18. Dairy Nutrition 2

1. maximize DMI and energy intake

2. support high milk production at DMI 5x maintenance

3. maintain rumen health at a pH of 6-6.5

what are the dairy nutrition goals

the 3wk pre to 3wk post calving period where we are adjusting the cow to a higher grain diet to combat the decreased intake + increased energy demand faced by lactating cows

what is the "transition cow"

transition cow period

at what point is metabolic disease (ketosis and SARA) at highest risk

3.5-4% BW

what is the DMI of lactating cows

50 lb DM/day

what would be your rough DMI estimate (at 3.7% BW) for a 1350 lb lactating cow

1. stage of lactation

2. milk production

3. fiber digestibility

4. environmental conditions

what are some of the factors that affect DMI

ADF: cellulose + lignin

what are the lab estimates we use to measure digestibility of fiber

intake

rumen fill limits ____ on high fiber diets

intake

energy demand drives ____ for lactating cows

intake

diet energy density affects ____ in dry cows

DMI (%BW) = 120/NDF

what formula can we use to estimate DMI of feed based on consumption

3-5hr/d

what is the cow time budget for eating

7-10hr/dr

what is the cow time budget for ruminating

>10hr/d

what is the cow time budget for resting...must be laying down

2-3hr/d

what is the cow time budget for milking

milk production

resting time affects....

decreases milk production

if cows get less than 10hr/d resting, what does that do

comfort

____ affects intake and health of cow

1. conserve energy

2. more rumination: buffering and increased intake

3. decreased lameness and stress on feet

4. increased blood flow to udder

what are the benefits of laying down

front feet in the stall, hind feet in alley, or laying partially in alley

what is perching behavior in cattle

poor stall comfort

what does perching behavior indicate

decreased intake increases lameness risk

what are the implications for perching behavior

18-30in

it is recommended to have ____ space/cow to decrease aggression and increase intake

+2.5-5lbs

+1lb DMI causes +_____ lbs of milk

acetate

what VFA is always made in the highest amount ~65%

milk fat and body fat synthesis

what is the function of acetate

propionate

which VFA is made in the second highest amount at 25%

glucose production...gluconeogenesis constant in cattle

what is the function of propionate

butyrate

which VFA is made in the lowest amount at 10%

ketone production

function of butyrate

VFAs

when microbes ferment carbs in the ruminant GIT, what is produced

starch

propionate mainly comes from what source

propionate

which VFA is considered the primary source of glucose

structural carbs such as cellulose and hemicellulose

what is the main source that acetate is produced from

acetate

which VFA is considered the primary fat source for milk (50% of milk fat) and adipose tissue

7-10hrs

what is the minimum time cows should ruminate each day

fat and acetoacetate (ketone)

acetate is the precursor for ______ and enters Krebs cycle at acetyl Co-A

glucose

propionate is the precursor for ____ and enters Krebs at succinate

B-hydroxybutyrate (ketone)

butyrate is the precursor for ____ and enters Krebs at ketone bodies

adipose tissue

____ provides FFA during lipolysis

1. acetyl CoA

2. acetoacetate

3. liver to produce triglyceride

what do the FFA from adipose tissue serve as precursors for

net energy

what is considered the most accurate energy system as it accounts for all losses in the forms of heat, gas, feces, etc...

1. maintains rumen pH

2. stimulate chewing and saliva

3. prevent acidosis

why does fiber matter

1. ADF > 18%

2. NDF >28%

3. forage NDF 20-24%

5. NFC 37-42%

list the fiber requirements during early lactation

NDF and forage NDF

which aspects of fiber actually stimulate rumination

starches, sugars, pectins

NFC are non-fiber carbs and are not super important but include what...

physically effective fiber length designed to require adequate particle length of >1.5in

what is peNDF

~22%

what is the minimum peNDF value for ruminants

drives rumination and buffering

what is the function of peNDF

NDF of ration + Penn state particle separator

what can we use to determine peNDF

repeated, prolonged periods of depressed ruminal pH (5.2-5.6) causing VFAs to accumulate...NO lactic acid accumulation

what is SARA/subacute rumen acidosis

1. high grain diets: excess VFAs exceed absorption capacity of rumen

2. low fiber (low peNDF): decreased rumination will decrease buffering

what are the causes of SARA

1. decreased intake and milk fat

2. diarrhea and laminitis

what are the effects of SARA

ruminal pH will be closer to normal

what happens to SARA cows several hours after eating

transition cows

SARA is primarily an issue for what cows

0.5-1 unit/day

what is considered a normal ruminal pH fluctuation range

1. intake of fermentable carbs

2. buffering capacity of rumen

3. rate of VFA absorption from rumen

what doe ruminal pH depend on

decreased intake...likely protective

what happens when rumen pH drops below 5.5

rumen damage and bacterial translocation

what are the risks of rumen pH drops

high ambient temp + high humidity

what makes up heat stress

1. decreased intake, rumination, and milk production

2. increased panting: less HCO3- in blood to buffer

what are the effects of heat stress...linking it to increased risk of acidosis

hot weather + high grain diet

what situation is the worst risk for rumen acidosis based on the chart

metabolizable protein

what aspect of protein actually ends up digested in the SI making it available for the animal to utilize to meet protein needs

readily available nitrogen for microbes

what does soluble intake protein (SIP) provide

non-protein nitrogen source such as urea

how can we provide SIP in the diet for microbes

true proteins that are more slowly digested in rumen making them available to microbes over a longer period

significance of degradable intake protein (DIP)/rumen degradable protein (RDP)

undegradable intake protein (UIP)/rumen undegradable protein (RUP)/by-pass protein

which type of protein is not rumen degradable allowing it to be digested in the SI

CHO (carbs) and RDP (rumen digestible protein)

we must carefully balance dietary ____ and ____ because microbial protein synthesis requires energy

nitrogen

___ is required by rumen microorganisms for protein synthesis

50%

microbial protein accounts for about ___ of protein supply to cow

rumen undegradable protein

cow needs ___ ____ ___ in ration to meet remaining protein requirements...common to use soybean meal to do this

16-18%

protein levels of ____% CP in dairy rations

12% CP

protein levels of ____% CP in dry cow requirments

2.25 lb corn

1 lb far has the equivalent of ___ lb corn

3%

base rations have about __% fat

7%

maximum fat in ration about ___% fat on DM basis

fat is un-degradable in rumen and excess causes less carbs and less energy availability for microbes

why does excess fat lead to decreased microbial activity

additional bypass protein

what may be required (in regards to protein) when there is more fat in the diet than needed

DMI

____ is the primary limiter of production

behavior and management

___ and ___ affect intake

fiber and pH

rumen health depends on ___ and ___

SARA

____ is a major production issue

energy, protein, and fiber

the diet must balance ____, ____, ___

ketosis and SARA

what are the primary risks during the transition period

intake, behavior, and milk fat

what can we monitor to assess dairy cow health