Maatalouden tutkimuskeskus, Kotieläinhoidon tutkimuslaitos, Tikkurila
The present study is a continuation of previous investigations (3, 4) in which trials were carried out on the mineral consumption of milk cows and heifers on pasture. In 1959 four trials were carried out with cows (Ayrshire breed) and four with heifers; in 1960 three trials were performed with each group. All of the mineral fodders were freely available to the animals under covered feeding troughs. The mean weight of the cows in 1959 was 507 kg and their mean age 6.1 years; in 1960 the corresponding figures were 522 kg and 5.8 years. Tables 1 and 2 present information on the cows used in the trials and Table 4 gives data on the heifers. Trials in 1959. Results from these trials are shown in Tables 3 and 5. In Trial I (8/6 —8/7) the cows were divided into two groups, high producers (A) and low producers (B). Group A grazed on a pasture dominated by meadow fescue and timothy, whereas the pasture of Group B was mainly a cocksfoot-meadow fescue pasture. Those cows whose feed requirements for milk production were over 7 feed units received supplementary concentrates in the form of oatmeal and dried molasses-beet pulp. In this trial the low-producing group (B) consumed more mineral fodders excluding common salt than the high-producing group. (Compare Trial I, 1960). The presence of 50 % monosodium phosphate in the fodder mixture made it palatable to the animals. In the case of the heifers, their mineral consumption with the exception of common salt was greater on the average than that of the cows. In Trial II (8/7 —7/8) the animals were given fodder salt mixtures V and VI, bone meal and common salt. Mixture V was preferred to the cows, evidently because of its 41 % content of disodium phosphate. In general this salt is not as readily eaten by cows as is monosodium phosphate, but in Mixture VI the content of monosodium phosphate was too low (only 15 %) to make this mixture expecially palatable to the cows. The heifers, however, consumed more of Mixture VI than V. In Trial III (7/8–26/8) limestone and chalkstone were compared with one another. The cows ate neither of these and the heifers only slight amounts, so that there was scarcely any difference in the palatability of these two fodders. In Trial IV (26/8–25/9) the poorly-tasting Mixture I was given additions of 10 % dried molasses- beet pulp, 10 % oatmeal or 10 % wheat bran. In the case of the heifers, the latter fodder was not used. The additions made the mixture more palatable to the animals, but the increase in consumption was evident mainly during only the first 10 days of the trial. Since the cows otherwise received large amounts of concentrates during this trial, this fact may explain why their mineral fodder consumption soon declined. In this same trial comparisons in the consumption of fine and coarse salt were made. The cows were found to prefer the fine salt. Trials in 1960. Results of these trials are shown in Tables 6 and 7. In Trial 1 (30/5–9/7) comparisons were made between the fodder salt mixture IV (50 % monosodium phosphate, 40 % dicalcium phosphate) and monosodium phosphate. The animals ate the latter much more willingly than the former. If, however, monosodium phosphate is not available, the cattle eat large amounts of the former salt mixture, as was the case in Trial I in 1959 and Trial III in 1960. In this trial the high-producing cows consumed more total minerals than the low-producing cows. In Trial II (9/7– 18/8) common salt was not given separately as in all the other trials, but it was prowided in the fodder salt mixture VII which contained 29.6 % NaCI. This mixture was otherwise similar to the poorly-tasting Mixture I. Cattle on pasture desire to eat common salt, and if it is not available as such, they will eat the fodder mixture which contains it most abundantly. Thus in this trial Mixture VII was preferred to Mixture I. The consumption of NaCI, however, was smaller than in the other trials. In Trial III (18/8—17/9) comparisons were made between limestone and dolomite limestone and in the case of cows also between fine and ordinary common salt. The cows consumed equal amounts of each of the two fodder forms, whereas the heifers consumed more limestone than dolomite limestone. Table 8 presents summarized data on the trials carried out in the years 1957–60. During the trial period the plant composition of the pastures was approximately the same, and that of the heifers was the same pasture in all years (its clover content, however, decreased and its weed content increased). Cattle on pasture consume mineral fodders which vary widely in quantity; their consumption depends mainly on the kind of mineral fodder. The consumption of calcium by cows varied between 1 and 26 grams, that of phosphorus 1— 29 g and that of sodium 9–29 grams. Of the fodders containing calcium, limestone, chalkstone, dolomite and dicalcium phosphate are poorly-tasting to cows, whereas bone meal is preferred by them. By mixing for example monosodium phosphate with poorly-tasting mineral fodders, they become more palatable and the cattle will eat them readily. Heifers eat more of the above-mentioned poorly-tasting fodders than cows. Of the phosphorus-containing fodders, monosodium phosphate is most favored by cattle. Its quantity in the fodder mixture has a direct effect on the palatability of the mixture. Phosphate fodders of moderate palatibility are bone meal and disodium phosphate. Dicalcium phosphate is eaten least willingly by cattle. Cattle want to eat common salt on pasture. If the mineral fodders contain abundant sodium phosphates, the consumption of common salt is less because of the presence of sodium in the fodder. In this case the total quantity of sodium consumed is greater than when NaCl as such is the only source of sodium. If common salt is not provided separately, but is mixed with fodders containing principally limestone and dicalcium phosphate, the total consumption of sodium chloride remains small.
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