FEEDS AND FEEDING
Ruminants
Dr. J.C. Plaizier
Room 232A
Ext.: 9500
E-mail: plaizier@ms.umanitoba.ca
1. NUTRIENTS
Energy
Protein
Carbohydrates
Lipids
Minerals
Vitamins
1.1. ENERGY:
Capacity to do work
Fuel for metabolic processes
Gross Energy (GE):
The total combustible energy in a feed, determined by measuring the amount of heat produced when a feed samples is completely burnt in a bomb calorimeter. This can also be referred to as Intake Energy (IE).
Digestible Energy (DE)
Energy that is available to the animal by digestion; measured as the difference between GE of a feed and the energy contained in the animal’s feces (FE):
The FE consists of undigested food (FiE) and metabolic losses (FmE)
Metabolizable Energy (ME)
The proportion of the feed GE that is not lost in the feces (FE), the urine (UE) and belched gasses, e.g. methane. (GasE)
ME = GE – FE – UE – GasE
Net Energy (NE)
The amount of feed energy available for production, e.g. growth (tissue energy TE), milk production (lactation energy (LE), pregnancy conceptus energy (YE) and wool/hair energy (VE). It is the energy retained in animal product, and can also be referred to as retained energy (RE). It is calculated as the difference between ME and the heat production (HE).
RE = TE + LE + YE + VE
Heat production results from:
Basal metabolism (HeE)
Voluntary Activity (HjE)
Digestion and Absorption (HdE)
Heat of Fermentation (HfE)
Product Formation (HrE)
Thermal Regulation (TcE)
Waste Formation and Excretion (HwE)
Measurements of HE are made by direct or indirect calorimetry.
HE (kcal) = 3.886O2 + 1.20CO2 – 0.518CH4 – 1.431N or
HE (kcal) = 4.890O2
FE and NEl can also be determined by bomb calorimetry
NEg or NEl = energy value of a feed in terms of its capacity to promote energy retention in growth or to promote the secretion of energy in milk.
NEm = energy value of a feed in terms of its capacity to support basal metabolism
True protein = large complexes of amino acids (60% – 80% of plant protein)
Peptides = smaller complexes of amino acids
Non-protein nitrogen (NPN)
peptides
ammonia
urea
nucleic acids
nitrate
amino acids
Amount of nitrogen (N) multiplied by 6.25. Conversion of protein by assuming that % of N in protein is always 16 % (multiplication factor = 100/16 = 6.25)
Amount of N determined by Kjeldahl technique
Error: Includes all forms of nitrogen, including NPN, that do not contain 16% N
Protein that is completely soluble in rumen fluid.
Degradable Intake Protein (DIP)
Portion of the intake protein that is degraded (broken down) by the microflora in the rumen to peptides, amino acids and ammonia. DIP is required for microbial protein synthesis. SP is included in the DIP.
Undegradable Intake Protein (UIP)
Portion of the ingested protein that escaped degradation in the rumen and can be digested in the other stomachs or in the intestine. It is commonly referred to as bypass protein.
A balance between DIP and UIP is required. Insufficient DIP will limit microbial protein synthesis. Excess DIP will increase rumen ammonia levels, blood urea levels, and urea excretion in the urine or in milk. Elevated blood ammonia is toxic. High yielding cows require UIP with an amino acid pattern to support high milk yields. Potentially limiting amino acids include methionine, lysine, tryptophane and histidine.
1.3. CARBOHYDRATES
Carbohydrates contain carbon hydrogen and oxygen. They are usually divided into structural (fibre) and non-structural (NSC) (predominantly starch and sugars). Structural carbohydrates predominate in the cell wall. Carbohydrates are major energy providing substrates. Dietary fibre is required to obtain maximum dry matter intake (DMI) and energy intake, maintain normal rumen fermentation and milk fat percentage. The main components of fibre are cellulose, hemicellulose and lignin.
Most sugars, e.g. glucose consist of 5 membered rings (pentoses) or 6 membered rings (hexoses) that can be combined into large structures called polysaccharides. Starch is a polysaccharide containing long unbranched chain units and branched short chain units of a-D glucose. Starch is the natural and most abundant glucose storage polysaccharide in plants. Cellulose consists of large complexes of b glucans. b glucans are complexes of glucose. Hemicellulose is a heterogeneous collection of polysaccharides, including xylan (a polymers of xylose, a pentose). Lignin is a condensed products containing aromatic compounds, e.g. polyphenols. Liginin is not digestible.
