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Monday, 14 July 2014
About grazing behavior and genetics.
It's one of those lovely wet and damp Irish days. These new lambs I bought recently are surely something. I have to say that even being so small and young they graze so much better than their distant inbred cousins, the dreaded Friesians.
Those East Friesians are hopeless. Get one if you want a pet sheep, because they are totally sweet and tame but stay well away from them if you want something to graze that little bit of waste land you have on the farm. Jeez they are hopeless. They won't touch anything that looks different from lush, green, tasty, fat grass.
On the other hand, the F1 crosses Lacaune x Friesians lambs are all over the place, on the ditch, on top of the brambles, inside the gorse, within the reeds, you name it, you'll find a lamb eating it. It's a pleasure to look at them gnawing at pretty much anything belonging to the plant kingdom. Being F1 crosses they also conserve that tameness typical of the "Hopeless Friesian sheep".
Another thing they do differently is looking for shelter. They will pick the best spot, while the Friesians look like someone trying to protect himself from rain with a leaf.
Ah! do I love genetics!
Fitness is what you loose first when you apply artificial genetic selection to animals. The reason is simple, there is no longer any natural selection pressure to keep there those genes badly needed to survive and thrive in nature, where there is no one to protect you from predators, to supply you with plenty of food and to provide you with shelter and clean water.
The more you push selection for a certain trait, the more you lose fitness in the population.
The exact definition of fitness is the capability of an individual to reach sexual maturity and generate fertile progeny. Basically the capability of passing down your genes to following generations, and of course it has a meaning only in wild and feral populations, in fact domesticated animals cannot choose who will reproduce, their owner is the one to decide who is fit to reproduce. Nevertheless they conserve a certain degree of fitness. An extreme example of this is the Bulldog, where fitness=0. Bulldogs are totally incapable to copulate because they have been bred so wrongly. When they manage, they cannot give birth without a cesarean.
It also depends on the criteria you use for selection. Nowadays selection is carried out with a bit more insight compared to the '80s when a single trait was pursued (quantity of milk as opposed to weight at 60 days). So nowadays you find inside genetic indexes also good things like "leg conformation", "udder shape", "feet index" and so on, all traits that have a positive effect on the fitness of the animal.
This also means that you cannot push as much for "milk quantity" anymore, but that's ok, because that little bit extra came at a big cost in terms of health and animal welfare.
So, Friesians have been selected with very little in mind in terms of fitness and very much towards the one goal: lots of milk, because they were traditionally reared in small flocks, housed and well fed. Furthermore there is no tradition of cheese making from sheep cheese in Friesland, so milk is particularly watered down (little solids in it).
Lacaune on the other hand, have been selected in France, with an eye towards fitness and lamb weight. They are reared on marginal land (Roquefort-sur-Soulzon), hence they need to be able to feed on rough material and thrive in Mediterranean semi-arid conditions. Furthermore their milk is traditionally used for cheese making (Roquefort) and is produced in volumes slightly smaller than Friesians' but with more solids, which is what you need if you make cheese. You cannot make cheese with water!
It's nevertheless quite shocking to see the difference with the purebred Friesian lambs I had last year. Long live the Lacaune cross!!