This document provides information on beef cattle nutrition, including: 1) It describes the digestive system of cows, which have four stomachs - the rumen, reticulum, omasum, and abomasum. The rumen is key for breaking down plant fibers through microbial fermentation. 2) It discusses the microbes in the rumen that break down plant fibers and synthesize proteins and vitamins. These microbes are essential for cattle digestion. 3) It covers important nutrients for cattle such as energy, protein, minerals (calcium, phosphorus, sulfur, potassium, copper, selenium), and water quality and intake requirements. Deficiencies and toxicities of each nutrient are summarized.

1. Basics of
Beef Cattle Nutrition
Bryan Doig, PAg
Livestock Development Specialist
Saskatchewan Agriculture and Food
North Battleford 446-7477
April 19, 2007
1

2. A Cow’s Digestive System
A Cow has four stomachs
Reticulum - The honeycomb" It sorts particles by size, this allows for better
breakdown of food.
Rumen - "The fermentation vat" The largest compartment that is key to volatile
fatty acid absorption. It is like a 55 gallon tank. Its capacity can vary from 46 to
70+gallons in a mature cow.
Omasum - The folded structure" It traps particles within the folds, where the
particles are squeezed to remove water prior to delivery to the abomasum.
Abomasum – “The true stomach" This is where the final breakdown of
digestion takes place.
60 to 120 litres of Saliva produced each day – helps to buffer the rumen –
maintains a more constant pH level.
2

3. The Rumen
Rumen
The rumen is a large fermentation vessel that can contain as much as 220 to
265 lbs of digesting material. Fiber particles remain in the rumen from 20 to 48
hours because bacterial fermentation of fiber is a slow process. However,
particles that digest faster tend to stay in the rumen for a shorter period of time.
Reticulum
The reticulum is the "crossroad" where particles entering or leaving the rumen
are sorted. Only particles that are small is size (< 1-2 mm) and dense (> 1.2
g/ml) may move on to the third stomach.
Omasum
The third stomach or omasum is round (Figure 1) and has a capacity of about 10
liters. The omasum is a small organ with great absorption capacity. It allows the
recycling of water and minerals such as sodium and phosphorus which return to
the rumen through the saliva. Since the modes of digestion in the rumen and the
abomasum differ drastically, the omasum acts as an organ of transition between
these two organs. The omasum is not essential, however, as it is absent in
camels, llamas and alpacas (pseudoruminants).
Abomasum
The fourth stomach is the abomasum. This stomach is like the stomach of non-
ruminants. It secretes a strong acid and many digestive enzymes. In non-
ruminants, ingested feeds are first digested in the abomasum. However, the
material entering the abomasum of a ruminant is made up primarily of
unfermented feed particles, some end-products of microbial fermentation and
microbes which grew in the rumen. 3

4. the “Bugs”
THE RUMINAL BACTERIA
The rumen provides a suitable environment with generous food supply for
microbes to grow and reproduce. The absence of air (oxygen) in the rumen
favors the growth of some particular species of bacteria, among them are those
that can degrade plant cell walls (cellulose) into simple sugars (glucose). The
microbes ferment glucose to obtain energy to grow and they produce volatile
fatty acids (VFA) as end-products of fermentation. The VFA cross the rumen
wall and become the major sources of energy to the cow.
As ruminal microbes grow, they synthesize amino acids, the building blocks of
proteins. Bacteria can use ammonia or urea as nitrogen sources to build amino
acids. Without bacterial conversion, ammonia and urea would be useless to the
cow. However, bacterial proteins synthesized in the rumen are digested in the
small intestine and constitute the major source of amino acids for the cow.
How Rumen Microbes Process Feed
Feed digestion in cattle is a two-step process. First, the bulk of the feed
consumed by the animal is digested by microbes in the rumen. Second, the
microbes and any residues they have not broken down are digested by the
animal itself.
Microbial digestion
Before microbes begin the process of digestion, they must first attach
themselves to feed particles. They do this by secreting a sticky, mucous-like
envelope onto the feed which serves as a bridge for attachment and reduces
their chances of being washed off.
Once attached, microbial cells multiply to form colonies at the site of attachment
and begin to release digestive enzymes which break down the feed. The 4

