The initial fertilizing capacity of longerm-stored liquid boar semen following pre- and postovulatory insemination

Reproductive performance of single fixed-time inseminated sows with semen doses submitted to different semen storage times

This study aimed to evaluate the reproductive performance of sows submitted to single fixed-time insemination (SFTAI) using boars according to capacity for liquid in vitro semen preservation, type of extender, and storage time. Boars (n = 12) were classified into two groups based on progressive motility (PM) at 120 h of semen storage: low (PM - 64.5%) - and high-preservation (PM - 83.9%) capacity for semen storage. Weaned sows (n = 397, parity - 1 to 7) were inseminated (1.5×10⁹ sperm cells) in a factorial design: two classes of boars (low- or high-preservation), two types of extenders (short- or long-term), and two semen storage times at insemination (24 or 72 h). An adapted triptorelin acetate protocol was used for SFTAI. Total sperm motility (TM) and PM at insemination were greater in high-preservation boars at 72 h compared with low-preservation boars at 24 or 72 h (P < 0.01). Short- or long-term extender did not affect (P ≥ 0.68) TM and PM in high-preservation boars; however, long-term extender improved these parameters in low-preservation boars (P < 0.01). Pregnancy and farrowing rates were not affected by groups (P > 0.05). Total piglets born (TPB) was reduced (P = 0.05) in low-preservation boars with 72 h of storage (13.6 ± 0.5) compared to high-preservation boars with semen stored for 24 or 72 h (15.2 ± 0.5 and 15.5 ± 0.5, respectively). The low-preservation boars reduced the TPB in sows submitted to SFTAI, and this reduction was greater using semen stored for 72 h.

Does a single fixed-time insemination in weaned sows affect gestation and lactation length, and piglet performance during lactation compared with multiple insemination protocols in a commercial production setting?

This study evaluated the effect of different single fixed-time artificial insemination (FTAI) protocols on gestation length, farrowing distribution (synchrony), and piglet performance. In Study 1, 866 sows were assigned to two groups: Multiple AI (n = 484) - multiple artificial insemination (AI) at 24 h intervals during estrus; and FTAI+MultAI (n = 382) - OvuGel® 96 h post-weaning and single FTAI 22-24 h later. In Study 2, FTAI protocols were retrospectively analyzed: pLH - sows received 2.5 mg (Exp.1, n = 184) or 5 mg (Exp.2, n = 362) of porcine luteinizing hormone (pLH) at estrus onset, and single FTAI 24 h later. The FTAI+MultAI resulted in shorter gestation length (P < 0.01) and greater synchrony of farrowing on days 114-115 of gestation (P < 0.01) than Multiple AI. Longer lactation length (21.2 vs. 20.9 d; P = 0.02) and greater piglet weaning weight (5378.9 ± 73.1 vs. 5153.2 ± 74.4 g; P = 0.03) for FTAI+MultAI compared to Multiple AI were observed. In Study 2, the gestation length based on the first AI record was shorter for FTAI and resulted in greater synchrony of farrowing on days 114-115 of gestation, compared with Multiple AI (P ≤ 0.05). Gestation length did not differ between groups (P > 0.05) when measured based on most probable AI responsible for fertilization (ultrasound evaluation). In conclusion, FTAI resulted in shorter gestation length and greater farrowing synchrony compared with Multiple AI. Longer lactation length and greater piglet weaning weight were observed for FTAI compared with multiple insemination protocols.

Reproductive performance of sows inseminated with semen doses stored for up to seven days in long-term extender in a field condition

This study aimed to evaluate the reproductive performance of sows inseminated with semen doses preserved at 15-18 °C for up to seven days in long-term extender (Duragen^®). Parity one (PO1) to PO7 sows were randomly assigned to the following groups: AI1-3 (n=190), insemination with semen doses stored between one and three days; and AI5-7 (n=124), insemination with semen doses stored between five and seven days. Sows were submitted to estrus detection twice a day. Post-cervical insemination according to weaning-to-estrus interval was performed. The farrowing rate (FR) did not differ between the groups (AI1-3=83.2%; AI5-7=82.2%; p>0.05) nor did the total number of piglets born (TPB; AI1-3=14.2±0.3; AI5-7=14.5±0.3; p>0.05). Considering the semen dose most likely responsible for fertilization according to its storage time (1, 2-3, 5, and 6-7 days), the FR (72.7%, 87.8%, 85.7%, and 79%, respectively) and TPB (14.4, 14.0, 14.9, and 13.5, respectively) were similar among the groups (p>0.05). In conclusion, the use of semen doses extended with long-term extender stored for up to seven days did not impair the reproductive performance of sows. Therefore, it’s using could optimize production efficiency and logistics of semen dose deliveries to sow farms.

In vitro aging of boar spermatozoa: role of sperm proximity and seminal plasma

BACKGROUND

Knowledge on the effect of seminal plasma on sperm function in extended semen during in vitro storage is lacking.

OBJECTIVES

The aim was to examine the interactive role of sperm concentration and seminal plasma concentration on boar sperm function during in vitro aging.

