The potential for extended lactations in Victorian dairying: a review

Abstract

This review examines the potential for extended lactations on Victorian dairy farms in the context of (i)�the advantages and disadvantages of existing seasonal milk production systems; (ii) projected future changes to Victorian dairy farming; (iii) the mechanics of extended lactations; (iv) the change in costs associated with extended lactations; and (v) how extended lactations might be successfully implemented. Traditionally, Victorian dairying has been characterised by seasonal, low input, pasture-based milk production reliant on family labour. Successful implementation of this type of milk production system requires cows to calve in accordance with seasonal pasture supply. Recently a number of economic (static or falling milk prices), management (larger herds, increased labour expense, lower labour availability) and social pressures (animal welfare and environmental regulation) have emerged that question the viability of pasture-based dairying in a number of countries including Australia. Some of these threats to dairying may increase the attractiveness of systems that exploit the production potential of high yielding cows in larger herds, with increased supplementation of pasture-based diets over extended lactations. It is generally concluded that 12-month calving intervals are the most economic, based on the shape of the lactation curve and the perceived costs of extended lactations. However, these fundamentals have been changed by years of intensive selection for high milk production and the recent implementation of new management techniques such as Bovine somatotrophin, total mixed rations and increased milking frequency. Modern high yielding cows can maintain high daily yields for a much longer proportion of lactation than previously, but these cows are also largely unsuited to seasonal production systems due to a prolonged period of negative energy balance after calving and consequent low fertility. We have identified that calving and pregnancy incur substantial costs that are often hidden but need to be accounted for in valid economic comparisons. It is evident that seasonal pasture-based dairying requires disciplined management where certain tasks must be achieved in a timely manner if the system is to operate efficiently. Where the system does break down, often due to infertility for example, new management approaches are required. It is of concern that farmers may adopt a default position of extended lactations without realising or exploiting the potential benefits. Among the advantages of extended lactation management would be a more even spread in labour requirements, input costs and income across the year. In conclusion, extended lactations are a suitable option for some Victorian dairy enterprises. That suitability will depend on a number of factors; particularly, cow milk production potential, ability to grow pasture or feed supplements economically, management expertise, environmental constraints, herd size and labour availability.

A New Perspective on Management of Reproduction in Dairy Cows: the Need for Detailed Metabolic Information, an Improved Selection Index and Extended Lactation

“…They found no significant decrease in daily milk yield but, importantly, they observed economic advantages in cows with extended lactations. Other reports from Sweden [29] and Australia [30] also concluded that extended lactations are a suitable option for some enterprises, and that suitability will depend on various factors, particularly cow milk production and especially persistency (the rate of decline in milk yield from peak), as well as management.…”

Genetic and phenotypic parameters of lactations longer than 305 days (extended lactations)

“…Furthermore, almost all cows are milked for about 300 days and are dried off at a pre-determined date. Recently, the seasonal calving system is being challenged due to increased herd size, increased use of bought-in feed, premium paid for off-season milk, increased milk production potential, reduced reproductive performance and pressure from animal welfare groups to minimise induced calving (Borman et al, 2004). As a result of these factors, interest in milking cows beyond the standard 305 days (over an extended lactation period) has increased and the proportion of herds that practice seasonal calving in Victoria, Australia, has decreased from 63% to 41% (Auldist et al, 2007).…”

Effect of Delayed Insemination on Holstein Cows’ Reproductive Performance

“…2 Estrus_AI: number of insemination at estrus, not counting the double AI at estrus. 3 Total AI: total number of AI per pregnancy, counting the double AI at estrus. 4 Estrus_PR 1 or PR 2 : pregnancy rates at first and second AI (with the first AI defined as estrus_AI).…”

“…More artificial inseminations (AI) in successive estruses are now needed to obtain pregnancy which is then involuntarily delayed [3]. This increase of reproductive failure and number of AI needed per pregnancy might be partly due to a decrease of estrus behavior, which makes it difficult to detect estrus and to inseminate the cow at the right stage [4].…”