Ovulation timing and conception risk after automated activity monitoring in lactating dairy cows.

Using 1 market-available activity monitor, 3 experiments were conducted in dairy cows to determine timing of ovulation, compare within-herd conception risk of cows inseminated based on activity monitors versus timed artificial insemination (AI), and determine conception risk of cows inseminated at various intervals after achieving an activity threshold. In experiment 1, ovaries were scanned every 3h by transrectal ultrasonography to determine the time of ovulation beginning 14 ± 0.5 h after the achieved activity threshold (n=132) or first standing event (n=59), or both (n=59). Progesterone at the first ovarian scan (0.1 ± 0.01 ng/mL) and ovarian structures [1 or 2 preovulatory-sized follicles (16.5 ± 0.2 mm)] confirmed that 88.6% of cows identified by activity were in estrus. The remaining 15 cows (11.4%) with a corpus luteum and elevated progesterone concentration (5.3 ± 0.5 ng/mL) were classified as false positives. The average interval from first standing event to ovulation (n=59) differed slightly from the interval after the achieved threshold (26.4 ± 0.7 vs. 24.6 ± 0.7 h, respectively). In 97 cows fitted with activity monitors, that interval was 25.7 ± 0.4 h. In experiment 2, the conception risk in 394 cows in 1 herd fitted with activity monitors was compared with that of 413 cows submitted to a timed AI program through 3 AI services. Days to first AI were reduced in cows fitted with activity monitors, and conception risk after activity threshold was less than that for timed AI at first service because of differing days in milk at first AI. Both median and mean days to pregnancy, however, were reduced in activity-group cows by 10 and 24 d, respectively, compared with timed AI cows. In experiment 3, 4,019 cows in 19 herds were inseminated after achieving the activity threshold. Conception risk was determined for cows inseminated at various intervals after the achieved activity threshold. A curvilinear conception risk curve peaked at 47.9% for primiparous cows inseminated between 13 and 16 h, whereas conception risk in multiparous cows was steady at 34% through 12 h and decreased thereafter. These experiments demonstrate that time of ovulation after activity threshold closely resembles the time of ovulation after first standing estrus. Time of insemination up to 12h after the activity threshold produced similar conception risks for multiparous cows, whereas intervals shorter than 13 and greater than 16 h in primiparous cows seemed to compromise their conception risk. Although conception risk may not be improved at individual inseminations after achieving an activity threshold, the rate of achieving pregnancy is hastened. Activity monitors can accurately predict ovulation and time of AI.

Effects of sex-sorting and sperm dosage on conception rates of Holstein heifers: is comparable fertility of sex-sorted and conventional semen plausible?

The conception rates of Holstein heifers after AI with 2.1 or 10 × 10(6) sperm dosages of sex-sorted or conventionally processed sperm were compared. Ejaculates collected by artificial vagina from 8 Holstein sires were cryopreserved at either 2.1 or 10 × 10(6) sperm per dose with or without sorting to 90% purity for X-chromosome-bearing spermatozoa using flow cytometry. All treatments were processed in an egg-yolk (20%), TRIS, glycerol (7%) extender and packaged in color-coded 0.25-mL French straws. Straws (n=350 straws/treatment per sire) were packaged and distributed in aliquots of 12 (3 straws of each treatment) to 51 herds of Holstein heifers. Straw color was recorded in the on-farm record keeping system at the time of AI and retrieved by electronic download. In total, 9,172 services were recovered, providing a mean sample size of 287±3.5 services/sperm dose per semen type within sire (range: 248 to 318). Conception rates were influenced by the main effects of herd, sire, semen type, sperm dosage, and service number. The herd by sperm dosage interaction was the only interaction determined to be significant and implies that some herds (technicians) are more proficient than others at maintaining high levels of conception with decreased sperm dosages. Across herds and sires, the conception rates of each semen type by sperm dosage combination were as follows: 2.1 × 10(6) sex-sorted, 38%, n=2,319; 10 × 10(6) sex-sorted, 44%, n=2,279; 2.1 × 10(6) conventional, 55%, n=2,282; and 10 × 10(6) conventional, 60%, n=2,292. The observation that conception rates of sex-sorted semen were improved by the 10 × 10(6) sperm dosage is encouraging toward the prospectus of development of a commercially available sex-sorted product with improved conception potential over existing technology. However, the failure of the 10 × 10(6) sex-sorted sperm dosage to achieve conception rates comparable to either dosage of conventional semen is somewhat discouraging toward the plausibility of comparable conception rates to conventional semen in the absence of major technological advances in efficiency of sperm sorting or cryopreservation.

