Experience early in life affects voluntary intake of blackbrush by goats

Abstract

Low nutritional quality and high levels of condensed tannins adversely affect voluntary intake of blackbrush (Coleogyne ramosissima Torr.) by goats. We studied: (1) how consumption of blackbrush or alfalfa pellets by young goats affected their consumption of those foods later in life, and (2) whether previous ingestion of blackbrush or alfalfa pellets affected the excretion of condensed tannins and total phenols from blackbrush in urine and feces, production of proline-rich proteins in saliva, excretion of nitrogen in feces, and mass of the liver, kidneys, parotid glands, and reticuloramen in goats. From 6 to 26 weeks of age, experienced goats were exposed to blackbrush, while inexperienced goats ate alfalfa pellets. Following exposure, both groups were offered older-growth blackbrush twigs (OG) or a choice between OG and current season's blackbrush twigs (CSG). A similar feeding trial was repeated nine months after exposure, and, in addition, both groups were offered a choice between OG ad libitum and alfalfa pellets at six levels of availability. Immediately after exposure, experienced goats ingested 95% more (P < 0.01) OG per unit of body weight than inexperienced goats, but both groups rejected CSG. Nine months after exposure, experienced goats ingested 27% more (P < 0.01) OG than inexperienced goats. Experienced goats ingested 30% more OG than inexperienced goats at every level of alfalfa pellet availability. The fate of condensed tannins and total phenols was similar for both groups, but experienced goats excreted 63% more (P < 0.05) uronic acids per unit of body weight. Neither experienced nor inexperienced goats produced proline-rich proteins in saliva. Experienced goats excreted 32% more (P < 0.01) nitrogen in feces per unit of nitrogen ingested than did inexperienced goats. The mass of the reticulorumen was 30% greater (P < 0.05) for experienced than for inexperienced goats one month after exposure, but did not differ 10 months after exposure. The mass of the liver, kidneys, and parotid glands did not differ between treatments. The results show that experience early in life can have profound and persistent effects on consumption of diets high in chemical defenses and low nutrional quality. The results also suggest that several physiological and morphological factors are involved.