justintime
Well-known member
JTM, I can only speak for myself, but I think you have made a very good point regardiung gestation length. I have never adjusted a birthweight or a birthdate and I think gestation length is one of the most important factors affecting birth weight. Of course there are other factors, but the length of the gestation period can make the difference between an unassisted birth and a hard pull. The Irish bull( HC Mist's Return 13R) we raised that is the easiest calving sire we ever used and he had the shortest gestation length of any bull we have used. I am not certain what all affects the gestation length but it is definitely affected by the sire, as Mist's Return calves are always born at least a week before the 283 day calving tables. I am also wondering if the mother can have an effect on this, as I have seen this especially in ET calves. One two occasions we have had 18 days between the first ET calf and the last one, on embryos from the same flush implanted on the same day.In both cases, it was the same recip cow that was the last one to calve. She has had 5 ET calves now, and she had gone over due with every one of them. Is it something in her genetics that causes this ? If the dam's genetics can affect gestation length, then why is it that our Mist's Return calves are all got short gestation lengths despite the genetics of the dam? We used Mist's Return on our heifers for 4 years and only assisted one birth, and it was a calf with a foot back.
In looking back at my records, GR Rodeo 4000 , the RD son that calved so good here, also sired calves with a shorter gestation length than average. He was also shaped right for calving ease but we never touched a calf from him at birth from cows or heifers. His sons were very similar. In the case of the flushmates, HC Midas 80M and HC Merger 93M, there was 9 days between them at birth. Midas was the easier calving sire of the two bulls, but we never had any problems using Merger on cows.
I often wonder about the gestation length of some of today's cattle with so many people inducing a cow if she goes overdue even a day or two. I have never induced a cow and probably never will ( I suppose there may be a reason to some day, but right now, I can't think of one). I think we all need to be putting more emphasis on gestation length and calving ease rather than just talking about birth weights
I don't have the answers to why some of these cattle calve easier than others with similar pedigrees do. This is not just a Shorthorn issue. Just a few days ago, at our local fair, I was talking with two Angus breeders who are using full brothers from a well known Angus herd, and these two bulls are like night and day in regards to calving ease and birth weights of their calves. These two bulls were pretty high dollar bulls, but they are breeding completely differently. How do you explain this using these full brothers EPDs?
Some of the differences could be management related, but both run their cow herds in very similar manners. I don't think there is a simple easy answer to some of these questions. Genetics are often complex and we have all seen major differences between some full sibs born in different years. I suspect there can also be different genetic reasons for why two full sibs will be so different in how they calve.
In looking back at my records, GR Rodeo 4000 , the RD son that calved so good here, also sired calves with a shorter gestation length than average. He was also shaped right for calving ease but we never touched a calf from him at birth from cows or heifers. His sons were very similar. In the case of the flushmates, HC Midas 80M and HC Merger 93M, there was 9 days between them at birth. Midas was the easier calving sire of the two bulls, but we never had any problems using Merger on cows.
I often wonder about the gestation length of some of today's cattle with so many people inducing a cow if she goes overdue even a day or two. I have never induced a cow and probably never will ( I suppose there may be a reason to some day, but right now, I can't think of one). I think we all need to be putting more emphasis on gestation length and calving ease rather than just talking about birth weights
I don't have the answers to why some of these cattle calve easier than others with similar pedigrees do. This is not just a Shorthorn issue. Just a few days ago, at our local fair, I was talking with two Angus breeders who are using full brothers from a well known Angus herd, and these two bulls are like night and day in regards to calving ease and birth weights of their calves. These two bulls were pretty high dollar bulls, but they are breeding completely differently. How do you explain this using these full brothers EPDs?
Some of the differences could be management related, but both run their cow herds in very similar manners. I don't think there is a simple easy answer to some of these questions. Genetics are often complex and we have all seen major differences between some full sibs born in different years. I suspect there can also be different genetic reasons for why two full sibs will be so different in how they calve.