence of a stress condition, which is connected to an energetic deficit related to lactation.

     

Efficiency of two timed artificial insemination protocols in Murrah buffaloes managed under a semi-intensive system in the tropics

The objective of the study was to determine the efficiency of ovsynch (OV) versus presynch-ovsynch (P-OV) protocol for synchronization of ovulation and timed artificial insemination (TAI) in female buffaloes. The OV group (n = 40) received gonadotrophin-releasing hormone (GnRH) on day 0 (random day of the estrous cycle), prostaglandin ( PGF_2a ) \left( {{\hbox{PG}}{{\hbox{F}}_{2\alpha }}} \right) on day 7 and a second GnRH administration on day 9 followed by a single artificial insemination (AI) 16-20 h later. The P-OV group (n = 40) received two PGF_2a {\hbox{PG}}{{\hbox{F}}_{2\alpha }} injections 14 days apart, with the second injection administered 14 days before starting the OV protocol. Progesterone (P₄) was measured at the time of PGF_2a {\hbox{PG}}{{\hbox{F}}_{2\alpha }} administration (within the OV protocol) and AI. Neither ovulation rate ((24 h after TAI) OV 90%-36/40 vs. P-OV 85%-34/40) nor pregnancy rates ((day 60 after TAI) OV 35%-14/40 vs. P-OV 45%-18/40) differed between the two protocols. Pregnant buffaloes had lower concentrations of P₄ at AI compared with non-pregnant animals in the OV group (0.7 ± 0.1 vs. 1.1 ± 0.1 ng/ml); but in the P-OV group, differences did not reach statistical significance (0.8 ± 0.1 vs. 1.0 ± 0.1 ng/ml). This apparent trend reached statistical significance when the analysis was carried out in animals from both protocols (0.7 ± 0.1 (pregnant) vs. 1.1 ± 0.1 (non-pregnant) ng/ml). In conclusion, both protocols synchronize ovulation effectively with no significant differences in conception rates. High concentrations of P₄ at AI seem to be detrimental for the establishment of pregnancy in lactating buffalo cows.     

High versus low body condition in mares: interactions with responses to somatotropin,GnRH analog,and dexamethasone

Mares that had previously been fed to attain body condition scores (BCS) of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) were used to determine the interaction of BCS with the responses to 1) administration of equine somatotropin (eST) daily for 14 d beginning January 20 followed by administration of GnRH analog (GnRHa) daily for 21 d and 2) 4-d treatment with dexamethasone later in the spring when mares in low BCS had begun to ovulate. The majority of mares with high BCS continued to cycle throughout the winter, as evidenced by larger ovaries (P < 0.002), more corpora lutea (P < 0.05), greater progesterone concentrations during eST treatment (P < 0.04), and more (P < 0.05) large- and medium-sized follicles. Treatment with eST alone or in combination with GnRHa had no effect (P > 0.05) on ovarian activity or ovulation. Plasma leptin concentrations were greater (P < 0.002) in mares with high BCS; however, there was no effect (P > 0.10) of eST treatment. Plasma IGF-I concentrations were greater (P < 0.0001) in mares treated with eST compared with mares given vehicle, and mares with high BCS had greater IGF-I (P < 0.02) and LH concentrations (P < 0.02) than mares with low BCS. Plasma leptin concentrations in mares with high BCS were increased (P < 0.001) within 12 h of dexamethasone treatment; the leptin response (P < 0.001) in mares with low BCS was greatly reduced (P < 0.001) and transient. Glucose and insulin concentrations also increased (P < 0.0001) after dexamethasone treatment in both groups, and the magnitude of the response was greater (P < 0.0001) in mares with high BCS than in mares with low BCS. In summary,low BCS in mares was associated with a consistent seasonal anovulatory state that was affected little by eST and GnRHa administration. In contrast, all but one mare with high BCS continued to experience estrous cycles and(or) have abundant follicular activity on their ovaries. The IGF-I response to eST treatment was also reduced in mares with low BCS, as was the basal leptin concentration and leptin response to dexamethasone. Although low BCS and leptin concentrations were associated with inactive ovaries during winter and early spring, mares with low BCS eventually ovulated in April and May while leptin concentrations remained low.     

