Effects of milk replacer plane of nutrition and levels of starch and neutral detergent fiber in pelleted starter on whole gastrointestinal tract pH around weaning.
The objectives of this study were to examine the effects of pelleted starter diets differing in starch and NDF content when fed differing levels of milk replacer (MR) on gastrointestinal pH rumen pH around weaning in dairy calves. The 4 dietary treatments (Trt; n = 12 per trt) were: 691 g MR/day (dry matter basis; DM) with starter containing low or high starch (LL:12.0% and LH:35.6% starch, respectively) and 1,382 g MR/day (DM) with starter containing low or high starch (HL and HH, respectively). All calves were in individual pens with straw bedding until wk 5 when bedding was covered. Calves were fed MR twice daily (0700 and 1700 h) containing 24.5% CP (DM), 19.8% fat (DM), and had ad libitum access to starter and water. Calves arrived between 1 and 3 d of age and the study lasted 8 wk with calves undergoing step-down weaning during wk 7. Starting at wk 5, an indwelling pH logger was inserted orally to monitor rumen pH until calves were dissected at the end of the study in wk 8. Data were analyzed using PROC MIXED in SAS 9.4 with the fixed effects of Trt, week, and their interaction, and random effect of calf nested within Trt. There were no differences between Trt or interaction within week for time below rumen pH 5.8, but there were trending differences between Trt for time below rumen pH 5.0 and 4.5 (Table 1). There were also Trt differences in rumen and abomasal pH at dissection (Table 1). Modest differences were present between Trt, suggesting further research and refinement of diets (altering feed particle size) may help our understanding of the effects of plane of MR and starch levels on gut development and health in calves.