Genetic and non-genetic parameters of several characteristics of production and semen quality in young bucks

The objective of this study was to evaluate genetic and non-genetic factors influencing characteristics of young buck semen production using a multivariate model that takes into account the longitudinal structure of data. Data were collected from 1989 to 2002 at two French A.I. centres. The data corresponded to 13151 and 9206 ejaculates of 758 Alpine and 535 Saanen bucks respectively, collected at the beginning of the first breeding season (September-December). The semen volume, the total number of spermatozoa, the concentration, the motility score of spermatozoa after freezing and the percentage of motile spermatozoa after freezing were registered for each ejaculate. Within-breed heritabilities and repeatabilities were estimated using a multivariate animal model using a power spatial covariance structure for environmental effect. For all characteristics and the two breeds, the main source of variation was the year-month interaction that interacted with the centre. We observed a decrease in years of motility score after freezing. Age and frequency of collection had a significant effect on semen volume and number of spermatozoa for both breeds, and on concentration of spermatozoa for the Alpine breed. No effect of these factors was found on the characteristics observed after freezing. Heritabilities for concentration, number of spermatozoa, semen volume, motility score after freezing and percentage of motile spermatozoa after freezing per ejaculate were respectively, 0.32, 0.15, 0.25, 0.12 and 0.05 for the Saanen breed and 0.34, 0.25, 0.29, 0.17 and 0.03 for the Alpine breed. Genetic correlations between volume and number of spermatozoa were respectively, 0.74 for the Alpine breed and 0.86 for the Saanen breed. Further study is required to compare the semen characteristics of young bucks with their mature production.     

Egg shell quality in Japanese quail: characteristics,heritabilities and genetic and phenotypic relationships

The objective of the present study was to estimate heritabilities as well as genetic and phenotypic correlations for egg weight, specific gravity, shape index, shell ratio, egg shell strength, egg length, egg width and shell weight in Japanese quail eggs. External egg quality traits were measured on 5864 eggs of 934 female quails from a dam line selected for two generations. Within the Bayesian framework, using Gibbs Sampling algorithm, a multivariate animal model was applied to estimate heritabilities and genetic correlations for external egg quality traits. The heritability estimates for external egg quality traits were moderate to high and ranged from 0.29 to 0.81. The heritability estimates for egg and shell weight of 0.81 and 0.76 were fairly high. The genetic and phenotypic correlations between egg shell strength with specific gravity, shell ratio and shell weight ranging from 0.55 to 0.79 were relatively high. It can be concluded that it is possible to determine egg shell quality using the egg specific gravity values utilizing its high heritability and fairly high positive correlation with most of the egg shell quality traits. As a result, egg specific gravity may be the choice of selection criterion rather than other external egg traits for genetic improvement of egg shell quality in Japanese quails.     

Variability in relationships between semen quality and estimates of in vivo and in vitro fertility in boars

The present experiment was designed to characterize relationships between common semen quality and fertility estimates for three boars known to differ in farrowing rate, number of pigs born alive, and monospermic penetration rate. The approach chosen to accomplish this was to monitor semen quality from these boars and use their semen alternately for either artificial insemination or in vitro fertilization for 40 weeks. This strategy relied on the variability in semen quality parameters that normally occurs in an individual boar over time. When comparisons were made among boars, farrowing rates, numbers of pigs born alive, and monospermic penetration rates were significantly different, but progressive motility, normal head and tail morphology, and acrosome morphology were not. However, when comparisons were made among ejaculates within individual boars, there were significant effects of semen quality on both in vivo and in vitro fertility. For boar 3495, the proportion of spermatozoa exhibiting progressive motility and distribution of spermatozoa in a percoll gradient had a positive linear effect on number born alive and monospermic penetration rate, respectively. For boar 2901, quadratic equations best described changes in litter size as a function of progressive motility and normal acrosomes. In addition, monospermic penetration rate increased linearly as normal acrosomes and the proportion of spermatozoa recovered from a percoll gradient increased. For boar 4291, the relationship between progressive motility and number born alive and between normal acrosomes and number of pigs born alive were also quadratic. However, a significant linear relationship was present only between normal acrosomes and monospermic penetration rate. These results demonstrate that simply relying on the means of common semen quality estimates from some boars has limited value in terms of being used as a prospective indicator of their in vivo or in vitro fertility. In contrast, characterization of relationships between semen quality and fertility estimates is useful for estimating differences in the fertility of ejaculates from individual boars. However, both quantitative and qualitative differences in these relationships among boars are present and a given semen quality estimate that is a good predictor of in vivo or in vitro fertilization for one boar, may not be applicable for others.     

