Influence of Aloe vera (Aloe barbadensis M.) as an alternative to antibiotics on the growth performance, carcass characteristics and haemato‐biochemical indices of broiler chickens

Abstract Background Medicinal herbs as classes of additives to poultry feeds have proven to be beneficial due to their antioxidant, antimicrobial and antifungal properties. Objective A 6‐week study was conducted to assess the effects of Aloe vera (Aloe barbadensis M.) as an alternative to antibiotics on the growth performance, carcass traits and haemato‐biochemical parameters of broiler chickens. Methods A total of 240 unsexed commercial broiler chickens, 2 weeks old, were randomly allocated to four treatments: T1 (negative control), T2 (positive control, 1 g/L oxytetracycline), T3 (0.5% Aloe vera gel extract) and T4 (1% Aloe vera gel extract) in a completely randomised design (CRD), with six replicates of 10 birds per replicate. The Aloe vera gel extract was administered in fresh drinking water. Results The results revealed across all the treatment groups, no significant (p > 0.05) differences were found in terms of growth performance and carcass traits. However, the mortality rate was significantly lower (p < 0.05) in the positive control and the Aloe vera groups compared to the negative control. Total cholesterol, total glucose, and high‐density lipoprotein values for the experimental groups (T3 and T4) were significantly (p < 0.05) lower than those of the control groups. The values for red blood cell count, haemoglobin content, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration for the birds treated with Aloe vera gel were significantly (p < 0.05) higher than those of the control groups. Conclusions It is therefore concluded that the addition of Aloe vera gel extracts up to 1% in the drinking water could replace antibiotics in broiler chickens without any adverse effects on the health status and the performance of birds.


Study site and duration
The study was conducted at the Poultry Farm of the Department

Experimental material and preparation
Fresh Aloe vera leaves were collected from the university farm. The leaves were cleaned thoroughly with water and the Aloe gel was extracted from the leaf by peeling off the leaves. The latex of the leaves was removed, and the gel was collected into a container. A 10% (w/v) concentrated infusion was prepared by taking 100 g of the fresh gel and putting it in 1 L of hot distilled water.
The Aloe vera gel was blended using an electronic blender and then poured into a glass jar. Distilled water which had a temperature of 52 • C was then poured into the glass jar containing the Aloe vera gel mixture.
The jar was shaken for 2 min to ensure thorough mixing and was then kept for 6-8 h at room temperature before use.

Experimental birds and design
Two hundred and forty 2-week-old Cobb 500 healthy birds of similar weight were selected and allocated randomly to four treatments, namely, T1, T2, T3 and T4. The four treatments were replicated six times, each with 10 birds using a completely randomised design (CRD). T1 (negative control) was provided with basal broiler diet and normal drinking water, T2 (positive control) was provided with basal diet and antibiotic (1 g/L oxytetracycline) in drinking water, and T3 and T4 were provided with basal diets and Aloe vera gel extracts at levels of 0.5% and 1%, respectively, in the drinking water. The standard diet contained a metabolisable energy of 3105.2 kcal/kg and a crude protein of 21.42%.

Housing and management
All the birds were housed in 24 deep litter pens with concrete floors.
Each pen was equipped with wood shaving spread on the concrete floor to a depth of 2-5 cm with a floor space of 0.2 m 2 per bird. Feed and water were provided ad libitum throughout the experiment. The birds were vaccinated against Gumboro and Newcastle diseases. They were also medicated against coccidiosis using a coccidiostat (amprolium).

Performance parameters
The chicks were weighed at the start of the experiment and then on a weekly basis after that. The chicks were weighed individually in each replicate, and weekly weight gain (g) was estimated by subtracting the initial weight from the weight at the end of the week. Weekly feed intake (g) was calculated by subtracting leftover feed from the total feed provided. By dividing feed consumed and weight gain, the feed conversion ratio (FCR) was obtained. Fresh drinking water given to the chicks was daily measured before serving. The difference between the amount of water given and the amount of water left over on a daily basis per replicate was used to calculate water intake (mL). Each pen was checked daily for the occurrence of death and the dead birds were immediately transported for post-mortem. Mortality rate was expressed as the percentage of the number of birds that died in a pen and the total number of birds that were in the pen at the onset of the study.

FCR = feed inake weight gain ,
Mortality rate (%) = number of dead birds total number of birds per pen × 100.

Carcass analysis
At the end of this study, two birds from each replication were chosen based on the group's average body weight and humanely sacrificed by jugular vein haemorrhage following a 12-h fast (with free access to water) for internal organ weights and carcass analyses. Birds were slaughtered, feathers plucked off and eviscerated. The carcass was cut into many pieces (breast, back, thigh, drumstick, both wings, neck and shank). The internal organs weight, dressed weight, breast, thigh, drumstick, back, wing, neck and shank were expressed as a percentage of the live weight using the formulae: Primal cut (%) = weight of primal cut live weight × 100, Internal organ ( %) = Organ weight live weight × 100.

