(First published in Beef Supplement, Hamilton Spectator January 2014)
At “Ivanhoe” near Cavendish we have put a lot of effort into breeding high fecundity livestock. We have invested heavily in genetics to improve lambing percentage and calving percentage in the belief that this an important way to increase production efficiency and profitability.
Last year we had 56 cows calving and ended up with 76 calves born. That is, 32% of the calves were born as multiples. This included 2 sets of triplets. This led us to wonder how common triplet births were in cattle. In looking on the internet and in text books, there are several comments from North American sources suggesting the odds of a triplet calving in beef cattle are about 1:105,000, and in dairy cattle figure might be 1:7,500, quite a divergence in the odds, but in any case it is clear that triplets calves are quite rare in the normal cattle population.
In the genetic selection herd (USMARC Twinners, bred in Nebraska) that our cattle come from, 50 -60% of the calvings are multiples with a triplet rate of around 2%. Clearly the genetic selection for increased fertility has been very successful. The weaning weight per twinning cow in these cattle is 160% of the weaning weight of comparable single bearing cows and in the US situation at least the carcasses are very satisfactory. Twinning in normal cattle is reasonably uncommon. The British beef breeds are usually quoted as having 0.5 to 4% twins, the continental breeds, 2 to 6% and dairy breeds 3 to 10%
Coming back to our own cattle last year; one of the cows that produced triplets calved successfully in the paddock and has reared 3 heifer calves without bother. They are shown in the associated photos soon after birth and near weaning. They are destined to be retained in our breeding herd. At 8 months of age they were weaned, weighing 198, 222 and 188 kg (not a very large range!). The mother has conceived again and is due to deliver twin calves this year. The other cow had the first calf in the paddock but then got into a spot of bother, getting cast largely due to paddock topography, and had to be assisted to deliver another calf and to stand up. Later that night she delivered a third calf which was dead (probably mainly because I did not bother to check for a third calf). This triplet set consisted of 2 females and a male, so the females are freemartins and will be sterile and hence they will be sold for slaughter. These were held in the yards for a couple of days to ensure that they mothered up but required no other extra management and the calves weighed 258 and 254 kg at weaning.
Very high calving and lambing percentages are possible with genetics that are available now. In sheep we have the option of the Booroola gene which is a major gene affecting ovulation rate and alternatively in both sheep and cattle, selection programs operating on larger numbers of genes to improve reproduction rates have been successful. In fact it is important that we don’t overshoot the mark remembering that we don’t have precise control of ovulation rate and we have to live with some variability. In cattle 40 -60 percentage of twins and just a few triplets is probably the upper limit at the moment, while in sheep 50 -60 percent twins plus 20 -30% percentage of triplets will probably strain our ability to feed the animals properly. In our relatively favourable grazing environment these percentages can be achieved but this comes at a slight cost of extra management at calving and lambing time and careful attention to feeding during late pregnancy and early lactation.