Genetic and non-genetic factors related to the success of artificial insemination in dairy goats.

The objective of this study was to evaluate genetic and non-genetic factors influencing artificial insemination (AI) success in French dairy goats. Data analysis, on a total of 584 676 and 386 517 AI records for Alpine and Saanen breed, respectively, collected from 1992 to 2009, was conducted separately on each breed. We used a linear simple repeatability animal model which combined male and female random effect and environmental fixed effects. The most important environmental factor identified was the period within year effect due to the European heat wave of 2003. The estimated values of the annual fertility exhibited a negative trend of 1% loss of AI success per 10 years for Alpine breed only. The range of variation for the flock×within years random effect was 70% and 65% for Alpine and Saanen breeds. The negative effect on AI success of antibody production after repetitive hormonal treatment was confirmed. We observed an important positive relationship between fertility and protein yield expressed as quartile within flock×years of protein 250-day yield for female with lactation number over 1, while this trend was negative for primiparous females. We detected a negative effect of the duration of conservation of semen with a difference of about 4% of AI success between extreme values (2 to 8+ or 9+ years). Heritability estimates for male fertility were 0.0037 and 0.0043 for Alpine and Saanen breed respectively, while estimates for female fertility was 0.040 and 0.049. Repeatability estimates for males were 0.008 and 0.010 for Alpine and Saanen, respectively, and 0.097 and 0.102 for females. With such low values of heritability, selection can hardly affect fertility.

Genetic and non-genetic parameters related to embryo production in superovulated Large White (LW) gilts.

The aim of this study was to identify genetic and non genetic factors which might affect results of embryo production of Large White (LW) cyclic gilts from data collected in one herd during 6 years. Donors (n=1060) were synchronized with a progestogen treatment and luteolysis was induced 13-15 days later by 2 injections of cloprostenol. To stimulate follicular development 800IU eCG was then injected 24h later, followed by 500IU hCG 48h later. Donors were inseminated twice; depending on the onset of oestrus, the interval between hCG treatment and first insemination (hCGAI1) was either 24 or 41 h. Embryos were collected at 5-6 days after the 1st AI by flushing uterine horns. Traits of interest were the number of corpora lutea (CL), the number of flushed embryos (FE), the number of transferable embryos (TE) and the number of unfertilized embryos (UE). The average number of TE was 18.8 ± 9.0. The main sources of variation for CL, FE and TE were the season (P≤0.002) and hCGAI1 (P≤0.001) effects. For the interval of 24h of hCGIA1 the number of TE was increased by 4 compared with the TE obtained for the 41 h interval of hCGIA1. Maternal and paternal genetic effects were estimated using restricted maximum likelihood methodology applied to the univariate animal model, whereas genetic covariance components were estimated in bivariate models. Estimates of maternal heritability were 0.45 for CL, 0.32 for FE, 0.29 for TE and 0.05 for UE whereas for the paternal effect, heritabilities were very low (<0.06). Genetic correlation between CL, FE and TE variables were very high (>0.89) for the maternal effect. A breeding scheme based on CL selection in response to superovulation could thus improve the number of transferable embryos.

Selection of impubertal gilts by ultrasonography optimizes their oestrus, ovulatory and fertility responses following puberty induction by PG600.

In a group of gilts, occurrence of puberty is spread over several weeks. The optimal time to apply puberty induction is therefore difficult to define, as treatment of puberal gilts is meaningless. Changes in uterine aspect around puberty can be detected by ultrasonography. Two experiments were carried out to assess the effect of PG600(®) (400 UI of eCG and 200 UI hCG) administration to 6 months old gilts shown to be impubertal by ultrasonography on cyclicity and reproductive performance. Impubertal Large White gilts (n=94) were treated with either PG600 or solvent (controls). Administration of PG600 to impubertal gilts increased significantly the proportion of females displaying pubertal uterine ultrasound images 3 days after treatment (100% versus 65% in controls). The number of days to puberty was significantly reduced in gilts injected with PG600 (3.3 days) versus controls (4.7 days). In gilts of the PG600 group, ovulation rate was higher at the 1st oestrus compared to the 2nd, while this did not happen in controls. Progesterone concentrations were higher at mid-luteal phase in the PG600 treated gilts compared to controls (significant treatment by time interaction). Similar proportions of gilts returned to oestrus (89% versus 74% for controls). Following insemination at the 2nd oestrus, pregnancy rate and number of live embryos were unaffected by treatment. The combination of ultrasonography and PG600 optimizes the use of exogenous hormones by targeting treatment to gilts that need it, therefore facilitating the introduction of gilts into all in/all out system.

The value of the percentage of motile sperm in predicting a significant portion of the fertility variation of frozen-thawed buck semen.

Prediction of the future fertility of a given ejaculate with a simple laboratory test is still considered a real issue in domestic mammal breeding. This study showed that a subjective assessment of the percentage of motile spermatozoa, measured 120 min after thawing (mob120), can predict a significant part (∼50%) of the variation of the future fertility of buck ejaculates. The predictive model was calculated using a calibration data set composed of 40 ejaculates from four Alpine and six Saanen bucks. A fertility trial using split ejaculates was conducted in order to estimate ejaculate fertility. Taken into account were the herd within breed factor and the year, month, and inseminator factors. On average, one ejaculate was used to inseminate two females per herd in 10 different herds. This calibration set allowed us to choose the mob120 variable among a set of laboratory tests: mitochondrial activity, acrosomal status, membrane integrity, osmotic resistance test assessed by flow cytometry, velocity and motion characteristics assessed by computer-assisted sperm analysis, visually assessed percentage of motile, and motility score measured 5 and 120 min after thawing. For the calibration step, the best model used the logarithm of mob120 and gave a correlation coefficient of 0.71 between the field fertility and the predicted fertility and a standard error of 0.17. We tested this model on 3 different validation data sets adding up to 95 ejaculates that were all different from those of the calibration data set. The correlation coefficients between field fertility and predicted fertility were always significant and the bias corrected standard error ranged from 0.15 to 0.18 on these validation data sets. A Monte Carlo simulation showed that about 20% of the fertility variation remained to be explained.

