Animal Husbandry and Fisheries Assistant · Chapter 2

Feeds and Fodder

What to remember

Feeds are roughages (more than 18 % crude fibre, low energy) or concentrates (less than 18 % crude fibre, rich in energy or protein). Roughages are green fodder, dry fodder, hay and silage.
Nutrient terms: crude protein (CP) = nitrogen x 6.25; digestible crude protein (DCP) and total digestible nutrients (TDN) show what the animal can actually use. Nutritive ratio (NR) = (TDN - DCP) / DCP.
Good silage is made from maize or sorghum at the milky-dough stage, packed tightly and sealed to keep out air; good hay is cut at early flowering and dried to about 15 to 20 % moisture.

Nutrients and proximate analysis

A feed contains water and dry matter (DM). The dry matter carries organic nutrients (protein, fat, carbohydrate, vitamins) and minerals (ash).

Proximate analysis divides a feed into six parts:

Fraction	How it is found	Note
Moisture	Drying at 100 to 105 °C	Dry matter = 100 - moisture
Crude protein	Kjeldahl nitrogen x 6.25	Protein is about 16 % nitrogen
Ether extract (EE)	Extraction with ether	Fats and oils
Crude fibre (CF)	Boiling in acid and alkali	Cellulose, hemicellulose, lignin
Total ash	Burning at about 550 °C	Minerals
Nitrogen-free extract (NFE)	By difference: 100 - (moisture + CP + EE + CF + ash)	Starch and sugars

Energy value: TDN = DCP + CF digested + NFE digested + 2.25 x EE digested. Fat gives 2.25 times the energy of carbohydrate.
Nutritive ratio: NR = (TDN - DCP) / DCP. A narrow ratio (such as 1:4) means high protein; a wide ratio (such as 1:10) means low protein.
Starch equivalent and metabolisable energy (ME) are other ways to express energy.
Mineral needs: calcium and phosphorus should be in the ratio of about 2:1 in the ration. Salt (sodium chloride) is provided free choice or mixed in feed. Mineral mixture is added to the concentrate at about 1 to 2 %.
Vitamins: green fodder gives carotene (vitamin A source). Sun-cured hay gives vitamin D. Rumen microbes make B vitamins and vitamin K in adult ruminants.
Water: the most important nutrient. Dairy animals need a free supply of clean water, and milk is about 87 % water.

Roughages: green fodder, hay and silage

Green fodder crops

Group	Examples	Remarks
Legumes	Lucerne (alfalfa), berseem, cowpea, stylo (Stylosanthes), Desmanthus, subabul (Leucaena)	Rich in protein and calcium; fix nitrogen; may cause bloat if fed wet and in large amounts
Cereal fodder	Maize, sorghum, bajra (pearl millet), oats	High in energy; sorghum young plants may contain hydrocyanic acid (HCN)
Grasses	Hybrid Napier (Bajra-Napier hybrid), guinea grass, para grass, Cenchrus, Dichanthium	Perennial grasses give many cuts

Berseem is a winter legume; lucerne is the "queen of fodder crops" and is perennial.
Hybrid Napier gives very high green fodder yield from slips (stem cuttings).
Subabul (Leucaena) is a fodder tree whose leaves are rich in protein. It contains mimosine, a toxin that causes hair loss and goitre when fed in large quantity.
Azolla is a floating water fern with high protein; it is a cheap supplement for dairy animals and poultry.
Sorghum: do not feed before 45 days or when stunted, because the HCN (dhurrin) content is high. Feeding after flowering is safe.
Fodder sources in AP also include crop residues such as paddy straw, groundnut haulms and sorghum stover, which are used as dry fodder.

Hay is green fodder dried to 15 to 20 % moisture. Cut grasses at early flowering; legumes at 10 % bloom. Turn the cut crop to dry quickly in the sun so that colour and leaves are kept. Overdrying shatters the leaves, which are the best part.

Silage is green fodder preserved in moist condition by lactic-acid fermentation in the absence of air (ensiling).

Moisture at ensiling should be about 65 to 70 %. Crops with 30 to 35 % dry matter are best.
Crops: maize, sorghum and hybrid Napier. Legumes alone ensile poorly because they are low in sugar and resist a fall in pH; add molasses (2 to 3 %) to improve them.
Stage of cutting: maize at milky-dough stage.
Process: chop to 2 to 3 cm, fill and press hard into a silo (pit, trench or tower), seal with polythene and soil.
Good silage: pH about 4.2, pleasant smell like fruit or pickle, green-yellow colour. Bad silage smells of rancid butter and has pH above 5.
Silage is ready in about 45 to 60 days.

