We have been contacted by a small number of suckler farmers who say that although their cows have scanned well, pregnancy rates in replacement heifers are back. While it is admittedly early to be building a picture of national pregnancy rates in suckler herds, vets are reporting that heifer scanning results were also poor in some dairy herds.
This is a strange turn of events – usually if there are issues, the opposite is the case, with more cows scanning empty than heifers.
There are some indications that, for whatever reason, oestrus may have been suppressed or delayed in heifers on certain farms. On the other hand, farmers are saying that heifers were bulled, didn’t repeat and scanned empty. This points toward embryonic death. But why?
Weight
Cattle weights are back around 20kg on last year in a lot of places. Weight is more important than age when bulling heifers. But while lower weights would explain a delay in puberty and oestrus, unless the animal was seriously stunted she should have conceived later in the season.
In cattle losing body condition, oestrus will be suppressed. Had our heifers been treated too well in the winter – which is entirely possible where silage may have been too good and/or too much meal was offered – they may have built up condition and subsequently began to lose at turnout, or where meals were pulled but turnout was delayed. Yet again, this would cause a delay in oestrus, not suppress it altogether.
Embryonic death
Both a vet and ruminant nutritionist flagged the possibility of nitrogen toxicity leading to embryonic death when queried by the Irish Farmers Journal. That is, where an animal conceived but something caused the embryo to die. After embryonic death, the reproductive cycle is temporarily suppressed. If your scanner is picking up empty heifers that are not cycling, but were served, this could well be your problem.
How?
The grass growth curve for 2016 has been unprecedented – we got nothing at the start of the year and then it exploded. This burst came in the height of breeding season and this grass will have been very high in crude protein. Where animals were taking in more protein than they could handle, there may have been excess urea in the blood, which can be toxic to embryos. Indeed, milk urea levels in dairy herds across the country were very high this summer. Some nutritionists reported that they were forced to pull back supplement crude protein levels in order to prevent embryonic death in milkers.
Both a vet and ruminant nutritionist flagged the possibility of nitrogen toxicity leading to embryonic death when queried by the Irish Farmers Journal
The fact that pregnancy rates in mature suckler cows are good so far could be down to the fact that as they are larger and rearing a calf. Their requirement for protein is greater than in heifers.
The embryonic death theory makes sense – the only common difference from previous years on farms with poor heifer pregnancy rates seems to be the spike in grass growth.
Don’t rule out disease
The main diseases causing embryonic death are IBR, BVD and leptospirosis. Those with poor scanning rates should look at taking blood tests before they rule these out. With BVD and leptospirosis, there will be a waiting game to see whether abortions or PI calves come. With IBR-induced embryonic deaths, there should be/have been a number of incidences of illness in the herd at this point.
It is plausible that those reporting poor scanning results are isolated cases. At this point, all we can do is speculate. However, as more herds are scanned, we will be able to paint a more complete national picture.
Part two: Poor scanning rates in heifers - what should I do?