I am writing this as I prepare to give a talk on crossbreeding in Saskatchewan and it strikes me that often the simplest things we can do in our operations are the most productive. It is possible to use straightbred genetics in the commercial industry and be profitable, and it is even possible to hit specific market targets. It is also possible to roof a house using a monkey wrench as your only tool. The important thing to remember is that there are easier ways to go about achieving the end goal. In the case of commercial beef production that easier way is to use the tool of crossbreeding.
Arguments over the perfect cow are a never-ending source of amusement for cattle producers, but it is a fair comment to say that the perfect Canadian cow is more likely to be a crossbred cow than she is to be a purebred. This is partly due to simple statistical odds (there are a lot more crossbred cows to pick from) but also due to her inherent advantages in longevity, disease resistance, fertility levels and lifetime productivity.
Heterosis or hybrid vigour is defined as the amount by which an offspring outperforms the average of its parents. It is caused by the pairing of unlike genes and tends to have the greatest influence on traits with the lowest heritability such as fertility and disease resistance. There is a variety of reasons for the effects of heterosis, but in essence it boils down to the fact that the whole is greater than the sum of its parts.
Much research has been done on crossbreeding and results show that the crossbred cow ultimately results in higher returns to cattle producers. Recent U. S. research shows an advantage of $75 to $100 return per year per crossbred cow. In essence a crossbred cow results in roughly one extra calf per cow for each cow in the herd over her lifetime. At the maximum potential, heterosis amounts to roughly 60 pounds of extra weaning weight for every cow exposed to a sire.
Another way to look at it is achieving a 24 to 30 per cent boost to your cow herd without incurring a fertilizer or fuel bill and without taking any more of your time. There is a reason that all our protein competition (poultry, pork) comes from crossbreeding systems.
Variation within and between breeds
I often hear that there is as much variation within a breed as between breeds. This is both true and complete garbage. It is true that there is a lot of variation within a breed. For example most breeds exhibit a 100-pound plus range in birthweight. It is also true that breeds are not created equal and more importantly, the genes contained within a breed may not be identical to the genes that control the same trait in a different breed. The other important thing is that the variation within an individual breed may be centred on a different average. For example, there may be 10 points of difference in yield within each of two breeds, however the average yield of one breed may be 55 and the other may be 65. There is as much variation within each of these breeds as there is between these two breed — but they are very different.
The myth of within breed heterosis
I often get into the discussions regarding the use of disparate lines of cattle within a breed to produce heterosis. Unfortunately the best one can do with this approach is to “recover inbreeding depression.” Remember the cause of hybrid vigour is the pairing of unlike genes. By definition, cattle from a breed exhibit breed characteristics because they share many genes in common. Another way to think about it is that a single line within a breed may have been selected for several years, but individual breeds developed over several centuries in isolation. This results in larger differences between breeds and thus heterosis. A really good practical example is to look at the hybrid vigour exhibited by Bos Indicus x Bos Taurus cross cattle (eg: Angus x Brahma). These cattle exhibit tremendous hybrid vigour and have evolved as separate populations for over 1.5 million years.
Complementary genetics is key
In a terminal situation, where all calves are being sold for slaughter, the sire breed can be quite different from the maternal breeds. The sire breed can excel in growth and carcass yield with little emphasis on milk and mature size. This scenario allows us to capture added growth and yield without fear of drastically increasing mature cow size or negatively impacting fleshing ability, as we are not keeping any replacements from the terminal line sires. The use of a