Regulation of food intake in dairy cows in relation to milk production

Abstract

The physiological state of the animal will influence the amount of energy it can utilize and this, in turn, will tend to affect its demand for food. Particularly when the energy concentration of the ration is not high, any effect of the physiological state on abdominal capacity will affect intake, e.g. young, fat or pregnant animals will have a reduced capacity compared to older, thin or non-pregnant animals, respectively. In general, intake of energy will increase with increasing concentration of digestible energy in the ration, but it becomes constant once the animal is able to meet its total requirement. When the energy concentration of the ration is not limiting, an increased output of energy will, in general, be matched by an increased intake. The response may not be immediate however, so that after parturition for example, peak food intake frequently occurs after peak milk yield. Correlations between intake and milk yield are generally low, whereas there is usually a marked relationship between body weight and intake in the lactating cow. Simple equations linking intake to body weight and milk yield are usually quite accurate in the general situation, but rarely of value to predict intake of an individual. More complex equations, though more accurate, are difficult to apply in the practical situation. The relationship between lactation and food intake is examined in some detail. It is concluded that efficiency of utilization of food energy for milk production could be improved by minimizing cyclic variations in liveweight of the cow during lactation. To permit this, methods are currently being examined for manipulating diet composition to enable the cow to consume enough food in early lactation to meet the requirement for milk production. If these methods are successful, it will be possible to feed the cow for constant liveweight by feeding to appetite at all times and altering the composition of the diet to match the energy demand of the cow. Allowance should be made for growth and pregnancy, but fatness should be avoided.