DAIRY COWS NEEDS

Wanganui Chronicle, Volume 74, Issue 192, 15 August 1931, Page 20 (Supplement)

DAIRY COWS NEEDS

MINERALS IN NUTRITION. .A line, critical review of the position of research in regard to the mineral requirements of dairy cattle has been pre pared by Mr J. A. Crichton, M.A., of the Rowett Research Institute, and has been reprinted from the Journal of Dairy Research. The paper deals with the role of minerals in nutrition, with their special importation for dairy cattle, with the secretion of the mineral constituents of milk, with the balance of minerals, with requirements for growth, and, finally, with the effect of deficiencies on yield, reproduction and health. Mr Crichton points out how the feeder of dairy cattle to-day is striving 1 to obtain more rapid growth in young cattle and more milk from cows in a shorter space of time. Strains of animals have been bred for rapid production necessitating the use of foods richer in constructive materials, such ~s calcium and phosphorus. He reminds us that with this speeding-up of production has come an increased use of j , concentrates or commercial by-products.• ’which, “because of their nature and j previous treatment, are usually badly i balanced foodstuffs.' 1 The discussion of data with regard ’ to the balance of minerals in the lacta-; ting animal is very iLtercsthig, and' would tend to support the view that, with heavy milking cows, ar. any rate, the comparatively high amount of phos. phorus present in artificial diets cannot be relied upon to supply all the phosphorus needs of the animal. The work of Meigs, for example, demonstrates that the continuous loss of calcium will cause a loss of phosphorus, even though the ration may contain plenty of assimilable phosphorus. Bone tissue is mobilised to supply calcium, and the phosphorus of the bone is liberated at the same time. This may be stored temporarily in the soft tissues, but must ultimately be lost. . . Mr Chrichton expresses the opinion that, from the available data affecting the balance of calcium and phosphorus, one -would be warranted in concluding that, with any given milk yield, factors tending to reduce the loss of these dements are (1) a high intake of calcium and phosphorus in the food; (2) a suitable ratio of calcium to phosphorus in the gut; (3) a vitamin found in cod-liver oil, in green food, and to a varying extent, in forages when freshly-cut or cured with the minimum exposure to weather: and (4) sunlight.