Meta-analysis of the effects of supplemental rumen-protected choline during the transition period on performance and health of parous dairy cows

摘要

The objectives were to use meta-analytic methodsto determine the effects of amount of supplementalcholine ion as rumen-protected choline (RPC) startingprepartum on production and health of dairy cows.The literature was systematically reviewed and 21 experiments,with up to 66 treatment means and 1,313prepartum parous cows, were included. All experimentshad a treatment with no supplemental choline (0 g/d;n = 30 treatment means), and the amount of cholineion supplemented to treated cows ranged from 5.6 to25.2 g/d (n = 36 treatment means). Duration of preandpostpartum feeding of RPC averaged (±standarddeviation) 22.0 ± 6.0 and 57.5 ± 42.2 d, respectively.Data collected included the ingredient compositionand chemical analyses of pre- and postpartum diets,amount of choline ion supplemented, number of cowsper treatment, frequency of health events, and the leastsquares means and respective standard error of themeans for production responses, liver composition, andblood parameters. The concentrations of net energy forlactation and metabolizable amino acids and protein(MP) in pre- and postpartum diets were predicted foreach treatment mean using National Research Council(2001). Mixed model meta-analysis was conductedincluding the random effect of experiment and weightingby the inverse of the standard error of the meanssquared. Increasing supplementation of choline ionduring transition linearly increased pre- (β = 0.0184 ±0.00425) and postpartum dry matter intake (β = 0.0378± 0.00974), and yields of milk (β = 0.436 ± 0.112),energy-corrected milk (ECM; β = 0.422 ± 0.0992), fat(β = 0.00555 ± 0.000793), and protein (β = 0.0138 ±0.00378). Nevertheless, an interaction between cholineand postpartum metabolizable methionine as a percentof MP (METMPPo) was observed for yields of milk,ECM, and protein because as METMPPo increased,the positive response to choline on yields of milk, ECM,and protein decreased. Supplementing choline duringtransition tended to reduce the risks of retained placentaand mastitis, but it had no effect on metritis,milk fever, displaced abomasum and ketosis, or theconcentration of triacylglycerol in the hepatic tissuepostpartum. The median amount of choline ion supplementedwas 12.9 g/d and responses in postpartum drymatter intake and yields of milk, ECM, fat, and proteinto that amount of supplementation were 0.5, 1.6, 1.7,0.07, and 0.05 kg/d, respectively. No interactions wereobserved between supplemental choline and prepartumdietary net energy for lactation or metabolizable methionineas a percent of MP. Collectively, feeding RPCduring the transition period improves performancein parous cows. Increases in yields of milk and milkcomponents were observed in spite of pre- and postpartumdiets, although the increments in milk, ECM, andprotein yields with supplementing choline decreased asthe concentration of methionine in postpartum dietsincreased. The optimum dose of choline ion was notdetected, but likely it is more than the 12.9 g/d fedin most experiments evaluated in the current metaanalysis.Finally, the meta-analysis identified lack ofsufficient data to understand the role of supplementalcholine in nulliparous cows.