Effects of Intraruminal Saliva Flow on Feed Intake in Goats Fed on Alfalfa Hay Cubes

Abstract

Research was carried out to ascertain whether or not the volume of saliva flowing into the rumen regulates dry forage intake in ruminants. Goats with a parotid fistula were fed roughly crushed alfalfa hay cubes, concentrated beef cattle feed and NaHCO 3 twice daily (10:00-12:00, 16:00-18:00). Except for the days on which experiments were conducted, the animals were free access to drinking water. The animals were intraruminally infused every day prior to the morning feeding period with parotid saliva collected from the parotid fistula over a 24 h period. The present experiment consisted of three treatments, non-infusion (NI), intraruminal infusion of parotid saliva (RSI), and intraruminal infusion of warm water (RWI). In the RSI treatment, approximately 4-5 kg of parotid saliva (280-290 mOsm/l) collected over a 24 h period was intraruminally infused 1 h prior to the commencement of morning feeding. In the RWI treatment, parotid saliva was substituted for warm water (36°C). After infusions, the animals were fed on roughly crushed alfalfa hay cubes for 2 h. During feeding, eating and saliva secretion rates were measured. Blood samples were also periodically collected from the jugular vein. After 2 h feeding, water intake was measured for 30 min. These measurements were used to define thirst levels. On the day of the experiment, the animals were not access to drinking water during the morning feeding. It is thought that rumen fill in RSI and RWI treatments was higher than the NI treatment. In comparison with the NI treatment however, cumulative feed intake increased by 39.3% with RSI treatment and by 45.9% with RWI treatment after completion of the 2 h feeding period. After 2 h feeding, thirst level in the RSI treatment showed only a 10% decrease compared to the NI treatment, but thirst level in the RWI treatment decreased 49.8%. Despite the significant differences in thirst levels between RSI and RWI treatments, the cumulative feed intake in both treatments was similar. When comparing accumulated saliva secretion volumes 2 h after feeding, volumes in the RSI treatment were significantly 35.9% lower than the NI treatment while volumes in the RWI treatment were unchanged. However, the volumes of saliva and fluid flowing into the rumen were greater in both RSI and RWI treatments when compared to the NI treatment. The results indicate that the amount of saliva flowing into the rumen is a factor regulating feed intake in ruminants fed on dry forage.

Changes in single‐unit activity in the ventromedial hypothalamic nucleus of goats during feeding

“…As a result, their feed intake was 45.9% larger than that in non‐infusion treatment, and this increase in feed intake was observed during the first half of the feeding period. The increase in feed intake during the first half of the present experiment corresponds to the results of the experiment conducted by Sunagawa et al . (2002).…”

“…The changes in eating rates in this experiment are similar to the results of experiments conducted by Prasetiyono et al . (2000) and Sunagawa et al . (2002) on goats.…”

“…Thus, in order to clarify whether the VMH neurons in ruminants play a role as a satiety center, recording neuronal activities in the various conditions of feed intake changes is indispensable. With regard to changes in the feed intake, it is reported that the feed intake in goats increased when an excessive amount of warm water was infused into the rumen (Sunagawa et al . 2002).…”

An intravenous replenishment of salivary components decrease water intake and increases feed intake in freely drinking large-type goats fed on dry forage

“…Intraruminal infusions of hyper-osmotic NaCl, polyethylene glycol-400, sodium acetate, or sodium propionate increase rumen fluid osmolarity and decrease feed intake (Grovum 1995). On the other hand, when the ruminal fluid osmolality was decreased by the intraruminal infusion of an excessive amount of warm water (39.88C) in sheep fed alfalfa hay cubes, feed intake increased 30% (Sunagawa et al 2002). It is thought that the changes in ruminal fluid osmolarity are sensed by the osmoreceptors in the rumen wall and these signals are then transported to the central nervous system affecting feed intake (Leek and Harding 1975).…”

“…When ruminants commence feeding on dry forage they secrete copious volumes of parotid saliva (Sato 1975;Sunagawa et al 2002Sunagawa et al , 2003, and large amounts of fluid and NaHCO 3 move from the circulating blood into the rumen in the form of saliva. Blair-West and Brook (1969) found that sheep fed lucerne chaff once a day showed a marked reduction in plasma volume within 15 min of the commencement of feeding.…”