Whats in a bag of feed?

WHAT IS IN A BAG OF FEED?

(Nutritional Terms explained)

Examining the label of a bag of feed or reading an article on nutrition can be a daunting experience. I will try and explain the terms found on a feed bag in order to try make some sense and relate this to the basic requirements of the Angora goat.

What information do feed bags/labels contain? Legislation FERTILIZERS, FARM FEEDS, AGRICULTURAL REMEDIES AND STOCK REMEDIES ACT, 1947 (ACT NO. 36 OF 1947) indicate label particulars which include:

• Crude protein (minimum)
• Equivalent crude protein from (NPN) non-protein nitrogen (maximum)
• Amino acids (minimum)
• Moisture (maximum)
• Crude fat (minimum and/or maximum)
• Crude fiber (minimum and/or maximum)
• Calcium (minimum and/or maximum)
• Phosphorus (minimum)
• Other mineral guarantees, Vitamins (minimum)

Examples of feeds and their contents/labels

The feed label will have a list of ingredients and a guaranteed analysis of the contents.

To makes things as simple as possible I will discuss the basic requirements of the Angora goat in terms of:

1. PROTEIN
2. ENERGY
3. MINERALS and VITAMINS

For those that are interested I will then discuss the detailed contents and terminology of the label of a bag of feed.

1. PROTEIN:

The protein content in a feed is often expressed as a %  or as g/Kg.  The % is the same a g/100g so a feed with Protein content of 15% equates to 150g protein/kg feed.

The protein requirements of the Angora goat vary according to its weight and reproductive status.

For autumn-mated ewes, late pregnancy and lactation normally coincides with a period when the quality of the natural grazing is very low (late winter and early spring in the summer rainfall areas. Protein is the first limiting nutrient for ruminants during winter season (Allen et al.) and therefore attention needs to be given to supplementing sufficient protein to uphold the functions of the late pregnancy and lactation phases.

2. ENERGY:

Experiments have determined the energy requirements Angora goats require for maintenance. The practical importance of energy requirements applies mostly to non-grazing systems such as feeding schemes in kraals or to overcome serious droughts. Under drought conditions a maintenance ration is usually fed just to keep the goats alive.

However the nutritional requirements from day 90 of the pregnant Angora ewe are significantly higher. Effects of inadequate nutrition during late gestation include:

(i) Abortion after day 90 of pregnancy (ii)   Poor lactation (udder formation, low colostrum and milk production) (iii) Low birth weight (iv)  Poor mothering instincts

The nutritional requirements of the ewe are increased considerably, and energy supplementation must be increased accordingly. Trials were performed to determine blood glucose concentration in 20 pregnant ewes receiving a high and low plane of nutrition during the fourth month of gestation (Wentzel, Le Roux and Botha). They concluded a drop in blood glucose levels due to nutritional stress to be the likely trigger for the onset of hormonal changes related to abortion in Angora goat ewes. In addition, the stress of sub-nutrition during the experimental period increased the incidence of perinatal mortality.

Most feeds will have a Metabolizable Energy (ME) value. Metabolizable Energy” (ME) is an estimate of the energy available to an animal from digestion of a feed material. Energy is measured in Joules and energy value of feeds should be expressed in MJ/Kg (MegaJoule per kilogram of feed)

What amount of Metabolizable Energy (ME) does an Angora goat need to survive?

TABLE  Maintenance energy requirements of Angora goats (keep alive) MJ/day

(M.J. HERSELMAN and W.A. SMITH)

3. MINERALS and VITAMINS

Also see article:

https://www.angoras.co.za/page/vitamin-and-mineral-supplements-requirements-for-angora-goats#122

Recommended levels in Angora goats diets on a Dry Matter (DM) basis

WHAT DO SOME OF THE OTHER TERMS USED ON THE FEED LABEL MEAN?

Laboratory analyses of the composition of feed or forage are used to assess their nutritive value.

• Crude Protein (CP) “Crude protein” is actually a chemical analysis of the food whereby the amount of nitrogen present is used to estimate the amount of protein in the food. While nitrogen does come from animal protein, it also comes from non-animal proteins like grains, as well as other non-protein nitrogen (NPN)

The crude protein content of a feed sample represents the total nitrogen (N) in the diet, which includes not only true protein but also non-protein nitrogen NPN. Because N is an integral part of any amino acid, non-protein nitrogen has the potential to be utilized for protein synthesis by rumen microorganisms.

