To what extent does photoperiod affect cattle reproduction? Clinical perspectives of melatonin administration

The seasonality of reproduction in most mammals is dictated by photoperiod, temperature and nutrition. Melatonin, mainly synthesized in the pineal gland, is generally accepted as the active mediator of photoperiod responses including reproduction. While non-pregnant heifers and cows show continuous sexual activity and are therefore not seasonal breeders, it has been suggested that photo-periodicity may influence the appearance of puberty in heifers and the onset of parturition. Further, the light/dark ratio may influence endocrine patterns of gestation and a shorter light period correlates with the incidence of twin pregnancies. This review considers specific aspects of the effects of photoperiod and melatonin on reproduction in dairy cattle and discusses the clinical applications of melatonin

Clinical overview of luteal deficiency in dairy cattle

Luteal deficiency is defined as reduced progesterone (P4) steroidogenesis by the corpus luteum (CL), either in the amount or duration, or both. This work provides a clinical overview of the current understanding of luteal deficiency and its association with low fertility in dairy cows. Low plasma P4 concentrations during the luteal phase post-artificial insemination (AI) are associated with lower conception rates. Treatments post-AI with P4, gonadotropin-releasing hormone (GnRH) or human chorionic gonadotropin (hCG) improve fertility in some conditions. Sub-luteal function during the late embryonic period (at pregnancy diagnosis, i.e., 28–34 days post-AI), is just one factor among other factors associated with pregnancy loss. Treatment with P4 in cows with one CL favors pregnancy maintenance, while GnRH treatment does the same in cows carrying twins. The diagnosis of sub-luteal function can be made clinically on the basis of plasma or milk P4 concentrations. Automated in-line milk P4 analysis systems to diagnose luteal activity emerge as a very interesting tool in dairy herds. Monitoring plasma or milk P4 concentrations with the help of Doppler ultrasonography to assess the CL function would allow individualizing the luteal phase support

Epidemiological aspects of factors affecting reproductive efficiency in high producing dairy cows

Descripció del recurs: el 27 d'agost de 2008Consultable des del TDXTítol obtingut de la portada digitalitzadaEl rápido progreso mundial en manejo y genética en vacas lecheras de alta producción, ha culminado con un aumento de animales por rebaño. A pesar de este aumento, la fertilidad y la eficacia reproductiva de estos animales ha ido disminuyendo desde los años 80. El manejo también ha sufrido importantes cambios estos años, al igual que el ambiente donde se encuentran las vacas de alta producción. La temperatura de confort de vacas lecheras se encuentra entre 5 y 25ºC, y por este motivo se puede pensar que el estrés por calor no sólo se producirá en zonas tropicales, si no que se expande globalmente y tiene una gran importancia para la ganadería. %&/El objetivo de esta tesis es estudiar factores de manejo y ambientales que puedan afectar a la fertilidad y a perdidas fetales iniciales en vacas altamente productoras en el Noreste español. Los estudios se realizaron en la zona del Segriá y los datos meteorológicos se obtuvieron de una estación situada a menos de 6 km de las granjas. En el primer estudio realizado se determinó que el índice de temperatura-humedad (THI) es mejor predictor para las perdidas fetales iniciales que la temperatura sola. Además, el período de 21-30 días postinseminación se determinó como un período crítico para la gestación. En el segundo estudio, las vacas altamente productoras fueron las que presentaron mayor fertilidad, evidenciando que el efecto negativo de la producción lechera sobre la eficacia reproductiva tiene que ser revisado. En el tercer estudio, los efectos de manejo fueron de gran importancia para la fertilidad de rebaños lecheros: el número de ordeños, los inseminadores y el toro. Posiblemente cada granja tiene que revisar periódicamente los toros utilizados, y entrenar a los técnicos inseminadotes correctamente. En el cuarto estudio se demostró que factores ambientales alrededor del periodo de inseminación tienen gran efecto sobre la fertilidad. No se pudo demostrar si el THI era mejor predictor para la pérdida de fertilidad que la temperatura sola. Finalmente en el quinto estudio se puso de manifiesto algunos marcadores de riesgo para la disminución de la fertilidad en granjas lecheras de alta producción, como los quistes ováricos y la baja producción de leche. En conclusión, para poder aumentar la eficacia reproductiva de granjas lecheras altamente productoras es necesario llevar a cabo un control periódico de los datos de cada rebaño, y monitorizar correctamente los animales. Además, el ambiente y el manejo se deben mejorar en este tipo de animales si se quiere seguir aumentando la producción lechera como hasta ahora.The rapid worldwide progress in management and genetics of dairy herds has culminated in an increase of milk production and number of animals per herd. But despite this rapid progress, reproductive performance and reproductive disorders of high producing dairy has suffered a dramatic decrease and increase, respectively, since the mid 1980's. Management practices have also suffered significant changes during the last decades besides an increase in milk production. The most comfortable temperatures for dairy cows ranged from 5 to 25ºC. Therefore, heat stress in not confined in tropical regions of the world and has a great impact on farm economy. The main objectives of this thesis were to study environmental and management factors that affect fertility and pregnancy losses in high producing dairy cattle in northeastern Spain, a country with a seasonal warm weather. The studies were performed in high producing dairy herds in Lleida. Climatic data were obtained from a meteorological station located less than 6 km from the herds and management data were recorded in each herd. In the first study results indicated that temperature humidity index during the periimplantational period and warm season were a risk factor for pregnancy losses. In the second, cows that get pregnant before 90 days postpartum were those who produce more milk on 50 days postpartum. Management practices of these herds offset the negative effects of milk production. In the third, management practices demonstrated to be an important factor for conception rate. Three times per day milking, inseminating bull and AI technician were a risk factors for infertility. In the fourth, environment proved to be directly affecting conception rate especially around AI period. In the fifth, monthly summary records provide risk markers for fertility: low milk production and ovarian cysts. In conclusion, to increase reproductive performance of high producing dairy herds, it is necessary to monitor their status periodically. Moreover, management and environmental factors of dairy herds have a great importance on economic success of high producing dairy farms