Effects of 2.1 and 3.5x10(6) sex-sorted sperm dosages on conception rates of Holstein cows and heifers.

The objective was to compare conceptions rates of Holstein cows and heifers after artificial insemination (AI) with 2.1 or 3.5x10(6) sex-sorted sperm or 15x10(6) conventional sperm. Ejaculates collected from 7 Holstein sires were cryopreserved conventionally at 15x10(6) sperm per dose or sorted to 90% purity for X-chromosome-bearing spermatozoa using flow cytometry and cryopreserved at either 2.1 or 3.5x10(6) sperm per dose. All treatments were processed in an egg-yolk (20%), Tris, glycerol (7%) extender and packaged in color-coded 0.25-mL French straws. Straws (n=700 straws/dosage per sire) were packaged and distributed in aliquots of 12 (4 straws/sperm dosage) to 69 Holstein herds with an across-herd goal of achieving approximately 50% use in heifers and cows. Straw color was recorded in the on-farm recordkeeping system at the time of AI and retrieved by electronic download. Data for cows and heifers were analyzed separately. Among heifers, 6,268 services were retrieved from 45 herds (298+/-4.2 services/sperm dose per sire; range: 244 to 344). Conception rate of heifers was influenced by the sire by treatment interaction. Conception rate of the 2.1 and 3.5x10(6) sex-sorted sperm dosages were comparable in 6 of 7 sires. Conception rate of both sex-sorted dosages were less than those of conventional semen for 6 of 7 sires. Across sires, heifer conception rates for 2.1 and 3.5x10(6) sex-sorted sperm dosages and 15x10(6) conventional dosages were 44, 46, and 61%, respectively. Among cows, 5,466 services were retrieved from 52 herds (260+/-3.3 services/sperm dose per sire; range: 236 to 289). Conception rates of cows were influenced by herd, sire, and sperm dosage. Conception rates of the 2.1 and 3.5x10(6) sex-sorted sperm dosage were comparable for all 7 sires. Conception rates of 2.1x10(6) sex-sorted sperm dosage were less than those of conventional semen for 4 of 7 sires and conception rates of the 3.5x10(6) sex-sorted sperm dosage were less than those of conventional semen for 2 of 7 sires. Across sires, conception rates for 2.1 and 3.5x10(6) sex-sorted sperm dosages and 15x10(6) conventional dosages in cows were 23, 25, and 32%, respectively. In conclusion, these data could not confirm that a meaningful improvement in conception rates should be expected in cows or heifers from increasing sex-sorted sperm dosage from 2.1 to 3.5x10(6) sperm per dose.

Evaluating the success of sex-sorted semen in US dairy herds from on farm records.

These data summarize on-farm records of dairy herds (n=211) using sexed semen. Sexed semen was predominantly used at first and second service in virgin heifers, which is reflected in younger ages at AI and at calving. Conception rates at first service averaged 47% for Holstein heifers and 53% for Jersey heifers, which were approximately 80% of that achieved with conventional semen. Analysis of inter-estrus intervals provides no evidence that cycle lengths are extended by use of sexed semen. Among singleton births, 89% were reported as female offspring and this rises to 90% for gestation lengths within a normal 265-295 d range. Age at calving appeared to interact with calf sex and semen type to influence the incidence of stillbirths. Semen type had no effect on the incidence of stillbirths among heifers delivering female calves. However, the incidence of stillbirths among heifers delivering male calves was greater for those conceived from sexed semen and was only partially explained by age at calving. Because the incidence of male calves from sexed semen is only 10%, the total incidence of stillbirths was not affected by semen type. In conclusion, failure to differentiate sexed from conventional semen in data recording and preferential bias in use of sexed semen in younger, more fertile females makes legitimate comparisons of sexed and conventional semen in the commercial setting difficult. When used in Holstein heifers, the average first service conception rate achieved with sex-sorted semen was 47%, which appeared to approximately 80% of that achieved with conventional semen in the same herds. The percentage of female calves (89%) was consistent with expectations. After adjusting for age at calving, sexed semen had no affect on the total incidence of stillbirths, however the source for an apparent increased incidence of stillbirth among male calves born from X-sorted sperm populations requires further investigation.

