5b. Feeding Cows

Question 1

What is the beef cow-calf cycle?

Answer 1

calve in winter/spring
at pasture over summer
wean calf in call - about 200-300kg
Over winter - preserved feed/pasture
heifer - until had 3rd calf

Question 2

What do we know about repro and cows?

Answer 2

first calf at 22-24mo of age - breed heifers at 12-15mo, %in estrus directly related to weight, 53-65% of mature body weight
Adult cows - % coming into estrus related to nutrition
remain in herd until 10+
usually pregnancy check in fall - sell open cows (~43% of cull cows pregnant at time of culling)

Question 3

What type of digestive system do cattle utilize?

Answer 3

efficient digesters, microbial fermentation, more tolerant of poor-quality diets - no dietary source of EAA’s, or EFA’s

Question 4

What might affect water consumption?

Answer 4

temp, BW, lactation status
Feed can contain water and metabolism releases water

Question 5

what an cause a cattle to have a shortage of energy?

Answer 5

adult beef cattle can meet energy needs from good quality roughage
shortage can occur - overstocked pastures, inadequate feed allowances, poor-quality forages, drought
heat increment - heat released during digestion, contributes to maintenance of body temperatures

Question 6

How to cattle get carbohydrates

Answer 6

ruminal microbes convert plant carbs (cellulose, starh) to VFAs - acetate, butyrate, propionate
VFAs provide 60-80% of a cow’s energy, maintaining a healthy microbial flora is essential

Question 7

How do cattle get fibre?

Answer 7

supports rumen health - maintains rumen distension, stims motility, cud chewing, salivary flow
delivers less dietary energy
balance fibre and non-fibre carbs to optimize energy intake and rumen health

Question 8

How do cattle get protein?

Answer 8

Have overall N req - no AA are essential in diet, sulfur req (sulfur-containing AAs)
Protein or Non-protein Nitrogen - ammonia and urea
Ruminal microbes can synthesize AA using NPN source, carbs and dietary energy
Generally need at least 2/3 of N as dietary protein - energy is limiting factor

Question 9

How do cattle get minerals?

Answer 9

direct add to feed
mineral blocks - typically contain Ca and P source, copper, iodine and selenium, free choice blocks should contain 25% salt

Question 10

Why should free choice blocks contain 25% salt?

Answer 10

Palatability

Question 11

How do we feed roughage?

Answer 11

cattle are ruminants - req roughage for rumen health, an inexpensive and widely available feed
Maintenance requirement
1.5% of BW as roughage DM
More if poor quality
Typically at least 60% of diet DM is roughage

Question 12

What is the allowance for wastage?

Answer 12

extra 10-30%, some of this is unpalatable feed, some is pure wastage from being trampled on
Reduce by using bale feeders
Chopping forage and feeding from a bunk

Question 13

How much dry matter intake do cattle need?

Answer 13

amount consumed per day (moisture free)
Impacted by feed composition, cow physiology, management
Max dry matter intake is 2-3% of BW

Question 14

How does feed composition affect dry matter intake?

Answer 14

neutral detergent fibre content, quality of feeds, maturity of forage, nutrient availability

Question 15

How does cow physiology affect dry matter intake?

Answer 15

age, body size, physiological state, BCS, lactation/production lvl

Question 16

How does management affect dry matter intake?

Answer 16

Feed bunk management
group strategies
heat abatement strategies
maintenance of body temp

Question 17

What are the nutritional phases in a cow’s life

Answer 17

spring - calving, lactation and early preg
Summer - lactation and pregnancy
Fall - calves weaned
Winter - calves mature

Question 18

What happens during the spring of a cows life?

Answer 18

Calving, lactation and early preg
Cow-calf pairs graze pasture - may move to community pasture
Pasture may not be adequate - too cold early in year/drought
supplement cows with good hay and grain

Question 19

What happens during the summer of a cows life?

Answer 19

lactation and pregnancy
at pasture - roam with bull(s), typically on community pasture, pasture rotation is best - parasite control, fertilize for optimal growth, allows grass a recovery period

Question 20

What are some pasture problems?

Answer 20

variable quality, not always growing, damage from over grazing
Shortage of pasture - move to new pasture, crop residue, preserved feed
Poor cattle prices - no incentive to sell, but can’t afford to feed
Drought - not enough to feed
Welfare cases - sell cows, don’t let them starve, producers often don’t want to lose genetics

Question 21

What happens during the fall of a cows life?

