Great Lakes Dairy Sheep Symposium - the Department of Animal ...

Practical Recommendations
A visual method to estimate pasture quality and herbage intake
Table 16 reports a pasture classification based on characteristics observable by visual
inspection. This classification (Avondo, 2005) has been developed on the basis of herbage intake
and crude protein content of the selected diets of lactating ewes in conditions where the height
and density of herbage, the biomass, the biological stage, and the pasture heterogeneity vary. All
these variables in combination can provide highly valid information on whether the pasture is
usable.
Pasture intake is the result of interaction between the animal and the herbage at its
disposal. The different types of pasture in the table offer the animal different feeding
possibilities. On pasture type 1 (and to a lesser extent on pasture type 2), young and compact
herbage allows the sheep to take large bites that are easy to chew and taste good. On pastures
type 3 and 4, because some of the herbage lignified, the animal takes small bites after having
first identified the most tender parts. This selective activity significantly improves the qualitative
characteristics of the diet compared to the values for available herbage, and is associated with a
notable reduction in dry matter intake with respect to better types of pasture. The animal nearly
always selects matter that is richer in protein. This must be taken into consideration when
formulating feed supplements. Indeed, when pasture quality is mediocre, a high protein
supplement is often administered (supplements up to 20% of crude protein), without considering
that it is exactly in these herbage conditions that there is more selection of higher protein parts of
herbage. This allows the sheep to intake significantly better diets than would be expected.
Table 17, referring to the empirical classification in Table 16, reports the mean expected
intake for each pasture typology, with different supplement levels, for a lactating ewe producing
3 l/d and weighing 60 kg. The same table also indicates the percentage increases expected in the
protein content of the selected diet at pasture compared to the available herbage protein content.
114