The use of the "summer to winter ratio" index, to assess the effect of summer heat stress on the performance of dairy cows in different regions of the USA

Dear Dr. Flamenbaum
Happy new year for you and your loved ones and for the colleges in engormix. Thank you for the correction and the valuable work on the heat stress on the dairy in hot areas.

Dear Dr Israel Flamenbaum, I have a question: why when the effects of heat stress on cattle are analyzed, production values and productivity values are taken as the basis of the variables? For example, when we analyze milk production, the value taken is produced by a cow, when, I think that the right thing would be to take the VALUES OF PRODUCTIVITY as milk production/weight of the animal. A cow that produces 28 kg of milk and weighs 420 kg is not the same as a cow that produces the same 28 liters of milk but weighs 320 kg under the same conditions of heat stress and with the same feeding.