Abstract

The supplementation of livestock feed with animal protein is a present cause for public concern, and plant protein shortages have become increasingly prominent in China. This conflict may be resolved by fully utilizing currently available sources of plant protein. We estimated the rumen degradability and the small intestinal digestibility of the amino acids (AA) in rapeseed meal (RSM), soybean meal (SBM), sunflower seed meal (SFM) and sesame meal (SSM) using the mobile nylon bag method to determine the absorbable AA content of these protein supplements as a guide towards dietary formulations for the dairy industry. Overall, this study aimed to utilize protein supplements effectively to guide dietary formulations to increase milk yield and save plant protein resources. To this end, we studied four cows with a permanent rumen fistula and duodenal T-shape fistula in a 4×4 Latin square experimental design. The results showed that the total small intestine absorbable amino acids and small intestine absorbable essential amino acids were higher in the SBM (26.34% and 13.11% dry matter [DM], respectively) than in the SFM (13.97% and 6.89% DM, respectively). The small intestine absorbable Lys contents of the SFM, SSM, RSM and SBM were 0.86%, 0.88%, 1.43%, and 2.12% (DM basis), respectively, and the absorbable Met contents of these meals were 0.28%, 1.03%, 0.52%, and 0.47% (DM basis), respectively. Among the examined food sources, the milk protein score of the SBM (0.181) was highest followed by those of the RSM (0.136), SSM (0.108) and SFM (0.106). The absorbable amino acid contents of the protein supplements accurately reflected protein availability, which is an important indicator of the balance of feed formulation. Therefore, a database detailing the absorbable AA should be established.

Highlights

  • A proper balance of the amino acids (AA) in the diet of dairy cattle is desirable because it may increase the level of milk protein (Paz et al, 2014)

  • The dry matter (DM), ether extract (EE), crude protein (CP) contents, Composition of feed crude fiber analyzed according to the AOAC (1990)

  • The neutral detergent fiber (NDF) and acid content of CP was highest in the soybean meal (SBM) (49.73%) and lowest detergent fiber (ADF) were analyzed according to the in the SFM (30.87%)

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Summary

Introduction

A proper balance of the amino acids (AA) in the diet of dairy cattle is desirable because it may increase the level of milk protein (Paz et al, 2014). Many researchers report that increases in dietary protein levels do not necessarily improve the milk production of dairy cows (Chiou et al, 1995), which may be due to imbalances in the AA profile of Submitted Apr. 21, 2015; Revised Aug. 3, 2015; Accepted Aug. 27, 2015 the rumen undegraded protein (RUP) or dietary protein degradation in the rumen that exceeds the capability of microbial proteins synthesized by rumen microorganisms (Chiou et al, 1995; Van Straalen et al, 1997; AbuGhazealeh et al, 2001). For the diet of dairy cows, profile AA and digestibility of RUP are estimated in a similar value as the initial protein supplements via the dairy NRC (2001) model. The rumen degradability (RD) of the feed AA and small intestinal digestibility (SID) of rumen undegraded AA of the feed

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