Effect of sex-sorted sperm dosage on conception rates in Holstein heifers and lactating cows.

Ejaculates were collected by artificial vagina from 3 Holstein sires and sorted to 90% purity for X-chromosome-bearing spermatozoa (range 88 to 93%) using flow cytometry. Sorted sperm were diluted to 2.1, 3.5, or 5.0 x 10(6) sperm per dose in an egg yolk (20%), Tris, glycerol (7%) extender. Collections were repeated until >600 straws per sperm dose per sire were obtained. Each sperm dose was loaded into color-coded 0.25-mL French straws, with alternate colors used to define treatments across sires. Within sires, straws were packaged at 9 per cane (3 of each color) and strategically allocated to 75 Holstein herds with targets for 50% use in heifers and 50% in lactating cows. Straw color was recorded in the on-farm record-keeping system at the time of insemination. Data were analyzed separately for cows and heifers. Among heifers, a total of 2,125 usable records were retrieved from 51 herds (238 +/- 5.5 services/ sperm dose per sire, range: 218 to 263). Conception rates in heifers were influenced by the sire x sperm dosage interaction. Within sire A, conception rates of heifers were greater for the 5 x 10(6) (59.5%) than for the 2.1 x 10(6) (46.4%) sperm dose and intermediate for the 3.5 x 10(6) sperm dose (52.2%). However, across sires, sperm dosage had no effect on heifer conception rates (46.7, 51.2, and 52.5% for the 2.1, 3.5, and 5.0 x 10(6) sperm dosages, respectively). Among cows, a total of 2,369 services were retrieved from 56 herds (263 +/- 8.8 services/sperm dose per sire, range: 233 to 303). Conception rates of cows (29.4%) were not affected by sire or sperm dosage (27.0, 29.1, and 30.3% for the 2.1, 3.5, and 5.0 x 10(6) sperm dosages, respectively). In conclusion, these data indicate that an increased sperm dosage may enhance virgin heifer conception rates for some (but not all) sires, whereas neither sire nor sexed-sperm dosage affected conception rates of lactating cows. Additional studies of sexed-sperm dosage across a larger sampling of bulls are warranted to determine whether and how such a practice can be implemented cost effectively for the benefit of the dairy industry.

Voluntary waiting period management practices in dairy herds participating in a progeny test program.

A survey was mailed to approximately 4,000 herds participating in a young sire progeny test program to estimate the percentage of herds that selectively alter the voluntary waiting period (VWP) for individual cows or groups of cows. Responses were received from 673 herds (17%; 583 Holsteins, 55 Jerseys, 35 other dairy breeds). The mean VWP cited by respondents was 56 +/- 0.6 d (range = 30 to 90 d) and did not differ by breed. Among responding herds, 64% (432/673) indicated the VWP was selectively altered for one or more reasons. The most frequently cited reasons for altering the VWP were postpartum health (50%), season (18%), milk yield (18%), parity (14%), and other reasons (14%). In Holstein herds that altered the VWP based on milk yield, the highest production group averaged 14 more days to first service than the lowest production group (> or =40 vs. <20 kg of energy-corrected milk, respectively). In contrast, days to first service were nearly identical for all production groups in Holstein herds that did not vary the VWP based on milk yield. In conclusion, management decisions to selectively alter the VWP led to differences in days to first service and may have a confounding effect on genetic estimates of daughter fertility. Opportunities to improve the accuracy of daughter pregnancy rate estimates may reside in models that adjust for VWP management decisions on a within-herd basis.

Relationships among lipid peroxidation, glutathione peroxidase, superoxide dismutase, sperm parameters, and competitive index in dairy bulls.

