Extensive Use Of Artificial Insemination Research Articles

The importance of historically popular sires on the accuracy of genomic predictions of young animals in the US Holstein population

The dairy industry is known for its extensive use of artificial insemination, which has resulted in a population where most animals can be traced back to only a few sires. Due to their relatedness to the population, old influential sires could still contribute to the accuracy of genomic predictions. The objective of the study was to identify the impact of historically influential sires on the recent population. This was tested by constructing a genomic relationship matrix using recursion with different sets of sires. Differences in prediction accuracies with different sets are indicative of how important each set is. Recursion coefficients linking young animals to those sets reveal the relative importance of specific sires to the prediction accuracy of recent animals. The data included ∼10 million scores for stature and fore udder attachment (FUA) measured from 1983. Genotypes of 569,404 animals were available. Sire sets included the 100 most popular sires born within different time periods. Computations were with single-step genomic BLUP. In general, the younger sires had higher prediction accuracies than the oldest sires, even though they generally have fewer progeny. The accuracy of evaluation for stature was increased from 0.54 with the most popular sires born before 1981 to 0.69 with sires born from 2001 to 2010, while the accuracy for FUA increased from 0.47 to 0.61. The accuracy achieved using the overall 100 most used sires was 0.66 for stature and 0.58 for FUA. All 100 sires from each period were combined in a subset to determine the importance of each sire relative to all 400 animals in the combined subset. The highest relative impact of a sire that was born within the different time sets was 1.97 for Valiant (before 1981), 1.94 for Blackstar (1981 to 1990), 4.38 for Shottle (1991 to 2000), and 3.09 for Planet (2001 to 2010). The 3 sires among the 400 with the greatest impact were Shottle, Goldwyn (3.73), and Planet. The relative impact of a sire was not strongly related to the number of progeny. For instance, the relative impact of Durham with 34K progeny was 2.29, whereas the impact of O Man with 15K progeny was 3.13. The impact of a sire is also influenced by whether it was used as a sire of sires. Results show that younger sires are more relevant to the accuracy of breeding value prediction in the recent population.

Proteomic identification of boar seminal plasma proteins related to sperm resistance to cooling at 17 °C

The modern pig industry relies on extensive use of artificial insemination with cooled semen. It is important that semen doses maintain their quality during processing, transport and storage before insemination to guarantee maximum fertility rates. However, ejaculates may respond differently to liquid preservation at 17 °C, despite the optimal quality assessed before cooling. Thus, the aim of this study was to identify differences in seminal plasma proteome of ejaculates with a higher or lower seminal resistance to storage at 17 °C. A total of 148 ejaculates from 65 sexually mature healthy boars were classified as: High Resistance to cooling (HR, total motility > 60% at 144h) and Low resistance to cooling (LR, total motility <60 at 72h). To identify differentially expressed seminal plasma proteins between HR and LR ejaculates, ten ejaculates of each group were analyzed by 2D SDS-PAGE and ESI-Q-TOF mass spectrometry. The proteins associated with HR ejaculates were cathepsin B (spot 2803 and 6601, p < 0.01); spermadhesin PSP-I (spots 3101 and 3103, p < 0.05); epididymal secretory protein E1 precursor (spot 2101, p < 0.05) and IgGFc binding protein (spot 1603, p < 0.01). The protein associated with LR group was the Major seminal plasma PSPI (spot 9103, p < 0.01). To our knowledge, this is the first report of the association of boar seminal plasma proteins to semen resistance to cold storage at 17 °C. These results suggest the use of these proteins as biomarkers for semen resistance to preservation at 17 °C.

Mitochondrial membrane potential and reactive oxygen species in liquid stored and cryopreserved turkey (Meleagris gallopavo) spermatozoa.

