Caleb Lemley, Mississippi State University Aug. 20, 2019 2019 ARSBC, Knoxville, Tenn. 1 Managing the pregnant female – fetal programming Caleb O. Lemley, PhD Department of Animal and Dairy Sciences, Mississippi State University Developmental Programming • The process through which a stimulus or insult establishes a permanent response • Developmental programming hypothesis • Exposure during a critical period in development may influence later metabolic or physiological functions in adult life Phenotype Classic Animal Breeding Example Phenotype = Genotype + Environment Eg. Milk production = Holstein genetics + Mastitis Phenotype Future Animal Breeding Example Phenotype = Genotype + Environment Eg. Yield grade = Angus genetics + Uterine environment “Farmers, ranchers and animal scientists know more about how nutrition affects fertility in cows, pigs and other commercially important animals than fertility experts know about how it affects reproduction in humans. There are small hints scattered across medical journals, but few systematic studies of this crucial connection in people” 1999 2002 2010
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Caleb Lemley, Mississippi State University Aug. 20, 2019
2019 ARSBC, Knoxville, Tenn. 1
Managingthepregnantfemale– fetalprogrammingCaleb O. Lemley, PhDDepartment of Animal and Dairy Sciences, Mississippi State University
DevelopmentalProgramming• The process through which a stimulus or
insult establishes a permanent response
• Developmental programming hypothesis• Exposure during a critical period in
development may influence later metabolic or physiological functions in adult life
“Farmers, ranchers and animal scientists know more about how nutrition affects fertility in cows, pigs and other commercially important animals than fertility experts know about how it affects reproduction in humans. There are small hints scattered across medical journals, but few systematic studies of this crucial connection in people”
1999 2002 2010
Caleb Lemley, Mississippi State University Aug. 20, 2019
2019 ARSBC, Knoxville, Tenn. 2
Livestock• Developmental programming known for decades prior to
epidemiological studies in humans. • How does developmental programming negatively
impact animal agriculture?• If we fully understand the process, could we develop
positive interventions to impact agriculture?
• Rationale: Majority of mammalian livestock used for meat production spend 30% of their life within the uterus being nourished solely by the placenta.
0102030405060708090
100
Percent Time in Each Phase of Beef Production from Conception to Harvest
In Utero (33%)
Nursing (28%)
Stocker (18%)
Finishing (21%)
Developm
ental Plasticity
Womb
Tomb
Percentage of total lifetime in each phase of beef productionfrom conception to harvest (womb to tomb). Nearly a third oflife is spent developing in utero when the fetus is mostvulnerable to the environment because of increaseddevelopmental plasticity.
10principalsofDevelopmentalProgramming1) During development in the womb, there are critical periods of vulnerability to suboptimal conditions.
Vulnerable periods occur at different times for different tissues.
Major Results:1.) Birth weight: by 7% in progeny born to RES 2.) Mortality rate: (10% in RES; 3% in ADQ)3.) Weaning weight: by 8% in progeny born to RES4.) Puberty of heifer progeny born to RES by 19 days
Milk production was not different between two groups; progeny programmed in utero…
• Early nutrient restriction model for Southeast• Beef producers opting for low-input, forage-based
replacement heifer management programs • 2 Groups of Replacement Heifers (replicated Spring
& Fall)• Low-Input (LOW): ~ 50% of expected mature BW at
breeding• Conventional (CON): ~ 65% of expected mature BW at
breeding
• At 45 days post-breeding heifers were comingled with adequate nutrition
HeiferDevelopmentResults• No change in late term uterine blood flow, fetal growth, and
birth weight. • Ideally, LOW heifers had compensatory changes to uterine
blood flow…
Cain et al. 2017. Theriogenology. 87:9.
• Calf weaning weight decreased by 38 lb in LOW vs CON.
• Spring heifers had increased uterine blood flow, birth weights, and weaning weights compared to fall calving heifers.
TimingisEverything(Mid)
Lemley et al. 2018. J Anim Sci. 96:4823.
• Do we need to supplement feed ($) during an early to mid pregnancy nutrient restriction? • Will breed influence this “programming” response?
• Angus and Brahman heifers were randomly assigned to 100% (CON) or 60% (RES) nutrient requirements from days 50 to 180 of gestation.• Re-alimented to adequate fed from day 180 to term.
Caleb Lemley, Mississippi State University Aug. 20, 2019
2019 ARSBC, Knoxville, Tenn. 4
BloodFlowandFetalSizeLemley et al. 2018. J Anim Sci. 96:4823.
Re-alimentationofFeedBirth Weights Not Different
Weaning Weights Not Different
Hearth Girth in Restricted
From Birth à Weaning
AlternativeTherapeutics• Can we use dietary supplements (antioxidants) to
improve postnatal growth? • Melatonin is a strong antioxidant and hormone of
nighttime • Cost effective for producers• $0.02/head/day (purchased as powder)• $1.80/head to cover last third of pregnancy (90
days)
ExperimentalDesign• Holstein heifers were bred in January 2013 using
sexed semen. • Trained to Calan feeding system at 170 days of
gestation (June of 2013; heat index on the rise!).• Dietary treatments applied from d 190 of gestation
until d 262 of gestation (20 mg of melatonin or no melatonin) • Average gestation length was 275 ± 2 d.
DairyHeiferResults
Brockus et al. (2016)
DietaryMelatoninvsImplants• 32 heifers and 25 cows confirmed pregnant to TAI,
predominantly Angus breeding crossbreds.• Cattle were treated with 2 subdermal ear implants
containing 24 mg of melatonin each. • Implants were administered every 30 days, occurring
on day 180, 210, and 240 of gestation. The last implant was expected to provide melatonin until day 270 of gestation.
Caleb Lemley, Mississippi State University Aug. 20, 2019
2019 ARSBC, Knoxville, Tenn. 5
BeefCowResultsMcCarty et al. (2018)
CCR in MEL
BMI in MEL
Longer and Leaner Calves
P - valueItem CON MEL SE TrtBody weight, lb 431 488 16 0.006Scrotal circumference, cm 18.7 19.6 0.4 0.032
BullCalfMeasurementsat195days(weaning)
McCarty et al. (2018)
Range P - valueItem CON MEL SE MIN MAX TrtSpermatozoa x 106/mL 386.9 357.2 19.3 281.9 458.6 0.148Motility
• Fall vs Spring calving heifers experiencing nutrient restriction and melatonin supplementation during late pregnancy. • Timing of melatonin supplementation during bull
development (in utero, pre-weaning, post-weaning). • Southeast model (T. Smith): Fall calving Angus with
early (May or before) hair shedding weaning heavier calves.
Conclusions• Insufficiencies during pregnancy, resulting in
reduced fetal development, are detrimental to beef cattle production • The timing of nutrient supplementation should be
considered relative to stage of pregnancy• First 3 months, Middle 3 months, and Last 3
months• Increased uterine blood flow during last 3 months
increased weaning weight and may improve bull development
Acknowledgments&Funding• MSU-Faculty
• Derris Burnett• Brian Rude• Heath King• Richard Hopper