Sperm membranes contain high concentrations of polyunsaturated fatty acids that are highly susceptible to oxidative damage that interferes with fertilization ability. The objective of this study was to determine associations among lipid peroxidation (thiobarbituric-acid-reactive substance concentration), antioxidant enzymatic activities in frozen spermatozoa, and competitive indices. Semen from multiple ejaculates collected in succession from each bull (four Holstein and four Jersey) was pooled. Heterospermic doses (20x10(6)sperm/0.5mL straw) were made to obtain 16 Holstein/Jersey combinations (equal number of sperm from each bull). Cows were inseminated on observed or synchronized estrus. The sire of calves (N=460) was determined; based on the number of calves sired, a competitive index was obtained for each bull. Prior to preparation of the heterospermic doses, a sub-sample of semen from each bull was taken, processed, frozen, and stored concurrent with heterospermic samples. After thawing, these homospermic samples were assessed for lipid peroxidation, superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, DNA fragmentation index (DFI), plasma membrane integrity (PMI), and total progressive motility (assessed by CASA). Sperm lipid peroxidation and the competitive index were negatively correlated (r=-0.78; P<0.05), the DFI and sperm lipid peroxidation were positively correlated (r=0.86; P<0.001), and there were negative correlations (P<0.05) for sperm lipid peroxidation and both PMI and total progressive motility (r=-0.78 and -0.83, respectively). There was neither significant association between SOD activity and competitive index, nor between GPx activity and competitive index. In conclusion, bulls with lower sperm lipid peroxidation had higher chances of siring calves; this was attributed to the deleterious effects of lipid peroxidation on sperm plasma membrane integrity and sperm DNA, which may reduce sperm fertilizing potential.

Effect of presence of clinical and subclinical endometritis at the initiation of Presynch-Ovsynch program on the first service pregnancy in dairy cows.

The present study examined the effect of presence of clinical or subclinical endometritis at the initiation of Presynch-Ovsynch estrous synchronization program on the first service pregnancy rate in dairy cows. Lactating Holstein cows (N=275) were given a thorough reproductive examination at 32-38 days in milk, 3 days prior to the scheduled start of Presynch-Ovsynch program. Based on the reproductive exam findings the cows were diagnosed and classified into three groups as clinical endometritis, subclinical endometritis and normal. All cows received two set-up injections of 25mg PGF(2alpha) (Lutalyse((R)), Pfizer Animal Health, New York, NY, USA) i.m., 14 days apart starting at 35-42 days in milk (DIM). All cows received 75microg of GnRH (Cystorelin, Merial, Iselin, NJ, USA) i.m. 14 days after the second pre-synchronization injection of PGF(2alpha), followed by a third injection of 25mg PGF(2alpha) i.m. 7 days later. Cows received a second injection of 75microg of GnRH i.m. 54h after the third PGF(2alpha), and received timed artificial insemination at the time of the second GnRH injection or 24h later. Multivariate logistic regression was used to analyze the odds of pregnancy at the first service. Variables included in the model were endometritis status (clinical endometritis, subclinical endometritis and normal), farm (two), presence of corpus luteum (CL, yes or no), timing of second GnRH in relation to AI (0 or 24h), sire fertility (bulls with greater compared with lesser estimated relative conception rates), parity (primiparous and multiparous) and their interactions. Of all variable included in the model, cows with corpus letuem (OR=1.83 versus OR=1.00; P=0.05) 3 days prior to the scheduled start of Presynch-Ovsynch program and primiparous cows (OR=1.00 versus OR=0.55; P=0.04) had increased odds of becoming pregnant at the first service. No differences were found in the odds of first service pregnancy among clinical, subclinical endometritis and normal cows (P>0.1). In summary, presence of clinical or subclinical endometritis at the initiation of Presynch-Ovsynch estrous synchronization program does not harm the first service pregnancy rate in dairy cows.

Effect of sire fertility and timing of artificial insemination in a Presynch + Ovsynch protocol on first-service pregnancy rates.

Sire fertility may influence pregnancy rate (PR) by differences in sperm survival in the female reproductive system and time required for capacitation and transport of sperm to site of fertilization. A predicted fertility index, Estimated Relative Conception Rate, was used to select 3 high-fertility artificial insemination (AI) sires (+3) and 3 average AI sires (-1). Ovulation can be predicted to occur at approximately 28 h following GnRH administration when used in an Ovsynch protocol. The objective of this study was to determine if AI at 2 times, 0 or 24 h after GnRH administration, in a Presynch + Ovsynch protocol resulted in different first-service PR when average or high-fertility sires were used. Lactating Holstein cows (n = 1,457) from 2 dairy herds located in the Piedmont region of North Carolina were utilized for 12 mo. Timing of AI did not affect first AI PR and no interaction of sire-fertility group and timing of AI was detected. First AI PR did not differ between sire-fertility groups (23.2 vs. 29.4%) for average and high-fertility groups, respectively. First-lactation cows were 53% more likely to conceive than older cows, and cows bred during April through June were 66% less likely to become pregnant compared with cows bred from October through January. No interactions were detected among parity, season, sire-fertility group, or time of AI. Using only 3 sires per group based on Estimated Relative Conception Rate estimates resulted in large variability of sire conception within groups, although group averages differed by 6 points.