Blood analysis
Blood samples were taken from two birds from each replication at random. Blood samples were taken from the jugular vein using a 2 mL sterile needle and syringe into anticoagulant (EDTA) bottles after the feed was withdrawn. Total red blood cells (RBC), haemoglobin (HB), lymphocytes, mean corpuscular volume (MCV), thrombocytes s, haematocrit (HCT) and white blood cells (WBC) were measured using a Haematological Auto Analyzer (AR 6300, ARI Medical Technology Co., Ltd.), and biochemical factors were measured using a 'FlexorJnr autoanalyzer' (Vital Scientific, NV). In a macro centrifuge, blood samples obtained for serum biochemistry were centrifuged for 10 min at 3000 rpm (revolutions per minute) to create a serum for biochem-ical examination. The serum samples were stored frozen until they could be analysed further. Before analysis, the frozen serum samples were allowed to thaw, and the thawed serum was pipetted into dry clean tubes and refrigerated at -20 • C. Total protein, total cholesterol, triglycerides, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) were among the assay parameters assessed by serum enzyme-linked immunosorbent assay (ELISA) (LDL).

Statistical analysis
The entire data collected on performance (feed intake, body weight gain, water intake and FCR), serum biochemistry (total cholesterol, total protein, triglycerides, LDL and HDL) and haematology (WBC, RBC, Hb, HCT, lymphocytes, thrombocytes and MCV) were computed and subjected to the analysis of variance (ANOVA) using Minitab Software (Version 18.1) at p < 0.05. Differences between treatment means were separated using the Tukey's test.  Table 2 presents the relative carcass characteristics and relative internal organs weights. All the carcass parameters and the weight of the organs did not differ (p > 0.05) across the treatment groups.

Blood indices
The effect of Aloe vera on the blood biochemical parameters of the birds is shown in Table 3. The values of total cholesterol were significantly (p < 0.05) lower in the Aloe vera-supplemented groups than that in the control groups. The level of triglyceride in the blood of the Aloe veratreated birds decreased (p < 0.05) as the level of the supplementation increased. The Aloe vera treatment groups had lower (p < 0.05) levels of triglycerides when compared to the control groups although, among the control groups, the positive control group recorded lower levels (p < 0.05). For HDL levels, the 1% Aloe vera-supplemented group was TA B L E 1 Effects of Aloe vera gel extracts on the performance of broiler chickens during 2-8 weeks. The impact of Aloe vera supplementation on haematological parameters is presented in Table 4. Red blood cell count was higher (p < 0.05) in the Aloe vera treatment groups (T3 and T4) as compared to those of the control groups, even though, among the control groups, the positive control was better (p < 0.05). The birds giving 0.5% Aloe vera treatment recorded the highest (p < 0.05) white blood cell count followed by T2 and T4 with T1 recording the lowest (p < 0.05). Haemoglobin and HCT levels were significantly (p < 0.05) superior in the Aloe vera treatment groups compared to the control groups. Mean corpuscular volume increased (p < 0.05) as the level of Aloe vera increased but this was appreciably low (p < 0.05) relative to the negative control. The values of MCH and MCHC were statistically superior (p < 0.05) in the Aloe vera groups when compared with the control groups. The thrombocyte level in the positive control group was significantly superior to all the other treatments but thrombocyte levels decreased (p < 0.05) as the level of Aloe vera increased.

DISCUSSION
The influence of Aloe vera on the growth performance of the birds revealed no significant difference. The absence of significant differences in this study as far as feed intake is concerned, suggests that the Aloe vera gel extract did not pose any negative effect on feed intake.
This finding agrees with the findings of Shokraneh et al. (2016) who also did not find differences in feed intake after giving broiler birds Aloe vera extract supplements. There were no significant differences among the various treatments for water intake. This result is consistent with the findings of Online et al. (2017) who also recorded no significant effect on water intake by Aloe vera gel extracts supplementation in broiler drinking water. However, Shokraneh et al. (2016) recorded an increase in water consumption with a high level of Aloe vera extract supplementation. This increase in water intake reported by the authors could be due to environmental influences or the fact that higher inclusion than the levels in this study was used. Furthermore, the weight gain of broiler birds given the control diets was not differ- The negative control recorded the highest mortality rate compared to the other treatment groups. The differences can be attributed to the antibacterial, antioxidant and antifungal properties of Aloe vera gel extracts, which helped the birds in the Aloe vera and antibiotics groups to fight against disease infection. Shokri et al. (2017) observed that Aloe vera is capable of boosting the bird's immune system, and this could help the birds in fighting against infections. Likewise, Rajasekaran et al. (2005) found in their study that Aloe vera is capable of improving birds' immunity and promoting cell repair. Darabighane and Nahashon (2014) recorded an increase in white blood cell count for broilers treated with