Pasty Vents in Broiler Chickens

Luis Fernando Vergamini Luna thanks for your comment. Because the pasty vent will improve the overall feed conversion, as average 6 points, or 0.06, the energy conversion will also be improved in similar proportion. Now the feed conversion due to pasty vent is dependent on the level of fat, meaning more fat in the diet the less effect on feed conversion due to emulsifier. In contrast, the less dietary fat the better feed efficiency due to emulsifier.
Hope this helps.
Regards.

Reza Mahdavi Thanks for your comments and let me clarify this more. As you mention, while adding more fat the emulsifier will have more effect on feed conversion, this is the first thinking as we all know the emulsifier helps to improve the fat digestibility. Making a meta-analysis with 21 publications and correlate improvement of FCR due to emulsifier, as compared to control diets, (Y axis, points, difference of FCR x 100) and dietary fat (X axis, %) shows a significant linear relationship: Y = 1.85 X -18.9. This means that as the dietary fat increases the improvement of FCR due to emulsifier is reduced. Why? Other papers shows that by adding more dietary fat, the fat digestibility is increased, so there is less for the positive effect from emulsifier. To avoid confusion about this data, this is the difference of feed conversions between the FCR from emulsifier and FCR from control diets. So if we are speaking about FCR of absolute terms, using two levels of dietary fat will clarify this more:
Dietary of total fat, % FCR from control FCR from emulsifier Difference of FCR x 100
4.5 1.70 1.59 -11
7.0 1.55 1.49 -6
This means, in terms of absolute terms as increase the dietary fat, the FCR from is reduced with the best feed efficiency from the emulsifier, however, as expressed in difference of FCR, compared to the control diets, as increase the dietary fat the difference of improvement FCR from emulsifiers are reduced from -11 to -6 points.
Hope this helps to clarify the concept.
Best regards.