Keeping Dairy Cows for Longer: A Critical Literature Review on Dairy Cow Longevity in High Milk-Producing Countries

Abstract

The ability of dairy farmers to keep their cows for longer could positively enhance the economic performance of the farms, reduce the environmental footprint of the milk industry, and overall help in justifying a sustainable use of animals for food production. However, there is little published on the current status of cow longevity and we hypothesized that a reason may be a lack of standardization and an over narrow focus of the longevity measure itself. The objectives of this critical literature review were: (1) to review metrics used to measure dairy cow longevity; (2) to describe the status of longevity in high milk-producing countries. Current metrics are limited to either the length of time the animal remains in the herd or if it is alive at a given time. To overcome such a limitation, dairy cow longevity should be defined as an animal having an early age at first calving and a long productive life spent in profitable milk production. Combining age at first calving, length of productive life, and margin over all costs would provide a more comprehensive evaluation of longevity by covering both early life conditions and the length of time the animal remains in the herd once it starts to contribute to the farm revenues, as well as the overall animal health and quality of life. This review confirms that dairy cow longevity has decreased in most high milk-producing countries over time and its relationship with milk yield is not straight forward. Increasing cow longevity by reducing involuntary culling would cut health costs, increase cow lifetime profitability, improve animal welfare, and could contribute towards a more sustainable dairy industry while optimizing dairy farmers' efficiency in the overall use of resources available.

Keywords: animal welfare; cattle husbandry; cow longevity; productive lifespan; profitability; sustainability.

Figure 1

Change over time of the top four culling reasons based on the total number of cows culled with a known reported reason in Canada between 1997 and 2019 [16].

Figure 2

Schematic representation of the life of a dairy cow according to a chronological sequence of key events (conception, birth, weaning, first calving, and culling/death) that prompt a change to the different life status (fetus, calf, heifer, and adult cow) and respective life stages (fetal, early, and productive life). The length of the arrows is proportional to the duration of each status and stage as seen in the province of Quebec, Canada [24].

Figure 3

Top 10 high milk-producing countries based on total milk production averaged over the years 2016 to 2018. Columns represent the averages followed by the standard deviation (error bars). The list of countries is limited to those for which we were able to provide sufficient and reliable data on the length of productive life. Data sources are provided in Table A1.

Figure 4

The average milk yield (kg) per animal from the top 10 high milk-producing countries over the years. The list of countries is limited to the world’s top high milk-producing countries for which we were able to provide sufficient and reliable data on the length of productive life. Data sources are provided in Table A1.

Figure 5

The length of productive life (year) of dairy cows from the top 10 high milk-producing countries on different decades. The relative width of each box per country within decades represents the number of observations available to generate it. The wider the box, the more observations were available. The list of countries is limited to the world’s top high milk-producing countries for which we were able to provide sufficient and reliable data on the length of productive life. Full circles (•) represent values above or bellow the interquartile range. Data sources are provided in Table A1.

Figure 6

Relationship between the concepts of profitability, non-productive and productive life stages of dairy cows for a more comprehensive definition of cow longevity along with proposed metrics representing each respective concept.