Adrenocortical responses in zebra finches (Taeniopygia guttata): individual variation, repeatability, and relationship to phenotypic quality

Although individual variation is a key requirement for natural selection, little is known about the magnitude and patterns of individual variation in endocrine systems or the functional significance of that variation. Here we describe (1) the extent and repeatability of inter-individual variation in adrenocortical responses and (2) its relationship to sex-specific phenotypic quality, such as song duration and frequency and timing of egg laying. We measured adrenocortical responses to a standardized stressor in zebra finches (Taeniopygia guttata) at two life history stages: approximately day 16 (nestlings) and 3 months of age (sexually mature adults). Subsequently, we assessed phenotypic (reproductive) quality of all individuals as adults. Marked inter-individual variation in the adrenocortical response was seen in both sexes and ages, e.g., stress-induced corticosterone ranged from 2.2 to 62.5 ng/mL in nestlings and 5.0-64.0 ng/mL in adults. We found sex differences in (a) inter-individual variation in the adrenocortical response, (b) repeatability, and (c) relationships between corticosterone levels and phenotypic quality. In males, variation in nestling corticosterone was weakly but positively correlated with brood size and negatively correlated with nestling mass (though this relationship was dependent on one individual). There was no significant correlation of adrenocortical responses between two stages in males and adult phenotypic quality was significantly correlated only with adult corticosterone levels. In contrast, in females there was no relationship between nestling corticosterone and brood size or mass but adrenocortical response was repeatable between two stages (r2=0.413). Phenotypic quality of adult females was correlated with nestling baseline and adrenocortical response.     

Variability,repeatability, character correlation and path coefficient analyses in yellow yam

Summary Phenotypic variances, genetic coefficients of variation, repeatability, expected genetic advance, correlation coefficients and path coefficients were estimated for seven agronomic traits in yellow yam. Plant leafiness, leaf virus infection, number of tubers per hill and tuber yield showed higher expected genetic advances associated with higher repeatability. Positive and highly significant correlations of tuber yield with plant leafiness, shoot height and vine dry weight were observed. Correlations of time to vine emergence and leaf virus infection with yield were negative. Path analysis showed that leaf virus infection had a large negative direct as well as indirect effect on yield. Based on these studies, it is suggested that resistance to leaf virus infection, as expressed by foliage vigour, is the chief criterion for selecting high yielding plant types in yellow yam.     

Relationships between rabbit semen characteristics and fertilising ability after insemination

This study aimed to analyse the relationship between rabbit semen characteristics and semen fertilising ability after insemination, which is generally found to be weak. Our hypothesis was that using high semen dilutions (1 : 19), non-oestrus-stimulated does, and homospermic inseminations would make it easier to predict semen fertilising ability. Semen characteristics were evaluated on 275 ejaculates of 128 INRA1001 bucks, distributed into five successive batches. A total of 1970 inseminations were performed. The continuous semen variables were subdivided into three classes of similar size to account for any non-linear relationship between semen characteristics and fertilising ability. Mass motility was divided into two classes according to the presence or absence of waves under microscope observation. Libido, the presence or absence of gel, volume, percentage of progressive sperms, curvilinear velocity, beat frequency of the flagellum, and straightness and linearity of sperm movement did not affect fertility, prolificacy or productivity. It was confirmed that mass motility, estimated by visual observation under the microscope, significantly influenced fertility as well as the percentage of motile and of rapid sperms, and the amplitude of lateral head displacement, estimated by a computer-assisted semen analysis system. To a lesser extent, the percentage of motile cells and of rapid cells significantly influenced prolificacy. Consequently, mass motility and the percentage of motile cells significantly influenced rabbit doe productivity (+1 live births/AI when the semen showed at least a beginning of wave movement, or when the percentage of motile cells was >84%). Interestingly, a gain of 1.5 rabbits was observed when the percentage of rapid cells changed from 64% to 79%, whereas productivity significantly dropped beyond 83% of rapid cells, reflecting a non-linear relationship.     

