Using pellet quality to improve broiler growth rate, feed conversion

The way feed is presented will affect energy and time required to consume it.

Poultry activity, or behavior, has not received as much research attention as other areas when considering performance. In our modern production environments, there has traditionally been little perceived economic value in understanding or monitoring bird behavior.

Most of the focus in broiler production has been on genetic progress, strain selection, feeding programs and management systems rather than on how the bird responds to such changes. However, bird activity is responsible for the major energy loss between consumed dietary metabolizable energy and the amount of energy retained as tissue, and so it merits consideration.

Activity and energy consumption  

Depending on the management system in place, 20 percent of metabolizable energy intake is used for activity. In other words, assuming that 14,287 Kcal metabolizable energy must be consumed to produce a 2.5 kg broiler, approximately 2,858 Kcal metabolizable energy are used for activity. Therefore, reducing activity energy expenditure by around 6 percent would save a considerable amount of energy.

Pelleting poultry feeds has been long recognized as a method to enhance bird performance. Pelleting is known to increase body weight, to reduce feed wastage and to improve feed conversion.

Its exact mode of action, however, has been speculative. Work reported by Jensen et al. (1962), indicated that pelleting did indeed elevate bird performance through increased body-weight gain and improved feed conversion. Additionally, Jensen noted that broilers fed pellets spent less time eating and more time resting than those fed mash.

Furthermore, the same study reported that digestibility was not a factor in the improved broiler performance. Consequently, bird behavior may well be a critical factor for defining the mode of action for pelleting. If true, then pelleting would also offer an avenue to manipulate bird energy expenditure for activity.

Observing behavior  

The importance of bird behavior and feed form were examined by Dr. Robert Teeter at Oklahoma State University in the following two experiments. Behavioral observations were conducted by walking past each cage five times spaced throughout the day and classifying the broilers into one of nine behavior categories.

These included eating, drinking, standing, resting, pecking, preening, walking, dust bathing, and other activity. The five observations for each bird were then put on a percent-time basis to create results for data analysis.

As described by McKinney and Teeter in 2004, bird body weight and feed conversion values were transformed into effective caloric value. The effective caloric value represents the caloric density that would be needed to achieve the same body weight and feed conversion result under low stress conditions. As such, effective caloric value enables evaluation of calorie savings when viewed as the difference between values created by varying nutritional and/or non-nutritional production scenarios.

In the first study, birds were offered two feed forms—mash vs. pellets—with treatments also including birds switched from one feed form to the other. All birds were offered the same ration composition, independent of feed form, and allowed to consume feed ad libitum.

Despite the fact that all birds were provided a 3,050 Kcal metabolizable energy/kg ration, the range of an effective caloric value for individual birds was from 2,450 when a bird spent 20 percent of its time resting to 3,550 when a bird spent 85 percent of its time resting, creating a spread of 1,100 Kcal of effective caloric value/kg ration.

Most of the variability for the performance deviation was explained by the activity variables displayed in Figure 1 (R2>.95). Results of the first study reported are also in general agreement with that of Jensen et al. (1962).

Encouraging quick consumption  

The importance of bird activity as a source of energy wastage is clear. Yet another factor impacting bird behavior appears to be feed form variety. Although mash and pelleting impacted effective caloric value, the greatest effect of feed form was in birds experiencing a feed form change.

Birds being switched from mash to pellet, or vice versa, exhibited the most voracious eating. Indeed, birds that were switched to a different feed form, independent of form, spent half the time eating more feed than those not having their feed switched.

Consequently, variety may also be an important aspect of behavior influencing efficiency in the production environment, as the highest effective caloric value energy value come from birds eating quickly and then resting.

In the second study, the influence of feed form on bird behavior and effective caloric value was again examined so that responses to varying pellet quality might be better defined.

Six feed form treatments were used: heat-processed mash served as a negative control; 20 percent pellets: 80 percent pellet fines; 40 percent pellets: 60 percent pellet fines; 60 percent pellets: 40 percent pellet fines; 80 percent pellets: 20 percent pellet fines; and 100 percent pellets.

The daily body weight and feed conversion data were transformed into dietary caloric density as effective caloric value and then examined as deviations from the mash diet to produce an estimate of the Kcal/kg efficiency added by pellet quality.

As expected, pelleting of the feed improved body weight, feed conversion and effective caloric value. When the effective caloric value is examined, relative to the mash ration, it progressively increased to +187 Kcal/kg of diet for the highest pellet quality (Figure 2). Note also that effective caloric value and bird behavior were highly correlated.

When viewed together, resting and effective caloric value form nearly parallel lines, both increasing as pellet quality improves. Any combination of management factors that decreases time spent eating and increases time spent resting appears to offer potential to increase the effective caloric value of the diet fed.

In an effort to make data from the second study field applicable, effective caloric value differences are expressed as that achieved by making a switch to higher (caloric density gain) or lower (caloric density loss) pellet quality (Table 1).

What change in pellet quality would be needed to compensate for a 55 Kcal metabolizable energy/kg ration reduction? Increasing pellet quality from 30 to 70 percent will exactly counter the effect of reducing the feed energy by 55 Kcal metabolizable energy/kg.

Considering the above example, to have equivalent bird performance, expressed as equivalent body weight and feed conversion for the flock, the producer would need to add the equivalent of 55 Kcal metabolizable energy/kg ration; this will achieve another 225 Kcal metabolizable energy intake.

This may be achieved via improving pellet quality as long as the initial pellet quality is equal to or less than 70 percent. Since the pellet quality response curve is not linear, it is necessary to examine the relationships at specific points in Table 1.

Observable benefits  

Results indicated that broilers typically spend their time in the following order (from greatest to least): resting, eating, standing, drinking, preening, walking, dust bathing, pecking, and other activity. It was common for the combination of eating and resting to account for 60-85 percent of broiler activity.

Broilers respond to pelleted feed by spending less time to eat the same or more feed. This decreased time spent eating is then spent resting, which decreases animal energy expenditure leaving more energy available for gain.

Changing the feed form presented to the broiler results in more voracious eating and may offer additional advantage. Depending on the current producer pellet quality, it appears possible to compensate for a reduction in feed energy by improving pellet quality.