Reproductive wastage in the androstenedione-immune ewe

Abstract

An experiment was carried out using 320 adult Merino ewes to examine the effects of immunization against an androstenedione human serum albumin conjugate (Fecundin) on ovulation rate, fertilization rate and embryo viability at days 2, 9 and 13-14 after fertilization. The ovulation rate of immunized ewes (2.19 +/- 0.06) was greater (P < 0.001) than that of control ewes (1.43 +/- 0.04). The recovery rate of embryos or of unfertilized oocytes on day 2 was reduced in immunized ewes, but fertilization rate of recovered oocytes was unaffected by immunization. The mean number of normal embryos per ewe pregnant (prolificacy) was higher and the proportion of ewes pregnant (fertility) was lower in immunized than in the control ewes. The distribution of the number of cells per embryo showed no differences in developmental age over the period of sampling, the majority of embryos at this time being at the two- to four-cell stage of development. At day 9 of pregnancy, blastocyst recovery rates were lower in immunized than in control ewes. About 90% of blastocysts recovered were developing normally in control ewes compared with 64% in immunized ewes. The majority of blastocysts recovered on day 9 had hatched from the zona pellucida prior to recovery (mean values were 94.2% and 87.8% for control and immunized groups, respectively). In control ewes single blastocysts were larger than twin blastocysts, but for the immunized ewes this difference was not significant. Both single blastocysts (P < 0.01) and twin blastocysts (P < 0.05) from immunized ewes were smaller than those from control ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunization against androstenedione to improve the reproductive efficiency in Nilagiri and Sandyno ewes

“…There was no significant difference in tupping percentage among the treatment groups. Scaramuzzi et al (1993) and Crocker et al (2003) observed no difference in tupping percentage among the treatment groups similar to the present study. Immunization of ewes against androstenedione also had no significant effect on lambing percentage which was in agreement with the findings of Philipon and Driancourt (1987) and Crocker et al (2003).…”

Effects of immunization against androstenedione or bone morphogenetic protein 15 (BMP15) on reproductive performance in sheep1

“…Previous studies examining the effects of immunization against androstenedione on conception rate, embryo survival, and lamb performance have been inconsistent but highlight the potential for negative effects of the vaccines on these traits (Boland et al, 1986;Cameron et al, 1988;Croker et al, 1988;Scaramuzzi et al, 1993). Expression of the androgen receptor is widespread in the sheep ovary, but it is unclear if androgens may have a direct effect on the oocyte, as receptors have been noted in oocytes using immunohistochemistry, but no mRNA for androgen receptor could be detected with in situ hybridization (Juengel et al, 2006).…”

“…However, similar to what was seen with the BMP15 vaccine, the effects of immunization against androstenedione appear primarily limited to alterations in ovulation rate as no differences were observed in conception rate or partial failure of multiple ovulations. Previous studies have shown detrimental effects of immunization against androstenedione on conception rate and early development of the embryo (Boland et al, 1986;Cameron et al, 1988;Scaramuzzi et al, 1993). However, controlling the timing of mating after the booster immunization appears to be a key element in minimizing these detrimental effects as ewes mating 14 d after the booster immunization were more severely affected than those mated 25 d (Boland et al, 1986).…”