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Effects of Dietary Crude Protein Level on Growth Performance, Carcass Traits, Meat Quality, and Fatty Acid Composition of Ningxiang Finishing Pigs
by
, , and
Xianglin Zeng
,
Yan Tang
,
Wenzhi Liu
,
Zhaobin Wang
,
Pengfei Huang
,
Qiye Wang
*
and
Huansheng Yang
* Hunan International Joint Laboratory of Animal Intestinal Ecology and Health, Laboratory of Animal Nutrition and Human Health, College of Life Sciences, Hunan Normal University, Changsha 410081, China
*
Authors to whom correspondence should be addressed.
Animals 2025, 15(20), 2950; https://doi.org/10.3390/ani15202950 (registering DOI)
Submission received: 1 August 2025
/
Revised: 18 September 2025
/
Accepted: 8 October 2025
/
Published: 11 October 2025
(This article belongs to the Section Pigs)
Simple Summary
This study examined the effects of varying crude protein (CP) levels on growth performance, carcass traits, meat quality, and fatty acid composition in Ningxiang finishing pigs. The results revealed that low-protein (LP) diets reduced lean meat percentage and increased fat deposition, while simultaneously improving meat quality and fatty acid profiles. Furthermore, LP diets facilitated fat accumulation by suppressing hepatic tryptophan–niacin metabolism and inhibiting the AMPK signaling pathway in muscle, thereby influencing carcass traits and meat quality. These findings offer valuable insights into optimizing dietary protein strategies to enhance growth performance and meat quality in indigenous pig breeds.
Abstract
This study investigated the effects of different crude protein (CP) levels on growth performance, carcass traits, meat quality, and fatty acid composition in Ningxiang finishing pigs. A total of 200 pigs (52.52 ± 0.41 kg) were assigned to five dietary treatments: high-protein (HP, 15.56%), moderate-high-protein (MHP, 13.99%), moderate-protein (MP, 12.94%), moderate-low-protein (MLP, 11.90%), and low-protein (LP, 10.31%). Feeding the MLP diet significantly improved average daily gain (ADG) compared to HP and LP diets (p < 0.05). Pigs fed the MP diet had higher lean meat percentage than those on the LP diet (p < 0.05), while both HP and MP diets reduced carcass fat percentage (p < 0.05). The LP diet significantly increased a*, pH45min, intramuscular fat (IMF), and C18:1n9c, while decreasing C23:0 and C20:3n6 in the longissimus dorsi muscle (p < 0.05). Liver metabolomics revealed that the LP diet inhibited nicotinate and nicotinamide metabolism (p < 0.05), accompanied by downregulation of genes related to the tryptophan–niacin metabolism and upregulation of genes involved with hepatic lipogenesis (p < 0.05). In muscle, the LP diet inhibited AMPK signaling via decreased p-AMPK expression, leading to increased IMF content (p < 0.05). In summary, the optimal growth performance of Ningxiang finishing pigs was achieved with a CP level of 11.90%. Additionally, the LP diet enhanced meat quality by modulating hepatic niacin metabolism and AMPK signaling.
