Nutritive Value of Thermoalkali-Processed Soy Materials for Young Calves and Rats

Thermoalkali-processed soy protein concentrates (experimental soy concentrate) were compared with sodium caseinate and a commercial soy protein concentrate (Promocaf) as protein sources in milk replacers, supplying .75 of the protein in 20%-protein replacers.Week-old Holstein calves were fed the replacers in two 4-wk trials.Average gains of calves fed experimental soy concentrate (processed 5 min at 85 C and pH 10.5), caseinate, and Promocaf replacers were 3.0, 6.6, and 6.6 kg.Calves fed experimental soy concentrate replacers heated for shorter or longer times lost .8 to 3 kg weight during the first 2 wk but gained .6 to 1.7 kg during the~ last 2 wk.Occasionally calves had loose feces, mainly during the first 2 wk, with no significant differences between groups.Efficiency with which rats used protein of nonfat, spraydried, milk-replacer ingredients correlated .96with growth of calves fed corresponding replacers.Growths and protein efficiency ratios were similar when rats were fed lyophilized, thermoalkali-p rocessed soy products heated for various times up to 1 h at either 85 CandpH 10.5 or 75 Cand pH 9. Rats fed the experimental soy c one entrate performed satisfactorily~; calves, less satisfactorily.The protein efficiency ratio of experimental soy products determined with rats correlated .68 with in vitro protein digestibility, -.60 with soluble nitrogen, and -.59 with trypsin inhibitor activity.