Continuous increases in population have increased the demand for animal proteins, especially poultry, because of its low price compared to other animals. Therefore, poultry production is increasing significantly worldwide1. Restrictions on the use of in-feed antibiotics have affected animal production in many countries. Supplementation with antibiotics has a risk of inducing not only cross-resistance but also multiple resistances2. The uncontrolled and unlimited use of antibiotics also leads to the accumulation of residues, which is harmful for animals and their products3. Consumed antibiotics residue can cause allergies, poisoning and pathogen resistance4.
Researchers have great interest in identifying natural growth promoters to enhance poultry production5. Natural growth promotors, such as prebiotics, probiotics, symbiotic, enzymes, spices, herbs, plant extracts, etc., can be extensively used to feed broiler chickens without any adverse effects on the performance of the birds6. Some plants containing various essential oils have been used as alternative remedies by some researchers7. Plant extracts can improve the feed conversion ratio, increase carcass quality, decrease the market age of the broiler and reduce their rearing cost8. For example, curcumin extracted from turmeric has biological functions such as anti-inflammation, anticoagulant and hypolipidemic9 and antibacterial activities10 and it can destroy bacterial cell membranes11.
Residues from herbal medicine processing in pharmaceutical plants creates a large amount of waste (herb residues), which consists mainly of environmental pollution and medicinal waste12. The active ingredients of traditional Chinese herbal medicine are the secondary metabolites of plants and the low decoction efficiency leaves approximately 30-50% of the medicinally active substances in their herb residues13. In addition, herb residues are mostly disposed of through stacking in the open, sanitary burials, or burning, causing serious environmental pollution, especially affecting water quality14. The huge amounts of herb residues produced by the continuous development of the herbal medicine industry have become a serious problem for large pharmaceutical companies12.
The broiler industry in Thailand is one of the most important industries in the country. One of the problems in this broiler industry is the spread of diseases, resulting in an increase in morbidity and/or mortality15. Moreover, increasing levels of broiler production are causing many environmental problems. Chicken manure can be a source of ammonia (NH3) emissions, which impact both animal and human health16. The study of Roberts et al.17 found that dietary fiber lowered NH3 emissions from laying hens. Lokaewmanee18 studied the effects of chili pedicle meal on the ammonia nitrogen of broiler chickens. Their results also demonstrated that dietary fiber reduced ammonia nitrogen production by poultry. However, these studies did not undertake any investigation of the effects of herb residues on growth performance, economic return, carcass quality, fecal moisture or ammonia nitrogen of broilers.
Therefore, the possibility of utilizing herb residues for feeding broilers is promising. The present study was carried out to investigate the effect of using herb residues as an unconventional feedstuff in broiler diets on growth performance, economic return and fecal ammonia nitrogen levels.
MATERIALS AND METHODS
This study was conducted at the Animal Farm of the Kasetsart University Chalermprakiat Sakon Nakhon Province Campus from August to September 2019.
Preparation of the herb residues: The herb residues were collected from the Laboratory of Chemistry, Department of Science, Faculty of Science and Engineering, Kasetsart University Chalermprakiat Sakonnakhon Province Campus, Thailand. Zingiber cassumunar, Kaempferia galangal and Curcuma aromatic were extracted by solvent extraction of 95% ethyl alcohol and evaporating by rotary vacuum evaporator. Essential oils from the solvent extraction were used for cosmetics, while all of the herb residues were dried for 1 day in an oven at 65°C and then ground and passed through a 2 mm screen. The dry matter, crude protein, crude fiber, crude fat, crude ash and gross energy contents of the herb residues were determined using the standard methods according to the Association of Official Analytical Chemists and are shown in Table 1. The herb residues were stored in plastic bags at ambient temperature before being mixed into the feed.
Experimental design, birds and management: The animal care and protocol was approved by Kasetsart University, Thailand. The experiment was performed using 160 individual broilers (Ross 308 strain), which were divided into four treatment groups with four replicates (10 birds in each replicate). A corn and soybean meal-based diet (Table 2) formulated to meet nutrient requirements was left unmodified in the control group (CT). In the ZC group, a diet containing 3 g kg1 Zingiber cassumunar residues was provided. In the KG and CA groups, Kaempferia galangal and Curcuma aromatic residues comprised 3 g kg1 of the diet, respectively.
The herb residues were first mixed with a premixture, subsequently mixed with the other dietary ingredients and then stored in plastic bags before feeding. The experimental diets were prepared every week. The diet was offered to the broiler chickens twice daily ad libitum and all birds had free access to water. The light program consisted of 24 h light and the birds were reared in open-sided houses with the temperature maintained at 33°C during the rainy season in northeastern Thailand.
Growth performance and economic return: The initial weights of the birds were taken at the start of the study and live weight measurements were subsequently recorded on a weekly basis. The feed intake was determined on a daily basis as the difference between the quantity of feed administered the previous day and the quantity left the next morning. The feed conversion ratio was calculated as the ratio of the feed intake to the body weight gain. All pens were checked for viability daily. The feed cost per gain, salable net return, net profits return per bird and return of investment of each group were calculated and compared with those of the control group.
Determination of carcass quality: On day 42, a total of 20 male chickens randomly selected from each treatment were slaughtered. The dressing weight, eviscerated weight, abdominal fat weight, breast muscle, wing muscle, thigh muscle and drumsticks muscle were weighed according to Chen et al.19. The shear force was determined using a texture analyzer (TA.XT Plus, Stable Micro System Ltd., United Kingdom). Meat samples were manually trimmed, 45 min after the muscles had been separated, into 1.0 cm (width) ×0.5 cm (thickness) ×2.5 cm (length) strips parallel to the muscle fiber from the main portion of the muscle and sheared vertically20. Each sample was measured three times along the muscle fiber.
Determination of ammonia nitrogen: Ammonia nitrogen was measured during the last week of the feeding period. The birds were randomly allocated to the four dietary treatment groups (four birds/group) of similar mean body weight and then moved into individual cages. The feces were subsequently collected over three consecutive 24 h periods on plastic trays placed within each cage. The feces from each of the 24 h periods were pooled within groups and stored at -20°C until analysis. Fecal ammonia nitrogen was analyzed by the AOAC method21.
Data analysis: Data collected were subjected to one-way analysis of variance (ANOVA) following the general linear model procedure22. Differences between treatments were tested using Duncan’s new multiple range test at the 5% significance level23. The results of the statistical analyses are shown in the tables as the mean with standard errors.
RESULTS AND DISCUSSION
The number of studies investigating the impact of herb residues on broiler chickens is limited. The results showed that the CA treatment significantly (p<0.05) increased the body weight gain, average daily gain, feed conversion ratio and productive index (Table 3). These results agree with the finding of González-Alvarodo et al.24 and Jiménez-Moreno et al.25, who reported that dietary supplementation with oat hull, soy hull and sugar beet pulp improved the productive performance of broilers. However, Lokaewmanee18 found that the addition of 0.5-1.5% chili pedical meal reduced the body weight gain and average daily gain of broilers and Sklan et al.26 reported that adding increasing levels of dietary fiber (80-90 g kg1) to turkey diets showed a negative effect on growth rate and feed efficiency. There was no significant difference in feed intake or viability among the CT, ZC, KG and CA groups at 42 days of age. The crude fiber of Zingiber cassumunar residues, Kaempferia galangal residues and Curcuma aromatic residues were 1.56, 2.31 and 0.22%, respectively.