Good meat quality attracts favorable attention from consumers as compared to meat with excess fat and excess fat deposition is a major factor of poor meat quality of broilers. Excess fat can result in reduction of carcass yield and difficulties in processing. White meat such as chicken meat  is  considered  superior  for  health reasons to red meat because of comparably low contents of fat, cholesterol and iron. Manipulation of trait depends on the combined genetic and nutrition. Some of the selection strategies results in accumulation of excessive fat in the body that negatively affects production efficiency, consumer  perception  and marketability of chickens (Zhou et al., 2006). The success in poultry meat production has been strongly related to improvements in body growth and carcass yield, mainly by increasing breast proportion and reduction in abdominal fat. Al-Daraji et al. (2011) demonstrated that increasing L-arginine supplementation level in broilers diet reduced total body fat deposition (Hyun-Seek et al., 2017). L-Arginine, an amino-acid reported to be the sole precursor of nitric oxide, with lots of immune functions (Kang et al., 2014) and growth performance. Nitric oxide (NO) plays an important role in modulating both the hepatic and renal circulation under physiological and pathological conditions. Addition of L-arginine in poultry diets is required to avoid the harmful influences of excessive free radicals produced during normal metabolism (Atakisi et al., 2009). Methionine and arginine are two amino acids that have proven immune regulatory action (Tayade et al., 2006). Arginine is involved in a number of other metabolic functions in the body, such as its potential to be converted to glucose (hence, its classification as a glycogenic acid), and its ability to be catabolized to produce energy (Tan et al., 2014; Tong and Barbul, 2004). It is also a vasodilator (Melik et al., 2016). Dietary L-arginine supplementation plays key role in enhancing meat quality. It was recently demonstrated that L-arginine increases specific immune response against infectious bursal disease (IBD) in chickens (Jeffery et al., 2014). In the liver, nitric oxide synthase (NOS) may be expressed by hepatocytes, cholangiocytes, hepatic stellate cells, and Kupffer cells (Trauner and Boyer, 2003). NO is able to exert dichotomous effects under physiological and pathological conditions. The induction of NOS in phagocytic cells by a variety of noxious stimuli may lead to high and  sustained  levels  of  NO,  which  may  cause cytotoxicity through nitrosative stress (Pacher et al., 2007). The aim of this study is to determine the effect of L-arginine on the kidney and liver of Sasso chickens.

This experiment was carried out at the Poultry Unit of Landmark University Teaching and Research Farms, Omu-Aran, Kwara State, Nigeria. A total of 297 mixed sex Sasso chickens were used for the study. The chickens were randomly distributed into three treatments containing three replicates of thirty-three birds each in a completely randomized design (CRD). The birds were fed with grower’s mash and given different treatment of 0 mg/L (Treatment A at 0% supplementation), 167 mg/L (Treatment B at 50% supplementation) and 334 mg/L (Treatment C at 100% supplementation) of L-arginine supplement in drinking water of 9 L per replicate daily for a period of five consecutive weeks; after 5 weeks, three birds from each treatment was decapitated at the Landmark University Teaching and Research Farms, the organs were removed and put in 10% phosphate buffered formaldehyde buffer solution in well labeled containers. The organs (kidney and liver) were taken to Federal Medical Center, Lokoja Histopathology Laboratory for analysis. For histopathological analysis, the tissue samples (the kidney and liver), were fixed in neutral phosphate buffered 10%-formalin solution, embedded in paraffin and 4 mm thick sections were prepared. After deparaffinization, the sections were stained with haematoxylin and eosin (HE). The slices were examined under the light microscope and images were captured with digital camera at the magnification of 100.

After carrying out the histological analysis on the kidney, there was no notable change in the heart of Sasso chickens administered treatment A, no dose of L-arginine (Plate 1).

Findings showed that the microscopic structure of the kidney of Sasso chickens given 0 mg/L has typical structure with no lesion as reported by Wideman (2001). Although, it was reported that increasing L-arginine level in broilers diet reduced total body fat deposit (Hyun-Seek et al., 2017), However, the  kidney structure of chickens given 167 mg/L of L-arginine showed congestion of vascular channels, destruction of the glomeruli and tubules  in   line   with   Pacher  et  al., (2007).  L-arginine caused desquamation of the epithelial cells lining the tubules with lymphoid follicle formation in the interstitium, which is the shedding off of the outermost layer of the tissue in all replicates given 334 mg/L, in line with Johnson (1979). Plate 4 shows a typical structure with no lesion as reported by Trauner (2003). The liver in Plate 5 shows the liver under 167 mg/L intake had congested vascular spaces. The liver in Plate 6 shows that the liver under  334 mg/L  intake  had  congested vascular spaces and periportal mononuclear inflammatory infiltration as reported by Pacher et al., (2007). The degenerations observed in the kidneys and livers of the birds indicate that 167 and 334 mg/L L-arginine supplementation induced adverse effects on the organs as reported by Ichihara et al., (1999). NO is a powerful vasodilator and it blunts the expression of the tubuloglomerular feedback and acts as a vasoconstrictor; these result is expected (Dai et al., 2013). The result from this experiment shows that oral supplementation of high dosage of L-arginine had a negative effect on the structure of the kidney and liver of  the  Sasso  birds  given  50  and 100% L-arginine supplementation. Not ignoring its benefits, L-arginine could still produce its positive effects if used at a lower dosage of less than 50% supplementation level.

One of the benefits of L-arginine is that it increases renal plasma flow (RPF) and glomerular filtration rate (GFR). However, from this study, high dosage of oral supplement can lead to the over-expression of nitric oxide in the organs  causing  a  negative  effect  on   the   microscopic structure of the kidney and liver of the Sasso chickens. Based on the finding from this experiment, further research should be done with lesser dosage less than 50% supplementation level of L-arginine supplement on the Sasso chicken to maximize the benefits such as reduction of total body fat deposit without any negative form of alteration in the structure of the organs.

African Chicken Genetic Gains is appreciated for the provision of the birds for this experiment.

The author has not declared any conflict of interests.