MATERIAL AND METHODS

Experiment 1: Twenty-one boar ejaculates were aliquoted with Beltsville Thawing Solution into five semen doses containing between 32.5 and 8.5 × 10⁶  sperm/mL. Experiment 2: Semen samples (n = 8) containing 18 × 10⁶ or 10 × 10⁶  sperm/mL with their natural amount of seminal plasma and 10 × 10⁶  sperm/mL substituted with autologous seminal plasma to the same concentration as in doses with 18 × 10⁶  sperm/mL were prepared. Experiment 3: Four variants of semen doses containing 18 × 10⁶ or 10 × 10⁶  sperm/mL with either 10% or 0.5% (v/v) seminal plasma were used. Lipid peroxidation was assessed using Bodipy 581/591 in samples (n = 8) with two different sperm concentrations. Semen was examined during 144-h storage at 17 °C by computer-assisted semen analysis and flow cytometry.

RESULTS

Experiment 1: 3D kinematic patterns revealed a concentration- and time-dependent loss of sperm kinematics in samples with < 23 × 10⁶  sperm/mL (p < 0.05). Percent viable spermatozoa with high mitochondria membrane potential were lower (p < 0.05) in samples with < 15 × 10⁶  sperm/mL. Experiment 2: Seminal plasma supplementation in samples with 10 × 10⁶  sperm/mL did not restore the loss of sperm kinematics (p > 0.05). Experiment 3: At 144 h, motility was lowest in samples containing 10 × 10⁶  sperm/mL and 10% (v/v) seminal plasma (p < 0.05). Sperm lipid peroxidation did not differ between samples with different sperm concentration.

CONCLUSION

Long-term exposure to seminal plasma has a negative impact on in vitro-aged boar spermatozoa. Reduced sperm-to-sperm proximity but not the reduction of seminal plasma limits sperm function in long-term stored boar semen.

Boar management and semen handling factors affect the quality of boar extended semen

Artificial insemination (AI) is the preferred method for reproduction in the majority of the intensive pig production systems Worldwide. To this end, fresh extended ready-to-use semen doses are either purchased from AI-centres or produced by boars kept on-farm. For profitable semen production, it is necessary to obtain a maximum amount of high quality semen from each boar. This paper reviews current knowledge on factors that may affect semen quality by influencing the boar or the semen during processing. Genetic markers could be used for early detection of boars with the highest fertility potential. Genetic selection for fast growth might jeopardize semen quality. Early detection of boars no longer fit for semen production might be possible by ultrasonography of the testes. Seasonal variation in sperm quality could be associated with changes in photoperiod and heat stress during summer. Comfortable housing, with appropiate bedding material to avoid locomotion problems is essential. In some areas, cooling systems may be necessary to avoid heat stress. The sperm quality can be manipulated by feeding strategies aiming, for instance, to increase sperm resistance to oxidative stress and extend storage duration. High collection frequency will negatively influence sperm quality. Also, if collection is not hygienically performed it will result in bacterial contamination of the semen doses. The concern over bacterial contamination has risen not only because of its negative effect on semen quality but also due to the detection of antimicrobial resistance in isolates from extended semen. Moreover, bacterial and viral pathogens must be monitored because they affect semen production and quality and constitute a risk of herd infection. During processing, boar sperm are submitted to many stress factors that can cause oxidative stress and capacitation-like changes potentially reducing their fertility potential. Dilution rate or dilution temperature affects the quality of the semen doses. Some packaging might preserve semen better than others and some plastic components might be toxic for sperm. Standard operation procedures and quality assurance systems in AI centres are needed.

Advances in Breeding Management and Use of Ovulation Induction for Fixed-time AI

The objective of the breeding herd is the predictable and consistent production of high quality pigs. To achieve this objective, an appropriate number of females need to be mated in each breeding week and they should maintain their pregnancy and deliver large litters. Many factors can impact achievement of optimal sow productivity, particularly breeding management. Most matings will involve artificial insemination (AI), and successful AI requires deposition into the cervix (or beyond) of sufficient viable high quality sperm at an appropriate time relative to ovulation. This is facilitated by improved knowledge of the sow's ovarian function prior to and during her oestrous period. Realization of the importance of establishing an adequate sperm reservoir in the oviduct at an appropriate time relative to ovulation has led to advances in the management of AI. The future of AI will likely involve insemination of single doses of high genetic merit semen, potentially having a reduced sperm concentration which is made possible by knowledge of the effect of site of sperm deposition on sow fertility. In particular, knowledge of when a sow is likely to ovulate during a natural or induced oestrous period will prove invaluable in the maintenance of herd productivity. This review will examine options for breeding management, including the control of oestrus and ovulation, on sow herd reproductive performance.

