MATERIALS AND METHODS

Experimental birds, housing and management: The chicks (240 male broilers) were randomly divided into 24 replicate lpens for 6 treatments in a 2×3 factorial arrangement under Completely Randomized Design (CRD) using 4 replicates per treatment group and 10 chicks were allotted to each replicate.

Table 1:	Composition of experimental starter diets
F1, F2 and F3 indicate added fat at the rate of 1, 2 and 3% in diets, respectively, E0 and E1 represent no emulsifier and 350 mg kg–1 fat emulsifier in the broiler diets, respectively

Table 2:	Composition of experimental finisher diets
F1, F2 and F3 indicate added fat at the rate of 1, 2 and 3% in diets, respectively, DCP: Dicalcium phosphate, CF: Crude fat or fiber, E0 and E1 represent no emulsifier and 350 mg kg–1 fat emulsifier in the broiler diets, respectively

Light, ventilation, relative humidity and floor space were maintained as standard. Temperature was kept at 95°F during first week and then it was decreased as 5°F per week until it was maintained at 75°F throughout the trial. This investigation approved by Department of Animal Sciences, College of Agriculture, University of Sargodha, Pakistan Ethical Committee.

Experimental design and diets: For the trial 6 iso-caloric and iso-nitrogenous broiler starter and broiler finisher diets were formulated having three fat levels 1, 2 and 3% with or without fat emulsifier at a constant level of 350 g t^–1. The trial lasted for 35 days and was divided into 2 phases i.e., starter and finisher phases. Description of the experimental diets is given in Table 1. The ingredients employed in feed formulation and chemical compositions of each experimental starter and finisher diet is given in Table 1 and 2, respectively. Proximate analysis of feeds is given in Table 3. All birds and chemicals were collected from Ghazi Brothers Ltd., Pakistan as gift sample.

Vaccination: All the chicks were vaccinated against new castle disease (ND) and Infectious Bursal Disease (IBD) in this trial.

Production performance and livability: Parameters regarding body weight, Feed consumption, feed conversion ratio, mortality, all are recorded during whole experiment and also conducted digestibility trial ash as an external marker for evaluation of dry matter and ether extract digestibility described by Olukosi et al. (2012):

Statistical data analysis: Data collected during the trial regarding initial weight, final weight, feed intake, weight gain, FCR, nutrient digestibility including dry matter and ether extract digestibility, carcass yield, breast meat yield, thigh meat yield, dressing percentage and relative organ weights of liver, heart, spleen, gizzard and abdominal fat was analyzed in 3×2 factorial arrangement under CRD and means were separated by Duncan’s Multiple Range Test (Steel et al., 1997).

RESULTS AND DISCUSSION

Feed intake: There was no interaction (p>0.05) between fat and fat emulsifier for starter, finisher and overall feed intake (Table 4). There was no individual effect (p>0.05) of fat emulsifier on starter, finisher and overall feed intake (Table 4). Increasing level of dietary fat supplementation did not affect (p<0.05) starter, finisher and overall feed (Table 4) Findings of present study are supported by Kussaibati et al. (1982) who reported no effect of dietary fat and exogenous fat emulsifier on feed intake during all phases of broiler life. The results might be attributed the improved nutrient digestibility with fat emulsifier supplementation which might resulted in fulfilment of the caloric requirements of the birds and hence the birds did not intake more feed (Mathlouthi et al., 2002). Results of present study are contradictory to the findings of Melegy et al. (2010), Udomprasert and Rukkwamsuk (2006) and Tang et al. (2007) who reported that inclusion of various fat blends with supplementation of lysolecithin (a fat emulsifier) resulted in a significant increase in feed intake in broiler.

