Effects of lysine concentration of the diet on growth performance and meat quality in finishing pigs with high slaughter weights

Abstract

The present study aimed to investigate the feasibility of using a diet low in lysine content as a means for increasing the intramuscular fat (IMF) content and pork muscle quality of finishing pigs. Thirty-two crossbred gilts and barrows weighing approximately 80 kg were fed either a low-lysine diet (0.60%; Low-lys) or a control diet (0.80% lysine; Med-lys) under a 2 × 2 factorial arrangement of treatments. The animals were slaughtered at a 132-kg body weight (BW) on average, followed by physicochemical analyses and sensory evaluation on Longissimus lumborum (LL) and Semitendinosus (ST) muscles. The average daily gain (ADG) did not differ between the Med-lys and Low-lys groups. However, ADG exhibited a tendency of sex × diet interaction (p = 0.09), being greater for barrows vs. gilts on the Low-lys diet ( p < 0.05), but not on the Med-lys diet. Backfat thickness adjusted for 132-kg BW also exhibited the interaction; it was greater for the Low-lys vs. Med-lys group within gilts but tended to be less for the former in barrows ( p = 0.08). The IMF content was not influenced by the diet or sex in either LL or ST. The a*, b*, and Warner-Bratzler Shear Force values and fatty acid composition were influenced by the sex or diet in either or both of the muscles, but the treatment effects did not apparently influence the meat quality. Sensory scores for the flavor, juiciness, tenderness, umami, and palatability of cooked muscle were not influenced by the diet in either LL or ST. When the LL and ST data were pooled, scores for those sensory attributes were positively correlated with the IMF content, which was associated with overall greater IMF contents and greater sensory scores for ST vs. LL. Collectively, the Low-lysine diet seemingly elicited the intended lysine deficiency in gilts as indicated by the increased BFT due to the diet. However, the Low-lys diet was not effective for increasing the IMF deposition or eating quality of the pork muscle of finishing pigs slaughtered at high BW probably because its lysine content was not low enough to elicit either outcome.

Effects of an extra-high slaughter weight and a low-lysine diet on growth and meat quality of finishing gilts

“…Use of a diet having a low lysine content is known to elicit an increase in IMF deposition accompanied by an increased backfat thickness (BFT) [18][19][20]. In a companion study of ours preceding the present one [21], gilts fed a low-lysine (0.60%) vs. control (0.80% lysine) diet from 81-kg BW to slaughter at 132 kg exhibited the known consequence of the lysine deficiency indicated by an increased BFT whereas in barrows such a diet effect was not detected. The gilts fed the low-lysine diet, however, did not have a greater IMF content or better eating quality of LM than those fed the control diet.…”

“…The animals used in the present study were Duroc-sired, Landrace × Yorkshire progeny which had the same genetic lineage as those used in the companion study [21], whose feeding trial mostly overlapped temporally with that of the present study. The animals had been reared on commercial grower diets with medium nutritional planes followed by a medium-nutritional plane finisher diet containing 0.80% lysine by the NRC [23] standard approximately from 80-kg BW before the present feeding trial as previously described [20,21,24].…”

“…Sixteen finishing gilts aged 140 ± 1 days and weighing approximately 85 kg were randomly allotted to two pens, with eight animals per pen, and fed to 150-kg target SW either of the medium-lys (XHSW group) and low-lys (0.60%; XHSW-LowLys group) diets which had been used as experimental diets in the companion study [21]. Eight gilts, as well as eight barrows as for the control with respect to the gender, weighing approximately 116 kg [AvSW and (B)AvSW groups, respectively] were selected at trucking from the market pigs which had been raised as for the pigs of the XHSW group but with no weight gain record.…”

“…The Longissimus lumborum muscle (LL) was dissected from the loin followed by removal of the subcutaneous fat. Physicochemical properties of trimmed LL, including the color, pH, Warner-Bratzler Shear force, and others pertaining to the water holding capacity were measured as previously described [14,21,25]. The fat content and fatty acid (FA) composition of LL were determined by Soxhlet extraction following the procedure of AOAC [26] and by gas chromatography after extraction of total lipids [27],…”

Effects of increasing dietary lysine and energy levels on growth efficiency, nutrient absorption, and meat carcass traits in growing-finishing pigs

“…The mechanism for the potential additional benefit of feeding above generally accepted net energy and lysine requirements in improving pig growth performance may involve enhanced nutrient utilization and metabolic efficiency, possibly through the stimulation of protein synthesis [15]. However, employing a low-lysine diet was not effective in enhancing the intramuscular fat content or improving the eating quality of pork muscle in finishing pigs with high slaughter weights [16]. Similarly, the utilization of a low-energy diet and the subdivision of the growing-finishing phase based on dietary protein levels did not yield any significant effects on growth performance or carcass characteristics [17].…”