dyates":t4bnppbr said:
As long as they wean at least 50% of their body weight, I don't care how big they are.
to continue my metabolic weight sermon, my theory (which i think is the next logical step after % of dam weight) is to use a Metabolic Weight Ratio.
Metabolic Weight Ratio = calf weight / dam's metabolic weight
if you look at % weaned and expect 50+% from each cow, you are giving the big cows an unfair shake.
with this rule:
1000 lb cow must bring in a 500 lb calf.
1500 lb cow must bring in a 750 lb calf
the problem is that the big cow has to raise a calf that weighs 50% more and she didnt consume 50% more resources.
1000 lb met wt = 178 lb
1500 lb met wt = 241 lb
the big cow only consumed 35% more resources, but her calf has to weigh 50% more.
if you look at metabolic ratio as a measure of weaning merit, the 1500 lb cow's calf only has to weigh 675 lb to raise the same amount of calf/resources consumed. this would mean that their Met Wt Ratio is the same (2.8 lb of calf / lb of met wt).
say you decide that your cows should wean with a 2.8 MWR:
cow weight |
Met Wt |
calf weight
1000 | 178 | 498
1100 | 191 | 535
1200 | 204 | 571
1300 | 217 | 608
1400 | 229 | 641
1500 | 241 | 675
1600 | 253 | 708
1700 | 265 | 742
1800 | 276 | 773
the weights above show the same "efficiency" regardless of the cow weight.
notice that the 1000 lb cow raises 50% of her weight and the 1800 lb cow only has to raise 43% of her weight to be as efficient.