Prior exposure of maiden ewes to rams enhances their behavioural interactions with rams but is not a pre-requisite to their endocrine response to the ram effect

In this study, we tested whether prior experience with rams would modify the behavioural and endocrine responses of maiden ewes to rams. During mid-anoestrus, sexually na?ve, maiden ewes were exposed to rams for 7 days (ram experienced, RE; n=61) or isolated from rams (ram na?ve, RN; n=63). All ewes were subsequently isolated from rams. In Experiment 1, RE (n=55) and RN (n=57) ewes were introduced to rams during late anoestrus. RE ewes had more total and positive interactions with rams than RN ewes (P<0.001). RE ewes showed more ram seeking behaviour and spent more time in proximity of rams than RN ewes (at least; P<0.05). In Experiment 2, RE (n=6) and RN (n=6) ewes were introduced to rams midway through a frequent blood sampling regime in late anoestrus. Ram introduction stimulated an increase in LH pulse frequency and basal LH in both RE and RN ewes (at least P<0.05). RE ewes had an increase in mean LH concentrations (P<0.01) that failed to reach significance in RN ewes (P<0.1). There was no significant effect of prior experience with rams on LH pulse frequency, amplitude or whether ewes had an LH surge. In conclusion, prior experience with rams is important in developing appropriate ewe-ram interactions but is not a pre-requisite to the endocrine response to the ram effect.     

A note on ram preference by oestrous ewes: Influence of rams’ age and sexual performance

Ewes in oestrus, besides being receptive to rams, develop an active search for them. We performed two experiments to determine if oestrous ewes prefer: (1) high or low sexual-performance rams, and (2) 2-year-old or aged (>8-years-old) rams. In the first experiment, the preference of ewes for rams with high or low sexual performances was compared in 16 tests. In the second experiment, 17 tests were performed comparing ewes’ preference for aged rams (>8-years-old) or young rams (2-years-old). In each test, two rams were tied at equal distances from the point of entrance of the ewe, with a maximum mobility for each ram of 2 m. The first approach to a ram, the quantity of approaches toward each ram (less than one body length), and the total time that the ewe remained near each ram were registered during 5 min. Oestrous ewes did not display any preference according to sexual performance of rams, but spent significantly more time (P = 0.02), and did it in more tests (P = 0.025), with young than with aged rams. Ewes also tended to approach first (P = 0.07), and more times in more tests (P = 0.06), to young than to aged rams. We conclude that ram's sexual performance seems not to influence oestrous ewes preference, and that ewes’ prefer young (2-years-old) rather than aged rams (>8-years-old).     

The contribution of the male to ovine embryogenesis in an in vitro embryo production system

The differences in the embryo production potential of four rams used in a commercial embryo transfer program were examined in both in vivo and in vitro embryo production systems. Processing frozen-thawed spermatozoa through Percoll density gradients prior to in vitro insemination eliminated differences in the estimates of sperm viability between the four rams, and yet, differences in embryo production persisted throughout the in vitro culture period. However, there was no effect of ejaculate within ram on embryo production rates. In addition, the timing of the onset of the differences between the rams at each stage of in vitro embryo development were revealed. Ram 2 differed from ram 4 in the proportion of fertilized oocytes at 17 h post-insemination (pi) and by 52 h, ram 3 differed from ram 4 in the proportion of cleaved embryos, and the observed differences between ram 1 and ram 2 in their blastocyst production were initiated prior to activation of the embryonic genome. Once differences in embryo development rates were detected among the four rams, they persisted throughout the in vitro culture period. The reduced in vitro fertilization (IVF) rates from ram 2 compared with the other rams was paralleled in vivo by the significantly lower proportion of embryos recovered from ewes mated to ram 2, and this was further exacerbated by a significantly lower embryo survival rate after transfer. However, the subtle differences observed in the timing of the contribution of each sire to embryo development during in vitro culture were not able to be detected in vivo. However, the higher proportions of transferable quality blastocysts obtained from ewes mated to ram 4 did not result in increased embryo survival throughout the remainder of gestation. Therefore, in this study, the blastocyst production potential for a particular sire, either in vitro or in vivo, does not necessarily reflect the potential for the production of live offspring.     

