Rhyme or reason?

[frustrated1]

Just brought a heifer back from the vet with a c section. Great big calf. The heifer that calved last nite had such a small one I got her in to check for the twin,not there. Same type of cow, same bull, same feed. One day apart. Between the two of them they averaged normal weight, but what a difference in birth weight. What's up with that? The other heifers have been having average sized calves, hopefully that continues. Haven't had a section for a few years now and sure don't want to know what they cost.

[nerves]

It's called good old mother nature throwing a curve ball at us. Genetics is always about percentages. My C section here in Southern AB cost me $340.00.

[PureCountry]

The last time we had a c-section was February, 1991, and it cost $185, according to my Fathers' entry in our old calving logs. Now, the same clinic - under different management - charged my neighbour $375. Inflation's a real bitch.

[frustrated1]

Guess that makes sense, seems to me the last one I had was about $240? Whatya do? Can't just shoot her. At least the big galloot was up nursing now, beats having a dead one. Put the next one in the barn now too, hope we're back to normal weight.

[cowman]

I wonder if it has to do with how long a certain cow carries her calf? From using AI it is rather amazing the variation in gestation lengths you sometimes get? It always seems those long overdue calves are just about always bulls? I remember once we were calving out a group of Hereford heifers bred AI to a Longhorn and one heifer went 14 days over! Her calf weighed 114 lbs. and he was definitely a Longhorn! The rest of the calves were in that 60-70 lb. range.

[boone]

Cowman: So was the bull calf a lazy breeder too? Or was he more of the slow roasting type?

[boone]

I think cowman has hit this one one the nose. We are working with the gestation length suggestion and find it to be key to birth weights, however when you are looking at another 20 odd traits in a new herd sire, sometimes things get overlooked.

[amazed]

I would say in this case the genetics between the females could be the difference. The post said the same "type" of cow but that does not mean it had the same genetic makeup as the others that have calved.

The cow provides over 50% of the influence of calf size between 50% of the genetics plus the environment in which the calf developed. The bull only kicks in half of the genetics.

Having said that if all things ARE equal chalk it up to bad luck and get rid of the heifer and her calf.

[pandiana]

As has already been pointed out, many things affect birthweight, several of which are not related to genetics.

Weather, feed quality and heavy feeding in the last trimester certainly influence birthweight. However, as you pointed out this is less likely to have been the case as they were fed together as a contemporary group. Nonetheless, genetics are not entirely ruled out as we all know some animals have a higher level of feed efficiency than others.


Genetic influences include both the cow and the bull.
We have weighed our cowes and their calves post partum for over 11 years and just as you would expect, big cows make big calves, small cows generally make small calves. In general we expect, statistically about 6.8% of the dam weight /- about 1.5%. Cows usually calve easily up to about 8.5%. 9% is getting into the pull zone and =>10% is usually a C-section. Of course, these observations are somewhat academic as they don't help predict who will need help but do help in determining 1. whether difficult births are attributable to one bull producing big calves or 2. whether the cow typically likes to produce big calves. It also helps to put into perspective that 130 lb birthweight is a perfectly acceptable weight for a 1900 lb cow whereas a 90 lb calf out of a 1000 lb first calf heifer is quite big at 9% of her body weight. For a herd of 1450lb cows an average birthweight of 98.6 lbs (range 77 to 120lbs)would be expected to be in the safe area.

I agree that gestational length will influence birthweight. It is estimated that calves in utero will gain as much as 2 lbs a day towards term. It wouldn't take long for this to become a problem. Some breed associations are now publishing a Gestation Length EPD. Bulls that are trait leaders for short gestation do usually produce smaller calves. Not always, however, indicating that other factors (cow genetics, feed, weather, etc) are an influence.

[greybeard]

In my opinion a bull will add or subtract plus or minus 10# of birth weight depending on it's EPD . The rest is due to the cow or environment.
Every time I buy groups of heifers I have an odd big calf. Better if I breed them myself as some sellers don't seem to use very good bulls. I also often seem to get some dinky little calves. I suspect this is due to " stacked" small birth weight . The heifers were probably out of heifers bred for small birth weight. They usually get culled out as they don't have much performance.