Gradual weaning does not improve performance for calves with low starter intake at the beginning of the weaning process

摘要

The weaning process may cause intense stress fordairy calves, even when low volumes of liquid diet arefed. Management tools that increase the intake of solidfeeds, such as gradual weaning, can provide betterphysiological and metabolic conditions through betterruminal development, leading to better adaptation toruminant metabolism and aiding in stress mitigation.The objective of this study was to evaluate the effectsof 2 weaning protocols and 2 levels of concentrate intakeon the performance and physiological and behavioralvariables related to stress in dairy calves. Thirty-sixnewborn male Holstein calves were used in a randomizedblock design with a 2 × 2 factorial arrangement:2 weaning strategies, abrupt or gradual, and 2 levelsof concentrate intake at 5 wk of age, high (>350 g/d)or low (≤350 g/d). Calves were equally managed untilthey were 5 wk of age and then grouped according toconcentrate intake. Statistical analyzes were performedusing the MIXED procedure of SAS software (SASInstitute Inc., Cary, NC), and no significant interactionwas observed between studied factors (weaningmethod and starter intake level); therefore, we consideredeach factor separately and their interactions withage. The highest dry matter intake and concentrationof β-hydroxybutyrate were recorded for animals with ahigh level of starter intake independent of the weaningmethod. Structural growth (cm/wk) and average dailygain were superior for calves with high starter intake,but weaning method had no effect. The gradual weaningprotocol increased the time eating starter, regardlessof the level of concentrate intake. Even animalswith low concentrate intake that were weaned abruptlyshowed levels of cortisol and acid-soluble glycoproteinwithin normal physiological levels. Apparently, otherfactors besides the milk supply affect the starter intakelevel of calves in a conventional feeding program. Theadoption of gradual weaning is not effective in improvingperformance when a calf has low intake 3 wk beforeweaning is complete, but it reduced vocalization on d2 postweaning.