Cluster analysis reveals a binary effect of storage on boar sperm motility function

Storage of liquid-preserved boar spermatozoa is associated with a loss of fertilising ability of the preserved spermatozoa, which standard semen parameters barely reflect. Monitoring responses to molecular effectors of sperm function (e.g. bicarbonate) has proven to be a more sensitive approach to investigating storage effects. Bicarbonate not only initiates capacitation in spermatozoa, but also induces motility activation. This occurs at ejaculation, but also happens throughout passage through the oviduct. In the present study we tested whether the specific response of boar sperm subpopulations to bicarbonate, as assessed by motility activation, is altered with the duration of storage in vitro. Three ejaculates from each of seven boars were diluted in Beltsville thawing solution and stored at 17°C. Only minor changes in the parameters of diluted semen were revealed over a period of 72 h storage. For assessment of bicarbonate responses, subsamples of diluted spermatozoa were centrifuged through a discontinuous Percoll gradient after 12, 24 and 72 h storage. Subsequently, spermatozoa were incubated in two Ca2+-free variants of Tyrode’s medium either without (TyrControl) or with (TyrBic) 15 mM bicarbonate, and computer-aided sperm analysis motility measurements were made. Cluster analysis of imaging data from motile spermatozoa revealed the presence of five major sperm subpopulations with distinct motility characteristics, differing between TyrBic and TyrControl at any given time (P < 0.001). Although there was an increasing loss of motility function in both media, bicarbonate induced an increase in a ‘fast linear’ cohort of spermatozoa in TyrBic regardless of storage (66.4% at 12 h and 63.9% at 72 h). These results imply a binary pattern in response of sperm motility function descriptors to storage: although the quantitative descriptor (percentage of motile spermatozoa) declines in washed semen samples, the qualitative descriptor (percentage of spermatozoa stimulated into fast linear motion by bicarbonate) is sustained independent of the duration of storage.

Bivalent response to long-term storage in liquid-preserved boar semen: a flow cytometric analysis

The fertility of liquid-preserved boar semen declines during storage at 17°C, insemination trials even indicating early losses in fertilizing ability within the first 24-48 h of storage. Standard semen parameters barely reflect these changes in semen quality, and new approaches for assessment of functional changes in stored spermatozoa are needed. Capacitation, the essential prefertilization step for spermatozoa in the female genital tract, is specifically induced in vitro by bicarbonate. Therefore, we have investigated changes in responsiveness of boar spermatozoa to bicarbonate during storage. Ejaculates of 14 boars were diluted in Beltsville thawing solution, cooled to 17°C and stored for 12, 24, 72, 120, and 168 h before investigation. At each time, basic semen quality was characterized by sperm motility and viability. Subsequently, washed subsamples were incubated in variants of an in vitro fertilization (IVF) medium and assessed for kinetic changes of viability (plasma membrane integrity) and intracellular calcium concentration using flow cytometry in combination with propidium iodide and Fluo-3. By this means, it was possible to determine specific effects of bicarbonate and calcium on sperm subpopulations over incubation time. During storage, standard semen parameters remained on a high level. However, flow cytometric analysis of sperm responses to capacitating and control media revealed two opposing effects of storage. There was a loss of response to bicarbonate in part of the live sperm population but an increasing degree of instability in the rest. Assessment of response to capacitating media by flow cytometry appears a markedly more sensitive way of monitoring sperm functionality during storage than the standard semen parameters of motility and viability.

The effect of storage time and number of spermatozoa per insemination dose on semen characteristics and fertilizing capacity of boar semen diluted with Beltsville Thaw Solution (BTS) extender

Semen collection from three boars was performed twice a week, and doses (100 ml each) of semen diluted with Beltsville Thaw Solution (BTS) extender were prepared containing 1 × 109, 3 × 109 and 5 × 109 spermatozoa. Diluted semen was then stored at 17°C for a maximum of 120 h. Percentage of motile spermatozoa (PMS) and type of spermatozoa motility (TSM) were determined by microscopic examinations performed at 24-h intervals, from zero time (beginning of storage at 17°C) up to 120 h of storage, and a sperm motility index (SMI) calculated. Sows (no. = 360) were divided into nine experimental groups (40 sows per group) and a combination of number of spermatozoa per dose and storage time was used for artificial insemination in each group. All the animals were inseminated twice at 12 and 36 h after detection of standing oestrus by a teaser boar. Return and farrowing data including litter size were recorded. PMS, TSM and SMI decreased significantly (P < 0·01) from 48 h up to 120 h of storage, this being more marked in semen doses of 5 × 109 spermatozoa. When semen stored for up to 24 h was used, no significant differences (P > 0·05) regarding return rates and farrowing rates were observed among the three groups inseminated with semen containing different numbers of spermatozoa per dose. Inseminations with semen doses of 1 × 109 and 3 × 109 spermatozoa stored for 48 to 72 h have significantly lower return rates (P < 0·05) and significantly higher farrowing rates (P < 0·05) than with doses of 5 × 109 spermatozoa. Inseminations with semen stored for more than 72 h gave relatively higher return rates and lower farrowing rates. Semen storage time and number of spermatozoa per dose appeared to reduce litter size only where semen doses of 5 X109 spermatozoa were inseminated after storage for more than 48 h.