Breed differences in competitive indices of Holstein and Jersey bulls and their association with sperm DNA fragmentation index and plasma membrane integrity.

The objective was to evaluate the relationship of a competitive index (CI) determined by heterospermic performance and post-thaw semen quality of the same stored ejaculates. Semen from multiple ejaculates collected in succession from each bull (four Holstein and four Jersey) was pooled. Heterospermic doses (20x10(6)/straw) were made to obtain all possible Holstein-Jersey combinations (16 two-bull combinations) and contained 20x10(6) sperm/mL/bull. Cows at two University dairy farms were inseminated on observed or synchronized estrus. The sire of calves (N=460) were determined and a CI was determined for each bull (based on the number of calves sired). Prior to preparation of the heterospermic doses, a sub-sample of semen from each bull was taken, processed, frozen, and stored concurrently with heterospermic samples. Post-thaw semen samples (homospermic) from each bull were assessed for: sperm morphology, acrosome integrity, sperm motility parameters assessed by computer assisted sperm analysis (CASA), flow cytometry analysis of DNA Fragmentation Index (DFI), and Plasma Membrane Integrity (PMI). Heterospermic performance of Holstein bulls was superior to that of Jersey bulls. The DFI was negatively correlated to CI (r=-0.87; P<0.001), whereas the PMI (r=0.87; P<0.001) and total progressive motility (r=0.74; P<0.05) assessed by CASA were positively correlated to CI. In multivariate regression models, the DFI and PMI accounted for 87% variance in competitive index. In conclusion, bulls with less DFI and higher PMI had higher probabilities of siring calves.

Comparison of three estrus detection systems during summer in a large commercial dairy herd.

The objective of the study was to compare three systems for estrus detection and combinations of these systems on a large commercial dairy (1075 lactating cows) during stress of summer heat. At 37-45 days in milk (DIM), 255 cows were fitted with a HeatWatch device (HW; DDx Inc., Denver, CO), an activity sensor ALPRO (ALPRO; DeLaval Inc., Kansas City, MO), and visually observed (VO) three times daily. Pregnancy status was determined by uterine palpation per rectum 35-49 days following artificial insemination (AI). Effects of DIM, parity, standing events, inseminator, and interval between onset of estrus and AI on conception rates were determined using logistic regression. Efficiencies for detection of estrus, determined by comparing detected periods of estrus with a theoretical total of 570 periods, were 49.3% (VO), 37.2% (ALPRO), 48.0% (HW), and 80.2% for all three systems simultaneously. Conception rates (LSM+/-S.E.) for cows detected by one or more of the three systems were 6.2+/-3.9 for VO, 19.8+/-5.6 for ALPRO, 17.3+/-5.0 for HW, 22.8+/-7.0 for VO+ALPRO, 26.9+/-4.6 for VO+HW, 23.2+/-5.2 for ALPRO+HW, and 18.4+/-4.7 for VO+ALPRO+HW. Inseminations performed during no and mild heat stress (temperature-humidity index; THI< or =76) had greater conception rate (P<0.05; 38.8%) compared to AI performed during moderated heat stress conditions (THI>76; 17.6%). Number of mounts were higher for primiparous versus multiparous cows (P<0.05). Cows over 80 DIM during estrus exhibited fewer (P<0.05) standing events. The highest conception rate occurred with the combination of VO+HW, which confirms the premise that combination of multiple systems enhances both the efficiency and accuracy of estrus detection.

Fertility following fixed-time AI or insemination at observed estrus in Ovsynch and Heatsynch programs in lactating dairy cows.