Effects of age and environmental factors on semen production and semen quality of Austrian Simmental bulls

More than 90% of the breeding stock of Austrian dual purpose Simmental cows is artificially inseminated. Knowledge of factors affecting sperm production and semen quality is of importance with regard to reproductive efficiency and thus genetic improvement as well as for the productivity and profitability of AI centers. Hence, semen data from two Austrian AI centres collected in the years 2000 and 2001 were evaluated. In total, 3625 and 3654 ejaculates from 147 and 127 AI bulls, respectively, were analysed regarding ejaculate volume, sperm concentration, percentage of viable spermatozoa in the ejaculate, total spermatozoa per ejaculate and motility. Effects accounted for were the bull (random), age of bull, collection interval, number of collection on collection day, bull handler, semen collector, temperature on day of semen collection, in the course of epididymal maturation (average temperature of days 1-11 before collection) and during spermatogenesis (average temperature of days 12-65 before collection). Age of bull significantly affected all traits (P<0.01 to P<0.001) except motility score in center 2. Ejaculate volume and total number of spermatozoa increased with age of bull while sperm concentration was lower in higher age classes (center 1). The collection team was also found to significantly influence semen quality traits. With increasing collection interval ejaculate volume and total number of spermatozoa increased significantly (P<0.05 to P<0.001) while collection intervals between 4-9 days and 1-6 days were superior with regard to sperm concentration and percentage of viable spermatozoa, respectively (P<0.10 to P<0.001). First ejaculates were superior with respect to ejaculate volumes, sperm concentrations and total number of spermatozoa per ejaculate (P<0.001). Temperature, either on day of semen collection or during epididymal maturation or spermatogenesis, had important but inconsistent effects on semen production and sperm quality. Overall, however, ambient temperatures in the range of 5-15 degrees C were found to be optimal for semen production.     

The relationship between rabbit semen characteristics and reproductive performance after artificial insemination

The relationships between several rabbit buck semen traits, concerning either the ejaculate or the dose inseminated (volume, mass motility, pH, percentage of motile sperm (PMS), concentration, number of total and motile sperm per ejaculate and per insemination dose) and the reproductive performance of does was investigated in 839 inseminations involving 54 bucks and 111 does. Four genetic types were involved: INRA1601 strain (A), INRA2066 strain (B) and the two reciprocal crossbreds (AB and BA). The mating design was A x A, B x B, (AB or BA) x (AB or BA). Semen was diluted (1:9) and a constant volume of 0.5 ml was inseminated 2-4h after collection. Therefore, the total number of spermatozoa per dose was variable and proportional to the initial concentration. Mass motility significantly influenced the kindling rate. Taken separately, volume, PMS and concentration did not influence the kindling rate but their product, the number of motile sperm per ejaculate, did. Litter size (total born) was significantly influenced by concentration and all variables depending on it, particularly the number of total and motile sperm per dose. However, reproductive performances were predominantly influenced by the physiological status of the does at insemination (lactation stage and receptivity).     

Sponge and dough bread making: genetic and phenotypic relationships with wheat quality traits

The genetic and phenotypic relationships among wheat quality predictors and sponge and dough bread making were evaluated in a population derived from a cross between an Australian cultivar ‘Chara’ and a Canadian cultivar ‘Glenlea’. The genetic correlation across sites for sponge and dough loaf volume was high; however, phenotypic correlations across sites for loaf volume were relatively low compared with rheological tests. The large difference between sites was most likely due to temperature differences during grain development reflected in a decrease in the percentage of unextractable polymeric protein and mixing time. Predictive tests (mixograph, extensograph, protein content and composition, micro-zeleny and flour viscosity) showed inconsistent and generally poor correlations with end-product performance (baking volume and slice area) at both sites, with no single parameter being effective as a predictor of end-product performance. The difference in the relationships between genetic and phenotypic correlations highlights the requirement to develop alternative methods of selection for breeders and bakers in order to maximise both genetic gain and predictive assessment of grain quality.     

Effect of age and genetic group on characteristics of the scrotum,testes and testicular vascular cones,and on sperm production and semen quality in AI bulls in Brazil

