The Research Column

Bacterial contamination of foods may lead to reduced shelf life due to outgrowth of spoilage organisms and, in the case of pathogens, to food borne illness upon consumption of contaminated products. To inactivate bacteria that may grow in finished products, many food products undergo heat treatment. Pasteurisation results in inactivation of vegetative cells. However, bacterial spores will survive such treatments, after which they may germinate and grow in finished liquid products.

Choline is a known essential nutrient as it is required for synthesis of essential membrane phospholipids, acts as a precursor for synthesis of acetylcholine, and in particular, has a role in lipid intermediary metabolism. In ruminants, however, almost all dietary choline is degraded by ruminal microbes and requires choline to be supplemented in a rumen-protected form. 

Successful management of an automatic milking system (AMS) requires effective functioning of the milking unit (MU). It is well established that an increased detachment level, i.e. earlier removal of the teat cups at the end of milking, can decrease milking time substantially with minimal to no milk yield loss. However, these studies were all conducted at cluster level, and some studies suggest an increase in residual milk or strip yield at increased cluster detachment levels, which indicates decreased udder emptying.

Trace minerals such as Cu, Zn, and Mn are essential to life, and their deficiencies in livestock result in health deterioration. In an effort to prevent such deficiencies, dairy cows are commonly supplemented with Cu, Zn, and Mn. Various sources of trace minerals are used for this purpose, with inorganic sources (oxides, chlorides, sulphates, and carbonates) being the most commonly supplemented to dairy cows. Alternative sources such as organically complexed trace mineral supplements (chelates) are specifically developed to provide greater nutritional bioavailability.

branched-chain volatile fatty acids, valerate. 

The onset of lactation markedly increases nutrient requirements of dairy cows. The concomitant reduction in feed intake around calving predisposes transition cows to a negative nutrient balance. High-yielding dairy cows may mobilize as much as 1 kg of tissue protein per day from skeletal muscle during the first 7 to 10 days of lactation to meet their amino acid requirements. Additionally, protein mobilization starts before parturition, likely to meet amino acid requirements for growth of the foetus, uterus, and udder tissue.

Whole milk powder is an important product that is often exported to be reconstituted and used for various purposes. The spray drying to obtain the product enables milk to be easily transported and stored for extended periods of time. However, the spray drying process can also facilitate oxidative changes as the high fat content is exposed to elevated temperatures, resulting in reduced shelf life due to off-flavour development. Moreover, whole milk powder can also be subjected to extreme temperature fluctuations during transport and storage, further affecting oxidative stability.

Listeria monocytogenes is a pathogen which may cause listeriosis with sometimes grave consequences. It is a ubiquitous, gram-positive, facultative anaerobe that grows at refrigeration temperatures and is found throughout the environment, specifically in soil and water. Listeria monocytogenes may survive in food that has a relatively high acid and salt content and can tolerate high and low temperatures.

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.

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.