The extensive use of artificial insemination in turkeys has led to the development of in vitro semen storage. However, fertility rates from liquid stored and frozen/thawed turkey semen are still unsatisfactory. The aim of the study was to assess spermatozoa viability, mitochondrial membrane potential (MMP), and reactive oxygen species production (ROS) in liquid stored and cryopreserved turkey semen with the use of flow cytometry. Moreover, motility and adenosine triphosphate (ATP) content in sperm were monitored at the same time to link flow cytometry data with sperm movement and energetics. Liquid storage led to a decrease in sperm motility (80.6vs. 55.6%, for fresh and stored for 48h), live sperm with an intact MMP (59.9vs. 30.5% for fresh and stored for 48h), and a 20-fold decrease in ATP content after 24h of storage. A 3-fold increase in ROS+ sperm was observed after 48h of storage (9.3vs. 26.8% for fresh and stored for 48h). Semen equilibration before cryopreservation affected only ATP content. However, freezing/thawing led to a dramatic decrease in all of the studied semen quality parameters. A 5-fold decrease in live sperm with intact MMP (59.8vs. 11.9%) and a 7-fold increase in sperm ROS+ (10.8vs. 74.4%) were recorded between fresh and frozen/thawed semen. The results strongly suggested that a significant loss of MMP and a disturbance in sperm ATP production during semen storage can be the main reason for the decline in sperm motility. The disturbance of mitochondria activity during storage seems to be associated with the increase in oxidative stress in turkey semen. Turkey sperm mitochondria also appear to be very sensitive to cryodamage. Diminished energy production in turkey spermatozoa, visible as the low percentage of sperm with an intact MMP and low level of ATP after freezing/thawing, which is associated with high ROS generation, could be responsible for the low fertilizing ability of cryopreserved turkey semen.

Using PCR-PIRA based genotyping for identifying complex vertebral malformation allele in Frieswal young bulls in India.

Complex vertebral malformation (CVM) has considerable economic impact on dairy cattle breeding due to extensive use of artificial insemination (AI). Identifying the carrier is an important factor to reduce the incidence of the genetic disorder. The study was conducted to identify the carriers of CVM in Frieswal cattle by polymerase chain reaction-primer-introduced restriction analysis (PCR-PIRA) method, which was further confirmed by sequencing. Carrier prevalence of 1% was observed in the Frieswal cattle. The results of the study clearly demonstrated the existence of carriers of CVM among Frieswal bull calves. Due to the widespread use of AI it is recommended to screen young bulls at early stages for this defective allele in order to avoid its rapid spread within the population.

The Influence of Air Contact on the Quality of Extended Boar Semen

Background: The extensive use of artificial insemination in the swine industry emphasizes the need for distribution of good quality semen doses by the artificial insemination centers. A factor that could modify seminal quality is the contact of extended semen with environmental air. However, only few studies have investigated the effects of air presence on semen parameters. Thus, the aim of the present study was to evaluate the influence of different amounts of air on porcine semen quality during the storage period.Materials, Methods &amp; Results: Four ejaculates from five sexually mature boars were used. Each ejaculate (n = 20) was isothermically diluted (30 x 106/mL) in a BTS-extender and assigned to three groups differing on the amount of air entrapped within the polystyrene tubes (100 mL). In group AIR-0 the tubes were completely filled with extended semen (0% air); in group AIR-25, 75% of the tube volume was filled with extended semen and 25% with air; in group AIR-50, 50% of the tube volume was filled with extended semen. The semen doses were stored at 17.3 ± 0.5ºC for 120 h. The motility parameters were assessed at 24, 72 and 120 h of storage using a CASA system. The evaluation of acrosomal integrity was performed by examining formalin-fixed samples under phase-contrast microscopy (1000 x) at 72 and 120 h of storage. The pH was measured at 24, 48, 72, and 120 h of storage with a digital pH-meter. At 120 h, samples were incubated in waterbath at 38°C for the thermoresistance test and sperm motility was assessed after 30 and 120 min of incubation. For each time analysis, a different sealed tube was used in order to maintain a constant amount of air within the tubes during storage. Data were analyzed as repeated measures using the GLIMMIX procedure of SAS® Software. Boar and week of collection were included as random effect in the model. Groups were compared using the Tukey-Kramer test at a significance level of 5%. The pH was significantly influenced by the amount of air entrapped within the tubes (P &lt; 0.01). Throughout the experiment, the pH of semen doses was higher as the amount of air increased within the tubes. The mean pH for groups AIR-50, AIR-25 and AIR-0 was 7.51 ± 0.06, 7.25 ± 0.06 and 7.07 ± 0.06, respectively. Overall motility was similar among the groups for up to 24 h of storage. At 72 h and 120 h of storage, total, progressive and rapid motility were higher (P &lt; 0.05) in AIR-0 compared to AIR-50. The kinematic parameters DAP and VAP decreased as the volume of air within the tubes increased (P &lt; 0.05). Group AIR-0 exhibited higher values (P &lt; 0.05) for DSL, DCL, VSL, VCL, BCF, and WOB compared to AIR-25 and AIR-50. Furthermore, after the thermoresistance test performed at 120 h of storage, total motility, progressive motility and rapid motility were negatively affected (P &lt; 0.05) by the increasing amounts of air within the tubes. There was no effect of air amount within the semen doses on acrosome integrity (P &gt; 0.05).Discussion: The presence of air within tubes affects the quality of extended semen during storage, resulting in increase of pH and subsequent decrease in motility preservation. This pH-rise could be explained by the loss of CO2 from the diluted semen to the air compartment within the tube. At the same time, it is possible to infer that this event influences the intracellular pH of the spermatozoa, increasing sperm metabolism and, consequently, impairing sperm motility. Therefore, we conclude that avoiding air presence within storage containers is recommended in order to ensure the quality of boar semen doses.