Fibre should have sufficient particle size. A measure for this is the effective NDF (eNDF) content. Insufficient particle size will reduce rumination, saliva production and buffering of the rumen. End products of fermentation include volatile fatty acids and lactic acid. Hence, insufficient buffering of the rumen results in a drop in rumen pH, referred to as ruminal acidosis.
Laboratory analysis of fibre includes the determinations of neutral detergent fibre (NDF) and acid detergent fibre (ADF). NDF is cell wall material insoluble in a neutral solution containing a detergent. It contains lignin, cellulose and hemicellulose. Some cellwall components, e.g. pectin are removed. Contaminants can include starch, animal keratin and soil minerals. ADF is cell wall material insoluble in an acidic solution containing a detergent. It contains lignin and cellulose. The difference between NDF and ADF mainly consists of hemicellulose. NDF content is negatively correlated with DMI. ADF is negatively correlated with digestibility and NE content. Often NE content is predicted from the ADF concentration.
1.4. LIPIDS
Lipids contain over 2.25 times the energy value of carbohydrates. Lipids mainly include triglycerides, but phospolipids, galactolipids, waxes and carotenoids are also included. There are 3 main types of triglycersides:
1. Unsaturated. These are liquid at room temperature and are mainly obtained from plant sources, e.g. corn oil, canola oil, soybean oil and cottonseed oil.
2. Saturated. These are solid at room temperature and are mainly obtained from animal sources, e.g. tallow.
3. Protected fat. These are treated or combined with another substance, e.g. calcium (soaps) in order to prevent breakdown in the rumen.
Essentials fatty acids (EFA) include linoleic acid (18:2), linolenic acid (18:3) and arachidonic acid (20:4 n6). EFA need to be provided by the diet. Normally enough rumen bypass from these acids occurs to meet the animals EFA requirements. Fatty acids, especially non-saturated fatty acids from plant origin, are toxic to rumen microflora. Hence, overfeeding of unprotected fats, especially vegetable oils, is detrimental. Grain mix ingredients naturally include 3 to 4% fat. Fat can be included up to a maximum of 6 % to 7 % of the DM. The lipid content of a feed is estimated from the ether extract (EE) fraction.
1.5. MINERALS
Minerals are divided into macro-minerals and micro-minerals (trace minerals). This depends on the amount of these minerals in feeds and in animal tissues. Macro-minerals that are supplemented include calcium, phosphorous, sodium and magnesium. Micro-minerals (trace minerals) that are supplemented include zinc, chromium, selenium, copper, iodine and manganese. Homeostatic mechanisms are in place to regulate levels of these minerals in biological systems. However, these mechanisms can be compromised, especially in high yielding cows during early lactation.
Calcium
Extracellular calcium is essential for the
formation of skeletal tissues, transmission of nervous tissue impulses,
excitation of skeletal and cardiac muscle contraction and blood clotting, and
as a component of milk. Intracellular calcium is involved in the activity of
enzymes, acts as an important second messenger, conveying information for the
cell surface to the cell interior. The bone acts as a reservoir of calcium.
Absorption of calcium is controlled by
1,25-dihydroxivitamin D, which is derived from vitamin D. The parathyroid gland
is sensitive to the concentration of calcium in the blood. A decrease in blood
calcium will result in increased secretion of parathyroid hormone (PTH). An increase in blood PTH levels will increase renal absorption
mechanism for calcium in order to reduce the loss of urinary calcium, and will
stimulate the intestinal absorption of calcium by stimulation of
1,25-dihydroxivitamin D synthesis and increase resorption of calcium from the
bone.
Lactation poses such a large drain on calcium
that the calcium homeostatic mechanisms cannot maintain blood calcium
concentration and hypocalcemia occurs. Hypocalcemia impairs the muscle and
nerve functions to such a degree that the cow is unable to rise. This is
referred to as milk fever. The therapy
for milk fever is intravenous infusion with calcium. Milk fever can be
prevented by stimulating the function of PTH. This can be achieved by creating
slight metabolic acidosis through the supplementation of anionic salts, thereby
reducing the dietary cation-anion balance (DCAB) of the diet. Equations to describe DCAB include (Na+
+ K+ ) – (Cl- + S-2).