5. the Remarkable Ruminants
Video “The Remarkable Ruminants”
5

6. Concept of Dry Matter
11.7
23.9
32.8
46.5
12
11
12.1 61
9.2
11
3.5
52 47 4.3
39
23
Alfalfa-Grass Grass Cereal Cereal
Hay Hay Straw Silage
Ash, Minerals, etc.
Moisture
Crude Protein
TDN - Energy
Feeds out of the pail or by the bale.
All feeds contain moisture or water.
It is difficult to compare the nutrients from one feed type to another.
6

7. Concept of Dry Matter
27.2 30
36.9
52.3
13.8 11
10.3
3.9
59.1 52.8 59
43.8
Alfalfa-Grass Grass Cereal Cereal
Hay Hay Straw Silage
Remove the water
Ash, Minerals, etc.
100 % Dry Matter Crude Protein
TDN - Energy
Take the moisture content to zero and nutrient comparisons can now be made.
You can now compare “apples to apples”
7

8. Water Quality
Water is the single most important nutrient
Water is never “pure”
Water may contain
dissolved minerals
pollutants
micro-organisms
suspended solids
organic and inorganic compounds
8

9. Water Quality
Total Dissolved Solids - TDS
a measure of all the inorganic compounds
dissolved in the water
TDS provides a useful measure of the suitability
of a water supply for livestock
TDS Concentration Usefulness for Cattle
ppm or mg/litre
< 1500 Very Good
1500 – 3000 Good
3000 – 4000 Fair
4000 – 5000 Useable
5000 – 7000 Diarrhea in Lactating Cows
7000 + Unsatisfactory
9

10. Water Quality
Sulphates
Concentration Usefulness for Cattle
ppm or mg/litre
< 500 No Problems
500 – 3000 Laxative Effect
800 + Sulphate levels higher than 800 mg/l
may interfere with Copper absorption
and cause deficiency problems
3300 + Unsuitable for lactating cows
10

11. Water Intakes
Requirements
Cows Calves Feeders Feeders
to 500 lbs to 750 lbs to 1100 lbs
Daily Demand Gallons per 1100 lbs liveweight
- Average 10 10 (5) 10 (7) 10
- Hot Weather 20 20 (10) 20 (14) 20
Surface Area Required 4 square feet per 100 head
11

12. Energy
TDN = total digestible nutrients
“Fuel for the body”
Inadequate energy causes . . .
• Loss of body weight and condition
• Inability to keep warm
• Loss of performance
12

13. Crude Protein
Plays an important role in . . .
• digestion and body functions
• muscle and skeletal growth
• feeding the “microbes” in the rumen
• “by-pass” protein
13

14. Calcium
Plays an important role in . . .
• growth and lactation
• digestion and enzyme activity
• deficiency symptoms include
• slow growth, stiff tendons
• retained placentas
• stillborn calves
Maximum calcium content is 1.0% of Dry Matter Intake. Calcium functions in
building and maintaining the structures of bone and teeth, initiation of the clotting
of blood , maximal activity of digestive enzymes and is involved as part of the
messenger system in the body. The body uses both active and passive transport
systems to absorb Ca from the intestine in response to parathyroid secretion .
Absorption is increased by arginine chelation and lysine but decreased by
oxalates, phytates and phosphates. Deficiencies include rickets in the young,
osteomalacia in mature animals, and slow growth. Low dietary Ca levels, vitamin
D deficiency, hypoparathyroidism, renal insufficiency or excessive P dietary
levels are some of the causes of Ca deficiency. Hypercalcemia does not
normally occur because excessive Ca is not absorbed. Calcium is abundant in
grasses, legumes and some oil seeds. It is limited in grains and supplementation
is common with grains. Acceptable ratios are from 1.5:1 to a maximum of 7:1.
Calcium levels are affected by K and Mg.
14

