Location: Dairy Forage ResearchTitle: Performance of dairy cows fed conventional sorghum or corn silages compared to brown midrib sorghum silage: a meta-analysis
|SANCHEZ-DUARTE, JUAN - South Dakota State University|
|GARCIA, ALVARO - South Dakota State University|
|CONTRERAS-GOVEA, FRANCISCO - University Of Wisconsin|
Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/11/2017
Publication Date: 6/25/2017
Citation: Sanchez-Duarte, J.I., Kalscheur, K., Garcia, A.D., Contreras-Govea, F.E. 2017. Performance of dairy cows fed conventional sorghum or corn silages compared to brown midrib sorghum silage: a meta-analysis [abstract]. American Dairy Science Association Abstracts. 100(Suppl 2):109-110.
Technical Abstract: A meta-analysis was conducted to compare the effects of feeding dairy cows conventional sorghum (CSS) or corn silages (CCS) vs. brown midrib sorghum silage (BMRSS) on dry matter intake (DMI), milk yield, and milk composition. Data from nine published articles (1984-2015) were used to contrast CSS (7 comparisons; 104 cows) or CCS (13 comparisons; 204 cows) vs. BMRSS. Statistical analysis was performed using fixed or random effects models in R. The degree of heterogeneity was measured with I2 statistics, and publication bias was determined with funnel plots and Egger´s regression test. Other sources of heterogeneity of response were analyzed through meta-regression. Estimated effect size was calculated for DMI, milk yield, and milk composition. No evidence of publication bias was observed for all variables tested. DMI and milk yield had the highest (I2=41.5 [CSS vs. BMRSS]; I2=72.6% [CCS vs. BMRSS]); and lowest (I2=0%) degree of heterogeneity, respectively. Compared to CSS, cows fed BMRSS tended to increase DMI (0.83 kg/d; P=0.09), and significantly increased milk yield (1.64 kg/d; P<0.001), milk fat (0.09%; P=0.03), and yields of milk fat (0.08 kg/d; P<0.001), protein (0.04 kg/d, P<0.001), and lactose (0.16 kg/d; P=0.02). No differences were observed for milk protein and lactose percentage (P>0.05). Compared to CCS, cows fed BMRSS increased milk fat (0.10%; P=0.009), but decreased milk protein (0.06%; P=0.03). There were no effects on DMI, milk yield, yields of milk fat, protein, and lactose, and lactose percentage between CCS and BMRSS. Meta-regression indicated that days in milk affected DMI and milk production when CSS was compared to BMRSS, and DMI when CCS was compared to BMRSS. Overall, lactation performance improved when cows were fed diets formulated with BMRSS compared to cows fed diets formulated with CSS. However, performance was not different between cows fed BMRSS and CCS. Future research comparing BMRSS with CSS or CCS needs to consider days in milk since cows respond differently throughout their lactation according to meta-regression analysis.