Abstract
The massive improvement in food production, as a result of effective genetic selection combined with advancements in farming practices, has been one of the greatest achievements of modern agriculture. For instance, the dairy cattle industry has more than doubled milk production over the past five decades, while the total number of cows has been reduced dramatically. This was achieved mainly through the intensification of production systems, direct genetic selection for milk yield and a limited number of related traits, and the use of modern technologies (e.g., artificial insemination and genomic selection). Despite the great betterment in production efficiency, strong drawbacks have occurred along the way. First, across-breed genetic diversity reduced dramatically, with the worldwide use of few common dairy breeds, as well as a substantial reduction in within-breed genetic diversity. Intensive selection for milk yield has also resulted in unfavorable genetic responses for traits related to fertility, health, longevity, and environmental sensitivity. Moving forward, the dairy industry needs to continue refining the current selection indexes and breeding goals to put greater emphasis on traits related to animal welfare, health, longevity, environmental efficiency (e.g., methane emission and feed efficiency), and overall resilience. This needs to be done through the definition of criteria (traits) that (a) represent well the biological mechanisms underlying the respective phenotypes, (b) are heritable, and (c) can be cost-effectively measured in a large number of animals and as early in life as possible. The long-term sustainability of the dairy cattle industry will also require diversification of production systems, with greater investments in the development of genetic resources that are resilient to perturbations occurring in specific farming systems with lesser control over the environment (e.g., organic, agroecological, and pasture-based, mountain-grazing farming systems). The conservation, genetic improvement, and use of local breeds should be integrated into the modern dairy cattle industry and greater care should be taken to avoid further genetic diversity losses in dairy cattle populations. In this review, we acknowledge the genetic progress achieved in high-yielding dairy cattle, closely related to dairy farm intensification, that reaches its limits. We discuss key points that need to be addressed toward the development of a robust and long-term sustainable dairy industry that maximize animal welfare (fundamental needs of individual animals and positive welfare) and productive efficiency, while also minimizing the environmental footprint, inputs required, and sensitivity to external factors.
Highlights
Sustainable agriculture is paramount to address the major challenges facing humankind, including human demography and food security, climate change, energy use, biodiversity, and the environmental footprint of human activity
Only 33 countries have a national average milk yield greater than 6 000 kg/cow/year (FAOSTAT, 2018; Fig. 1), which represents only a small fraction (~13%) of the world dairy cattle population but more than 40% of the total world milk
As we focus on increasing dairy sustainability, it will be crucial to evaluate the animals’ efficiency to digest alternative feed sources
Summary
The strong focus of the dairy industry on ensuring food security through higher productivity raises concerns on other sustainability dimensions (Clay et al, 2020) This requires us questioning continued selection strategies for milk yield in populations (or countries) that have reached very high production levels, but simultaneous selection for productivity and functional traits (e.g. adaptation, welfare, resilience) should be applied in low-producing populations, especially in local breeds and developing-country populations. The transition toward lower-input (with improved usage of resources) production systems needs to be favored This is required to minimize the environmental footprints of the industry, meet the food demands of a steadily growing population in face of rapid scientific and technological innovations, limited resources and land availability, greater environmental and ethical awareness of animal husbandry practices, demand for higher-quality products produced with lower use of antibiotics, and natural challenges (e.g., new pathogens and diseases, climate change). In some cases, there might be a need for greater governmental involvement to support changes in certain directions, especially toward better animal welfare and environmental footprints, as well exemplified by policies implemented in some European countries
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