B-mode ultrasound observations of bull testes during breeding soundness examinations

The testes of 78 adult Beefmaster bulls (13 to > 31 mo old) were scanned with a 5 MHz, linear array portable ultrasound unit during routine breeding soundness examinations. Videotape recordings were used to measure mediastinum testis width and fluid width between visceral and parietal tunics (fluid width), and to count the number of fibrotic foci. Ultrasound results were compared to breeding soundness score parameters, which included total score, age classification, and percentage of primary and secondary sperm abnormalities. The overall mean mediastinum testis width and fluid width were 0.33 cm ± 0.133 and 0.10 cm ± 0.13, respectively; 15 testes had 1–8 fibrotic foci. There were no significant differences in mediastinum testis width and fluid width between left and right testes when compared by breeding soundness score classification or by age classification. There were no significant differences in mediastinum testis width, fluid width, breeding soundness score, or primary or secondary sperm abnormalities in bulls with fibrotic foci compared to bulls without fibrotic foci. There appears to be no significant information that routine testicular ultrasound examination adds to accepted breeding soundness evaluations performed on the same day.     

Reproductive parameters of miniature stallions

Breeding soundness evaluation (BSE) of stallions is a routine component of stud farm practice. Guidelines for assessing satisfactory breeding potential have been developed using data derived from stallions of full-size breeds. In view of the increasing popularity of miniature stallions, knowledge of normal semen parameters of these stallions is important. Therefore, testicular measurements and semen parameters from 216 sexually rested miniature stallions were obtained. Semen was collected twice, 1.5 to 3 h apart, using an artificial vagina. Values were averaged over the 2 collections because of the sexual inexperience of the stallions. The smaller stallions (Group A, 72 to 86 cm; Group B, 87 to 96 cm) had smaller testicles (P<0.05), and Group A stallions had the lowest ejaculate volume (P<0.05) compared with Group C (97 to 104 cm) stallions. Thus, although there was no difference in the concentration of spermatozoa per milliliter between groups of stallions, Group A stallions had fewer total spermatozoa in their ejaculate than Group C stallions (4.31+/-0.47x10(9) vs. 5.41+/-0.30x10(9), P<0.05). Moreover, miniature stallions had smaller testicles and fewer total spermatozoa in their ejaculate than is commonly accepted as normal in full-size stallions. Average total scrotal width of miniature stallions was found to be 7.13, 7.38 and 7.95 cm for Groups A, B and C, respectively. The average total number of spermatozoa in the ejaculates of miniature stallions in this study was 4.94+/-0.22x10(9) cells, with 1.75+/-0.09x10(9) total normal, motile spermatozoa. When only stallions <96.5 cm in height were considered (conforming to requirements of the American Miniature Horse Association Registry), the average total number of spermatozoa in the ejaculates was 4.59+/-0.30x10(9) cells, with 1.70+/-0.11x 10(9) total normal, motile spermatozoa. Based on these findings, different criteria should be used to evaluate the potential breeding soundness of miniature stallions than are commonly applied to full-size stallions.     

Preliminary implications of B-mode ultrasonography of the testicles of beef bulls with normal breeding soundness examinations

Four polled Hereford bulls were found to have satisfactory breeding soundness examinations. They were examined by B-mode ultrasonography, at which time the testicular diameter was measured by ultrasound. The testicles were removed, measured physically and this data was compared with the ultrasound measurements and correlated with other parameters of the breeding soundness examination. The testicles from bulls with normal breeding soundness examinations appeared ultrasonographically identical with the normal testicles from other species such as the pig and dog. Results indicated that the bull testicle diameter could be accurately measured by ultrasonography. Neither ultrasonographic nor physical testicular diameter measurements correlated statistically with scrotal circumference, but they did correlated well with testicular circumference, weight and volume.     

A survey of the fertility of Icelandic stallions

Very limited information is available on the breeding performance of Icelandic stallions, let alone the effect that management practices may have had on such performance. As an extensively kept, largely genetically isolated breed of horse it provides a good model for the study of factors that affect reproductive performance without the additional complication of selective breeding, infectious infertility and breed effect. A survey was conducted using 27 Icelandic stallions covering 1590 mares within the normal Icelandic breeding system (May to September). During the season, stallions cover mares within three periods of time, each period being of a similar length (average 35.5 days). During period 1, mares are covered in hand and at pasture. During periods 2 and 3, all mares are covered at pasture. The overall fertility rate for Icelandic stallions was calculated. The effect of a range of variables on fertility was investigated statistically using a number of models in an attempt to minimise the effect of confounding factors. An overall adjusted fertility rate for Icelandic stallions of 67.7% was obtained. The following factors were shown to have a significant effect on fertility: age of mare (P<0.001), training level of stallion (P<0.05) and method of breeding (P<0.05). For some individual stallions reproductive status of the mare also had a significant (P<0.001) effect. Many of these factors have been observed to effect FR in other more intensively managed equine populations. However, the less dramatic detrimental effect of age and the lack of a significant effect of mare reproductive status in most stallions suggests that infertility problems are less evident in Icelandic mares, possibly due to less emphasis on selection for athletic performance and the accepted culling of subfertile stock.     

