CLC improves the post thaw semen quality but not the fertility in Sahiwal bulls

Abstract Text: Sahiwal cattle is the best dairy breed of Pakistan whose purebred population is reduced to an extent where it can be declared as endangered. AI is a tested tool for genetic improvement/ conservation. During cryopreservation, cholesterol is an important component in the regulation of membrane fluidity. The objective of the present study was to determine if addition of cholesterol in semen extender has a beneficial effect on its post-thaw semen quality and pregnancy rate in Sahiwal bulls. Experiment-1: Cholesterol was added to Tris-citric acid semen extender in the form of cholesterol-loaded cyclodextrin (CLC). Extended semen was incubated with CLC at room temperature for 15 minutes before the addition of egg yolk and glycerol. Five replicates of each bull (n=3) were separately evaluated and further processed with at least 60 % sperm motility. Semen samples were diluted at 37° C in extender containing either 1 mg (LOW), 2 mg (MEDIUM), 3 mg (HIGH) of CLC or without (CON) per ml containing 120 million spermatozoa. Post thaw motility (PTM), live spermatozoa (LS), plasma membrane integrity (PMI) and normal apical ridge (NAR) were assessed using standard procedures. Mean PTM, LS and NAR values were significantly (P < 0.05) higher in MEDIUM group (50.33 ± 1.50, 59.53 ± 2.32 and 65.13 ± 1.63 %, respectively) as compared to CON and LOW groups but did not differ (P > 0.05) with HIGH group. Mean PMI was significantly (P < 0.05) higher in MEDIUM group (60.73 ± 1.49 %) as compared to CON but did not differ (P > 0.05) with those of LOW and HIGH groups. Experiment-2: Semen doses from MEDIUM (n=94) or CON (n=94) were used for fertility trial (n=188). Pregnancy rate was numerically higher (63 %) in cows inseminated with semen of MEDIUM group as compared to CON (57%) but did not differ (P > 0.05). It is concluded that addition of cholesterol in MEDIUM concentration (2 mg CLC) to Sahiwal bull semen can improve post-thaw semen quality but not fertility as compared to CON group.  

Keywords: CLC, Sahiwal bull, Semen