DAIRY HERD NUTRITIONpp. 435-442;

446-449

GOALS IN FEEDING A DAIRY HERD

• Maximize milk production• Maintain reproduction• Prevent metabolic diseases

– Ketosis– Milk fever (parturient paresis)– Displaced abomasum

• Control feed costs• Minimize nutrient excretion

EARLY LACTATIONTHE DAIRY COW’S DILEMMA

FACTORS AFFECTING DM INTAKE OF DAIRY COWS

• Milk production• Week of lactation

– Peak feed intake follows peak milk production

0 10 20 30 40 500

0.51

1.52

2.53

3.54

4.5

Week of lactation

DMI,

% B

W

• NDF concentration

• Fat concentration of diet– Feeding > 5% fat reduces DM intake

• Worse problem with unsaturated fats

• Diet moisture– Feeding diet > 50% moisture reduces DM intake

• Improper adaptation to high grain diet reduce DM intake

• Metabolic diseases (ketosis or milk fever) reduce DM intake

IMPLICATIONS OF CHANGES IN FEED INTAKE OF DAIRY COWS

• Increase in feed intake follows increase in milk production in early lactation

• High level of feed intake increases rate of passage– A reduction in digestibility of 4% for each increase in DMI of

1x maintenance (Typically DMI will be 3x maintenace)– Reduction greater on high grain diets than high forage diets– Reduces ruminal protein degradability

Energy Requirement of Dairy Cows• In lactating dairy cows, it has been shown that energy

is utilized for maintenance, lactation and pregnancy with approximately equal efficiency– 60 – 70% with an average of 64.4%

Energybalance

0

ME intake

MaintenanceReqt 112 kcal MEOr 73.5 kcal NE/kg.75

Lactation

BW gain

• As a result, the energy requirements for all expressions are expressed as one term, NEl

NET ENERGY REQUIREMENT FOR MAINTENANCE OF DAIRY COWS

• Calculation– NEl, Mcal/day= 0.08 kg BW.75

• Factor affecting maintenance– Extra activity % increase

• Flat pasture, close 10• Hilly pasture, far 50

– Temperature• Cold

– Assume NEl concentration of diet reduced by 8%• Heat

– Assume a 25% increase in maintenance– Pregnancy % increase

• Day 190 60• Day 270 86

– Growth % increase• 1st lactation 20• 2nd lactation 10

NET ENERGY FOR MILK PRODUCTION BY LACTATING DAIRY COWS

• NEl, Mcal/kg milk = .0929 x Fat% + .0347 x CP% + .0395 x lactose%• Example (Assume 3.4% CP and 5.8% lactose)

% fat Mcal/kg2.5 0.593.0 0.643.5 0.684.0 0.74

• Simply added to maintenance

NEL REQUIREMENTS OF 680 KG COW PRODUCING 10,000 KG MILK/YR

FIBER REQUIREMENT OF DAIRY COWS• Adequate fiber of the appropriate length is necessary to:

– Maintain milk fat percentage– Maintain rumen health (Parakeratosis, Laminitis, Displaced abomasum)– Maintain feed intake

• Recommendations– Minimum amount of forage = 40% DM– 1989 NRC

• Minimum NDF = 28% (75% from forage)• Minimum ADF = 18%

– 2001 NRC NDF requirement Forage DietMinimum NDF, %DM Minimum NDF, %DM 19 25 17 29 15 33

• Adjustments in fiber requirement– Starch source

• High moisture corn 27% NDF (Minimum)• Barley 27% NDF (Minimum)

– Forage particle size• Desire length of chop of forage at ¼”

15 to 20% of particles > 1.5”– Method of feeding

• Feeding separate components will increase the NDF requirement

– Dietary buffers• Can lower NDF requirements• Buffers (fed at 0.5 – 1.5% of DM)

