A 2-year study reveals implications of feeding management and exposure to mycotoxins on udder health, performance and fertility in dairy herds
Journal of Dairy Science, Vol. 107, No. 2, 2024.
This article, from Austrian researchers, aimed to characterize to which extent factors related to the occurrence of mycotoxins and their secondary metabolites, as well as the different feeding management actions among Austrian dairy farmers, contribute to the fertility, udder health traits and performance of dairy herds. For the study, the researchers surveyed 100 dairy farms between 2019 and 2020, visiting each farm two times, and collecting data and feed samples. Data collection involved information on the main feed ingredients, nutrient composition and the levels of mycotoxin and other metabolites in the diet. They hypothesized that farms with the greatest mycotoxin contamination levels, high contents of phytoestrogens and suboptimal nutritional status would have higher risks for impaired health (mainly udder health), productivity and reproductive performance.
The authors say mycotoxins, which to some extent go neglected in ruminants, are one of the most critical threats to food and feed safety and security due to their effects on human and animal health. Thus, these compounds can have considerable economic implications. The toxicological activity of mycotoxins can be manifested as hepatotoxicity, neurotoxicity, nephrotoxicity and secondary infections induced by immunosuppression, and the signs or lesion manifestations can be delayed due to long-term exposure. Additionally, they say, impaired fertility or disorders could result from dietary exposure to mycotoxins and phytoestrogens. Some fungal metabolites, such as zearalenone (ZEN), as well as plant metabolites, such as phytoestrogens, are known compounds with estrogenic activity. Another interesting aspect is that although the ruminal microbiota can metabolize many toxins, the released metabolites from ruminal mycotoxin degradation are not always less toxic. For instance, the ruminal metabolism of ZEN in the rumen can result in the metabolite alpha-zearalenol, which has a potency factor of 60 compared with the parent compound.
The article lists some generic signs associated with subclinical mycotoxicosis in livestock. The most common are a reduction of feed intake, a decrease in nutrient absorption, presentation of metabolic disorders, endocrine alterations and a decline in reproductive as well as productive performance. Fusarium-derived mycotoxins and metabolites are considered the most relevant fungal contaminants in the total mixed ration (TMR) of dairy cows and other animal feeds, which could be detected across feedstuffs of TMR. They also say that there is a group of emerging mycotoxins such as enniatins (ENN), beauvericin (BEA) and culmorin (CUL) that co-occur with other fusarium mycotoxins, such as deoxynivalenol (DON), ZEN and fumonisin B1 (FB1). ENN and BEA have antibacterial and cytotoxic properties that can affect the rumen ecosystem, generating disruptions to the microbiome; however, the implications of these emerging mycotoxins are still not well known.
The conclusions of the study underline the potential risks of dietary contamination of fusarium metabolites on the udder health of dairy cows. Primiparous cows were more susceptible compared with multiparous cows in this regard. Corn silage was found to be a risky feed source affecting udder health traits because it is associated with fusarium mycotoxin contamination in dairy rations. The authors say that considering the limitations of the ecological studies, research using controlled conditions will be necessary to clarify the effects and thresholds of mycotoxins and other secondary metabolites on the health as well as the productive and reproductive performance of dairy cattle.
Perspective: Prolonged cow-calf contact – a dilemma or simply another step in the evolution of the dairy industry?
Journal of Dairy Science, Vol. 107, No. 1, 2024.
This article from researchers from Wisconsin and British Columbia Universities, addresses the contentious issue of cow-calf separation at birth, stating this practice is incongruent with many views on acceptable farming practices and carries the risk of eroding public trust in the dairy industry if it goes unaddressed.
The authors indicate the future prosperity and long-term sustainability of the dairy industry rests on the willingness of consumers to purchase fluid milk and other milk products. This willingness is dependent upon the industry’s ability to retain its social licence to operate. However, the dairy industry is increasingly subject to criticism, with much negativity focused on many standard animal practices that fail to resonate with societal values. This may – eventually – erode the public trust. Also, they add that when farm animal industries fail to respond to social risk, some regions have observed increases in regulatory requirements.
The fact that dairy cows must have a calf to produce milk and that this calf is separated within hours of birth contradicts the pastoral image most people have of the dairy industry. The immediate separation of the cow and her calf is highly contentious in multiple regions. There are only a limited number of studies that have addressed this practice, and this limits the ability to advise on how best to house and manage such a system in ways that ensure high standards of animal welfare while ensuring economic sustainability for the farm business. Advocates of the practice of immediate separation indicate perceived reasons for this, like a reduction in weaning distress by preventing the formation of a strong maternal bond, the potential for improved management of colostrum delivery and the ability to limit the volume of milk that calves consume.
The authors pose the question: “Should dairy producers persist with early cow-calf separation in the hope that science supports the practice? Or will the dairy industry continue to evolve, as it has done in the past when it transitioned, for example, from tiestalls to freestalls or from parlour milking to automated milking systems?” They say the available scientific evidence indicates early cow-calf separation will not be supported by science. There is substantial evidence that prolonged cow-calf contact improves calf growth rates and reduces negative oral behaviours (e.g., cross-sucking). The highly protective effect of prolonged cow-calf contact on mastitis taken together with the prediction that increased frequency of sucking may also be protective for metritis, suggests there may be animal-health and farm-profitability benefits in providing prolonged contact.
One of the problems with this research is that housing cows and calves together is complex. The calving area and early postpartum housing will need to be adapted to prolong cow-calf contact and is considered to be an area of weakness in the current housing and management of dairy herds. The authors say one-third to one-half of all freestall-housed dairy herds report moving recently calved cows into a sick pen with cows suffering mastitis or other infectious diseases, such as mycoplasma and salmonella. Thus, the argument by many in the industry that we must continue to separate calves at birth because it is the “ideal approach” cannot be made in this instance.
There are many questions regarding the implementation of this system: is partial daily contact between cows and calves sufficient to meet the welfare needs of both cows and calves and retain public trust? Should the duration of prolonged contact be limited to the milk-feeding period of 8 to 12 weeks as is commonly used by the dairy industry – a considerably shorter time to weaning than would occur in nature. Should we manage bull calves and their dams differently or the same as heifer calves and their dams? What should be done with mothers that birth a stillborn calf? The list of questions could go on.
Additionally, to address producers’ concerns and provide a tool to assist their decision-making, a detailed economic model will be needed to facilitate the discussion. This model needs to evaluate the changes in labour requirements along with the loss in salable milk from the cows that continue to suckle their calves, balanced against the reduction in the use of milk replacer, the improved growth rates achieved for the calves, the potential for higher milk yield post-weaning and the overall improved health of both cows and calves.
The authors conclude by saying that this begins with the general acceptance that we need to find alternatives to the aspects of our current management practices that fail to resonate with societal values. They say this is a major first step but one they feel is necessary and inevitable for the continued maintenance of public and consumer trust. This is not merely a case of stopping doing something unnecessary, as was the case with tail docking. In this instance, we must find a new path forward to achieve something with positive outcomes for the animals, the farm business, the dairy industry and the wider community.
This column brings you information regarding some of the research being done around the world and published in the Journal of Dairy Science. The objective is to bring to light areas of research that may have an immediate practical application on a dairy farm, as well as research that, even though it may not have a practical impact now, could be interesting for its future potential application. The idea is to give a brief overview of select research studies but not go into detail on each topic. Those interested in further in-depth reading can use the citations to find each study.
