The Research Column

The environmental effects of mineral nitrogen are of global concern, and there is growing determination to mitigate its use for agricultural purposes. The replacement of synthetic fertilizer N with N fixed by bacteria (biological N fixation) in association with legumes such as white clover (Trifolium repens L.) offers the potential to lower fertilizer N use, nitrous oxide and ammonia emissions, and energy use.

Below par post-calving health has a negative effect on the performance and survival of dairy cows and occurrence of uterine, metabolic and other health disorders which are risk factors for lower subsequent fertility and milk yield, and higher risk of culling. The interrelationship between loss in body condition score (BCS) and disease prevalence is however complex and establishing cause and effect associations is challenging. Increased risk of milk fever, ketosis, fatty liver, metritis, digestive disorders and mastitis in cows with greater loss of BCS after calving has been shown.

In the study, the effects of homogenization conducted at higher pressure than the conventional (10 megapascal [MPa] for the first stage and 5 MPa for the second stage) on curd structure of set yogurt was investigated, the focus being on the fat globule size. Each yogurt mix was adjusted at the range of fat globule sizes from 0.45 μm to 1.1 μm by a homogenizer and then heated at 95°C for 5 minutes (conventional heat treatment), 120°C for 2 seconds (ESL processing) or 140°C for 2 seconds.

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: 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: breeding; Keywords: productivity measures, inbreeding, longevity, replacement costs, heritability, fitness traits.

Discipline: carbon footprint; Keywords: production systems, milk yield, fertilizer use, manure management, rumen fermentation.

Discipline: disease; Keywords: liver fluke, parasitic disease, lymnaeid snail, drug therapy, molluscicides, milk withdrawal period.

Discipline: probiotics: Key words: yogurt, fermented milk, probiotic viability, storage stability, sensory preference.                                                                  

Discipline: reproduction; Key words: dairy cow, body temperature,