3 Nutritional Management 1 Flashcards
What is the role of grains?
Optimize rumen fermentation to maximize production
Different types of forage
Legume, grass, straw, barley silage, corn silage
Nutrient composition of the forage types
Legume: high NDF, high CP
Grass: high NDF
Straw: highest NDF
Compare CP, NDF and starch contents of barley vs corn silage
Barley:
10-15% CP
45-55% NDF
10-25% starch
Corn:
8-12% CP
40-50% NDF
5-30% starch (higher, but larger variation)
Why is barley silage used? When is it grown & harvested?
Agronomically more predictable than corn
Grows May to August
Harvested as whole crop silage at mid-dough stage
Why is corn silage used? What does it depend on
Greater yield
Environmental conditions affect starch content, plant growth and kernel filling
What are Corn Heat Units (CHU)
Measure of the heat accumulated over the growing season specific to the physiological needs of a corn plant
What is used to calculate CHU?
Minimum and maximum temperatures
When does no growth occur for corn plants?
Night temps (min) below 4.4C
Day temps (max) below 10C
What happens when CHU is low?
There is a greater risk of killing frost before corn matures
What is the milk line?
White line in corn
For silage, harvest when milk-line is in the middle
When is corn silage more digestible?
> 12 weeks after harvest
do not feed right after harvesting, there is poor digestibility
Why does corn silage become more digestible over time?
Starch granules are embedded in a protein matrix
Protein matrix solubility increases with time (less protective wall) = increased digestibility
Three types of silage storage
Upright silo
Ag-bag
Bunker silo
How is silage preserved?
fermentation and production of lactic acid (inhibits decomposition of the herbage until feeding)
25-50% dry matter anaerobically stored (high moisture = good environment for lactic acid producing bacteria)
Slide 25*
Ensiling process (confusing)
Four important characteristics of silage storage environments
- sugar (fermentable CHO to make lactic acid)
- moisture (50-75%)
- correct pH (4.0)
- no oxygen
Nutrient losses associated with ensiling
- plant respiration
- CO2 production (initial fermentation)
- seepage (moisture content)
- secondary fermentation (aerobic fermentation by yeasts and molds in silage exposed to oxygen at silo face)
Losses associated with silage vs hay
Silage = storage loss
Hay = harvest loss
How much moisture in hay? Why?
<20%
safe storage without mold
How are nutrients lost during hay harvest?
When drying in the field, leaves easily fall off the stem. When collected, leaves may fall off and only stem is collected
Leaves contain more protein and are more digestible
Stems contain more fiber and are less digestible
Nutrient losses associated with hay (5)
- shattering (loss of energy and protein when leaves fall)
- plant respiration
- rainfall or leaching loss
- bleaching (sun curing)
- losses at feeding
Pros of feeding grains to ruminants
- high in digestible E
- low cost / kg of digestible energy (in general)
- decrease need for on-farm storage
- easy to feed
Cons of feeding grain to ruminants
Risk of rumen acidosis / lameness