Sheep breeding schemes utilising artificial insemination; large-scale simulation with a complex breeding goal

Alternative Norwegian sheep breeding schemes were evaluated by stochastic simulation of a breeding population with about 120 000 ewes, considering the gain for an aggregate genotype including nine traits and also the rate of inbreeding. The schemes were: a scheme where both young unproven rams (test rams) and proven rams (elite rams) are used in artificial insemination (AI scheme), a scheme with test rams in natural mating in ram circles and elite rams (from one and a half years of age) in AI across all flocks in the country (NMAI2 scheme), a scheme where, in addition to testing rams, the youngest elite rams (one and a half years of age) are also used in natural mating in ram circles, while older elite rams are used in AI (NMAI1 scheme), and a scheme, acting as a control, where both test and elite rams are used in natural mating (NM scheme). Within the NMAI- and AI-schemes, experimentation was performed for percent ewes inseminated to elite rams v. test rams (EM%), numbers of ewes inseminated per elite ram (EAIn), and numbers of ewes mated per test ram by natural service (TNMn) or by AI (TAIn), respectively. With a restriction on the rate of inbreeding (⩽0.8% per generation), the AI scheme gave similar gain to the NMAI2 scheme (and about 40% more than did the NM scheme). Less gain was generated by the NMAI1 scheme, but it was still considerably more than for the NM scheme (about 25%). In the AI scheme, relatively few ewes (200/300) should be inseminated to each test/elite ram, and a low EM% should be chosen (10%). In the NMAI schemes, TNMn should be relatively high (40 to 50), combined with average and somewhat larger than average EAIn (NMAI2: 700 ewes, NMAI1: 900 ewes), and EM% medium (30%).     

Reproductive response and LH secretion in ewes treated with melatonin implants and induced to ovulate with the ram effect

Two experiments were conducted to examine the effects of treating seasonally anoestrous ewes with melatonin before ram introduction on reproductive response, and on LH secretion in anoestrous ewes induced to ovulate by rams.In Experiment 1, a total of 667 ewes from three flocks involving Merino (Flock 1, N = 149), Merino entrefino (Flock 2, N = 325) and Rasa Aragonesa (Flock 3, N = 203) breeds were used. Within each flock, ewes isolated from rams since the previous lambing were assigned at random to receive melatonin implants of Regulin (75, 175 and 105 in Merino, Merino entrefino and Rasa Aragonesa flocks, respectively) or to serve as untreated controls (74 in Merino, 150 in Merino entrefino and 98 in Rasa Aragonesa flocks). Fertile rams were introduced into all flocks 5 weeks after implantation in March (Flocks 1 and 2) or April (Flock 3), and remained with the ewes for a 50 day mating period. Percentage of ewes with luteal activity at ram introduction did not differ between melatonin treated and control ewes in any flock. There were no significant differences in either the mean interval from ram introduction to lambing or the distribution of lambing. Implantation with melatonin resulted in an improvement of prolificacy in all three flocks, although this only reached statistical significance in the Merino flock (1.15 vs. 1.03 in treated and control ewes, respectively, P < 0.05). Fertility was increased significantly (P < 0.05) in the Merino entrefino flock (64.5% in treated vs. 51.3% in control ewes).In Experiment 2, two trials were undertaken utilizing a total of 63 ewes. Trial 1 involved 24 mature Manchega ewes and Trial 2 involved 39 Merino ewe lambs. Half of the animals in each trial received a Regulin implant on 28 February (Trial 1) or 12 March (Trial 2) and the remaining half acted as controls. Rams were introduced 5 weeks after implantation and remained with the ewes for a 25 day period. In both trials, anoestrous ewes at ram introduction were bled at 20 min intervals for 3 h before and 5 h after ram introduction and then at 3 h intervals over the next 24 h for assessment of plasma concentrations of LH. Secretion of LH before or following introduction of rams was not affected by melatonin. Both treated and control anoestrous ewes in each trial responded to introduction of rams with an increase in the frequency of the LH pulses (P < 0.05), but no significant changes were detected in pulse amplitude or mean levels of LH. A preovulatory surge of LH was detected between 8 and 26 h after ram introduction, but neither mean interval from ram introduction to the peak of LH surge, nor the magnitude of the LH peak, was influenced by melatonin treatment.Results from this study show that: (1) melatonin implants administered during early seasonal anoestrus have the potential to improve reproductive performance in Spanish breeds of sheep, but the response is conditioned by breed, management system and environmental factors; (2) melatonin did not modify the secretion of LH in anoestrous ewes induced to ovulate by the ram effect under our experimental conditions.     