Concentrates and feed additives

Energy concentrates: cereal grains (maize, sorghum, ragi), broken rice, wheat bran, rice polish, molasses.
Protein concentrates: oilseed cakes (groundnut cake, cottonseed cake, soybean meal, sunflower cake, coconut cake), pulse chunnies, fish meal, meat meal.
Brans: wheat bran, rice bran, deoiled rice bran.
Anti-nutritional factors

Feed	Toxic factor	Effect
Groundnut cake (spoiled)	Aflatoxin from Aspergillus flavus	Liver damage, cancer, aflatoxin in milk (M1)
Cottonseed cake	Gossypol	Reduced fertility, toxic to young calves and pigs
Subabul	Mimosine	Hair loss, goitre
Young sorghum	HCN (dhurrin)	Rapid breathing, sudden death
Soybean raw	Trypsin inhibitor	Poor protein use; heat treatment destroys it
Linseed	HCN glycoside	Safe when cooked
Mustard cake	Glucosinolates	Thyroid effects
Oxalate plants	Oxalic acid	Calcium loss

Urea is a non-protein nitrogen (NPN) source. Rumen bacteria turn it into microbial protein. Feed up to 1 % of the concentrate mixture or up to about one-third of the protein need. Never feed to calves or monogastrics, and never in one big dose. Toxic signs: bloat, trembling, frothing.
Urea treatment of paddy straw: 4 kg urea dissolved in 50 to 60 litres of water is sprinkled on 100 kg straw, which is then covered for 2 to 3 weeks. The treated straw has more crude protein and better digestibility.
Molasses is a cheap energy source. It is fed up to about 10 to 15 % of the ration. Urea-molasses mineral block (UMMB) is a lick block.
Complete ration or total mixed ration (TMR) mixes roughage and concentrate in one feed.
Bypass protein is a protein which escapes breakdown in the rumen and is digested in the intestine; it helps high yielding cows. Heat or formaldehyde treated cake provides this.
Probiotics, buffers (sodium bicarbonate) and yeast are used as additives. Ionophores such as monensin improve feed efficiency.

Digestion and feeding practice

A ruminant has four stomach compartments: rumen, reticulum, omasum, abomasum (true stomach). The rumen is the largest. Bacteria, protozoa and fungi in the rumen digest fibre.
Volatile fatty acids (VFA): acetic, propionic and butyric acid. Acetic acid is the main precursor of milk fat; propionic acid helps glucose supply. High grain diets lower rumen pH and cause acidosis.
Calves: colostrum within 1 to 2 hours of birth, about 10 % of body weight per day of milk for the first weeks; calf starter and good-quality green fodder from the second week; weaning at about 8 to 12 weeks.
Daily requirements for adult cattle (thumb rules):
Dry matter intake about 2.5 to 3 % of body weight.
Maintenance concentrate about 1 to 1.5 kg for an adult cow.
Production: 1 kg of concentrate for every 2.5 litres of cow milk and 1 kg for every 2 litres of buffalo milk (when quality green fodder is available, less concentrate is needed).
Green fodder about 25 to 30 kg per adult cow per day; roughage should be at least one-third dry for rumen health.
Mineral mixture 30 to 50 g daily; common salt 30 g.
Feed in two to three meals; change feed gradually over 7 to 10 days. Cut green legumes should be wilted before feeding to avoid bloat.
Feed storage: keep dry and clean to avoid fungi and aflatoxin.

Worked examples

1. Fresh maize has 80 % moisture. A 1,000 kg lot has 20 % dry matter = 200 kg DM.
2. A feed has 13.2 % crude protein, so nitrogen = 13.2 / 6.25 = 2.11 %.
3. Feed analysis: moisture 10, CP 15, EE 4, CF 8, ash 6. NFE = 100 - (10 + 15 + 4 + 8 + 6) = 57 %.
4. TDN 66 and DCP 11: NR = (66 - 11) / 11 = 5:1, i.e. 1:5 (narrow).
5. A cow gives 10 litres of milk. At 1 kg concentrate per 2.5 litres, the production concentrate = 4 kg. With 1.5 kg for maintenance, total concentrate = 5.5 kg.
6. To prepare 100 kg of straw with 4 % urea: urea = 4 kg.
7. Pearson square for mixing: mix a 20 % CP feed with a 10 % CP feed to make a 16 % CP mix. Parts of 20 % feed = 16 - 10 = 6; parts of 10 % feed = 20 - 16 = 4. Ratio 6 : 4 = 3 : 2.