The objective of this study was to compare the conception rate for fixed-timed artificial insemination (FTAI) and observed heat artificial insemination (HAI) prior to the scheduled FTAI in Ovsynch and Heatsynch synchronization protocols. In Experiment 1, lactating dairy cows (n=535) received two set-up injections of 25mg prostaglandin F(2alpha) (PGF(2alpha)) i.m., 14 days apart starting at 36+/-3 days in milk (DIM). Cows were blocked by parity and were randomly allocated to either Ovsynch or Heatsynch groups. All cows received 100 microg of GnRH i.m. 14 days after the second set-up injection of PGF(2alpha), followed by a third injection of 25mg PGF(2alpha) i.m., 7 days later. In the Ovsynch group, HAI cows (n=29) were bred on standing estrus after the third PGF(2alpha) before the scheduled second GnRH, whereas FTAI cows (n=218) that were not observed in estrus, received a second injection of 100 microg of GnRH i.m., 48 h after the third PGF(2alpha) and received TAI 8 h after the second GnRH. In the Heatsynch group, all cows (n=288) received 0.5 mg of estradiol cypionate (ECP) 24 h after third PGF(2alpha) and HAI cows (n=172) were bred on standing estrus and FTAI cows (n=116) that were not observed in estrus, received TAI 72 h after the third PGF(2alpha). In Experiment 2, repeat breeder cows (n=186) were randomly assigned to either Ovsynch or Heatsynch groups. The FTAI and HAI cows were inseminated similar to Experiment 1. All cows were observed for estrus three times daily. The associations with the conception rate were modeled with logistic regression separately for Experiments 1 and 2. Of all the variables included in the model in Experiment 1, type of AI (HAI versus FTAI, P=0.0003) and parity (primiparous versus multiparous, P=0.05) influenced the first service conception rate. Over-all conception rate and first service conception rate for HAI cows were higher compared to FTAI cows (33.8% versus 21.3%, and 35.3% versus 21.0%; P=0.001). In the Heatsynch group, cows that received HAI had significantly higher over-all conception rate and first service conception rate compared to FTAI (35.2% versus 17.3% and 36.0% versus 15.5%; P=0.0001). The conception rates in repeat breeder cows for HAI and FTAI (30.1% versus 22.3%) were not different (P>0.1). In conclusion, it was recommended to include AI at observed estrus and fixed-time AI for cows not observed in estrus in order to improve the conception rate in synchronization protocols.

Technology and applications for encapsulated spermatozoa.

A technique for microencapsulation of bovine spermatozoa has been developed with minimal spermatozoal injury and thus, a potential use in artificial insemination (AI). Membranes made of the following polymers have proven best: poly-l-lysine, polyarginine, polyvinylamine, and protamine sulfate. Successful encapsulation has been achieved for capsules ranging in size from 0.75 to 1.5 mm, and sperm concentrations from 45 to 180 x 10(6) cells/ml. Successful buffers include Cornell University Extender and egg yolk citrate - glycerol (maximum 10% v/v egg yolk for normal capsular shape). Capsule fragility (ability to rupture under aging and physical stress) was negatively related to membrane thickness which ranges from 1.92 microm to 5.32 microm (controlled by polymer concentration, molecular weight, and exposure time) and positively to concentration of sperm encapsulated. On delivery to the porcine reproductive tract, the capsule constructed of poly-l-lysine membranes ruptured between 12 and 24 hr after insemination. Heterospermic studies have shown that encapsulated sperm are capable of fertilization in vivo, but are at a disadvantage to unencapsulated sperm when AI is at conventional times following detection of estrus.

Microencapsulation of bovine spermatozoa for use in artificial insemination: a review.

A technique for microencapsulation of bovine spermatozoa has been developed with minimal spermatozoal injury and thus of potential use in artificial insemination. The polymers poly-l-lysine, polyvinylamine and protamine sulfate have proven best for membranes. Encapsulation has been successful with capsules ranging in size from 0.75 to 1.5 mm, and with sperm concentrations from 45 to 180 x 10(6) cells mL-1. Successful extenders include CUE, CAPROGEN, and egg yolk-citrate-glycerol (maximum 10% v/v egg yolk for normal capsular shape). Capsule fragility (ability to rupture under ageing and physical stress) is negatively related to membrane thickness which ranges from 1.92 to 5.32 microns (depending on the concentration of polymer used) and positively related to concentration of sperm encapsulated. Heterospermic studies have shown that encapsulated sperm are capable of fertilization in vivo, but are at a disadvantage to unencapsulated sperm when cows are inseminated at conventional times. Uterine retention of inseminates is favoured by capsules having a 'sticky' membrane. Using current procedures, preliminary homospermic fertility studies indicate that sperm encapsulated with poly-l-lysine or protamine sulfate may achieve normal fertility.