Phospohrous
Phosphorous (P) has many biological
functions. About 80 % of the P in the body is deposited in bones and teeth. In
bone, it is present with calcium. In cells almost all energy transactions
involve formation or breaking of high-energy bonds that link oxides of P to
carbon or to carbon-nitrogen compounds, such as adenosine triphosphate (ATP). P is an essential component of buffer systems in blood and other body
fluids. Rumen microorganisms require P for digestion of cellulose and the
synthesis of microbial protein.
The
absorption of P occurs in the small intestine. Both and active and a passive
absorption mechanism appear to be in place. The percentage of P absorbed is not
as closely related to need as is the absorption of Ca. The active absorption
process, is also influenced by 1,25-dihydroxivitamin D. There is a long held
view that the ration of Ca to P in the diet is of importance, as the ratio
between Ca and P is roughly 2: 1 both in blood and in bone. However, as the
absorption of Ca and P varies substantially between feeds, and due to P
recycling in the saliva, it has become clear that is not possible to recommend
an optimal dietary ratio of these two minerals.
A
large proportion of P in cereal grains, oilseed meals and grain byproducts is
bound to phytate. Phytate P is unavailable for non-ruminants. In ruminants,
phytase activity of ruminal microorganisms renders nearly all the phytate P
available for absorption.
Accurate and precise management of P
nutrition is crucial to optimize performance and health of dairy cows, but
increasingly, also to minimize P excretion to the environment. Excretion of P
to the environment is a major contributor to contamination of surface waters
leading to eutrophication.
1.6. VITAMINS
Fat soluble vitamins, A, D and E are
routinely added to cattle diets. Vitamin requirements are given in
international units (IU). Is based on biological activity. This is done as many
forms of the different vitamins exist that vary in their biological activity.
Vitamin A has a number of functions, including gene regulation, maintenance and growth of epithelial cells and vision. Plant products contain no vitamin A, but can contain b-carotene that can be converted to vitamin A. Fresh forage is a god source of b-carotene, but hay and concentrates generally contain low amounts. Silage can have moderate concentrations of b-carotene. The requirements for vitamin A are based on a conversion factor of 1 mg of b-carotene = 400 IU of vitamin A. The current recommendation for vitamin A intake is 110 IU/kg of BW.
b-carotene had other functions on top of providing provitamin A. It is founds in several types of immune cells and the ovary, especially the corpus luteum. Hence, effects of b-carotene on immunity and fertility have been suggested.
Vitamin
D is primarily involved with Ca and P homeostasis. It is a pro-hormone for
1,25-dihydroxivitamin D. Hay and other sun-dried foraged contain
vitamin D. Also, cattle exposed to sunlight can synthesize this vitamin. The
requirement of vitamin D has been estimated at 31 IU/ kg BW.
Vitamin E (a-tocopherol)
The primary function of vitamin E is as a
cell membrane antioxidant. It is also involved with arachidonic metabolism. Because of these functions, vitamin E has substantial effects on immune
function. This can contribute to the prevention of mastitis. The minimum daily
allowance of vitamin E has been set at 0.8 IU/kg of body
weight (BW). Supplementation of cows is usually not
needed when cows graze pastures, but might be required is conserved feeds are
fed.
2. FEEDS
2.1. GRASS AND LEGUME FORAGES
Legumes vs. grasses:
Legumes
Generally higher in CP
Higher lignin content: lower digestibility
Lower cell wall content: higher intake
Constant degree of lignification between leaves and stem
Generally lower in CP.
Lower lignin content: higher digestibility
Stems have higher lignin content than leaves
Mixed
First cut vs. second cut: First cut contains
more grass. Second cut contains more legumes.
Maturity
When grasses and legumes get to mature, the CP content and digestibility decrease. Hence, harvest at immature stage.
Hay
Hay is
forage harvested during the growing period and preserved by drying for
subsequent use.
