Strategies to extend sperm cell lifespan and improve fertility outcomes in dairy heifers

Abstract

The efficiency of the reproductive techniques in dairy heifer is fundamental for the profitability and production increase, determining the age of first birth and the days that the animal will not be produced. For this, efficiency can be reached with the use of timed artificial insemination (AI) protocols in heifers to optimize the time to better plan of the stage to be followed. However, 25 % of heifer start the estrus in 24h after insemination having, thus, a decrease in rate conception in animals that ovulate after this period. But the difference in AI in this period has a factor the duration semen lifespan inside of reproductive tract of this heifers, prevented that it is viable from the first day of ovulation until the last day that was induced with GnRH. Thereby, the strategy for extending the semen lifespan inside of female reproductive tract, which permits TAI to be performed after the second GnRH injection. There is a decrease of 25% of animals loss. Although in vitro results suggest that Semen Extender 1 (SE1) and Semen Extender 2 (SE2) developed by IMV Technologies are capable to prolong availability of fertile semen after insemination, validation of such outcomes in vivo are lacking. Therefore, two experiments were proposed. The Pilot Study will evaluate of effects of the semen processing over rate and pregnancy loss, the hypotheses is: the incorporation of SE1 and SE2 during semen processing will not decrease the pregnancy rate for TAI or increase the risk of pregnancy loss in dairy heifers subjected to timed AI. For this, non-lactating Holstein heifers with 13 months of age will be divided in 4 groups with 85 animal each. The first group conventional will consist of unwashed semen without additional treatment; second group: conventional semen washed without additional treatment; third group: conventional semen treated with SE1; and the last treatment: conventional semen treated with SE2. All the heifers will be submitted to a protocol receive an injection of GnRH and an intravaginal progesterone device (d-8), that will be removed 5 d later and heifers will be treated with two injections of PGF2± 24 h apart (d -3 and -2). All heifers will receive timed AI and a second injection of GnRH 72 h after the first injection of PGF2± (d 0). Pregnancy will be diagnosed by transrectal ultrasonography 35 d after AI and pregnant heifers will be re-examined on d 63 after AI. The Main Study seeks to analyze the effects of semen extenders on the sperms cell lifespan end the fertility result. The hypotheses of this study is that the incorporation of SE1 and SE2 during semen processing will increase pregnancy rate in dairy heifers submitted the TAI modified protocol. The objective of this study is to evaluate the effects of treating semen with SE1 and SE2 over risk of pregnancy loss in dairy heifers. For this the animal will be submitted to the following experimental groups: timed AI on d 1 using conventional semen without additional treatment; timed AI on d 0 using conventional semen without additional treatment; timed AI on d 0 conventional semen treated with SE1; timed AI on d 0 conventional semen treated with SE2, each treatment will have 200 animals. All heifers will be subjected to a modified protocol. Each animal will receive an injection of GnRH and an intravaginal progesterone device (d-7), that will be removed 5 d later and heifers will be treated with two injections of PGF2± 24 h apart (d -2 and -1). All heifers will receive timed AI 48 h after the first injection of PGF2± (d 0) second injection of GnRH 24 h later (d 1). Pregnancy will be diagnosed by transrectal ultrasonography 35 d after AI and pregnant heifers will be re-examined on d 63 after AI. (AU)