Progesterone supplementation during multiple ovulation treatment in buffalo species (<Emphasis Type="Italic">Bubalus bubalis</Emphasis>)

The aim of this study was to evaluate the effect of exogenous progesterone supplementation on superovulatory response in buffaloes that has undergone a multiple ovulation program. Fourteen Mediterranean buffaloes were divided into two groups and received a 4-day decreasing dosage of an equal mixture of 500 IU of FSH and LH starting on day 8 of the cycle. In group A (n = 7) a progesterone-releasing intravaginal device was removed on day 8, whereas in group B (n = 7) it was left till day 10, when PGF_2a {\hbox{PG}}{{\hbox{F}}_{{2}\alpha }} was administered. Eighty hours later, buffaloes were artificially inseminated and after 6 days they undergone uterine flushing. A higher (P < 0.05) number of corpora lutea (8.3 vs. 5.7) and embryo/flushing/buffalo (2.3 vs. 1.3) were recorded in group B vs. group A if responsive buffaloes are considered (n = 12) and the number of corpora lutea was highly correlated with the number of embryos (r = 0.65; P < 0.05). In conclusion, progesterone supplementation during the first 2 days of the superovulation treatment seems to enhance the recovery rate in buffalo species. A high ovulation rate, associated with a high number of corpora lutea, can represent a parameter for estimating embryo recovery.     

Effect of breed and other animal-related factors on conception rate to artificial insemination with frozen semen in mares in Ethiopia

Equine reproduction is unique by having long behavioral estrus and differences in time of breeding between breeds and individuals of mares. An experimental study was conducted at the Balderas Sport Horses and Recreational Center, Addis Ababa, Ethiopia, from January to June, 2018, to evaluate conception rate to frozen semen in local and exotic crossbreed mares. Mares were teased to characterize estrus behavior and examined by ultrasound in determining imminent ovulation. Inseminations were done post ovulation within an average of 6–9 h using frozen-thawed semen. The overall conception rate to frozen semen was 15/21 (71.43%) with 8/11 (72.73%) in crossbreed and 7/10 (70%) in local breed mares. Age and body condition score (BCS) of animals had no significant effect on conception rate to AI with frozen semen. A slightly higher conception rate was obtained when ovulation was from the right ovary than when ovulated from the left ovary. A higher conception rate was obtained when the diameter of the preovulatory follicle was ≤ 45 mm than above diameter. The conception rate increased significantly with increased number of services/conception with an overall mean ± (SEM) of 2.2 ± 0.2 services/conception. A more number of services/conception were required for local breed (2.7 ± 0.2) than crossbreed mares (1.8 ± 0.3) and again for lower body condition scores than higher condition scores of mares. In conclusion, the increased number of services improved the conception rate with significant difference between breed of mares, whereas good management of mares for improved body conditions could be required to decrease the number of services per conception.

     

Endocrine Profile Comparisons of Fat Versus Moderately Conditioned Mares Following Parturition

The influence of progesterone, luteinizing hormone (LH), and estrogen on the mare's estrous cycle has been well researched and documented, but other endocrine profiles have not received as much attention. To evaluate endocrine concentrations in fat-conditioned (body condition score [BCS] of 7–8) versus moderately conditioned mares (BCS of 5–6), 24 mares were allotted to and maintained in respective groups from late gestation until pregnancy was confirmed after breeding on the second postpartum estrus. Serum concentrations of thyroxine (T₄), insulin-like growth factor-1 (IGF-1), and leptin were assayed to characterize circulating blood concentrations. Additionally, LH and progesterone serum concentrations were assayed to evaluate the estrous cycle status of the mares. Leptin and progesterone concentrations were not different (P > .05) between the groups. Nevertheless, serum concentrations of T₄ were higher (P < .01) and IGF-1 concentrations lower (P < .01) in moderately conditioned as compared with fat-conditioned mares during times of ovulation and the interovulatory period. Furthermore, serum concentrations of LH were found to be different between the groups only when the estrous cycle approached the second ovulation (P < .0001). Results of this study suggest that mares maintained in a BCS of 5 or greater are similar in terms of reproductive efficiency. Although the circulating serum concentrations of T₄ and IGF-1 are different after parturition, their influence does not affect reproductive capabilities of mares with a BCS of 5 or greater.     

Phosphorus,calcium, and magnesium contents of pasture and their effect on body condition scores and body mass of communal cattle depending on natural pasture of Mogosane Village,of the North-West Province,South Africa

