Albert De Vries

Department of Animal SciencesUniversity of Florida

Gainesville, Florida, USAdevries@ufl.edu

Economics of Heat Stress: Implications for Management

DAIReXNET Webinar, April 9, 2012

Supported by AFRI Competitive Grant no. 2010-85122-20623 from USDA-NIFA

Topics

• Cost of heat stress, value of cooling• Improved fertility in summer• Sexed semen mix

Dairy heat stress losses in USA

St-Pierre et al. (2003)• Feed intake • Milk production • Reproduction • Repro culling • Death

Average losses due to heat stress• Without any heat abatement:

$167 per cow per year

• With optimal heat abatement system:$100 per cow per year

Annual production and economic losses in 6 states (minimum heat

abatement)

State

Dry matter intake (lbs/cow/

yr)

Milk (lbs/cow/y

r)

Days open

Repro culling (%)

Deaths

(%)

Annual hours of

heat stress (%)

Loss ($/cow/yr

)

WI 201 403 9 0.6 0.1 9 72

CA 320 646 12 0.9 0.2 12 110

NM 370 745 23 2.2 0.5 20 168

AZ 798 1609 26 2.5 0.5 22 256

FL 1971 3975 59 8.0 1.7 49 676

TX 2196 4425 54 7.4 1.6 36 698

After St-Pierre et al. (2003)

Florida seasonal pregnancy rates 1976-2002

summer

winter

De Vries and Risco, 2005

Florida Observation

• Many seasonal breeding herds– Calve in fall, breed in winter, dry in summer

• Preferably no calving in late spring/summer– Heat stress during calving– Death risk (cows, calves)– Milk production , fertility

• Getting cows pregnant in summer: late spring / summer calving

• How important is it to get cows pregnant in summer?

Can we improve profitability

by improved fertility andbetter insemination

decisions?A story of calving patterns

Systems approach

• Large spreadsheet(+) with heifers and cows, lactation curves, fertility, feed intakes, labor, prices, etc.

• Decisions: replacement, insemination, calf raising• Closed herd: sell surplus heifer calves + all bull

calves• Optimize profit per (milking) slot per year• Heat stress effects on milk production, fertility,

death risk

• This is difficult

Relative humidity, temperature and temperature humidity index

for Orlando, Florida

min H

max H

max F

min F

THI

Seasonal herdconstraint: 1300 total cows

cows calved

heifers calved

heifer calves born

heifer calves kept

Seasonal herdconstraint: 1300 total cows

Milk Cows milking

Open cows

Cows present

• Increase probability of conception by 10%

• For example: 40% + 0.1 * 40% = 44%

+10% Probability of conception

constraint: 1300 total cowsNormal +10% Prob.

conception

Profit/slot/year $728 $767+$39/slot/year

heifers

cows

Inseminations+10% probability of conception

constraint: 1300 total cows

cows

heifers

Delayed inseminations+10% probability of conception

constraint: 1300 total cows

cows

heifers

Calvings+10% probability of conception

constraint: 1300 total cows

cows

heifers

1000 milking cows constraint

Seasonal herdconstraint: 1000 milking cows

Milk Cows milking

Open cows

Cows present

Inseminations+10% probability of conceptionconstraint: 1000 milking cows

+$60/slot/year

Normal +10% Prob. conception

Profit/milking slot/year $587 $647

cows

heifers

Present and milking+10% probability of conceptionconstraint: 1000 milking cows

present

milking

Delayed inseminations+10% probability of conceptionconstraint: 1000 milking cows

heifers

cowscows

Calvings+10% probability of conceptionconstraint: 1000 milking cows

cows

heifers

Sexed, fresh IVF embryo transfer in summer increases

conception rates• Summer transfer of sexed in-vitro fertilized

embryos• 200% of conventional AI summer conception rate• 88% heifer calves

Stewart et al. (2011)

• Economics? • $90 per IVF-ET transfer• $250 sold heifer calf, $50 sold bull calf• Change in calving pattern

IVF-ET in summer: scenario Aconception rates and #inseminations,

IVF-ETAll summer “breedings” with IVF-ETNo delayed inseminationsAll calves sold, heifers purchased1300 total cows constraint

conception rate

inseminations/ET

IVF-ET in summer: scenario ACows calved and milking

All summer “breedings” with IVF-ETNo delayed inseminationsAll calves sold, heifers purchased1300 total cows constraint

Value of IVF-ET: -$4 /milking slot/year Normal: $779, IVF-ET: $775

milking

calved

IVF-ET in summer: scenario Bconception rates and #inseminations,

#IVF-ETOptimal summer “breedings”Allow delayed inseminations1000 milking cows constraint

inseminations/ET

conception rate

IVF-ET in summer: scenario BCows calved and milking

Optimal summer “breedings”Allow delayed inseminations1000 milking cows constraint

Value of IVF-ET: $88 /milking slot/year Normal: $569, IVF-ET: $657milking

calved

Conventional, sexed semen, and summer heat stress

• $20 conventional dairy semen– Normal fertility– 48% heifer calves– Extra heifers calves sold for $250, bull calves $50

• $35 female sexed semen– 80% of normal fertility– 88% heifer calves– Extra heifer calves sold for $250, bull calves $50

• What is the optimal mix?

Conventional and sexed semen mix

constraint: 1000 milking cows

Profit conventional only: $587 / milking slot / yearProfit sexed + conventional: $624 / milking slot / year (+$37)

conv. cows

sexed heifers

Summary• Cooling dairy cows pays in hot climates

• Value of improving fertility in summer depends on seasonality of cow performance (milk, fertility) andherd constraints (parlor capacity, cash flow)

• Seasonality has major implications for optimal insemination mix

What do you think?Thank youdevries@ufl.edu