URGENT NEWS. Grass Silage Update No 144: Grass Silage Update /2011. Fermentation quality and intake characteristics

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1 1 of 6 Grass Silage Update Nature is such a great leveler. The early fears of winter forage shortages have gone on most farms but so too have the hopes of the highest quality grass silage crop for many years. The average results of the analyses of over 5000 clamped grass silages show generally good, but not vintage, quality. In fact the average grass silage is decidedly average marginally better than the past 2 years but equivalent to the 10 year average. Consequently, there is limited scope to reduce concentrate feeding with this year s average grass silage. The results of all clamp grass silages, further divided into first and second cut are given in the attached tables. Dry matter and energy Grass silages are higher in dry matter than last year averaging 32.8%, which is 1% above last year and indeed 2% higher than the 10 year average (from 2000). Forty percent of the grass silages so far analysed have an ME of 11 MJ/kg DM or more. On average. the energy content of 10.8 MJ/kg DM for all silages is 0.2 MJ/kg DM above , although only 0.1 MJ/kg DM above the 10 year average which itself ranges from 10.4 to 11.2 MJ/kg DM. Closer consideration of first and second cut silages shows a higher energy first cut compared to last year (10.9 vs 10.6 MJ/kg DM) but no difference in second cuts (10.5 MJ/kg DM). Since later cuts have been taken on many farms this summer, the overall average energy content may yet decline still further. Based on the average energy content to date and a dry matter intake of 10kg, grass silage will supply approximately M+5 litres. An extra 2MJ per day can be obtained from this year s average grass silage compared to , equivalent to less than 0.5 litre of milk. Alternatively a potential saving of only 0.18 kg of concentrate per day may be possible to achieve the same milk yield, equivalent to approximately 8 per cow over a 200 day winter. Fermentation quality and intake characteristics The average crop is well preserved (based on ph, ammonia-nitrogen, lactic acid and VFA content) with good intake potential (100 g/kg 0.75 ). It will feed well. Some 10% of forages are not well made, having a ph of 4.5 or more, and are therefore prone to extensive secondary fermentation. These silages can induce heating in mixed diets, resulting in reduced ration dry matter intakes and increased wastage. This could be a serious issue, especially on those farms where forages are in short supply. Urgent News 142 previously identified this problem and provides a control measure using Selko TMR. In contrast, a further 10% of this year s grass silages have a high lactic acid content of 100g/kg or more. The resultant acid load can significantly impact on rumen activity through acidosis and reduce dry matter intake. Adequate effective fibre intake is essential with these forages and rumen buffering using buffer salts and yeasts are often effective in these situations.

2 2 of 6 Fibre The average NDF content of all clamp silages is lower this year than (48.1 vs 49.7%). Whilst this lower NDF value is reflected in the higher average energy content it is important to note that the correlation between ME and NDF has an r 2 of only 0.3. See graphs over page. Clearly, there are other components which influence the D value of forage. For example, lignin (a component of NDF and ADF) binds to fibre, reducing digestibility. This year, for increased accuracy in the Rumenac system, we have been measuring the lignin content which averages 4.3% and ranges from 2.4 to 7.0%. Examination of the data shows good, but not surprising, correlation of increasing lignin reducing ME (r 2 of 0.52). It is clear, therefore, that grass silages can have a low NDF and low ME value if the lignin content is high. Examples this year include a grass silage with an NDF of 40.7%, ME of 12.0 MJ/kg DM and a lignin of only 2.39%; in contrast, another had a similar NDF of 40%, but an ME of only 10.5 MJ/kg DM due to a lignin content of 5.66%. Clearly, the lignin content can be very useful in helping to explain unexpected results. As in previous years, care must be taken to ensure adequate effective fibre intake balanced against fermentable carbohydrate supply, to maintain healthy rumen conditions, especially where high acid load silages are being fed. Protein Crude protein (13.5%) and metabolisable protein values (MPB, MPN, MPE) are comparable to last year. As always, the balance of rumen nitrogen and energy supply in the total ration is important to dairy cow performance, health and fertility. Research has shown that an excess of rumen nitrogen of 500g per day requires energy to deaminate and excrete equivalent to 1.3 litres of milk. An intake of 10kg DM of this years average grass silage will have an excess MNP to MPE of 148g per da, thereby supplying 50% of the maximum total diet excess target of 300g per day. Careful consideration the concentrate input is important to balance the daily nutrient supply. Vitamin E The average estimated content of vitamin E in grass silage of 30 mg/kg DM is typical. It is important to note that a daily intake of 10kg DM of this silage will supply only 300mg of vitamin E compared to the advised requirement published in NRC Dairy (2001) of 2.8mg/ kg body weight, or 1820mg per day for a 650kg cow. To balance this shortfall in, for example, a TMR, a mineral fed at 250g per cow per day should contain at least 5000 mg vitamin E per kg. In summary Averages form an interesting basis for comparison, but attention to detail on each individual farm is critical to maximizing profitability. With the spread in cutting dates and the quantity of later cut silages taken this year, it is essential to test the silage clamp regularly through the winter to identify and react to changes before they impact on performance. Further information can be obtained from the Frank Wright Trouw technical department on Receive these technical publications directly via link. Contact Sarah Brandrick to register your interest on or at sarah.brandrick@frankwright. com. You can also access this and past CONTACT and URGENT NEWS publications by registering on our website:

3 3 of 6 Clamp Grass Silage to y = x R 2 = ME MJ/kgDM NDF % 13 Clamp Grass Silage to R 2 = ME MJ/kg DM Lignin %

4 4 of 6 Average Grass Silage Analyses Min Max Dry Matter % Crude Protein % D Value % ME MJ ph NH3N % Sugar % Ash % NDF % ADF % Oil % VFA g/kg Lactic Acid g/kg Vitamin E mg/kg Intake Potential g/kg PAL meq/kg RSV MPB g/kg MPN g/kg MPE g/kg

5 5 of 6 Average 1st Cut Grass Silage Analyses Min Max Dry Matter % Crude Protein % D Value % ME MJ ph NH3N % Sugar % Ash % NDF % ADF % Oil % VFA g/kg Lactic Acid g/kg Vitamin E mg/kg Intake Potential g/kg PAL meq/kg RSV MPB g/kg MPN g/kg MPE g/kg

6 6 of 6 Average 2nd Cut Grass Silage Analyses Min Max Dry Matter % Crude Protein % D Value % ME MJ ph NH3N % Sugar % Ash % NDF % ADF % Oil % VFA g/kg Lactic Acid g/kg Vitamin E mg/kg Intake Potential g/kg PAL meq/kg RSV MPB g/kg MPN g/kg MPE g/kg