This research was conducted to determine the effects of phosphorus (P), calcium (Ca), and magnesium (Mg) content in pasture with body weight and body condition scores in cattle depending entirely on natural grazing. The work was done in 2006 in Mogosane Village of North-West Province, South Africa, and it was conducted from March 2006 to March 2007, with the annual rainfall of 384.38 mm maximum. A total of 25 growing mixed breed cattle aged between 6 months and 2 years old were selected randomly from a herd feeding exclusively on communal grazing. Animals were depending on natural pasture, with no supplements given. Records of body mass (BM) and body condition score (BCS) were recorded from a diverse range of animals in order to include as many different body masses and body condition scores as possible. Mean BM and BCS values are reported but there were no significant (P > 0.05) differences between months. Possible reasons are given in the “Results and Discussion” section. The focus of the research reported here was on the changes in the P, Ca, and Mg concentrations of pasture. Pasture samples were collected once a month for analysis to determine the contents of P, Ca, and Mg. Mineral concentrations in the pasture increased significantly (P < 0.05) with rainfall in January 2007, February 2007, and March 2007, and in January 2007 and February 2007, the mean values of BCS (3.90) and BM (444.05 kg) increased. After the good rains in March 2006 and April 2006, there were significant (P < 0.05) decreases in grass P and Mg in the following dry months along with decreases in BCS and BM. There were subsequent significant (P < 0.05) increases in grass P and Mg following rains in August 2006 through January 2007. Grass Ca followed a much different pattern compared with that of P and Mg with significant (P < 0.05) increases after periods of little or no rainfall. Mineral concentrations (P, Ca, and Mg) of grass in this research were significantly (P < 0.05) influenced by the rainfall making it imperative that mineral supplementation be given to animals in the dry periods.

     

The relationship between body condition,leptin, and reproductive and hormonal characteristics of mares during the seasonal anovulatory period

An experiment was conducted to determine the effects of high vs low body condition scores (BCS) produced by restricted feeding on reproductive characteristics, hormonal secretion, and leptin concentrations in mares during the autumnal transition and winter anovulatory period. Mares with BCS of 6.5 to 8.0 were maintained on pasture and/or grass hay, and starting in September, were full fed or restricted to produce BCS of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) by December. All but one mare with high BCS continued to ovulate or have follicular activity during the winter, whereas mares with low BCS went reproductively quiescent. Plasma leptin concentrations varied widely before the onset of restriction, even though all mares were in good body condition. During the experiment, leptin concentrations gradually decreased (P < 0.0001) over time in both groups, but were higher (P < 0.009) in mares with high vs low BCS after 6 wk of restriction, regardless of initial concentration. No differences (P > 0.1) between groups were detected for plasma concentrations of LH, FSH, TSH, GH, glucose, or insulin in samples collected weekly; in contrast, plasma prolactin concentrations were higher (P < 0.02) in mares with high BCS, but also decreased over time (P < 0.008). Plasma IGF-I concentrations tended (P = 0.1) to be greater in mares with high vs low BCS. The prolactin response to sulpiride injection on January 7 did not differ (P > 0.1) between groups. During 12 h of frequent blood sampling on January 12, LH concentrations were higher (P < 0.0001), whereas GH concentrations (P < 0.0001) and response to secretagogue (EP51389; P < 0.03) were lower in mares with high BCS. On January 19, the LH response to GnRH was higher (P < 0.02) in mares with high BCS; the prolactin response to TRH also was higher (P < 0.01) in mares with high BCS. In conclusion, nutrient restriction resulting in low BCS in mares resulted in a profound seasonal anovulatory period that was accompanied by lower leptin, IGF-I, and prolactin concentrations. All but one mare with high BCS continued to cycle throughout the winter or had significant follicular activity on the ovaries. Although leptin concentrations on average are very low in mares with low BCS and higher in well-fed mares, there is a wide variation in concentrations among well-fed mares, indicating that some other factor(s) may determine leptin concentrations under conditions of high BCS.     

Effect of environmental factors and changes in the body condition score on the onset of the breeding season in mares

Several methods have been proposed to advance the onset of the breeding season in horses. Most of them are based on the exposure to an artificial lighting period combined with hormonal treatments. Mares exposed to an artificial photoperiod are most often housed indoors where the ambient temperature is often higher than the outside temperature. Mares held in barns are also exposed to different daylight intensities than horses kept outside, depending on the architecture. In the current study, we evaluated the impact of ambient temperature, daylight intensity and changes in body condition score (BCS) on the timing of first ovulation after winter anestrus in mares exposed to an artificial photoperiod. Mares (n = 211) were housed in barns with different ambient temperature and daylight exposure but with the same artificial photoperiod exposure (except for a natural photoperiod control group). Artificial photoperiod as well as an increase in BCS over the winter significantly advanced the first spring ovulation. The BCS at the start and end of the anestrus period did not have an effect on the interval to first ovulation and neither did the modest increase in ambient temperature in the barn. However, a higher light intensity during the daytime significantly advanced the first spring ovulation. The results of this study suggest that exposure to more sunlight advances the onset of the breeding season. This effect is likely mediated through the biological effect of short wavelength blue light and its impact on melatonin suppression and biological rhythms. We suggest that greater/direct exposure to the blue light component of daylight improves the response to the artificial photoperiod. The results of the present study can further assist to optimize the conditions that lead to an efficient spring transition of breeding mares.     