• Non-protein Nitrogen (NPN) All proteins contain on average 16% Nitrogen (N) whereas urea contains 45% N. In order for it to be utilized by the rumen microbes it must first be chemically combined with water to form CO2 and ammonia. This reaction is accomplished by action of the enzyme urease derived from certain rumen microbes. Maximum amounts of this enzyme are produced at pH 6-7. For this reason carbohydrates have to be fed with urea and also provides energy for the microbes for the incorporation of NH3 (ammonia) into bacterial protein. The optimal ratio of urea: carbohydrate is 1:8. Optimal ratio of N origin should be 2/3 : 1/3 in favour of protein.

Goats should be adapted over 2-3 weeks by increasing the urea level slowly to a maximum level of level 20-25%. If they do not receive urea for a gap of 2-3 days then again an adaption period is needed. Max levels of urea tolerated by an adult Angora goat is 15g/day.

Urea is 100% rumen degradable therefore feed with caution and is highly water soluble so protect from rain.

Urea does have a negative effect on reproduction in trials conducted with Angora goats. A study to determine the effect of different levels of urea in winter supplements for late pregnant and lactating Angora ewes on reproduction, milk production, growth of lambs, as well as milk, blood, urine and rumen characteristics was conducted by J.Hoon and J. Van Rooyen. Milk production of ewes at 3 to 4 weeks after lambing did decreased with an increase in urea inclusion level, resulting in lower body weights of the 4% Urea group at 42-day age. A lower conception rate was also recorded in the next breeding season for ewes receiving higher inclusion levels of urea, indicating a possible carry-over effect from the feeding treatments applied during late pregnancy and lactation.

• Crude Fiber (CF) This is used to divide carbohydrates into digestible and indigestible fractions. When CF content is higher, the energy content of the feed is lower because crude fiber is considered indigestible. Crude fiber accounts for most of the cellulose but only a portion of the lignin and no ash, so it underestimates true fiber and is less than acid detergent fiber (ADF). Thus, CF is not a good indicator of digestibility in ruminant animals, and the use of this parameter in feeds for ruminants is declining.
• Acid Detergent Fiber (ADF) The fibrous component represents the least digestible fiber portion of forage or other roughage. This highly indigestible part of forage includes lignin, cellulose, silica and insoluble forms of nitrogen but not hemicellulose. Forages with higher ADF are lower in digestible energy than forages with lower ADF, which means that as the ADF level increases, digestible energy levels decrease. ADF is often used to calculate digestibility, total digestible nutrients (TDN).
• Fat: Chemically, fats are “triglycerides of fatty acids” that are a high-density source of energy for animals. Fat is rich in energy; it contains 2.25 to 2.8 times the energy found in carbohydrates and is highly digestible. Fat is added to rations to boost energy levels when intake may be limited due to poor animal health, less palatable feed or environmental stress. Fats are composed of building blocks called fatty acids. Fats in feed samples are typically determined through ether extraction (EE). In addition to fat, EE may solubilize some other compounds like plant pigments, esters and aldehydes. This is why the measurement of fat through EE is called crude fat. True fat can be measured by determining the content of fatty acids or it can be estimated in forages as ether extract minus one.
• Crude Fat: Crude fat is an estimate of the total fat content of feeds. The crude fat is estimated using ether extraction. Crude fat contains true fat (triglycerides) as well as alcohols, waxes, terpenes, steroids, pigments, ester, aldehydes and other lipids.
• Dry Matter (DM): Dry matter represents everything contained in a feed sample except water; this includes protein, fiber, fat, minerals, etc. In practice, it is the total weight of feed minus the weight of water in the feed, expressed as a percentage. It is determined by drying the feed sample in an oven until the sample reaches a stable weight.
• Neutral Detergent Fiber (NDF): NDF concentration is negatively correlated with dry matter intake (i.e., as NDF in the forage increases, animals will consume less forage). As a result, NDF is often used in formulas to predict the dry matter intake. The NDF is considered a close estimate of the total fiber constituents of feedstuffs since it measures cellulose, hemicellulose, lignin, silica, tannins and cutins. Because they give the plant rigidity and enable it to support it as it grows, these three components are classified as structural carbohydrates. Though lignin is indigestible, hemicellulose and cellulose can be (in varying degrees) digested by microorganisms in animals with a rumen.
• Non-structural Carbohydrate (NSC): NSCs are simple carbohydrates, such as starches and sugars, stored inside the cell that can be rapidly and easily digested by the animal. Hence, NSC is considered to serve as a readily available energy source.
• Rumen Degradable Protein (RDP): RDP is also known as Degradable Intake Protein (DIP). The DIP or (RDP) represents the portion of crude protein (CP) that can be digested or degraded to ammonia and amino acids in the rumen by microbes. This fraction of CP consists of non-protein nitrogen (e.g., urea and ammonia in treated silage) plus the true proteins that are soluble and those having intermediate ruminal degradability. They are used to synthesize microbial protein in the rumen. The RDP or DIP is expressed as a percentage of CP
• Non degradable protein (NDP) or Undigestable Intake Protein UIP is or also called by-pass protein, escape protein or Rumen Undegradable Protein (RUP). Refers to material that is not degraded in the rumen but is degraded in the abomasum and thus is not truly “undegradable.” By-pass Protein is the portion of intake protein that has a slow rate of degradability in the rumen. It is fed so that it may escape digestion in the rumen, reach the lower gastrointestinal (GI) tract essentially intact and be digested directly in the small intestine as it would be in non-ruminants. This can provide a balance of amino acids unaltered by microbial digestion and synthesis. By-pass proteins contain a.a that by-pass the rumen and are absorbed further down the intestinal tract. If microbes break down the a.a in the rumen then body has to rebuild them which is a waste of energy.