Hay is essential for the proper functioning of the digestive tract, including rumen motility, ruminating and saliva production. Hence, it contributes to maintaining proper conditions for microbial action in the rumen.
Problems:
Quality of hay can be decreased rapidly by rain, sun, bleaching raking, handling when it is too dry and storing with to much moisture (heat damage).
Problems obtaining sufficiency drying time
Losses from cutting to feeding of alfalfa
second cut hay:
Leaves:
35 %
DM:
20 %
CP:
29 %
Silage
Preservation by ensiling. The ensiling process refers to the changes which take place when forage or feed with sufficient moisture to cause fermentation are stored in a silo in the absence of air. The ensiling process requires 2 to 3 weeks.
Aerobic activity: Living plant cells consume oxygen. Hence, as long as ensiling conditions are good, the aerobic phase is short.
Anaerobic activity:
Anaerobic bacteria multiply, molds and yeasts
die.
Some NSC (sugars) are converted into lactic
acid and volatile fatty acids
A proportion of the plant protein is
converted into peptides, ammonia and amino acids. Hence, the proportions of NPN
and DIP increase.
Low pH stabilizes and
conserved the silage.
Sometimes additives are
requited to drive down pH (sugars, molasses)
Advantages of silage over hay:
Higher proportion of
nutrients is retained.
Not as weather dependent
Eliminates danger due to
loss of fire and heat damage
Production process more
mechanized
Disadvantages over hay:
Protein is degraded.
Less DM content,
required handling of more tonnage
Short chop lengths, less
eNDF
May spoil during feeding
Requires silo
Potential palatability
problems.
2.2. GRAIN
Corn
Corn is the leading dairy feed in Eastern Canada and in the USA. It is palatable and an excellent energy source, but it is lower in crude protein than barley. Corn may be fed to dairy cattle cracked, steam flaked or ground. It is low in the amino acids lysine and tryptophane and it is deficient in minerals, especially in calcium.
High moisture corn is corn that is harvested at a moisture level of 22 to 40% and stored without drying. It is preserved by ensiling, and/or by the addition of an organic acid. This reduces the costs for drying and reduces the risks of spoilage due to molding or heating. Also, the producer can harvest at an early date, in order to avoid unfavorable weather.
Barley
Barley is among the leading grains in Western Canada. Compared with corn it contains more crude protein, more fibre, less NSC and less fat. The nutrient content of barley can be quite variable. When fed to dairy cattle, barley should always be steam rolled or ground. The rumen fermentation rate of barley is higher than that of corn.
Digestion rates (% / hr) of carbohydrate
fractions
|
|
Sugars |
Starch |
Fermentable fibre |
|
Corn, cracked Corn, high moisture Barley, rolled dry Wheat, rolled dry |
100-200 200-300 250-350 250 - 350 |
10-20 20-30 20-30 35-45 |
5-7 6-8 4-6 8-10 |
Source: Sniffen et al, 1992.
2.3. PLANT PROTEIN SOURCES
Soybean meal
Soybean meal is the ground residue remaining of the removal of most of the oil from soybeans. The oil extraction process affects the composition of soybean meal. In the past, oil was extracted by solvent, hydraulic and expeller processes. Today, almost all of the soybeans are solvent extracted. Soybean meal has the highest nutritive value and the best-balanced amino acid profile of any plant protein source for dairy cattle nutrition. Soybean meal is low in calcium phosphorous, carotene and vitamin D.
Canola meal is also a plant protein supplement. Its amino acid composition compares well with that of soybean meal. Canola is widely grown in Western Canada. Hence, its costs might be lower than that of soybean meal.
In the processing of sugar cane and sugar beet, the white crystalline sucrose is separated from the molasses and the brown sugars. Molasses can also be produced from citrus. Molasses has value as an appetizer, to reduce dustiness of a ration, as a binder for pelleting and to stimulate rumen activity. It is also a good source of minerals, especially trace minerals. The different forms of molasses are also available in dehydrated form. Excess molasses might be too laxative due to the high mineral and sugar content.
Wheat middlings is a by-product of the milling industry. It consists of the fine particles of what bran, wheat shorts, wheat germ, and some of the offal from the “tail of the mill”. Wheat middlings are low in fibre (< 9.5 %). It is can be used as a source of energy for dairy cows.
