The Research Column

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.

Whole milk powder is an important product that is often exported to be reconstituted and used for various purposes. The spray drying to obtain the product enables milk to be easily transported and stored for extended periods of time. However, the spray drying process can also facilitate oxidative changes as the high fat content is exposed to elevated temperatures, resulting in reduced shelf life due to off-flavour development. Moreover, whole milk powder can also be subjected to extreme temperature fluctuations during transport and storage, further affecting oxidative stability.

The environmental impact of producing animal source foods is a critical topic of policy discussion in domestic and international governments, social media, the popular press, and the consumer marketplace. Livestock’s contribution to the environmental impacts associated with food production are significant concerns for all food chain stakeholders, including livestock producers who play a major role in reducing environmental impacts per unit of food.

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.

The environmental effects of mineral nitrogen are of global concern, and there is growing determination to mitigate its use for agricultural purposes. The replacement of synthetic fertilizer N with N fixed by bacteria (biological N fixation) in association with legumes such as white clover (Trifolium repens L.) offers the potential to lower fertilizer N use, nitrous oxide and ammonia emissions, and energy use.

Mastitis in dairy cows is costing the industry. It leads to treatment costs, milk production losses, and early culling of cows. For many years, blanket dry cow therapy (BDCT) has been the accepted treatment in mastitis control. It involves administering long-acting antibiotics to all cows and quarters at dry-off, regardless of their infection status or incidence risk during the dry period.

Reducing methane emissions in livestock production is one of the challenges of this century and researchers from different disciplines including nutrition, physiology, and genetics have made substantial efforts to develop tools that can help reduce methane emissions. Methane traits in dairy cattle have low to moderate heritability, from 0.11 to 0.33.

The gastrointestinal tract is highly sensitive to a large number of internal variables in the lifecycle of dairy cows. The hindgut is susceptible to acidosis, much like the rumen, but due to a variety of physiological and structural differences, it is less capable of tolerating acidosis than the rumen, resulting in increased permeability to antagonistic compounds and repartitioning of energy to support an immune response. By improving gut integrity and function, less energy is repartitioned, thereby saving energy for productive purposes.

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 onset of lactation markedly increases nutrient requirements of dairy cows. The concomitant reduction in feed intake around calving predisposes transition cows to a negative nutrient balance. High-yielding dairy cows may mobilize as much as 1 kg of tissue protein per day from skeletal muscle during the first 7 to 10 days of lactation to meet their amino acid requirements. Additionally, protein mobilization starts before parturition, likely to meet amino acid requirements for growth of the foetus, uterus, and udder tissue.