The Research Column

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.

Compared with Holstein milk, some conventional milk replacer (MR) formulations provide high amounts of lactose, low concentrations of fat, and comparable crude protein levels. Consequently, MR provides a lower dietary energy density than whole milk. Fat inclusion in MR compositions should raise the energy content, but the literature shows both positive and negative results.

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.

Up to 90% of administrated antibiotics are eliminated from the animal body through the faeces or urine, implying that manure generated from animal production represents a major route of antibiotic transfer to the environment. The presence of antibiotics, even at very low concentrations, can contribute to emergence of antibiotic resistance genes (ARG) and selection of antibiotic resistant bacteria.

In a report by Dr Indur Goklany who was a founding member of the International Panel on Climate Change (IPCC), the effects we currently experienced and other evidence which are considered as evidence of climate change, the author challenged the interpretations. The reference to the paper is: I.M. Goklany, 2021. Impacts of Climate Change: Perception and reality. Report 46, The Global Warming Policy Foundation. The question is what should we make of this.

The foods we eat may have a direct impact on our cognitive acuity in our later years. This is the key finding of an Iowa State University research study by Dr B.S. Klinedinst and colleagues, published in the November 2020 issue of the Journal of Alzheimer's Disease, with reference: doi.org/10.3233/JAD201058. The title of the paper is: Genetic factors of Alzheimer’s Disease modulate how diet is associated with long term cognitive trajectories: A UK Biobank Study.