Transcript UBC Dairy Education and Research Centre

About myself…
3rd year Graduate Student at UBC
 working towards a Master of Science
Degree
 Program: Ruminant nutrition
 Department: Animal Science
 Faculty: Agricultural Sciences

Where I work…
-UBC Dairy Education and Research Centre
-Pacific Agri-Food Research Centre (PARC)
Agassiz, BC
225 lactating cows
200 cow replacement herd
In the dairy barn
Free stall design
12 cow groups
Parallel double 12
milking parlour
My Research:

Study the effects of nitrogen (N)
fertilization on protein quality of forage
grass
Nitrogen forms
N2: nitrogen gas
 NO3-: nitrate
 NO2-: nitrite
 NH3: ammonia

Amino Acid
H
H
O
N-C-C
H
R
An amino acid
OH
Proteins
2 amino acids together: dipeptide
 3 or more amino acids together: polypeptide
 Polypeptide chain(s): protein

Plant nitrogen
80% of the atmosphere composed of N2
 This N is unavailable for plant nutrition
 Ammonia (NH3 ) is the only form of
nitrogen that can be utilized by the plant

Nitrogen fixation and oxidation

Nitrogen fixation: convert N2 to NH3
 Rhizobium and other types of bacteria
have enzymes that fix nitrogen

Nitrogen oxidation: convert N2 to NO3 Lightning oxidizes nitrogen
Nitrate converted to ammonia

Plants and bacteria have enzymes that are
capable of converting NO3- to NO2 -

Plants and bacteria also have enzymes that
are capable of converting NO2 – to NH3
Ammonia to amino acids, etc.

Ammonia is converted via metabolic
pathways into amino acids, nucleotides, and
other nitrogen containing molecules.
The nitrogen cycle
N2
NO3-
NO2 -
NH3
amino acids,
nucleotides,
etc.
Nitrogen fertilizers
Ammonia, nitrates
 Urea, urea formaldehyde
 Urease required for breakdown
 Organic wastes
 Slow release

Cows are ruminants
rumen
omasum
Ruminants






“Four chambered stomach”:
Reticulum sorts feed
Rumen is full of microbes that ferment feed
 Largest compartment (fits up to 200lbs of
feed)
Omasum filters and absorbs
Abomasum is comparable to our stomach
Cows ruminate
Cows are ruminants
rumen
omasum
Nutrition Made Simple
Cows (like us) are a moving clump of
matter
 Cows need both building material and
energy (to build and move) in diet
 Building material comes from protein
 Energy comes from carbohydrates

Ruminant nutrition protein
terms…
Crude protein: % nitrogen in a sample x
6.25
 “Typical” protein molecule is 1/16
nitrogen
 1/16 = 0.0625
 Problem: not all nitrogen in food is in
protein form

Non Protein Nitrogen and True
Protein:
Crude protein is made up of non-protein
nitrogen (NPN) and true protein (TP)
 Non-protein nitrogen (NPN): nitrogen not
in protein molecules (free peptides, free aa,
nitrates, ammonia, etc)
 True protein (TP): nitrogen in the form of
proteins (peptides linked together)

Protein:
Rumen degradable protein (RDP): nonprotein nitrogen (NPN) and true protein
(TP) that is degraded into non-protein
nitrogen in the rumen.
 Rumen undegradable protein (RUP): true
protein (TP) that is not degraded in the
rumen.

Protein in Feed
Protein Digestion
ammonia
Carbohydrate digestion
Energy metabolism in humans
cell
glucose
Pyruvic acid
O2
Acetyl CoA
ADP
Citric acid cycle
CO2
mitochondria
ATP
H2O
nucleus
The three VFAs used for energy:
Acetate
 Butyrate
 Propionate

VFA metabolism in cows
Butyrate
cell
Acetate
Propionate
Ketone bodies
Acetyl CoA
ADP
O2
Citric acid cycle
CO2
mitochondria
ATP
H2O
nucleus
Human vs. Cattle fat production

Humans:

Excess glucose
used to make fat

Cattle:
Unable to make fat
directly from
glucose
 Excess acetate used
for fat production

My Research: RUP from Forage
Grass
Problems:

Lactating dairy cows need a lot of protein in
their diet

A lot of dairy cow diets have too much RDP
and too little RUP
Environmental concerns

Both NO3- and NH4+ are water soluble

NO3- is also readily leached out of the soil

NH4+ associates with soil colloid particles
and resists leaching
Plant Nitrogen usage
nitrates, ammonia etc. converted into plant
proteins
nitrates, ammonia etc. taken up by
plants
nitrates, ammonia etc. from ground
Possible Solution
Increase the RUP content of forages:
Reduce N fertilization
 Alter harvest schedules
 Identify genetics that give more RUP

What we are doing

We are growing three types of grass in 56
plots

Each plot is either given 0, 200, or 400 kgs
of N fertilizer a year

Plots are cut several times a year and grass
is allowed to dry to between 25-35% DM
The Haldrup Logster Harvester
Harvesting the plots
Harvest

Grass is chopped and put into mini silos

Samples are taken before and after ensiling
and analyzed for CP, TP and fibre
Drying oven
Rumen Degradabilities
Silage is incubated in the rumens of
cannulated cows:
 Incubated silage analyzed for CP
 Know N percentage before and after
 Assess RDP and RUP

The cannulated cow barn
What We Have Found:

Reducing N fertilizer levels decreases the content
of non-protein nitrogen (NPN) in grass

Less non-protein nitrogen = more true protein in
grass

More true protein = more rumen undegradable
protein
Consider a Career in Agricultural
Science

Agricultural community/ farm background

Education in rural setting

Good job prospects