Effects of season and body condition on appetite, body mass and body composition in ad libitum fed pony mares

Changes in appetite, body mass (BM), body condition score (BCS), direct (ultrasonographic) and indirect (deuterium oxide dilution technique) measures of body fat were monitored in Welsh Mountain pony mares (n = 11, 5–19 years of age) offered ad libitum access to a complete diet (gross energy 16.9 ± 0.07 MJ/kg dry matter) for 12 weeks during summer (n = 6; 246 ± 20 kg) and winter (n = 5; 219 ± 21 kg). At the outset, each group comprised two thin (BCS 1–3/9), moderate (BCS 4–6/9) and obese (BCS 7–9/9) animals.For ponies that were non-obese at the outset, BM was gained more rapidly (P = 0.001) in summer (0.8 ± 0.1 kg/day) than winter (0.6 ± 0.0 kg/day). This was associated with a seasonal increase in dry matter intake (DMI) which became maximal (summer, 4.6 ± 0.3% BM as DMI/day; winter, 3.5 ± 0.1% BM as DMI/day) during the second month. The appetite of the obese ponies was half that reported for non-obese animals in the summer and BM remained constant irrespective of season.Body ‘fatness’ increased progressively for non-obese but not obese ponies. Body fat content was exponentially associated with increasing BCS but BCSs >6 were not useful indicators of actual body fat. Endogenous circannual mechanisms to suppress winter weight gain were insufficient to prevent the development of obesity in ad libitum fed ponies.     

Estradiol interactions with dopamine antagonists in mares: Prolactin secretion and reproductive traits

Two experiments studied the effects of pretreatment with estradiol benzoate before treatment with a dopamine antagonist on prolactin secretion and reproductive traits in mares during (1) the seasonal anovulatory period and (2) the normal breeding season. Experiment 1 was performed in winter with 17 mares selected for low follicular activity. Nine mares received estradiol benzoate injections every other day for a total of 10 injections; 8 mares received similar injections of vehicle. Ten days after onset of injections, all mares were placed on daily injections of sulpiride (250 mg) for 35 days or until ovulation. Plasma prolactin concentrations were higher (P < .001) in mares receiving estradiol than in controls for all assessments from days 12 through 36. Plasma luteinizing hormone (LH) concentrations were also increased (P < .05) by estradiol treatment from days 14 to 23. Mean day of first ovulation was 73.6 for control mares and 29.0 for estradiol-treated mares (P = .016). Estradiol treatment greatly enhanced prolactin secretion in response to sulpiride and increased LH secretion in seasonally anovulatory mares, which together hastened the date of first ovulation by an average of 45 days. Experiment 2 was designed to assess the efficacy of a long-acting, single-injection microparticle preparation of another dopamine antagonist, domperidone, for increasing prolactin secretion in cyclic mares in the summer. The experimental design and procedures used in experiment 1 were repeated, except that a single 3-g domperidone-microparticle injection was administered on day 11 rather than 45 days of sulpiride injections. Day 0 was the first day of estrus for each mare. Prolactin concentrations were higher (P < .05) in mares receiving estradiol than in control mares from days 12 through 25 and after a thyrotropin-releasing hormone injection on d 21. Estrous cycle traits (time to ovulation and time of luteal regression) were not affected (P > .1) by treatment. Estradiol enhanced the prolactin response to a single injection of 3 g domperidone in cyclic mares in the summer in a manner similar to the estradiol enhancement of prolactin secretion in response to daily sulpiride injections in anovulatory mares in winter. Thus, the single injection of domperidone could possibly replace the daily sulpiride injections used in experiment 1 to induce ovulation in seasonally anovulatory mares; this needs to be tested in future experiments.     

Connection between body condition score, chemical characteristics of body and reproductive traits of rabbit does

