We hypothesized that steam-flaking the high-starch grains can stimulate ruminal microbial activity and reduce cecal fermentation due to lowering starch escaping in to hind-hut of young calves. Therefore, the current study evaluated the effect of steam-flaking the grains (corn grain vs. barley grain) with either 18% (18CP) or 22% (22CP) dietary protein content (dry matter basis) on growth performance, microbial protein synthesis (MPS) and inflammatory markers in young calves. Female Holstein calves (48 calves with 3 d of age) were assigned randomly to the following treatments: SFC-18CP, SFC-22CP, SFB-18CP, and SFB-22CP (n=12, each). Milk feeding schedule was identical among treatments until weaning (d 53), and calves had ad-libitum access to water and starters until the final day of experiment (d 73). Feeding SFC increased starter intake compared to calves fed SFB diet (p = 0.05; pre-weaning, have greater feed efficiency (tendency, p = 0.07; post-weaning), better fecal score (p = 0.01), and higher hip height (p = 0.03; post-weaning) compared to calves fed SFB diet. However, ruminal pH was lower (p = 0.04; pre-weaning), heart girth was smaller (p = 0.02), and post-weaning circulating tumor necrosis factor-α was greater (TNF-α, p = 0.03) for calves fed SFB compared to calves fed SFC diet. Feeding 22CP compared to 18CP diet improved hip height at weaning time (p =0.01) and reduced pre-weaning serum amyloid A (SAA, p = 0.04). With respect to the interaction, results indicated that higher ADG (p = 0.04) and subsequently higher BW (p < 0.05) was detected for calves fed SFC along with 22CP diet compared to other experimental arrangements. The calves fed SFB along with 18CP diet had lower withers height (p = 0.01), lower urinary allantoin (p = 0.02), and MPS (p = 0.04); but higher TNF-α (p = 0.01; pre-weaning) and higher SAA (p=0.04; post-weaning) was found to be for SFB-18CP diet compared to other experimental treatments. . Optimal processing method applied for high-starch grains to increase ruminal fermentation and prevent starch escaping in to the hind-gut of young calves for reducing cecal fermentation needs to be more evaluated in milk-fed calves.
