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

Abstract

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.

Deprivation of Esophageal Boluses and Dry Forage Intake in Large-type Goats

“…Blair-West and Brook (1969) reported that changes in hematocrit and plasma total protein concentration reflected the changes in circulating plasma volume. Sunagawa et al (2008) reported that in large-type goats fed dry forage, hematocrit and plasma total protein concentration rapidly increased with dry forage feeding while plasma osmolality increased very slowly. Consistent with the results reported by Sunagawa et al (2008), in both the NFC control and the SFC treatment of the present experiment, after the commencement of dry forage feeding hematocrit and plasma total protein concentration increased to levels higher than pre-feeding levels.…”

“…Sunagawa et al (2008) reported that in large-type goats fed dry forage, hematocrit and plasma total protein concentration rapidly increased with dry forage feeding while plasma osmolality increased very slowly. Consistent with the results reported by Sunagawa et al (2008), in both the NFC control and the SFC treatment of the present experiment, after the commencement of dry forage feeding hematocrit and plasma total protein concentration increased to levels higher than pre-feeding levels. Hematocrit and plasma total protein concentrations in the SFC treatment were greater than those in the NFC control.…”

The Physiological Suppressing Factors of Dry Forage Intake and the Cause of Water Intake Following Dry Forage Feeding in Goats — A Review

“…Values are means± standard error of 6 large-type goats. a,b Means with different superscripts differ (p<0.05) from the non-infusion control (NI) ( Sunagawa et al, 2008 ).…”

“…In countries such as Japan where ruminants are raised in barns, most farmers feed their livestock a diet of dry forage twice a day. In NFC when goats were fed on dry forage for 2 h twice daily, irrespective of whether drinking water was supplied ( Nagamine et al, 2003 ; Sunagawa et al, 2003 ; 2008 ) or withheld ( Sunagawa et al, 2002 ; 2007 ) during feeding, eating rates rapidly decreased in the first 30 or 40 min of feeding and were subsequently reduced to very low rates for the reminder of the 2 h feeding period. The low eating rates mean that dry forage intake significantly decreased.…”

“…It was investigated whether or not the loss of NaHCO 3 from the blood and hypovolemia brought about by dry forage feeding actually depress dry forage intake in goats under free drinking conditions ( Sunagawa et al, 2008 ). The experiment consisted of three treatments (non-infusion control: NI, intravenous infusion of artificial saliva: ASI, intravenous infusion of mannitol solution: MI).…”