Effects of heat stress on reproduction in cattle

Transcription

1 Effects of heat stress on reproduction in cattle P.J. Hansen Dept. of Animal Sciences University of Florida Take Home Message #1 Heat stress affects most aspects of reproduction but especially fertility Effects of Heat Stress on Reproduction ESTROUS BEHAVIOR FERTILITY FETAL GROWTH Take Home Message #2 Best Estimates of Heat Stress Needed to Reduce Fertility is a Rectal Temperature of 12.2 o F Body Temperatures at Which Cows Experience Declines in Production and Reproduction Conception rates decline as afternoon rectal temperatures > 12.2 o F normal rectal temp~ o F The critical vaginal temperatures are ~ 12.5 o F in the PM 1

2 Take Home Message #3 Day 2-3 after estrus Heat stress can compromise fertility many weeks later Changes in Sperm Motility in Bull Semen During and After Heat Stress Take Home Message #4 The only reproductive technique known to increase fertility during heat stress is embryo transfer It works very well! 88 o F for 8 h/ 95 o F for 16 h per 24 h day Meyerhoeffer et al., J. Anim. Sci. 6, Effectiveness of a single use of fixed time AI for first service on pregnancy rate during the summer in lactating Holsteins in Florida 6 Day 2-3 after estrus Percent Pregnant Control TAI Arechiga Arechiga de la Sota Arechiga Arechiga de la Sota First service 12 d postpartum 2

3 Pregnancy rate (%) * * * * * * ET AI T < 22.5 C Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Take Home Message #5 Reproduction of beef cattle can be affected by heat stress but it is much less of a problem than for dairy cows Lactating Cows Burn as Much Energy as Human Athletes and Must Lose that Heat to Prevent Hyperthermia Human Athlete Typical human requires 2 Mcal/day Extreme aerobic exercise can increase caloric requirements by 6 to 8 Mcal/day (i.e., 3 4 times maintenance) Seasonal Variation in Pregnancy Rate Per Insemination in Dairy Cows and Heifers in Florida Lionel Bonaventure/AP Dairy Cow at Peak Lactation Average dairy cow produces 99 lb/day at peak lactation Maintenance energy=15 Mcal ME/day Extra energy for milk=55 Mcal ME/day Total energy demands=7 Mcal ME/day At peak lactation, energy consumption increases to 4.7 times maintenance Santos et al. (21) Reprod. Dom. Rum. VII: Badinga et al., J Dairy Sci. 68:78 (1985) Body temperature in Holsteins Wisconsin (Sartori et al., 22) Infertility Heat Stress is Often Not a Major Problem for Beef Cattle Fertility Because: They produce much less metabolic heat than dairy cattle They are not always bred during the hottest times of the year Many breeds are thermally adapted 3

4 Calving interval (days) Differences in Calving Interval for Cows Calving in Fall (Sept-Nov) vs Spring (Feb-April) in Oklahoma Fall Spring RELATIVE TO ANNUAL AVERAGE, Ang X Her Her X Ang Br-Ang x Her Br-Her x Ang Br x Her Br x Ang McCarter, Buchanan and Frahm, J Anim Sci. 69:3977 (1991) SOURCE: NCAR GIS PROGRAM (STATISTICAL DOWNSCALING OF INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE FIFTH ASSESSMENT RCP 6. SCENARIO, CCSM4) Take Home Message #6 The best long-term solution to heat stress is to use cattle that are genetically-adapted to heat stress Differences between breeds in afternoon rectal temperature in August and December in Florida 15 August Rectal temperature Angus Hereford Brahman Senepol H X S SXH Romo. December Rectal temperature Angus Hereford Brahman Senepol H X S SXH Romo. Hammond et al., J Anim. Sci. 74:295 (1996) SLICK WILD TYPE SLICK SLICK WILD TYPE 4

5 Milk Yield in First 9 Days in Milk for Cows in Summer & Winter N=43 Winter (Oct.-Dec.) Summer (May July) ibutton DS1922L ibutton Temperature Logger Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA 9486 Range: 4 C to +85 C Resolution:.625 C (11 bit) or.5 C (8 bit) C N=18 CIDR 1 inch Vaginal Temperatures in Two Cows August, 215 Alachua County Representative GPS - Angus Vaginal Temperature ( o C) Angus Brahman Infertility Time of Day 5

6 Final Thoughts Magnitude of heat stress effects will vary from herd to herd --greater where high air temperatures, high humidity and high solar radiation predominate, in fescue containing pastures & where there is little shade or water --magnitude of effect depends on the breeding season When heat stress is a problem, fixed time AI is better than AI but ET is best of all --TAI will improve submission rate but not fertility --ET will prevent heat stress effects on fertility Genetics is the best way to solve effects of heat stress --new genetic techniques may mitigate increased risk from heat stress due to global climate change PJ Hansen hansen@animal.ufl.edu Heat Stress Inhibits Expression of Estrus Monty and Wolff, 1974 Thatcher and Collier, 1986 Effect of Milk Yield on Seasonal Variation in Pregnancy Rate in Lactating Dairy Cows Florida South Georgia 9 day non-return rate J F M A M J J A S O N D Month <1, lb 1,-2, lb >2, lb Body Temperatures at Which Cows Experience Declines in Production and Reproduction Grazing Endophyte-Infected Pastures Reduces Fertility Only During the Hot Season (Arkansas/Gelbvieh x Angus) Aug breed/may calving Feb breed/nov calving 1 Conception rates decline as afternoon rectal temperatures > 12.2 o F normal rectal temp~ o F The critical vaginal temperatures are ~ 12.5 o F in the PM Calving rate Fall vs spring, P<.5 Interaction, P< Percent of time grazing endophyte pastures Caldwell et al., J Anim Sci 91:465 (213) 6

7 Differences in Calf Crop for Cows Calving in Fall (Sept-Nov) vs Spring (Feb-April) in Oklahoma (Hot) (Cool) Battisti and Naylor, Science 323: 24 (29) Spring calving group - breeding May-July calving Feb-April Fall calving group - breeding Jan March calving Sept-Nov Delayed Effect of 28 Day Exposure to Heat Stress on Oocyte Competence to Support Blastocyst Development in Gir Cows Control HS Heat stress Torres-Júnior et al., Theriogenology 69: (28) Gene editing to create new genes in cattle These new tools enable researchers to rewrite genes, making targeted changes to an organism s DNA with unprecedented specificity. With the advent of TALENs and CRISPRs, the [GM] landscape is going to change, says [James] Murray [of University of California, Davis]. Jeff Akst, The Scientist, June 1, 214 ibutton DS1922L ibutton Temperature Logger Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA 9486 Range: 4 C to +85 C Resolution:.625 C (11 bit) or.5 C (8 bit) C CRISPRs (clustered regularly interspaced short palindromic repeats) are DNA loci containing short repetitions of base sequences found in eubacteria & archaea. CRISPRs are often associated with cas genes that code for proteins related to CRISPRs. CIDR By inserting a plasmid containing cas genes and specifically designed CRISPRs, an organism's genome can be cut at any desired location. Wikipedia 1 inch 7

8 Average vaginal temperatures for lactating Holsteins on a grazing dairy in Florida during the summer Vaginal temperature ( o C) Temperature, o F Infertility Irrigation pivot milking Hour of the Day Vaginal temperatures are about.2-.4 o F higher than rectal temperatures 8