The present study was conducted to investigate effect of rumen protected amino acids inclusion in diet on milk yield and composition of Holstein dairy cow using meta-analysis. Total 21 published studies were employed in meta-analysis. Effects of rumen protected amino acids were classified according ...
The present study was conducted to investigate effect of rumen protected amino acids inclusion in diet on milk yield and composition of Holstein dairy cow using meta-analysis. Total 21 published studies were employed in meta-analysis. Effects of rumen protected amino acids were classified according to used amino acids: methionine and methionine+lysine. Prior to the calculation of effect size, linear regression model was established using mixed model, and RMSPE (root mean square predicted error) of individual results in each study was calculated using established model. Then RMSPE value of each results was assumed as standard deviation value for the calculation of standardized mean difference. Finally, effect size of application of protected amino acid were calculated. At low crude protein diet condition, regression analysis for the effect of protected methionine by mixed model showed a trend of increasing milk yield and represented significantly decreased milk protein (p<0.05). Milk fat content was not changed by inclusion of protected methionine in low crude protein diet. In summary effect evaluated by the calculation of standardized mean difference, negative effects of protected methionine on milk yield content was found at both of fixed and random effect model, and the significance was detected only in fixed effect model (p<0.05). In milk protein content, fixed effect model showed significant negative effect (p0.05). Effect of protected methionine on milk fat content was positive at both of fixed and random effect model, however significance was found only in fixed effect model (p0.05). From standardized mean difference analysis, effect of protected methionine on milk yield was negative at both of fixed (p0.05). Whereas significant positive effect on milk protein content was measured at both of fixed and random effect model (p<0.05). In milk fat content, fixed effect model showed significant positive effect (p0.05). Inclusion of protected methionine and lysine mixture at low crude protein diet condition showed negative slope in all measured parameters by regression analysis using mixed model however, those effects were not significant (p>0.05). In standardized mean difference, fixed effect model showed significant negative effect on milk yield. However, positive effect on milk yield in random effect model was found without significance (p>0.05). Positive effect of protected methionine and lysine mixture on milk protein content was detected at both of fixed (p>0.05) and random effect model (0.1>p>0.05). And positive effect on milk fat content was found at both of fixed (p0.05). In effects of protected methionine and lysine mixture at high crude protein diet condition measured by regression analysis, increased milk yield and decreased milk protein and fat were found. However, those effects were not significant (p>0.05). In standardized mean difference analysis, significant positive effects on milk yield and protein were found (p<0.05). Effect on milk fat content was also positive in both of fixed (p0.05). The present work used two analytical tools, regression using mixed model and standardized mean difference, for estimation of protected amino acid effect on milk performance. Both of those tools were frequently used in meta-analysis and regarded as high through-put in extraction of summary effect. However, this works employed regression analysis to calculated deviation value of results at each study. So this work concluded the effect of protected amino acid on milk performance based on standardized mean difference. The present study hypothesized that there was a discrepancy on the benefit of use of protected amino acid in dairy cow. And the forest plots represented effects of individual studies and their treatments showed largely scattered. And this patterns could be regarded to support the hypothesis of this work. As a conclusion, a series of analysis suggested that application of protected amino acid could represent more positive effect at high crude protein diet (>18%) than low diet (<16%). In the consideration of used amino acid, combination of methionine and lysine showed more great positive effect than the application of methionine only.
The present study was conducted to investigate effect of rumen protected amino acids inclusion in diet on milk yield and composition of Holstein dairy cow using meta-analysis. Total 21 published studies were employed in meta-analysis. Effects of rumen protected amino acids were classified according to used amino acids: methionine and methionine+lysine. Prior to the calculation of effect size, linear regression model was established using mixed model, and RMSPE (root mean square predicted error) of individual results in each study was calculated using established model. Then RMSPE value of each results was assumed as standard deviation value for the calculation of standardized mean difference. Finally, effect size of application of protected amino acid were calculated. At low crude protein diet condition, regression analysis for the effect of protected methionine by mixed model showed a trend of increasing milk yield and represented significantly decreased milk protein (p<0.05). Milk fat content was not changed by inclusion of protected methionine in low crude protein diet. In summary effect evaluated by the calculation of standardized mean difference, negative effects of protected methionine on milk yield content was found at both of fixed and random effect model, and the significance was detected only in fixed effect model (p<0.05). In milk protein content, fixed effect model showed significant negative effect (p0.05). Effect of protected methionine on milk fat content was positive at both of fixed and random effect model, however significance was found only in fixed effect model (p0.05). From standardized mean difference analysis, effect of protected methionine on milk yield was negative at both of fixed (p0.05). Whereas significant positive effect on milk protein content was measured at both of fixed and random effect model (p<0.05). In milk fat content, fixed effect model showed significant positive effect (p0.05). Inclusion of protected methionine and lysine mixture at low crude protein diet condition showed negative slope in all measured parameters by regression analysis using mixed model however, those effects were not significant (p>0.05). In standardized mean difference, fixed effect model showed significant negative effect on milk yield. However, positive effect on milk yield in random effect model was found without significance (p>0.05). Positive effect of protected methionine and lysine mixture on milk protein content was detected at both of fixed (p>0.05) and random effect model (0.1>p>0.05). And positive effect on milk fat content was found at both of fixed (p0.05). In effects of protected methionine and lysine mixture at high crude protein diet condition measured by regression analysis, increased milk yield and decreased milk protein and fat were found. However, those effects were not significant (p>0.05). In standardized mean difference analysis, significant positive effects on milk yield and protein were found (p<0.05). Effect on milk fat content was also positive in both of fixed (p0.05). The present work used two analytical tools, regression using mixed model and standardized mean difference, for estimation of protected amino acid effect on milk performance. Both of those tools were frequently used in meta-analysis and regarded as high through-put in extraction of summary effect. However, this works employed regression analysis to calculated deviation value of results at each study. So this work concluded the effect of protected amino acid on milk performance based on standardized mean difference. The present study hypothesized that there was a discrepancy on the benefit of use of protected amino acid in dairy cow. And the forest plots represented effects of individual studies and their treatments showed largely scattered. And this patterns could be regarded to support the hypothesis of this work. As a conclusion, a series of analysis suggested that application of protected amino acid could represent more positive effect at high crude protein diet (>18%) than low diet (<16%). In the consideration of used amino acid, combination of methionine and lysine showed more great positive effect than the application of methionine only.
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