The Research Column

Consumers complain about spoilage due to bacterial growth and spoilage also contributes to dairy product waste, which in a developing country we cannot really afford. We probably do not have figures in South Africa, but milk spoilage in the US amounts to $6.4 billion per year. Microbial spoilage is of particular concern and can be caused by either psychrotolerant spore formers, which likely originate from raw milk, or by post-pasteurization contamination (PPC).

In the studies, primary research papers were found through targeted Web of Science searches, the reference lists of recent reviews for each topic, and the reference lists of papers identified from these sources. Studies were included if they were published in English, the full text was accessible, and they compared treatments with and without contact between dairy cows and calves for a specified period. The resulting manuscripts underwent a 4-step appraisal process, and further manuscripts were sourced from reference lists.

Infectious diseases, such as metritis and mastitis, have  serious economic consequences due to the use of antibiotic treatment, the withdrawal period thereafter, delayed onset of cyclicity after calving, extended intervals between calving, and poor fertility . Most high-yielding dairy cows struggling with such diseases also have metabolic disorders, and some results have shown a connection between immunological defense and metabolic regulatory mechanisms.

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. Improving choline status pre-calving has the potential to reduce the risk of fatty liver and improve health and lactation.

The consumption of Mozzarella cheese in the form of Pizza toppings, salads, cheese blends have increased in recent years. The functional properties of the cheese are the ability to shred easily, melt rapidly, and reflect acceptable stretching, oiling-off and browning upon baking. Sodium chloride salt, starter cultures and acids are key ingredients in the manufacture of Mozzarella cheese and affect its functionality. Salting occurs either by brining or with dry salting.

Nitrous oxide (N2O) is a long-lived stratospheric ozone-depleting substance and greenhouse gas with an atmospheric lifetime of about 110-120 years. The concentration of atmospheric N2O has increased by more than 20% from 270 parts per billion (ppb) in 1750 to 331 ppb in 2018, with the fastest growth being in the last fifty years. Two key biochemical processes—nitrification and de-nitrification—control N2O production in both land and water ecosystems.

In the ultra-high temperature (UHT) process, milk is subjected to high temperatures, above 135 oC for a few seconds, resulting in a product with a shelf-life of several months when stored at ambient temperature. However, chemical and physical changes in the milk can lead to off-flavours, browning, fat separation, sediment formation or gelation during  storage. Important associated factors are processing parameters, storage conditions (time and temperature) and type of packaging.

Silage is an integral component of most dairy cow diets and research has primarily focused on improvement of silage quality and minimizing nutrient losses during ensiling. Silage inoculants have been the most commonly used additive for improving  quality.

The transition period is a critical period for dairy cows, characterized between three weeks before and three weeks after calving. This is a challenging period for dairy cows because of milk genesis, uterine contraction, as well as metabolic and hormonal changes associated with negative energy balance. Yeast products and yeast-containing feed ingredients can be used as a nutritional feed additive to improve health and performance during the transition between pregnancy and early lactation.

Mastitis is the most common disease in dairy cows, causing significant economic effects on milk production and compromising animal welfare. Antibiotic dry cow therapy (aDCT) is an effective way to control mastitis, as cows are susceptible to new within-udder infection at the time of drying-off and again during the immediate post-calving period. Selective dry cow therapy means that only infected or presumed infected cows are treated, instead of dry cow therapy being used as a treatment for all cows.