Body condition scoring (BCS) is widely used to evaluate the nutritional status of livestock (cows, ewes, sows). In intensive systems, rabbit does are generally inseminated 11 days post partum and, due to a hormonal antagonism and an energy deficit caused by concurrent lactation and pregnancy, they show low fertility. The aim of this investigation was to assess an in vivo method for scoring the body condition of does by verifying the association with the body fat depots, the chemical composition of body tissues, the ovarian status, the hormonal response and the reproductive performance. The evaluation of BCS, involving 66 multiparous lactating does inseminated at 11 days post partum, was based on the test of bone protrusions and fullness of muscle of the loin, rump and hind leg. The traits were subjectively scored using 0, 1 and 2 for poor, intermediate and good condition, respectively. For calculating an aggregate BCS, the hind leg score was omitted, because it is less correlated with the real body condition. Adding the respective score (0–2) of the loin and rump regions, 5 classes of BCS were obtained (0–4). This aggregate BCS was highly correlated with the body fat depots (r = 0.79), the ether extract content of muscle samples of Obliquus abdominis (r = 0.87) and Biceps femoris (r = 0.84), and the ether extract of the empty body (r = 0.84). There was a lower correlation with the body weight (r = 0.45). The increase of BCS corresponded to higher lipid content in the body parts considered, especially the Obliquus abdominis (from 2.0 to 10.0%) and fat depots (from 10.6 to 107.7 g/doe). BCS was not related to ovulation rate or embryo production, but was correlated with sexual receptivity and fertility.Plasma FSH and LH concentrations were determined by RIA, 48, 24, 0 h before and 1 h after GnRH administration and artificial insemination. Animals with extreme body condition scores (BCS ≤ 1 or BCS = 4) showed lower plasma FSH levels (20.0 vs. 34.5 ng/mL) than does with optimal body condition (2 ≤ BCS ≤ 3) and their preovulatory LH surge, released after GnRH administration, was less evident (16.9 vs. 20.3 ng/mL). The poor reproductive performance of does with extreme BCS could be explained by this pituitary activity. On day 11 post-partum, a high number of does (71.2%) had extreme BCS and showed a lower sexual receptivity (37.2% vs. 80.0%) and fertility rate (50.9% vs. 86.6%) than does in optimal condition. On these results, the possibility of applying an in vivo method for scoring the body condition of lactating rabbit does appears promising for use in on-farm reproductive management.     

Pregnancy Rates in Tranquilized Maiden Thoroughbred Mares

In Thoroughbred breeding, it is sometimes necessary to tranquilize a maiden mare to accomplish safe breeding by natural service. To determine whether tranquilization adversely affected fertility of maiden mares, pregnancy rates achieved in 792 matings of 531 maiden Thoroughbred mares were evaluated. One hundred sixty-three matings were accomplished after administration of a tranquilizer cocktail (20 mg acepromazine, 100 mg xylazine, and 10 mg butorphanol tartrate, injected intravenously), whereas 598 matings were accomplished without tranquilization. Pregnancy rate/cycle did not differ between maiden mares tranquilized before (64%; 105/163) and mares not tranquilized before mating (69%; 434/629) (χ² = 1.048; P > .05). We concluded that tranquilization of maiden Thoroughbred mares immediately before mating did not adversely affect fertility.     

Oxidative Stress and Antioxidant Status in Standardbreds: Effect of Age and Training in Resting Plasma and Muscle

The hypothesis of this study was that yearlings would have more oxidative stress as measured by malondialdehyde (MDA), total glutathione (GSH-T), glutathione peroxidase (GPx), and nitric oxide (NO) than mature mares before training, but after they would have similar levels. Ten Standardbred yearling fillies and 10 mature Standardbred mares were split into trained and nontrained groups. Horses were trained 5 days/wk for 7 weeks. Blood and muscle samples were collected at rest on weeks 0, 2, 5, 7, and 9. At week 0, the yearlings had higher muscle GSH-T and NO concentrations (P = .03) than the trained mares. At week 9, plasma NO concentrations were lower in trained mares than in the trained yearlings (P = .007). Trained mares increased muscle MDA and decreased plasma MDA concentrations from weeks 0 to 9 (P < .01), while all mares increased muscle NO and GSH-T concentrations by week 9 (P < .05). Trained mares and yearlings had increased erythrocyte GPx activity at weeks 7 and 9 and GSH-T concentration at week 7 (P < .05). Mares had higher lipid peroxidation and lower antioxidant status in the muscle than the yearlings prior to training. Trained mares improved antioxidant status and oxidative stress levels through training, resulting in levels similar to the yearlings.     

Infertility in the brood mare

This communication describes the methods used and results obtained with a 21-year-old Standardbred sire bred, using artificial insemination techniques, to a book of 108 mares during the period 11th September to 16th March, 1979-80. A positive pregnancy test rate of 93.5% was achieved. Those mares becoming pregnant averaged 4.6 inseminations per pregnancy (range 1-13). Barren mares, maiden mares and wet mares, irrespective of age, all achieved highly satisfactory pregnancy rates and it was noted that breeding through the January/February period improved the ultimate success rate markedly. When the official returns for the breeding season under review were returned the sire had a live foal success rate of 84%.     

