The Research Column

Improved animal health and resilience are important breeding objectives for the dairy cow. Many diseases affecting the cow occur in the first 30 days after calving. Some of these diseases are associated with metabolic disorders such as ketosis and milk fever, which can have deleterious effects on animal health and welfare and farm profitability. Although heritability estimates of metabolic disorders are generally low, sufficient genetic variation exists suggesting that improvement in metabolic health through selection should be possible.

Dairy cows often experience negative energy balance in early lactation because the energy intake is insufficient to meet the sudden increase in demand for milk production. Therefore, high-starch diets are usually fed to early-lactation dairy cows to reduce the energy deficit. However, high-starch diets during the first several weeks after calving may decrease rumen pH and further increases the risk of sub-acute ruminal acidosis (SARA).

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.

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.

The nutritional and pharmacological advantages of chromium (Cr) for animals and humans have been well established. Trivalent Cr is a component of chromodulin which is involved with insulin regulation, and thereby associated with the metabolism of carbohydrates, protein and lipids. The signs of Cr deficiency include impaired nutrient metabolism, lower sensitivity of the peripheral tissues to insulin, compromised immunity and decreased weight gain and health status, specifically under stressful conditions.

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.

Standardization of terminology is important as people often develop definitions which  the meaning thereof is not recognized or understood by others, or they use one term for different activities or functions. One such term is culling which is used in different ways leading to confusion or misinterpretation. To address this Dr J. Fetrow and colleagues were commissioned by the American Dairy Science Association to address the confusion and come up with recommendations.

When products derived from the coagulation of milk are produced, liquid whey results which may account for 80 to 90% of the milk which originally entered the dairy manufacturing facility and about 50% of the milk nutrients. The composition of the whey varies depending on the end product, and the manufacturer’s production process. Hard cheeses (e.g. Cheddar) result in sweet whey, with a relatively high pH (more than 5.8), high protein and low mineral contents. Fresh cheese and strained yogurts ( e.g.

Greenhouse gases (GHG), including methane (CH4), play an important role in global warming. Methane has 28 times the global warming potential of CO2. Although in SA the figures are much lower due to the small size of the dairy industry, the global dairy supply chain produces 20% of the livestock-sector’s GHG, and 46.5% of that is from enteric CH4.

Serum total Ca (tCa) and whole-blood ionized Ca (iCa) were monitored in 24 multi-lactation Holstein cows after parturition. Pre-calving diets were formulated with a positive dietary cation-anion difference of 172 mEq per kg of DM and contained 4.1 g of Ca per kg of DM. At calving, cows were blocked by calving sequence and blood Ca status as either normo-calcaemic (cut-off threshold of iCa equal or more than 1.10 mmol per L) or hypocalcaemic (cut-off threshold of iCa less than 1.10 mmol per L).