Protocol optimization for long-term liquid storage of goat semen in a chemically defined extender

A specific problem in the preservation of goat semen has been the detrimental effect of seminal plasma on the viability of spermatozoa in extenders containing egg yolk or milk. The use of chemically defined extenders will have obvious advantages in liquid storage of buck semen. Our previous study showed that the self-made mZAP extender performed better than commercial extenders, and maintained a sperm motility of 34% for 9 days and a fertilizing potential for successful pregnancies for 7 days. The aim of this study was to extend the viability and fertilizing potential of liquid-stored goat spermatozoa by optimizing procedures for semen processing and storage in the mZAP extender. Semen samples collected from five goat bucks of the Lubei White and Boer breeds were diluted with the extender, cooled and stored at 5 degrees C. Stored semen was evaluated for sperm viability parameters, every 48 h of storage. Data from three ejaculates of different bucks were analysed for each treatment. The percentage data were arcsine-transformed before being analysed with anova and Duncan's multiple comparison test. While cooling at the rate of 0.1-0.25 degrees C/min did not affect sperm viability parameters, doing so at the rate of 0.6 degrees C/min from 30 to 15 degrees C reduced goat sperm motility and membrane integrity. Sperm motility and membrane integrity were significantly higher in semen coated with the extender containing 20% egg yolk than in non-coated semen. Sperm motility, membrane integrity and acrosomal intactness were significantly higher when coated semen was 21-fold diluted than when it was 11- or 51-fold diluted and when extender was renewed at 48-h intervals than when it was not renewed during storage. When goat semen coated with the egg yolk-containing extender was 21-fold diluted, cooled at the rate of 0.07-0.25 degrees C/min, stored at 5 degrees C and the extender renewed every 48 h, a sperm motility of 48% was maintained for 13 days, and an in vitro-fertilizing potential similar to that of fresh semen was maintained for 11 days.

Thawing boar semen in the presence of seminal plasma: Effects on sperm quality and fertility

Causes of poor fertility after insemination of frozen-thawed (FT) sperm include reduced sperm viability at thawing and a shorter longevity of surviving sperm in the female genital tract due to sub-lethal damage. The present studies examined the effect of incubating thawed boar sperm in seminal plasma (SP) on sperm membrane integrity (viability), and motility in vitro (experiment 1), and fertility in vivo (experiment 2). For experiment 1, FT sperm from five individual boars and a sperm pool from these boars were thawed and incubated for 4 h in media containing 0%, 10%, or 50% autologous seminal plasma (individual boars) or pooled seminal plasma (sperm pool). At approximately 10 min (0 h) and again at 1 h, 2 h, 3 h, and 4 h, sperm populations were examined for percentage sperm viability and percent sperm motility. Each variable progressively decreased during the incubation period. Incubation in 50% SP increased percentages of live sperm (P < 0.0001) and percent sperm motility (P < 0.01) at all time points compared to incubation in either 0% or 10% SP. For experiment 2, multiparous Large white x Landrace sows (n = 82) each received 900 IU eCG at weaning and 750 IU hCG 80 h later to control time of ovulation. Sows were assigned on the basis of parity to be inseminated with pooled semen with or without SP from the boars used in experiment 1. Sows received 3 x 10(9) live fresh-extended sperm (n = 30) or FT sperm thawed in 80 mL BTS extender (n = 26) or 3 x 10(9) live FT sperm thawed in 80 mL BTS containing 50% SP (FT-SP; n = 26). Sows were inseminated at 36 h, and 42 h after hCG injection. Compared to sows receiving fresh semen, the pregnancy rate of FT inseminated sows tended (P = 0.06) to be lower with the FT-SP group being intermediate. Farrowing rates were not different (83.3%, 69.2%, and 65.4% for fresh, FT, and FT-SP, respectively). Inseminations with FT sperm were associated with a reduction in litter size (P < 0.05), which was not evident in the FT-SP group. Taken together, these data confirm an adverse effect of inseminating FT sperm on sperm quality and sow fertility but suggest that thawing FT sperm in 50% SP may partially alleviate these adverse effects.

Fertility Results of Artificial Inseminations Performed with Liquid Boar Semen Stored in X-CellTMvs BTS Extender

The objective of the present field study was to compare the fertility results for boar semen diluted in X-cell stored up to 4-5 days before artificial insemination (AI) with semen diluted in Beltsville thawing solution (BTS) used for AI following 2-3 days of storage (where the first day being the collection day). A total number of 2601 double inseminations in Norwegian herds were included in this two-trial study. All the boars used in the study were mature cross-bred Norwegian Landrace x Duroc (LD), which were routinely used for AI in Norway. The inseminated gilts and sows were Norwegian Landrace x Yorkshire (LY). The AI doses contained 2.5 billion spermatozoa, and consisted of a mixture of semen from three, occasionally four, boars (i.e. heterospermic semen). Fertility was measured in terms of the likelihood of farrowing and subsequent litter size. The fertility of the semen in both of the extenders was satisfactory and no significant differences were found either in semen stored 4-5 days in X-cell compared with 2-3 days in BTS or in semen stored 2-3 days in X-cell compared with 2-3 days in BTS. The storage capability findings for the long-term extender X-cell could significantly simplify the practical issues of semen production and the distribution of AI doses containing 2.5 billion spermatozoa. However, in pig production systems where all semen is used within 2-3 days, the short-term extender BTS is as good as the more expensive extender X-cell.

