Pregnancy outcome after insemination of frozen-thawed bovine semen packaged in two straw sizes: A meta-analysis

Abstract

The 0.25-mL French straw has been thoroughly studied and compared with the 0.5-mL French straw for about 40 yr. The 0.25-mL straw has some distinct advantages over the 0.5-mL straw in terms of storage efficiency and extender usage. The 0.25-mL straw is more sensitive to temperature change, which may be an advantage in some freezing systems with a slow freezing rate, but provides no advantage when the freezing rate is accelerated to optimize freezing in 0.5-mL straws. Disadvantages of the 0.25-mL straw include increased sensitivity to post-thaw temperature change, slightly more difficult handling, and inferior readability. Fertility of cattle inseminated with extended semen packaged in 0.25-mL straws assessed in 13 studies (>770,000 inseminations) had a weighted advantage of 0.9% (0.7% unweighted advantage) compared with semen packaged in 0.5-mL straws. In 2 studies in which palpated conception rates were obtained, the weighted advantage of the 0.25-mL versus the 0.5-mL straw was 0.2% (0.4% unweighted advantage). Paired t-tests did not detect a significant difference in pregnancy outcome between straw sizes. Logistic regression of all 15 studies (>780,000 inseminations) detected large variation among studies and tended to detect a small advantage for the 0.25-mL straw. Meta-analyses applied to fixed- or random-effect models of all 15 studies indicated the average odds of having a greater pregnancy outcome with the 0.25-mL straw were either 3 or 4% greater. Based on these odds ratios, the expected proportion of difference in pregnancy outcome translated into a difference of 0.74%. These small differences in pregnancy outcomes do not provide compelling evidence that a transition from 0.50- to 0.25-mL straws in the United States is warranted, especially given the added negative aspects of semen handling and the greater potential for technician x straw type interactions among herdsman inseminators.

Evaluation of Sperm Kinetics and Plasma Membrane Integrity of Frozen Equine Semen in Different Storage Volumes and Freezing Conditions

“…The inferior results observed for 0.25-mL straws can be dependent (at least partially) on the freezing systems used in this experiment. Of note, such interference was already reported by Stevenson et al [18].…”

Spermatozoa motility, viability, acrosome integrity, mitochondrial membrane potential and plasma membrane integrity in 0.25 mL and 0.5 mL straw after frozen-thawing in Hanwoo bull

“…Canada and Europe have adopted 0.25 mL straw while the United States and South America have adopted 0.5 mL straw. The optimal straw size and fertility rate are disputed among herdsman and technicians (Stevenson et al, 2009). In Korea, bull semen has been cryopreserved in 0.5 mL straw with semen extender based on tris-citric acid supplemented with 20% egg yolk.…”

“…AI technicians and dairy and beef farm owners are often concerned that the low spermatozoa may reduce the conception rate. Nevertheless, there was no reduction in the conception rate after the introduction of 10-30 million spermatozoa for AI (Stevenson et al, 2009).…”

“…About 10-30 million spermatozoa are filled in 0.25 mL or 0.5 mL straw, distributed to farms, and used for AI worldwide (Stevenson et al, 2009). The 0.25 mL straw has half the volume of the 0.5 mL straw and more than two 0.25 mL straws can be preserved in the LN 2 tank (Johnson et al, 1995).…”

The effects of ambient temperature and humidity on pregnancy rate in Beefmaster cows in a subtropical environment of Mexico

“…Semen from different sires was used proportionally every month, in order to avoid confounding effects of bull and climatic conditions. Conception rate in cows differ widely between inseminators (Stevenson et al, 2009), but this effect could not be isolated because this information was not available. Nonreturn cows were rectally palpated around 50 d post insemination for confirmation of pregnancy.…”