Heritability of ram mating success in multi-sire breeding situations

Multi-sire mating of a mob of ewes is commonly used in commercial sheep production systems. However, ram mating success (defined as the number of lambs sired by an individual) can vary between rams in the mating group. If this trait was repeatable and heritable, selection of rams capable of siring larger numbers of lambs could reduce the number of rams required for mating and ultimately lead to increased genetic gain. However, genetic correlations with other productive traits, such as growth and female fertility, could influence the potential for ram mating success to be used as a selection trait. In order to investigate this trait, parentage records (including accuracy of sire assignment) from 15 commercial ram breeding flocks of various breeds were utilised to examine the repeatability and heritability of ram mating success in multi-sire mating groups. In addition, genetic and phenotypic correlations with growth and female fertility traits were estimated using ASReml. The final model used for the ram mating success traits included age of the ram and mating group as fixed effects. Older rams (3+years old) had 15% to 20% greater mating success than younger rams (1 or 2 years of age). Increasing the stringency of the criteria for inclusion of both an individual lamb, based on accuracy of sire assignment, or a whole mating group, based on how many lambs had an assigned sire, increased repeatability and heritability estimates of the ram mating success traits examined. With the most stringent criteria employed, where assignment of sire accuracy was >0.95 and the total number of lambs in the progeny group that failed to have a sire assigned was<0.05, repeatability and heritability for log_e(number of lambs) was 0.40±0.09 and 0.26±0.12, respectively. For proportion of lambs sired, repeatability and heritability were both 0.30±0.09. The two ram mating traits (log_e(nlamb) and proportion) were highly correlated, both phenotypically and genetically (0.88±0.01 and 0.94±0.06, respectively). Both phenotypic and genetic correlations between ram mating success and growth and other female fertility traits were low and non-significant. In conclusion, there is scope to select rams capable of producing high numbers of progeny and thus increase selection pressure on rams to increase genetic gain.     

Effect of early and late exposure to estrual ewes on ram sexual performance classifications

This study was conducted to determine whether exposure of ram lambs to estrual ewes during their first autumn and again as adults just before serving capacity tests (SCT) affected the outcome of the sexual performance tests. Treatments were either early exposure of Polypay ram lambs (i.e., 7-8-mo-old rams with ewes for 17 d [n=30] or no early exposure [n=30]), and late exposure (i.e., 16-19-mo-old rams with estrual ewes for 3 d) or no exposure to estrual ewes in a 2x2 factorial arrangement. Three serving capacity tests were conducted immediately after the early exposure period for individual ram lambs that were exposed to ewes early. Three sham sexual performance tests (i.e., four ram lambs placed in test pens for 30-min without ewes) were conducted with ram lambs that were not exposed to ewes early. All rams were evaluated during nine 30-min serving capacity tests over a 2-mo period at 16-19 mo of age to determine sexual performance. Prior to serving capacity tests, one half of the rams from each early exposure treatment were exposed to estrual-induced ewes for 3 d. Specific sexual behaviors (e.g., sniffs, flehmens, foreleg kicks, vocalizations, mount attempts, mounts, and ejaculations) were recorded during serving capacity tests. Number of sniffs, flehmens, foreleg kicks, vocalizations, and mount attempts were summed without estimating the value of importance and analyzed as courtship behaviors. Sexual performance data were analyzed with Mixed model procedures for repeated measures. During serving capacity tests, the early exposed rams exhibited more courtships (40.3+/-8.0 versus 23.4+/-4.6; P<0.05; LSM+/-estimated SE), mounts (11.3+/-1.0 versus 7.7+/-0.9; P<0.01), and ejaculations (3.3+/-0.2 or 2.4+/-0.2; P<0.01) than rams not exposed to ewes as ram lambs, respectively. We conclude that early exposure of 7-8-mo-old ram lambs to estrual ewes improves sexual performance in serving capacity tests at 16-19 mo of age in most rams whereas, late exposure to estrual ewes for 3 d prior to serving capacity tests did not improve sexual performance scores.     