15. Phosphorus
Plays an important role in . . .
• energy transfer in the body
• genetic, enzyme and blood systems
• deficiency signs include
• slow growth, reduced appetite
• reduced feed efficiency
• low milk production
• “silent heat”, lowered fertility
Maximum phosphorus content is 0.6% of DMI. Phosphorus functions in bone
and cell membrane structures, genetic, energy, enzyme and blood buffering
systems. Phosphorus absorption involves both active and inactive systems but
is independent of Ca absorption. Over 90% of P can be absorbed on P deficient
diets. However, the availability of P is rather low (about 15 to 20 percent).
Presence of fatty acids, aluminium and ions which can form complexes with P in
the gut decrease P absorption. Deficiency symptoms include slow growth, pica,
low appetite, low conception rates, reduced feed efficiency and low milk
production. Toxicity can occur when Ca and Mg phosphates precipitate in the
urine (the cause is urinary calculi). Although cattle may receive sufficient P when
fed high grain diets, supplementation is normally required for most classes of
cattle.
Acceptable ratios are from 1.5:1 to a maximum of 7:1.
15

16. Sulphur
• High levels of sulphur in the diet interferes with
copper absorption. Problems occur when
sulphur levels exceed 0.35% diet dry matter.
• At increasingly higher levels and where the
sulphur is readily absorbed, “P.E.M.” or
polioencephalomalacia can result, causing
scarring of the brain tissue and death.
Sulphur is needed at 0.15% of the diet for all cattle. Maximum tolerable level is
0.40%. Sulphur is a constituent of the amino acids methionine and cysteine.
Sulphydryl compounds are involved in the activation of various enzymes,
formation of adrenaline and creatine, bone calcification and prevention of
enzymes from damaging epithelial cells. Most absorption of S occurs in the
small intestine as part of amino acid sulphur. In the rumen, dietary S is usually
degraded to sulphide and then re-used in the formation of microbial protein.
Deficiency symptoms are very varied due to the varied functions performed by
S. Toxicity can lead to polioencephalomalacia (P.E.M.). Excess sulphur from
either the diet or water interferes with copper availability. Sulphur present in
water is additive to sulphur present in the feed or forage.
16

17. Potassium
Excess potassium (over 3.0% of ration DM)
may interfere with magnesium absorption and
reduce feed intake
Cereal greenfeed or silage can have high
levels of potassium (1.8% to over 5.1%)
High levels of potassium can contribute to milk
fever. Measure using the DCAB ratio. Can
also affect the Tetany Ratio (K / Ca + Mg).
DCAB = Dietary Cation Anion Balance (Na+K)-(Cl+S)
+400 to 450 or more = hypocalcemia
Growing and finishing cattle and gestating cows need 0.6% of DMI as
potassium. Lactating cows need 0.7% potassium. Maximum tolerable level is
3% of DMI. Potassium functions in the acid-base balance of the body, enzyme
systems, glucose and amino acid uptake, and blood pressure regulation.
Absorption is mostly by passive means. Several hormones including antidiuretic
hormone, aldosterone (decrease), glucocorticoids (decrease), insulin and
glucagon (increase), influence K levels in the body. Deficiency symptoms
include abnormal electrical activity of the heart, slow growth, stiffness,
convulsions and even death. Deficiency can occur in animals fed high grain diets
and during stressful situations. A small increase in blood K can be toxic The
dietary K/(Mg+Ca) ratio should not exceed 2.2:1. High dietary K reduces
absorption of magnesium but increases calcium absorption from the intestine.
Potassium is involved in the DCAB calculation. At present there are no DCAB
recommendations for beef cattle. Problems with milk fever start to appear when
the DCAB values start to exceed 400.
17