Recent artificial selection in U.S. Jersey cattle impacts autozygosity levels of specific genomic regions.

BackgroundGenome signatures of artificial selection in U.S. Jersey cattle were identified by examining changes in haplotype homozygosity for a resource population of animals born between 1953 and 2007. Genetic merit of this population changed dramatically during this period for a number of traits, especially milk yield. The intense selection underlying these changes was achieved through extensive use of artificial insemination (AI), which also increased consanguinity of the population to a few superior Jersey bulls. As a result, allele frequencies are shifted for many contemporary animals, and in numerous cases to a homozygous state for specific genomic regions. The goal of this study was to identify those selection signatures that occurred after extensive use of AI since the 1960, using analyses of shared haplotype segments or Runs of Homozygosity. When combined with animal birth year information, signatures of selection associated with economically important traits were identified and compared to results from an extended haplotype homozygosity analysis.ResultsOverall, our results reveal that more recent selection increased autozygosity across the entire genome, but some specific regions increased more than others. A genome-wide scan identified more than 15 regions with a substantial change in autozygosity. Haplotypes found to be associated with increased milk, fat and protein yield in U.S. Jersey cattle also consistently increased in frequency.ConclusionsThe analyses used in this study was able to detect directional selection over the last few decades when individual production records for Jersey animals were available.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1500-x) contains supplementary material, which is available to authorized users.

Effect of sample stratification on dairy GWAS results

BackgroundArtificial insemination and genetic selection are major factors contributing to population stratification in dairy cattle. In this study, we analyzed the effect of sample stratification and the effect of stratification correction on results of a dairy genome-wide association study (GWAS). Three methods for stratification correction were used: the efficient mixed-model association expedited (EMMAX) method accounting for correlation among all individuals, a generalized least squares (GLS) method based on half-sib intraclass correlation, and a principal component analysis (PCA) approach.ResultsHistorical pedigree data revealed that the 1,654 contemporary cows in the GWAS were all related when traced through approximately 10–15 generations of ancestors. Genome and phenotype stratifications had a striking overlap with the half-sib structure. A large elite half-sib family of cows contributed to the detection of favorable alleles that had low frequencies in the general population and high frequencies in the elite cows and contributed to the detection of X chromosome effects. All three methods for stratification correction reduced the number of significant effects. EMMAX method had the most severe reduction in the number of significant effects, and the PCA method using 20 principal components and GLS had similar significance levels. Removal of the elite cows from the analysis without using stratification correction removed many effects that were also removed by the three methods for stratification correction, indicating that stratification correction could have removed some true effects due to the elite cows. SNP effects with good consensus between different methods and effect size distributions from USDA’s Holstein genomic evaluation included the DGAT1-NIBP region of BTA14 for production traits, a SNP 45kb upstream from PIGY on BTA6 and two SNPs in NIBP on BTA14 for protein percentage. However, most of these consensus effects had similar frequencies in the elite and average cows.ConclusionsGenetic selection and extensive use of artificial insemination contributed to overlapped genome, pedigree and phenotype stratifications. The presence of an elite cluster of cows was related to the detection of rare favorable alleles that had high frequencies in the elite cluster and low frequencies in the remaining cows. Methods for stratification correction could have removed some true effects associated with genetic selection.