Ultrasonography: an important tool in captive breeding management in elephants and rhinoceroses

Nearly two decades ago, modern wildlife medicine started to gradually use the advantages of the non-invasive ultrasonography, which was already well established in human and classical veterinary medicine. For more than one decade now, the application of imaging ultrasound for reproductive assessments and as a supportive tool during assisted reproduction procedures such as artificial insemination (AI) in elephants and rhinoceroses has dramatically improved the breeding success in captive breeding programmes. The opportunity for identifying potential breeding candidates on the basis of their reproductive health status is widely used for natural mating or for AI, today. The longitudinal sonographic monitoring of pathological processes on the internal female genital tract allowed the identification of pathogenetic causes for the rapid infertility development in older nulliparous females. The factors causing temporary infertility in captive male elephants and rhinoceroses were also identified by the use of ultrasound. Today, ultrasonography is the golden standard for reproductive assessments in megavertebrates such as elephants and rhinoceroses in captive management settings and also in the wild.     

Possible negative effects of inbreeding on semen quality in Shetland pony stallions

Inbreeding is widely believed to negatively affect reproductive performance. Indeed, in some species, high levels of inbreeding are thought to be the major cause of poor semen quality. It is, however, not clear whether inbreeding affects fertility in horses. In this study, the relationship between inbreeding and semen quality was examined in 285 immature Shetland pony stallions submitted for breeding soundness examination in March-April of the years 1992-1997. The majority of stallions examined were 3 years old (85%) and their coefficients of inbreeding ranged from 0 to 25% (mean+/-S.D.: 3+/-4.6%). For the purpose of analysis, stallions were divided into six inbreeding classes (0-1, 1-2, 2-5, 5-8, 8-12 and >12%) containing 132, 40, 42, 27, 25 and 19 animals, respectively. The degree of inbreeding significantly affected many aspects of sperm production and quality, based on a standard examination of two ejaculates collected at a 1.5-3h interval. In particular, coefficients of inbreeding above 2% were associated with lower percentages of motile (p<0.01) and morphologically normal sperm (p<0.001). When the data set was used to estimate heritability of semen characteristics, the high values calculated for sperm progressive motility (0.46) and concentration (0.24) suggested that these traits could be improved by phenotypic selection. These findings support the hypothesis that inbreeding has a detrimental effect on semen quality in Shetland ponies, although examination of multiple ejaculates after repeated semen collection to bring the animals to daily sperm output is needed to confirm this conclusion. Nevertheless, the results support previous suggestions that inbreeding is an important cause of reduced semen quality.     

Contagious equine metritis in Australia.

Contagious equine metritis (CEM) was first diagnosed in Australia in August 1977 and it has since been found on 6 farms in 3 states, having been isolated from about 24 mares and 2 stallions. Details are given of the epidemiology and control procedures used to combat CEM on one farm. Difficulty was experience in successfully treating one infected stallion; this was thought to be associated with inadequate cleaning and treating of the diverticulum of the urethral fossa. Introduction of the disease has had far-reaching consequences and may well result in the adoption of routine bacteriological tests on stallions and mares of unknown or dubious breeding history and other measures to minimize the possibility of spread between farms.     

Capacitation, acrosome function and chromatin structure in stallion sperm

In general, fertility in breeding stallions is lower and more variable than in the other farm animal species, primarily because selection is based on pedigree, looks and/or athletic performance, with little consideration of fertility or fertility potential. Moreover, because the average stallion breeds only a limited number of mares per year and in-field fertility is influenced significantly by non-stallion factors such as management and mare fertility, meaningful fertility data are hard to come-by. Unfortunately, generating usable figures would involve impractically high costs, time and numbers of mares. Instead, a breeding soundness examination (BSE), based on assessments of sperm number, motility and morphological normality and of mating ability, is often carried out with the ostensible aim of identifying animals with the "potential for good fertility". In fact, the BSE generally succeeds only in ruling out those stallions with a very clear reason for sub-fertility, and still fails to identify some seriously sub-fertile animals. Thus, the routine BSE has very limited use as a predictor of subsequent fertility. This paper reviews assays developed for identifying capacitated, acrosome-reacted and DNA-damaged sperm, and assesses their utility for improving our ability to predict a stallion's fertility prior to the onset of his breeding career.     

