PHOTO: HENK RISWICK


NUTRITION ▶▶▶


Until recently the effects of different miner- al sources in par- ent feed on bone develop- ment in broilers had hardly been studied.


while the tibia was removed from the right leg for further examination. The weight, length, volume, mineral content and mineral density of the tibias were determined. Finally, the same tibias were broken to determine the force required to break these bones. Stronger bones with more minerals need more force to be broken and are therefore more able to support the weight of the chicks.


Results On average, the hatching rate of the hatching eggs was 86% of the fertilised eggs. This did not differ between the feed treatments of the parent stock. No effects of the mineral source in the parent stock feed on chick quality at hatching were found either. The mineral concentration in the eggs and in the day-old chicks was hardly influenced by the mineral source provided to the parent stock. This was contrary to ex- pectations. However, the mineral source in the parent feed had a major effect on the growth of the Hubbard broilers, while this was not the case for the Ross broilers. In the Hub- bard chicks, the difference in body weight on day 49 between the inorganic and organic parent feed was 132 grams (see Table). Feed intake and feed conversion were not influenced by the mineral source of the parent stock. The effects of the mineral source in the parent feed on the tibias were clear. Chicks from parent stock fed on organic


28 ▶ POULTRY WORLD | No. 6, 2022


minerals had better developed bones: they had thicker bones with a better mineral density and with a higher breaking strength. For some tibia traits this was only observed in the Hubbard chicks and not in the Ross chicks, while for other tib- ia traits this was true for both the Hubbard and the Ross chicks. Better bone development is positive for bearing the animals’ weight and could result in fewer leg problems. How- ever, the latter was not found in this study. The percentage of chicks with leg problems was very small in this experiment and no differences were found between the two mineral sources in the feed of the parent stock.


Clear effect Organic minerals in parent feed had a positive effect on the quality of the tibia of their offspring (broilers) for both Ross and Hubbard. This effect was greater in the slower growing chicks. A clear effect on growth was also found here. The reason it was particularly visible in Hubbard chicks may have to do with the lower feed intake of the parent stock but it is also possible that we are not yet fully aware of the optimum mineral levels in the feed of slower growing parent stock. Be- cause the mineral content in both the eggs and the day-old chicks hardly differed, it is not clear how the effects of organic minerals in the parent feed affect the broilers. This will have to be further researched.


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