Exam traps

Hay vs silage: hay has 15 to 20 % moisture; silage 65 to 70 %.
Roughage vs concentrate: the dividing line is 18 % crude fibre.
Crude protein vs DCP: CP is chemical content; DCP is the digestible part.
Gossypol vs aflatoxin: gossypol is from cottonseed; aflatoxin is a fungal toxin of groundnut cake.
Mimosine vs HCN: mimosine is in subabul; HCN in young sorghum.
Urea vs bypass protein: urea is rumen NPN; bypass protein is true protein protected from rumen breakdown.
Acetic vs propionic acid: acetic acid helps milk fat; propionic acid gives glucose.
Lucerne vs berseem: lucerne is perennial; berseem is a winter annual.

One-liners

1. Crude protein = nitrogen x 6.25.
2. NFE is found by difference.
3. Nutritive ratio = (TDN - DCP) / DCP.
4. Calcium to phosphorus ratio in the ration should be about 2:1.
5. Silage moisture should be about 65 to 70 %.
6. Good silage has a pH of about 4.2.
7. Hay is dried to 15 to 20 % moisture.
8. Lucerne is called the queen of fodder crops.
9. Subabul contains mimosine.
10. Cottonseed cake contains gossypol.
11. Urea should not exceed 1 % of the concentrate mixture.
12. Colostrum should be fed within 1 to 2 hours of birth.

