title: New insights into AI semen use and objective semen evaluation in UK Veterinary Practice
Creators: name: Spilman, Mark William
Publisher: name: University of Glasgow
Year: 2019
Subjects: subject: Artificial insemination, cattle.

description: The reproductive performance of breeding cattle is a key driver of sustainable beef and dairy production. Good fertility performance in breeding cattle is a multifactorial phenomenon and the male factors of fertility should not be overlooked. The aim of this study was to investigate the semen handling and storage practices on 47 farms utilising Artificial Insemination (AI) through a questionnaire, and then to use objective multi parametric semen analysis equipment in a veterinary practice to assess the quality of the AI semen in storage on the same beef and dairy farms in North Yorkshire. From these data, the proportion still above breeding company pre-release standards, and differences between conventional and sexed semen, beef and dairy, breed of bull, beef and dairy type of farm were investigated for all assays performed using Students t-test. Fresh semen from bull breeding soundness evaluations was also assessed and in the same laboratory and subjective and objective assessments of motility and morphology assessments compared. Finally semen evaluation results were compared with field fertility data on one farm and correlations reported. There were inconsistencies in how farmers stored and handled semen in storage on their farms. 12.1% of flasks in use were over 14 years old, over half of the herds surveyed (51.7%) did not respond with the age of flask, but 13.8% were new in the last 4 years. Of the herds that responded, the most common response (45.1%) was that liquid nitrogen levels were not checked at all and 6.1% herds checked their liquid nitrogen levels weekly. The majority (19.5%) of farms used a thaw temperature between 370C and 37.90C, next most common was 35 – 35.90C, 36 -36.90C accounted for 2.4% of farms, and only 1.2% of farms used &gt;380C. The majority (28%) of farms that responded thawed straws for between 21 and 30 seconds, but some farms (2.4%) were using short thaw times of less than 10 seconds. Only 9.8% of farms thawed straws for longer than 30 seconds. 70.7% of herds in the study were using DIY AI; less than 25% of herds were using a technician service. 40.2% of herds were carrying out less than 50 serves/month. 30.5% of herds were serving more than 99 times per month. Semen analysis of straws of frozen semen taken from farm storage in North Yorkshire, UK was compared to pre-release standards used in UK and N America. Analysis of conventional and sex sorted semen showed respectively 65% and 70% were above the viability standard; 46% and 0% were above mitochondrial activity standard; 44% and 10% above CASA motility standard; 32% and 10% above CASA progressive motility standard in the UK; 86% and 40% above CASA progressive motility standard in North America (see table 3). Categories of semen were then compared using students t test, following visual assessment of normality. Comparisons between sex sorted and conventional straws showed significant differences in CASA motility (p=0.0182), progressive motility (p=0.0024), mitochondrial activity (p&lt;0.0001) and morphology (p=0.0257). 11 | Page - Straws from dairy sires had significantly greater viability (p=0.0432) and morphology (p&lt;0.0001) than beef sires, whereas straws from dairy farms had significantly greater acrosome integrity (p=0.0043), CASA motility (p=0.0129), progressive motility (p=0.0243) and morphology (p=0.0271) than straws from beef farms. There was no significant difference in motility (p=0.1001) or progressive motility between dairy and beef sires (p=0.0804). There was no significant difference in acrosome integrity between beef and dairy sire (p=0.1959). Investigation of field fertility outcomes on one dairy farm showed significant positive correlations between the flow cytometry viability assay and conception rate (r2 = 85.3% and P = 0.025), and also the CASA % motile at 2 hours post thaw and conception rate (r2 = 90% and P = 0.05). 70 semen samples from bull breeding soundness evaluations were evaluated in the same manner, as well as having manual assessment of morphology performed. Significant differences were present when on farm subjective motility assessments were compared with laboratory-based assessments (CASA motility and subjective), (p&lt;0.0001) but not between CASA motility assessment in the lab and subjective assessment in the lab. There was no difference between morphological evaluations assessed by CASA or manually, despite CASA limitations in picking up sperm head abnormalities. Multiparametric objective semen analysis in a Veterinary practice-based laboratory can offer additional information on the semen in use on farm (AI and natural service), to complement traditional subjective methods. This may allow investigation as to what factors impact on semen quality and which parameters may therefore be most important when selecting semen to use on farm.