Influence of time of insemination relative to ovulation and frequency of insemination on gilt fertility

The objectives of this study were to determine the optimal time of insemination in the pre-ovulatory period (from 32 to 0 h before ovulation) and to evaluate once-daily versus twice-daily inseminations in gilts. In Experiment 1, pre-puberal gilts (n=102) were observed for estrus every 8h and ultrasonography was performed every 8h from the onset of estrus to confirmation of ovulation. The gilts were inseminated once with 4 x 10(9) spermatozoa at various intervals prior to ovulation. Pregnancy detection was conducted 24 days after AI and gilts were slaughtered 4-6 days later. Corpora lutea and the number of viable embryos were counted and the embryo recovery rate was calculated (based on the percentage of corpora lutea). Inseminations performed <24h before ovulation resulted in a higher embryo recovery rate (P=0.02) and produced 2.1 more embryos (P=0.01) than inseminations >or=24h before ovulation. However, the pregnancy rate was reduced when inseminations were performed >16 h before ovulation (P=0.08). In Experiment 2, pre-puberal gilts (n=105) were observed for estrus every 12h and ultrasonography was performed every 12h from the onset of estrus to confirmation of ovulation. Gilts were inseminated (with 4 x 10(9) spermatozoa) 12h after the onset of estrus, with inseminations repeated either every 12h (twice-daily) or 24h (once-daily) during estrus. The gilts were allowed to farrow. There were no differences (between gilts bred twice-daily versus once-daily) for return to estrus rate (P=0.36) and adjusted farrowing rate (P=0.19). However, gilts inseminated once-daily had 1.2 piglets less than those inseminated twice-daily (P=0.09). In conclusion, gilts should be inseminated up to 16 h before ovulation, as intervals >16 h reduced pregnancy rate and litter size.

A retrospective study on effects of storage time of liquid boar semen on reproductive performance in Norwegian swine

The objective of this retrospective field study was to determine the effects of storing, for up to 62 h, heterospermic and homospermic semen in the short-term extender Beltsville thawing solution (BTS), on reproductive performance in Norwegian swine of four different breed combinations. The study was based on fertility records after single or double inseminations with semen collected at an AI station in Norway from January 1998 to June 2001. Increasing the duration of storage of homospermic semen, but not heterospermic semen, from an interval of 4-14 h to an interval of 52-62 h, was associated with a 0.5 piglet reduction in litter size. There were differences in reproductive performance among breed combinations that appeared to be associated with duration of semen storage. In conclusion, prolonged semen storage decreased reproductive performance; the extent varied among breeds and was prevented by the use of heterospermic versus homospermic semen.

Select antioxidants improve the function of extended boar semen stored at 10°C

The objective was to determine the effects of antioxidant addition to extender on viability, acrosome integrity and penetrability in vitro of boar spermatozoa preserved at 10 degrees C. Washed spermatozoa were resuspended at 1 x 10(8) cells/mL in modified Modena solution containing 20% (v/v) boar seminal plasma and 5 mM antioxidant (glutathione, cysteine or hypotaurine). Control aliquots were the same suspension without added antioxidants. Sperm suspensions were then chilled to 10 degrees C with a computerized cooling program. Sperm viability after 7 and 14 d was higher in the presence of glutathione or cysteine, whereas hypotaurine did not improve the survival rate. Percentage of chlortetracycline (CTC) fluorescence pattern as intact live cells was higher in spermatozoa preserved with glutathione or cysteine at 7 and 14 d of preservation. When the preservation period was prolonged until 57 d, survival rate was higher with cysteine than controls. When spermatozoa were preserved with cysteine and then inseminated in an IVF system, penetration rate was not different until 15 d of preservation and higher than controls at 15-29 d, whereas no sows became pregnant after AI with spermatozoa preserved for 21-23 d. Therefore, glutathione and cysteine can improve the viability and functional status of boar spermatozoa during liquid preservation and boar spermatozoa penetrated in vitro even after preservation in the presence of cysteine at 10 degrees C for 29 d.

Accessory sperm: a biomonitor of boar sperm fertilization capacity

The number of accessory sperm found in the zona pellucida of porcine embryos was correlated to their individual quality and to the embryo quality range found within a single sow. Our goal was to determine whether accessory sperm counts provide semen evaluation with additional, useful information. Accessory sperm count was highest when only normal embryos were found in a given sow and diminished if oocytes or degenerated embryos were present (P<0.01). Within a given sow, normal embryos had higher (P<0.05) accessory sperm counts than degenerated embryos, although not when oocytes were also present. Fertilization capacity of sperm is optimal when only normal embryos are found in a given sow; this capacity is indicated by high accessory sperm counts. A decrease in fertilization capacity is reflected in diminishing accessory sperm counts. The boar had a significant effect (P<0.01) on accessory sperm count, but not on the percentage of normal embryos; this suggests that accessory sperm may be more sensitive indicators of the fertilization capacity of sperm than the percentage of normal embryos. We conclude that accessory sperm count can be used for the detection of compensable defects in sperm and is a valid parameter for assessing sperm fertilization capacity.

Sperm factors related to in vitro and in vivo porcine fertility

The prediction of sperm fertilizing ability has great economic importance for breeding herds when artificial insemination is used. Classical methods of semen evaluation generally measure the sperm concentration, progressive motility, percentage of viable cells, and acrosome morphology. These assays are poor in predicting sperm fertility, because only the samples with markedly poor quality can be detected. The development of new sperm tests that measure certain sperm functions is an attempt to solve this problem. On the other hand, the binding and penetration of the zona pellucida is one of the most important barriers the spermatozoa must overcome in the fertilization process. Also, the interaction with the oocyte plasma membrane appears to explain much of the variability in sperm fertilizing potential among fertile boars. Thus, the study of the relationship between sperm factors and in vitro fertility may be a good strategy and assays that include a study of gamete interaction may lead to a better way to predict male fertility than the routine laboratory evaluation of semen. This review will discuss the relationships between sperm factors and fertility in vitro and in vivo (AI trial) with both diluted and frozen-thawed semen. We will also try to analyze the problems and limitations related to the interpretation of boar sperm tests.