Practice questions

Crude protein of a feed is calculated as nitrogen content multiplied by:
1. 5.70
2. 4.25
3. 6.25
4. 8.5
Answer
C. 6.25
Protein contains about 16 % nitrogen, so CP = N x 6.25.
Feeds with more than 18 % crude fibre are classed as:
1. mineral supplements
2. concentrates
3. vitamin premixes
4. roughages
Answer
D. roughages
Roughages have more than 18 % CF; concentrates less than 18 %.
The Kjeldahl method is used to estimate:
1. total ash
2. nitrogen (crude protein)
3. ether extract
4. crude fibre
Answer
B. nitrogen (crude protein)
Kjeldahl digestion measures nitrogen.
The toxic principle in cottonseed cake is:
1. mimosine
2. aflatoxin
3. gossypol
4. oxalic acid
Answer
C. gossypol
Gossypol harms fertility and young animals.
Mimosine toxicity is associated with feeding of:
1. lucerne
2. maize
3. subabul (Leucaena)
4. berseem
Answer
C. subabul (Leucaena)
Subabul leaves contain mimosine, causing hair loss and goitre.
The fungus responsible for aflatoxin in spoiled groundnut cake is:
1. Candida albicans
2. Rhizopus nigricans
3. Penicillium notatum
4. Aspergillus flavus
Answer
D. Aspergillus flavus
Aflatoxins are produced by Aspergillus flavus.
Which of these is a perennial legume fodder called the queen of fodder crops?
1. Oats
2. Lucerne
3. Cowpea
4. Berseem
Answer
B. Lucerne
Lucerne (alfalfa) is a perennial legume.
Silage is preserved mainly by:
1. lactic acid fermentation without air
2. drying in sun
3. adding salt only
4. freezing
Answer
A. lactic acid fermentation without air
Lactic acid lowers pH and preserves the green fodder.
The ideal moisture content of hay is about:
1. 40 to 50 %
2. 15 to 20 %
3. 65 to 70 %
4. 5 %
Answer
B. 15 to 20 %
Hay is dried to 15 to 20 % moisture.
The ideal moisture content at ensiling is about:
1. 15 to 20 %
2. 30 %
3. 65 to 70 %
4. 90 %
Answer
C. 65 to 70 %
Crops with about 30 to 35 % DM make good silage.
Which volatile fatty acid is the main precursor of milk fat?
1. Lactic acid
2. Butyric acid alone as glucose source
3. Propionic acid
4. Acetic acid
Answer
D. Acetic acid
Acetic acid supplies carbon for fat synthesis in the mammary gland.
The true (glandular) stomach of a ruminant is the:
1. rumen
2. reticulum
3. omasum
4. abomasum
Answer
D. abomasum
Abomasum is the true stomach with gastric glands.
Azolla is useful in animal feeding because it is:
1. a cereal grain
2. a toxic weed
3. a protein-rich aquatic fern
4. a cellulose-free feed
Answer
C. a protein-rich aquatic fern
Azolla is a floating fern with high protein.
Which of these is a non-protein nitrogen source for ruminants?
1. Soybean meal
2. Urea
3. Groundnut cake
4. Fish meal
Answer
B. Urea
Rumen microbes convert urea nitrogen to protein.
The recommended calcium to phosphorus ratio in a dairy ration is about:
1. 2 : 1
2. 1 : 5
3. 5 : 1
4. 1 : 1 exactly in all cases
Answer
A. 2 : 1
A ratio of about 2:1 is considered satisfactory.
The nutritive ratio is calculated as:
1. DCP / TDN
2. (DCP - TDN) / TDN
3. TDN / DCP
4. (TDN - DCP) / DCP
Answer
D. (TDN - DCP) / DCP
NR = non-protein digestible nutrients to DCP.
Young sorghum plants can cause sudden death due to:
1. hydrocyanic acid (HCN)
2. gossypol
3. mimosine
4. aflatoxin
Answer
A. hydrocyanic acid (HCN)
Young or stunted sorghum contains dhurrin, which releases HCN.
Raw soybean meal is heated before feeding to destroy:
1. oxalic acid
2. trypsin inhibitor
3. mimosine
4. gossypol
Answer
B. trypsin inhibitor
Heat treatment inactivates trypsin inhibitor.
The fat in a feed has an energy value which is approximately ____ times that of carbohydrate.
1. 0.5
2. 4.0
3. 2.25
4. 1.0
Answer
C. 2.25
TDN calculation multiplies digestible EE by 2.25.
Urea should not exceed what proportion of the concentrate mixture for cattle?
1. 10 %
2. 1 %
3. 40 %
4. 25 %
Answer
B. 1 %
Excess urea causes ammonia poisoning.
Why should urea not be fed to young calves?
1. Calves are allergic to nitrogen
2. Urea is too costly
3. The rumen is not yet functional
4. Urea gives them diarrhoea only
Answer
C. The rumen is not yet functional
Urea use needs rumen microbes, which develop later.
Bypass protein is protein which:
1. is fully broken down in the rumen
2. is made by rumen microbes
3. cannot be digested
4. escapes rumen breakdown and is digested in the small intestine
Answer
D. escapes rumen breakdown and is digested in the small intestine
It supplies amino acids directly to the intestine.
A high-grain diet fed suddenly to cattle most commonly leads to:
1. rumen acidosis
2. anthrax
3. rickets
4. milk fever
