A lesson learned this week that’s for sure – not to assume that all farms are similar and have similar targets. My comment relates to planning for the end of closing in 3 weeks time and for the Spring grazing season 2010. The farm walk with the farmer, before the budgeting, allows an opportunity for a chat and to discuss tactics for the grassland management for the coming months. At this time of the year it usually includes the common assumptions that we close at approximately “500 kgDM/ha and open at 650 kgDM/ha”. On two occasions this week how wrong could we have been. Unknown to the farmers in question, breeding had went very well earlier in the year leading to an earlier than normal and compact calving pattern, and, coupled with a slight increase in cow number for next year, led to a significantly higher demand in Spring than anticipated. All this meant that target opening cover on both of these farms was circa 770 kgDM/ha as opposed to 650 kgDM/ha. Accordingly closing cover for this year was increased to 600 kgDM/ha. The consequences of going with the out initial assumption would have been that large amounts of concentrates would have to be fed in Spring to slow and expected rapid decline in farm cover to magic day - bottom line was that measurement and budgeting now saved money!
Grazing conditions in the past week have deteriorated considerably. Obviously not desirable, but for some, causing more problems than others. Graze out of paddocks is suffering especially with pre-grazing yields of >2000 kgDM/ha. In this case it is essential to stimulate appetite by keeping the cows in after milking for 2-3 hours – one they go out they are focussed on satisfying their appetite and grazing down through the sward. On wet soils this must be taken a step further with on/off grazing.
Another very topical issue for the coming weeks – relates to the changes in protein in the diet with increasing levels of silage in the diet. Grass and silage protein levels are set and reports are that silage protein levels are low this year, so what type of concentrate should I be feeding to balance the protein in the diet?
Considering a typical milk yield at present of circa 13 litres/day and 15kg DM intake, it is suggested that crude protein percentage in the total diet should be circa 14%. Therefore protein intake should amount to 2100g/day. To elaborate on this I will use two scenarios:
1 – High Grass/Low Silage in the diet Protein Supply
Grass – 10kgDM intake @ 18% Protein 1800g
Silage – 2kgDM intake @ 10% Protein 200g
Concentrate (Citrus) – 3kg intake @ 10% Protein 300g
Total Protein intake 2300g/day
2 – Low Grass/High Silage in the diet Proetin Supply
Grass – 6kgDM intake @ 18% Protein 1080g
Silage – 6kgDM intake @ 10% Protein 600g
Concentrate (Citrus) – 3kg intake @ 10% Protein 300g
Total Protein intake 1980g/day
As you can see scenario number 2 is deficient in the amount of protein supplied in the diet. If the amount of grass in the diet can not be increased then the % crude protein of concentrate must increase – i.e change or adjust concentrate. So, again consider scenario 2 above:
Requirement: 2100g Protein per day
Provided by: Grass (6kgDM) 1080g & Silage (6kgDM) 600g
Shortfall of Protein to be supplied by concentrate: 2100–1680 = 420g
If 3kg concentrate is to be fed then what % protein must it contain: 420g/3000g = 0.14 = 14%
So using this scenario, the concentrate being fed must be balanced to amount to 14% crude protein. Proetin sources are expensive but there are a number of them available, e.g Gluten (≈20%), Distillers (≈ 25%), Rapeseed Meal (≈30%), however the latter two have intake limitations. Why not mix components? In the example above 3kgs concentrate made up of 2kg citrus and 1 kg gluten suffices to account for the protein requirements in the diet.
I can not finish without coming back to Scenario 1 above. It must be clear that, at this time of the year grass has a high crude protein level. Bottom line, if you make provision for and maintain high levels of grazed grass in the diet you will more than satisfy crude protein requirements in the diet and alleviate the necessity of expensive alternatives.