Comparison of Efficacy of Two Dose Rates of Histrelin for Inducing Ovulation in Broodmares

Between February 14 and April 26, 2012, 75 broodmares (7 maiden, 11 barren, and 57 foaling) maintained on pasture in southeast Texas were examined three times weekly (Tuesday, Thursday, Saturday) by transrectal palpation and ultrasonography. On Tuesday or Thursday, mares in estrus with uterine edema, a relaxed cervix, and a dominant follicle ≥30-mm diameter were alternately assigned to treatment with 0.5 mg of intramuscular (IM) histrelin (group 1) or 0.25 mg IM histrelin (group 2). Ovulation was confirmed by ultrasound examination. No differences in proportion of maiden plus barren (96%) compared to foaling (86%) mares ovulating within 2 days was found (P > .10); therefore, responses for all mares were combined for analysis. No differences in ovulation rates within 2 days were noted for 0.5 mg histrelin compared to those for 0.25 mg histrelin treatment (42 of 46, 91%; 44 of 52, 85%; P > .10). No differences were detected between response rates to 0.5 or to 0.25 mg histrelin for any month (P > .10). The use of 0.5 or 0.25 mg histrelin were found to be effective treatments for inducing ovulation within 2 days of administration throughout the early breeding season.     

Retrospective study on the incidence of postinsemination uterine fluid in mares inseminated with frozen/thawed semen

Uterine fluid accumulation has been reported after insemination or natural breeding of mares. This retrospective study examined the factors affecting the incidence of uterine fluid after insemination of frozen semen. Specifically, this study determined the association between mare age, reproductive status, fluid accumulation, and pregnancy rates in mares. Records were available from 283 warmblood mares throughout 496 cycles. Mares were divided into maiden, foaling, and barren and age groups of 3 to 9, 10 to 16, and more than 16 years. Mares were inseminated only once with frozen semen within 4 to 8 hours before or after ovulation. Ultrasound examinations were performed 12 to 18 hours after insemination. A depth of at least 20 mm of fluid was considered significant. Mares with less than 20 mm were treated with oxytocin, and those with more than 20mm of fluid were given oxytocin and uterine lavage. Pregnancy determination was performed at 14 to 16 and 30 to 50 days after ovulation. Fluid level of more than 20 mm was recorded in 25% of the cycles. Barren mares and aged mares (10-16 and > 16 years) had a higher incidence of uterine fluid accumulations. Per-cycle pregnancy rate was lower (45%) in mares with uterine fluid than in mares without uterine fluid (51%). This difference was primarily due to the reduction in fertility of mares who were older than 16 years and retained fluid after insemination. Apparently, oxytocin and lavage treatments provided acceptable fertility in the other groups of mares that had uterine fluid.

Introduction

Use of equine frozen semen is accepted by the majority of horse registries. According to several field studies,[1, 2, 3, 4 and 5] insemination of frozen semen has resulted in acceptable pregnancy rates. Postbreeding fluid accumulation is a physiologic inflammation that clears the uterus of foreign material such as excess spermatozoa, seminal plasma, bacteria, and extenders. [6, 7, 8, 9 and 10] Uterine fluid can be easily diagnosed with ultrasonography. [10, 11 and 12] Persistent postbreeding uterine fluid has been associated with a decrease in fertility after natural mating or artificial insemination (AI) of fresh semen. [11, 12 and 13] Predisposing factors to persistent fluid accumulations are reduced myometrial contractions, poor lymphatic drainage, large overstretched uterus, and cervical incompetence. [7, 14 and 15] Normal mares are able to expel uterine fluid quickly after inseminations, whereas susceptible mares accumulate fluid in their uterine lumen for more than 12 hours after breeding or insemination. [10]It is commonly stated that insemination with frozen semen leads to greater post-AI fluid accumulation than insemination with fresh or cooled semen or after natural mating. Apparently, there is only 1 controlled study on this comparison.[7] The authors reported that infusion of frozen semen resulted in a greater inflammatory response than natural breeding. In a field study, [16] 16% of mares naturally mated had persistent postbreeding fluid accumulations compared with a 30% rate reported for mares inseminated with frozen semen. [1 and 2] More recently, Watson et al. [17] reported a postbreeding fluid accumulation rate of 16%, which is identical to that reported for natural mating. [16] It is difficult to compare studies because details of mare selection and insemination or breeding frequencies are not always reported. Obviously, a higher proportion of barren and aged mares in a study would increase the incidence of postbreeding fluid accumulation. [1 and 2]The study presented herein was a retrospective study designed to determine the incidence of postbreeding fluid accumulation in a large number of mares inseminated with frozen semen. Associations were determined between mare age, reproductive status and fluid accumulation, and pregnancy rate in mares with and without uterine fluid accumulation.