Effect of breed and age on sexual behaviour of rams

The objective of this study was to highlight the problems that arise during the reproduction between thin-tailed rams and fat-tailed ewes. At the same time, particular emphasis laid on the influence of sheep breed, sheep age, time after ram introduction and day of the ewe estrus cycle on ram and ewe sexual behaviour. Rams were subjected to sexual performance tests by being individually exposed to 12 ewes for 3 h daily, 19 consecutive days. The 16 rams of the experiment were separated according to their age (9 and 21 months old) and breed (Chios and Karagouniki), and the 96 ewes of Chios fat-tailed breed, were divided by age (9 and 21 months old). The main characteristics of courtship behaviour, like sniffing, nudging, flehmen response and following were recorded and studied in detail. Mature Chios rams, which were the only one with previous experience of Chios ewes, exhibited higher rates of sexual interest per ewe than the other rams (P < 0.05). On the other hand, rams sniffed and nudged more young than mature ewes (P < 0.05), probably due to the fact that young ewes did not express intense symptoms of estrus. Young rams exhibited substandard sexual interest towards mature ewes, when they first came in contact with them (P < 0.05). In general, Karagouniki thin-tailed rams exhibited reduced rates of mating behaviour when they courted with Chios fat-tailed ewes in comparison with Chios rams (P < 0.05). Moreover, as the time after ram introduction passed, the frequency and duration of sexual behaviour components decreased (P < 0.001). Finally, the effect of the day of the experiment was only significant in the case of sniffing, which increased during the first 2 days and then declined and stabilized (P < 0.01). As it was demonstrated, ram age and ram breed played a fundamental role in the exhibition of sexual interest elements.     

Influence of classification levels of ram sexual activity on spring breeding ewes

Ram lambs (7–8 months old) and mature rams (19–20 months old) were used to evaluate the effect of classification levels of male sexual performance on reproductive performance of ewes during spring breeding. In Exp. 1, sexually active ram lambs with high (1.8±0.3; n=5) and low (0.9±0.2; n=5) sexual performance scores (HP and LP; mean±S.E.M.) were used in single sire breeding pens. Ewes (n=305) were stratified by age and assigned to 10 pens for 34 days starting in late March. For Exps. 2 and 3, two replicates were conducted for 2 years with sexually active mature rams in a single sire mating scheme. For Exp. 2, HP rams (n=5) averaged 3.6±0.2 ejaculations and LP rams (n=7) 1.8±0.2 ejaculations for sexual performance scores based on nine, 30 min serving capacity tests (SCT). Polypay ewes (n=152 to 153 per year) were stratified by age and assigned to pens each year for 34–38 days starting in late March for years 1 and 2. For Exp. 3, HP rams (n=6) averaged 3.7±0.1 ejaculations and LP rams (n=10) 2.3±0.1 ejaculations for sexual performance scores based on 18, 30 min SCT. Polypay ewes (n=229 in year 3 and n=244 in year 4) were stratified by age and assigned to pens each year for 34 days starting in late March. In Exp. 1, lambing rates for ewes bred to HP versus LP ram lambs did not differ (65.8 versus 53.0; P=0.20). Prolificacy tended (P=0.06) to be increased by 0.1 lambs in ewes bred by LP ram lambs. Total number of lambs born per ewe present at lambing, and lambing distribution were not altered by HP and LP ram lambs. In Exp. 2, lambing rates for fall-lambing ewes bred to mature HP or LP rams did not differ (58.1 versus 60.1; P=0.78). In Exp. 3, lambing rates for fall-lambing ewes bred to mature HP or LP rams did not differ (74.3 versus 69.0; P=0.35). There was no difference (P>0.10) between years for Exp. 2 or Exp. 3, and mature HP and LP rams did not affect the other reproductive variables monitored. Analyses of the combined data for Exps. 2 and 3 indicated only a year difference (P<0.001) in lambing rates and total lambs born. Present studies indicate that different sexual performance classifications for ram lambs and mature rams did not alter lambing rates or distribution of lambing of Polypays bred in late March to April. These results indicate that HP and LP, sexually active, Polypay rams and ram lambs with average to high quality semen can provide a source of rams for spring breeding Polypays in ambient conditions and that there was no advantage to using HP over sexually active LP ram lambs or rams.     

