Physiological Response of Broiler Chickens to Varying Dietary Levels of Scent Leaf (Ocimium Gratissimum) Meal

Location of the Experiment

The experiment was conducted at the Poultry unit of the Livestock Teaching and Research Farm of Prince Abubakar Audu University, Anyigba. Anyigba lies between Latitude 70 151 N and 70 211 E of the Equator and Longitude 70 111 N and 70 321 E of the Greenwich Meridian with an altitude of about 420m above Sea level. The zone is characterized by 6 -7 months of average annual rainfall of about 1600mm and the daily temperature ranges between 250C and 350C [8].

Collection, Processing and Preparation of the Experimental Diet

Fresh scent leaves (Ocimum grattisimum) were obtained from the Prince Abubakar Audu University environment. The samples were dried under the shade to retain its greenish coloration and further ground into powder using a hammer mill. The obtained powder was packed in a polyethylene bag and preserved in the feed storage room until used in fortifying the feed as additives. The result of the proximate analysis of the Scent leaf meal is shown in Table 1. Commercial feed was purchased and used throughout the experimental study. Scent leaf meal was incorporated into the feed at 0.00%, 0.45%, 0.75% and 1.05% by thoroughly mixing the feed with the phytogenic plant.

Experimental Design and Management of Birds

Ninety-six (96) four weeks-old broiler chickens were used for the experiment. On the twenty-eight-day, the birds were weighed and randomly allocated to four experimental treatments in a Completely Randomized Design (CRD). Scent leaf (Ocimum grattisimum) meal was incorporated at 0 %, 0.45 %, 0.75 % and 1.05 % and designated as T1, T2, T3, and T4 respectively. Each treatment had twenty-four birds (24) with three replicates of eight (8) birds each The birds were raised on deep litter system. The experiment lasted for four weeks. Feed and drinking water were provided ad libitum and standard routine management practices were observed.

Statistical Analysis

All data collected were statistically analyzed using the one-way Analysis of Variance (ANOVA) with the aid of SPSS version 16 (SPSS, 2007). Where there were significant difference, the data were subjected to Fisher’s Least Significant Difference.

Physiological Response of Broilers to Varying Dietary Levels of Scent Leaf Meal

Effect of varied inclusion levels of scent leaf meal on the physiological response of Broilers is presented in Table 2. Result obtained revealed that the physiological parameters of respiration rate and pulse rate were progressively reduced across the treatments (p > 0.05) as the inclusion level of scent leaf meal increased. Rectal temperature was not affected by treatments (p > 0.05). Values obtained for the rectal temperature ranged from 41.09 to 41.94 0C. Respiratory rate had a steady decrease with increase in the scent leaf meal inclusion levels with values ranging from 66.91 b/min to 72.41 b/min. Value range obtained for pulse rate followed a similar trend with highest value of 225.00 b/min obtained in the control and least value of 219.54 b/min obtained in the birds fed 1.05%SLM.

a,b==means with different superscripts along the same row show significant difference at p<0.05; SEM= Standard Error of the Mean; LOS = level of significance; *= Significantly different; NS=Not Significantly Different. Table 2: Physiological response of broilers to varying dietary levels of scent leaf meal.

The physiological evaluation revealed that rectal temperature ranged from 41.09 0C to 41.94 0C. Webb P, [9] opinioned that the formation of circadian rhythm is hypothesized to be related to the difference between heat production and dissipation generated from variation of dietary treatment. This therefore implies less energy was generated with increase in Ocimium gratissimum leaf meal inclusion. This is in line with the report of Deeb N, et al. [10] who reported that the body temperature of a broiler cloaca is not always constant, but displays significant changes with change in nutrition, the biochemical processes as well as the climatic condition. Hashemi, et al. [11] reported that scent leaf has proven natural, less toxic, residue free pharmacological properties, resulting in a stress-free physiological state in broiler chickens. This implies that reduction in rectal temperature might not be significant except there is significant nutrition or climatic changes [12]. Anugom MI, et al. [13] reported that there was no significant difference in the feed intake and rectal temperature of experimental birds fed 1% scent leaf meal. Odoemelam KI, et al. [14] also noted no significant difference in the feed intake, rectal temperature as well as heart rate of broilers fed 0.75% inclusion level of scent leaf. Ogbu FI, et al. [15] reported rectal temperature value range of 39.800C to 40.940C for broilers fed scent leaf meal at 0 to 1% inclusion level. However, Okpe AA, et al. [16] reported rectal temperature value range of 39.94 to 42.60°C for broilers raised under feed restricted conditions.

Significant variation (P<0.05) for respiratory rate was obtained with significant higher values of 72.14 b/ min and 72.00 b/min obtained in the control and 0.45% SLM (Scent leaf Meal) inclusion level. This result implies reduction in respiratory rate as rectal temperature decreases numerically with increasing inclusion level of scent leaf meal. This suggests that birds on 0.75% SLM and 1.05% SLM enjoyed better homoeostatic condition. Values obtained for respiratory rate were in harmony with values obtained by Lin H, et al. [17] who reported respiratory rate range of 58.90 to 71.43b/min for 14 days old broilers.

Values obtained for pulse rate significantly (P<O.05) decreased steadily with increase in the inclusion levels of scent leaf meal. Value of 225.00 b/min obtained in the control was within the value of 206.50 to 367.46 reported by Buyse, et al. [18] when broilers were fed diet containing varied metabolizable energy content. The significant improvements in physiological parameters of the broiler chickens with increase in the inclusion levels of scent leaf as observed in the rectal temperature, heart rate and breath rate may be due to the phytochemical properties and the mineral composition of SLM in the diets [12]. The phytochemical components such as alkaloids and saponins posess antibacterial properties, and may have acted as homoeostatic regulators which promotes the improvement of the physiological parameters. Moreover, Lin H, et al. [17] had reported that there is a correlation between cloaca temperature, heart rate and breath/min and also that factors that significantly increase body temperature of the bird would alter the physiology of the animal.