Corn gluten is a mixture of the bran (high fibre shell, or hull of the kernel) and steep water solubles (a molasses like material derived from the water used to soak the corn during wet milling). It is defined as the dried residue from corn after the removal of the larger part of the starch and germ, and the separation of the bran by the process employed in the wet manufacture of cornstarch and syrup. Corn gluten meal averages 43 % crude protein. It is an excellent source for UIP.
Soybean hulls are the outer covering of soybean seeds. They are high in fibre and fair in protein content. They have a high fibre content and can act as an energy source for cattle.
Blood meal
Blood meal consists of dried blood. It has a high crude protein content (80 % or more). Blood meal is an excellent source of UIP. As it is of animal origin, it has a good amino acid profile for dairy cattle production.
Tallow
Tallow is beef and/or sheep fat obtained be extracting or rendering. It consist mainly of triglycerides. It may be used to increase the caloric density of diets. However, limitations exist for the amount of fat that can be added to the rations of ruminants.
3. ASSIGNMENT
Farmer Jones from Southern Manitoba milks 100 cows. He grows his own forage, but he buys all his concentrates. He does not believe in a custom made concentrate, he wants more flexibility in choosing a diet. However, he buys a mineral and vitamin mix. This mix is 100 DM. You can assume that all mineral and vitamin requirements are met. The average live weight of his cows is 657 kg. The average milk production is 31.5 kg/d. Average milk composition is 3.7 % milk fat and 3.2 % milk protein. You are an independent feed consultant, and farmer Jones has contacted you for advice.
He feeds all his lactating cows according to the following table:
|
Ingredient |
Amount fed (As fed basis, kg/d) |
|
High moisture corn Mixed hay Corn silage Mixed haylage Blood meal Corn gluten meal Tallow Wheat middlings Soybean hulls Molasses Minerals |
5.3 1.7 32.3 11.3 0.3 0.6 0.2 0.4 0.5 0.5 0.9 |
You had all of these feeds, with the exception of the minerals, analyzed by wet chemistry at Norwest labs in Winnipeg. You also had barley grain, canola meal and barley silage analyzed.
|
|
Haylage (mixed) |
Corn silage (40 % Grain) |
Mixed hay (Mixed) |
Barley silage |
High Moisture Corn |
|
DM (%) CP (% of DM) UIP (% of CP) DIP (% of CP) NDF (% of DM) ADF (% of DM) Ca (% of DM) P (% of DM) NEl (Mcal/kg) Price ($/ton) |
34.6 23.0 29.5 70.5 41.2 34.3 1.64 0.31 1.42 45 |
32.2 9.5 22.6 77.5 49.6 26.7 0.21 0.21 1.55 29 |
89.9 18.2 35.7 64.3 44.7 31.0 1.07 0.31 1.44 85 |
35.5 12.0 14.0 86.0 56.3 34.5 0.52 0.29 1.31 31 |
70.7 10.5 34.5 65.5 9.8 3.2 0.01 0.33 2.02 100 |
|
|
Soybean meal |
Canola meal |
Blood meal |
Corn gluten meal |
|
DM (%) CP (% of DM) UIP (% of CP) DIP (% of CP) NDF (% of DM) ADF (% of DM) Ca (% of DM) P (% of DM) NEl (Mcal/kg) Price ($/ton) |
90.0 47.7 27.9 72.1 8.0 6.5 0.29 0.68 1.96 280 |
92.0 44.0 37.0 63.0 36.2 18.0 0.76 1.15 1.72 162 |
92.0 87.2 78.2 21.8 - - 0.40 0.32 1.50 900 |
91.0 46.8 68.1 31.9 9.0 8.0 0.07 0.61 1.91 360 |
|
|
Tallow |
Wheat middlings |
Soybean hulls |
Molasses |
Barley grain |
|
DM (%) CP (% of DM) UIP (% of CP) DIP (% of CP) NDF (% of DM) ADF (% of DM) Ca (% of DM) P (% of DM) NEl (Mcal/kg) Price ($/ton) |
99.0 - - - - - - - 5.4 450 |
89.0 18.4 25.4 74.6 35.0 11.2 0.15 1.00 1.81 125 |
91.0 12.1 32.3 67.8 67.0 50.0 0.53 0.18 1.77 85 |
78.0 8.5 0 100 - - 0.15 0.03 1.82 210 |
87.0 13.2 36.8 63.2 18.0 8.0 0.05 0.35 1.88 98 |
Question 1. How does the amount of dry matter fed compare to the maximum dry matter intake?
