| Abstrakt: |
Thirty-two female Holstein cattle with an average age of 3 to 4 months and an average initial weight of 105 kg. were divided into two replications by weight and assigned to 16 treatments in a factorially designed experiment. The overall experiment was terminated when the animals reached an age of 7.5 years. The four levels of fluorine used were 10, 28, 55, and 109 ppm on a moisture-free hay basis; computed according to dry matter intakes, the fluorine levels were 12, 27, 49, and 93 ppm. Two quantities, 1.0 or 3.0%, of a Ca-P mineral mixture were incorporated in a pelleted grain concentrate. Two or four pounds of the concentrate were fed during the first two metabolism trials. During the last three trials the concentrate levels were raised to 0.75 or 1.0 lb. daily per pound of milk fat produced weekly. Five digestion and metabolism trials were conducted, two before and three after the animals began to lactate.Fluorine consumption had no significant effects upon feed intakes, digestion coefficients, or absorption of nutrients during the first two trials before the cattle began to lactate. During trials three, four, and five, however, the animals ingesting 109 ppm F consumed less feed than the animals on the lower levels. Because of this lowered feed intake, the amount of nutrients absorbed was also decreased in most of the animals on the 109-ppm F treatment. This effect was also evident in some of the animals receiving the 55-ppm F level. Digestion coefficients for many of the nutrients increased slightly with each higher level of ingested fluorine, although these increases were not statistically significant.The higher quantities of concentrate tended to result in higher energy intakes and higher amounts of absorbed energy as measured by digestible and metabolizable energy. The high concentrate level did not result in significantly less fluorine retention. Likewise, the higher level of Ca-P mineral did not reduce body retention of fluorine.Apparently the effects of fluorine on the digestion and absorption of nutrients are secondary, since it required nearly 2½ years for the higher levels to influence these physiological functions.The results of this experiment indicate that during a 7-year period of the life of a dairy animal, the tolerance level of fluorine as sodium fluoride is between 28 and 55 ppm on a dry hay basis or between 27 and 49 ppm on a total dry feed basis. |
