HVT-delivered chicken IGF-1 improves growth performance in broilers

The domesticated poultry is invaluable as a global protein source. Growth performance in poultry, particularly broilers, plays a critical role in production efficiency. Insulin-like growth factor-1 (IGF-1) is a multifunctional hormone which shows promotive effects on growth and development. Traditional IGF-1 delivery methods, such as injections or dietary supplements, face practical limitations including high cost, multiple dosages and rapid degradation. To explore a more efficient IGF-1 delivery method for promoting chicken growth, we generated a recombinant herpesvirus of turkey expressing chicken IGF-1, rHVT-chIGF-1. A single dose of rHVT-chIGF-1 was administered intramuscularly to broilers at day 1 of age. Growth performance parameters, including body weight (BW) and average daily weight gain (ADG) was assessed over a 42-day period. The results showed that, at both 35 and 42 days of age, the rHVT-IGF-1 group showed significantly higher BW and ADG compared to the HVT group (35d BW: p = 0.0063; 42d BW: p < 0.0001; 35d ADG: p < 0.0001; 42d ADG: p < 0.0001) and the blank control group (35d BW: p = 0.0189; 42d BW: p = 0.0032; 35d ADG: p < 0.0001; 42d ADG: p < 0.0001). The cross-sectional area (CSA) of pectoral and leg muscle fibres was significantly greater in chickens from the rHVT-chIGF-1 group compared to those in the HVT vector (p = 0.0078) and blank control (p = 0.025) groups. Additionally, the mRNA expression of muscle development-related genes was significantly upregulated in the rHVT-chIGF-1 group. These findings suggest that rHVT-chIGF-1 is a novel and effective in vivo delivery system for promoting chicken growth, offering an alternative to traditional IGF-1 delivery methods.