18. Copper
10 to 16 mg/kg of feed (ppm) depending on
sulphur and molybdenum intake
1400 lb cow requires 166 mg to 265 mg/day
Maximum intake is 100 mg/kg of feed
more than 0.25% sulphur and 2 ppm
molybdenum increases the requirement
800 ppm sulphate in water is equivalent to about
0.24% sulfur in the ration
some strains of cattle require more copper
Deficiency symptoms include reduced fertility,
retained placentas, faded hair coat
Copper is needed at 10 mg/kg of diet for all cattle. Maximum level is 100 mg/kg
of diet. It is absorbed in all parts of the gut, with high levels found in the liver and
brain. Absorption of Cu is decreased in the presence of excess calcium, zinc,
cadmium and iron. In addition, high levels of molybdenum and sulphur influence
the availability of copper through the formation of insoluble and unabsorbable
copper sulphide. Molybdenum inhibits sulphide oxide which is required to
release Cu from copper sulphide. Copper availability is increased by chelation
with amino acids, citrate and high protein diets. It functions in various enzyme
systems including desaturase enzymes. The dietary Cu:Mo should ideally be
greater than 6:1, borderline at 2-3:1 and toxic if less than 2:1. Blood Cu levels
are not acceptable unless extremely low. Levels in the liver are more
acceptable.
18

19. selenium
0.3 mg/kg of feed
1400 lb cow, range 3.3 mg to 12 mg
Selenium deficiency can cause white muscle
disease, stillborn calves, weak calves, reduced
fertility, “silent” heat, retained placentas and
reduced immune system
“narrow window” of supplementation. Toxicity
problems do occur from over-feeding Selenium.
Loss of hair, cracked hooves and lameness, weak
or stillborn calves and abortions all result from
excess dietary Selenium
New regulations by the Canadian Food Inspection Agency specify that the
maximum level of Selenium in prepared beef cattle minerals cannot exceed 30
mg/kg. The maximum levels in trace mineralized salt cannot exceed 120 mg/kg.
“White muscle” areas of the province include the Black, thin Black and Grey-
Wooded soils. These soil types are common in the Parkland region of
Saskatchewan.
The NRC requirement for selenium is 0.1 mg/kg but a more practical level is 0.2
mg/kg. Maximum tolerable level is 2.0 mg/kg. Absorption in association to
methionine and cysteine is almost 100% with inorganic sources about 60-70%
efficient. Excretion occurs through the urine, bile and pancreatic juice.
Deficiency symptoms include white muscle disease, loss of condition, retained
placenta, lameness and diarrhea. Toxicity can cause loss of tail hair, sloughing
of hoofs and death from respiratory failure. Selenium and vitamin E perform
related functions in the muscle, one can replace the other to an extent but not
completely.
19

20. selecting Salt
Look for products with these levels of trace minerals
Trace Mineralized Fortified Salt
• 2500 to 3000 mg Copper
• 5000 to 8000 mg Zinc
• 10000 to 12000 mg Manganese
• 90 to 120 mg Selenium
Blue Salt = salt + cobalt + iodine
Blue Salt is “1962” technology. Our cattle have 2000 genetics. It is generally
advisable to use the newer Trace Mineralized Fortified Salts which, in addition to
Cobalt and Iodine, contain Copper, Manganese and Zinc. They can be
purchased with or without Selenium.
A daily intake of 1.5 oz salt containing 120 mg/kg selenium provides 5.1 mg of
selenium
A daily intake of 1.5 oz mineral containing 30 mg/kg selenium provides 1.3 mg of
selenium
Salt plus mineral gives a total of 6.4 mg of selenium – well within the window for
selenium
intakes in “white muscle” areas of the province.
20

21. choosing Minerals
Look for products with these levels of trace minerals
Minerals
• 2500 to 3000 mg Copper
• 5000 to 8000 mg Zinc
• 10000 to 12000 mg Manganese
• 30 mg Selenium
Minerals need to be fed every day
Mineral supplements are used to balance or correct deficiencies of required
minerals that may or may not be present in the feed.
There are many commercially available beef cattle mineral products available in
the market. They are often described as a 1:1, 2:1, 3:1 or 0:1 ratio. This ratio is
determined by the amount of Calcium compared to the amount of Phosphorus
contained in the mineral (expressed as a percentage). A 1:1 mineral may
contain 15% Calcium: 15% Phosphorus or 18% Calcium: 18% Phosphorus or
any other equal amount of Calcium and Phosphorus. A 2:1 mineral may contain
18% Calcium: 9% Phosphorus or any other blend, but it will always have 2 parts
of Calcium for every one part of Phosphorus.
Commercial mineral products may also contain other minerals such as Copper,
Zinc, Manganese, Selenium, Vitamins A, E and D, medicating ingredients and
ionophores.
21