阴道超声与宫腔镜诊断对围绝经期女性异常子宫出血病因的研究对比

目的:研究阴道超声与宫腔镜诊断对围绝经期女性异常子宫出血(Abnormal uterine bleeding,AUB)病因的对比。方法:从2012年3月到2013年3月,我院共有123例围绝经期AUB患者需行手术治疗。全部患者均于术前实施阴道超声检查及宫腔镜检查,分别归入阴道超声组及宫腔镜组,并于术后常规实施病理确诊,并将所得结果作为金标准分别对比。结果:根据术后的病理检查,最终确定患者子宫内膜为正常者4例,内膜增生44例,内膜息肉29例,黏膜下肌瘤26例,内膜癌20例。宫腔镜组在内膜增生及内膜息肉方面的诊断结果与病理检查结果最为接近,诊断结果显著优于阴道超声组,差异均有统计学意义(均P0.05)。但两组在正常内膜、黏膜下肌瘤以及内膜癌等方面的诊断结果对比,差异均无统计学意义(均P0.05)。宫腔镜组与病理检查的符合率在黏膜下肌瘤及内膜癌方面较阴道超声组与病理检查结果的符合率更高,但差异无统计学意义(P0.05)。尤其是关于内膜增生和内膜息肉的符合率,宫腔镜组显著高于阴道超声组,差异有统计学意义(均P0.05)。结论:宫腔镜诊断方案对于围绝经期女性AUB患者的诊断结果更接近于病理结果,但临床在一定条件可与阴道超声联用,以期进一步提升诊断符合率。值得临床推荐。     

A polymorphism within the equine CRISP3 gene is associated with stallion fertility in Hanoverian warmblood horses

Fertility of stallions is of high economic importance, especially for large breeding organisations and studs. Breeding schemes with respect to fertility traits and selection of stallions at an early stage may be improved by including molecular genetic markers associated with traits. The genes coding for equine cysteine-rich secretory proteins (CRISPs) are promising candidate genes because previous studies have shown that CRISPs play a role in the fertilising ability of male animals. We have previously characterised the three equine CRISP genes and identified a non-synonymous polymorphism in the CRISP1 gene. In this study, we report one non-synonymous polymorphism in the CRISP2 gene and four non-synonymous polymorphisms in the CRISP3 gene. All six CRISP polymorphisms were genotyped in 107 Hanoverian breeding stallions. Insemination records of stallions were used to analyse the association between CRISP polymorphisms and fertility traits. Three statistical models were used to evaluate the influence of single mutations, genotypes and haplotypes of the polymorphisms. The CRISP3 AJ459965:c.+622G>A SNP leading to the amino acid substitution E208K was significantly associated with the fertility of stallions. Stallions heterozygous for the CRISP3 c.+622G>A SNP had lower fertility than homozygous stallions (P = 0.0234). The pregnancy rate per cycle in these stallions was estimated to be approximately 7% lower than in stallions homozygous at this position.     

Retrospective and statistical analysis of breeding management on the Italian Heavy Draught Horse breed

This study investigated some aspects of breeding management in the Italian Heavy Draught Horse breed, aiming at improving its efficiency at stud farm level. A first aim was to evaluate the risk of unsuccessful reproduction in mares after an early (3 years) or normal (4 years) age at first foaling, in interaction with different stud rearing systems. A second objective was the examination of the mean time length in which young 2-year-old stallions maintain a genetic superiority on older proven stallions, identifying a ‘genetic lifespan’ in which young stallions can be safely used for reducing the cost of services. Reproductive performance at first and second foaling of 1513 mares were used. Mares had a normal first foal at 3 (n = 745) or 4 years of age (n = 768) in stud farms on the basis of stable (n = 488), feral (n = 345) or semi-feral (n = 680) rearing systems. Logistic regression analysis was performed by modeling the risk of unsuccessful reproduction in the subsequent season (i.e., results at second foaling), as affected by the interaction of age at first foaling × rearing system (six classes). Genetic lifespan of young stallions was estimated by regressing the least square means from a mixed model analysis for repeated measures of individual differences in ‘total merit’ estimated breeding values (EBVs) between young stallions (mean no. of 45/year) and the mean EBV of all proven stallions in a given year of genetic evaluation (mean no. of 483/year). Young stallions born between 1999 and 2005 were used, following each generation (i.e., birth year) from 2 to 7 subsequent yearly genetic evaluations. In comparison with the best reproductive success of second foaling at 4 years in stable systems, the greatest risk of unsuccessful reproduction was at 3 years in feral (+167%) and 3 years in semi-feral conditions (+91%). Young stallions showed a 0.50 s.d. greater EBV at the first evaluation than proven stallions, with a mean annual decrease in EBV of 0.07 s.d./year on proven stallions. Optimal breeding management could be obtained in stud farms by limiting foaling at 3 years, particularly in feral and semi-feral rearing systems, and using young stallions for 3 to 4 years to maintain a perceptible selection differential with older proven stallions and to reduce cost of services. Later, the selection differential with proven stallions become less consistent and genetic improvement could be slowed down.     

