Effects of Decreasing Dietary Crude Protein Level on Growth Performance, Nutrient Digestion, Serum Metabolites, and Nitrogen Utilization in Growing Goat Kids (Capra hircus).

Wen Zhu,Xingyong Chen,Zijun Zhang,Congcong Wei,Wei Xu,Chunchao Jiang

doi:10.3390/ani10010151

Wen Zhu, Xingyong Chen + Show 4 more

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https://doi.org/10.3390/ani10010151

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Abstract

Simple SummaryReducing the dietary protein content could potentially reduce losses of nitrogen from ruminant farms and mitigate pressure on the protein ingredient supply. However, there is little information in the literature on the effect of low-protein diets in growing Anhui white goat kids. We demonstrated that decreasing the dietary crude protein level in Anhui white goat kids affected growth performance, improved nitrogen utilization, and reduced environmental nitrogen pollution. The key finding of this study was that a diet containing 13.4% crude protein supplied adequate protein to improve nitrogen utilization in white goat kids without any adverse effect on growth performance.The effects of decreasing dietary crude protein (CP) level on growth performance, nutrient digestion, serum metabolites, and nitrogen utilization in growing goat kids were investigated in the current study. Thirty-six male Anhui white goat kids were randomly assigned to one of three CP content diets: 14.8% (control), 13.4%, and 12.0% of dry matter, respectively. Diets were isoenergetic. The experiment lasted for 14 weeks, with the first two weeks being for adaptation. Results showed that the low-CP diet decreased average daily gain, feed efficiency, digestibility of dry matter, organic matter, crude protein, and fiber. No significant changes were observed in dry-matter intake. With a decrease in dietary CP level, fecal nitrogen excretion (% of nitrogen intake) increased linearly, whereas CP intake, blood urea nitrogen, urinary nitrogen excretion (% of nitrogen intake), and total nitrogen excretion (% of nitrogen intake) decreased. Serum glucose concentration decreased, while concentrations of low-density lipoproteins and non-esterified fatty acids increased with the low-CP diet. In conclusion, decreasing the dietary CP level decreased goats’ nitrogen excretion, but with restrictive effects on growth performance. A diet containing 13.4% CP is optimal for reducing nitrogen excretion without any adverse effect on growth performance of Anhui white goat kids. This concentration is 1.4% points lower than the NRC recommendations and thus is also environmentally beneficial on the input side because it decreases the use of feed (soy) protein.

Highlights

In ruminants, the part of microbial degradable dietary nitrogen (N) is converted to ammonia in the rumen [1]
The crude protein (CP) level of the diet had no significant effect on dry-matter intake (DMI) (p > 0.05) (Table 2)
Intake of neutral detergent fiber (NDF) and acid detergent fiber (ADF) was not affected by CP level (p > 0.05)

Summary

Introduction

The part of microbial degradable dietary nitrogen (N) is converted to ammonia in the rumen [1]. The excessive ammonia absorbed through the rumen wall into the blood converts to urea in the liver, which is excreted in the urine [2]. Nitrogen excretion results in water pollution, soil acidification, and formation of fine particles [3]. As an important source of food, fiber, and economic security [4], goats are an important ruminant species, especially in developing countries. As the global population of goats is approximately 654 million the goat industry should take responsibility for N excretions [5]. According to previous studies, reducing dietary protein level is an effective way to reduce N excretion [6,7]

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