Materials and methods

Mares

Records were available from 283 warmblood mares inseminated with frozen semen at the Cristella Veterinary Clinic in Italy during 1998 to 2001. Mares ranging in age from 3 to 20 years were inseminated with semen that was frozen in 10 centers and was from 34 stallions. The broodmare population was subdivided into 3 reproductive groups: 89 maiden mares (mean age, 7.2 years), 106 foaling mares (mean age, 9.4 years), and 87 barren mares (mean age, 11.9 years). Maiden mares older than 7 years were selected with biopsy scores of 1 or 2 only. Barren mares were open for no more than 2 consecutive seasons and had negative cytology and bacteriology scores. Age groups were divided as follows: 3 to 9 years (n = 132), 10 to 16 years (n = 137) and older than 16 years (n = 14). Data from 496 cycles were used. Distribution of the estrous cycles was 172, 157, and 167 in the maiden, foaling, and barren groups, respectively; and 224, 244, and 28 in the youngest, intermediate, and oldest groups, respectively.

Mare reproductive management and artificial insemination protocol

During estrus, all mares underwent a daily ultrasound examination with a 5-mHz transrectal probe (SA 600 Vet; Medison Inc., Seoul, South Korea) until 1 or more 35-mm ovarian follicles were detected. Ovulation was then induced by the intravenous administration of 2000 IU of human chorionic gonadotropin (hCG). Ultrasound examination was performed 12 hours after hCG treatment and then every 4 to 8 hours until ovulation occurred. Mares were inseminated only once within a period of 4 to 8 hours before or after ovulation. The semen used was thawed according to the distribution center's instructions and had the following minimum post-thaw quality requirements: not less than 200 × 10⁶ progressively motile spermatozoa per dose and a minimum of 30% progressive spermatozoal motility. Foaling mares were not inseminated at their first postpartum (“foal heat”) estrous period, because pregnancy rates are recognized to be lower than during the subsequent estrous periods.[18] During the first postpartum estrus, ovarian ultrasound scan examinations were performed every 2 to 3 days until an ovulation was detected. A prostaglandin F₂α injection was given 5 days later to short-cycle the mare.

Postinsemination monitoring

An ultrasound examination of the reproductive tract was performed 12 to 18 hours after insemination to detect any intrauterine fluid accumulation. The presence and depth of intrauterine fluid was recorded. Twenty millimeters or more of grade II or III intrauterine fluid[19] was recorded as a significant amount of fluid. Mares with less than 20 mm of fluid were treated with an intravenous injection of 20 IU oxytocin. For mares with more than 20 mm of fluid, oxytocin was administered, and the uterus was flushed daily with buffered saline solution: 1-L aliquots were infused and recovered until the recovered fluid was clear. In these mares, oxytocin treatment was repeated up to 3 times daily. Post insemination treatments were performed for no more than 4 days after ovulation had occurred.Pregnancy diagnosis was performed with ultrasound at 14 to 16 days after ovulation. Scans were then repeated at 30 and 50 days of gestation to confirm the presence in the uterus of an apparently healthy developing conceptus.

Statistical analysis

χ² Analysis was used to determine the effect of reproductive status and age on the incidence of fluid accumulation. In addition, the influence of persistent uterine fluid accumulation on pregnancy rates per cycle was determined for each reproductive class and age by using χ² analysis.

Results

The per-cycle pregnancy rate at 14-16 days after ovulation was 49.3% (245/496 cycles). By the end of the season, 245 of 283 mares (86.5%) were confirmed pregnant. Fluid level of at least 20 mm (grade II or III) was recorded in 126 of the 496 cycles (25.4%). Barren mares had a higher (P < .05) incidence of postbreeding fluid accumulation (64/167; 38.3%) than maiden (34/172; 19.7%) and foaling (28/157, 17.8%; Table 1) mares. The incidence of fluid accumulation was also higher in mares older than 16 years (19/28; 67.8%) than those aged 10 to 16 years (69/244; 28.2%) and 3 to 9 years (38/224; 17%). The incidence of uterine fluid was also higher (P < .05) for mares aged 10 to 16 years than those aged 3 to 9 years (Table 2). Overall, the per-cycle pregnancy rate was lower (P < .05) for mares with post-AI fluid accumulations than for those with no uterine fluid or only a small quantity of fluid (57/126, 41.9% vs 188/360, 56.2%). Pregnancy rates were similar (P > .05) for mares with or without uterine fluid when comparisons were made within maiden and barren mare groups. However, more foaling mares became pregnant when no fluid was detected after insemination. Pregnancy rate for this group (68.1%) was higher than that for maiden (44.2%) and barren (44.6%) mares (Table 3). Older mares with uterine fluid accumulations had a lower per-cycle pregnancy rate (36.8%) than mares in the same group but without fluid. Surprisingly, if no fluid was detected, the highest pregnancy rates were in mares older than 16 years ( Table 4).     

