The Research Column

Discipline: sensory; Keywords: texture, aroma, flavour, taste, scorecard judging, analytical sensory tests, descriptive analysis.

Is sensory analysis a valuable tool to the dairy product manufacturer? M.A. Drake was invited by the American Dairy Science Association to review the work done on sensory appraisal. The title of his Review which was published in the Journal of Dairy Science, Volume 90 of 2007, page 4925 to 4937, was appropriately: Sensory Analysis of Dairy Foods.

Discipline: calf rearing; Keywords: individual housing, starter intake, group housing, automatic feeding system, target weight, respiratory problems.

The question addressed is when pre-weaning calves housed individually can be grouped successfully without increasing stress and the incidence of disease. This research by Drs Bach in colleagues was published in The Journal of Dairy Science, Volume 93 of 2010, pages 413 to 419. The title of the paper is: Optimizing weaning strategies of dairy replacement calves.

Discipline: mastitis; Keywords: dry cow therapy, Staphylococcus aureus, antibiotics, re-infection,teat sealant.

 In a large study this question was addressed in two papers: in the first paper the preventive effect of various dry cow measures on new infections were investigated and in the second paper the cure of existing infections. These studies are unique in the sense that a highly powerful statistical method, called meta-analysis, was used which enable scientists to pool research data from various studies conducted in different circumstances and synthesize a highly reliable result which for all practical purposes can be considered correct to implement. The titles of the respective papers published by T. Halasa and co-workers in the Journal of Dairy Science, Volume 92 of 2009, page 3134 to 3149 and page 3150 to 3157 are: Meta-analysis of dry cow management for dairy cattle. Part 1. Protection against new intramammary infections and Part 2. Cure of existing intramammary infections.

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.