Feed Quality

Feed Quality

Deer need good quality feed to perform.  The quality of the feed available is made up of plant components (ME, protein, fibre) and pasture components (species, age, legume content, stem and dead material etc.). The diet selection and seasonal variation in appetite of deer are also important.

A lower energy requirement in winter can be met by a diet of lower feed quality, likely to be more grass or brassica than legume. The intake of deer rise rapidly in spring and the opportunity is to provide enough feed of high quality to capture the liveweight gain (productivity) benefits.

An example of the theoretical liveweight gain profiles of young red deer stags on pastures of different quality from the QGraze software

An example of the theoretical liveweight gain profiles of young red deer stags on pastures of different quality from the QGraze software.

 

Guide to Feed Quality

Farmers and consultants often send off a sample of silage or pasture to see what is in it, but what do the figures mean when we get the test back? The notes in the fact sheet below will help you take make sense of the test results and allow you to judge the quality of the feed you have or are about to buy.  By Dr David Stevens, AgResearch  The following is taken from a Focus on Deer – After the Field Day fact sheet.

What is on the test sheet?

  • Reference range
  • Nutrient contents (expressed as %; g/100g or g/kg)
  • Fermentation indicators (on silage test samples)

What to ignore:

  • Reference range

We usually look at the reference range to see if our feed sits on the “normal” or “medium” range. However, these ranges are not about nutritive value. Instead they refer to the typical sample measured by the lab, not about how the feed meets the requirements of your animals. If you are in the normal range then your sample is similar to a lot of others that have been through that lab.

  • Nutrient content

There are many components of the feed and each has its own specific trait in determining animal performance. Some are directly related to performance (protein and energy), while others are indirectly related, (Acid Detergent Fibre (ADF) and Neutral Detergent Fibre (NDF)). The concentration of these nutrients needs to be different for different livestock classes at different times. For example, animals at maintenance will need a lower protein content, and will get by with lower energy content.

 

Components of the feed

Dry Matter (DM) often expressed as % or g/100g, is most important when considering silage, or when you want to work out how much to feed, as all the nutrients are in the dry matter.  As a working example—a silage with a dry matter of 25%. This means a 120kg hind at maintenance requirement of 2kgDM will need 2/0.25 = 8 kg of wet silage per day.  Dry matter may also help when estimating how palatable a silage will be as very dry (>80%) or very wet (<20%) silages will be less palatable. 

Crude protein (CP) usually expressed as g/kg or g/100g:  Deer Requirements: These values should be increased by at least 2% if high quantities of silage are used in the diet (>50%).

Maintenance 10-12%
Growth 14-16%
Pregnancy 14-16%
Lactation 16-18%
Velvet 16-18%
Spike Initiation 18-20%

 Metabolisable Energy (ME) usually expressed as MJ/kg – this indicates the potential animal performance that might be expected on the feed:

Maintenance  8-9 MJ/kg DM
Some growth/pregnancy  9-10.5 MJ/kg DM
Reasonable growth/lactation  10.5-12 MJ/kg DM
High growth/good lactation   >12 MJ/kg DM

This range may vary depending on feed type – the range above applies to silage, pasture, and other forages and forage supplements like hay.  Supplements like grain or maize silage, may provide higher performance at lower ME (usually provide good growth and lactation performance at >10.5 MJME/kg). When feeding a high ME diet to animals that are on maintenance then the total amount of dry matter offered may be decreased.

 

What some of the components mean

ME – Metabolisable Energy - It is an estimate of the energy available to an animal from digestion of a feed material, expressed in units of megaJoules per kilogram of feed (MJ/kg DM).

ADF – Acid Detergent Fibre.  (g/kg) g/100g need for a healthy rumen and good digestion. This provides an estimate of the relatively indigestible fibre and should be a minimum of 18 grams or 80g/kg and preferably over 20 for rumen health. Maximum animal performance occurs when the diet has between 20-25% (g/100g) ADF.

NDF Neutral Detergent Fibre - This provides an indicator of how quickly the feed might be digested. Maximum performance is often achieved at 35% and intake progressively declines as NDF increases. Once NDF is over 45% the feed is usually not suitable for lactation and growth will be moderate. Over 55% the feed is only suited to maintenance. The value of NDF will often follow the opposite trend to ME.

pH – Only recorded in preserved feeds like silage and indicates how well preserved the feed is. Silage pH should sit between 4.2 and 4.8 indicating good fermentation and palatability Silages below pH 4 may have low intake. Silages above pH 5.0 may be less stable when exposed to air, or may have higher incidence of harmful bacteria – potentially causing animal health issues like listeriosis.

Lactate/lactic acid – another preservation indicator

Ammonia-N-     Usually indicated as ppm or % of total N and is an indicator of loss of protein from the original feed. High levels indicate significant degradation of the protein and feeds may require extra protein if the CP is also low. Also an indicator of potential palatability – high values lower feed intake.

Butyrate/butyric acid (g/100g or ppm) is an indicator of poor fermentation - it usually indicates a slower fermentation which can influence the protein availability. The silage may smell bad, when butyrate is high and feed intake will be low.

Most of the other components on a feed test have little relevance to helping meet your animals’ requirements.

 

 Explaining maintenance requirements and costs

  • Animals require a certain amount of nutrients to maintain themselves.
  • Generally ruminants need about 10-12% of their diet as protein.
  • Energy requirements are a little more complex as they vary based mostly on surface area to volume ratio, rather than size or weight in totals.
  • Energy is required for core processes such as replacing worn out tissue, but also for staying warm, exercise (walking, standing, running etc) and for keeping pathogens at bay.

Up to half of the core or basal maintenance cost may be due to maintaining the immune functions of the animal.  Maintenance then increases when:

  • it is cold or wet
  • it is hilly
  • where the animal is nervous and paces a lot
  • when it is presented with a new or heightened attack on its immune system, e.g. parasites in the diet, facial eczema, Johne’s

In the last example – immune challenge – the animal also needs more protein as well as more energy, because proteins are needed to make the agents, such as immunoglobulin, that fight the challenge.  A significant challenge could add 50% to the maintenance requirement. This then means that energy and protein are diverted from things like growth or lactation.