By Victoria Phillips BSc Agricultural Biochemistry and Nutrition and MSc Animal Production
Home-grown forage is the most important feed ingredient on any farm, and so using it effectively to achieve maximum performance and output from your livestock is critical. It is well established that the addition of molasses improves the palatability of any diet, but its role in increasing forage intake is much more important than simply improving taste.
When cattle digest molasses it is quickly utilised by the rumen microbes as an instant energy source resulting in increased digestive efficiency. Enhanced digestive efficiency results in higher production of microbial protein in the rumen, placing less reliance on expensive bought-in protein sources. By balancing a ration with molasses, the cellulytic rumen micro-organisms can capture more of the dietary nitrogen present (from grass or grass silage), thus maximising the breakdown of fibre in the forage, allowing more of the latter to be utilised in the daily ration.
The table below shows a silage based diet and the effect of adding molasses. The ration is feeding high yielding dairy cows (50 litres per day), with molasses incorporated at 1.1kg (1.5% of the ration) and 1.8kg (2.7% of the ration) respectively:
GREEN = GOOD BUN / YELLOW = ELEVATED BUN
Balancing the available protein and energy in the diet of a high yielding dairy cow is essential to maintain a healthy blood urea nitrogen (BUN). If the diet is rich is readily available nitrogen, but without a readily available source of energy (molasses), the nitrogen is converted to ammonia, which is absorbed into the blood. This ammonia is transported to the liver and converted to urea, and the urea is taken to the kidneys where excess urea is excreted. This ‘detoxification’ of ammonia in the liver requires energy, which is already in short supply in early lactation cows, so the high blood urea and ammonia concentrations will exacerbate the negative energy status of these animals.
Studies have shown that cows with low blood urea nitrogen were 2.4 times more likely to be confirmed pregnant, and those with the lowest levels had the fewest days to service – up to 40 days less. Cows with low or medium levels have 8-15% better fertility than those with high levels. This is somewhat due to the utilisation of energy by the liver to deal with the ammonia, but may also be the result of changes to the uterine environment which can adversely affect fertility, embryonic development and implantation, and is seen particularly in first lactation cows.
Conclusions
- Approx. 3% Increase for both grass and maize silage utilisation rising to a massive 14% increase when molasses is added to the ration at 1.1kg and 2kg respectively.
- Margin over feed costs increased by 8p per cow and 15p per cow per day respectively when molasses is included at 1.1.kg and 2kg addition to the ration.
- Lower inclusion of expensive proteins (Hipro Soya) in ration when molasses is included.
- More stable blood urea and ammonia levels should promote better health and fertility in livestock.
* Biosimetrics, Peter Wilson Building, West Mains Road, Edinburgh EH9 3JG
