Generally, Chicks need some hours or days to have access to feed due to the time required for hatchery treatments and transport to the rearing farm. This delay in feeding impacts negatively on their future performance. Early feeding has more beneficial effect than feeding high-quality diets after a delay in feeding1-3. In commercial poultry rearing, getting a good start at the hatchery is an important factor to maximize profits. It is often thought that, feeding the chick during the embryonic stage would provide more nutrients necessary for improved starting weights, better feed utilization and faster growth. Thus, researchers are focusing on a new feeding strategy in order to increase the nutrients at the embryonic stage including in ovo feeding. Recent articles have focused on the effect of in ovo feeding on hatchability and early growth performance. In an earlier study, Ohta et al.4 showed that amino acids injected into the yolk sac at 7 days of incubation, did not affect hatchability but chick body weight increased relative to egg weight prior to incubation. In another experiment, Uni and Ferket5 showed that, in ovo feeding positively impacted hatchability, hatchling weights and this advantage was observed to be sustained until at least 35 days of age. Besides, the advanced development of the intestinal mucosa was also observed. So far, several studies have been conducted by using nutrients that have been applied for in ovo feeding include amino acids6-8; carbohydrates9,10; modulators11,12 and minerals13.
Among the minerals, Selenium (Se) is one of the elements that has many benefits for poultry but its use is very limited. It has been proven that Se deficiency in the poultry diet causes pathological problem that can affect the growth performance of poultry14. Many studies have been conducted on Selenium because of its physiological importance in the organism15,16. Selenium acts as a modulator of reproductive system, growth performance, immunity function and aging (or anti-aging) process in the organism17. Selenium acts as a component of the enzyme glutathione peroxidase (GSH-Px). Thus it plays a central role in maintaining the integrity of cellular membrane. Hariharan and Dharmaraj18 found that Selenoprotein derivative such as Thioredoxin reductase plays important role during oxidative stress and inflammation in wound healing process. With all these properties, Selenium can be considered as an ideal dietary supplement in poultry industry to enhance growth and the overall production performance. Although preliminary studies are underway in different laboratories to evaluate the effect of Selenium on the poultry performance, many of these studies have only used it as a component or supplement of feed ingredient. There is a scarcity of studies available on the use of Selenium as nutrients for in ovo administration. Thus the aim of this study was to investigate the effect of in ovo injection of Selenium on hatchability of Isa Brown fertile eggs and on post hatch performance of progenies.
MATERIALS AND METHODS
Experimental site: The experiment was carried out at the laboratory of poultry production of Regional Centre of Excellence in Poultry Science situated at the agronomic experimental station at the University of Lomé in Togo. All study protocols used in this study were approved by the Centre of Excellence in Poultry Science Animal Used and Care review committee, University of Lome in Togo.
Experimental design: A total of 750 hatching eggs from Isa Brown breeders were used for this study. Prior to the incubation, the eggs were numbered and weighed. The eggs were then incubated at 37.8°C, relative humidity of 60% and were turned once every hour at 90° angle. At day 18th of incubation, 600 incubated eggs with evidence of live embryos were divided into five (5) groups that were: (T0) eggs without any injection, (T0+) eggs injected with the saline solution, (T10) eggs injected with 10 μgSe, (T20) eggs injected with 20 μgSe, (T30) eggs injected with 30 μgSe. Selenium was injected by drilling two holes with a syringe needle after candling the eggs. The different solutions were injected into the eggs through the holes. The appropriate solution corresponding to each group of eggs was injected at 0.1 mL per egg using an automatic syringe. After the injection, both holes were sealed with adhesive paper tape and the eggs were transferred into the hatching baskets then placed in the hatcher for hatching. From 456-516 h, after every 3 h, the hatching times were recorded. After hatch, the quality of the chicks, the relative organs weight and blood parameters were determined. The chicks were then reared and fed ad libitum with the standard feed (Table 1) and chicks weight was recorded weekly during 6 weeks.
