Broiler Chickens Fed Chromium Propionate Supplemented Diets in a Tropical Environment: Serum Biochemical and Intestinal Morphology

— Aims: The effects of dietary supplementation with Chromium Propionate (CrProp) on serum aspartate aminotransaminase, alanine aminotransaminase, and intestinal morphology in broiler chickens are investigated in this study. Study Design: The completely randomised design was used for this study. Methodology: A total of 644 Cobb 500 broiler chickens were randomly assigned to eight dietary treatments (10 birds per replication). Diets 1 to 4 were designed by dividing a base diet into eight equal halves. Diets 1 to 4 were supplemented with 0, 0.4, 0.8 and 1.2 mg/kg CrProp, respectively. For a 42-day trial period, the birds had unrestricted access to feed and water sources. The gross pathological alterations were documented during necropsy. The intestinal tissues were fixed in 10% buffered formalin for histological investigation. Results: Serum ALT and AST levels were measured to investigate Cr toxicity. There was a significant increase with CrProp supplementation, indicating that the Cr levels administered were hepatotoxic. Intestinal morphology was also enhanced by CrProp supplementation. Conclusion: In conclusion, serum metabolites such as ALT and AST were affected following 0.8 mg/kg of CrProp supplementation, and jejunal morphological qualities were improved.


INTRODUCTION
Poultry meat is the most accessible protein source for humans in most countries. However, the poultry sector may be limited by many problems, including high or low environmental temperature, high stocking density. Heat stress is one of the main problems encountered within the poultry sector (Meremikwu et al.,2013;Shakeri et al.,2020). The tropical regions with high ambient temperature and humidity were more susceptible to high heat stress than the polar or temperate regions (Zhao et al., 2015). Notably, in Nigeria, the high environmental temperature may be responsible for reduced performance and increased mortality (Oguntunji and Alabi 2010; Yousaf et al., 2019).
In addition, heat stress has a negative impact on intestinal development, resulting in a decrease in nutrient utilisation (Makanjuola and Adebiyi, 2012).
Chromium propionate, as an organic form of Cr, was approved as a source of Cr in broiler diets, and 200 μg/kg Cr from chromium propionate was recommended in broiler chicken complete feed by the Food and Drug Administration (FDA, 2020), Dietary chromium (Cr) supplementation has been shown to increase growth performance (Huang et al.,2016) and immunological responses (Bahrami et al.,2012) in broiler chicks under heat-stressed conditions. Studies also showed that Cr (III) could induce histopathological changes and oxidative stress  3 24 in the liver and kidney in chicken . In low content, trivalent chromium can promote the growth and development of chickens, thereby improving the quality of their meat (Piva et al.,2003), which is the potential reason why Cr is added into animal feed. Studies of chromium propionate have focused on broilers (Brooks et al., 2016;Xiao et al., 2017;Luo et al.,2019). Its importance in stress situations in animals and birds is becoming more widely recognized, and it aids in reducing the adverse effects of environmental and nutritional stress. Besides the reported beneficial effects of Cr, there is also a need for studies on the potentially toxic impact of wrong or inappropriate dosage in poultry.
This research focused on how dietary supplemented chromium propionate (CrProp) affected broiler chickens' blood aspartate amino transaminase, alanine aminotransaminase, and intestinal morphology.

Experimental Diets and Animals
A basal diet each was prepared for the starter (age 1-3 weeks) and the finisher (age 4-6 weeks) phases (Table 1) and analysed for proximate composition [AOAC.1995]. The basal diets were sundered equally into eight parts and labelled diets 1to 8 and supplemented as follows:

Blood Sample Collection and Analysis
Blood samples were collected from the jugular vein of three birds per treatment group randomly on day 42 of the experiment in plain tubes were immediately transferred to the laboratory. The blood samples in plain tubes was allowed to clot and was serum harvested and stored at −80°C to determine aspartate aminotransferase and alanine aminotransferase in serum biochemical analyzer (Dia-CHEM 240 Plus). was measured from the villus tip to the villus crypt junction, and the crypt depth was measured from the crypt base to the crypt-villus transition region. The surface area of the villus was calculated using the formula (2p) (villus width/2) (villus length).

Data Analysis
All data were subjected to analysis of variance from the General Linear Model stratagem for complete randomised design with 4 CrProp levels factorial setting of treatments. The data were checked for CrProp, and When the treatment out-turn was significant (P<0.05), means were differentiated using Duncan's multiple range test using SPSS version 28.

III. RESULTS
The AST concentration of control group, 0.4, 0.

IV. DISCUSSION
The AST enzyme is one of the indicators used to determine whether or not an individual has liver impairment. AST enzyme is found in cytosolic and mitochondrial isoenzymes of the liver, skeletal muscles, heart muscles, kidneys, brain, pancreas, lungs, leukocytes and red blood cells. On the other hand, the AST enzyme is less sensitive and specific for detecting liver disease (Zachariah et al., 2017). There were significant differences in AST concentrations in the 0.4, 0.8 and 1.2 mg/kg CrProp supplemented diets compared to the control group. The increase was possible because of the increased Chromium concentration in the diet. However, the findings contradicted those of Liang et al. (2021), who found that Cr supplementation reduced aspartate transaminase (AST) activity considerably. Because the AST enzyme is specific to the liver and other body tissues, an increase in this enzyme does not always suggest liver damage. The ALT enzyme was observed to increase in the 0.4, 0.8 and 1.2 mg/kg CrProp supplemented diets compared to the control group, and the increase was statistically significant. Because this cytosolic enzyme was present in the highest amounts in the liver and was more selective in detecting liver function deterioration, ALT enzymes were a stronger predictor of liver damage than AST enzymes (Thapa and Walia, 2007). Because ALT enzyme activity in the liver is about 3000 times that in the serum, Kim et al. (2008) observed that ALT released from damaged liver cells would enhance the measured activity of the ALT enzyme in the serum in the case of hepatocellular injury or death. According to Ognik et al. (2020), the increase in the ALT enzyme caused oxidative liver damage, which resulted in histological abnormalities in the liver. As a result, reactive oxygen species (ROS) produce more free radicals, damaging effects on membrane phospholipids and causing a wide range of cell damage. significantly influenced by chromium intakeSerum ALT and AST levels were measured to investigate Cr toxicity, and there was a significant change with Cr supplementation, revealing that supplemented Cr levels were hepatotoxic. The finding was inconsistent with Bakhiet et al. (2007), who observed no effect of Cr supplementation as CrCl3 on blood AST and uric acid in broilers.
In birds, improvement in gut mucosal morphology is characterized as a health indicator and growth indicator (Awad et al., 2009

V. CONCLUSION
Supplemental Chromium propionate CrProp significantly affects the serum metabolites such as ALT and AST and improves intestinal morphological qualities at 0.8mg/kg supplementation of CrProp of feed.

This work was approved by the Research and Ethics
Committee of the Animal Production and Health Department, The Federal University of Technology, Akure, Nigeria.

COMPETING INTERESTS
Authors have declared that no competing interests exist.

AUTHORS' CONTRIBUTIONS
This work was carried out in collaboration among all authors. Authors OSO, OAA and CAC designed the study. Authors OAA and FBA performed the statistical analysis. Authors OSO, OAA and FBA wrote the protocol. Authors OSO, FBA and OTA wrote the first draft of the manuscript. All authors managed the analyses of the study. Authors OSO, OAA and FBA organised the literature searches. All authors read and approved the final manuscript