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Pregnancy rates in mares following a single insemination with a low number of spermatozoa into the tip of the uterine horn
Thefiogeno~gy
395
i S e x i n g / Sex Ratio
PREGNANCY RATES IN MARES FOLLOWING A SINGLE INSEMINATION WITH A LOW NUMBER OF SPERMATOZOA INTO THE TIP OF THE UTERINE HORN
B.R.Buchanan, 1 P,M.McCue, 1 E.L.Squires, l G.E.Seidel Jr, 1 and J.J.Fleury2 XAnimal Reproduction and Biotectmology Laboratory, Colorado State University, Fort Collins, CO, 80523 USA 2Faculdade de Medicina Veterinaria Octavio Bastos-Sao Paulo-Brazil
Insemination with a low number of spermatozoa is necessary when semen is limited or when using sorted sexed semen. Therefore, a study was done to compare pregnancy rates of mares inseminated on a single occasion with 500, 25, or 5 x 106 progressively motile spermatozoa from 1 of 2 stallions. Sixty-one mares were randomly assigned to 1 of 3 treatments: Group 1 (n=20) were inseminated into the uterine body with 500 x 106 sperm (controls). Group 2 (n=21) and group 3 (n=20) were inseminated in the tip of the uterine horn ipsilateral to the preovulatory follicle with 25 or 5 x 106 sperm, respectively. Mares were administered cloprostenol (250pg i.m.) to induce luteolysis and monitored by ultrasonography every other day until a follicle _>30ram was detected, and then daily until ovulation was detected. GnRH (deslorelin 2.2 rag, Ovuplant®, Fort Dodge, IA) was administered when the dominant follicle was _>35ram. Mares were inseminated 34 (n=29) or 40 hours (n=32) after GnRI-I. Data from 22 mare cycles were excluded because they either oxallated prior to planned insemination (n=l 1), did not ovaxlate (n=3), or ovulated > 4 days after GnRI-I administration (n=8). Semen was collected and immediately diluted with a skim milk extender (EZ-Mixin, OF, Animal Reproduction Systems, Chino, CA) to either 25 x 106 or 5 x 106 motile sperm/ml. Mares were inseminated as described in Table 1. Mares receiving 1 ml were inseminated with a flexible plastic artificial insemination pipette (IMV, France), while mares receiving 0.2 ml were inseminated using a disposable implant gun (Veterinary Concepts, Green Valley, WI) containing a 0.5 ml straw. Different insemination pipettes were used to optimize delivery of the two different volumes. The location of pipettes within the uterus was confirmed by transrectal ultmsonography prior to semen deposition. Pregnancy was determined by ultrasonography at 16 days after ovulation. Pregnancy rates were not different between stallions (P>0.05), so results from the two stallions were combined (Table 1). There was no difference in pregnancy rates between mares bred 34 vs. 40 hours after GnRH administration 19/29 (65%) and 18/32 (56%), respectively (P>0.1). Pregnancy rates decreased as the number of motile spermatozoa inseminated decreased. Breeding mares with 25 x 106 progressively motile sperm into the tip of the uterine horn resulted in a pregnancy rate of 57%. Table 1. Day 16 Pregnancy Rates from a Single Insemination No. of Motile Sperm No. Pregnant/No. Bred % Pregnant 500 x 106 in 20 ml 18/20 (90%) a 25 x 106 in 1 ml 5 x 106in 1 ml 5 x 106 in0.2 ml
12/21 3/10 4/10
a,b Values with different superscripts differ (P<0.05).
(57%) b (30%) b (40%) b
395
i S e x i n g / Sex Ratio
PREGNANCY RATES IN MARES FOLLOWING A SINGLE INSEMINATION WITH A LOW NUMBER OF SPERMATOZOA INTO THE TIP OF THE UTERINE HORN
B.R.Buchanan, 1 P,M.McCue, 1 E.L.Squires, l G.E.Seidel Jr, 1 and J.J.Fleury2 XAnimal Reproduction and Biotectmology Laboratory, Colorado State University, Fort Collins, CO, 80523 USA 2Faculdade de Medicina Veterinaria Octavio Bastos-Sao Paulo-Brazil
Insemination with a low number of spermatozoa is necessary when semen is limited or when using sorted sexed semen. Therefore, a study was done to compare pregnancy rates of mares inseminated on a single occasion with 500, 25, or 5 x 106 progressively motile spermatozoa from 1 of 2 stallions. Sixty-one mares were randomly assigned to 1 of 3 treatments: Group 1 (n=20) were inseminated into the uterine body with 500 x 106 sperm (controls). Group 2 (n=21) and group 3 (n=20) were inseminated in the tip of the uterine horn ipsilateral to the preovulatory follicle with 25 or 5 x 106 sperm, respectively. Mares were administered cloprostenol (250pg i.m.) to induce luteolysis and monitored by ultrasonography every other day until a follicle _>30ram was detected, and then daily until ovulation was detected. GnRH (deslorelin 2.2 rag, Ovuplant®, Fort Dodge, IA) was administered when the dominant follicle was _>35ram. Mares were inseminated 34 (n=29) or 40 hours (n=32) after GnRI-I. Data from 22 mare cycles were excluded because they either oxallated prior to planned insemination (n=l 1), did not ovaxlate (n=3), or ovulated > 4 days after GnRI-I administration (n=8). Semen was collected and immediately diluted with a skim milk extender (EZ-Mixin, OF, Animal Reproduction Systems, Chino, CA) to either 25 x 106 or 5 x 106 motile sperm/ml. Mares were inseminated as described in Table 1. Mares receiving 1 ml were inseminated with a flexible plastic artificial insemination pipette (IMV, France), while mares receiving 0.2 ml were inseminated using a disposable implant gun (Veterinary Concepts, Green Valley, WI) containing a 0.5 ml straw. Different insemination pipettes were used to optimize delivery of the two different volumes. The location of pipettes within the uterus was confirmed by transrectal ultmsonography prior to semen deposition. Pregnancy was determined by ultrasonography at 16 days after ovulation. Pregnancy rates were not different between stallions (P>0.05), so results from the two stallions were combined (Table 1). There was no difference in pregnancy rates between mares bred 34 vs. 40 hours after GnRH administration 19/29 (65%) and 18/32 (56%), respectively (P>0.1). Pregnancy rates decreased as the number of motile spermatozoa inseminated decreased. Breeding mares with 25 x 106 progressively motile sperm into the tip of the uterine horn resulted in a pregnancy rate of 57%. Table 1. Day 16 Pregnancy Rates from a Single Insemination No. of Motile Sperm No. Pregnant/No. Bred % Pregnant 500 x 106 in 20 ml 18/20 (90%) a 25 x 106 in 1 ml 5 x 106in 1 ml 5 x 106 in0.2 ml
12/21 3/10 4/10
a,b Values with different superscripts differ (P<0.05).
(57%) b (30%) b (40%) b