Short term, repeated exposure to rams during the transition into the breeding season improves the synchrony of mating in the breeding season

The ram effect is widely used in Mediterranean breeds of sheep but its use in temperate genotypes is restricted by breed seasonality. However, ewes from these highly seasonal genotypes are sensitive to stimulation by rams close to the onset of the natural breeding season. In this study we developed a pre-mating protocol of repeated, short-term exposure to rams (fence-line contact or vasectomised rams) beginning during late anoestrus and continuing into the breeding season. We hypothesised that this pre-mating protocol would synchronise the distribution of mating of North of England Mule ewes during the breeding season above that observed in ewes isolated from rams prior to mating. Ram-exposed ewes were given contact with rams (Experiment 1: fence-line; FR, n = 94 and Experiment 2: vasectomised rams; VR; n = 103) for 24 h on Days 0 (10 September), 17 and 34 of the experiment. Control ewes (Experiment 1; FC, n = 98 and Experiment 2; VC; n = 106) remained isolated from rams prior to mating. In Experiment 2, a subset of VR (n = 35) and VC ewes (n = 35) were blood sampled twice weekly to monitor their pre-mating progesterone profiles. At mating, harnessed entire rams were introduced, 17 or 16 days after the last ram exposure (Experiments 1 and 2) and raddle marks were recorded daily. The median time from ram introduction to mating was reduced in ewes given both fence-line and vasectomised ram contact (P < 0.001), leading to a more compact distribution of mating and lambing (At least P < 0.01). In the blood sampled VR ewes, there was a progressive decline in the number of days from ram exposure to the onset of dioestrus (at least P < 0.05). This observation indicates that the cycles in VR ewes became increasingly synchronised over the pre-mating period, a pattern not evident in VC ewes. In conclusion, repeated, short-term exposure of ewes to rams during the transition into the breeding season is an effective method of synchronising the distribution of mating during the breeding season.     

Mating behavior, serum testosterone and semen characteristics in vasectomized and short scrotum rams

Ten similar rams were either vasectomized (VAS) or altered by securing the testes near the abdomen using elastrator bands (short scrotum, SS). Semen characteristics (electroejaculation) were similar (P>0.10) between groups before treatment and ejaculate volumes remained relatively constant (P>0.10) throughout the trial. Remaining sperm cells were nonmotile and 95% abnormal by 6 days after vasectomy. By 12 days after surgery, ejaculates contained no cells. Two SS rams had detectable sperm numbers at 12 days after treatment, but 95% were abnormal and all but 1% were nonmotile. Ejaculates collected 3 months after surgery were similar between treatments, in that all existing cells were nonmotile and abnormal. Partial spermatogenic function was regained in SS rams 15 months after treatment as indicated by the presence of low concentrations of motile sperm. Three and 15 months after treatment, sexual activity was estimated by exposing rams to a group of four estrous ewes. During the 15-minute exposure, VAS males exhibited more (P<0.10) nonmating sexual approaches than did SS animals during the first year. However, nonmating approaches and incomplete and completed matings were similar (P>0.10) between VAS and SS rams during the second year. No treatment differences in serum testosterone were observed before, during or after either libido trial. Shortening the scrotum of 6-month-old ram lambs has little effect on libido or testosterone when compared with VAS rams. However, the SS method of alteration does not result in complete sterility as indicated by the presence of motile spermatozoa in ejaculates 15 months after SS treatment.     

