Factors Affecting Feed Intake and Its Regulation Mechanisms in Ruminants -A Review

Abstract

Feed intake is one of the main determinant factors of ruminant performance. However, it is affected by different sets of factors that can be grouped under three categories; 1) feed related factors (include feed chemical and physical characteristics, associative effects between dietary components, nutrient balance and amount of anti-quality factors), 2) animal related factors (such as physiological status, size and genotype of the animal) and 3) environment related factors (like temperature, housing and prevalence of diseases). Ruminants try to satisfy their nutrient requirements for maintenance and other productive purposes from different feed sources because it is unlikely that feed/s contain the exact amount of nutrients required by animals. This consumption of different feeds to balance nutrient intake by ruminants may lead them to over or under consumption of one or more nutrients. Both under and over feeding are not required by the animals and therefore they should have mechanisms to regulate their intake. Ruminants feed intake regulation mechanisms have been perceived and described differently by scholars—theories of intake regulation. But, these intake regulation theories fall under three categories: 1) physical feed intake regulation—states fill effect from resulted from destination of the gastrointestinal tract causes the animal to stop or start feeding; 2) metabolic or chemostatic feed intake regulation—states the presence of nutrients, metabolites and hormones in the circulating blood signals the animal to stop or continue on feeding); 3) cost benefit model of feed intake regulation—states animals continue feeding to get nutrient they require and stops to avoid the detrimental effect of by-products of metabolism, (free radicals), but this theory have been criticized by different scholars. However, it has been proved that, the different signals in intake regulation are working in integrated way controlled by the central nervous system.