Effect of intracerebroventricular infusion of urocortin on feed and salt intake in parotid fistulated sheep

Self Cite

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.

Section: Discussionmentioning

confidence: 67%

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

Sunagawa¹,

Nakatsu²,

Nishikubo³

et al. 2002

Self Cite

“…Saliva is continuously lost in parotid fistulated sheep. Despite sheep being trained on a pedal-press system to allow them free access to a 0.6 mol/L NaHCO 3 solution and water, so long as the saliva lost through the parotid fistula was not returned to the rumen, sodium and water appetite in the fistulated sheep markedly increased while feed intake and urine volumes decreased (Sunagawa et al, 2002a). In the present experiment, in order to avoid any harmful influences on the animals, the saliva collected from the parotid fistula throughout the previous day was infused with a bathtub pump via an extension tube into the rumen prior to morning feeding.…”

Section: Blairmentioning

confidence: 99%

Controlling Factors of Feed Intake and Salivary Secretion in Goats Fed on Dry Forage

Sunagawa¹,

Ooshiro²,

Nakamura³

et al. 2005

The purpose of this research was to determine whether or not feeding induced hypovolemia (decreases in plasma volume) and decreases in plasma bicarbonate concentration caused by loss of NaHCO 3 from the blood, act to suppress feed intake and saliva secretion volumes during the initial stages of feeding in goats fed on dry forage. The animals were fed twice a day at 10:30 and at 16:00 for 2 h each time. Prior to the morning feeding, the collected saliva (3-5 kg) was infused into the rumen. During the morning 2 h feeding period (10:30 to 12:30), the animals were fed 2-3 kg of roughly crushed alfalfa hay cubes. At 16:00, the animals were fed again with 0.8 kg of alfalfa hay cubes, 200 g of commercial ground concentrate and 20 g of sodium bicarbonate. In order to compensate for water or NaHCO 3 lost through saliva during initial stages of feeding, a 3 h intravenous infusion (17-19 ml/min) of artificial mixed saliva (ASI) or mannitol solution (MI) was begun 1 h prior to the morning feeding and continued until the conclusion of the 2 h feeding period.The physiological state of the goats in the present experiment remained unchanged after parotid gland fistulation. Circulating plasma volume decreases caused by feeding (estimated by increases in plasma total protein concentration) were significantly suppressed by the ASI and MI treatments. During the first 1 h of the 2 h feeding period, plasma osmolality in the ASI treatment was the same as the NI (non-infusion control) treatment, while plasma osmolality in the MI treatment was significantly higher. In comparison to the NI treatment, cumulative feed intake levels for the duration of the 2 h feeding period in the ASI and MI treatments increased markedly by 56.6 and 88.3%, respectively. On the other hand, unilateral cumulative parotid saliva secretion volume following the termination of the 2 h feeding period in the ASI treatment was 50.7% higher than that in the NI treatment. MI treatment showed the same level as the NI treatment. The results of the present experiment proved that the humoral factors involved in the suppression of feeding and saliva secretion during the initial stages of feeding in goats fed on dry forage, are feeding induced hypovolemia and decrease in plasma HCO 3 concentration caused by loss of NaHCO 3 from the blood.

“…Silanikove and Tadmor (1989) reported that in cows deprived of water for long periods of time, there was a positive relationship between saliva secretion rates and wheat hay intake. Sunagawa et al (2002b) reported that despite being given free access to water and salt via a pedal press system, sheep with a parotid fistula consumed substantially less alfalfa chaff than sheep without a parotid fistula. It is therefore thought that saliva secretion volume is a regulating factor in dry forage intake.…”

Section: Introductionmentioning

confidence: 99%

An Intravenous Replenishment of Salivary Components and Dry Forage Intake in Freely Drinking Large-type Goats

Sunagawa¹,

Hashimoto²,

Izuno³

et al. 2008

Large-type goats eating dry forage secreted large volumes of saliva which resulted in the loss of NaHCO 3 from the blood and decreased plasma volume (hypovolemia). This research investigated whether or not the loss of NaHCO 3 from the blood and hypovolemia brought about by dry forage feeding actually depresses feed intake in large-type goats under free drinking conditions. The present experiment consisted of three treatments (NI, ASI, MI). All treatments in this experiment were carried out under free drinking conditions. In the NI control (NI), a solution was not infused. In the ASI treatment, i.v. infusion of artificial saliva was initiated 2 h before feeding and was continued for a total of 3 h concluding 1 h after the commencement of the feeding perod. In the MI treatment, mannitol solution was infused to replenish only water lost from the blood in the form of saliva. The hematocrit and plasma total protein concentrations during feeding in the NI control were observed to be higher than pre-feeding levels. This indicated that dry forage feeding-induced hypovolemia was caused by the accelerated secretion of saliva during the initial stages of feeding in freely drinking large-type goats. Increases in hematocrit and plasma total protein concentrations due to dry forage feeding were significantly suppressed by the ASI treatment. While hematocrit during feeding in the MI treatment was significantly lower than the NI control, plasma total protein concentrations were not different. From these results, it is clear that the MI treatment was less effective than the ASI treatment in mitigating the decreases in plasma volume brought about by dry forage feeding. This indicates that plasma volume increased during dry forage feeding in the ASI treatment which inhibited production of angiotensin II in the blood. The ASI treatment lessened the levels of suppression on dry forage feeding, but the MI treatment had no effect on it under free drinking conditions. The results indicate that despite the free drinking conditions, increases in saliva secretion during the initial stages of dry forage feeding in large-type goats caused NaHCO 3 to be lost from the blood into the rumen which in turn caused a decrease in circulating plasma volume and resulted in activation of the renin-angiotensin system and thus feeding was suppressed.