Table 3:	Proximate analysis of experimental diets
F1, F2 and F3 stand for added fat at the rate 1, 2 and 3% in the diets, respectively

Table 4:	Effect of fat and fat emulsifier on feed utilization in broiler
F1, F2 and F3 indicate added fat at the rate of 1, 2 and 3% in diets, respectively, E0 and E1 indicate added fat emulsifier at the rate of 0 and 350 mg kg–1 in diets, respectively, NS: Non-significant (p>0.05), *Significant (p<0.05), SEM: Standard error mean

These results might be attributed to the type of fat emulsifier used in previous studies because lysolecithin, choline and cholic acid have been reported to be more efficient fat emulsifiers as compared to bile acid which was used in present study. The results of present study are in agreement with the findings of Crespo and Esteve-Garcia (2001), Fernandez and Fraga (1996), Shahryar et al. (2011) and Nobakht et al. (2012) who found that increasing fat levels had no effect on feed intake. Some other researchers (Suksombat et al., 2007; Rahimi et al., 2011) also reported no effect of vegetable fat (oil) supplementation on average daily feed intake. It might be attributed to the lower levels of fat used in diets resulting in no effect on dustiness, palatability and intake of feed (Saleh et al., 2009). The results of present study are contradictory to the findings of Leeson (1993), Ghazalah et al. (2008), Rezaei et al. (2007) and Velasco et al. (2010) who reported that higher levels of dietary fat (up to 5%) resulted in increased feed intake in broiler. Several others have also reported that inclusion of vegetable oils in high energy diets resulted in improved feed intake (Monfaredi et al., 2011). The increase in feed intake might be due to higher level of dietary fat causing decreased dustiness and improved palatability (Rezaei et al., 2007).

Feed conversion ratio: Starter and overall FCRs were found unaltered (p>0.05) however, finisher FCR was significantly affected (p<0.05) with combination of fat and fat emulsifier in diets (Table 4). Fat emulsifier did not affect (p>0.05) starter and overall FCR but finisher FCR was affected (p<0.05). Increasing dietary fat levels had no significant effect (p>0.05) on finisher and overall FCR however, starter FCR increased with increasing fat levels (p<0.05).Results of present study are agreed with the findings of Guerreiro Neto et al. (2011) who reported that there was no effect of fat and fat emulsifier interaction on overall FCR in broiler however, starter FCR was affected. Increasing FCR with increasing fat level in starter might be attributed to no lipase activity in starter phase resulting in lower absorption of fats and as a result lower energy absorption from iso-caloric (Wongsuthavas et al., 2007). Results of present study are contradictory to the findings of Zollitsch et al. (1997) who reported that there was a significant effect of fat and fat emulsifier on FCR in broilers fed diets containing a blend of different fats supplemented with choline. The difference in results might be attributed to higher emulsifying activity of choline as compared to bile acid which was used in present study.

The result of present study are in agreement with the findings of Wongsuthavas et al. (2007) and Nobakht et al. (2012) who reported that there was no effect of various fat levels on overall FCR in broiler while, starter FCR was significantly increased with increasing fat levels. The results might be attributed to lipase activity which is not found in starter phase resulting in no absorption of fats and there is more loss of energy with increasing fat level in iso-caloric diets (Gaiotto et al., 2001; Wongsuthavas et al., 2007). Results of present study are contradictory to the findings of several researchers (Crespo and Esteve-Garcia, 2001; Baiao and Lara, 2005; Fernandez and Fraga, 1996; Suksombat et al., 2007; Ghazalah et al., 2008; Velasco et al., 2010; Mansoub, 2011) who reported that increasing fat levels in poultry diets improved FCR throughout the broiler life span. The difference in results might be attributed to the reduced dustiness with utilization of higher fat levels in diets which might resulted in improved nutrient utilization and as a result improved FCR (Rezaei et al., 2007).

Nutrient digestibility: There was an interaction (p<0.05) between fat and fat emulsifier for dry matter and ether extract digestibility (Table 5). Dry matter and ether extract digestibility was affected (p<0.05) by fat emulsifier supplementation in broiler diets. Increasing dietary fat levels did not affect (p>0.05) dry matter and ether extract digestibility (Table 5).