22. vitamin A
Cows require 40 to 50,000 IU’s of Vitamin A
per day (Lactating 70 to 80,000 IU’s)
Grains and weathered forages do not supply
any Vitamin A
High nitrate levels impair Vitamin A uptake
Liver will store Vitamin A up to 90 days
Vitamin A deficiencies include retained
placentas, abortions, stillbirths and weak
calves, reduced fertility and lowered
conception rates, reduced immune response,
night blindness and an increase in “water belly”
Vitamin A can be injected or fed once per week
Vitamin A content of each feed is expressed in thousands of international units
(KIU) per kg and Ib. Recommended and supplied levels of vitamin A are
expressed as IUs. Recommended values are 2200, 2800 and 3900 IU/Kg DMI
for growing/finishing, gestating and lactating cattle, respectively. Vitamin A is a
generic term and refers to all compounds other than carotenoids (pro-vit A), with
vitamin A activity. Vitamin A is fat soluble and is absorbed in the gut mainly as
free retinol and carotenols but is esterified with long-chain fatty acids and
released into the lymph as chylomicrons. Over 90% of vitamin A is stored in the
liver. Light and oxygen oxidize vitamin A and usually over 90% of activity is
retained for periods up to 6 months but stability is reduced by pelleting and in
the presence of trace minerals. Excretion is in the bile and urine. It functions in
vision, growth, glycoprotein formation, reproduction, maintenance of mucus
membranes and immunity. Deficiency symptoms reflect the many functions of
vitamin A. Toxicity results in bone abnormalities, loss of hair, poor growth and
congenital abnormalities. Toxicity problems of Vitamin A are rare as extremely
high amounts would have to be fed over a long period of time.
22

23. The Basics
Thumb rules . . .
• cows do not eat percentages
• cows do not eat decimal points
• cows know nothing about nutrition
Once cows are on a balanced ration,
monitor their condition to ensure that the
feeding targets are being met.
23

24. Feeding Cattle
Cows will only balance 4 things . . .
• the air they breathe
• the water they drink
• dry matter intake
• salt
It is up to us to supply properly balanced
winter rations
24

25. feeding example
One square bale of hay weighs about 65 lbs
During lactation, a 1200 lb cow will eat about
one-half of a bale each day. If that is the only feed
that is provided – this is the result
The cow is losing 0.82 lbs of body weight per day
The diet is deficient in TDN (energy)
Phosphorus Vitamin A Manganese
Selenium Copper Zinc
1200 lb cow lactating April
Alfalfa-Grass Hay – average feed values Crude Protein 14 % TDN Energy 61
%
The cow will lose ½ of a Body Score in 130 days or 7 % of her body weight
1200 lbs X 7% = 84 lbs in 103 days = a loss of 0.82 lbs per day
25

26. example of a balanced ration
1200 lb Cow lactating
Month of April
Feeds and Intake
Alfalfa-grass Hay 22.0 lbs
Straw 2.0 lbs
barley or oats grain 7.0 lbs
1:1 Mineral 1.5 oz per day
Vitamin A 0.2 oz per day (10 million IU per Kg)
Fortified Salt 1.5 + oz per day Free Choice
current month temperature 5 C
previous month temperature -5 C
0.19 lbs ADG
expected calf birth weight 80 lbs
26

27. Basics of Beef Cattle Nutrition
Questions
Comments
Concerns
27

28. end of presentation
Bryan Doig, PAg
Livestock Development Specialist
Saskatchewan Agriculture and Food
North Battleford 446-7477
28