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This study was conducted to investigate the effect of betaine on growth performance, carcass characteristics, myogenic gene expression, and insulin-like growth factor-1 (IGF-1) signaling pathway in partridge shank broiler chickens. A total of 192 one-day-old partridge shank broiler chickens were randomly divided into 4 groups with 6 replicates of 8 chickens for a 52-d feeding trial. Broilers were fed a basal diet supplemented with 0 (control), 250 (B250), 500 (B500), or 1,000 (B1000) mg/kg betaine. Compared with the control group, the B500 and B1000 groups had higher (P < 0.05) body weight gain (BWG), and the B500 group had a lower (P < 0.05) feed/gain ratio (F:G) during the whole trial period. Moreover, the B1000 group increased (P < 0.05) the breast muscle yield and decreased (P < 0.05) relative abdominal fat weight. The mRNA expression of myocyte enhancer factor 2B (MEF2B) and mechanistic target of rapamycin (mTOR) and mTOR phosporylation were higher (P < 0.05) in both breast and thigh muscles in the B500 and B1000 groups than those in the control group. The higher (P < 0.05) concentration and mRNA expression of IGF-1 were also observed in breast muscle in the B500 and B1000 groups. Additionally, the B1000 group up-regulated (P < 0.05) the mRNA level of myogenic differentiation factor 1 (MyoD1) in breast muscle and myogenin (MyoG) in thigh muscle. In conclusion, diets supplemented with 500 or 1,000 mg/kg betaine improved the growth performance of partridge shank broiler chickens during the whole trial period, and the B1000 group significantly improved the breast muscle growth. These improvements might result from increased mRNA expression of MyoD1 and MEF2B in breast muscle and MyoG and MEF2B in thigh muscle, and through alterations in IGF-1/mTOR signaling pathway.

Translucent egg consumption is low due to consumer acceptance and quality concerns, which is a problem that egg producers need to address. This study was performed to evaluate the reasons for the high occurrence of egg translucency in summer, as well as whether the addition of mono-dicalcium phosphate (MDCP) to the diet can relieve eggshell translucency and whether eggshell translucency is associated with the risk of bacterial invasion. A total of 72 laying hens that were 36 weeks old were randomly divided into control (CON) and MDCP groups and fed in the same environment. Results showed that the number of translucent eggs increases in July and August as the temperature and humidity increase. Compared with the CON group, in July, August, and October, the translucent egg grade (TEG) of the MDCP group was lower than that of the CON group (p < 0.05). TEG was correlated with mastoid space height (MSH), width (MSW), and area (MSA) (correlation coefficients 0.63, 0.59, and 0.68, respectively, p ≤ 0.05). There was no significant difference in the invasion rate of E. coli between translucent and non-translucent egg groups (47.2% vs. 39.33%), and translucent area and non-translucent area (13.49% vs. 15.08%). In conclusion, our results show that dietary MDCP may alleviate eggshell translucency and that eggshell translucency would not increase the probability of E. coli cross-shell penetration rate.

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