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  • The Protein Problem: An Expensive Feed Ingredient Poorly Used By The Dairy Cow

    Protein is a critical part of dairy cow diets and has a significant impact upon feed costs and environmental pollution. A major problem is that nitrogen retention from ingested feed protein is very low, some 25% in dairy cows (Calsamiglia et al., 2021). As much as 75% of feed protein is returned to the environment in manure which creates environmental problems. In the Netherlands, cattle farming, both dairy and beef, is a major source of ammonia emission, a product of waste nitrogen (Velthof et al., 2012). Therefore, on both economic and environmental grounds, efficient protein usage is essential in dairy cow management.

    In dairy cows, feed protein is fermented by the rumen microbes into microbial protein which then becomes a source of amino acids for the cow. The protein requirement for milk or growth is then obtained from the microbial protein synthesized in the rumen and the undegraded dietary protein (UDP) in the feed. Improved microbial protein production in the rumen can decrease the need for undegraded dietary protein and improve utilisation of the dietary protein fed (Thirumalesh and Krishnamoorthy, 2013).

    It is well established that Glycal Forte can manage rumen function in the transition cow via optimising rumen pH etc. As well as this, based on observed responses in dairy cows it was previously suspected that Glycal Forte produced more microbial activity in the rumen. Therefore, the ability of Glycal Forte to improve rumen biomass has been studied by both in vitro and in vivo techniques.



    In vitro studies are extensively used in ruminant nutrition to develop novel concepts or principles. In this independent study, a significant improvement in microbial biomass production with Glycal Forte was demonstrated using a gas evolution technique with a TMR compared to the control and the glycerol group (Table 1).


    Table 1. Digestibility of a TMR with Glycal Forte or glycerol.

    Treatment Graph

    MBM = microbial biomass



    Milk urea values give a general indication of the protein utilization by the dairy cow. A general recommendation is for milk urea to be around 0.020-0.035 % (200-350 mg/kg) for optimal dairy cow performance. Milk urea values either below or above this range of 0.020-0.035 % (200-350 mg/kg) indicate possible feed utilization or feed intake issues. Below 0.02% (200 mg/kg) there can be a protein deficiency or excess energy, and this indicates poor rumen synchrony.

    In this on-farm study, a herd of transition cows with very low milk urea values were used to investigate the effect of Glycal Forte from 5-30 days post-calving on urea values. As shown in Figures 1 and 2, initial milk urea values at day 5 were 0.012% (120 mg/kg) in the control group and 0.006 (60 mg/kg) in the group to receive Glycal Forte, which is extremely low.

    Over the experimental period the milk urea values in the control group remained very low, only reaching 0.018% (180 mg/kg) at 30 days post-calving (Figure 1). The regression analysis showed an R-squared of only 3.5% indicating no relationship between milk urea and days after calving. It is evident from Figure 1 that the milk urea values are unlikely to reach an acceptable value of 0.03% any time soon.

    Figure 1. Regression analysis for milk urea values in control cows over 5-30 days post-calving.

    By contrast the group fed Glycal Forte showed a continuous increase in milk urea values reaching 0.029% (290 mg/kg) by day 30 which is in the middle of the recommended range for milk urea of 0.020-0.035%. Furthermore, the R-squared value in the regression analysis was over 10 times better than the control at 36.4. This indicates a strong relationship between milk urea and days after calving when cows were fed the same diet with added Glycal Forte.

    Figure 2. Regression analysis for milk urea values in cows fed Glycal Forte over 5-30 days post-calving.


    This on-farm animal trial shows that Glycal Forte was able to dramatically improve milk urea values in the post-calving period. This suggests better protein utilization from the feed due to improved rumen biomass. This in vivo trial is entirely consistent with the in vitro data presented in Table 1.

    The ability of Glycal Forte to improve rumen biomass which in turn improves utilization of dietary protein has important implications for dairy cow management. Feed protein prices currently are extremely high and nitrogen excretion from dairy cows is a serious environmental concern. The data from the in vitro and in vivo trials with Glycal Forte strongly suggest that addition of Glycal Forte to dairy rations would have a Protein Sparing Effect. For example, it may well be possible to reduce the feed protein level by 1-2% subject to the type of diet already fed.  This could reduce daily feed costs and protein wastage on farm.



    Calsamiglia, S., Ferret, A., Reynolds, C. K., Kristensen, N. B.and van Vuuren, A. M. (2010). Strategies for optimizing nitrogen use by ruminants. Animal 4, 1184-1196.

    Thirumalesh, T. and Krishnamoorthy, U. (2013). Rumen Microbial Biomass Synthesis and Its Importance in Ruminant Production. International Journal of Livestock Research, 3: 5-26.

    Velthof, G. L., van Bruggen, C., Groenestein, C. M., de Haan, B. J., Hoogeveen, M. W. and. Huijsmans, J. F. M. (2012). A model for inventory of ammonia emissions from agriculture in the Netherlands. Atmospheric Environment, 46: 248-255.