The Predictive Value of Porcine Seminal Parameters on Fertility Outcome under Commercial Conditions

The aim of this study was to address the question of whether differences in farrowing rate and litter size after the use of different ejaculates could be predicted using the standard semen parameters under commercial conditions. In this study, a total of 1818 sows were used to evaluate the fertility predictive value of different sperm parameters. Logistic regression analysis (univariate and multivariate) was used to correlate the dichotomous farrowing rate data to the sperm parameters. Linear regression was also used to determine the relationship between litter size and semen parameters (Pearson correlation and multiple regression). Receiver-operating curves (ROC) were used to determine the overall performance characteristics of each semen variable in the logistic regression model. Semen analysis, under commercial conditions, allows to identify ejaculates with very low fertility potential but the pre-selection of the samples, the high number of sperm per doses and the high quality of the semen used in artificial insemination (AI) programmes reduces the variability. Therefore, it is unlikely to detect fertility differences associated with seminal parameters.

Boar sperm storage capacity of BTS and Androhep Plus: viability, motility, capacitation, and tyrosine phosphorylation

Androhep Plus, a long-term extender (up to 7 days) and Beltsville Thawing Solution (BTS), a short-term extender (up to 3 days), are commonly used for liquid storage of porcine semen. To test the hypothesis that modifications in sperm viability, motility, chlortetracycline (CTC) fluorescence patterns, and protein tyrosine phosphorylation occur during semen storage in extenders, we compared these end points at different periods of storage in either Androhep Plus or BTS. Sperm from five boars were assessed daily over 12 days of storage (n = 5 ejaculates from different boars). Viability was not different (P < 0.05 between extenders, except on Day 2, when Androhep Plus maintained better viability. Differences in the percentage of motile (total) sperm due to extender were evident on Days 2, 4, 5, and 6, when Androhep Plus was superior to BTS (P < 0.05). The percentages of progressively motile sperm also differed, with Androhep Plus supporting higher rates on Days 2, 4, 5, 7, 8, 9, 10, and 11 (P < 0.05). The CTC fluorescence pattern distribution differed due to extender as early as Day 2; storage in Androhep Plus induced higher levels of pattern B sperm (P < 0.05) than storage in BTS. A tyrosine-phosphorylated protein of Mr 21,000 appeared after 10 days in sperm incubated in BTS, and was identified as a phospholipid hydroperoxide glutathione peroxidase. Therefore, modifications in viability, motility, CTC fluorescence patterns, and sperm protein tyrosine phosphorylation were apparent during sperm storage in extenders; these may affect the fertilizing capacity of the semen.

A retrospective study on the preserving capacity of a commercial boar semen extender

The objective of this study was to evaluate the preserving capacity of a commercial, long-term boar semen extender beyond 4 days in terms of farrowing failure and total born per litter in sows and gilts. Data from 21 farms were subjected to logistic and linear regression analyses to assess the effect of parity (2-5, > 5 and gilts), wean-to-service interval (</= 5 and >/= 6 days) and number of AI (1, 2, or 3) on the association between semen age (</= 6, 7, 8, 9, and >/=10 days) and fertility. As the semen age increased, the likelihood of farrowing failure increased and total born per litter decreased in sows and gilts. The effect of semen ageing on farrowing failure was more pronounced in sows than in gilts as in the latter it became significant only after 8 days. The effect of semen ageing on total born per litter was similar in both sows and gilts. A lower parity and wean-to-service interval were associated with a reduction in farrowing failure and increase in total born per litter in sows. Increasing the number of inseminations up to two was beneficial in reducing farrowing failure in sows and gilts. A third insemination increased the likelihood of farrowing failure in sows. The number of total born per litter in sows increased with number of inseminations and the effect was not significant in gilts.

Effect of time of ovulation and sperm concentration on fertilization rate in gilts

In normal production practices, sows and gilts are inseminated at least twice during estrus because the timing of ovulation is variable relative to the onset of estrus. The objective of this study was to determine if a normal fertilization rate could be achieved with a single insemination of low sperm number given at a precise interval relative to ovulation. Gilts (n=59) were randomly assigned to one of three treatment groups: low dose (LD; one insemination, 0.5 x 10(9) spermatozoa), high dose (HD; one insemination, 3 x 10(9) spermatozoa) or multiple dose (MD; two inseminations, 3 x 10(9) spermatozoa per insemination). Twice daily estrus detection (06:00 and 18:00 h) was performed using fenceline boar contact and backpressure testing. Transrectal ultrasonography was performed every 6 h beginning at the detection of the onset of standing estrus and continuing until ovulation. Gilts in the LD and HD groups were inseminated 22 h after detection of estrus; MD gilts received inseminations at 10 and 22 h after detection of estrus. Inseminations were administered by using an insemination catheter and semen was deposited into the cervix. The uterus was flushed on Day 5 after the onset of estrus and the number of corpora lutea, oocytes, and embryos were counted. Time of insemination relative to ovulation was designated as 40 to >24 h, 24 to >12 h, and 12 to 0 h before ovulation and >0 h after ovulation. The LD gilts had fewer embryos (P<0.04), more unfertilized oocytes (P<0.05) and a lower fertilization rate (P<0.07) compared to MD gilts. The effects of time of insemination relative to ovulation and the treatment by time interaction were not significant. We conclude that a cervical insemination with low spermatozoa concentration may not result in acceptable fertility even when precisely timed relative to ovulation.