Dynamics of Tritrichomonas foetus Infection in Bulls Used for Natural Service in a Florida Dairy Farm

The economic impact of bovine trichomonosis has been well reported for beef and grazing livestock. However, in dairy farms the extensive use of artificial insemination (AI) has reduced its prevalence. The one exception is those herds where natural service (NS) is a part of the reproductive management and the potential for venereal disease transmission exist. In the US, a considerable number of dairies use bulls in their reproductive program. In the Southeast, de Vries et al, (2005) reported that 70% of herds used NS along with an AI program. Worldwide trichomonosis is considered a major cause of infertility in cattle bred by natural service. Tritrichomonas foetus (T. foetus) is a flagellate, obligate, anaerobic protozoa which causes venereal disease in domestic animals. The transmission of T. foetus occurs at coitus when an infected bull breeds a susceptible female or vice versa. In bulls, the infection is asymptomatic. In females, the protozoa cause embryonic death during early stages of pregnancy and temporary infertility. However, pyometra or abortions are the only clinical signs that may be observed. The objective of this study was to evaluate the prevalence of T. foetus in dairy bulls used for natural service in Florida dairy farm.

5078 Treatment of leptomeningeal involvement of breast cancer with high-dose methotrexate and ifosfamide

Progeny-test (PT) programs of US artificial-insemination (AI) organizations were examined to determine timeliness of sampling, PT daughter distribution, rate of return of PT bulls to widespread service, and genetic merit of PT bulls compared with AI-proven and natural-service (NS) bulls. Bull age at semen release and at birth and calving of PT daughters was documented by breed (Ayrshire, Brown Swiss, Guernsey, Holstein, Jersey, and Milking Shorthorn) for bulls that entered AI service since 1960. Mean Holstein bull age at semen release (16 mo) changed little over time, but standard deviations (SD) decreased from 4.0 mo during the 1960s to 2.4 mo during the 1990s. Most Holstein bulls (80%) had semen released by 18 mo. Mean age of Holstein bulls at birth and calving of PT daughters during the 1990s was 29 and 56 mo, respectively (a decline of 4 mo from the 1960s); SD decreased from 6 to 3 mo. Bulls of other breeds usually were older at birth and calving of PT daughters, and SD were larger. Mean Holstein bull age when 80% of PT daughters had been born declined from 36 mo during the 1960s to 31 mo during the early 1990s; for other breeds, bulls showed the same trend but at older ages. Mean Holstein bull age when 80% of PT daughters had calved declined from 65 mo during the 1960s to 59 mo during the 1990s; for other breeds, bulls were older. Percentage of herds with PT daughters has increased over time. For Holsteins, herds with five or more usable first-parity records that had PT daughters with usable records increased from 15% during 1965 to 61% during 1998; percentage of herds with from 1 to 19% PT records increased from 11 to 38%, and percentage of herds with >50% PT daughters increased from 1 to 5%. Percentage of Holstein PT bulls returned to AI service declined to about 12% for bulls with PT entry around 1990; for other breeds, 12 to 23% of most recent PT bulls were returned to service. Percentage of milking daughters that had records usable for genetic evaluation that were sired by PT bulls increased steadily from 10 to 18%, whereas percentage of daughters with usable records that were sired by NS bulls declined from 14 to 7%. Milk yield of daughters of AI-proven bulls was 107 to 200 kg greater than for daughters of PT bulls and 366 to 444 kg greater than for daughters of NS bulls for all years. More extensive and rapid sampling and increased selection intensity of PT programs have led to more rapid genetic progress. More extensive use of AI could increase US producer income by millions of dollars annually.

