الفهرس 
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Abstract
Summary
This study was conducted in the poultry house of Animal and Poultry Management and Wealth Development Department at the Faculty of Veterinary Medicine Beni-Suef University, Egypt at April 2016 to investigate the effect of rearing broilers under two different stocking densities and using Protexin® probiotics on the performance and welfare. A total number of 240 chicks were purchased from a commercial hatchery and brooded at 33ºC using electric heaters for the first week of age, then were randomly distributed at the end of the first week into four groups with three replicates of eachin 12 floor pens -each measured 1m × 1.6 m- with a new wood shaving litter material to overcome the possible deteriorated air and litter quality that occur during the brooding period as following,Gp1, 48 chicks (16 bird/ replicate) were reared at density of 10 bird/m2without probiotic supplementation “control group”,Gp2, 48 chicks (16 bird/ replicate) were reared at density of 10 bird/m2 with probiotic supplementation, Gp3, 72 chicks (24 bird/ replicate) were reared at density of 15 bird/m2without probiotic supplementation and Gp4, 72 chicks (24 bird/ replicate) were reared at density of 15 bird/m2 with probiotic supplementation, andthe results showed that:
1. The effect of different stocking densities and probiotic “Protexin®” supplementation on the microclimatic conditions surrounding the bird:
Regarding the air quality, the obtained data showed that increasing housing density from 10 to 15 bird/m2 having adverse effect on air quality with regard to the temperature and RH, especially during the last rearing weeks Furthermore, the gaseous emissions were lower than threshold levels which make it possible to house this number of birds with more advanced technology of ventilation to relieve heat stress that was the main cause of deteriorated air quality.
Protexin® supplementation didn’t significantly affect ammonia emission in both densities inspite of the being non-significantly (P˃0.05) decreased in both densities.
Concerning litter quality, HSD result in deteriorated litter quality in term of increased litter temperature, moisture which resulted in a bad litter score that was the worst at the 5th and 6th wks. of the growing cycle. Moreover, limiting floor space might lead to an increase in litter pH. However, increasing the birds number result in a corresponding increase in the litter nitrogen content but unfortunately increased the ammonia nitrogen fraction which was a bad indicator concerning the manure quality as a fertilizer.
Protexin® supplementation failed to achieve a success in decreasing pH at both densities. But having a beneficial effect in reducing litter ammonia nitrogen fraction in both densities but this effect wasn’t to the extent of decreasing ammonia nitrogen level in the HD group to the level even close to the control group where there was a great gap between both groups in the level of this nitrogen fraction, so inspite of this beneficial effect it didn’t achieve the purpose of preserving nitrogen content of broiler’s litter.
2. The effect of different stocking densities and probiotic “Protexin®” supplementation on the broilers performance
Regarding the feed intake, there was a significant improvement in the FI only in the 2nd wk. of the growing cycle with increasing density and continued without significance in the 3rd wk. which then reversed into a significant decline starting from the 4th wk. till the end of the growing cycle, while the whole cycle feed consumption wasn’t significantly affected by SD. Besides, the Protexin® supplementation significantly increased the last two wks., 22-42 and 8-42 d FI in the lower density group but fail to achieve a significant improvement in the FI in the HD group inspite of a significant increase in the 22-42d FI.
Referring to the body weight, it was clear that increasing SD result in a corresponding non-significant improvement in the 2nd wk. BW and a significant improvement of the 3rd wk. BW which will be turned into a decrease starting from the 4th wk. (P˃0.05) passing with 5th and 6th wks. which showed a significant (P˂0.01) decrease in the broiler BW with increasing density. Additionally,the inclusion of Protexin® resulted in a corresponding increase in the broilers BW in both stocking densities and result in decreasing the adverse effect of HSD on the BW.
With regard to the body weight gain, increasing SD resulted in a significant improvement in the starter BWG (P˂0.05), which turned into a significant decline in the 22-42 and 8-42 d BWG (P˂0.01). Moreover, the use of Protexin® didn’t significantly affect weekly BWG but significantly increase the CBWG at both densities.
With reference to the FCR, increasing density resulted in non-significant improvement in the 2nd wk.., 3rd wk. and 8-21 d FCR which turned in a significant adverse effect at the 4th wk. which continued without significance till the end of the cycle while, the 22-42 and 8-42 d CFCR were significantly poorer with increasing density. Furthermore, Protexin® supplementation didn’t significantly affect weekly, 8-21 and 22-42 d FCR, while the 8-42 d CFCR was significantly improved in both rearing densities.