Endocrine and ultrasound evaluation of a non‐cycling African elephant: Identification of an ovarian follicular cyst

The reproductive rate of captive African elephants is low because of logistical difficulties associated with transporting animals for breeding, the danger of maintaining bulls and medical or physiological problems. There also is growing evidence that a significant number of mature female elephants are not experiencing normal estrous cycles. The case described in this report involves the diagnosis and attempted treatment of an ovarian follicular cyst in an African elephant at the Pittsburgh Zoo. On the basis of serum progesterone analysis, the female exhibited regular ovarian cycles from July 1993 through March 1994, but from November 1994 to the present has not shown any evidence of reproductive cyclicity. In April 1996, a large follicular structure was identified on the right ovary using transrectal ultrasound. In an attempt to luteinize the cyst, 500 μg gonadotropin‐releasing hormone (GnRH) was administered intravenously in October 1996, which stimulated a modest increase in serum luteinizing hormone (LH) (approximately twofold over baseline), but no resumption of ovarian activity. The elephant was treated again 5 months later with a higher dose of GnRH (5 mg, i.v.) with the same results. An ultrasound evaluation in July 1997 indicated the structure was still present. In October 1997, the female was given human chorionic gonadotropin (hCG; 10,000 IU, i.m.), which induced estrus and breeding, but no ovulation or luteinization of the cyst, and she remains acyclic. These results suggest that conventional methods developed in other species for treating ovarian follicular cysts may not necessarily be effective in the elephant. It is also important that reproductive age females be monitored via continuous progesterone analysis and occasional reproductive tract ultrasound evaluations to understand better the etiology of ovarian dysfunction so that effective treatments can be developed to induce consistent ovarian activity. Zoo Biol 18:223–232, 1999. © 1999 Wiley‐Liss, Inc.     

Tests for cooperative behaviour between stallions

Breeding groups with multiple stallions occur sympatrically with single-stallion breeding groups in feral horse, Equus caballus, populations. Mutualism and reciprocal altruism between stallions have been proposed to explain the origin and functioning of multistallion bands. However, empirical support for these hypotheses is contradictory and incomplete. Furthermore, there are no explicit tests of the predictions that each hypothesis makes about stallion behaviour and social structure. We compared nine multistallion and 18 single-stallion bands in the Kaimanawa Ranges, New Zealand. Compared with agonistic behaviours, affiliative behaviours were relatively unimportant in the relationships between stallions within bands. The number of stallions in the band did not have a positive influence on mare group size, stability, home range quality or reproductive success in bands. Furthermore, there was a positive relationship between aggression ('intolerance') by the dominant towards subordinate stallions and the subordinates' effort in mare group defence ('helping') but a negative relationship between helping effort by subordinates and their proximity to, and mating with, the bands' mares. Therefore, the predictions of the mutualism and reciprocal altruism hypotheses were not supported. Indeed, for some of the predictions we found the opposite outcomes to be true. Multistallion bands had significantly poorer reproductive success, and dominant stallions were less tolerant of subordinates that helped most and reduced their access to mares. Nevertheless, in all other respects Kaimanawa stallions in multistallion bands behaved like those described elsewhere. Thus, we reject cooperative hypotheses for multimale breeding groups in horses and discuss the mate parasitism and consort hypotheses as better alternatives. Copyright 2000 The Association for the Study of Animal Behaviour.     