Genetic Analysis of Male and Female Fertility After Artificial Insemination in Sheep: Comparison of Single-Trait and Joint Models

The outcome of an insemination depends on male and female fertility. Nevertheless, few studies have incorporated genetic evaluation of these 2 traits jointly. The aim of this work was to compare genetic parameter estimates of male and female fertility defined as success or failure to artificial insemination (AI), using 8 different models. The first 2 models were simple repeatability models studying fertility of one sex and ignoring any information of the other. Models 3 and 4 took into account the information of the other sex by the inclusion of its random permanent environmental effect, whereas models 5 and 6 included fixed effects of the other sex. Models 7 and 8 were joint genetic evaluation models of male and female fertility ignoring or considering genetic correlation. Data were composed of 147,018 AI of the Manech Tête Rousse breed recorded from 2000 to 2004 corresponding to 79,352 ewes and 963 rams. The pedigree file included 120,989 individuals. Variance component estimates from the different models were quite similar; heritabilities varied from 0.050 to 0.053 for female fertility and were near 0.003 for male fertility. Correlations among estimated breeding values in the same sex using different models were higher than 0.99. The genetic correlation between male and female fertility was not significantly different from 0. These results show that for French dairy sheep with extensive use of AI, estimation of breeding values for male and female fertility might be implemented with quite simple models.

Prevalence of mycoplasmas in the semen and vaginal swabs of Danish stallions and mares

The reproduction rate of horses is one of the lowest within domestic livestock despite advances the veterinary medicine. Infertility in horses may be due mainly to the lack of suitable selection criteria in the breeding of horses. However, acquired infertility due to genital, bacterial infections may occur. Mycoplasmas have been implicated in genital disorders and infertility of many species including humans and horses. However, their role as commensals or pathogens of the genital tract of horses is still not determined. Bacteriological examinations made on the fossa glandis, urethra, penis and semen of stallions, showed the presence of different Mycoplasma species. Therefore our study aimed to find the prevalence of Mycoplasma species and a possible association with fertility problems in Danish riding horses. Eighty semen samples from stallions and 19 vaginal swab samples from mares were tested by PCR for presence of mycoplasmal DNA. The vaginal swab samples were also cultured in the Mycoplasma specific medium. None of the samples were positive for presence of genital mycoplasmas during the screen. The lack of genital mycoplasmas observed in this study may be due to a very extensive use of artificial insemination of modern sport horses.

Effects of liquid storage on amidase activity, DNA fragmentation and motility of turkey spermatozoa

Short-term liquid storage of turkey semen is of great interest in the management of turkey reproduction due to the extensive use of artificial insemination. This study examined changes in DNA fragmentation (using a comet assay), sperm motility characteristics (using computer-aided sperm analysis), and amidase activity (using a colorimetric assay) of turkey sperm stored for 24 and 48 h. In addition we found that turkey spermatozoa contain besides acrosin, additional two serine proteinases of molecular weight of 34 and 42 kDa. We found that, after 48 h of liquid storage, decreases in sperm motility characteristics and increases in amidase activity and DNA fragmentation occurred. An increase of amidase activity was found after 24 h. Decreases in sperm motility and increase in DNA fragmentation were found after 48 h of storage. These data suggest that a decrease in turkey sperm quality during short-term storage is related to disturbances to the acrosome, presumably related to premature activation of acrosomal serine proteinases, and to a lesser extent a decrease in sperm motility characteristics and damage of sperm DNA.

Increasing storage time of extended boar semen reduces sperm DNA integrity

There is an extensive use of artificial insemination (AI) in the pig industry. Extended liquid boar semen may be used for insemination for up to 5 days after collection. The objective of this study was to determine the changes in sperm quality, when boar semen was extended and stored at 18 °C for up to 72 h post-collection. The study included three ejaculates from five boars, for each of the four breeds: Duroc, Hampshire, Landrace and Danish Large White ( n = 60 ejaculates). The sperm chromatin structure assay (SCSA) showed an increase in DNA fragmentation index (DFI) after 72 h of incubation ( P < 0.001), with no differences between breeds ( P = 0.07). For two Hampshire boars, all ejaculates had a large increase in DFI after 24 h of incubation. The standard deviation of DFI (SD-DFI) differed between breeds, with the SD-DFI for Hampshire being significantly greater than for the other breeds. The SD-DFI did not change during the 72 h of storage. Sperm viability was determined using SYBR-14 and propidium iodide in combination with flow cytometry. The sperm viability did not differ between breeds ( P = 0.21), but a difference in viability during storage ( P < 0.001) was detected. In conclusion, the SCSA cytogram patterns were consistent for different ejaculates within boars and storage of extended boar semen at 18 °C for 72 h significantly decreased the integrity of sperm DNA.

