Growth performance, carcass and blood traits, immunity, jejunal morphology and meat quality of heat-stressed broiler chickens fed urea-treated pomegranate (Punica granatum L.) peel

Abstract

The aim of this study was to evaluate the effects of dietary urea-treated pomegranate (Punica granatum L.) peel (UTPP) on growth performance, carcass attributes, blood biochemical indices, immunity, intestinal morphology, and meat quality of broiler chickens subjected to heat stress. The treatment with urea increased the gross energy and crude protein contents, while decreased the ash, calcium, phosphorous, neutral detergent fiber, acid detergent fiber, extractable polyphenols, total anthocyanins, condensed tannins, and hydrolyzable polyphenols contents of pomegranate peel. A total of 200 1-day-old male broiler chickens were randomly allocated to four groups; each group had 5 floor pens with 10 birds each. The broiler chickens were fed with the basal diet containing 0, 15, 30 or 50 g UTPP / kg diet from day 1, and exposed to a cyclic high temperature (37 ± 1 °C, 55 % relative humidity) for 6 h / day from day 29 –42. Dietary UTPP increased body weight gain during the starter (linear (L), P = 0.001; quadratic (Q), P < 0.001) and overall experimental (L, P = 0.019; Q, P = 0.004) periods. However, it reduced feed intake during the starter (Q, P = 0.004) and grower (L, P = 0.019; Q, P = 0.007) periods. Dietary UTPP improved the feed conversion ratio during the starter (L, P < 0.001; Q, P < 0.001), grower (L, P = 0.018), finisher (L, P = 0.004), and overall experimental (L, P = 0.001) periods. The breast yield quadratically increased as UTPP level increased (P = 0.002), while the liver (L, P = 0.002) and abdominal fat (L, P < 0.001) percentages decreased. The concentration of blood glucose (P < 0.001), high density lipoprotein (P = 0.01), and globulin (P = 0.001) linearly increased with UTPP inclusion, but the plasma albumin (L, P < 0.001), alkaline phosphatase (L, P < 0.001), alanine aminotransferase (L, P < 0.001; Q, P < 0.001), lactate dehydrogenase (L, P < 0.001), cholesterol (L, P < 0.001; Q, P < 0.001), low-density lipoprotein (L, P < 0.001; Q, P < 0.001), and malondialdehyde (L, P < 0.001) concentrations decreased at day 42. The bursa percentage increased (L, P = 0.011; Q, P = 0.006) as UTPP level increased. Dietary UTPP also improved the primary total (L, P < 0.001), IgM (L, P < 0.001; Q, P = 0.003), and IgG (Q, P = 0.015) responses and the secondary total (L, P < 0.001; Q, P = 0.024) and IgG (L, P < 0.001) responses against sheep red blood cells. It increased the villus height (L, P < 0.001; Q, P = 0.003), crypt depth (L, P < 0.001; Q, P < 0.001), and villus height / crypt depth ratio (L, P < 0.001; Q, P = 0.001), while decreased the villus width (L, P < 0.001; Q, P = 0.038).