There was significant effect (P<0.05) of supplementation on average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR) during d 7-21, 22-42 and 0-42 (Table 2). During d 7-21, T2, T3 and T5 groups showed higher ADG (P<0.05) when compared to other groups. T3 group showed highest ADG from d 22-42 of experimental period. T3 group had significantly higher final BW than other supplemented groups and control. Similar observations were found by Zanu et al., (2011), Ansari et al., (2012)
and Shihab et al., (2017)
who reported that NLP supplementation improved final BW of broiler chickens. Contrary to the present findings, Bonsu et al., (2012)
and Nayaka et al., (2013)
reported that BW was not affected by NLP supplementation in broilers. Results of present study are in agreement with that of Saied et al., (2022)
who reported that CNO (500, 1000, 1500 mg/kg) supplementation significantly increased chickens’ BW in comparison with control and antibiotic groups; however 500 mg/kg CNO level gave more salient results. Ahmed et al., (2019)
found that BW of quail chicks significantly increased when supplemented with ginger or CNO than antibiotic. Mehdipour and Afsharmanesh (2018)
also observed that adding 200 mg/kg CNO in quail feed improved BW and FCR when compared with control birds.
Table 2: Average daily gain (ADG; g/d), body weight (BW), average daily feed intake (ADFI; g/d), feed conversion ratio (FCR) and broiler performance efficiency index (BPEI) of broiler chickens (d 0-42).
It was observed that ADFI differed significantly (P<0.001) during d 7-21 and d 22-42. During d 7-21, ADFI was highest in T0, followed by T5 and lowest in T2 group. When birds were on finisher diet, ADFI was least in T5 group. Overall feed intake (d 0-42) significantly (P<0.05) decreased in response to supplementation than control. This might be due to bitter taste (limonoid) of NLP and strong, warm and spicy aroma associated with CNO, thus decreasing feed palatability (Paul et al., 2020).
Findings of present study are in agreement with that of Akintomide and Onibi (2018)
, Beg et al., (2018)
and Ubua et al., (2019),
but contradicted to Zanu et al., (2011), Adeyemo and Akanmu (2012)
and Bonsu et al., (2012)
who reported no significant difference in feed intake between control and neem leaf fed groups and Mehdipour et al., (2013)
who reported feed intake was not affected by CNO treatments.
During d 7-21 and 22-42, all the supplemented groups (T1 to T5) showed better FCR (P<0.001) than control group. Overall FCR (d 0-42) ranged from 1.69 to 1.81 in supplemented groups, which was significantly (P<0.001) better than control (1.98). Within supplemented groups, T3 and T5 groups performed better than other groups. This effect was more pronounced for birds fed with 100 mg/kg CNO in comparison with 200 mg/kg CNO and neem supplemented groups. This finding is in accordance with Devi et al., (2018)
and Mehdipour and Afsharmanesh (2018)
who reported that feeding 3 g/kg CNO + 4 g/kg ajwain and 200 mg/kg CNO respectively, improved FCR significantly when compared with control.
Both T3 and T5 groups showed better (P<0.001) BPEI when compared with control and other supplemented groups. This finding is in accordance with Devi et al., (2018)
who found that European Production Efficiency Index significantly enhanced during upon supplementation of 3 g/kg CNO and 4 g/kg ajwain.
The observed enhancement in growth traits upon addition of CNO (100 mg/kg) in broiler diets may be imputed due to effect of some active constituents (cinnamaldehyde and eugenol) in cinnamon plant, which are regarded as stimulatory agents for digestion because of their accelerating ability to secrete endogenous digestive enzymes, safeguard intestinal villi via intercellular antioxidant action and favourably impact how well digested nutrients are absorbed (Jamroz et al., 2006).
According to Toghyani et al., (2011),
broiler chickens fed 2 g/kg cinnamon powder at d 28 and 42 had a higher BW than control. Ciftci et al., (2009)
stated that higher BW and FCR were observed at d 35 by supplementing 500 mg/kg CNO in broiler diet than control and antibiotic-treated groups. Contrarily, Symeon et al., (2014)
didn’t find any significant effect of CNO supplementation on broiler chickens’ growth performance.
Better performance was observed when CNO (100 mg/kg) and same dose of CNO with combination of NLP (2 g/kg) were fed to broiler chickens. This may be due to synergistic effect of CNO and NLP. Synergistic feed additives operate by combining their individual effects to produce outcomes that are superior to those of their single use (Ren et al., 2019).
Potency of lesser doses of herbal products like neem oil as compared to individual components can be attributed to synergistic interactions between multiple ingredients prevalent within plant extracts, which may be preferred over a single isolated substance (Aiyegoro and Okoh, 2009)
. Combining essential oils (EO) can provide a synergistic result. Components of different plants’ EOs have been postulated to work synergistically in a plethora of ways, such as by impacting diverse targets as well as through physicochemical interactions (Vankar and Wijayapala, 2019)