Relationship between body condition score and production of multiparous beef cows

Pregnancy rate, calving interval, weaning weight, birth weight and quarterly body condition score (BCS) were collected on fall calving multiparous English crossbred cattle (ages 3 to 10) from 1994 to 2001 to evaluate the critical time of cow condition measurements that predict production. The study was initiated with 260 cows. Replacement animals entered the study at first calving (2 years of age), with 45, 54, 27, 68, 54, and 45 animals added in years two through seven, respectively. Body condition score was measured in association with calving, breeding, weaning, and midway between weaning and calving (August). Regression of the logit of the probability of pregnancy (Y) showed that pregnancy outcome was quadratically related to BCS at breeding (P < 0.0001, Y = − 4.81X² − 0.52X − 4.339) and linearly related to BCS at calving (P = 0.009, Y = 0.32X + 4.17), but was not associated with either the pre- or postpartum change in condition (P > 0.05). Calving interval varied cubically with BCS at calving and quadratically with BCS at breeding (P < 0.0001 and P = 0.002, respectively). The largest decreases in calving interval were associated with increases in body condition score at calving from 3.5 to 4.5 and from 7 to 8. Calf weight at 205 days was related to both the BCS at breeding and the change in BCS from breeding to weaning (P = 0.01 and P = 0.004). Calf weight at 205 days was also associated with BCS at weaning (P = 0.0003). Cows with either low or high BCS at weaning tended to wean lighter calves than cows with moderate condition (4.5 and 5.5). Moreover, BCS at weaning (≈ 6 months prior to calving) was related to birth weight (P = 0.01). Dams with a BCS at weaning of 7 birthed heavier calves than dams with low (3 to 4) or high (8.5) BCS. The relationship of BCS at breeding with pregnancy rate, calving interval, and weaning weight suggests that maintenance of adequate BCS immediately before, during, and after the breeding season may be most critical to sustaining adequate reproductive performance and calf gains in animals subject to the seasonal forage production associated with a Mediterranean climate.     

Effects of a gonadotropin-releasing hormone antagonist and altrenogest on luteinizing hormone concentration and ovulation in the mare

The objective of Experiment 1 was to determine a dose and frequency of gonadotropin-releasing hormone (GnRH) antagonist administration to effectively suppress serum luteinizing hormone (LH) concentration and to delay ovulation when administered to mares. The objectives of Experiment 2 were 1) to determine the effects of subcutaneous or intravenous administration of a GnRH antagonist or oral altrenogest on serum LH concentration in the estrual mare; and 2) to determine the effectiveness of human chorionic gonadotropin (hCG) in inducing ovulation in mares with suppressed LH concentrations. In Experiment 1, mares (N = 20) were randomly assigned and treated with either 5% mannitol (control, single subcutaneous injection, 1 mL, at time 0; n = 5); low-dose GnRH antagonist (single subcutaneous injection, 0.01 mg/kg, at time 0; n = 5); frequent low-dose GnRH antagonist (subcutaneous injections, 0.01 mg/kg, at 0, 6, 18, and 24 hours; n = 5); or high-dose GnRH antagonist (single subcutaneous injection, 0.04 mg/kg, at time 0; n = 5). Both the frequent low-dose and high-dose GnRH antagonist treatments resulted in significantly lower LH concentrations compared with controls at 90, 102, and 114 hours after treatment (P < .05). In Experiment 2, mares (N = 38) were randomly assigned and treated with subcutaneous sterile saline (control), altrenogest (oral), subcutaneous GnRH antagonist, or intravenous GnRH antagonist. LH concentration for the altrenogest group was lower than the control group at 3, 4, 18, and 30 hours after treatment (P < .05). LH concentration for both the subcutaneous and intravenous GnRH antagonist groups were lower compared with the control group at several time points (P < .05). Based on these data, dose but not frequency of administration of a GnRH antagonist lowered LH concentration in the estrous mare but did not delay ovulation. In addition, serum LH concentrations can be lowered and ovulation effectively postponed in mares treated with altrenogest followed by administration of hCG. This indicates that serum LH concentrations can be lowered and ovulation effectively postponed in mares treated with altrenogest followed by administration of hCG.