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

K Sunagawa,S Shiroma,T Ooshiro,I Nagamine,N Nakamura,A Shinjo

doi:10.5713/ajas.2005.1414

Abstract

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 NaMCO 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.

Highlights

Ruminants can consume large amounts of feed quicker than their non-ruminant counter-parts (Tsuda, 1994)
In the non-infusion control (NI) treatment 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)
In comparison to the NI treatment, the level of increase in plasma total protein concentration brought about by feeding, was decreased by both the artificial mixed saliva intravenous infusion treatment (ASI) and MI treatments (Figure 3). These results indicate that the level of decrease in plasma volume estimated by increases in plasma total protein concentrations declined significantly during the initial stages of crushed alfalfa hay cube feeding

Summary

Introduction

Ruminants can consume large amounts of feed quicker than their non-ruminant counter-parts (Tsuda, 1994). These actions are supported by their salivary secretion pattern. The water supplies fluid to the non-secretory rumino-reticulum and helps facilitate mixing of the ruminal content. The sodium bicarbonate in the saliva being an alkaline, serves to buffer the decrease in the pH due to volatile fatty acid production in the rumen. In this way, saliva plays an important role in eating and homeostatic regulation of the acid-base balance in rumen fluid

Objectives

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Conclusion