I don't know what other people do, but I report the actual BW no matter when it was born. As I commented on here in the past, I have had two sets of ET calves from the same matings, and implanted on the same day, go 18 days from the first calf born to the last calf born from these embryos from the same flushes. I have always reported the actual BWs. I also know there is a fairly wide variation in gestation lengths within a breed from different blood lines. For that reason, I do not think you can just look at a gestation chart and expect a female to calf on the date the chart shows.
Here is a couple of examples in my own herd: Years ago, when we were running two Irish imported herd sires, Highfield Irish Mist and IDS Duke of Dublin, I kept track of gestation lengths of all my calves from each bull. On average Irish Mist calves arrived 8 days earlier than Duke of Dublin calves.( Mist was a straight Leader bred sire and Duke was from the Improver line, but his dam was leader bred.... I don't know if this is a a factor or not) Once I figured this out, I never hesitated to use Mist on heifers. Even though I never had any calving issues from Duke of Dublin, his calves were heavier at birth and I did not use him on heifers. I know some people did, but I never did... simply because I feel it is very important to have as uneventful as possible birth from a heifer's first calving. Despite what some people think, I feel there are lots of excellent choices to breed your heifers to, that will provide an uneventful first calving experience. I also realize there are exceptions to every rule, and while I have no firm facts to prove this, I expect there are some bloodlines in the Shorthorn breed that are reducing the ability of true calving ease in the females from these bloodlines. Maybe that is why I do not feel that there is as much a calving issue in the Shorthorn breed as many others do. I have just come in from checking my cows and heifers and my 18th calf is on the ground. So far the hardest thing I have had to do in the first 18 calves was make out the ear tag and put it in the calf's ear.... and weigh it. I'm not suggesting for a second, that I know the answers, but I do think we can all eliminate many calving issues, if we use some common sense along with some research in the bloodines we are going to use.
The easiest calving bull I ever used was a son of Highfield Irish Mist, named HC Mist's Return 13R. He was a full Irish bull that I used on my heifers naturally for 4 years. In that 4 years, I only assisted one calf from a heifer, and that was one that had a foot back. Mist's Return also has the shortest gestation length I have ever seen in my herd, and his calves averaged 274 days gestation. If you were just looking at a Beef gestation table based on 283 day pregnancy, you would probably miss every calf being born from Mist's Return because they would be born, on average, over a week earlier than this. I am finding that his daughters are showing the same traits so I am fairly certain that gestation length is not only determined by the sire, but also by the dam. In the case of ET calves, I am also suspecting that the recip mother can affect this as well. I have one recip cow, who is now carrying her 7th ET calf. In her 6 previous ET calvings, she has been the last recip to calve from embryos implanted on the same day. She is in fact, the cow that had both of the ET calves that were 18 days after the first born. I find this to be interesting stuff, and I wish there was more research done on this. As usual, the sire used gets all the blame for overdue calves, and that may be true in some cases, but I don't think it is the only thing affecting this.
It may be premature, to say that I have another calving ease bull, but the first indications are suggesting that. I bred all my heifers to an ET son of Pheasant Creek Leader 4th last year, and I have only had 3 calves from these heifers so far. I had 5 Leader 4th calves from this flush of B Good Red Sue 1P, and these calves all came early. Red Sue is a Charmer X Trump, which are two bloodlines not necessarily considered to be calving ease lines, but I have never had any problems from my limited use of either of these. I kept HC Bar Code 13X to use in my herd, because he had a 75 lb BW and I loved his smoothness and easy fleshing ability. As I said, 3 heifers have now calved and so far I haven't seen one born, and the 3 calves averaged 78 lbs at birth. The first of these heifers calved on Feb 2nd and she is in heat today, so that is exactly what I like to see from first calf heifers. I will know a lot more about how Bar Code is going to calve in the the next few weeks as there are about 28 more coming.
All 5 of the Leader 4th ET calves came earlier than the due date shown on the 283 day gestation table. So, I record the actual BW regardless of whether they were early or late. IMO, how do we determine the correct BW? If we deduct some pounds from an over due calf, should we also add pounds to the calves that come early? As far as I am concerned a 283 gestation table is an estimate based on breed averages. It is probably the top of the bell curve so to speak. There are going to be calves born on either side of this, and some of it is related to genetics, and I'm pretty sure there are probably some management and environmental factors that affect this.
I wish we could have actual breeding dates on all our females so that we could also document gestation lengths with our BW information. Maybe if we could even record the gestation lengths from the ones we do have breeding dates on, maybe we could ... in time, start to see some trends.... but then we would also have to rely on breeder's honesty, and that could be a limiting factor in some cases as well.
