Table 3.9 Coefficients obtainedfrom fitting curvilinear regressions ofbody weight gain and feed conversion efficiency (FCE) on dietary protein intake, with feed form and trough location as groups
Body weight gain FCE
Source Coefficient P value Coefficient P value
Constanta -1.12 0.419 202.0 0.001
Protein intake 5.537 0.001 2.508 0.001
Protein intake/ -0.474 0.004
Feedform 1.366 0.001 89.8 0.001
Constantb -1.5 0.427 242.5 0.001
Protein intake 6.37 0.001 2.508 0.001
Protein intake2 -0.613 0.005
Feed trough location -0.154 0.615 8.4 0.673 Constanta
=
feed form. Constantb=
feed trough locationgains when young broiler chickens were fed mash rather than pelleted feed.Furthermore, because body weight gain is highly dependent on nutrient intake, the improved performance obtained by feeding pellets has been attributed to hyperphagia (Bolton, 1960).
The improved growth of broiler chickens fed pellets may have occurred due to reduced maintenance requirement, as had been stated in previous studies (Penz, 2002).
Furthermore, it was noted in this trial that chicks fed pellets spent less time feeding, thus reducing the energy spent on consumption, which could have led to more energy being available for growth. Moreover, pelleting may increase intake of nutrients by bringing nutrients together, thus improving nutrient utilization in the feed. The results of feeding young broilers pellets.is in contrast to the earlier findings by Calet (1965) who observed no improvement in growth due to pelleting feeds for young broiler chicks, but is in line with the findings of Hinds and Scott (1958) and Penz (2002) who claimed that the effect of pellets is more marked when the broiler chickens are very young.
Location of feed troughs inside the cages proved to be beneficial to growth of the broiler chickens, as shown by the significant improvement in weight gain with both feed forms.
This improvement in weight gain may be attributed to improved food accessibility. This justifies the suggestion that the problem of inadequate food intake on growth of broiler chickens at Ukulinga may be improved by using feed troughs situated inside the cages (Gous, 2002-personal communication). This applies specifically to the brooder cages at Ukulinga, but it does highlight the importance of accessibility to food when feeding chicks.
The significant difference in food intake between mash and pellets, with high intake observed when broilers were fed mash may be attributed to the difference in maintenance requirement by the chickens to the two feed forms, with high maintenance requirement occurring when chickens were fed mash feed. This is contrary conclusion to that of Leroy (1961),that when the feed is supplied in mash form, the heat loss measured by respiratory exchange is considerably reduced thus reducing energy requirements.
The lowest food intake that occurred when the broiler chickens were fed low dietary protein pellets may partly be attributed to the hardness of these pellets. The low intake of the hard pellets may also be responsible for low FCE, as performance is directly related to food intake. This poor food intake of hard pellets is in accord with the findings of Allred et
pellets may have occurred as a result of low concentrations of high fat ingredients in the feed. The quality of the food offered to the chickens has an influence on the appetite (Emmans and Fisher, 1986). This can be justified by the increased food intake as the quality was improved.
The significant improvement in food utilisation due to pelleting was not surprising, as it has constantly been noted with older birds (Calet, 1965) and with younger birds (Penz, 2002). Jensenet al.(1962) showed that while pelleting only slightly affects the number of meals,the duration of each meal is reduced three-fold in broiler chickens when the feed is pelleted. Although meal lengths and frequency were not objectively determined in this experiment, the subjective behavioural observations confirmed the above reports. In accordance with the conclusion of Savory (1974), who carried out behavioural studies, chickens fed pellets were less active, as they "sat" more and spent less time eating. The inability of allocation of mash feed inside the cages to improve food utilization beyond its location outside the cage may be attributed to food wastage, which was observed when inside troughs were used.
FCE was improved by pelleting the feed, independent of the amount consumed. This beneficial effect in food utilization due to pelleting occurred despite a decreased food intake due to hardness of low protein pellets. The hardness and length of low protein pellets observed may have had an adverse effect on the adaptation of the gastro-intestinal tract, and affected the bird's overall response to feeding pellets during the periods studied.
The improved food utilization that occurred when pellets were used indicates that large particles are suitable for the young chicks and may have enhanced development of the intestinal tract compared to mash feed.
3.8 Conclusions
Dietary protein content was positively related to performance. Chicks showed a positive response in all measures of performance when the feed troughs were placed inside the cages, except for food intake when mash was located in this position. The positive response of the chicks to pelleting also proved that pelleting is beneficial for young chicks.