Answer 21

Calves are weaned
mild gestation, lactation stops at weaning
period of lowest nutritional requirements for cows
Cows may graze - forage left on grain fields after harvest, straw + missed grain, damaged crops, grass undersown in barley field, maize fields, pasture - particularly in warm wet fields

Question 22

What is weaning?

Answer 22

typically wean at end of summer/in fall when grass is no longer growing - gradual weaning using a nose rung to stop sucking is best, wean about a week later when nursing has stopped
Calf then - background or sent to feedlot

Question 23

What is acute bovine pulmonary emphysema and edema?

Answer 23

ABPEE aka Fog fever
Sudden onset of resp distress, minimal coughing
course ends after a few days (Fatally or with dramatic improvement)
Typically in fall, 5-10 days after change to lush green pasture bc of rapidly growing pastures has L-tryptophan which is converted by ruminal microbes into 3-methylindole which is then absorbed into the blood stream to cause epneumotoxicity
Introduce to lush pasture slowly

Question 24

When do we perform BCS?

Answer 24

in the fall when pregnancy checking - check that enough feed available for winter
feed to reach or maintain a BCS of 6 or 7
to move a 500kg cow from score 2-6 in 100d - req nutrients for maintenance, fetal growth, gain in body condition
the colder it gets the more difficult it is to improve condition

Question 25

What do cows eat during the winter pase of their life?

Answer 25

preserved feeds like hay, silage, greenfeed, straw/chaff (<80* of diet) + grain
mature cows have greater body reserves and lowe nutrient req than heifers
Can generally be over-wintered on rations of poor quality
should maintain weight fall to fall
Calve at BCS 5.5-6 - over-conditioning causes excess fat deposition in udder and lower milk prod, inc risk of dystocia

Question 26

What should the fetal growth % be around at two months pre-calving?

Answer 26

70-80% of fetal growth
at late stage gestation or lactation 20-45% higher energy req and 40-80% higher protein requirements

Question 27

What happens to feeding in the winter when its cold?

Answer 27

inc nutrient reqs, rely on heat prod in rumen to maintain body temp, particularly in thin cows
feed 0.5kg extra grain for every 5C drop - if below -20C and drop is sudden
poor quality feed, insufficient feed
Moldy feeds - reduced nutritional quality, risk of abortions and other reproductive problems
Moldy sweet clover - high in courmarin, converted to moulds to dicoumarol, interfere with metab of VitaK

Question 28

What are the limitations on feeding non protein nitrogen?

Answer 28

ruminal microbes can synthesize AA’s using NPN source, carbs and energy
Need 2/3 of N as dietary protein - energy limiting
high prod animals like lactating cows or feedlot calves will require all/most of dietary N as protein - microbial synthesis of AAs from urea requires too much energy
Beef cow in mid gestation - can be fed urea

Question 29

What is hypocalcemia?

Answer 29

usually seen in late preg/early lactation
early or rapidly rising lactation
dairy cows after parturition - going off feed also predisposes
affects all muscle types - weakness and recumbency

Question 30

How does hypocalcemia affect the body?

Answer 30

inc demand for Ca overcomes ability to maintain homeostasis - body stores (bones) are adequate, low plasma ionizes Ca, Ca removal exceeds replacement from diet and bone - mobilized from bone cannot keep up
Avoid high Ca concentrations in prepartum ration - high ca rations prepartum down-regulate the regulatory syste

Question 31

What does anionic diets give cattle?

Answer 31

DCAB (dietary cation-anion balanced feeding systems)
DCAB promotes acidic condition, which promotes ca mobilization

Question 32

How do we feed calves?

Answer 32

“creep feeding”
grain mixture or high-quality forage accessible only by calves
high fibre, corn gluten, dry distiller’s grain, soyhulls
Salt-vitamin-mineral mix
commercial 14-16% protein creep feed

Question 33

What do we feed replacement heifers during the weaning to breeding stage

Answer 33

weaning to breeding - feed separately
weigh about 53-6% of mature weight at breeding - usually breed one cycle (21d) before cows - 13-14mo, better observation, short calving period
need to gain about 0.5kg/day from weaning to breeding

Question 34

What are some possible winter diets?

Answer 34

gray hay (75%) and grain (25%)
Corn silage (96%), protein supplement(4%)
Alfalfa/grass hay mixture
feed adlib (2.5% of BW plus wastage)

Question 35

How do we feed our replacement heifers from breeding to calving

Answer 35

summer - at pasture
next winter - still req separate feeding, req more feed than adults as still growing

Question 36

How do we feed our breeder bulls?

