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Open AccessArticle

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

1
College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, China
2
Luan Lvjie Animal Husbandry Co., Ltd., Luan 237000, China
*
Author to whom correspondence should be addressed.
Animals 2020, 10(1), 151; https://doi.org/10.3390/ani10010151 (registering DOI)
Received: 26 November 2019 / Revised: 8 January 2020 / Accepted: 8 January 2020 / Published: 16 January 2020
(This article belongs to the Special Issue Small Ruminant Nutrition and Metabolism)
Reducing 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.
Keywords: crude protein; growth performance; nutrient digestion; nitrogen utilization; Anhui white goat crude protein; growth performance; nutrient digestion; nitrogen utilization; Anhui white goat
MDPI and ACS Style

Zhu, W.; Xu, W.; Wei, C.; Zhang, Z.; Jiang, C.; Chen, X. Effects of Decreasing Dietary Crude Protein Level on Growth Performance, Nutrient Digestion, Serum Metabolites, and Nitrogen Utilization in Growing Goat Kids (Capra hircus). Animals 2020, 10, 151.

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