B-mode ultrasonographic examination of the accessory sex glands of boars

Thorough examinations of the reproductive system of boars are generally not performed on normal boars to be used for breeding; only boars with problems undergo a form of a breeding soundness examination. In order for veterinarians to identify pathological conditions, the normal architecture of the accessory sex glands needs to be described. The purpose of this study was to use B-mode ultrasonography to describe the accessory sex glands in the boar and to see if transrectal ultrasonography would be a viable option in which to obtain this data. Initially, cross-sectional saline bath examinations of accessory sex glands were performed on crossbred boar reproductive tracts (n = 4) using B-mode ultrasonography equipped with a 5 MHz dual frequency linear array transducer. In situ examinations were also performed on terminal line crossbred boars (n = 16) ranging in age from 10 to 23 months old using the same ultrasound methodology; four boars were under general anesthesia and the remaining 12 were standing in crates. Eight boars were abstinent for 2 days and the other eight had ejaculates collected 2 h prior to examination. The paired bulbourethral glands are best described as a long oval gland with a uniformly echogenic appearance with a large anechoic space in the center of the gland extending most of its length. The walls of the vesicular glands were found to be thin, with the parenchyma having multiple small echolucent areas that appeared to merge and form a central canal. The prostate gland was best identified as a pecan-sized gland with a uniform echogenic appearance. Visualization of the prostate gland was accomplished with more proficiency using the saline bath ultrasonography as compared to in situ examinations. All of the accessory sex glands could be examined using both methodologies of ultrasonographic examination with a 5 MHz frequency linear array transducer. It was determined that each accessory sex gland could be recognized, and differences between ejaculated and nonejaculated boars could be identified. The results of this study demonstrate that transrectal ultrasonography can be used as a diagnostic aid in assessing the accessory sex glands of boars.     

A description of the findings from bull breeding soundness evaluations and their association with pregnancy outcomes in a study of western Canadian beef herds

The primary objectives were to describe beef bulls considered for use and those reported as used in 205 beef herds in western Canada, and to determine whether factors typically assessed during breeding soundness evaluations were associated with reproductive success. More than 100 veterinary clinics reported 2990 breeding soundness evaluations for bulls considered for natural service in client's herds. Differences among clinics explained 5.2% of the variation in scrotal circumference (SC) and 6.9% of the variation in percentage of morphologically normal sperm of all bulls considered for use (after accounting for age, breed, body condition, significant physical abnormalities, month, and year). The percentage of morphologically normal sperm was lower in bulls with an SC ≤34 versus >34 cm (P < 0.006). This study included data from 1384 and 1370 bulls used for breeding in 2001 and 2002, respectively. Most (80%) of the bulls used were Simmental, Black Angus, Charolais, Red Angus, or Hereford, and 80% were ≤4 y of age. Before the breeding season, a veterinarian evaluated 89.5% of all bulls used in these herds. Of the bulls subjected to a breeding soundness evaluation and subsequently used, 93.1% were satisfactory. In 2001 and 2002, injuries were reported in 2.5 and 2.1% of bulls and in 16.6 and 11.4% of herds, and necrobacillosis of the foot was reported in 2.5 and 1.2% of bulls and 11.2 and 6.5% of the herds. The average number of cows exposed to each bull was 26 (both years). Cows exposed to bulls with a smaller SC were less likely to be diagnosed pregnant (P < 0.047) and had a longer median interval from first bull exposure to calving (P < 0.016) than bulls with a larger SC. In conclusion, our findings emphasized the value of breeding soundness evaluations, including measurements of SC, in fertility management of beef cattle.     

Morphological and biochemical alterations in reproductive tracts of neonatal female mice treated with the pesticide methoxychlor

Effects of estradiol-17 beta and the estrogenicity of different doses of the technical grade pesticide methoxychlor were compared in the vagina, uterus, and oviducts of neonatal mice. Beginning within 24 h of birth, neonates received 10 daily i.p. injections of sesame oil vehicle, 10.0 micrograms estradiol, or 0.05, 0.1, 0.5, or 1.0 mg methoxychlor. Estradiol injections induced precocious vaginal opening, complete vaginal cornification, and increased total reproductive tract weight and its DNA content. In comparison to the controls, the three highest methoxychlor doses also significantly increased the weights of the reproductive tracts and stimulated their development. The two highest doses (0.5 and 1.0 mg) also induced precocious vaginal opening and complete vaginal cornification. In addition, the same two doses produced atypical cells in the uterus and oviducts that may be indicative of early dysplasia; similar atypia were not recorded following estradiol treatments. Total DNA content in various reproductive organs increased with increased methoxychlor dosages. Dose-response changes were observed in the oviduct and uterus but not vagina. In summary, methoxychlor stimulated the development of neonatal female reproductive tracts, even at concentrations not previously reported to be biologically active. Furthermore, the higher doses induced abnormalities that were not seen following estradiol treatment; these abnormalities may represent precursors of pathological changes.     

