TECHNICAL ARTICLES Beef

Quality Roughage: The challenge with hidden benefits

The continuing squeeze on profit margins of dairy producers warrants a closer look at areas of potential efficiency improvement. One such an area is the roughage content and composition of diets for dairy cows. When nutritionists and dairy producers are asked to identify major factors that limit milk production in thier herds, they often indicate roughage quality as the single most important element. Generally the uncertainty about roughage quality refers to substandard or inconsisyent nutrient compostion.

Typically the roughage component, on a dry matter basis, constitutes 30 to 40% of a total mixed ration (TMR) for high producing cows. The forage portion is not only responsible to maintain rumen health, but contributes significcantly to the total energy, protein, fibre and mineral concentration of the diet. The nutrient concentration and digestibility of the roughage component determine the actual quantity of nutrients available for absorption from a substantial portion of the diet. It also has an impact on the ruminal and intestinal flow rates and thus influences voluntary feed intake and milk production potential.

Although the importance of forage quality is appreciated by South African dairymen, more focus and commitment should be placed on the timeous assessment of roughage quality to improve the efficiency of milk production. The perception that poor quality roughages can be ‘corrected’ by a fancy formula and a better quality concentrate is still common, but not entirely true. Even if this was the case, the cost of correcting a 40% error in the diet will be excessive and dilute profitability. The effect of poor quality lucerne on milk production is clearly illustrated in Table 1.

Table 1: The effect of lucerne growth stage on the production of 4% fat corrected milk by dairy cows

Lucerne growth stage Milk Production
Forage: Concentrate = 46:54
Pre-bloom 39.6
Early bloom 35.0
Late bloom 29.4

Silages are also widely used roughage sources with a very inconsistent moisture and nutrient composition. To maintain a constant dry matter intake of silage when the moisture content of the silage increases from 65 to 70% will require additional 2.9kg silage per cow per day on an as-fed basis (Table 2).

Table 2: The effect of moisture content in silage on as-fed daily allocation

% Dry Matter Kg As-fed Kg Dry Matter
30 20.0 6
35 17.1 6

The actual type of grain and cu ltivar that will be ensiled also play an important part in the final nutritive value and performance of t he cows. Different barley cultivars that were ensiled and fed to dairy cows at sim ilar intake levels have shown that the production of 4% fat corrected milk varied fr om 31.4 kg to 34.1 kg per day. Cutting stage is another critical fact or that affects milk yield of dairy cows on silage based diets. Energy corrected milk decreased fr om 31 kg/day to 28.2 kg/day for barley silage that was harvested in the headi ng stage vs. the ear ly dough stage.

Clearly roughage quality has a significant impact on milk yield and composition and purchase agreements must be considered ca refully to ensure the required nutrient profile is acquired to achieve optimum milk production efficiency. Although resources to accurately predict the nutri ent composition of roughages and silages exist, the means to achieve greater access to dairy farmers and timely incorporation of nutrient variation into formula adjustments and feeding recommendations are not yet utilised widely enough. Near Infrared Spectrophotometry (NIR) technology can be a great help in quickly and accurately pr edicting the nutrient composition of raw materials. Please contact your nearest Meadow Feeds feed mill or technical adviser to be of assistance in the assessment of the roughage component in your dairy rations.

Date published: 2011-01-31

Author:
Joubert Naude

Publication: N/A