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

K Sunagawa,T Hirata,N Hashizume,M Okano,T Hashimoto,M Izuno,I Nagamine

doi:10.5713/ajas.2008.70292

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.

Highlights

The advantages of drying fresh grass are the ability to store it for long periods of time and transport it to far off markets
In the non-infusion control (NI) control of the present experiment, a decrease in plasma volume estimated by increases in hematocrit and plasma total protein concentrations was apparent within 15 min of the commencement of feeding (Figure 3)
The hematocrit and plasma total protein concentrations throughout the entire 2 h feeding period in the NI control were observed to be higher than pre-feeding levels

Summary

Introduction

The advantages of drying fresh grass are the ability to store it for long periods of time and transport it to far off markets. The daily dry matter intake levels in highly productive lactating cows and heifers can be increased by feeding them dry feed rather than fresh grass (Anil et al, 1993). The reason for this is that fresh grass has a water content of more than 80% compared with less than 10% in dry feed. The drying process is expensive and leads to the loss of trace nutrients including vitamins In countries such as Japan where ruminants are raised in barns, most farmers feed their stock a diet of dry roughage twice a day.

Methods

Results

Conclusion