Feed utilisation, physiological and meat quality responses in Jumbo quail reared on apple pomace-containing diets

Abstract

Quail (Coturnix sp.) farming has enormous potential to contribute to global food production and nutritional security by supplying high-quality animal protein to meet the nutritional demands of the rapidly growing human population. However, over-dependence on conventional feed ingredients such as maize (Zea mays L.) and soybean (Glycine max) when formulating quail diets is socially, economically, and environmentally unsustainable. Alternatively, the use of agro- industrial by-products such as apple (Malus domestica Borkh.) pomace, which are usually discarded to the detriment of the environment, could offer a sustainable long-term strategy to continuously supply bioactive compounds and essential nutrients for sustainable quail intensification while protecting the environment. Thus, this study assessed the effect of including graded levels of apple pomace powder (APP) on apparent nutrient digestibility, growth performance, blood parameters, carcass characteristics, internal organ sizes, and meat quality and composition in Jumbo quail. A total of 350, one-week-old unsexed Jumbo quail chicks (28.0 ± 0.828 g live weight), were evenly and randomly allotted to 35 replicate pens (experimental units). The birds were reared using five isonitrogenous and isoenergetic experimental diets (replicated seven times), which were formulated by including APP in a standard grower diet at a rate of 0 (AP0), 25 (AP25), 50 (AP50), 75 (AP75), and 100 g/kg (AP100). Daily feed intake and weekly liveweights were measured from week 1 to week 5. At five weeks of age, two female quail per pen were selected and used to measure apparent nutrient digestibility, while the rest of the birds were slaughtered at a nearby abattoir. Blood was collected during slaughter from two birds per experimental unit for measurement of serum biochemical and haematological parameters. Thereafter, the carcasses were eviscerated for measurement of carcass characteristics, internal organs, and meat quality parameters. Experimental diets significantly influenced organic matter digestibility (OMD) only, where quail on diet AP100 had higher (P <0.05) OMD (651.4 g/kg) than those on diet AP75 (542.1 g/kg). Linear and quadratic effects (P <0.05) were observed for feed intake in week 2 in response to increasing dietary APP levels. In week 3, feeding incremental levels of dietary APP induced a significant quadratic effect for feed intake. Diet AP75 promoted the highest feed intake in weeks 2, 3, 4 and 5. Two-week-old Jumbo quail offered diet AP25 had higher (P <0.05) weight gain (30.41 g/bird) than those in the other treatment groups. However, in week 5, birds reared on diet AP75 (46.84 g/bird) had higher weight gain than all the other treatment groups. Significant linear decreases were observed for G:F in weeks 2, 3 and 4 in response to dietary APP levels. In week 5, G:F showed a significant quadratic response [y = 0.240 (±0.0167) + 0.002 (±0.0009) x – 0.00002 (±0.000008) x2; R2 = 0.151; P = 0.024], from which an optimum inclusion level was calculated to be 50.0 g/kg APP. Diet AP25 promoted higher (P <0.05) serum calcium levels than diets AP75 and AP100. Quail reared on diet AP0 had the least alkaline phosphatase (ALKP) (166.1 U/L) content than those on diets AP75 and AP100. Diet AP0 produced heavier carcass weights than diet AP100. Diet AP0 promoted the heaviest proventriculus weight (0.778 % HCW) compared to all the other diets. One-hour yellowness (b*1) and 24-h (L*24) showed linear increases, while 24-h redness (a*24) and 24-h (chroma24) linearly declined with increasing APP levels. Diet AP25 promoted higher pH24 values (5.59) than diets AP0, AP50, AP75 and AP100, which did not differ (P >0.05). Quail meat from birds fed diet AP75 had higher (P <0.05) crude protein (CP) (225.9 g/kg) than meat from quail fed with diets AP0, AP50 and AP100, whose CP content did not differ (P >0.05). Based on the quadratic response for G:F in week 5, an optimum APP inclusion of 50.0 g/kg was determined. It was concluded that dietary APP should be capped at 50 g/kg to maximize feed utilisation efficiency in Jumbo quail without compromising blood, carcass, and meat quality parameters.