Effects of Supplementing Rumen-Protected Met and Lys on Diets Containing Soybean Meal or Canola Meal in Lactating Dairy Cows
Previously, replacing solvent soybean meal (SBM) with equal CP from canola meal (CM) was found to increase milk yield in lactating dairy cows by about 1 kg/d. We tested whether supplementing rumen-protected Met and Lys (RPML) would improve milk and protein yield in cows fed either CM or SBM. Sixteen lactating Holstein cows were blocked by DIM and parity into 4 squares of 4 cows each in a replicated 4 x 4 Latin square. There was a 2 x 2 arrangement of treatments: equal CP supplemented as either SBM or CM, with or without added RPML to provide 10 g absorbed Met/d (Mepron®) plus 22 g absorbed Lys/d (AminoShureL®). Cows within squares were randomly assigned to treatment sequences and fed experimental diets for 3-week periods before switching diets. All diets contained (DM basis) 41% alfalfa silage, 25% corn silage, 2.3% mineral-vitamin premix, 1.4% ground shelled corn and 17% CP. Soybean meal diets contained 22% high moisture corn, 8.7% SBM and 28% NDF; CM diets contained 19% high moisture corn, 11.7% CM and 30% NDF. Data from the last week of each period were analyzed using the mixed procedures of SAS; LS-means are reported in the table. Replacing SBM with CM increased DMI (P = 0.04) and tended to increase yields of energy-corrected milk and fat (P ≤ 0.09), but there were no other affects on production (P ≥ 0.15). Supplementing with RPML did not influence intake or yield (P ≥ 0.15) and no significant of protein x RPML interactions were detected (P ≥ 0.15). These results tended to support previous findings of improved milk yield on CM versus SBM. However, under the conditions of this trial, there were no effects of supplementing with rumen-protected Met plus Lys on either protein source.
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