– NaHCO3– MgO– KHCO3

• Unpalatable• Will increase rumen pH, but doesn’t solve all problems

associated with low fiber

PROTEIN REQUIREMENTS OF LACTATING DAIRY COWS

• Metabolizable protein requirement follows milk production– MP reqt, gm/d = (Maintenance + (Milk production, gm x

.036))/.67

• Meeting the protein requirements of dairy cows– Increase crude protein concentration and reduce

protein degradability in early lactation• No NPN use

– Lower crude protein concentration and increase protein degradability in mid- and late lactation

• NPN may be used in late lactation to limits– Supply enough degradable protein to meet

microbial needs during dry period to 3 weeks prior to freshening

• NPN may be used to limits

Ca AND P REQUIREMENTS OF DAIRY COWS

• Ca and P requirements follow milk production and pregnancy

PHASE FEEDING OF DAIRY COWS

EARLY LACTATION• First 70 days of lactation

– First 3 weeks are most critical• Relationship of intake and milk production

Week of peakMilk production 6-8Feed intake 8-12

• Results– High producing dairy cows can’t meet energy

requirements and fiber requirements in early lactation

• Implications– Meet the cow’s fiber requirements and accept the

loss in cow weight.• A dairy cow in good condition (BCS 3.5 on 5 point scale),

but not overly fat, can safely lose up to 15% of her bodyweight in first 70 days.

• Energy mobilized from tissue related to BCS BCS Mcal NEl

2 3753 3994 4175 432

• Example– A cow at BCS 4 losing 1 BCS will produce 417 Mcal/0.74 Mcal/kg 4% FC milk = 564 kg FCM

• Cows should not be at a condition score >4 coming into lactation

– Will be susceptible to ketosis and displaced abomasum

• Body weight lost should be replaced during late lactation– Advantages Efficiency Stage of lactation ME to tissue Tissue to milk Total Late lactation 75 82 61.5 Dry period 60 82 49.2 Diet to milk 64.4– Additional advantages of replacing weight in late lactation

» Easier to feed grain to lactating cows» Because of higher feed intake of lactating cows, easier

to meet fiber requirement while feeding grain

– Maximize feed intake• Don’t have cows at BCS>4 (5 point scale)• Use premium or supreme quality forage• Properly adapt cow to grain

– Introduce to lactation grain mix 2 weeks before calving– Increase grain mix at 1 lb/day in early lactation to

lactation diet• Delay fat supplementation until week 5 to 7• Do not feed DDGS at greater than 20% of the DM

– High fat and fiber– Increase concentration of CP, Ca, and P in diet

• Can’t mobilize these nutrients as readily as energy• Utilize sources of rumen undegradable protein and

protected amino acids (lysine, methionine)– Supplement

• Salt 0.5 % DM• Trace mineral• Vitamin A 5,500 IU/kg DM• Vitamin D 1,500 IU/kg DM• Vitamin E 40 IU/kg DM

MID TO LATE LACTATION• Mid lactation 70 to 140 days• Late lactation 140 to 305 days• Replace body energy stores

– Will breed when positive energy balance occurs• Balance diet to meet energy and nutrient

requirements • Maximum Grain = 2.5% BW• Minimum Forage = 1.5% BW

• Can utilize supplemental fat to increase energy concentration

Supplemental fat source Maximum fat in diet, %DMUnprotected fat (Tallow) 5Fat in seed (Soybean, Cottonseed) 7Ca-salt of long-chain fatty acid 7– Problems with excess fat

• Milk fat depression– Trans-10, cis-12 linoleic acid produced from hydrogenation of

fatty acids in rumen of cattle fed high grain diets inhibits fatty acid in the mammary gland

• Reduced feed intake• Reduced milk protein

– Need to supplement RUP• Reduced digestion of Ca and Mg• Excessive fatness if BCS>3.5

– Can utilize NPN to limits• No more than 1/3 of the diet CP• No more than 1% of the diet DM

– Supplement • Salt 0.5 % DM• Trace mineral• Vitamin A 3,700 IU/kg DM• Vitamin D 1,000 IU/kg DM• Vitamin E 30 IU/kg DM

