DAIRY HERD NUTRITION pp. 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 LACTATION THE DAIRY COW’S DILEMMA

FACTORS AFFECTING DM INTAKE OF DAIRY COWS Milk production Week of lactation Peak feed intake follows peak milk production

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% Lactation BW gain Energy balance Maintenance Reqt 112 kcal ME Or 73.5 kcal NE/kg.75 ME intake 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/kg 2.5 0.59 3.0 0.64 3.5 0.68 4.0 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 (Acidosis, 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 Diet Minimum NDF, %DM Minimum NDF, %DM 19 25 17 29 15 33

Adjustments in fiber requirement Starch source Forage particle size 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 2 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

First 70 days of lactation Relationship of intake and milk production EARLY LACTATION First 70 days of lactation First 3 weeks are most critical Relationship of intake and milk production Week of peak Milk production 6-8 Feed 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 2 375 3 399 4 417 5 432 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

Increase concentration of CP, Ca, and P in diet 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 Do not feed corn gluten feed at greater that 25% of the DM High 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 cycle 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, %DM Unprotected fat (Tallow) 5 Fat in seed (Soybean, Cottonseed) 7 Ca-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

60 or 45 days to 14 days pre-calving 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: transported from liver as VLDL 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 milk production

Avoid excessive fatness in cows (BCS>4) 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/100 Normal 10 Milk 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 Creates metabolic acidosis 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