Dairy R&D in SA

Some interesting results have been reported by Dr Jan van Wyk, who is responsible for the Milk SA project: Fasciola hepatica: Impact on Dairy Production and Sustainable Management on Selected Farms in South Africa. The report is from the fourth quarter of 2018.

Members of the Enterobacteriaceae family have been associated with food safety and spoilage problems. Enterobacteriaceae can enter an inadequately cleaned dairy chain and cause enzymatic breakdown of proteins or lipids, instigating spoilage which contributes to substantial economic losses and wastage. Some Enterobacteriaceae have also emerged as potential opportunistic pathogens due to acquisition of virulence and antibiotic resistance and some, including E.

Conjugated linoleic acid (CLA) has the ability to inhibit growth in a number of human cancer cell lines. It is also immune-modulating and growth-promoting and was shown to decrease fat mass without significantly affecting body weight. In terms of prevention of heart disease, CLA depressed total cholesterol and lowered the ratio of low-density lipoprotein (LDL) to high-density lipoprotein (HDL).

In recent years, there has been an increase in the prevalence of environmental pathogens as a cause of within udder infections in dairy cattle. Increases in prevalence could potentially be ascribed to improved control methods for contagious pathogens, difficulties in controlling pathogens from an environmental reservoir and the ability of Streptococcus uberis and Escherichia coli to persist in the udder. Streptococcus uberisshowed an increase in prevalence over an 11-year study period (1996–2007) in South African dairies.

 Author: Heinz Meissner, Milk SA Program Manager R & D, November 2018.   

1. Mastitis Program:

1.1. PRJ-0210 Antimicrobial resistance on dairy farms - Screening mastitis causing coliforms for the production of extended spectrum Beta-lactamases and Colistin resistance. Dr Inge-Marie Petzer.

Ideally, pasture management should emphasize production of optimum forage yield and quality, without compromising the environment. Accurate irrigation scheduling, therefore, plays an important role in the success of a dairy enterprise by affecting forage yield and quality, irrigation input and energy usage, and environmental pollution. For years farmers arbitrarily have used an irrigation guideline of 25 mm of irrigation water per week for most temperate grasses and legumes, regardless of season or region.

The South African dairy industry shows immense diversity when it comes to mastitis management practices. However, if consistently executed, which should improve udder health and milk flow, it could be satisfactory, but supporting the diversity by extension is a challenge. As is the case globally, the dairy industry is aware of and actively addressing antimicrobial resistance (AMR). To that effect, a survey was funded by Milk SA to record what practices are followed and a project: ‘Resistance to Available Antibiotics in Lactating Cows with Mastitis’, was initiated in 2015.

Dairy farms often experience a summer through autumn rise in somatic cell count (SCC) with some farms affected more than others.  The extent to which climatic factors contribute to this summer rise in SCC in South Africa is unknown although weather is blamed anecdotally. Consequently, the value of heat abatement or other preventative intervention cannot be established. The relative effect of season and/or heat stress on milk production and SCC is likely to be unique to South African conditions and therefore this formed the basis of the study cited below.

The dairy industry is a major consumer of antibiotics globally and mastitis is the most treated disease of dairy cows. In South Africa, producers have unrestricted access to 12 of 22 registered within-udder antibiotic products without prescription, whereas the remaining 10 registered products are restricted for veterinary use. It is conceivable that the antibiotics available without prescription may be used incorrectly and may contribute to the emergence and/or persistence of antibiotic-resistant strains. 

The sustainability of current nitrogen (N) fertilization regimes for minimum tillage kikuyu-ryegrass (Pennisetum clandestinum, Lolium multiflorum) pastures in the southern Cape is questioned. The guidelines, originally, were developed for conventional tillage and non-grazing systems. It may well be that these guidelines may not apply any more. In fact, there is the possibility that the N levels applied are too high with implications to both economics and leaching of unutilised N.