Abstract
Simple SummaryIn the past, many studies have been carried out to investigate the effect of lysine supplementation on broilers’ growth performances and feed efficiency. However, the knowledge concerning the reduction of the dietary content of this essential amino acid is limited and mainly restricted to the production performances of the birds. Within this context, the present study aimed at assessing the impact of lysine restriction during grower I (10–20 d) and grower I and II (10–20 and 21–34 d) feeding phases on live performances, breast meat quality traits and technological properties, as well as on the incidence and severity of abnormalities affecting the pectoral muscles (i.e., white striping, wooden breast and spaghetti meat). Lysine restriction during different feeding phases exerts negligible effects on the production performances of the broilers due to their compensatory growth. In addition, the increased anserine content following lysine depletion might have exerted a protective role against protein denaturation by buffering the acidic end-products generated during post-mortem rigor development.The present study aimed at assessing the impact of lysine restriction performed during different feeding phases on growth performances, meat quality traits and technological properties as well as on the incidence and severity of breast muscle abnormalities. For this purpose, a total of 945 one-day-old Ross 308 male chicks was randomly divided into three experimental groups: CONT, fed a four feeding phases commercial diet, GRW I, and GRW I + II fed CONT diet with the depletion of synthetic lysine during grower I and grower I and II feeding phases, respectively. Productive performances were recorded throughout the whole rearing cycle and the incidence of breast muscle growth-related abnormalities assessed at slaughter (49 d) on 280 breasts/group. Quality traits and technological properties of breast meat were measured on a total of 54 Pectoralis major muscles. Lysine restriction only marginally affected the productive performances and the quality parameters of breast meat. The increased (p < 0.05) solubility of the protein fraction along with the remarkably higher (p < 0.05) anserine content found in GRW I + II suggests an increased energy requirement in the pectoral muscles belonging to lysine-restricted birds and supports the hypothesis of a reduced protein synthesis taking place within these muscles.
Highlights
Lysine (Lys) is one of the most limiting essential amino acids in commercial cornsoybean meal diets for broiler chickens [1]
Chicks assigned to CONT, GRW I and GRW I + II groups showed similar body weight (BW)
Considering the orthogonal contrasts, such differences achieved the statistical significant threshold, thereby confirming that Lys-depleted groups were characterized by lower BW and daily weight gain (DWG)
Summary
Lysine (Lys) is one of the most limiting essential amino acids in commercial cornsoybean meal diets for broiler chickens [1]. The impressive growth rate and breast muscle development achieved by the modern hybrids selected for high meat yield undoubtedly imply the need for an adequate energy and nutrients supply exceeding those ones required for the past genotypes or autochthonous breeds. For this reason, the commercial broiler diets are currently formulated including a Lys level which is higher than that suggested by the NRC [6]. According to the widely known ideal protein concept, the dietary
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