Lipid deficient extender for bovine spermatozoa: its development and use in measuring freezing-induced lipid loss

Pellet-freezing of Damascus goat semen in a chemically defined extender

During the breeding season of goats (12 bucks and 64 does) in Egypt, five experiments were conducted using a chemically defined cryoextender (CDE) to investigate: (1) the influence of rates of semen dilution (1:2, 1:4 and 1:19) and methods of thawing of frozen semen pellets (dry thawing versus wet thawing) on sperm progressive motility (SPM), sperm acrosome abnormalities (SAA) and rate of lipid peroxidation in semen as measured by malonaldehyde (MAL) production, and (2) the effect of insemination of does in natural (n = 38) and cloprostenol-synchronized (n = 26) estrus with frozen semen on their kidding rates and prolificacy. Semen (two successive ejaculates/buck) was collected twice a week via an AV and only ejaculates of >2500 x 10(6) sperm/ml and 70% SPM were diluted in one step at 30 degrees C with the CDE, cooled to 5 degrees C over a 4h-period, frozen in the form of 0.30 ml pellets and stored in liquid nitrogen for 72 h. The results revealed that post-thaw SPM of semen diluted at a rate of 1:4 was significantly (P < 0.01) higher than that of semen diluted at the other rates. Dilution of semen at a rate of 1:19 (< or =151 x 10(6) sperm/ml) not only minimized (P < 0.01) pre-freeze and post-thaw SPM, but also augmented (P < 0.01) pre-freeze and post-thaw rates of lipid peroxidation as evidenced by the high level of MAL production and the ability of antioxidants (1mg/ml EDTA, 200 U/ml bovine liver catalase, 0.61 mg/ml reduced glutathione and 0.11 mg/ml sodium pyruvate) to restore (P < 0.01) pre-freeze and post-thaw SPM. Frozen semen pellets exposed to dry thawing had a greater percentage of SPM (P < 0.01) as well as lower values of SAA and MAL (P < 0.01) than those exposed to wet thawing. Although the kidding rates did not vary significantly among does in natural (55.26%) and synchronized (53.85%) estrus, a higher (P < 0.05) prolificacy was obtained after their insemination in natural (1.81+/-0.16) rather than in synchronized (1.22+/-0.11) estrus.

Fertility of bull sperm frozen and stored in clarified egg yolk-Tris-glycerol extender

Egg yolk-Tris-glycerol extender, which is widely used in commercial artificial insemination (AI), was modified by replacing the 20% egg yolk (vol/vol) with a supernatant from egg yolk centrifuged at 50,000 x g for 2 h and then used to cryopreserve bull sperm. Preliminary studies showed that 20% egg yolk interfered with biochemical assays, which could be overcome by centrifugation. In Experiment 1, semen from 4 Holstein bulls was frozen in the experimental Tris extender and compared with the whole milk-glycerol control. A total of 2256 first services resulted in 72.6% 60- to 90-d nonreturns for the control and 71.0% for the Tris extender. In Experiment 2, semen from 10 Holstein bulls was frozen in the experimental Tris extender. Half of the semen was used immediately and half was stored in liquid nitrogen for 1 yr before distribution. The nonreturn rates based on 8878 first services for 7 bulls that completed both parts of the trial were 70.9% initially and 71.6% 1 yr later. This time trend difference of 0.7% was comparable to 0.6% for the AI mean for Holstein sires used at the same time. These fertility results and previous laboratory studies indicate that the conventional egg yolk-Tris-glycerol might be simplified for cryopreserving bull sperm. The experimental Tris extender also was suitable for making biochemical measurements.

Bovine spermatozoa in vitro: A review of storage, fertility estimation and manipulation

In vitro storage of bovine spermatozoa virtually indefinitely has provided the opportunity to distribute conveniently and widely germ plasm from superior sires and benefit the productivity of cattle around the world. Techniques developed in our laboratories are well on their way to being able to predict accurately the fertility of young, prospective sires without the inconvenience and expense of large field trials. Manipulation of spermatozoa provides opportunities for the predetermination of sex of resulting offspring, the introduction of foreign DNA into oocytes, and the formation of transgenic individuals. Many other possibilities are limited only by the ingenuity of those conducting research in this exciting field.

Effects of package, extender, and light on stored frozen bull spermatozoa

Spermatozoa were analyzed when fresh, freshly frozen, and stored at --196 C for 6 and 18 mo after processing in egg yolk-citrate and Promine-D extender with varying exposure to light and packaging in straws or glass ampules. Over all treatments there were decreases with time in spermatozoal motility, oxygen uptake, and cellular glutamic oxaloacetic transaminase due to freezing-thawing. Percent progressive motility decreased from spermatozoa freshly frozen (36.5%) to those stored for 6 mo (33.6%). Oxygen uptake in freshly frozen samples was 8.4 microliter per 10(8) cells per h. In frozen semen stored for 6 and 18 mo corresponding values were 12.2 and 8.3 microliter. Packaging methods did not have a significant effect on oxygen uptake, but package interacted with storage. Egg yolk-citrate extender supported greater progressive spermatoal motility than did promine-D. Extender interacted with storage for all criteria. Visible light radiation reduced progressive spermatozoal motility from 40.2 to 38.0% and oxygen uptake from 11.8 to 10.8 microliter per 10(8) cells per h. Light interacted with storage time. Correlations between all criteria and storage times were not important practically.