Young Scholar Presentation: Manipulating Early Lactation Energy and Protein Balances Using Canola Meal As a Protein Source

Negative energy and protein balances during the immediate postpartum period pose opportunities to improve dairy cow health and production. The inability of the cow to consume an adequate supply of nutrients leads to the mobilization of body reserves to serve as energy and protein supplies for milk production. Labile protein turnover can range from 8 to 21 kg in the first 5 to 6 wk of lactation. Turnover of protein stores can be used as amino acids for gluconeogenesis and synthesis of milk protein. Protein and specific amino acid requirements for dairy cows during the early lactation period are not well defined. The use of canola meal (CM) in dairy cow diets has recently shown favorable results in milk yield when compared to feeding soybean meal (SBM) based diets. Mid-lactation feeding experiments and meta-analysis methods showed that cows produced 0.77-1.41 kg/d more milk when fed CM compared to SBM and other vegetable-based protein sources. The amino acid profile of CM has recently garnered attention due to a more similar amino acid profile to milk protein vs. SBM. In addition, the SBM amino acid profile is higher in the two non-glucogenic amino acids Leu and Lys. Therefore, it was hypothesized that CM may provide a protein source that is more efficiently utilized by the cow during a period of negative energy and protein balance. Our laboratory conducted a feeding experiment utilizing a randomized complete block design with a 2 Î 2 factorial arrangement of treatments. Cows were evaluated during the first 16 wk of lactation. High (18.1%) and Low (16.2%) concentrations of crude protein were fed, using CM or SBM as protein sources. Cows fed CM consumed 0.80 ± 0.34 kg/d (P=0.09) more dry matter, and yielded 4.45 ± 0.97 kg/d (P<0.01) more milk than cows fed SBM. Milk component yield favored CM-based diets, and feed efficiency tended to be higher for cows fed CM (2.27 vs. 2.16 ± 0.38; P=0.06). Another possible difference may be the impact of the protein source on fiber digestibility. In a recent study, total-tract neutral detergent fiber digestibility was 48.1 vs. 45.1 % of neutral detergent fiber intake (P<0.01) for CM- vs. SBM-fed dairy cows. This may be another avenue in which animals fed CM are outperforming their SBM-fed counterparts. The dramatic increase in production and underlying mechanism for CM-fed animals compared to SBM-fed animals warrants further investigation.