Effect of reducing dietary protein and lysine on growth performance, carcass characteristics, intramuscular fat, and fatty acid profile of finishing barrows1

Abstract

Intramuscular fat is an important quality trait in pork. Lysine and protein have been reported to influence this trait, but most studies have modified both factors simultaneously. In this study, the effects of dietary Lys and protein were investigated in finishing pigs to determine if either of the 2 factors alone or in combination influence the deposition of intramuscular fat. One hundred and four barrows (Landrace × Duroc) were fed 1 of 4 experimental diets, including control protein-control Lys (CPCL), control protein-low Lys (CPLL), low protein-control Lys (LPCL), and low protein-low Lys diets (LPLL) with 10 pens per treatment and 2 or 3 pigs per pen. Pigs fed CPLL showed a trend to decrease feed efficiency (P < 0.10) compared with those fed CPCL, but pigs fed LPLL performed similarly to the CPCL pigs, indicating that CP levels can be reduced to 12% for pigs between 62 and 97 kg and to 9.8% afterward without negative effects on performance. In the longissimus thoracis, intramuscular fat increased in pigs fed LPCL or CPLL (P < 0.05) compared with CPCL. In the semimembranosus muscle, intramuscular fat was reduced in pigs fed LPLL compared with those fed CPLL (P < 0.05), and the same trend was observed in the longissimus thoracis (P < 0.10). Dietary protein reduction tended to increase back fat thickness (P < 0.10) and reduced SFA and MUFA (P < 0.05) and PUFA, particularly in subcutaneous fat (P < 0.05), whereas the effect on MUFA in the longissimus thoracis was less pronounced. A reduction of n-3 FA (P < 0.05) and PUFA (P < 0.01) in the semimembranosus muscle and in the liver, respectively, was observed when the level of dietary protein was reduced. These results indicate that the effect of a reduction of dietary protein and Lys on growth and intramuscular fat is not independent, and reduction of protein, while maintaining Lys, may improve meat quality without impairing performance.

Effects of sex and dietary lysine on performances and serum and meat traits in finisher pigs

“…That effect might also be modulated by AAs imbalance and the energy source (Tous et al, 2014). In a recent work, a total Lys restriction from 11 to 5.2 g/kg during the grower phase produced an incomplete compensatory growth in the subsequent phase and increased carcass fat depth (Suárez-Belloch et al, 2015) in agreement with previous results from other researchers (Campbell et al, 1988;Fabian et al, 2002).…”

Addition of arginine and leucine to low or normal protein diets: performance, carcass characteristics and intramuscular fat of finishing pigs

“…The current study was performed to evaluate if the reduction of dietary protein level below requirements (NRC, 1998) has the same effect on IMF than in the previous study (Tous et al, 2014) with a different crossbreed (Duroc × Landrace vs. Duroc × Landrace sows crossed with a Pietrain boar) in which IMF was expected to be lower. Therefore, the control diet had a protein level according to NRCʼs (1998) requirements (16% during the growing period and 13% during the fattening period) and the low protein diet had a level below these requirements (14% during the growing period and 11.8% during the fattening period).…”

“…Therefore, the control diet had a protein level according to NRCʼs (1998) requirements (16% during the growing period and 13% during the fattening period) and the low protein diet had a level below these requirements (14% during the growing period and 11.8% during the fattening period). In order to avoid the protein × Lys interaction observed in a previous study (Tous et al, 2014) the level of Lys was kept constant between the different diets. In the current study, although diets were based on maize which has lower protein content than barley, the level of dietary protein could not be as low as in the previous study because diets were supplemented with two different amino acids (Arg and Leu).…”

“…In terms of taste, IMF is well correlated with pork acceptability. The threshold level of 2 of protein as the ones in the control diet resulted in an increase of IMF, while when both parameters protein and Lys were reduced IMF was not affected (Tous et al, 2014). Wood et al (2004) found that a low protein diet slowed growth and increased neutral lipid fatty acid concentrations in Longissimus (LM) and Psoas muscles in the two modern breeds compared with two traditional genotypes.…”

“…The second objective was to determine if the reduction of dietary crude protein (CP) would increase IMF without negatively affecting growth performance and other carcass traits in a leaner genotype ([Landrace × Duroc] × Pietrain) than the one used in our previous study (Duroc × Landrace crossbreed; Tous et al, 2014).…”