Relationship of seminal traits and insemination time to fertilization rate and embryo quality.

The nature of subfertility due to the male or inseminate is as complex as that of the female. Fertilization failure or failure in embryogenesis are both documented to be of seminal origin. Males also differ in the numbers of sperm required to reach their maximum fertilization rate. Males requiring more sperm would be considered to have compensable seminal deficiencies. These include a number of known (viability and morphology) and unknown factors (functional or molecular traits) precluding sperm access to the ovum or ability to engage the ovum sufficiently to initiate fertilization and the block to polyspermy. Differences in fertility among males or inseminates independent of sperm dosage are considered uncompensable. These deficiencies would be associated with fertilizing sperm that are incompetent to maintain the fertilization process or subsequent embryogenesis once initiated, with most failures occurring prior to maternal recognition of pregnancy. Such sperm would preempt fertilization by competent sperm. Chromatin aberrations in morphologically normal or near normal spermatozoa from abnormal semen samples appear to be the best candidates for the uncompensable deficiency. However, recognition of uncompensable or incompetent fertilizing sperm has not been achieved. Six-day-old non-surgically recovered bovine ova/embryos have been used to evaluate compensable and uncompensable seminal deficiencies as well as to test reproductive strategies. These ova/embryos provide information on fertilization status and embryo quality as well as quantitative and qualitative data regarding associated accessory sperm. Thus, they permit the separation of reproductive failure by fertilization from that by embryonic development. Accessory sperm number is positively associated with both fertilization rate and embryonic quality. Early insemination results in low fertilization rates (low accessory sperm number), but good embryo quality, whereas, late insemination results in high fertilization rates (high accessory sperm number), but poor embryo quality. Additional studies will be necessary to substantiate this model; however, if true, future research designed to improve results to artificial insemination should be tested by breeding early in estrus where sperm viability is most limiting and embryo quality is best.

Automated electronic systems for the detection of oestrus and timing of AI in cattle.

For the majority of dairy herds where artificial insemination (AI) is practiced, the limiting factor toward obtaining efficient reproductive performance is the failure to detect oestrus in a timely and accurate manner. Periodic visual observation has been the dominant method used to identify cows in oestrus. New approaches are being developed to provide automated systems of detection of oestrus using electronic technology. The goal of an oestrus detection program should be to identify oestrus positively and accurately in all cycling animals and consequently to identify animals not cycling. The ultimate goal should be to predict the time of ovulation, thus allowing for insemination that will maximize the opportunity for conception. Unfortunately, most studies designed to evaluate the optimal time of AI generally contained two technical deficiencies: inadequate numbers of cows for valid statistical comparisons and inaccurate knowledge of the onset of oestrus because of low frequency of visual observations and/or efficiency of methods used for the detection of oestrus. Studies using pedometry and a pressure sensing radiotelemetric system will be reviewed as each have independently obtained an optimal time of AI of 5 to 17 h after either the increase in locomotive activity or following the first standing event associated with the onset of oestrus.

Encapsulation of porcine spermatozoa in poly-lysine microspheres.

Three experiments were conducted to examine the effects of incubating porcine spermatozoa in concentrated samples, to determine the viability of sperm encapsulated in microspheres and to evaluate the potential of microencapsulating porcine spermatozoa for use in artificial insemination. In Experiment 1, sperm incubated at 4, 15, 20 or 37 degrees C and at concentrations of 7.5, 15, 30, 60 or 120 x 10(6) sperm/ml lost motility over a 16-h incubation period. Sperm motility was significantly lower at 4 degrees C than at 15, 20 or 37 degrees C and was significantly higher in more concentrated samples. In Experiment 2, sperm were encapsulated in poly-lysine microspheres at concentrations of 30, 60 or 120 x 10(6) sperm/ml and incubated in vitro at 4, 15 or 20 degrees C. Unencapsulated samples were incubated at similar concentrations and temperatures and served as controls. Motility and percentage of sperm with intact acrosomes were estimated at 2, 4, 8 and 16 h of incubation. The procedure of encapsulation did not affect sperm motility or acrosomal morphology; however, there was an accelerated loss of motility in encapsulated samples. There were no differences in acrosomal morphology between the two groups across time. In Experiment 3, sperm were encapsulated at a concentration of 120 x 10(6) sperm/ml and 20 ml of capsules were inseminated into estrous sows. Uterine contents were flushed at 3, 6 and 24 h after insemination and examined for capsules. Capsules containing motile sperm were recovered from sows at 3 and 6 h, but not at 24 h. These results demonstrate that porcine spermatozoa can be encapsulated in microspheres and that these capsules can be inseminated into estrous females, but the sperm undergo an accelerated loss of motility in vitro and in vivo.

