Recent advances in the central control of intake in ruminants.

Neuropeptide Y (NPY) is a strong stimulant of feed intake in sheep as well as in rodents. The information available indicates that it functions in vivo in the modulation of feeding within the central nervous system, more specifically, within the hypothalamus, and probably within the paraventricular nucleus. Injected NPY can override a variety of satiating factors, including those arising from normal feed intake, artificial distension of the reticulorumen, and intraruminal infusion of sodium propionate. Even so, these satiating factors are able to reduce feeding in the face of at least one dosage of exogenous NPY. Neuropeptide Y has specificity in regard to ingestive behavior in rats. It stimulates feeding and drinking but does not alter grooming behavior. It also preferentially enhances carbohydrate appetite. The possibility that specific appetites are influenced by NPY has not been investigated in ruminants. Finally, further investigations of NPY should enhance our knowledge of feed intake and energy balance regulation and its linkage with reproductive physiology.