The Research Column

Discipline: disease; Keywords: pathogen, faecal culture, blood serum tests, economic losses, culling.

How does infection with Johne's disease affect milk production in dairy herds? Smith and co-workers studied the status of the disease in three herds in the US and tried to predict the impact on milk production when the condition is latent or when the cows are actually shedding cells. The study was published in the Journal of Dairy Science, Volume 92 of 2009, pages 2653 to 2661, with the title: A longitudinal study on the impact of Johne's disease status on milk production in individual cows.

Discipline: birth weight; keywords: mortality, stillbirths, reproductive performance, calf-cow size index.

It is known that heavier calves tend to be more prone to stillbirths, dystocia and lower calf survivability than lighter, smaller calves, but it is not known whether calf birth weight is also associated with other factors affecting the economic efficiency of the dairy herd. A number of such factors were included in the study of T.C. Linden and co-workers reported here; the title being: Calf birth weight and its association with calf and cow survivability, disease incidence, reproductive performance, and milk production. The paper was published in the Journal of Dairy Science, Volume 92 of 2009, page 2580 to 2588.

Discipline: carbon footprint; Keywords: methane, nitrous oxide, volatile organic compounds, ammonia, LCA, emissions per unit of production.

This question was discussed in an Invited Review by S.E. Place and F.M. Mitloehner of the University of California in the US, in a paper entitled: Contemporary environmental issues: A review of the dairy industry’s role in climate change and air quality and the potential of mitigation through improved production efficiency, published in the Journal of Dairy Science, Volume 93 of 2010, pages 3407 to 3416.

Discipline: housing; Keywords: thermal protection, durable lying surfaces, behaviour, free-stall lying surface softness, culling.

Is there an advantage to having soft flooring material instead of concrete? A recent Danish study investigated whether this was indeed the case; reference: L.E. Ruud, K.E. Bøe and O. Østerås. Associations of soft flooring materials in free stalls with milk yield, clinical mastitis, teat lesions, and removal of dairy cows. Journal of Dairy Science (2010) Volume 93, pages 1578-1586

Discipline: starter culture; Keywords: industrial cheese manufacturing, enzymatic coagulation, protein separation, proteolysis.

Miniature cheeses can open up new possibilities to screen cheese starter cultures and study many other aspects of cheese production in the factory. The study was reported by H. Bachmann and coworkers in the Journal of Dairy Science (2009), Volume 92, pages 5868-5882, using the title: A high-throughput cheese manufacturing model for effective cheese starter culture screening.

Discipline: yogurt; Keywords: lactic acid bacteria, stirring, low-speed agitation, process time, acidity profile, microbiological dynamics.

Is agitation during fermentation beneficial to yogurt characteristics? This question was addressed by E.J. Aguirre-Ezkauriatza and coworkers in a study entitled: Effect of mixing during fermentation in yogurt manufacturing, which was published in the Journal of Dairy Science (2008), Volume 91, pages 4454-4465.

Discipline: reproduction; Keywords: reproductive performance, genetic progress, health, glucose manufacturing, hormonal interference, appetite control.

Sub-fertility in high-producing dairy cows is a known problem in most countries, also in South Africa. The question is do we understand the causes and can farmers limit the consequences? The status of current knowledge and understanding has been reviewed recently by L.M. Chagas and co-authors in a paper published in the Journal of Dairy Science (2007), Volume 90, pages 4022-4032; the title being: New perspectives on the roles of nutrition and metabolic priorities in the sub-fertility of high-producing dairy cows.

Discipline: body condition score; Keywords: body reserve status, fat, hormonal changes, pregnancy, metabolic disorders.

Research in this context was reviewed by J.R.Roche and coworkers in a paper published in the Journal of Dairy Science, Volume 92, pages 5769 to 5801. The title of the paper is: Body condition score and its association with dairy cow productivity, health, and welfare.

Discipline: dairy & health; Keywords: inflammatory diseases, CLA, fishy flavors, rumen-inert calcium salts, sensory panel.

This topic was addressed by K.A.S. Nelson and S. Martini in a paper called: Increasing omega fatty acid in cow's milk through diet manipulation: Effect on milk flavor. The paper was published in the Journal of Dairy Science, Volume 92, pages 1378-1386.

Discipline: probiotics; Keywords: fermentation, flavour, human health, starter culture, propionibacteria.

Researchers F.Y. Ekinci and M. Gurel thought so and tested the concept in their research published in the paper: Effect of using propionic acid bacteria as an adjunct culture in yogurt production. The paper was published in The Journal of Dairy Science, Volume 91, pages 892-899.