Transrectal real-time ultrasound scanning of the cow reproductive tract

A transrectal real-time ultrasound scanning of the cow reproductive tract allows the operator to view images of structures which normally can be only palpated. The device used in these studies allowed exact evaluation of the cow reproductive tract for position, size and consistency of ovaries, uterus and fetuses; these parameters cannot be described to this level of exactness even by the most skilled palpators. This paper describes real-time ultrasound scanning of an ovary containing a cystic corpus luteum and several follicles and ofa nonpregnant and a pregnant tract at different stages of gestation. The device may be expected to aid both the researcher and the practicing veterinarian considerably in the future.     

Exposure to stallion accelerates the onset of mares' cyclicity

Horses (Equus caballus) belong to the group of seasonally polyestrous mammals. Estrous cycles typically start with increasing daylight length after winter, but mares can differ greatly in the timing of onset of regular estrus cycles. Here, we test whether spatial proximity to a stallion also plays a role. Twenty-two anestrous mares were either exposed to one of two stallions (without direct physical contact) or not exposed (controls) under experimental conditions during two consecutive springs (February to April). Ovarian activity was monitored via transrectal ultrasound and stallion's direct contact time with each mare was determined three times per week for one hour each. We found that mares exposed to a stallion ovulated earlier and more often during the observational period than mares that were not exposed to stallions. Neither stallion identity nor direct contact time, mare age, body condition, size of her largest follicle at the onset of the experiment, or parasite burden significantly affected the onset of cyclicity. In conclusion, the timing of estrous cycles and cycle frequency, i.e., crucial aspects of female reproductive strategy, strongly depend on how the mares perceive their social environment. Exposing mares to the proximity of a stallion can therefore be an alternative to, for example, light programs or elaborated hormonal therapies to start the breeding season earlier and increase the number of estrous cycles in horses.     

Toll-like receptors and their role in animal reproduction

Toll-like receptors (TLRs) are evolutionarily conserved innate immune receptors that recognize pathogen specific molecular pattern (PAMPs) in an efficient, non-self-reactive manner and initiate specific immune signaling that culminates in triggering antigen-specific adaptive responses. Different TLR genes in domestic animal species have been characterized and accumulating evidence from recent studies indicates an extended role for TLR signaling in reproductive physiology. In females, TLRs have been implicated in the regulation of ovulation, fertilization, gestation and parturition, as well as in pathological conditions such as endometritis and mastitis. In males, TLRs play a role in steroidogenesis and spermatogenesis. Use of TLR agonists has also been shown to be effective in the treatment of certain reproductive tract infections. Moreover, gene polymorphisms in TLRs have been associated with mastitis providing evidence that TLRs can potentially be exploited as markers in future breeding programs. The aim of this review is to provide a comprehensive treatise on role of TLRs in male and female reproductive physiology and associated pathology in domestic livestock.     

Bull influences on conception percentage and calving date in Angus Hereford, Brahman and Senepol single-sire herds

Bull breeding soundness parameters, semen characteristics and sexual behavior were evaluated for effects on reproductive performance in single-sire beef herds. A total of 155 cow herds (Angus, 50 herds; Hereford, 40 herds; Brahman, 46 herds; and Senepol, 19 herds) bred to bulls of the same breed were observed for 8 yr. All bulls produced adequate quality semen and had scrotal circumference (SC) >/= 30 cm. Reproductive performance was evaluated by the conception rate (CON), conception rate during the first 21 d of the breeding season (21dCON), mean calving date (MCD), and mean calving date of the first half of the herd to calve (HHCD). Correlations were determined between breeding soundness parameters and reproductive performance for all bulls combined, by breed, and by age. The Cp statistic was used to select models for the effects of parameters on CON, 21dCON, MCD and HHCD. Breeding season length and breed had significant effects. The percentages of normal cells, proximal droplets, detached heads and the semen score (motility plus percentage of normal cells) had a significant effect on CON when all bulls were considered. After the effect of season was deleted, the most significant parameter affecting CON in the Brahman was the percentage of detached sperm heads. In the Angus, motility was significantly correlated with all reproductive performance indices. In the Hereford, breeding soundness examination score (BSE) was positively correlated with 21dCON.