The Research Column

Discipline: behaviour; Key words: automatic jaw movement recorder, grazing behaviour, validation.  

Discipline: breeding; Key words: genomic testing, rate of genetic gain, sexed semen   

Bacteria are ubiquitous microorganisms present in all known environments, including various areas of the animal body as well as in fermented dairy foods, where they are organized in complex consortia. The microbial ecology of fresh cheese has been extensively investigated, and has lead to the generally accepted understanding that bacteria residing in milk may contribute beneficially to the aroma of fermented dairy products. Here, lactic acid bacteria are particularly important due to their positive or negative impacts on fresh and ripened cheese.

The utilization of functional foods has increased since the last decade. In many instances they form part of the daily diet where they have the potential to lessen the risk of disease along with their accepted nutritional efficacy. The beneficial effects are due to the presence of physiologically active components, which have the ability to lessen the threat of chronic diseases.

The health, well-being and reproductive status of dairy cows, apart from profitability in production, should be the most important considerations in animal breeding. Normally though, genetic evaluation focuses mostly on the genotypic background which influences economically important traits such as milk yield and composition. However, in many countries selection for enhanced milk performance has caused a decline in cow reproduction and consequently, this has led to increased interest associated with non-production traits, including reproductive efficiency, longevity and health.

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, heat treatment is often used. Pasteurisation usually is effective to inactivate vegetative cells, but bacterial spores will survive, after which they may germinate and grow in finished liquid products.

Enteric methane is to varying degrees an end product of microbial fermentation in the rumen and hindgut of ruminant livestock. Because it is a potent greenhouse gas (GHG) that contributes to global warming, enteric methane has become one of the main targets of GHG mitigation practices in the dairy industry. Several dietary strategies may contribute to mitigating enteric methane production, including the use of feed additives.

Lactation yield estimates standardized to common lactation lengths of 270 or 305 days are commonly used in management decisions and genetic evaluations. The use of such measurements to quantify the merit of individual cows fails to penalize cows that do not reach the standardized lactation length, or vice versa to reward cows that lactate for more than the standardized lactation length. The objective of a study by Dr M.

The nitrogen (N) use efficiency (conversion of feed N into milk N) of dairy cattle is poor, typically ranging from 25 to 35%. The unused feed N is excreted about equally via the faeces and urine, although the proportion depends on the crude protein (CP) level and the ratio of rumen degradable protein (RDP) to rumen undegradable protein (RUP) in the diet. The excreted N is lost at each stage of manure management (e.g., during collection, storage, and after land application) in several forms: ammonia (NH3), nitrous oxide (N2O) and nitrate.

Although limited in South Africa, many dairy cattle worldwide are still housed in tiestalls, meaning that they are tethered by the neck to individual stalls. On some farms, tied cattle are permitted seasonal access to pasture, but otherwise their movements are restricted compared with cows housed in freestall barns or other loose housing systems. The aim of the systematic review by Dr A Beaver and colleagues was to summarize the scientific literature pertaining to the welfare of tied dairy cattle through comparison with less-restrictive housing systems.