The objectives were to determine the effects of age and genetic group on characteristics of the scrotum, testes and testicular vascular cones (TVC), and on sperm production and semen quality in 107 Bos indicus, B. taurus and cross-bred bulls at three artificial insemination (AI) centers in Brazil. In addition, predictors of sperm production and semen quality were identified. In general, scrotal circumference (SC), scrotal shape score, scrotal neck perimeter, and testicular size (length, width and volume) increased (P < 0.05) with age. Although there were no significant differences among genetic groups for SC or testicular size, B. indicus bulls had the least pendulous scrotal shape, the shortest scrotal neck length, and the greatest scrotal neck perimeter (P < 0.05). Fat covering the TVC was thinner (P < 0.05) in bulls < or = 36 months of age and in B. taurus bulls than in older bulls and B. indicus bulls, respectively. Age and genetic group did not affect testicular ultrasonic echotexture. B. indicus bulls tended (P < 0.1) to have the lowest average scrotal surface temperature (SST). In general, ejaculate volume, total number of spermatozoa and number of viable spermatozoa increased (P < 0.05) with age. However, there was no significant effect of age on sperm concentration, motility, major and total defects. The proportion of spermatozoa with minor defects was highest (P < 0.05) in bulls 37-60 months of age. B. indicus bulls had higher (P < 0.01) sperm concentration, total number of spermatozoa and number of viable spermatozoa than B. taurus bulls, with intermediate values for cross-bred bulls. Increased sperm production was associated with increased testicular volume, SC, TVC fat cover, and SST top-to-bottom gradient. Decreased semen quality was associated with increased SC and bottom SST, and decreased scrotal shape, scrotal neck perimeter and vascular cone diameter. In summary, age and genetic group affected the characteristics of the scrotum, testes, and TVC, sperm production and semen quality. In addition, characteristics of the scrotum, testes and TVC were associated with sperm production and semen quality in bulls and could be assessed for breeding soundness evaluation.     

Estimation of genetic parameters for semen quality traits and growth rate in a paternal rabbit line

Variance components of sperm quality traits were estimated in a paternal line of rabbits selected on the basis of daily weight gain (DG, g/day) between 28 and 63 days of age. Features of the marginal posterior distributions for the genetic variance ratios, variance due to non-additive plus environmental permanent male effects, and variance due to litter of birth effects with respect to phenotypic variance are reported. The correlation between sperm quality traits and the selection criteria were also estimated. Nine sets of two-trait analyses were performed involving 12 908 DG records, 2231 ejaculates corresponding to 412 males, and 14 700 animals in the pedigree file. Heritability values (h²) of sperm quality traits commonly evaluated in a classic spermiogram were 0.18, 0.19, and 0.12 for normal acrosome status (NAR) (%, percentage of sperm with intact acrosome), sperm abnormalities (ANR) (%, percentage of sperm abnormalities), and sperm motility (MOT) (%, percentage of total motile sperm cells), respectively. The h² of some motion computer-assisted sperm analysis (CASA) Parameters 0.09, 0.11, 0.10, 0.11, 0.11 and 0.11 for average path velocity (VAP) (μm/sec; average path velocity), straight-line velocity (VSL) (μm/sec; straight-line velocity), curvilinear velocity (VCL) (μm/sec; curvilinear velocity), linearity index (LIN) (%, linearity index), amplitude of lateral head displacement (ALH) (μm; amplitude of the lateral head displacement) and straightness (STR) (%, straightness) were also estimated. Permanent environmental effects were lower than the corresponding values of h² and varied between 0.04 and 0.14. Genetic correlations between DG and sperm traits showed a high interval of highest density of 95% (HPD)_95% (interval of highest density of 95%). However, there is some consistent evidence of the negativity of the genetic correlations of DG with NAR and MOT (−0.40 and −0.53, respectively). Permanent correlations were low, including the zero in the HPD_95%. Litter birth correlations between DG with LIN and STR showed that a favorable effect for growth could be detrimental for them (−0.47 and −0.53). Therefore, as the magnitude of the genetic correlations does not seem very high, it may be possible to define a selection index, including some sperm quality traits that allow improvement of DG without diminishing the semen quality.     

Age-dependent changes in sperm production, semen quality, and testicular volume in the black-footed ferret (Mustela nigripes)

The black-footed ferret (Mustela nigripes), which was extirpated from its native North American prairie habitat during the 1980s, is being reintroduced to the wild because of a successful captive-breeding program. To enhance propagation, the reproductive biology of this endangered species is being studied intensively. The typical life span of the black-footed ferret is approximately 7 yr. Female fecundity declines after 3 yr of age, but the influence of age on male reproduction is unknown. In this study, testis volume, seminal traits, sperm morphology, and serum testosterone were compared in 116 males from 1 to 7 yr of age living in captivity. Results demonstrated that testes volume during the peak breeding season was similar (P > 0.05) among males 1 to 5 yr of age, reduced (P < 0.05) among males 6 yr of age, and further reduced (P < 0.05) among males 7 yr of age. Motile sperm/ejaculate was similar in males 1 to 6 yr of age but diminished (P < 0.05) in those 7 yr of age. Males at 6 and 7 yr of age produced fewer (P < 0.05) structurally normal sperm than younger counterparts; however, serum testosterone concentrations were not reduced (P > 0.05) in older males. Histological comparison of testicular/epididymal tissue from 5- and 7-yr-old black-footed ferrets confirmed that the interval between these two ages may represent a transitional period to reproductive senescence. In summary, functional reproductive capacity of male black-footed ferrets exceeds that of females by at least 2 yr. Testes and seminal quality are indistinguishable among males 1 to 5 yr of age, with progressive reproductive aging occurring thereafter.     