Roles of antioxidants on prolonged storage of avian spermatozoa in vivo and in vitro.

This review focuses on natural and assisted prevention against lipid peroxidation in avian spermatozoa. The presence of high levels of n-6 polyunsaturated fatty acids (PUFAs) in the plasma membrane creates favorable conditions for the formation of peroxidative products, a major cause of membrane damage which may ultimately impair male fertility. However, a complex antioxidant system involving vitamin C, vitamin E and GSH is naturally present in avian semen. Coupled with a battery of enzymatic defenses (e.g., SOD, GSH-Px either Se- or non-Se-dependent), this system acts to prevent or restrict the formation and propagation of peroxides. The presence of specialized sites dedicated to prolonged sperm storage in avian females raises the question of durable protection of sperm membranes against peroxidation. Preliminary observations have revealed the presence of a specific antioxidant system at these sites in which vitamin C could exert a major role. From a practical standpoint, the extensive use of artificial insemination in poultry, along with the emergence in some species of workable techniques to cryopreserve spermatozoa, demand better control of peroxidation occurring in the plasma membrane of spermatozoa before or during storage. Dietary supplementation with vitamin E is effective in limiting lipid peroxidation of sperm plasma membranes, both in chickens and turkeys. In addition, organic Se with or without vitamin E stimulates Se-GSH-Px activity in seminal plasma. Preliminary observations in female chickens have also revealed the effectiveness of dietary supplementation with vitamin E, organic selenium or both to sustain fertility in aging flocks.

Dairy genetic improvement through artificial insemination, performance recording and genetic evaluation

Artificial insemination (AI) of dairy cattle in Canada was started more than half a century ago and today it is estimated that at least 75% of all dairy cattle nationally are bred using this common reproductive technology. A Best Linear Unbiased Prediction sire model for estimating genetic evaluations for production traits was introduced in 1975. The combination of extensive use of AI with genetic evaluations for bulls and cows has resulted in significant phenotypic and genetic gains over the past 20 yr. In the Holstein breed, mature equivalent yields have increased by an average of 200 kg milk, 7.0 kg fat and 6.3 kg protein per year since 1980. Genetically, the relative emphasis realized for production traits versus overall type during the past 5 yr has followed the 60:40 breeding goal represented in the Lifetime Profit Index, which has increased at an average rate of 0.28 standard units per year. Examination of the generation interval in the Canadian Holstein breed, associated with each of the four pathways for genetic improvement, indicates a 46% increase in the rate of annual genetic gain today compared to 20 yr ago. The increased accuracy and intensity of selection associated with the use of AI and genetic evaluations have also contributed to the rates of phenotypic and genetic progress achieved over the years. In the future , AI will continue to be a critical component of the genetic gains possible in dairy cattle breeding but it will be complemented by other reproductive technologies aimed at further reducing generation intervals and increasing the accuracy and selection of intensity, especially on the female side. Key words: Dairy cattle, artificial insemination, genetic progress, genetic evaluation