Selenium solution administration: Five milligrams of Selenium were dissolved in 10 mL of a physiological saline (NaCl 9‰) and vortex to obtain a solution of 500 μgSe mL1. Then, the mother solution was diluted successively with NaCl 9‰ to obtain different solutions of 400, 300, 200 and 100 μgSe mL1.
The test product L-Seleno-methionine was provided by Orffa additive company.
Hatching events: Between 456 and 516 h of incubation, the eggs were removed from the hatcher and checked after every three hours to determine the Internal Piping (IP), External Piping (EP) and Hatching time (Ha) for each egg. At the end of the incubation, hatching time for each egg was determined by calculating the difference between the time when the eggs were set in the incubator and the time when the eggs were hatched.
Hatchability and chick quality assessment: Hatched chicks from each treatment were removed, counted to determine the hatching rate and then Tona scoring method19 was used to assess the chicks quality. For the quality assessment, 10 chicks were removed from each treatment and every chick was assessed on the basis of physical parameters including reflex, down and appearance, eyes, conformation of legs, navel area, yolk sac, remaining membranes and yolk. Non hatched eggs were counted and then opened to determine the time of the embryo mortality (Early mortality, late mortality, mortality at internal or external piping).
Relative organ weight and blood parameters: A total of 6 hatched chicks per treatment were selected and sacrificed through cervical dislocation. Blood samples were collected in Eppendorf tube and centrifuged at 3000 rpm for 15 min for serum collection. Blood parameters (total protein, triglyceride, aspartate transaminase, alanine transferase, albumin and uric acid) were determined per treatment by the spectrophotometric method using EPOCH 2 spectrophotometer and commercial kit manufactured by CYPRESS DIAGNOSTIC. Organs (liver, yolk sac and heart) were removed and weighed to determine the relative weight of the organ.
Bird management and feeding: A total of 60 hatched chicks per treatment except the positive control group were selected. They were divided into 4 replicates of 30 chicks each. Chicks were weighed individually and reared for 6 weeks on deep litter system. Feed (Table 1) and water were provided ad libitum. Body weight, weight gain, feed intake and feed conversion ratio was calculated weekly.
Statistical analysis: Data collected were expressed as Mean±standard error (SE) of mean. Statistical Analysis was performed using a statistical software Graph Pad Prism 5. Differences of p<0.05 were considered statistically significant. The effects of the treatments were analysed using one way ANOVA followed by Turkey test for Comparisons among means.
Effect of Selenium inoculation on incubation duration: Table 2 shows the effect of in ovo Selenium administration on internal, external and hatching duration. The results showed that the external piping (477.5 h) and hatching (468.7 h) time was significantly (p<0.05) shortest in the negative control group (T0) compared to other treatments. The highest hatching duration was observed in T20 group (eggs injected with 20 μgSe egg1) while the highest external piping time was observed for eggs injected with the saline solution. However, the incubation duration between internal and external piping; external piping and hatching did not show any significant (p>0.05) difference for all the treatments.
Effect of in ovo inoculation of Selenium on eggs hatchability, embryonic deaths and chick’s quality: Figure 1 shows the effect of in ovo injection of Selenium on egg hatchability. No significant (p>0.05) difference was observed across treatments.
The effect of Selenium inoculation on embryonic mortality rate is presented in Fig. 2. The mortality rate was significantly (p<0.05) higher for the eggs that received the saline injection compared to others.
Figure 3 shows the quality of the hatched chicks assessed by Tona score. The higher concentration of Selenium in the injected solution significantly (p<0.05) increased the quality of chicks. Chicks quality in treatment T20 and T30 were significantly (p<0.05) higher compared to the negative control group (T0). Whereas the chicks quality in T0+ (positive control) and T10 were similar (p<0.05).
Effect of Selenium inoculation on day old chick’s organ relative weight and serum biochemistry profile: Table 3 shows the effect of in ovo inoculation of Selenium on relative organ weights of day old chicks. There were no significant differences (p>0.05) in the different treatments with respect to the relative yolk sac and liver weights. In contrast, the relative weight of the heart was significantly (p<0.05) lower for the chicks in the treatment T0+ compared to others.
The serum biochemistry profile is shown in Table 4. No significant (p>0.05) difference was observed across treatments.