Evaluation of rumen protected rapeseed expeller (NovaPro) as an alternative to soya bean meal in dairy cow diets

Abstract

There are environmental, social and economic pressures to reduce the use of soya bean meal in ruminant diets by using alternative protein sources, such as those derived from rapeseed. A new protected form of rapeseed (NovaPro) has been developed to provide similar quantities of digestible undegradable protein (DUP) compared to soya bean meal. NovaPro is hot pressed expelled rapeseed (no hexane solvent used), treated with a specific wood derived xylose-rich lignosulphonate in the presence of elevated moisture and heat to increase DUP. The objective of this study was to evaluate NovaPro as a protein supplement for high yielding dairy cows.Four diets were formulated to supply similar quantities of metabolisable energy and protein but containing different dominant protein sources. The main protein sources were: Control – soya bean and rapeseed meals; NP1 – NovaPro and wheat dried distillers grains with solubles (DDGS); PR – protected solvent-extracted rapeseed meal and wheat-DDGS; NP2 - NovaPro and SoyPass. Diets were fed to 44 cows using a Latin square design with four feeding periods of 28 days each.Milk yield was significantly higher when cows were fed on rapeseed treatment diets (mean 42.7 kg/d) than when fed on the control diet (mean 41.1 kg/d), as was energy-corrected milk (ECM) yield (mean 43.2 versus 41.7 kg/d). Dry matter intake was higher when cows were fed on NP1 and NP2 (mean 25.0 kg/d) than when they were fed on the control diet (mean 23.9 kg/d); dry matter intake for PR was intermediate (mean 24.4 kg/d). Concentrations of milk fat and protein reflected differences in milk yield, and there was no difference between treatments in fat or protein yield, although fat plus protein yield was higher when cows were fed on rapeseed treatment diets (mean 2.84 kg/d) than when fed on the control diet (mean 2.72 kg/d).Differences in rumen fluid and blood composition were commensurate with differences in diet composition, nutrient intake and milk yield. Retrospective calculation of metabolisable energy and protein supplies showed that these were within 3% of requirements for observed responses. Calculation of amino acid profiles suggested that profiles, particularly methionine, were better for the rapeseed treatment diets.Results of this study support the hypothesis that cows fed on NovaPro and other rumen protected rapeseed proteins will have similar or improved milk production compared to a control (soya-based) diet. Improved milk yield was accompanied by increased dry matter intake, but it is likely that intake was driven by milk yield rather than vice versa. The most likely explanation for improved milk yield when cows were fed on the rapeseed treatment diets is that amino acid balance was improved compared to control.