Abstract
The impact of dietary 2-hydroxy-4-(methylthio) butyric acid isopropyl ester (HMBi) on rumen fermentation in cashmere goats was investigated to determine the effect of this ester on cashmere production. Four healthy castrated Liaoning cashmere goats with permanent rumen cannulas were assayed for four periods. In each period, goats were fed a different diet: control diet (containing 0% MetaSmart (an HMBi product)), diet I (containing 0.85% MetaSmart), diet II (containing 1.27% MetaSmart) or diet III (containing 1.70% MetaSmart). Rumen pH, ammonia-N concentration, volatile fatty acid (VFA) concentrations and total protein concentration were determined after feeding in each period. Results showed that rumen pH significantly increased and rumen ammonia-N concentration significantly decreased when the diet was supplemented with 0.85%, 1.27% and 1.70% MetaSmart. Diets with 1.27% and 1.70% MetaSmart increased rumen total VFA concentration, and 3 hours post feeding all three HMBi diets increased acetic acid concentration. Rumen total protein concentration significantly increased in the goats fed 1.27% or 1.70% MetaSmart. Thus, diets supplemented with HMBi significantly affected rumen pH, ammonia-N concentration, VFA concentrations and total protein content. Dietary HMBi can promote rumen fermentation in cashmere goats.
Highlights
Methionine is a limiting amino acid in the diet of goats
Significant correlation was found between rumen pH and dietary hydroxy-4-(methylthio) butyric acid isopropyl ester (HMBi) level (P
Rumen ammonia-N concentration gradually increased after feeding with each diet (Table 3), but the increasing trend was greater with the control diet than with the three other diets
Summary
Methionine is a limiting amino acid in the diet of goats. As a sulfur-containing amino acid, methionine is a key factor to determine the quality of cashmere (Reis, 1979) and there has been much interest in increasing methionine levels in the diet of cashmere goats.2-hydroxy-4-(methylthio) butyric acid isopropyl ester (HMBi) is a rumen-protected methionine additive that can be absorbed by the rumen wall and converted into methionine (Graulet et al, 2004). About 50% of HMBi is degraded to 2-hydroxy-4-(methylthio) butyric acid (HMB) by microbes in the rumen (Robert et al, 2002; Noftsger et al, 2005), so HMBi may affect rumen fermentation via HMB. Patton et al (1970) stated that HMB affected rumen fermentation by altering some microbes in the rumen, while Hegedus et al (1995) and Noftsger et al (2005) found that HMB did not significantly promote the growth of microbes. These varying results cast doubt about the effects of HMB on rumen fermentation and microbe
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