Unilateral twin pregnancy: a non-infectious factor required for the etiological diagnosis of abortion in dairy herds

Twin pregnancies are classified into bilateral (one fetus in each uterine horn: 44%) and unilateral (both fetuses in the same uterine horn, right or left: 56%). The incidence of abortion during mid- to late gestation is approximately 1% in cows carrying bilateral twins and more than 40% in cows carrying unilateral twins. In this period, abortion seems most commonly associated with infectious agents. However, although this imbalanced abortion rate may imply that unilateral twin pregnancy is a non-infectious abortion factor, few available data can describe the cause of abortions in twin pregnancies. The current findings suggest that unilateral twin pregnancy is a non-infectious factor required for the etiological diagnosis of abortion in dairy herds

Inducing Ovulation with hCG Improves Fertility Outcomes of Co-Dominant Follicle Drainage to Avoid Twin Pregnancy in Dairy Cows

Twin pregnancies are undesirable in dairy cattle as they dramatically compromise cow lifespan and, consequently, herd economy. Clinical problems in cows arise from the time of pregnancy diagnosis to pregnancy loss, abortion, or parturition. The drainage of co-dominant follicles in cows with two or more follicles at insemination prevents twin pregnancy. The objective of this study was to compare the effectiveness of draining the smaller of two follicles through a simplified maneuver not requiring ultrasonography in cows in their third or more lactation, and then inducing ovulation immediately before artificial insemination (AI) with GnRH or human chorionic gonadotrophin (hCG). Animals were monitored by ultrasound at AI and randomly assigned to the groups: follicular drainage and treatment with GnRH (Deph; n = 60), follicular drainage and treatment with hCG (hCG; n = 60), and non-drainage (ND; n = 60) as control cows. On the basis of odds ratios, cows treated with hCG were 2.1 times more likely to become pregnant than control animals. Our results reveal the efficacy of hCG treatment at AI in cows with two follicles of pre-ovulatory size subjected to a simple follicular drainage procedure.This study received financial support from the procedure “01.02.01 de Transferència Tecnològica del Programa de desenvolupament rural de Catalunya 2014–2020” (Number 19005)