Table 5:	Effect of fat on feed utilization in broiler
F1, F2 and F3 indicate added fat at the rate of 1, 2 and 3% in diets, respectively, NS: Non-significant (p>0.05), *Significant effect (p<0.05)

Table 6:	Effect of fat and fat emulsifier on growth performance of broiler
F1, F2 and F3 indicate added fat at the rate of 1, 2 and 3% in diets, respectively, E0 and E1 indicate added fat emulsifier at the rate of 0 and 350 mg kg–1 in diets, respectively, NS: Non-significant (p>0.05), *Significant effect (p<0.05)

Table 7:	Effect of fat on growth performance of broilers
F1, F2 and F3 indicate added fat at the rate of 1, 2 and 3% in diets, respectively, NS: Non-significant effect (p>0.05), *Significant effect (p<0.05)

Findings of present study are supported by the results obtained by Adrizal et al. (2002), Maisonnier et al. (2003), Parsaie et al. (2007), Firman et al. (2008), Kil et al. (2010) and Cho et al. (2012) who reported that there was a significant increase in DM and EE digestibility in broiler fed iso-caloric diets containing fat emulsifier and dietary fats at low level. The results might be attributed to the action of fat emulsifier as an emulsifying agent for dietary fat and a stabilizer for other feed ingredients along with higher degree of lipolysis of triglycerides resulting in more micelle formation, digestion and absorption of fats (Cho et al., 2012). Results of present study are not in line with the findings of several researchers (Danicke et al., 2000; Sanz et al., 2000; Hertrampf, 2001; Andreotti et al., 2004; Ferreira et al., 2005; Guerreiro Neto et al., 2011) who reported that that there was no effect of low level of fat emulsifier supplementation in iso-caloric diets containing higher fat levels (5-6%) from various sources. The differences in the results might be attributed to improper concentration of fat emulsifier supplemented in the diets containing higher levels of fat. This might resulted in decreased uptake and utilization of feed ingredients including dietary fat and other feed ingredients (De Los Santos et al., 2008).

Weight gain: No interaction was found between fat and fat emulsifier for starter, final and overall weight gain (p>0.05) however, finisher weight gain was improved (p<0.05) (Table 6). Dietary fat did not affect starter, finisher, final and overall weight gain (Table 7). Increasing level of dietary fat in starter feed resulted in a linear decrease in weight gain (p<0.05) while, there was no effect (p>0.05) on finisher, final and overall weight gain. Results of this study are in line with the findings of Roy et al. (2010), Guerreiro Neto et al. (2011) and Luc et al. (2013) who reported that addition of fat emulsifier in vegetable oil based broiler diets resulted in an improved weight gain during finisher phase however, no effect was found on starter weight gain. These results might be attributed to no activity of lipase in starter phase while increased weight gain in finisher phase might be attributed to increased lipase activity resulting in higher fat digestibility along with emulsification (Gaiotto et al., 2001; Wongsuthavas et al., 2007; Guerreiro Neto et al., 2011).

Andreotti et al. (2004) and Ferreira et al. (2005) who reported that there was no interaction between fat emulsifier and higher levels of dietary fat in broiler diets with regard to weight gain. The results might be attributed to use of higher concentration of dietary fats with an improper concentration of fat emulsifier (Andreotti et al., 2004).

The result of present study are in agreement with the findings of several researchers (Sanz et al., 2000; Crespo and Esteve-Garcia, 2001; Suksombat et al., 2007; Wongsuthavas et al., 2007; Ghazalah et al., 2008; Tabeidian et al., 2010; Velasco et al., 2010; Nobakht, 2011) who reported that there was no effect of graded fat levels on weight gain in broiler.

Table 8:	Effect of fat and fat emulsifier on organ weight of broiler
F1, F2 and F3 indicate added fat at the rate of 1, 2 and 3% in diets, respectively, E0 and E1 indicate added fat emulsifier at the rate of 0 and 350 mg kg–1 in diets, respectively, NS: Non-significant (p>0.05), *Significant (p<0.05)

Gaiotto et al. (2001) and Guerreiro Neto et al. (2011) reported that fat supplementation in broiler resulted in a linear decrease in weight gain during starter phase. The decrease in weight gain during starter phase might be attributed to no or limited lipase activity which might result in poor fat utilization (Gaiotto et al., 2001; Wongsuthavas et al., 2007). The results of present study are contradictory to the findings of a number of researchers (Adrizal et al., 2002; Baiao and Lara, 2005; Rezaei et al., 2007; Monfaredi et al., 2011; Shahryar et al., 2011) who reported that weight gain in broiler was affected by varying levels and higher proportion of dietary fat as compared to other feed ingredients. The difference in the results might be attributed to the decreased dustiness with usage of higher fat levels resulting in more palatability, increased feed intake and higher weight gain as a result (Rezaei et al., 2007).

