Muscle fibers proportion play a major role in meat quality and can be regulated by diets. Inadequate protein supplies cause changes in the concentrations of free AA in the muscle, which have been evaluated as potential biochemical markers of pork quality. However, not enough research has been reported regarding the effect of protein level in the muscle. The objective of the present study was to assess the effect of feeding reduced crude protein (CP), AA-supplemented diets on meat quality in growing and finishing pigs. For this purpose, two trials were carried out. In the first trial, 18 crossbred growing pigs (36.5 kg BW) were randomly assigned and fed 1 of 3 corn-soybean meal diets containing either 18% CP (normal protein, NP); 15% CP (low protein, LP); or 12% CP (very low protein, VLP). In the second trial, another 18 finishing pigs (62.3 kg BW) were allotted randomly into three diets: 16% CP (NP); 13% CP (LP); and 10% CP (VLP). LP and VLP diets were supplemented with crystalline AA in both trials to achieve equal content of standardized ileal digestible lysine, methionine, threonine, and tryptophan. At the end of each study, longissimus dorsi muscle (LM) samples were collected from all pigs. Samples were used for determining meat quality, intramuscular fat (IMF) content, fatty acid composition, free AA profile, and myosin heavy chain isoforms gene expression.
Growing and finishing pigs fed the LP diets showed an increased redness value of LM, while finishing pigs fed the LP and VLP diets revealed a decreased shear force values. Compared with the NP diet, growing and finishing pigs fed lower CP diets had higher contents of IMF and MUFA, and therefore lower contents of PUFA. Besides, higher concentrations of taurine and free AA (which are suggested to produce a tastier flavor in meat) were observed in VLP diet-fed growing and finishing pigs.
Results appear to indicate that low-protein diets (3% reduction of dietary CP) could positively affect meat quality of growing and finishing pigs, probably through regulation of IMF content and fatty acid composition, fiber characteristics, and free AA profile in the muscle.
Li, Y. H., F. N. Li, Y. H. Duan, Q. P. Guo, C. Y. Wen, W. L. Wang, X. G. Huang, and Y. L. Yin. 2018. Low-protein diet improves meat quality of growing and finishing pigs through changing lipid metabolism, fiber characteristics, and free amino acid profile of the muscle. Journal of animal science 96: 3221-3232. https://doi.org/10.1093/jas/sky116