Effects of dietary gossypol on aspects of semen quality, sperm morphology and sperm production in young Brahman bulls

Eight young reproductively normal Brahman bulls (average age and bodyweight 20 months and 500 kg, respectively) received either cottonseed meal delivering 8.2 g free gossypol/bull/d (treatment group, n=4) or soybean meal (control group, n=4) for 12 wk. After adjustment (1 wk), weekly procedures (11 wk) included blood collection, scrotal circumference measurement and electroejaculation. Semen assessments included sperm motility, percentage of live spermatozoa, general sperm morphology (using brightfield microscopy), and midpiece morphology (using DIC microscopy). After sacrifice (Week 12), sperm production rates (daily and per gram testicular parenchyma) were determined. Treated bulls did not differ from controls in scrotal circumference or the percentage of live spermatozoa. Sperm motility differed at Weeks 9 (P<0.05), 10 and 11 (both P=0.06). Treated bulls had fewer normal spermatozoa at Weeks 5 (P<0.05), 6 (P<0.01) and 7 thru 11 (P<0.001). Beginning from Week 3, treated bulls showed an increased proportion of sperm midpiece abnormalities (P<0.05) which stabilized at 52 to 62.5% between Weeks 5 and 11 (P<0.01 or P<0.001). Treated bulls also had lower sperm production than untreated bulls, both on a daily (P<0.01) and per gram testicular parenchyma (P<0.001) basis. A cottonseed supplement providing 8.2 g of free gossypol per bull per day had adverse effects upon both sperm morphology and spermatogenesis in young Brahman bulls, with the former being first evident within 3 to 4 weeks of feeding of cottonseed meal.     

Effects of oocyte quality, semen donor and embryo co-culture system on the efficiency of blastocyst production in goats

The aim of the study was to determine whether the selection of immature oocytes by a combination of cumulus-oocyte-complexes (COCs) morphology and staining with brilliant cresyl blue (BCB) would be helpful in selecting developmentally competent oocytes, and thereby increase the efficiency of blastocyst production from ovarian oocytes of FSH-primed, adult goats. In a second experiment the interaction between oocyte quality and semen donor was assessed. In a third experiment the usefulness of Vero cells for co-culture with goat embryos was investigated. In the pool of morphologically normal COCs recovered from ovaries following slicing (21.9+/-11.0), the mean rate of COCs classified as BCB+ was 85.6%, and the BCB- was approximately 11%. Oocytes classified as grade 1 and BCB+ exhibited the highest developmental competence (P<0.001) after in vitro maturation and fertilization compared with oocytes of grade 1 BCB- and grade 2 BCB+ or BCB-. There were no significant differences in developmental competence in grade 2 oocytes, regardless of BCB coloration. No significant differences in embryo cleavage and blastocyst formation rates among three bucks were observed when morphologically normal, BCB+ oocytes were used. For all tested bucks, differences in embryo production efficiency were related only to the oocyte quality. Similar blastocyst rates were developed from embryos co-cultured with goat oviduct epithelial cells (34.3%) and with Vero cells (33.3%). These results show that the most important criterion for selection of COCs before maturation is the visual assessment of morphological features. Staining with BCB of COCs recovered from adult goats does not enhance efficiency of selection of developmentally competent oocytes for IVF.     

Body weight, semen quality, and age at sperm production of hemicastrated and intact cockerels (Gallus domesticus)

Spermatozoa were found earlier in the ejaculates of hemicastrated cockerels and the mean body weight of the hemicastrates was significantly (P less than 0.01) greater than that of the intact cockerels. The mean values for sperm concentration/ml, and total spermatozoa in the ejaculates of the hemicastrates were significantly greater (P less than 0.01) than those of the intact cockerels. Differences existed between the hemicastrates bearing the left testis, and those bearing the right testis in respect of age at sperm production, sperm/concentration and total spermatozoa in the ejaculate.