Development of a procedure to determine standardized mineral availabilities in soybean meal for broiler chicks

The objective of this study was to develop a procedure for estimating the standardized mineral (calcium, Ca; phosphorus, P; copper, Cu; manganese, Mn; zinc, Zn) availabilities (SMA) in soybean meal for broilers. In experiment 1, twelve 24-day-old male chicks were used to determine the length of the pre-experimental fasting period needed to empty the total tract of feed residues. Feed was removed and excreta samples were collected for 12, 24, 36 or 48 h after feed withdrawal, respectively. The result indicated that birds were fasted for at least 24 h after feed withdrawal in order to ensure that no previous feed residues remained in the digestive tract of chicks. In a subsequent experiment, forty-eight 24-day-old male chicks were used to determine SMA in soybean meal. Chicks were fasted for 24 h and then fed mineral-free or soybean meal diet for 4 h, and excreta samples were collected until 24 or 48 h after feed withdrawal. The results showed that the extended excreta collection time of 48 h after feed withdrawal was adequate for estimating SMA. The standardized availability values of Ca, P, Cu, Mn or Zn in soybean meal were 51.14%, 50.22%, 36.28%, 30.79% or 49.66%, respectively. In experiment 3, a similar bioassay was conducted with forty-eight 36-day-old male chicks to measure SMA in the same soybean meal. The standardized availability values of P (51.59%), Cu (36.37%), Mn (31.94%) or Zn (43.37%) were similar (P > 0.12) to the results of experiment 2 except for Ca (41.49%), indicating that the age of birds had no effect on the standardized availabilities of P, Cu, Mn or Zn in soybean meal. The results from this study suggested that this simple and rapid procedure could be used to determine SMA in feedstuffs (e.g., soybean meal) for broiler chicks.