BACKGROUND: Reducing the protein and amino acid content of diet or altering the dietary electrolyte balance were suggested as the effective strategies to prevent the harmful effects of the heat stress in poultry.OBJECTIVES: This study surveyed the effects of various levels of threonine and dietary cation-anion balance on the broiler chickens under the heat stress conditions.METHODS: 700 one-day-old male broilers (Ross 308) were used for 6 weeks under high- temperature conditions. This experiment was conducted using a 2 × 3 + 1 factorial experiment based on a completely randomized design, with 7 treatments (5 replicates per treatment and 20 birds per replicate). Experimental factors included two threonine concentrations (recommended level and 10 % above recommended level) and three dietary electrolyte balances (175, 250, and 325 mEq/kg). The control group considered the treatment with a normal threonine concentration (recommended level) and a dietary electrolyte balance of 250 mEq/kg under optimal temperature conditions.RESULTS: Although there was no interaction between threonine level and electrolyte balance, the electrolyte balance of 175 meq/kg increased the performance index compared to the electrolyte balance of 250 or 325 mEq/kg (P<0.05). The villus height to crypt depth ratio and villus surface area in the jejunum improved with an electrolyte balance of 175 or 250 mEq/kg (P<0.05). A decrease in the dietary electrolyte balance increased in the nitrogen-corrected apparent metabolizable energy (P<0.05). Besides, an increase in the population of lactobacilli and bifidobacteria in the cecum, as well as an increase in protein digestibility, were observed by increasing levels of threonine in the diet (P<0.05).CONCLUSIONS: Based on these results, a high level of threonine or a low electrolyte balance in diet (175 mEq/kg) may improve the performance, metabolizable energy, and intestinal microbial flora of broilers reared under heat stress.

This study was conducted to investigate the effects of the sources and levels of dietary copper supplementation on broiler chickens. A 37-day feeding trial was accomplished using 192 one-day-old unsexed Arbor Acres broiler chicks which were randomly allocated into four groups with different strategies of copper supplementation. The first group was the negative control and fed on diets containing copper-free mineral-vitamin broiler premix. Diets of the second group were supplemented with copper sulfate (Cu2SO4) at the level of 7.5 mg/kg. The third and fourth groups were fed on diets supplemented with copper nanoparticles (Cu-NPs) at the levels of 7.5 mg/kg and 3.75 mg/kg, respectively. Growth performance, carcass characteristics, copper concentrations, serum antioxidant bio-markers and mRNA of metallothionein and ceruloplasmin were evaluated. Results of growth performance showed that Cu-NPs significantly (P ≤ 0.05) increased body weight gain and feed utilization compared to an equal quantity of Cu2SO4. No adverse effect on growth performance occurred when Cu-NPs were supplemented at half of the level of Cu2SO4. Dressing and thigh yields were significantly (P ≤ 0.05) increased in birds in the fourth group. Total antioxidant capacity, malondialdehyde level and transcription of ceruloplasmin were not significantly affected by the tested copper sources or levels. The superoxide dismutase enzyme activity and transcription of metallothionein were significantly (P ≤ 0.05) increased by the replacement of Cu2SO4 with the same quantity of Cu-NPs. Our findings suggested that Cu-NPs could be a superior dietary supplement of copper in broiler chickens’ diets over Cu2SO4, with possibility of quantity reduction.

In the study, zinc oxide nanoparticles (ZNOPs) at concentrations of 20, 40, and 60 mg/kg were tested for their antimicrobial action against the oocysts of Eimeria tenella. The oocysts of E. tenella were isolated from the feces of broilers received at the veterinary hospital in Diwaniyah Province and initially diagnosed by compound optical microscopy. The oocysts were confirmed molecularly by polymerase chain reaction targeting the ITS1 gene with a molecular weight of 409 bp. The results in the first week showed that ZNOP concentrations of 20 and 40 mg/kg possess various activities against E. tenella, while 60 mg/kg was the most effective in reducing excreted oocysts compared to the positive control and amprolium group, along with the appearance of mild symptoms and a mortality rate of 0.8%. In the second week of infection, excreted oocysts and mortality rates generally decreased in all treated groups. A comparison of all groups showed that the 60 mg/kg ZNOP-treated group had a significantly lower number of excreted oocysts, and all birds in this group recovered during the second week of infection. These findings revealed the prospect of using ZNOPs against E. tenella in challenging situations of the appearance of resistance to anticoccidial agents.