The Research Column

Discipline: economics; Key words: profitability, marginal response, supplementary feed, marginal economics. 

Discipline: management; Key words: sensor technology, dairy cow behaviour, ruminating. 

Discipline: mastitis; Key words: bovine clinical mastitis, fertility, economics, animal health management. 

Costs associated with clinical udder infection can be divided into treatment costs, costs of mortality through culling (replacement of culled animals) and indirect costs from production losses. Intervention for clinical cases usually consists of (mainly within udder) antibiotic treatment. However, in light of its connection with antimicrobial resistance, it may be prudent to search for alternative interventions. For instance, culling cows with clinical mastitis could be a viable alternative.

South Africa is 13th on the list of highest emitters of global greenhouse gases GHG). Despite this is Africa still the smallest contributor to GHG emissions among the continents, yet the most vulnerable to the impacts of climate change. The effects will not be limited to rising temperatures and changing rainfall patterns, but also to increased severity and frequency of droughts, heat stress and floods. Agriculture is not only impacted upon by climate change but also contributes to global warming.

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.

Zinc (Zn) is an essential trace mineral and plays an important role in DNA and RNA synthesis and replication and in cell proliferation. Zinc supplementation has been shown to increase milk yield, live weight and growth rate, and enhanced disease resistance. With reference to the latter, it has been suggested that Zn deficiency could result in increased somatic cell count (SCC) and ultimately increase mastitis in dairy cows. 

Significant changes have occurred in the US dairy industry in the last decade, involving the number of dairy farms, herd size, milk quality, and management practices. Although the number of dairy cows in the United States has remained relatively constant over the past decade, at approximately 9 million head, the number of dairy operations has decreased by 30%, resulting in larger dairy farms. This trend is even more prevalent in the south-eastern United States, where the number of dairy farms has decreased by 39% from 5315 in 2008 to only 3235 in 2017.

In some countries lameness has been identified as the third most important health-related economic loss, after fertility and mastitis. Lameness has serious negative consequences on animal welfare and the environment. Secondly, lameness may reduce the overall lifetime performance of dairy cows due to milk production loss and culling, as well as having the potential to further affect sustainability by increasing the total greenhouse gas emissions per unit of milk produced. Furthermore, lame cows are more at risk for developing future mobility issues.

Time of dry-off, calving and the start of a new lactation are critical transition events for a dairy cow. Large changes in both physiology and management increase the risk for disease and culling. The cow faces these transition events every year, as a one-year calving interval is usually aimed for. A one-year calving interval is usually associated with a good average 305-day yield and better economic results compared with longer calving intervals.