Timeliness and Effectiveness of Progeny Testing Through Artificial Insemination

Progeny-test (PT) programs of US artificial-insemination (AI) organizations were examined to determine timeliness of sampling, PT daughter distribution, rate of return of PT bulls to widespread service, and genetic merit of PT bulls compared with AI-proven and natural-service (NS) bulls. Bull age at semen release and at birth and calving of PT daughters was documented by breed (Ayrshire, Brown Swiss, Guernsey, Holstein, Jersey, and Milking Shorthorn) for bulls that entered AI service since 1960. Mean Holstein bull age at semen release (16mo) changed little over time, but standard deviations (SD) decreased from 4.0mo during the 1960s to 2.4mo during the 1990s. Most Holstein bulls (80%) had semen released by 18mo. Mean age of Holstein bulls at birth and calving of PT daughters during the 1990s was 29 and 56mo, respectively (a decline of 4mo from the 1960s); SD decreased from 6 to 3mo. Bulls of other breeds usually were older at birth and calving of PT daughters, and SD were larger. Mean Holstein bull age when 80% of PT daughters had been born declined from 36mo during the 1960s to 31mo during the early 1990s; for other breeds, bulls showed the same trend but at older ages. Mean Holstein bull age when 80% of PT daughters had calved declined from 65mo during the 1960s to 59mo during the 1990s; for other breeds, bulls were older. Percentage of herds with PT daughters has increased over time. For Holsteins, herds with five or more usable first-parity records that had PT daughters with usable records increased from 15% during 1965 to 61% during 1998; percentage of herds with from 1 to 19% PT records increased from 11 to 38%, and percentage of herds with >50% PT daughters increased from 1 to 5%. Percentage of Holstein PT bulls returned to AI service declined to about 12% for bulls with PT entry around 1990; for other breeds, 12 to 23% of most recent PT bulls were returned to service. Percentage of milking daughters that had records usable for genetic evaluation that were sired by PT bulls increased steadily from 10 to 18%, whereas percentage of daughters with usable records that were sired by NS bulls declined from 14 to 7%. Milk yield of daughters of AI-proven bulls was 107 to 200kg greater than for daughters of PT bulls and 366 to 444kg greater than for daughters of NS bulls for all years. More extensive and rapid sampling and increased selection intensity of PT programs have led to more rapid genetic progress. More extensive use of AI could increase US producer income by millions of dollars annually.

Effects of method of embryo production and transfer on pregnancy rate, embryo survival rate, abortion and calf production in beef cows

Progeny-test (PT) programs of US artificial-insemination (AI) organizations were examined to determine timeliness of sampling, PT daughter distribution, rate of return of PT bulls to widespread service, and genetic merit of PT bulls compared with AI-proven and natural-service (NS) bulls. Bull age at semen release and at birth and calving of PT daughters was documented by breed (Ayrshire, Brown Swiss, Guernsey, Holstein, Jersey, and Milking Shorthorn) for bulls that entered AI service since 1960. Mean Holstein bull age at semen release (16 mo) changed little over time, but standard deviations (SD) decreased from 4.0 mo during the 1960s to 2.4 mo during the 1990s. Most Holstein bulls (80%) had semen released by 18 mo. Mean age of Holstein bulls at birth and calving of PT daughters during the 1990s was 29 and 56 mo, respectively (a decline of 4 mo from the 1960s); SD decreased from 6 to 3 mo. Bulls of other breeds usually were older at birth and calving of PT daughters, and SD were larger. Mean Holstein bull age when 80% of PT daughters had been born declined from 36 mo during the 1960s to 31 mo during the early 1990s; for other breeds, bulls showed the same trend but at older ages. Mean Holstein bull age when 80% of PT daughters had calved declined from 65 mo during the 1960s to 59 mo during the 1990s; for other breeds, bulls were older. Percentage of herds with PT daughters has increased over time. For Holsteins, herds with five or more usable first-parity records that had PT daughters with usable records increased from 15% during 1965 to 61% during 1998; percentage of herds with from 1 to 19% PT records increased from 11 to 38%, and percentage of herds with >50% PT daughters increased from 1 to 5%. Percentage of Holstein PT bulls returned to AI service declined to about 12% for bulls with PT entry around 1990; for other breeds, 12 to 23% of most recent PT bulls were returned to service. Percentage of milking daughters that had records usable for genetic evaluation that were sired by PT bulls increased steadily from 10 to 18%, whereas percentage of daughters with usable records that were sired by NS bulls declined from 14 to 7%. Milk yield of daughters of AI-proven bulls was 107 to 200 kg greater than for daughters of PT bulls and 366 to 444 kg greater than for daughters of NS bulls for all years. More extensive and rapid sampling and increased selection intensity of PT programs have led to more rapid genetic progress. More extensive use of AI could increase US producer income by millions of dollars annually.