Energy

Energy is not a nutrient, but rather the end product of a nutritional process of digestion, absorption and metabolism of nutrients in a feed. Nutrients able to produce energy are carbohydrates, proteins and fats. The metabolism of these is used to perform cellular functions. 

• Metabolisable Energy” (ME) is an estimate of the energy available to an animal from digestion of a feed material. Energy is measured in Joules and energy value of feeds should be expressed in MJ/Kg (MegaJoule per kilogram of feed)

The energy that is derived by the goat from the feed (Net Energy) is not the same as was originally present in that feed (Gross energy) and hence the importance of ME. This can be explained in the following way.

The total Energy available in the food = Gross Energy (GE).

(On a dry matter basis most feeds contain about 18.4 MJ/kg)

GE (Gross Energy)              Digestible Energy (DE)                 Metabolizable Energy (ME)

                   Less  Energy lost in the FAECES (Undigetible Energy)                                                                    Less Energy lost in URINE &GAS 

ME (Metabolizable Energy)    Net Energy (NE)   Energy for Production

                  Less Energy lost as heat in the DIGESTIVE PROCESS                               Less Energy used for MAINTENANCE

• Total Digestible Nutrients (TDN): The sum of the digestible fiber, protein, lipid, and carbohydrate components of a feedstuff or diet. TDN is directly related to digestible energy.
• Digestable Energy(DE): The loss through faeces for goats is for roughages is 40-50% and concentrates 20-30%. This is where the digestibility of feeds is important.
• Gross Energy (GE). On a dry matter basis most feeds contain about 18.4 MJ/kg.
• Net Energy (NE): Net energy refers to the amount of feed energy actually available for animal maintenance, growth and production.

More information on the importance of Angora goat nutrition can be obtained from the following:

1. Creep feeding:

https://www.angoras.co.za/page/licks_lekke#106

2. Weaning to First mating (target : 28-30kg mass 90% adult mass)

This requires an average daily growth rate of about 35g a day.

https://www.angoras.co.za/page/weaning_and_the_first_18_months#46

3. Flush feeding Ram/Ewe

https://www.angoras.co.za/page/flush_feeding#42

4. Preganant and Lactating ewe

https://www.angoras.co.za/page/pregnant_and_lactating_ewe#47

5. Drought - keeping Angora goats alive.
6. Angora goats on lucern

https://www.angoras.co.za/page/angora_goats_on_lucerne#108

7. Lucern Hay

https://www.angoras.co.za/page/lucerne_hay#100

8. Vitamins and minerals

https://www.angoras.co.za/page/vitamin-and-mineral-supplements-requirements-for-angora-goats#122

References Extractions from research in these articles by:

1. D. H. van Niekerk
2. Wentzel
3. Wentzel, M.J. Herselman, P.R. King & J.J. Olivier
4. Wentzel, M. Le roux & L J J Botha
5. N.Louw & B.D.H van Niekerk
6. Snyman

J H Hoon, J N Swart and B R King

J H Hoon, M J Herselman & B R King

 J.B.J. van Ryssen and J.H. Hoon

J.H. Hoon

J.H. Hoon and M.J. Herselman

J.H. Hoon & J.A. van Rooyen

L Louw

M.J. Herselman & W.A.Smith

P G Marais

P G Marais, & J A Roux

P.B. Cronjé

P.R. King, V. Sumner, D. Wentzel, P. Schlebush and M.J. Herselman

Van Niekerk, Louw

Bath GF, Wentzel D, van Tonder EM