Ruminant Nutrition General

摘要

The objective was to quantify the effect of Cr supplementation on productionand how the effect changes based on Cr source and stage of lactation.A meta-analysis was performed with data from 28 studies and 93 treatmentmeans from experiments testing the supplementation of Cr startingin the dry period (n = 38) and during lactation. Studies utilized Cr asCr-Picolinate, Cr-Yeast, Cr-Chelate, Cr-Methionine, or Cr-Propionate.Using the metaphor package in the R software, we modeled the meandifference between the experimental (cows receiving Cr) and controlgroups. Response variables were milk yield (MY; kg/d), energy-correctedmilk (ECM; kg/d), and dry matter intake (DMI; kg/d). Difference inMY had a quadratic response to Cr supplementation expressed in mg/dand a quadratic response to days in milk (DIM). The model ΔMY =–4.65 (±1.85) + 0.640 (±0.264) × Cr – 0.0477 (±0.0173) × Cr2+ 0.0949(±0.0318) × DIM – 0.0005 (±0.0002) × DIM2 suggest supplementationof Cr is maximized at 6.7 mg and when cows are at 95 DIM. Maximumincrease in MY is 2 kg/d and then continues at a decreasing rate up to13 mg of Cr and in cows up to 156 DIM. Using Cr-methionine furtherincreases MY by 2 kg/d but there was no difference with other sourcesof Cr. With the model for ΔECM = –4.21 (±1.65) + 0.697 (±0.216) × Cr– 0.0510 (±0.0142) × Cr2 + 0.0843 (±0.0310) × DIM – 0.0004 (±0.0004)× DIM2 supplementation of 6.8 mg of Cr to cows up to 105 DIM is suggestedfor a maximum increase of 2.6 kg/d of ECM. Increase in ECMwas not affected by Cr source. model ΔDMI = –3.19 (±0.76) + 0.214(±0.099) × Cr – 0.0113 (±0.0066) × Cr2 + 0.0607 (±0.0145) × DIM –0.0003 (±0.0003) × DIM2 suggest a dose of 9.5 mg of Cr up to 101 DIMto maximize DMI by 0.9 kg/d. DMI is increased another 2.9, 2.5, and 1kg/d by Cr-Yeast, Cr-Methionine and Cr-Propionate respectively. Overall,the effect of Cr supplementation is affected by stage of lactation andCr source. With these models and the cost of the different Cr productswe can predict what stage of lactation, Cr amount, and sources would bemost effective and give a recommendation that would maximize profits.