Seasonal variation in testes size in Polish Merino rams and its relationship to reproductive performance in spring

Observations relating testes size to body weight in growing and adult Polish Merino rams were performed during 3 consecutive years in a flock of 1700 pedigree ewes. October-born ram lambs were measured for testis diameter (TD), scrotal circumference (SC), and body weight (BW) at 100 (January), 150 (March), 180 (April), 240 (June), 365 (October), and 480 d (February) of age. In adult rams (n = 63 to 73 per year) BW and SC were measured in March, May (prior to breeding), August and October. Semen quality was evaluated before each breeding season, and the results of controlled reproductive performance (2 natural services to designated rams) were analyzed. Indices were applied to relate testis size to body weight: TD BW , SC BW and TW BW . Heritability estimates of testes indices in ram lambs at 100 to 240 d and at 480 d of age ranged from 0.21 to 0.36 (SE = 0.067 to 0.090). In adult rams SC measurements within months in consecutive years were repeatable (r = 0.55 to 0.68; P相似文献   

Libido and scrotal circumference of rams as affected by season of the year and altered photoperiod

Two trials were conducted to evaluate the influence of season of the year and altered photoperiod on libido and scrotal circumference (SC). A 30-minute serving-capacity test was used to measure ram libido. the measures of libido were reaction time (RT), time from entry into the pen to first mount and/or service, total mounts (M), and total services (S). The serving-capacity test was conducted by placing a ram with four estrus-induced ewes and measuring RT and counting M and S. Prior to each serving-capacity test, SC was measured for each ram. Rams were tested every two weeks. In Trial I, eleven two-year-old Rambouillet rams from each of three selection lines -a high line (four rams; selected on the basis of high prolificacy), a low line (three rams; selected on the basis of low prolificacy) and a random bred control line (four rams) - were used in a one-year study. Rams were exposed to ambient conditions throughout the year. Rams were more active during the short days of fall and winter, i.e. normal breeding season, as evidenced by a greater number of total mounts and services plus a shorter reaction time. Selection line affected reproductive parameters measured, with the high line having more M and S and a shorter RT than the low line. However, SC was larger in the low line. In Trial II twelve rams were divided into two groups of six. The control group was exposed to ambient conditions from April 18 through July 24. The treated group was exposed to eight hours of light and 16 hours of darkness (8L:16D) from April 18 through July 24, simulating short days of fall and winter. Total services (S) in the 30-minute test interval were higher for rams subjected to the 8L:16D treatment (P<0.01; 2.7+/-0.2 vs 1.6+/-0.2 for 8L:16D and control, respectively). SC was 31.7+/-0.2 vs 30.2+/-0.2 for 8L:16D and control, respectively (P<0.01). Total mounts in 30 minutes were not affected by treatment (6.9+/-0.8 vs 5.7+/-0.8 for 8L:16D and control, respectively; P>0.10). No significant differences in any of the reproductive parameters between treatment groups were observed during the first 28 days. However, there were significant differences (P<0.05) observed between 8L:16D rams and control rams for SC during 42 to 84 days and S between days 42 to 70, respectively. Serving-capacity tests carried out about one month following the end of altered photoperiod trial showed no significant differences between treated and control rams, thus indicating that treatment had no carry-over effect.     

Semen characteristics, mating performance and serum testosterone in rams fed sewage solids

Two months before beginning an autumn breeding season, ten 18-month-old Debouillet rams were randomly allotted to one of two dietary treatments. Five rams were offered a complete pelleted diet containing 3.5% cottonseed meal (CSM) and five were fed a similar diet containing 7% undigested, irradiated (1 Mrad gamma-irradiation) sewage solids (SS, Las Cruces, NM, municipal sewage) during the ensuing nine-month period. Ram body weights did not differ (P>0.10) between treatments nor was grease fleece weight (six-month clip) influenced by dietary SS. Analysis of serum constituents did not reveal any treatment effects. Neither quantity nor quality of sperm was influenced by treatment. Rams were mated to both CMS- and SS-fed ewes and dietary SS did not adversely influence (P>0.25) ram or ewe reproductive performance. Paternal sewage consumption did not alter (P>0.10) preweaning performance of lambs; however, ewes consuming SS produced lambs that weighed less (P<0.05) at weaning. Neither paternal nor maternal treatments influenced (P>0.10) lamb weights or gains during an 84-day postweaning feedlot trial. When each ram was challenged with 50 mug gonadotropin releasing hormone, both groups responded with a similar testosterone surge. These data suggest that a diet containing 7% SS does not impair reproductive function, testosterone production, offspring performance or health of fine-wool rams.     

