During weaning, methionine (Met) supply decreases as liquid feed isreduced and rumen function is developing. During this transition, calfstarter should both promote rumen development and provide adequatenutrients postruminally. Rumen-protected forms of Met (RPM), andMet analogs, such as HMTBa or HMBi are used to increase Met supply,stimulate ruminal fermentation, or both. Our hypothesis was Met is alimiting AA and Met analogs might facilitate rumen development duringthis period. To test this hypothesis, 74 14 d old Holstein calves wereindividually housed from birth to 91 d of age, in 2 enrollment periods.Milk replacer (28% CP, 15% fat) was offered up to 1.6 kg DM/d. Calveswere balanced for sex and randomly assigned to receive a control starter(CTRL, n = 20) or one supplemented with RPM (n = 16), HMTBa (n =19), or HMBi (n = 19). Starters (23% CP, 2.5 Mcal ME/kg) were offeredad libitum and supplement inclusion was set to provide an additional0.16% DM of Met equivalents. Weaning occurred from d 49 to 63. Bodyweight (BW) was measured weekly. Data were analyzed as a randomizedblock design with repeated measures over time, using enrollmentperiod as block. Pre-planned contrasts were conducted against theCTRL. RPM and HMBi inclusion enhanced starter intake preweaningand HMBi tended to increase intake postweaning (Table 1). However,there were no differences from CTRL in postweaning BW or BW gain.Post-hoc contrasts among Met supplements indicated HMBi improvedfeed intake and BW gain postweaning (P < 0.05) with a tendency forgreater final BW (P = 0.06).
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