Pasture Management
Introduction
Beef Cattle
Beef cattle which have been adapted to dry lot feeds do not have the necessary ruminal microflora to utilize very high nutrient levels in pasture.
When they are turned onto spring pasture, they are for a brief period of time placed in metabolic distress which causes poor coronary band function.
As a result, grooves form in the walls of the claws from which sandcracks may develop.
Similar pathological changes can occur as the result of sudden alterations in the quality of the pasture consumed caused by good growing weather or rotational grazing.
Dairy Cattle
Fewer and fewer dairy cows or heifers are turned out to grass.
However, where grazing is practiced, changes in the appearance of the claws can be seen corresponding to the period when exposure to or removal from grass has taken place.
Comparable changes in the quality of nutrients occur when forage from different sources (more particularly differing in quality) are suddenly substituted.
It is highly important to test pasture samples for protein and effective fibre if there is reason to believe that lots vary in quality.
When forage is purchased it is wise to mixsome of the batch being replaced with newly imported material. Allow a ten day acclimatization period from batch to the other if possible.
Protein and Fibre in Pasture
Hay fed during the winter may have a crude protein content of from 8.5 - 15.7% and acid detergent fibre (ADF) from 27 - 43 %.
Typical nutrient levels of spring grasses range from 14-16% crude protein, 40-50% neutral detergent fibre (NDF) and 25-35% ADF.
Nitrogen fertilization can routinely enhance the crude protein to 30% and depress the ADF to 20%.
Sudden jumps in protein levels and drop in ADF will occur about ten days after the commencement of a period of warm wet weather.
Irrigation, particularly of fall aftermath pastures, can cause a sudden dramatic alteration in the nutritional quality of the pasture.
Rotational grazing will lead to sudden jumps in pasture quality if the plots are too heavily stocked.
Recommendations
- Meet the nutritional needs of the animals throughout the season to reduce predisposition.
- Fall management to enhance residue on pasture. Reduce late summer/fall grazing on pastures that will be used early in the spring to increase fibre content in the diet. Rational and complementary grazing systems enable this approach.
- Reduce spring use of fertilized pastures. Deferr grazing of fertilized pastures to allow for increased fibre and reduced nutrient concentrations.
- Delay/deferr spring turn out. Where economically feasible, animals should be retained on dry lot, however, this option must include increased summer pasture utilization to offset the economics.
- Earlier spring turn out. The development of a sacrifice pasture that permits continued dry feeding as the animals adjust to the emerging pastures.
- Hay/straw/silage feeding on spring pasture. Withdraw access to mineral
mix and dress forage with salt to increase palatability. Continue availability
of dry feeds over the first three weeks of pasturing to enable higher
fibre levels, and dilute the high nutrient levels found in spring pasture.
Discussion
If obvious grooves are present in the walls of the claws of cows, it is a certain indication that some change in the metabolism of the animal has occurred.
If all the cows have a groove in the same place, then something is causing this to happen at the same time.
Calculate the date of the cause for the change and investigate nutritional and environmental events that took place at this time.
If a herd has a lameness problem, it is essential to monitor the analysis of the forage or pasture consumed by the animals.
Changes in the quality of the effective fibre is a likely cause.
If there is any reason to believe that micronutrients are deficient, samples of feed should also be monitored for trace elements.