Carcass characteristics: Fat emulsifier supplementation did not affect (p>0.05) liver, spleen and gizzard weight however, heart weight was affected (p<0.05) and gizzard weight decreased (p<0.05) linearly with increasing fat level (Table 8). The result of present study are in agreement with the findings of Crespo and Esteve-Garcia (2001), Ghazalah et al. (2008) and Nobakht et al. (2012) reported that dietary vegetable fat supplementation in broiler had no effect on the dressing percentage of broiler. Several other researchers (Peebles et al., 1997; Lara et al., 2006; Suksombat et al., 2007; Roy et al., 2010; Guerreiro Neto et al., 2011; Shahryar et al., 2011) also found that there was no effect of dietary oils on dressing percentage and carcass characteristics including abdominal fat, live weight, liver weight, dressing percentage, thigh weight, breast weight, heart weight, spleen weight and gizzard weight. The results might be attributed to the source of fat utilized in all the studies because vegetable fats might not affect carcass characteristics of broiler (Lara et al., 2006). The results of present study are contradictory to the findings of several researchers (An et al., 1997; Tabeidian et al., 2010; Velasco et al., 2010; Nobakht et al., 2012; Kabir and Ide, 1995) reported that supplementation of fat in poultry had a significant effect on dressing percentage, liver, gizzard and breast and thigh weights. The higher carcass and organ weights obtained in birds consuming dietary fat might be as a result of fat which might gave higher metabolizable energy values as compared to other energy sources (Saleh et al., 2009). Results of present study are not in line with the findings reported that inclusion of fat in broiler diets reduced the relative weight of liver which might be attributed to the presence of inositol which is involved in the movement of fats from liver to other body parts in broilers (Schaible, 2000). The differences in results might be attributed to increased utilization of fat as a source of energy in broilers when the diets contained fat (Nobakht, 2011).

Present study is in line with the findings of Andreotti et al. (2004), Ferreira et al. (2005), Lara et al. (2006), Roy et al. (2010), Guerreiro Neto et al. (2011), Cho et al. (2012) and Luc et al. (2013) who reported that there was no effect of fat emulsifier supplementation on the internal organ weights of broiler. The results might be attributed to increased utilization of fat as a source of energy when the diets contain fat and fat emulsifier (Nobakht, 2011). Results of present study are not in line with the findings of Praharaj et al. (1997) reported that relative weights of liver, heart, spleen and gizzard were affected significantly in broiler by supplementation of fat emulsifier in the diets. The difference in results might be attributed to the presence of lecithin in commercial emulsifier preparations which might enhance the activity of emulsification (Schaible, 2000).

CONCLUSION

This investigation reveals that dietary fat should be avoided in starter diets and supplementation of fat emulsifier in broiler diets may improve DM and EE digestibility. It can also be concluded that supplementation of fat emulsifier in broiler rations may improve dry matter and ether extract digestibility. Further investigation entails to identification of mechanisms of action as well as other effective or toxic effect on animal.

ACKNOWLEDGMENTS

Authors acknowledge to Dr. Muhammad Arif and Mr. Abdur Rehman, Department of Animal Sciences, College of Agriculture, University of Sargodha, Pakistan as well as Graduate School of Chinese, Academy of Agricultural Sciences, Beijing (100081), China, College of Animal Sciences, Northwest A and F University, Yangling, 712100, China, Progati Medical Institute, Department of Pharmacy, Dhaka-1216. Bangladesh for their collaborated support.