Frozen storage of ram semen II. Causes of low fertility after cervical insemination and methods of improvement

Fertilization rate and embryonic mortality were assessed in 636 ewes inseminated in each uterine horn with 50 x 10(6) frozen spermatozoa from four control rams and from four rams submitted to a moderate (1.4-2.2 degrees C), but repeated, intermittent (16 h/day for 21 consecutive days) increase in their subcutaneous scrotal temperature by means of scrotal insulation. Pregnancy was assessed twice in each ewe from concentration of progesterone in blood plasma at 17 days and by ultrasound at 65 days after insemination. No differences were observed in the pregnancy rate at 17 days between ewes inseminated with semen collected from control rams (56.0, 65.2, 66.7 and 60.3%) and from heated rams (60.6, 71.8, 63.6 and 48.2%) before or after 4, 15 and 21 days of heating, respectively. In contrast, the rate of embryonic mortality between 17 and 65 days after insemination was significantly higher at days 4, 15 and 21 in the heated rams (78.7, 78.6 and 93%) than in the control rams (55, 59 and 65.7%). These results indicate that an intermittent slight, but repeated, increase in the subcutaneous scrotal temperature could induce a significant increase in the embryonic mortality rate. As these changes were apparent on day 4 of heating, an effect must have occurred on sperm stored in the epididymis.

https://rep.bioscientifica.com/downloadpdf/journals/rep/94/2/jrf_94_2_007.pdf

Effects of heating the testes and epididymides of rams by scrotal insulation on fertility and embryonic mortality in ewes inseminated with frozen semen.

Artificial insemination of ewes with frozen-thawed semen at a synchronized oestrus. 1. Effect of time of onset of oestrus, ovulation and insemination on fertility

A review on reproduction in South American camelids.

The fertility of ewes after artificial insemination and the relationship between fertility and motility characteristics assessed by a computerized motility analysis system were examined with ram semen frozen in diluents reported to improve postthaw motility. The percentages of motile and progressive spermatozoa were better when frozen in proline- or glycine betaine-containing or HEPES-based, rather than Tris-based, diluents (P < 0.01). The fertility of spermatozoa frozen in diluents containing proline or glycine betaine was slightly reduced, whereas when both compatible solutes were present, the reduction was more pronounced, in comparison with semen frozen in Tris- or HEPES-based diluents (9.5 versus 71.1 and 66.6%; P < 0.01). Fertility of frozen-thawed spermatozoa was higher after laparoscopic insemination than after cervical or transcervical insemination (P < 0.01). Similarly, higher fertility was obtained after cervical insemination with fresh than with frozen-thawed semen (32.4 versus 11.3%; P < 0.01). Furthermore, loss of embryos was lower after laparoscopic insemination of ewes with semen frozen in a Tris diluent than with semen frozen in proline diluents, in glycine betaine diluents, or in proline-plus-glycine betaine diluents (0.0 versus 26.0, 38.5, and 60.0%; P < 0.001). A wide variation in the postthaw percentage of motile (31.6-59.7%) and progressive (22.6-43.1%) spermatozoa and in the fertility of spermatozoa from individual rams was also observed after laparoscopic (29.2-59.7%) or cervical insemination (8.7-30.5%). Postthaw motility results from immediately after thawing and fertility results from experiments where intrauterine insemination was performed with semen frozen in proline- or glycine betaine-containing or HEPES- or Tris-based diluents were pooled and subjected to a pairwise correlation procedure. The correlation analysis showed relationships between some of the motility characteristics (P < 0.01), but there were no relationships between the motility characteristics and fertility.

Fertility and Its Relationship to Motility Characteristics of Spermatozoa in Ewes After Cervical, Transcervical, and Intrauterine Insemination With Frozen‐Thawed Ram Semen

There have been a number of reports on the frozen storage of ram semen, and artificial insemination with frozen semen has been performed on an experimental basis in several countries. Intensive laboratory studies led to considerable progress regarding the freezing and thawing procedures (Salamon & Visser, 1972; Colas, 1975). However, fertility following insemination tends to be considerably lower than for fresh or chilled semen (Maxwell et al. 1980).

Intra-uterine insemination of ewes with frozen semen

In an experiment involving the artificial insemination of 312 Merino ewes, fertilization, early (18 day), and late (100 day) pregnancy rates were examined after intrauterine insemination with frozen semen using a laparoscope. Oestrus was synchronized in ewes by progestagen sponge/PMSG treatment. After cervical insemination of fresh semen (control) 55 hrs after sponge removal, the fertilization, early and late pregnancy rates were 24/30, 37/46 and 33/46 respectively. Following intrauterine insemination of frozen-thawed semen at 24, 36, 48 and 60 hr after sponge removal, fertilized eggs were recovered in 7/27, 12/22, 17/25 and 19/25 ewes; the early pregnancy rates were 13/34, 18/34, 20/34 and 23/35; and the late pregnancy rates were 3/34, 6/34, 17/34 and 19/35 for the respective insemination times.

Fertility of ewes after intrauterine insemination with frozen semen.

One hundred and fifty ewes with lifetime records of ovulation rate and lambing were divided into two groups on the basis of age, live weight and reproduction index (calculated from reproductive performance data). Both groups were synchronised in oestrus with progestagen sponges inserted for 14 days. At sponge removal one group received no PMSG while the other group received 400 i.u. PMSG. Eight days after sponge removal, the ovaries of all ewes were examined at laparoscopy.

LG Butler

Papers

Intra-uterine insemination of ewes with frozen semen

Fertility of ewes after intrauterine insemination with frozen semen.

PMSG response in ewes of different breeding value for reproductive rate as an aid to selection.