The present study was undertaken at the Instructional Poultry Farm (IPF), of Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, U.S. Nagar. The place is located between 28° 53ʹ 23ʺ to 30° 27ʹ 50ʺ N and 77° 34ʹ 27ʺ to 81° 02ʹ 22ʺ E at 243.84 m MSL (mean sea level) in the Tarai region of Uttarakhand State (India). The climate is humid subtropical. Winters are very severe and summers are hot and humid. Temperatures may rise to a maximum of 43°C in the summer and fall to a minimum of 2°C in the winter. Relative humidity ranges from 15 to 95% (Singh et al., 2015). The study was conducted on 252 day-olds straight run Ven Cobb⁴⁰⁰ broiler chicks for 6 weeks under standard management conditions. Feed and water were provided ad libitum. The present study evaluated the effect of dietary inclusion of various feed supplements and their combination on the performance index, glucose and serum cholesterol for 6 weeks. Day- old broiler chicks (n=252) were randomly assigned to seven treatment groups, each with 3 replicates. The first treatment was designated as control (T₀) in which no supplement was added to the feed, while in treatments T₁; organic mineral mixture (Organomin forte), T₂; organic mineral mixture (Vannamin), T₃; probiotics (Microguard), T₄; enzyme (Brozyme -XPR) and probiotics, T₅; emulsifier (Lipigon) were provided through feed. In the T₆ group, 3 percent less energy was given through feed and at the end of the feeding trial on 42nd day, two birds from each replicate were randomly selected and their organ weights were taken.

After evisceration, the intestine of the birds were carefully separated and the length of the duodenum (from the ventriculus to the pancreo-biliary duct), jejunum (from the pancreo-biliary duct to Meckel’s diverticulum), and ileum (from Meckel’s diverticulum to the ileocecal junction) were measured using a measuring tape, villus height was measured from the tip of the villus to the bottom of the villus, crypt depth was measured from the villus bottom to the crypt base and villus height and crypt depth ratio was also calculated.

The data were analysed statistically by using SPSS (Armonk, New York, US) and significant mean differences between the treatments were determined at P<0.05 using Duncan’s Multiple Range Test as modified by Kramer (1957). A p-value of <0.05 was considered as statistically significant.

The effect of different supplements on organ weights of the broilers has been shown in Table 1. Liver weight was significantly increased in the broilers of feed supplemented groups in comparison to control. Gizzard and heart weights were significantly increased in the broilers of feed supplemented groups in comparison to control except T₆. Pancreas weight was significantly increased in the broilers of feed supplemented groups in comparison to control except T₂ and T₆. Spleen weight was significantly increased in the broilers of feed supplemented groups in comparison to control except T₁ and T₂.

The results of the present study are in agreement with Aguihe et al. (2017) and Kaushal et al. (2018) who found significantly (P<0.05) higher liver and gizzard weights of broilers fed the diet supplemented with enzymes with probiotics. Awad et al. (2009) and Mahmud et al. (2014) noted a significant (P<0.05) increase in weights of liver, spleen, gizzard, and heart in broilers fed the diet supplemented with probiotics. Swain et al. (2012) observed that weights of liver, heart, spleen were higher in broilers supplemented with probiotics and yeast. Aguilar et al. (2013) found an increase in liver weight of broilers fed the diet supplemented with an exogenous emulsifier. Sagar et al. (2018) reported a significant (P<0.05) increase in spleen weight of broilers supplemented with zinc. Sharma et al. (2018) found a significant (P<0.05) increase in liver, spleen, gizzard, heart and pancreas weights of broilers fed the diet supplemented with enzymes.

Means bearing different superscripts in a column differ significantly (P < 0.05).

Means bearing different superscripts in a column differ significantly (P < 0.05).

In contrast, Shareef and Al-Dabbagh (2009) and Yadav et al. (2018) reported non-significant (P>0.05) differences in liver, gizzard, heart, spleen and pancreas weights of broilers fed the diet supplemented with probiotics viz., Saccharomyces cerevisiae and Bacillus subtilis respectively. Zakaria et al. (2010) found nonsignificant (P>0.05) differences in liver and gizzard weight of broilers fed diet supplemented with enzymes. Narasimha (2013) observed non-significant (P>0.05) differences in liver, gizzard, pancreas, spleen and heart weights of broilers fed the diet supplemented with enzymes and probiotics.

The weight of vital organs viz. heart, pancreas, liver, gizzard, and spleen were significantly (P<0.05) increased by the feed supplements of which were in the normal range. The effect of higher inclusion levels of feed supplements and their combination of vital organs increase was more pronounced as compared to lower levels in general.

The effect of different feed supplements on the intestinal morphology of the broilers has been shown in Table 2.

Duodenum, ileum and small intestinal length were significantly increased in the broilers of feed supplemented groups in comparison to control except T₆. Jejunum length was significantly (P<0.05) increased in broilers of feed supplemented groups in comparison to control except T₁ and T₆. The results are in agreement with the finding of Wang et al. (2016) found a significant (P<0.05) increase in duodenal, jejunal and ileal length of broilers fed the diet supplemented with probiotics. In contrast, Kaushal et al. (2018) found non-significant (P>0.05) difference in intestinal length of broilers fed the diet supplemented with multi- enzymes.

Duodenum villous height was significantly increased in the broilers of feed supplemented groups in comparison to control except T₆. Duodenum crypt depth was significantly decreased in broilers of feed supplemented groups in comparison to control except T₃, T₄, and T₅. Villous height: crypt depth ratio was significantly increased in the broilers of feed supplemented groups in comparison to control. Gao et al. (2008) noted a significant (P<0.05) increase in villi height in the duodenum of broilers fed the diet supplemented with probiotics (Saccharomyces cerevisiae). Luo et al. (2009) found a significant (P<0.05) increase in villus height: crypt depth ratio in broilers fed the diet supplemented with the enzyme (xylanase). Yang et al. (2008) observed a significantly (P<0.05) decrease in crypts depth of broilers fed the diet supplemented with the enzyme (xylanase). Zhang et al. (2005) found a significant (P<0.05) increase in villus height: crypt depth ratio in broilers supplemented with yeast. Awad et al. (2009) found a significant (P<0.05) decrease in crypt depth and increase in villus height: crypt depth ratio of broilers fed the diet supplemented with probiotics (Lactobacillus species). Echeverry et al. (2016) found significantly (P<0.05) lower crypt depth and higher villi height: crypt depth ratio in broilers fed the diet supplemented with organic trace minerals. Abdel-Latif et al. (2018) found a significant (P<0.05) increase in the villi height and villus height: crypt depth ratio in broilers while crypt depth was significantly (P<0.05) decreased in broilers fed the diet supplemented with probiotics. Kaushal et al. (2018) found a significant (P<0.05) increase in duodenum villus height and villous height: crypt depth ratio and decrease in duodenum crypt depth of broilers fed the diet supplemented with enzymes and probiotics. Pelicano et al. (2005) noted a significant (P<0.05) increase in villus height in the duodenum, jejunum, and ileum of broilers fed the diet supplemented with probiotics and prebiotics.

Thus it may be inferred that supplements had altered the gut morphology by stimulating rapid cell division and elongation and more intercellular space leading to increased surface area for absorption of nutrients.