In vivo mixed muscle and collagen turnover in P. major in two meat broiler strains and their characterization by heat production, microbiota and plasma metabolites for myopathy

Two fast-growing meat-type broiler strains were reared in 70 floor pens (25 birds/pen; 35 pens/strain) from 0-56d utilizing primary breeder nutrition and husbandry guidelines for P. major mixed muscle and collagen protein turnover (PT) study. Broilers (n=10, each strain) were selected at d 21, 28, 35, 42 and 56 and infused with 15N- phenylalanine (Phe) and 1-13C proline (Pro) utilized as amino acid tracers. Muscle and plasma samples were collected and enrichments of 15N-Phe and 1-13C Pro were determined using mass spectrometry. Fractional synthesis rate (FSR) and fractional degradation rate (FDR) were measured. At d 42, broilers were also studied for heat production (HP), microbiota and plasma metabolites after separating the sampled birds as myopathy (woody breast (WB) score > 2) and non-myopathy (WB < 1) (n= 5 each group). Data were analyzed using one-way ANOVA using t-test. Data from microbial 16s rRNA gene sequencing were analyzed using mothur package, whereas plasma metabolome was processed using skyline software. Results showed that mixed muscle and collagen FSR and FDR in P. major dropped (P <0.05) for both the strains as broiler aged. Mixed muscle FSR for Strain A was 33.75 %/D whereas it was 35.03 %/D for Strain B at d 21 and decreased to 8.01 %/D and 11.66 %/D by d 56 respectively. FDR for mixed muscle and FSR for collagen was higher for Strain B than Strain A (P <0.05). Total collagen was higher (P <0.05) for Strain B (4.50 and 12.12 µg/mg for Strain A and Strain B by d 56) with greater myodegeneration occurring as exhibited by histomicrograph. Fasting HP (P <0.05) was higher for non-myopathy bird which was indicative of higher body protein content. Microbiota results showed unclassified Lactobacillus was predominant genus in myopathy group. Differentially expressed significant metabolites (P <0.05) identified between myopathy and non-myopathy group in plasma were homocysteine, cyclic GMP, trimethylamine N-oxide (TMAO), tyramine, carnitine and acetylcarnitine, which were all associated to cardiovascular system. Findings suggest that higher myodegeneration occurring in Strain B (than Strain A) in could be due to higher mixed muscle degradation (likely from compromised vascularity) resulting in higher collagen content and greater myopathy incidence.

Key Words: muscle synthesis, muscle degradation, collagen, metabolite, myopathy.

Abstract presented at the International Poultry Scientific Forum during IPPE 2020.