Assessing in vivo fertilizing capacity of liquid-preserved boar semen according to the 'Hanover gilt model'

The goal of this study was to determine the ability of the Hanover gilt model to assess in vivo fertilizing capacity of preserved sperm and to consider whether any modifications to this model were needed. This model evaluates the fertilizing capacity of semen based on the fertilization rate, the rate of normal embryos and the accessory sperm count of 3-5-day embryos. Its distinguishing characteristics are the use of one-time insemination of sperm in reduced numbers, of spontaneously ovulating gilts and of ovulation detection through ultrasound examination of ovaries. Reduced sperm numbers allow for an accurate evaluation of the fertilizing potential of different semen treatments, thereby avoiding the compensatory effect of doses calibrated to maximize fertility. The model's usefulness was assessed in a trial run designed to compare the fertilizing capacity of liquid boar semen diluted into two different extenders. The diluent, the boar and the backflow, had no significant effect on any of the parameters studied. Gilts inseminated less than 24 h before ovulation had a significantly higher (p < 0.01) fertilization rate and accessory sperm cell count (p < 0.05) than those inseminated more than 24 h before ovulation. Very good/good embryos from homogeneous litters (only very good/good embryos were present) had a significantly higher (p < 0.01) accessory sperm count than those from heterogeneous litters (at least one embryo was of a different quality and/or oocytes were present). Both very good/good and degenerated/retarded embryos from heterogeneous litters had low accessory sperm numbers. This suggests that accessory sperm count is significantly related to the quality of the litter, but not to the quality of the embryo within gilts. It can be concluded that the Hanover gilt model is sensitive enough to show fertility differences (in this study, those associated with in vivo ageing of semen), while using relatively few gilts and little time.

Reproductive performance of early-weaned female swine according to their estrus profile and frequency of artificial insemination

We determined the estrus profile (weaning-to-estrus interval (WEI), estrus duration (ED), and frequency of estrus per detection period) in 184 female swine and estimated the effect of the WEI, ED and frequency of artificial insemination (AI) on farrowing rate (FR) and litter size. Estrus detection was done at 8:30 a.m. and 5:00 p.m. The WEI was categorized as short (<100 h), medium (100-120 h) and long (>120 h). The ED was categorized as short (<60 h), medium (60-72 h) and long (>72 h). Mean lactation length was 14.6 days, mean WEI was 124.5 h and mean ED was 69 h. In each weaning group, females received either one or two AI, following a breeding schedule based on the estrus profile. In single-mated females, Al was performed 36 h after the beginning of estrus. In double-mated females, the first AI was done 24 h after the beginning of estrus and the second AI occurred 12 h later. The period of estrus detection had no effect (P > 0.05) on WEI, ED, FR, total born (TB) and live born litter size (LB). Mean FR was 82.6%, mean TB was 10.0% and mean LB was 9.2%. Mean ED was shorter (P < 0.03) for females having medium and long WEI (67.0 and 65.4 h, respectively) than for those having short WEI (72.2 h). A linear regression analysis identified a weak (R2 = 0.02) but significant negative association between ED and WEI (P = 0.05). The WEI did not influence FR (P > 0.05). Total litter size for females having short WEI (9.4) was lower (P < 0.03) than for those having long WEI (10.4). Also, LB for females having medium and long WEI (9.7-9.8) was higher (P < 0.05) than for those having short WEI (8.7). AI frequency had no effect on FR (P > 0.05). TB and LB litter size were lower (P < 0.05) for single-mated females (9.6 and 9.0, respectively) than for double-mated females (10.7 and 9.6, respectively). Double Al was associated with higher subsequent litter size. However, breeding schedules based only on estrus profile may not be precise in determining ideal breeding time, since females having short WEI had the longest ED and produced the lowest litter size.

Storage of boar semen

The problems, aspects and methods of liquid storage and freeze-thawing of boar semen are discussed and a review is given on examination of spermatozoa by the recent fluorescent staining methods.

The time of ovulation in relation to estrus duration in gilts

The objective of this study was to determine time of ovulation, monitored by transcutaneous ultrasonography, relative to the duration of estrus in gilts. We exposed 92 cyclic gilts, Camborough x Canabrid terminal line, at Day 19 of their third estrous cycle to vasectomized boars every 6 h for the detection estrus. Transcutaneous ultrasonography was performed every 6 h, starting 24 h after the onset estrus, to determine time of ovulation. Estrus duration was, on average, 52.6 h (range: 30 to 72 h), and ovulation occurred between 30 and 60 h after the onset of estrus (mean: 44 h), about 85 % of the way through the estrus period. The time of ovulation during estrus was dependent on the duration of estrus (Time of ovulation = (duration of estrus) x 0.409 + 22.7; r = 0.57, P = 0.0001). Prediction of the time of ovulation in relation to duration of estrus is important for determining the optimal time for inseminating gilts. This knowledge would contribute to an improvement in the fertilization rate and in reproductive efficiency of the breeding herd.