DRY PERIOD

• 60 or 45 days to 14 days pre-calving• Goals

– Maintain body condition• Prevent excessive fatness• Feed a high forage diet

– Can use some lower quality for to dilute energy• May have to limit feed

– Particularly corn silage• Consequence of excessive fatness is ketosis

• Ketosis-fatty acid liver– In early lactation, energy must be mobilized from tissue reserves

Excessive use of body fat Lack of OAA Lack of carnitine Lack of niacin

Overcomes limit of triglyceride to be:1. transported from liver as VLDL2. oxidized in TCA cycle in liver

Fat accumulates Acetyl-CoA in hepatocytes (Fatty liver) Acetoacetate B-OH-Butyrate Impairs gluconeogenisis

Impairs feed intake Appear in milk Reduces glucose Increased milk fever Increased displaced abomasum Increased retained placenta Increased mastitis

Reduced milkproduction

– Ketosis prevention• Avoid excessive fatness in cows (BCS>4)• Maximize intake immediately before and after

calving– Avoid abrupt change to high grain lactation diet at

calving– Feed balanced ration– Use high quality forages

• Drench cows with propylene glycol (1L/day) for 1 week daily before calving

– Propylene glycol is metabolized to lactate that can be used for gluconeogenisis

• Supplement with nicotinic acid (6 – 12 g/d)– Increases DMI– Reduces lipolysis– Recommendations

» Use in ketosis prone cows» Use from 14 days prepartum to 120 days postpartum» Use palatable carrier

– Prevention of milk fever• Milk fever (parturient paresis)

Serum Ca, mg/100Normal 10Milk fever 4.6

• Occurs immediately before or after calving• Caused by failure of Ca homeostasis

– Reduced calcium absorption from small intestine– Reduced mobilization of Ca from bone– Both result from alkalosis caused by a high

concentration of cations relative to anions in diet• Prevention

– Reduce cation-anion difference– DCAD = ([Na+] + [K+] + .15[Ca+2] + .15[Mg+2])

- ([Cl-] + .6[S-2] + .5[P-3])

Methods to decrease DCAD during dry period• Decrease concentration of cations (particularly K) in

diet– K is the cation in highest concentration in dairy rations– Factors affecting dietary K levels

• Legumes > Grasses• Immature > Mature• Leaves > Stems• Heavily fertilized > Unfertilized• High temperatures > Cool temperatures

Dietary K, %Dietary Ca, % 1.1 2.2 3.1 .5 Urine pH 5.8 8.0 8.1 1.5 5.7 7.9 8.2

.5 Milk fever incidence 0/10 4/11 8/10 1.5 2/10 6/9 3/13

- Decrease Na concentration in diet- Decrease Ca concentration of diet???

Method of decreasing DCAD (Continued)• Adding anions to diet

– Commonly added anions• CaCl2

• Ca propionate• Ca SO4

• NH4Cl• (NH4)2SO4

• MgCl2

• MgSO4

– Unpalatable and may causes ulcers in mouth and GI tract– Monitor urine pH

• Desired range 6.2 – 6.8– CaCO3, PO4 salts and elemental S are ineffective– Recent studies increasing the anion content of forages by

fertilizing with CaCl2 shows promise– Do not use on heifers

• Return to positive DCAD after calving

• Other considerations in dry period nutrition– Feed 12% CP

• To maintain rumen microbial growth– Feed 60 to 80 gm Ca/day– Feed 30 to 40 gm P/day– Limit salt to 28 gm/day

• To prevent udder edema– Vitamin A 5,500 IU/kg DM– Vitamin D 1,500 IU/kg DM– Vitamin E 40 IU/kg DM

TRANSITION PERIOD• 2 weeks pre-calving• Feed lactation grain mix up to .5 to 1.0% BW• Maintain long hay at .5 to 1.0% BW• Limit corn silage to 1.0% BW