In vivo fertility of rams in relation to sperm-zona pellucida binding and sperm-zona pellucida penetration of ovine oocytes

Sperm-zona pellucida (zona) binding and sperm-zona penetration have been suggested for use as in vitro bioassays of fertility since both are essential steps in the fertilization process. The correlations of sperm-zona binding and sperm-zona penetration with the in vivo fertility of sheep were investigated in this study. In vivo fertility was estimated from a heterospermic insemination trial using cryopreserved ram semen. Neither zona binding, zona penetration nor the ability to undergo an acrosome reaction was significantly correlated with the in vivo fertility of the rams (P = 0.78, P = 0.66, and P = 0.85, respectively). These results suggest that the zona binding and zona penetration bioassays may not be useful estimators for assessing cryopreserved ram sperm fertility.     

Relationships between Brucella ovis semen culture and various semen and serology parameters

Semen and blood samples from 154 rams from two Montana range flocks (Flock A, vaccinated for Brucella ovis ; Flock B, nonvaccinated) were evaluated to determine the relationship between Brucella ovis (B. ovis ) semen culture results and various semen and blood parameters. All rams utilized in this study exhibited no palpable ram epididymitis lesions. Thirteen and 25.6% of the rams tested in Flocks A and B, respectively, had positive B. ovis semen cultures. Only age of ram and ram condition scores differed (P<0.05) between flocks. No flock by semen culture interactions were detected (P>0.05) for any of the parameters evaluated. Age of ram, ram condition score, and spermatozoa rate from forward movement were unrelated (P>0.05) to B. ovis culture results. Rams with positive B. ovis semen cultures had lower sperm motility (P<0.05), higher percentage of abnormal spermatozoa cells (P<0.05), higher percentage of spermatozoa head abnormalities (P<0.01), lower percentage of live-normal cells (P<0.05), higher incidence of white blood cells in semen (P<0.01) and higher complement fixation (CF) titers (P<0.01).     

An acrosin inhibitor in ram spermatozoa that does not originate from the seminal plasma.

Ram seminal plasma, and ejaculated ram spermatozoa that have been washed with 0.25M sucrose, both contain acrosin inhibitor. The aim of this work was to determine whether the intracellular inhibitor originates from the seminal plasma. The amounts of inhibitor in ejaculated and epididymal spermatozoa were measured and compared with the amounts present in the seminal plasma of normal and vasectomized rams. One ejaculated ram spermatozoon contained 2.1 amol (2.1 X 10(-18) mol) of inhibitor and one epididymal spermatozoon contained 3.3 amol of inhibitor. (All molarities are mean values based on pooled ram semen or on single ejaculates from three vasectomized rams.) Calculations from results in earlier publications indicated that one ejaculated ram spermatozoon contains about 3 amol of acrosin; thus the inhibitor: acrosin ratio in washed ram spermatozoa is approximately 1. One ml of ram semen contains, on average, 3 X 10(9) spermatozoa and not more than 0.8 ml of seminal plasma. This number of ejaculated spermatozoa would contain 6.3 nmol of inhibitor, while the same number of epididymal spermatozoa would contain 9.9 nmol of inhibitor. These values exceed the quantities of inhibitor present in 0.8 ml of normal seminal plasma (approximately 1.6 nmol) or in 0.8 ml of seminal plasma from vasectomized rams (approximately 2.3 nmol). We conclude that seminal plasma is not a major source of the acrosin inhibitor that can be recovered from washed ejaculated ram spermatozoa.     

Serum luteinizing hormone, testosterone, and thyroxine and growth responses of ram lambs fed locoweed (Oxytropis sericea) and treated with vitamin E/selenium