The fecundity of porcine semen stored for 2 to 6 days in Androhep and X-CELL extenders

Extending the raw ejaculate prior to artificial insemination (AI) is beneficial, in part, due to the increased number of females that are bred from an ejaculate, along with prolonged shelf life of the semen. The objective of this study was to examine the affects of storage time on the fecundity of porcine semen diluted in 2 semen extenders, Androhep and X-CELL. A completely randomized design with a factorial arrangement of treatments was utilized in which 429 high quality, gel-free ejaculates from 48 boars were used in a timed, double insemination of 1,431 first-service gilts. The gilts were divided into groups and inseminated with semen stored in Androhep or X-CELL for 2 to 3 d, 3 to 4 d, 4 to 5 d, or 5 to 6 d prior to use (day of collection = Day 0). Sperm age was identical, and both extenders were used concurrently each day of the trial. Farrowing rate and litter size data were recorded. Farrowing rates did not differ between extenders through Days 4 to 5 of storage. Gilts inseminated with Androhep diluted stored semen showed a decrease (P < 0.001) in farrowing rate compared with those inseminated with semen extended in X-CELL stored for 5 to 6 d. Mean litter sizes did not differ between extenders through Days 2 to 3 of storage. Compared with the X-CELL extended semen, gilts inseminated with Androhep extended semen produced smaller litters when semen was stored for 4 to 5 d (P < 0.05). Within the Androhep treatment, smaller mean litter sizes (P < 0.05) were evident when the semen was stored for 3 to 4 and 4 to 5 d. No differences were detected in litter size or farrowing rate for gilts bred with semen stored for 2 to 6 d in the X-CELL extender (P > 0.1). The results of this study indicate that extender type influences the fertility potential of fresh porcine semen stored for 2 to 6 d. For optimal fecundity in gilts, semen extended with Androhep extender should be used for AI within 3 d. The X-CELL extended semen can be used for up to 6 d without significant decrease in litter size or farrowing rate. These recommendations are dependent upon using high quality semen that is properly handled from collection through insemination.

The influence of time of insemination relative to time of ovulation on farrowing frequency and litter size in sows, as investigated by ultrasonography

The objective of this experiment was to identify the optimal time of insemination relative to the time of ovulation, based on ultrasonographic detection of embryonic survival at 10 days after ovulation, number of sows farrowing, and litter size. Furthermore, the possible value of the interval from weaning to onset of estrus for prediction of the time of ovulation was examined. Crossbred sows (n = 143) that had farrowed 2 to 9 litters were weaned (Day 0) and observed for estrus every 8 h from Day 3 until end of estrus. Ultrasonography was performed every 6 h, from 12 h after onset of estrus until ovulation had been observed. The sows were inseminated once at various time intervals from ovulation. At Day 16, 25 of the sows were slaughtered and their uteri were flushed for embryos. In the remaining sows, the number of viable and dead piglets and mummified fetuses per sow was recorded at farrowing, with the sum of the 3 constituting the total number of piglets born per sow. The highest number of embryos recovered per sow was found after insemination during the interval from 24 h before to 4 h after ovulation. The lowest frequency of non-pregnant sows and the highest total number of piglets born per sow were found after insemination from 28 h before to 4 h after ovulation. Consequently, the optimal time for insemination was found to be in the interval 28 h before to 4 h after ovulation. The interval from weaning to onset of estrus and from onset of estrus to ovulation were negatively correlated, allowing a rough prediction of the time of ovulation from the interval from weaning to onset of estrus.

Effect of time of insemination relative to ovulation on fertility with liquid and frozen boar semen

Precise data on fertility results following peri- and postovulatory insemination in spontaneously ovulating gilts is lacking. Using transcutaneous sonography every 4 h during estrus as a tool for diagnosis of ovulation, the effects of different time intervals of insemination relative to ovulation were investigated with liquid semen (Experiment 1, n=76 gilts) and frozen semen (Experiment 2, n=80 gilts). In Experiment 3 (n=24 gilts) the number of Day-28 embryos related to the various intervals between insemination and ovulation was determined after the use of liquid semen. Using liquid semen the fertilization rates based on Day-2 to Day-5 embryos and the number of accessory spermatozoa decreased significantly in gilts inseminated with 2 x 10(9) spermatozoa per dosage in intervals of more than 12 h before or more than 4 h after ovulation. In the time interval 4 to 0 h before ovulation, comparable fertilization rates were obtained using frozen semen (88.1%) and liquid semen (92.5%). Fertilization rates and numbers of accessory spermatozoa decreased significantly when gilts were inseminated with frozen semen more than 4 h before or 0 to 4 h after the detection of ovulation. The percentage of Day-28 embryos was significantly higher following preovulatory insemination compared to inseminations 0 to 4 h and 4 to 8 h after ovulation. It is concluded that the optimal time of insemination using liquid semen is 12 to 0 h before ovulation, and 4 to 0 h before ovulation using frozen semen. The results stress the importance of further research on sperm transport and ovulation stimulating mechanisms, as well as studies on the time of ovulation relative to estrus-weaning intervals and estrus duration.