Background: Timed artificial insemination (TAI) as part of a controlled breeding programme is a reproductive strategy that eliminates the requirement for oestrus detection, guarantees the submission of enrolled cows and attempts to optimise the timing of insemination relative to ovulation. However, the success of TAI requires careful cow selection, diligent herd management and the selection of an appropriate synchronisation protocol.Aim of the article: This article, the first in a two‐part series, outlines the key ovarian follicular wave dynamics in the bovine oestrous cycle and the key goals of any synchronisation protocol. It describes the most commonly used drugs, their actions and how they can be combined into effective synchronisation protocols. The second part of the series, to be published in a subsequent issue of In Practice, discusses how to implement controlled breeding strategies on farms and considers factors aside from the TAI protocol that are essential for the success of any programme.
In autumn calving dairy herds, treatment of cattle not observed in estrus prior to the breeding season is common. Routinely, a single prostaglandin or a modified Ovsynch (MOFT) protocol are used—without evidence of their relative effectiveness. This study compares the effects on conception, associated timing, and profitability of administering cows with prostaglandin or MOFT treatment. A hundred and ninety-two Holstein-Friesian cows from three herds without an observed estrus within 28-days before mating start date were randomly treated with d-cloprostenol (PGOD) or an 8-day MOFT protocol. The association of treatment and calving-breeding start-date interval (CBSI) on the risk of conception were investigated. Partial budget, sensitivity analysis, and Monte Carlo simulation was used to assess economic performance, identify critical input variables, and explore the effects of input uncertainties on model output. There was a significant association between MOFT treatment and conception during 21 and 84 days after mating start date, compared to PGOD. MOFT treatment was associated with a mean net benefit of £58.21 (sd £19.42) and £27.29 (sd £17.75) per cow for herds with a fixed or variable dry-off date, respectively. The relative profitability of an MOFT protocol is dependent on its effects on barren rate and herd dry-off strategy.
Background: Seasonal calving herds account for around a fifth of dairy farms in the UK (AHDB 2016). Their structure allows focused farm management and seasonal labour requirements, as well as the opportunity to maximise the conversion of grazed grass into milk. However, their economic success is underpinned by a requirement for optimal reproductive management, and for this reason a thorough understanding of how to approach fertility in these herds is essential for veterinary surgeons involved in their management.Aim of the article: This article explains the concept of seasonal calving systems, the impacts of poor fertility, the key performance indicators used to monitor performance in clinical practice, and the key areas where improvements can be made.
Colostrum, the first milk produced by the cow before calving, is functionally and compositionally distinct from whole milk. Differences in fat, carbohydrate, protein, vitamin and mineral concentrations provide nutrition for the neonate. A high lipid content is an indispensable source of energy, while protein aids development and vitamins and minerals that are poorly transferred across the placenta can be provided orally. Immunoglobulins within colostrum are essential for the transfer of passive immunity, since the calf is born agammaglobulinaemic. Biologically active factors, including antimicrobial compounds, hormones, growth factors and immune-enhancing compounds, may contribute to immune development, intestinal growth and energy metabolism after birth. Bioactive substances may also direct the maturation of specific tissues via epigenetic effects that occur after parturition has occurred. An appreciation of the differences between colostrum and milk composition may be useful for all stakeholders interested in optimising early life feeding regimens for neonatal calves.
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