Nutrients required for developing the fetus in dairy cattle
A cow may use feed for five purposes as follows: 1) Maintenance 2) Milk Production 3) Increasing body weight 4) Growth, if not mature 5) Developing the fetus. Feeding standards have been established experimentally for all of these except fetal development. It is customary for feeders to be more liberal in feeding pregnant animals, probably due to the general belief that developing the fetus is more or less a tax upon the maternal organism. Feeders often say that cows in a lean or moderate state of flesh will drop calves larger and healthier than calves from excessively fat cows. This is thought to be due to the fact that the space for the development of the fetus is restricted in fat animals or possibly the blood supply is reduced. The author has seen cows so lean at the time of parturition that for several days following, they were too week to stand, yet the calves were of normal size and healthy. The mother in such cases has drawn upon the materials in the body to supply nutrients for the fetus. The amount required in such cases and in normal cases is hard to determine. In the experiments conducted at this station and reported in this thesis an attempt has been made to measure the nutrients required for fetal development by the changes occurring in the body weight of the mother. The inaccuracy in using body weights as a measure of nutrients used is recognized, yet other than the respiration calorimeter no method seemed more adequate than weighing. It is apparent that these experiments serve to demonstrate only in a practical way the nutrients required to develop the fetus.
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