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.

Short-duration insemination with frozen semen increases fertility rate in nulliparous dairy goats.

Standard artificial insemination (AI) using a speculum in dairy goats does not result in acceptable fertility rates in nulliparous does. An explanation might be the difficulties to pass the cervical canal in nulliparous females with the insemination gun, increasing the time needed for semen deposition. Nulliparous Alpine dairy goats were used to evaluate whether time interval from insertion to withdrawal of the speculum is a factor influencing pregnancy rates to first AI with frozenthawed semen. Oestrus was synchronized using fluorogestone acetate intravaginal sponges (FGA, 40 mg) for 11 days, associated with 50 mg i.m. of cloprostenol and 250 IU i.m. eCG 48 ± 2 h before sponge removal. In the first experiment (n = 52; 3 herds), the average duration of the AI procedure was 42 ± 10 s, with a median of 39 s. AI performed in less than 39 s resulted in higher pregnancy rates (75%, n = 28) than AI lasting for more than 39 s (46%, n = 24). In the second experiment, does (n = 325; 5 herds) were randomly assigned into two treatment groups according to a short (20 s) or long (60 s) AI procedure. We showed that the duration of AI affected fertility after a first insemination, and that pregnancy rate was significantly improved using a short-duration AI (61.2%; n = 169) compared with a long-duration AI (44.2%; n = 156). We have previously shown in the ewe that genital stimulation during AI enhanced uterine motility. Other authors reported a negative correlation between increased uterine motility at the time of AI and fertility rates in small ruminants. The results of this study suggest that rapid semen deposition may limit the reflex activation of uterine contractions provoked by the speculum and the movement of the insemination gun, and thus ameliorates reproductive performance to first AI in nulliparous goats.

Development of OPS vitrified pig blastocysts: effects of size of the collected blastocysts, cryoprotectant concentration used for vitrification and number of blastocysts transferred.

Unhatched blastocysts from Large White hyperprolific gilts (n=103) were identified, measured and vitrified using the Open Pulled Straw (OPS) technique to evaluate the effects of the collected blastocyst size and cryoprotectant concentrations used for vitrification, and the number of embryos transferred per recipient. Vitrified/warmed blastocyst viability was estimated in vitro, as the percentage of embryos developing after 72h, and in vivo, on pregnancy Day 30. In the in vitro study, we compared the use of three cryoprotectant concentrations (16.5, 18, or 20% DMSO+16.5, 18, or 20% EG+0.4M sucrose). Survival rates differed significantly between the control (98.3%) and the three cryoprotectant concentrations (67, 62.3, and 57%, respectively). Blastocyst size at vitrification determined the further in vitro development of embryos (26% survival for blastocysts 126-144microm versus 100% for blastocysts >199microm). For the in vivo study, blastocysts were vitrified using cryoprotectant concentrations of 16.5 or 18% DMSO+EG and transferred surgically in groups of 20 or 30 per recipient (n=40). Recipients were slaughtered on pregnancy D30. No significant differences were detected in gestation rates (50-70%) and embryo survival rates (14.7-25%), although survival was higher (P=0.0003) when 20 blastocysts were transferred compared to 30 (24.7% versus 15.5%). Our findings indicate that best results, in terms of subsequent in vivo embryo survival, were achieved after transferring 20 embryos at the blastocyst or expanded blastocyst stage, previously vitrified using cryoprotectant concentrations of 16.5 or 18%.

Response of goat sperm to hypoosmotic steps modelled probit analysis.

Hypoosmotic swelling test (HOS) has been proposed by many authors to evaluate the functional integrity of the sperm membrane. Our approach in this experiment has consisted in exposing spermatozoa to a wide range of osmotic pressures then evaluating the reacted sperm cells by flow cytometry and finally modelling the sperm cell responses. Semen samples were diluted in skim milk or NPPC (native phosphocaseinate) extenders, and stored at 4 degrees C for 3 days. At D0 and D3 aliquots from each ejaculate (n=12) were submitted to seven hypoosmotic solutions varying from 230 to 10mOsm/kg. Sperm samples were analyzed using flow cytometry to determine two populations of spermatozoa identified by propidium iodide (PI): PI+ (including PI, red fluorescence) and PI- (excluding PI, no fluorescence). Spermatozoa PI+ were considered as spermatozoa with membrane damages. PI+ exhibited a high variation from 230 to 10mOsm/kg which was considered as a dose-response curve. Data were modelled using Mixed procedure and probit analysis to a sigmoid curve. Each model curve characterized the profile of response of the variable PI+ to the range of osmotic pressure from 230 to 10mOsm/kg. The estimated parameters modelling the sigmoid curves are discussed in order to evaluate the effect of extender (skim milk versus NPPC) and duration of preservation (D0 versus D3). Such modelling could help to differentiate storage method ejaculates within males or between male, contributing therefore to improve semen technology.