Rhyme or reason?

[Horse]

Back a few yrs ago when I had about 35 cows and 1 bull. one yr I dont think I had the puller off the wall and the next yr I bet I pulled nearly half of the calves out of same bull and same cows and I dont think there was that much difference in the feed.So explane that to me.

[frustrated1]

Who'd have thought one small thread of venting would generate such a response. Never ceases to amaze me the knowledge and insight these chats produce. Most always find them interesting if not productive. Thanks all!

[cowman]

Horse I have always found a dry year produces hay/feed that really makes those calves grow in the cows. A feed test shows feed value is the same so what can you do? After all the "experts" are never wrong, right?
Another thing affecting calf weight is the barometric pressure. When one of those big highs sets in the cows all quit calving. When the low comes in away they go again....a low usually means a storm...and we all know how cows just love to calve in a storm?
Considering some of these strong highs can last two weeks and that calf continues to grow everyday, it is not unrealistic to figure we'll get a bigger calf?
Anyone who has done a bit of AI knows how this barometric pressure thing works. When a high is dominating the picture no cows are around but just let a low move in and the whole pen is bulling!

[pandiana]

I never really thought about short term changes in weather (barometric pressure). This would be interesting to pursue.

On the other hand, climate and weather do have significant effects on birth weights although I am not sure anyone knows exactly why.

Those of us with some experience of calving on grass will note a big difference in calving ease and birthweight when compared to January-February calving with bulls and cows being the same. Also, cows that stay out on pasture through November, December and sometimes January, also appear to have smaller calves. This phenomenon can also be seen in many American AI sires, with birthweights in the 80-90 lbs that consistently sire 95-105 lbs in our area.

[grassfarmer]

Cowman, I don't know if the weather affects calf birthweight but I certainly recognise the onset of a low pressure front prompting births. We found that even more pronounced among sheep than cattle.
Pandiana, I assume excercise will be the biggest contributing factor in your above scenario's. I always make my cows walk a good distance to and from water all winter. This winter for the first time I've kept my cows entirely away from the corrals as they will be calving from mid April onwards. Cows are healthy, clean coats and have used no bedding so no manure to haul out. I won't go back to having cows in the corrals again.