Sperm survival and transport in the female reproductive tract.
ABSTRACT Fertilization failure, mostly due to absence of sperm in the oviducts, is a major cause of reproductive inefficiency of farm animals. Sperm may be transported to the oviducts of cattle and sheep within a few minutes after mating or insemination, but these sperm probably fertilize few ova. Slower transport, with establishment of sperm populations in each segment of the reproductive tract, requires a few to several hours. In swine, sperm capable of fertilizing ova reach the oviducts in less than 1 h. Smooth muscle contractions of the reproductive tract, ciliary beats, fluid currents, and flagellar activity of sperm are primary mechanisms of sperm transport. Sperm become hyperactive in the oviducts in association with capacitation. Most sperm in an inseminate drain from the female reproductive tract within a few minutes or hours after insemination; remaining sperm are removed from the tract by slower drainage or phagocytosis. Sperm survival and transport in estrous ewes is reduced drastically by pastures with high estrogen content and by regulating estrus with progestogen or prostaglandin F2 alpha. The cervix is the initial site of inhibition of sperm transport in ewes, and endocrine imbalances probably are the basis of inhibition. Sperm transport problems generally are associated with immobilization and death of sperm in the uterus and anterior segments of the cervix within 2 h after mating. After gilts are inseminated with frozen-thawed semen, relatively few sperm are retained in the reproductive tract, apparently accounting for lowered fertilization rates. Sperm transport has been improved by adding to semen or administering to females such compounds as prostaglandin F2 alpha, oxytocin, estradiol, phenylephrine, or ergonovine. Estradiol, prostaglandin F2 alpha, phenylephrine, and ergonovine administered to rabbits at insemination each increased fertilization rates.
- SourceAvailable from: Manoel F de Sá Filho[Show abstract] [Hide abstract]
ABSTRACT: The abilities of two different estradiol esters to induce ovulation in a timed AI (TAI) synchronization protocol in suckled Bos indicus cows were evaluated. In Experiment 1 (synchrony of ovulation), 31 cows were submitted to an estradiol/progestin-based synchronization protocol (Day 0) and randomly assigned to one of three treatments at the time of progestin removal on Day 8: 0.5 or 1.0 mg of estradiol cypionate (EC) at that time or 1.0 mg of estradiol benzoate (EB) 24 h later (Day 9). To determine the timing of ovulation, ultrasound examinations were performed every 12 h from ear implant removal to 96 h after the removal. Orthogonal comparisons were performed to determine the effects of estradiol ester and the effects of the dose of EC on reproductive parameters. Although neither the E2 ester (P = 0.83) nor the dose of EC (P = 0.55) affected the ovulation rate, the interval from progestin removal to ovulation was longer (P = 0.04) in EC-treated cows (1.0 mg EC = 71.1 ± 3.6 and 0.5 mg EC = 78.0 ± 3.5) than EB-treated cows (EB = 66.0 ± 2.3) was detected. Ovulation in 0.5-mg-EC-treated cows was less synchronous than that in 1.0-mg-EC-treated cows (distribution curves compared using kurtosis). In Experiment 2 (pregnancy per AI; P/AI), 660 cows at two different locations received the same synchronization protocol (n = 361 at Farm A and n = 299 at Farm B) and were treated with estradiol esters as in Experiment 1 [0.5 mg EC (n = 220) or 1.0 mg EC (n = 219) at the time of progestin removal or 1.0 mg EB (n = 221) 24 h later]. The cows were inseminated 54 to 56 h after progestin removal. As applied in the Experiment 1, orthogonal comparisons were performed to evaluate the effect of estradiol ester and the dose of EC on P/AI. Although the type of estradiol ester used did not affect the P/AI (P = 0.57; EB - 43.0% vs. EC - 44.6%), the P/AI was higher (P = 0.03) in cows treated with 1.0 mg EC (55.7%) than in those treated with 0.5 mg EC (38.6%). In summary, the administration of 0.5 mg EC at the time of progestin removal altered the distribution of ovulation and resulted in a lower P/AI when compared with the use of 1.0 mg EC in suckled Bos indicus cows. However, the P/AI following the administration of 1.0 mg EC at the time of progestin removal did not differ from that after the administration of 1.0 mg EB 24 h later.Animal Reproduction Science 10/2014; · 1.58 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The primary objective was to determine if low doses of PGF2α (dinoprost) given intramuscularly (im) concurrent with timed artificial insemination (TAI) would improve conception rates in dairy cattle. A secondary objective was to determine if body condition score (BCS) and parity would influence conception rates, either independently or in interaction with PGF2α treatment. In experiment I, 307 lactating Holstein cows were randomly assigned to receive either 5-mg PGF2α im (PGF2α treated, n = 154) or 0-mg PGF2α (control, n = 153) at TAI (Day 0). Blood samples were obtained on Days −10, −3, 0, and 7 to determine plasma progesterone (P4) concentrations. Pregnancy was confirmed 30 to 32 days after insemination by transrectal ultrasonography. In experiment II, 451 cows were randomly assigned to receive either 10-mg PGF2α im (PGF2α treated, n = 226) or 0-mg PGF2α (control, n = 225) at TAI, and pregnancy was confirmed 45 to 50 days after TAI by palpation per rectum. Pregnancy data were analyzed by CATMOD (SAS). In experiment I, PGF2α treatment, BCS, and parity did not affect conception rate (35.7% vs. 37.0% for PGF2α treated vs. control; P > 0.05). However, in experiment II, conception rates were higher in cows given 10-mg PGF2α than those in control cows (45.8% vs. 36.0%; P < 0.05), in cows with high BCS than in cows with low BCS (52.1% vs. 30.4%; P < 0.01), and in primiparous than in multiparous cows (47.6% vs. 34.4%; P < 0.01), but their interaction with PGF2α treatment did not affect conception rates. In summary, 5 mg of PGF2α given im concurrent with TAI failed to enhance conception rate in lactating dairy cows, whereas 10 mg of PGF2α significantly increased conception rateTheriogenology 10/2014; · 1.85 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: INTRODUCCIÓN La industria lechera estadounidense de este siglo continua cambiando hacia un actividad desarrollada por un menor número de tambos y con un incremento en la cantidad de vacas por establecimiento (19). El manejo de una mayor cantidad de vacas por persona es cada vez más frecuente, con un aumento en la exigencia puesta sobre las vacas a medida que son llevadas desde un sistema natural pastoril hacia el confinamiento. La detección de los celos en vacas en lactancia en confinamiento es un gran desafío, debido a la menor opor-tunidad de interacción vaca-vaca, por el espacio limitado y por el impacto negativo del tipo de superficie (piso de concreto) sobre la expresión del celo. El aumento de la frecuencia de ordeño eleva el tiempo de traslado de los animales desde los corrales hacia los patios de alimentación, lo que reduce el tiempo destinado al descanso y a la alimentación. Todos estos factores impactan sobre las tasas de concepción, que han declinado durante los últimos 20 años, no sólo en los EE.UU. (19). Incluso en el Reino Unido, donde las vacas producen menos leche, las tasas de concepción han bajado alrededor de un 1% por año desde 1983 (30). El objetivo de esta presentación es identi-ficar y describir los factores interrelacionados que determinan las tasas de preñez de los rodeos.