PHOTO: TED PROBERT
BREEDING ▶▶▶
Which breeds perform best on pasture?
A look at the latest findings on which breeds perform best on pasture, as average global temperatures rise and the number of extreme heat days increases.
BY TREENA HEIN, FREELANCE CORRESPONDENT G
F1 Jersey-Hol- stein progeny are going to be pretty dark in coat colour, which absorbs more heat. But overall, crosses are best in terms of performance on pasture.
lobal warming is a big worry for dairy farmers around the world, and there is therefore increased interest in which cow breeds perform better with pasture-based systems. These types of dairying
are very common in countries such as New Zealand and Ireland, but are also used in many other parts of the world, including other European countries, Canada and the US. It’s true that nutrition can play a role in helping cows with- stand heat stress, but genetic performance on pasture is receiving more and more attention. And while there may not be extensive research on the differences between cattle breeds for pasture performance, Ted Probert, retired exten- sion dairy specialist with University of Missouri, notes that these differences are quite evident in practice. In an extension article, Probert explains, however, “No single ideal pasture-based cow exists. Dairies that use grazing do so differently, and therefore the ideal cow will not be the same for all dairies.” Looking back over the decades in terms of genetic progress
over time, Probert observes that milk yield of individual cows has been a high-priority breeding trait in the US dairy indus- try. That focus has led to a slip in reproductive efficiency over the years (a lengthening of the average calving interval). Probert explains that in pasture-based systems, particularly seasonal dairies that use “batch” or “window” calving, lowered reproduction efficiency can be a major problem. “In these systems, it is imperative that a high percentage of cows in the herd return to oestrous cyclicity and breed back within a time that will keep them on the desired seasonal calving schedule,” he says. Jerseys are among the dairy breeds that offer a shorter calving interval, but Jerseys and their related cousins are also small, and smaller animals can generally dissipate heat better than larger ones (in the case of cows, the Holstein). Their pasture performance is therefore superior. Probert adds that smaller (less heavy) cows also tend to do less damage to pasture, especially during wetter weather. In addition, Jerseys and other similar breeds sport lighter coat colours, which do not absorb sunlight to the same extent as darker coats, keeping the cow much cooler.
The Jersey – number one? Jerseys were developed on the British Channel Island of Jer- sey. The Jersey is a small cow with a lighter brown coat and white markings. The number of Jersey herds has greatly in- creased in Canada and the US in recent years due to their pasture performance, higher milk fat and protein percentag- es (ideal for cheese making), shorter calving lengths, ease of calving and other factors. It’s also a highly-productive breed, with some cows giving over ten times their own weight in milk per lactation. Probert reports that in Missouri, which has a long pasture season from March to early December, pasture-based dairy herds are made up of about 10% Jersey, with some Guernsey and Brown Swiss herds. But the vast majority (80–90%) of dairy cattle out on pasture in Missouri are Jersey-Holstein crosses. In a recent master’s thesis completed at the University of North Carolina, Jason Graham assessed crossbred dairy cattle for heat tolerance in pasture-based systems. He writes that most breeding for heat tolerance has focused on purebreds
10 ▶ DAIRY GLOBAL | Volume 9, No. 3, 2022
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