3. The effect of different stocking densities and probiotic “Protexin®” supplementation on broiler’s health:
Increasing SD resulted in decreasing leg health with regard to increased contact dermatitis incidence and production of serious FP, HB and breast lesions. Moreover, the leg strength was altered as indicated by shorter latency to lie duration. Additionally, increasing density resulted in poorer feather condition in the form of significantly (P˂0.01) poor plumage cleanliness score and feather score in HD group
Protexin® supplementation was proved to be a useful strategy to improve leg health especially at higher densities by decreasingfoot pad dermatitis incidence and better CD scores as well as shorter latency to lie duration but failed to improve feather condition at both densities.
4. The effect of different stocking densities and probiotic “Protexin®” supplementation on the stress response of broilers:
• Regarding the mortality, neither HSD nor Protexin® supplementation at both densities have an effect on the mortality %throughout the growing cycle.
• Concerning the physiological indicators of stress, increasing SD caused the serum CS levels to be increased (P˂0.01) at the 4th wk., this increase was continued with significance (P˂0.01) till the 6th wk. of the growing cycle. Moreover, Protexin® supplementation had no significant effect on CS levels at lower SD throughout the growing cycle However, it was succeeded in decreasing (P˂0.01) CS levels at HSD at the last two weeks of the growing cycle.
Broilers reared at HSD didn’t pose oxidative stress as indicated by non-significant alteration in serum MDA levels. But significantly increase brain serotonin levels. Moreover, Protexin® supplementation didn’t significantly affect MDAlevels at both densities but significantly decreased brain serotonin levels at HSD only.
• With regard to the immunological indicators of stress, the serum levels of Anti NDV AB titre wasn’t significantly affected by increasing SD. However, there was a reduced (P˂0.01) mRNA expression of IL6 with increasing density. Protexin® supplementation didn’t significantly affect AB titre or mRNA expression at both densities.
• Referring to the anatomical indicators of stress, increasing SD increased (P˃0.05) liver wt. and decreased lymphoid organs wt. that was indicative for a possible stress, Protexin® supplementation only improved the absolute bursa wt. at lower density group which may be considered an improvement of the immune system.
• Speaking on the ability of broiler to cope with challenges during development, it was reduced with increasing SD as indicated with higher fluctuating asymmetry. Protexin® supplementation improved the ability of the birds to cope with the stress of HSD as indicated by decreased fluctuating asymmetry values.
• The behaviour of broiler as indicator of stress was altered in term of,
Temporary improvement in the feeding frequency in the initial rearing phase followed by marked decline at the later rearing phase. Additionally, it reduced drinking frequency and duration particularly at the 6th wk. of the growing cycle.
Decreased walking behaviour and increase standing frequency especially at the end of the cycle.
Impairment of bird’s lying behaviour and subsequent decrease in sleeping frequency.
Decreased preening, restricted environmental exploration and bird interaction.
Protexin® supplementation improved feeding behaviour expressed in prolonged TFD, in lower density only, with no recorded effect on drinking behaviour. Moreover, it didn’t affect kinesis, rest, sleep, body care and reactivity of broilers at both densities. But birds stocked at high stocking density and supplemented with Protexin® showed no alterations in all behavioural patterns compared to control group, which means that the used probiotic mitigated the recorded impairment effect of HSD on bird’s behaviour.
5. The effect of different stocking densities and probiotic “Protexin®” supplementation on the fear response of broilers:
Increasing SD resulted in increased fear levels as indicated by increased time taken by the bird to make the first attempt to stand (P˂0.05), reduced numbers of attempts to stand (P˃0.05) and longer TI duration (P˂0.01).and Protexin® supplementation failed to decrease fear response of densely stocked broilers.
6. The effect of different stocking densities and probiotic “Protexin®” supplementation on the broiler’s carcass quality:
Increasing SD decreased carcass quality in term of decreased carcass yield, overall acceptability, water loss from broilers meat which adversely may affect meat tenderness and flavor.
Protexin® supplementation didn’t affect carcass and giblet yield but improved overall acceptability score and decreased water loss particularly at HSD.
7. The effect of different stocking densities and probiotic “Protexin®” supplementation on the profitability:
Increasing stocking density significantly increased the yield/unit area (P˂0.01), BCR (P˂0.01), net profit/unit area (P˂0.05) and PI(P˂0.01), however there was a decrease (P˃0.05) in the PEI. This indicated an increase in the economic efficiency with increasing SD.
Protexin® supplementation at both densities resulted in an increased yield/unit area (P˂0.01) and PEI (P˃0.05) on the other hand, it significantly impaired the economic returns by decreasing (P˂0.01) BCR, net profit per unit area and the PI.