Response of cow's milk composition to changes in environmental temperature : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
The need for greater production of animal proteins in the developing countries stems from two factors. Protein deficiency among growing populations due to a wide gap between production and consumption and the continuing demand for the conventional proteins despite the availability of synthetic substitutes French 1970. Studies with regard to the nutritional properties of dairy products Henry 1957; McGillivray and Porter 1960. McGillivray and Gregory 1962 showed that the (protein) fraction of milk was well balanced in the essential amino acids enchancing their nutritive value. Milk production at the desired levels has not been possible in humid and arid regions of the world due to a variety of technical problems chief of which have been the choice of dairy breeds and the availability of good quality pasture, Payne 1957. Cattle breeds indigenous to these regions are poor milk producers. They are slow developing, late maturing animals with short lactatious, long dry periods and poor milk let down; factors which probably contribute to their higher heat tolerance, a character incompatible with high milk yields Mahadevan and Marples 1961. In the United States of America Red Sindhi and Brahman breeds were used in cross breeding programmes aimed at evolving a heat tolerant high producing dairy breed for the gulf coast areas. The first generation Jersey Sindhi and Jersey Brahman crosses not only produced less milk than their contemporary pure Jerseys, but also lacked persistency and a suitable dairy temperament; which were in fact heritable. Brandon McDowell and Brown 1966. These observations do not preclude however the advantages of cross breeding for higher milk production in the tropics Legates 1966; Salazar 1968. Although early ventures using temperate breeds of cattle for milk production in the tropics have shown results of a disappointing nature Payne 1957, given near temperate conditions found in tropical uplands these breeds could respond well. Trail 1968; Yung Chen Chia 1966.