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Department of Animal Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville 32611
This volume represents the span of invited papers presented at the Eighth International Workshop on the Biology of Lactation in Farm Animals (BOLFA) held in Pirassununga, Brazil, August 21 to 23, 2006. That meeting was the first BOLFA workshop not held as a companion to a European Association for Animal Production (EAAP) or American Society of Animal Science (ASAS) meeting, and the first outside of North America or Europe. Despite these venue departures from the norm, the workshop format of interactive discussion on topics related to milk production in farm animal species was unchanged. This volume begins with a paper from Antonella Baldi’s group (Baldi et al., 2008
) that provides a historical perspective of previous BOLFA workshops with an emphasis on nutritional factors that influence mammary function. It sets the stage for the later papers that consider aspects of milking management and mastitis treatment to improve milk yield in farm animal species.
The next series of contributions focus on environmental and management influences on mammary function. Dahl (2008) summarizes recent developments in the study of photoperiod exposure during the dry period and develops a hypothesis that prolactin-mediated events influence mammary cell turnover and metabolic gene expression in the liver. These findings lead to a discussion of similarities between photoperiodic and thermal influences on prolactin-related responses, and the potential for a common pathway for environmental effects.
Without competent milk ejection, lactation fails. More thorough understanding of what stressors lead to disruptions in the milk ejection reflex, or inhibit it completely, will allow for the development of new methods to limit the impact of those stressors. Bruckmaier and Wellnitz (2008) summarize the many factors that may impact milk ejection and suggest management approaches to optimize that reflex and ensure competent milk ejection.
Whereas acute management factors can produce stress that inhibits milk ejection, there is also evidence that genetic factors play a role, and this is particularly noticed in cattle that have some level of Bos indicus breeding. Negrao (2008) compares the responses of oxytocin, prolactin, and cortisol release to machine milking or suckling in Gir, Gir x Holstein, and Holstein cows. The observation that cortisol concentrations are greater in pure Gir cows at milk ejection relative to the Gir x Holstein and purebred Holstein cows is indicative of greater stress sensitivity in Bos indicus cattle relative to those of Bos taurus breeding. However, circulating prolactin and oxytocin increased in Gir cows to a similar extent to the other breeds under most conditions. These results indicate that Gir cows are able to produce milk under intensive management but may require effective stress adaptation than cows of Bos taurus breeding.
Wall and McFadden (2008) provide a compelling argument that supports the concept of a period early in lactation when mammary cell function can be amplified by more frequent milk removal, and more importantly that this response is mediated locally in the mammary gland. The unilateral frequent milking model described in this paper can be applied to questions of basic mammary function and used to develop management systems that can improve the efficiency of milk production at the farm level.
Consideration of milk ejection and milking frequency is essential to successful management of automated milking systems. Svennersten-Sjuanja and Pettersson (2008) review the current state of knowledge of automatic milking in Europe, where the majority of the world’s 8,000 robotic milkers are used. Although automation of milking provides a significant labor savings to producers, it is clear that the approach is only successful when integrated as a part of an overall management scheme for cows that includes feeding, housing, and movement.
The contribution from Marnet and Komarra (2008) reviews the impact of different milking frequency on yields from cattle, sheep, and goats. Marnet and Komarra present evidence that supports the concept of significant storage site impact on the ability of ruminants to maintain galactopoiesis in the face of less frequent milk removal. Relative to cows, does and ewes have large mammary gland cisterns and store a substantial fraction of milk between milkings in those cisterns rather than in the alveolar lumen. Better understanding of the relationship of mammary anatomy to yield losses with less frequent milking may improve lactation, as well as labor management in certain species of ruminants most adaptable to less frequent milking.
The final 2 papers in the symposium focus on mastitis, the most costly disease related to dairy production across all species. Zhao and Lacasse (2008) summarize the latest findings in mastitis research, with emphasis on the potential for immune response itself to cause tissue damage within the mammary gland. Awareness of how antioxidants may blunt the pathogenic effect of local immune responses should lead to improvements in mastitis management, not only to eliminate the infectious agent but also to lessen the severity of the tissue damage.
The traditional mastitis therapy of antibiotic treatment is the subject of novel methods to improve efficacy through combination with innate compounds of the mammary gland. Lacasse et al. (2008) describe investigation of the iron scavenging compound lactoferrin as a naturally occurring enhancer of antibiotic action in the mammary gland. Their studies offer evidence that even pathogens that are normally recalcitrant to antibiotic therapy, such as S. aureus, are responsive when that therapy includes a lactoferrin component. These types of combination therapies may result in more effective mastitis treatment with lower use of antibiotics in the future.
Collectively, the reviews found in this volume reflect a small segment of current research in lactation biology and mammary function. They offer, however, a view of the spectrum of basic to translational approaches that are brought to bear on these issues using farm animals as models. In keeping with previous BOLFA workshops, the success of this meeting was based on this broad discussion of lactation biology that continues to serve as a catalyst for further investigation and new methods to improve the efficiency of milk production of farm animals.
Received for publication October 26, 2007. Accepted for publication October 28, 2007.
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