Answer
A. rumen acidosis
Starch ferments rapidly and lowers rumen pH.
A silage with a pH of about 4.2 and a fruity smell indicates:
1. spoilage by Clostridia
2. too much moisture only
3. unsafe for feeding
4. good quality
Answer
D. good quality
Low pH with pleasant smell shows correct lactic fermentation.
Cut green legumes should be wilted before feeding to avoid:
1. bloat
2. poisoning by gossypol
3. milk fever
4. tetany
Answer
A. bloat
Wet legumes cause frothy bloat.
For urea treatment of straw, the urea used per 100 kg straw is:
1. 0.4 kg
2. 4 kg
3. 14 kg
4. 40 kg
Answer
B. 4 kg
4 kg urea in 50 to 60 litres water per 100 kg straw.
Dry matter intake of an adult cow is normally about ____ of body weight.
1. 12 %
2. 0.5 %
3. 2.5 to 3 %
4. 8 %
Answer
C. 2.5 to 3 %
A cow eats 2.5 to 3 kg DM per 100 kg body weight.
Calves should receive colostrum within:
1. 3 days
2. 1 to 2 hours of birth
3. one week
4. 24 hours
Answer
B. 1 to 2 hours of birth
Antibody absorption is best in the first hours after birth.
Fresh fodder has 75 % moisture. How much dry matter is in 400 kg of it?
1. 100 kg
2. 300 kg
3. 250 kg
4. 75 kg
Answer
A. 100 kg
DM = 25 % of 400 = 100 kg.
A feed has 12.5 % crude protein. Its nitrogen content is:
1. 7.8 %
2. 12.5 %
3. 0.8 %
4. 2.0 %
Answer
D. 2.0 %
12.5 / 6.25 = 2.0 %.
A feed analysis shows moisture 10 %, crude protein 14 %, ether extract 3 %, crude fibre 9 % and ash 7 %. The NFE is:
1. 67 %
2. 47 %
3. 57 %
4. 43 %
Answer
C. 57 %
100 - (10 + 14 + 3 + 9 + 7) = 57 %.
A feed has TDN 60 % and DCP 10 %. The nutritive ratio is:
1. 1 : 0.2
2. 1 : 6
3. 1 : 10
4. 1 : 5
Answer
D. 1 : 5
(60 - 10) / 10 = 5.
A cow gives 12 litres of milk. At 1 kg concentrate per 2.5 litres plus 1 kg for maintenance, the total concentrate required is about:
1. 4.8 kg
2. 12 kg
3. 5.8 kg
4. 3 kg
Answer
C. 5.8 kg
12 / 2.5 = 4.8; plus 1 = 5.8 kg.
A buffalo gives 8 litres of milk. At 1 kg concentrate per 2 litres and 1.5 kg for maintenance, the total is:
1. 5.5 kg
2. 8 kg
3. 4 kg
4. 2.5 kg
Answer
A. 5.5 kg
8 / 2 = 4; plus 1.5 = 5.5 kg.
To make a 16 % CP mixture using a 20 % CP feed and a 12 % CP feed, the ratio (20 % : 12 %) should be:
1. 1 : 2
2. 1 : 1
3. 3 : 1
4. 2 : 1
Answer
B. 1 : 1
Parts of 20 % feed = 16 - 12 = 4; parts of 12 % feed = 20 - 16 = 4; ratio 1:1.
A cow of 400 kg body weight eats dry matter at 3 % of body weight. The daily DM intake is:
1. 30 kg
2. 1.2 kg
3. 12 kg
4. 3 kg
Answer
C. 12 kg
3 % of 400 = 12 kg.
If green maize has 20 % DM and the cow needs 10 kg DM from it, the green maize required is:
1. 10 kg
2. 20 kg
3. 200 kg
4. 50 kg
Answer
D. 50 kg
10 / 0.20 = 50 kg.
Rumen bacteria convert urea into microbial protein by first releasing:
1. nitrate
2. ammonia
3. methane only
4. glucose
Answer
B. ammonia
Urease of rumen microbes splits urea to ammonia, which is used for protein synthesis.
A silage mix is made of 1,000 kg green maize at 70 % moisture. It contains dry matter of:
1. 300 kg
2. 700 kg
3. 100 kg
4. 30 kg
Answer
A. 300 kg
DM = 30 % of 1,000 = 300 kg.
Consider the statements: 1. Silage is made at 65 to 70 % moisture. 2. Hay is made at 65 to 70 % moisture. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Hay holds only 15 to 20 % moisture.
Consider the statements: 1. Cottonseed cake contains gossypol. 2. Groundnut cake may contain aflatoxin if stored wet. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
C. Both 1 and 2
Both are true.
Consider the statements: 1. Legumes are rich in protein and calcium. 2. Cereal fodders are usually richer in protein than legumes. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Legumes are richer in protein than cereal fodders.
Consider the statements: 1. Rumen microbes can make B vitamins in adult ruminants. 2. Urea can be fed freely to calves to save protein cost. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Urea is unsuitable for calves.
Consider the statements: 1. Propionic acid is a main source of glucose for ruminants. 2. Acetic acid is the main precursor of milk fat. Which is/are correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
C. Both 1 and 2
Both are standard facts of rumen metabolism.
Match the toxin with the feed: (a) mimosine, (b) gossypol, (c) HCN. Feeds: (i) cottonseed cake, (ii) subabul, (iii) young sorghum. Which is correct?
1. a-iii, b-i, c-ii
2. a-ii, b-iii, c-i
3. a-i, b-ii, c-iii
4. a-ii, b-i, c-iii
Answer
D. a-ii, b-i, c-iii
Mimosine in subabul, gossypol in cottonseed cake, HCN in young sorghum.

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