
Supplemental material for "Lactational performance effects of 3-nitroxypropanol supplementation to dairy cows: A meta-regression"
A meta-regression was conducted to determine the production effects of 3-nitrooxypropanol (3-NOP) and investigate their associations with dose, dietary nutrient composition, and supplementation length in dairy cows. Forty treatment and control mean comparisons extracted from 21 studies conducted or published between 2014 to 2024 were used in the meta-regression. Response variables were DMI, MY, energy-corrected milk (ECM) yield, ECM feed efficiency, BW, BW change, and concentrations of milk fat, true protein, lactose, and milk urea nitrogen. Treatment and control mean differences (MD) as well as standardized MD were calculated and used for data presentation and statistical analysis, respectively. Dose (± SD; 77.0 ± 33.17 mg 3-NOP/kg DMI), forage-to-concentrate ratio (FC; 58.9 ± 8.83% expressed as average ± SD % of forage in the diet), dietary concentrations of CP, ether extract, NDF, and starch (16.3 ± 1.84, 4.3 ± 1.03, 33.7 ± 4.40, and 20.9 ± 3.97% as average ± SD% of DM, respectively), supplementation length (days), and days-in-milk and BW of the cows at the beginning of the study were used as continuous explanatory variables. Mixed-effects models were fitted using the robust variance estimation method. Full models containing uncorrelated explanatory variables (Pearson’s correlation < 0.50) were fitted and variables removed from the final model if non-significant using the stepwise selection approach. Compared with control, supplementation of 3-NOP decreased DMI and MY by 0.80 ± 0.149 and 0.98 ± 0.250 kg/d, respectively, but only numerically decreased ECM by 0.50 ± 0.298 kg/d. Consequently, feed efficiency was increased by 0.05 ± 0.012 kg ECM/kg DMI with 3-NOP supplementation. Body weight and BW change were not affected by 3-NOP supplementation. Milk fat, true protein and milk urea nitrogen concentrations were increased by 0.09 ± 0.028%, 0.02 ± 0.006%, and 0.59 ± 0.106 mg/dL, respectively. Increasing 3-NOP dose further decreased DMI and increased milk fat and milk urea nitrogen concentrations. Increasing dietary NDF and FC lessened the negative effect of 3-NOP on DMI and MY, respectively, and decreased its positive effect on milk fat and milk urea nitrogen (dietary NDF concentration effect only). Similarly, increasing dietary CP lessened the negative effect of 3-NOP on DMI and decreased its positive effect on milk urea nitrogen. To explain some of the production effects herein observed, ruminal fermentation data from 6 published studies were included in the meta-regression. Supplementation of 3-NOP tended to increase rumen pH and decreased NH3 concentration. Concentrations of total VFA, acetate, and the acetate-to-propionate ratio were decreased, whereas the concentration of propionate was increased, and that of butyrate was numerically increased by 3-NOP supplementation. Overall, 3-NOP supplementation of dairy cow diets decreased DMI and MY but did not affect ECM because of increased milk fat and true protein contents. Increased milk fat and milk urea nitrogen responses can be explained by shifted ruminal fermentation, and the increased milk true protein response may be explained by increased rumen propionate molar proportion by 3-NOP supplementation.
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Work Title | Supplemental material for "Lactational performance effects of 3-nitroxypropanol supplementation to dairy cows: A meta-regression" |
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License | CC BY 4.0 (Attribution) |
Work Type | Other |
Publication Date | 2024 |
DOI | doi:10.26207/h6qs-vw40 |
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Deposited | October 24, 2024 |
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