Sixteen ram lambs (5 m.o. old, 45 +/- 1.5 kg) received a control diet (50% concentrate, no locoweed, n = 4), locoweed (20% locoweed for 21 d, n = 4), MUSE (2 mL i.m. of MUSE containing 5 mg selenium and 50 mg vitamin E/mL, n = 4) on Days 21 and 35([Day 0 = first day of trial]), or locoweed + MUSE (n = 4). The rams were maintained in individual pens (3 x 9 m) with free access to feed, water, salt and shade. On Day 7 after initiating locoweed, serum alkaline phosphatase (AP) increased (P < 0.01), and serum thyroxine (T4) decreased (P < 0.01) in locoweed-fed rams. Effects on serum AP and T4 remained constant in rams during the 21 d of locoweed feeding. Treatment with MUSE did not influence (P > 0.10) AP or T4. Locoweed-fed rams had reduced (P < 0.05) intake and body weight for the 2-wk period after locoweed feeding ended. The MUSE regimen or diet had no effect on intake or body weight (P > 0.50). Neither locoweed nor MUSE affected serum LH before or after GnRH administration on Day 22 (P > 0.10). On Day 50, however, area under the LH curve (AUC) was 966 units in locoweed-fed rams and 1,373 units (+/- 154) in controls (P = 0.09). Serum testosterone (T) was reduced in locoweed-fed rams before and after (P < 0.05) GnRH on Day 22. On Day 50, the T AUC was numerically lower (P = 0.14) in locoweed-fed rams (1,252 units) than in controls (1,539 +/- 130 units). Conversely, MUSE treatment resulted in increased (P = 0.02) T AUC on Day 50 (1,148 and 1,643 +/- 130 units in control and MUSE-treated ram lambs, respectively). During the 6-wk period after locoweed feeding, serum immunoglobulin G averaged 14.0 and 18.6 (+/- 1.1) mg/mL in control and locoweed-fed rams (P < 0.01), respectively. Twenty percent dietary locoweed for 21 d exerts adverse effects on feed intake, growth, and reproduction in young ram lambs and MUSE was not effective in reversing these effects.     

Relationship between in vitro sperm functional tests and in vivo fertility of rams following cervical artificial insemination of ewes with frozen-thawed semen

Several procedures have been proposed to assess structural and functional characteristics of cryopreserved ram semen but none so far have yielded consistent relationships with in vivo fertility. The objectives of this study were to evaluate several sperm function tests as potential markers of in vivo ram fertility (determined by pregnancy rate in ewes) using frozen-thawed semen. In experiment 1, frozen-thawed straws (n=3 per ram) of semen from three high and three low fertility rams were assessed using fluorescent microscopy for (1) progressive motility, (2) viability and, (3) acrosomal status. In experiment 2, frozen-thawed straws (n=3 per ram) of semen from 18 rams of known fertility were analysed using either computer-assisted sperm analysis (CASA) for eight motion characteristics or flow cytometric staining for: (1) viability and acrosomal status, (2) plasma membrane status and capacitation-like changes, and (3) live cells following an osmotic resistance test (ORT). In experiment 3, platelet-activating factor (PAF) was isolated from straws (n=2 per ram) of semen using high-pressure liquid chromatography (HPLC) and quantified using HPLC-tandem mass spectrometry for 18 rams. In experiment 1, no association was found between motility, viability (% live) or acrosomal status (% damaged, % intact and % reacted) and in vivo fertility. In experiment 2, no correlation was found between motility (CASA), viability (% live), acrosomal status (% live, % live intact and % reacted), capacitation status (% capacitated, % non-capacitated), plasma membrane stability (% dead) and % live cells following ORT and ram in vivo fertility. In experiment 3, there was no relationship between PAF content in spermatozoa and ram fertility. In conclusion, we were unable to relate the in vivo fertility of rams with in vitro functional tests of their frozen-thawed semen and suggest that the fertility of a given semen sample cannot easily be quantified using available in vitro tests.     

Scrotal circumference measurements in purebred Dorset, Hampshire and Suffolk lamb and yearling rams

Purebred Suffolk, Hampshire and Dorset lamb and yearling rams (n=753), underwent performance testing from 1986 to 1989. Scrotal circumference, birth date and entry weight were recorded for each ram entering the test station. Mean age in days at entry, weight (lbs), and scrotal circumference (SC; cm) were greatest for the Hampshire rams. For all rams combined (Dorset, Hampshire and Suffolk), the mean SC by month of age revealed rapid growth from 2 to 6 mo, with a 3- to 6-mo mean SC significantly (P0.05) for mean SC measurement and a less rapid increase in SC diameter. Between 12 and 13 mo a significant increase (P相似文献