The accuracy of enzyme-linked immunosorbent assay and latex agglutination progesterone test for the validation of estrus and early pregnancy diagnosis in dairy cattle.

The accuracy of the enzyme-linked immunosorbent assay (ELISA) and the latex agglutination (LA) on-farm progesterone kit for detecting estrus and diagnosing early pregnancy was investigated in this study. Italian Friesian dairy cows (n=82) from 6 dairy herds were used for the collection of foremilk samples at the time of breeding and at 19, 21, and 23 days post insemination. Pregnancy status was ascertained by uterine palpation per rectum 40 to 60 days post insemination. Progesterone levels were affected by herd, percentage of milk fat, and the day of testing x diagnosis interaction. Validation of estrus by qualitative on-farm tests was 74.6% (LA) and 100.0% (ELISA) accurate using 0.5 ng/ml of progesterone as the RIA estimate for estrus. The accuracy rate for early pregnancy diagnosis by RIA was 68.4 to 83.8% for day 19 and day 21, respectively, while the detection rate for nonpregnancy was 84.6 to 100% on day 19 and day 21, respectively, as compared with uterine palpation per rectum. The average accuracy rate for early pregnancy diagnosis ranged from 84.7 to 92.3% for the LA and ELISA tests, respectively; the nonpregnancy rate was correctly predicted 93.9% to 68.2% for the LA and ELISA tests, respectively.

Predictive value of palpation per rectum vs milk and serum progesterone levels for the diagnosis of bovine follicular and luteal cysts.

Diagnosis of bovine follicular and luteal cysts by palpation per rectum was compared with diagnosis by progesterone status, as determined by an enzymeimmunoassay (EIA). A 2x2 contingency table analysis allowed the calculation of predictive value, sensitivity and specificity for the palpation diagnosis of both cyst types. The results were 75.0, 61.9 and 50.0% for follicular cysts and 35.1, 50.0 and 61.9% for luteal cysts, respectively. The EIA results were compared to radioimmunoassay (RIA). The predictive value for a low progesterone determination (<5ng/ml) was 91.8% and for high progesterone (5ng/ml or >) it was 83.3%. The sensitivity and specificity for the EIA were both 88.2%. Within the EIA system, milk and serum samples agreed a total of 85 out of 87 times (97.7%). Definitive diagnosis of follicular or luteal cysts should not be based upon palpation per rectum alone. The EIA was found to be the better definitive diagnostic technique.

Evaluation of an on-farm blood progesterone test for predicting the day of parturition in cattle.

An on-farm blood progesterone enzymeimmunoassay (EIA) was evaluated as a diagnostic test to predict the time of calving within a 24-hour period in near-term dairy cows. Blood samples were taken daily from 45 cows beginning 5 days prior to their expected due dates until calving, and plasma was stored at -20 degrees C until all cows had calved. The EIA test was performed on frozen-thawed plasma samples, and progesterone concentrations were determined to be low (positive test for calving within 24 hours) or high (negative test for calving within 24 hours). Sensitivity, specificity and predictive value of the EIA to accurately determine parturition within 24 hours were 86.7, 90.8 and 75.0%, respectively. The EIA correctly predicted the day of parturition in 168 of 187 (89.8%) plasma samples. Ten additional cows were similarly monitored except the EIA was performed on whole blood immediately after collection, and the sensitivity, specificity and predictive value of the test were 80.0, 97.6 and 88.9%, respectively. The day of parturition was correctly predicted in 49 of 52 (94.2%) whole blood samples. More than 95% of the cows calved within 24 hours when their plasma progesterone reached < 1.3 ng/ml. When results of the EIA were compared with those of a radioimmunoassay (RIA), the EIA findings were used to correctly classify 190 of 232 (81.9%) plasma samples as having low (< 2.0 ng/ml) or high (>/= 2.0 ng/ml) concentrations of progesterone. The EIA test was found to be a quick, practical means of estimating progesterone concentrations in bovine plasma or whole blood and was a useful test for predicting the day of parturition in cows.