Question 2. Compare the intakes of CP, UIP, DIP, NDF, ADF and NEl with the requirements for these nutrients.
Question 3. Balance the diet to better meet the nutrient requirements.
Question 4. High moisture corn (HMC) is expensive and difficult to get. Suggest a diet without HMC that meets the requirements. Consider inclusion of barley grain. How does the inclusion of barley grain influence diet composition?
Question 5. Soybean meal is expensive. Replace this ingredient with canola meal. What happens to the diet? Balance the diet to better meet the nutrient requirements.
Question 6. Farmer Jones does not want to use corn silage anymore. He wants to use barley silage in stead. What happens to the diet? Balance the diet to better meet the nutrient requirements.
Question 7. You are trying to convince framer Jones that feeding only 1 TMR to all of the lactating cows creates difficulties in meeting the nutrient requirements of all of the cows. The high producers might not meet their nutrient requirements, whereas the low producers might be under fed. Hence, formulate three least cost TMRs for three different production groups. The low group has a daily milk yield of 20 kg/g or lower, the medium group has an average milk yield of 30 kg/d. The high group has an average milk yield of 40 kg/d. Assume that milk composition is 3.7 % milk fat and 3.2 % milk protein for all groups.
Question 8. Early lactation cows have reduced feed intakes. What recommendations do you have for Farmer Jones regarding the feeding of early lactation cows?
|
Table
1. Guidelines for composition of complete rations 3.7 % milk fat, 3.2 % milk protein |
||||||
|
|
Levels of Milk Produced Per Day |
Early
|
Dry |
|||
|
|
<20 kg |
30 kg |
40 kg |
50 kg |
|
|
|
Protein |
||||||
|
Crude protein % |
12- 15 |
16 |
17 |
18 |
19 |
12 |
|
DIP, % of CP |
63 |
61 |
60 |
55 |
55 |
- |
|
UIP, % of CP |
37 |
39 |
40 |
45 |
45 |
- |
|
|
|
|
|
|
|
|
|
Energy |
||||||
|
NEl, Mcal/kg |
1.42-1.52 |
1.62 |
1.72 |
1.72 |
1.67 |
1.25 |
|
|
|
|
|
|
|
|
|
Fibre |
||||||
|
ADF, % |
21 |
21 |
19 |
19 |
21 |
27 |
|
NDF, % |
28 |
28 |
25 |
25 |
28 |
35 |
|
|
|
|
|
|
|
|
Minerals
|
|
|
|
|
|
|
|
Ca, % |
0.47 |
0.58 |
0.64 |
0.66 |
0.77 |
0.39 |
|
P, % |
0.30 |
0.37 |
0.41 |
0.41 |
0.48 |
0.24 |
|
Table
2. Dry matter intake by cows in mid to late lactation |
||||||
|
Milk Yield (kg) |
Cow Body Weight (kg) |
|||||
|
|
450 |
550 |
650 |
|||
|
|
% |
kg |
% |
kg |
% |
kg |
|
10 |
2.6 |
11.7 |
2.3 |
12.7 |
2.1 |
13.7 |
|
20 |
3.4 |
15.3 |
3.0 |
16.5 |
2.8 |
18.2 |
|
30 |
4.2 |
18.9 |
3.7 |
20.4 |
3.4 |
22.1 |
|
40 |
5.0 |
22.5 |
4.3 |
23.7 |
3.8 |
24.7 |
|
50 |
5.6 |
25.2 |
5.0 |
27.5 |
4.4 |
28.6 |
DMI of cows in early lactation may be reduced by up to 18% below the
values in Table
2. Early lactation cows have reduced appetites. Problems
such as difficult calving, milk fever, retained afterbirth or twisted stomach
will further depress DMI. Most cows increase in DMI gradually after calving and
peak in DMI by 10 to 12 weeks of lactation.