Interval from Oestrus to Ovulation in Dairy Cows-A Key Factor for Insemination Time: A Review.

This review describes the oestrus-to-ovulation interval, the possibility of predicting the time of ovulation, and the optimum time for insemination relative to oestrus in dairy cows. The duration of oestrus in dairy cows is approximately 8-20 h, with differences possibly related to the methods of oestrus detection and the frequency of observations. Most cows ovulate approximately 24-33 h after the onset of oestrus and 15-22 h after the end of oestrus. The interval from the preovulatory luteinising hormone (LH) surge to ovulation is approximately 4-30 h. Ovulation occurs when follicle diameter averages 18-20 mm. When it is possible to correctly determine the beginning of oestrus, artificial insemination can be performed utilizing the "a.m.-p.m. rule", and only one insemination may be applied. In cows with too long or too short oestrus-to-ovulation intervals, fertility can be compromised. One important factor that can alter the oestrus-to-ovulation interval is acute or chronic heat stress during the warm season. When there is a risk that insemination may occur too early or too late with respect to the time of ovulation, GnRH administration can be considered.

Use and adequacy of non-pregnancy diagnosis in cow. Which future?

In cattle, early detection of gestation is very important from an economic and management point of view in all types of farming. However, due to the poor efficiency of oestrous detection, it is essential to determine non-pregnant cows as early as possible, in order to minimize the inter-insemination interval, thus de facto, reducing herd open days. Direct and indirect gestation diagnostic methods have been developed with the aim of improving the reproductive performance of the herd. Today, the most accurate method for making an early diagnosis of gestation from 28 to 30 days post-insemination is B-mode ultrasound. In recent years, indirect methods have included techniques that allow non-pregnant cows to be identified with a minimum margin of error, the most widely utilized of which is the colour Doppler. This technique is rapidly becoming established for the diagnosis of non-pregnancy, which allows for the identification of non-pregnant animals earlier compared with the pregnancy diagnosis. Some limitations of this technique in dairy cow have been presented.

Effect of pegbovigrastim on clinical mastitis and uterine disease during a full lactation in grazing dairy cows.

In this randomized controlled trial on four commercial grazing dairy farms, we investigated whether pegbovigrastim (PEG) treatment affects clinical mastitis (CM) and uterine disease (i.e. retained placenta (RP), metritis and endometritis) occurrence during a full lactation. The association of prepartum body condition score and prepartum non-esterified fatty acid (NEFA) concentration with disease occurrence was also evaluated. Holstein cows were randomly assigned to one of two treatments: first PEG dose approximately 7 d before the expected calving date and a second dose within 24 h after calving (PEG) compared to untreated controls (Control). In total, 2,153 animals were included in the study: 733 primiparous cows (Control = 391, PEG = 342) and 1420 multiparous cows (Control = 723, PEG = 697). Treatment effects were evaluated with generalized linear mixed models and Cox's proportional hazard models. Treatment with PEG reduced the occurrence of a first case of CM during the first 30 days in milk (DIM) by 24.6% and reduced the hazard of a first case and the rate of total cases of CM during the full lactation. All PEG treatment effects were independent of parity. Prepartum body condition score interacted with PEG treatment: in over-conditioned cows, PEG reduced the occurrence of a first case of CM during the first 30 DIM by 49.5%. The hazard analysis of a first case of CM during the full lactation suggested that the preventive effect of PEG disappeared with increasing DIM. Treatment with PEG did not affect the occurrence of RP or metritis. Pegbovigrastim treated cows with metritis subsequently showed a reduced occurrence of endometritis compared to control cows with metritis. Pegbovigrastim reduces the occurrence of CM particularly in cows at risk of elevated lipid mobilization, and PEG ameliorates the uterine healing process in cows that experienced metritis.

Ultrasonography of the bovine female genital tract.

The objective of this article is to help interested readers learn to use ultrasound for female bovine reproductive tract examinations. The first section discusses practical issues for using ultrasound in the field, such as animal restraint and preparation, type of ultrasound units available, and scanning technique. The second section reviews ultrasound diagnosis of various ovarian structures. The third section explores uterine changes during the estrous cycle, in addition to uterine pathologic conditions. The fourth section covers early pregnancy, twinning, embryonic and fetal viability, and fetal anomalies. The final section considers the use of ultrasound with advanced techniques, such as embryo transfer, in vitro fertilization, and color Doppler technology, and as a complement tool in reproduction synchronization protocols for dairy cattle.

Ultrasound imaging of the bull reproductive tract: an important field of expertise for veterinarians.

Diagnosing male reproductive system pathologies can often be frustrating because of the challenge involved in precisely determining their site, severity, and prognosis. The introduction of complementary ultrasonographic examination enables clinicians to address these important questions. This procedure should be performed not only on bulls destined to artificial insemination, but on all farm bulls. The examination is easy to perform with a versatile ultrasonographic unit designed for bovine theriogenology. To recognize abnormal tissues, however, the operator must have an excellent knowledge of the ultrasonographic anatomy of the reproductive system. This article discusses the basis of ultrasound technique for male reproductive tract examination. Ultrasound evaluation of physiologic and pathologic conditions of external and internal reproduction organs is proposed.