Answer 36

Growing bull calves req balanced ration
yearling bulls fed extremely high energy diets prone to dz and reduced longevity
deficiency of carotene, phosphorus, energy and protein can reduce fertility
ensure present in adequate amounts in ration 6-8wks prior to breeding

Question 37

How are calves finished in feedlots?

Answer 37

enter feedlot - immediately following weanings, after backgrounding (yearlings) - less dz
purchased from a variety of sources, shipped long distances + comingled = high risk of resp dz at entry to feedlot

Question 38

How is backgrounding?

Answer 38

growing, feeding and managing steers and heifers from weaning until they enter the feedlot
feed is typically forgage-based w/ some grain feed
Control weight gain - gain enough muscle and bone before laying down fat covering an dmarbling

Question 39

What are some approaches to purchasing?

Answer 39

buy preconditioned calves - adapted to partial grain diet, dewormed, vx’d, may be favored by sm feedlots
Buy poorer calves - less expensive, favored by feedlots w/ good tx protocols, concerns about policing of pre-conditioned

Question 40

What is compensatory growth?

Answer 40

growth initially restricted by a low enegery (roughage) diet - poorer body condition
placed on a high energy diet - eat more, grow faster, less energy used for maintenance compared to better conditioned animals, attain normal mature size
favored by buyers

Question 41

What is the diet for feedlot calves?

Answer 41

fed ad. lib
first 2wks - good quality hay
Then switch to higher energy diets - transition diet that contains 30% or less roughage, contain grain and often protein supplement

Question 42

What is ruminal acidosis?

Answer 42

inc rapidly fermentable carbs, accumulation of VFA, and dec ruminal pH

Question 43

How might ruminal acidosis happen/

Answer 43

grain overoad - ruminal pH <5, lactic acidosis and acidemia, CV collapse, shock, death
Subacute ruminal acidosis - rminal pH 5.6-5.2; repeated occurrence, indigestion, dec feed intake, bacterial leakage into portal circulation can = liver dz
slow transition to allow ruminal mucosa time to adjust
longer forage particles

Question 44

What is frothy bloat?

Answer 44

prod of insoluble slime by rumen bact when fed high-carb diets
Particularly if feed is too finely ground - fermented gas entrapment by fine particle size
most common in cattle on grain diet for 1-2mo - inc lvl of grain feeding, slime -prod rumen bact proliferate to lg enough #’s

Question 45

What are fat and finishers?

Answer 45

possibly added fat at up to 4% of DM
excess fat lvls may be unpalatable and affect rumen microbes
sources - rendering, vegetable oil, kitchen grease
advantages - inc caloric density, less dust loss

Question 46

What are conditioners?

Answer 46

reduce dust loss (blwon away) in dry feed
reduce sorting - selective eating of more palatable feed
improve palatability
usually used on dry (90^ DM) diets - beet molasses, cane molasses, tempering feed w/ water

Question 47

What are some buffers to add to feed?

Answer 47

sodium bicarb - about 0.75% of diet DM
protcts against ruminal acidosis
improves feed intake

Question 48

What are ionophores?

Answer 48

Antibiotics that ar enot medically important - not used therapeutically or in non-ruminants, lasalocid and monensin
Used in feed
especially effective against gram+
alter ruminal microbial popul. - inc propionate, dec methane, reduce AA degradation

Question 49

What are the benefits of adding ionophores to diets?

Answer 49

recently added to feedlot diets
improved feed efficiency as less methan wastage - 2.5-25% inc feed efficiency, 3% dec DM intake, 2.5% inc average daily gain
Less ruminal acidosis - off feed, mild bloat, +/- diarrhea, low rumen pH, more meals and eat more slowly
less bloat - coccidostats

Question 50

What should be monitored in feedlot cattle?

Answer 50

checked constantly, diet, growth rate, weight

Question 51

What are the steps to formulating a ration?

Answer 51

1) Determine nutrient req, feed intake and desired weight gain for each class of cattle
2) Feed-test “on-farm” feeds to determine
nutrient levels
3) Determine required “off-farm” feedstuffs
(protein supplements, minerals, feed additives,
vitamins…)
4) Formulate rations
5) Implement the nutritional program and
monitor the performance of the cattle
6) Adjust rations according to weather conditions and animal performance