Heat Stress During LactaBon. Why Dry Cow Heat Abatement Is So Key. What about dry cows? Heat Stress Effects on Yield Linger 11/6/17

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1 Heat Stress During LactaBon Why Dry Cow Heat Abatement Is So Key G. E. Dahl Department of Animal Sciences InsBtute of Food and Agricultural Sciences GPS Leaders Forum 16 November 217 Depresses DMI Reduces milk yield Recent studies suggest addibonal metabolic effects beyond DMI Recovery dependent on durabon What about dry cows? Milk yield? Metabolism? Immune funcbon? Heat Stress Effects on Yield Linger Late gesta(on DAM vs. DAUGHTER Cow performance? ThermoregulaBon? Calf health? Calf growth? Heifer growth? ReproducBon? Tao & Dahl, J. Dairy Sci. 96:

2 Study Design: Heat Load of Dry Cows Temperature Humidity Index higher than 72 throughout the day June 4th to O ctober AVG TH I 8 T H I Thresholds H o u rs Do Amaral et al., J. Dairy Sci. 94: Heat Stress Increases Mean Rectal Temperature Morning Treatment Effect; P<. Time a b Afternoon Heat Stress Dry Cows Increases Milk Milk Production, kg/d Weeks in milk Do Amaral et al., J. Dairy Sci. 94:86 96 Tao et al., J. Dairy Sci. 94:

3 Dry Cows Increases Milk 4 Heat Stressed Cooled Milk ProducBon 4 Milk, kg/d 3 2 Epithelial Cell Metabolism + Epithelial Cell Number 1 1 Collier et al., 1982 Wolfenson et al., 1988 Avendaño-Reyes et al., 26 Adin et al., 29 do Amaral et al., 29 do Amaral et al., 211 Tao et al., 211 Thompson et al., 212 Tao et al., 212 Thompson et al., 214 Fabris et al., 217a Fabris et al., 217b Milk ProducBon Increased ProliferaBon of Mammary Cells Prepartum (d-2) Epithelial Cell Metabolism + Epithelial Cell Number Cell Growth Cell Death Ki67 labeling, % * **.. Epithelium Stroma Total Tao et al., J. Dairy Sci. 94:

4 TUNEL labeling, % Heat Stress During Dry Period No Effect on MEC Apoptosis Epithelium Heat Stress Reduces DMI Prepartum But Not Postpartum DMI (kg/d) Treatment effects: Prepartum P =.3 Postpartum P =.9! Heat Stress Days relative to calving Days relative to calving Tao et al., J. Dairy Sci. 94: Tao et al., J. Dairy Sci. 94: Dry Cows Increases BW Prepartum, Decreases Postpartum Effect of Dry Cows on Metabolic Profile Thompson et al., J. Dairy Sci. 97: Tao et al., J. Dairy Sci. 9:-46 4

5 Dry Cows Increases Lymphocyte ProliferaBon Dry Cows Effects on Acquired Immunity Do Amaral et al., Domest. Anim. Endo. 38:38-4 Do Amaral et al., J. Dairy Sci. 94:86 96 Dry Cows Increases Neutrophil AcBon Postpartum Dry Period Duration Do I have to cool cows the entire dry period? Can I just cool during the close-up phase? Do Amaral et al., J. Dairy Sci. 94:86 96

6 Heat stress increases Rectal Temperature and Rate Week 1 3 Before Switch Heat Stress Increases Rectal Temperature and Respira@on Rate Week 4-6 A]er Switch Heat Stress Decreases Gesta@on Length and Dry Period Length at Any Time Heat Stress Imposed at Any Time in the Dry Period Reduces Milk Yield P =. P <. P <. P =. P <. P <. Milk yield, kg/d P P <. 6

7 - Decreases milk yield - No prepartum metabolic effect - Reduces immune funcbon 4 Increases Calf Birth Weight Treatment effect: P <.1 Late gesta(on Calf health? Calf growth? DAM vs. DAUGHTER Heifer growth? ReproducBon? Cow performance? ThermoregulaBon? Birth Weight, kg kg 42.4 kg 2 Tao et al., J. Dairy Sci. 9: Heat stress Weaning BW, Kg BW Change, Kg Weaning Weight Heat stress Tao et al., J. Dairy Sci. 9: P =.4 Heat stress Total IgG (mg/dl) Improves Total IgG and AEA 3, 2 Heat Stress 1 2, Heat stress 2, 1, 1, Tao et al., J. Dairy Sci. 9: Days of Age AEA, % 4 3 7

8 Why Does Affect AEA? Calf or Colostrum Effect? Experiment 1 - In utero heat stress for ~6 weeks reduces body weight and height to weaning Monteiro et al., J. Dairy Sci. 97: Monteiro et al., J. Dairy Sci. 97: Increased Apparent efficiency of IgG absorption (AEA*) 3 trt: P <. Experiment 2 No Effect of Colostrum from Cooled or Heat Stressed Cows on Calf Performance AEA, % % 26. % Heat Stress * AEA = [Serum [IgG] (g/l) * birth weight (kg) *.91 / IgG fed (g)] x 1 Monteiro et al., J. Dairy Sci. 97:

9 11/6/17 In Utero HT Accelerates Gut Closure Heat Stress Summary Short Term Effects on Calves increases weight at birth and weaning In utero heat stress reduces apparent efficiency of IgG absorpbon, but not an effect on colostrum quality In utero heat stress alters carbohydrate metabolism, consistent with greater fat deposibon Ahmed et al., J. Dairy Sci. 99: analysis of records of calves from studies between 27 and 211 Monteiro et al., J. Dairy Sci. 99: Heat Stress Experiments Bulls Heifers Total Heat Stress Total 9

10 Birth Weight, kg Monteiro et al., J. Dairy Sci. 99: Birth Weight 44.8 kg 39.1 kg Heat Stress trt: P <.1 gender: P =.2 In Utero Heat Stress Decreases Calf Bodyweight to Puberty Body Weight (kg) Heat Stress trt: P <. Monteiro et al., J. Dairy Sci. 99: P = Months of Age In Utero HS Decreases Calf Survival In Utero Heat Stress Decreases ReproducBve Performance Monteiro et al., J. Dairy Sci. 99: Monteiro et al., J. Dairy Sci. 99:

11 kg 42.4 kg Heat Stress /6/17 In Utero Heat Stress Reduces Milk Production In Utero Heat Stress Does Not Affect Mature Bodyweight P =.3 P =.3 Monteiro et al., J. Dairy Sci. 99: Monteiro et al., J. Dairy Sci. 99: In Utero HT Alters Body Temperature Regulation at Maturity Altered autophagy Decreased mammary growth 4 4 Late gesta(on DAM vs. DAUGHTER Milk Production, kg/d Decreased milk yield Weeks in milk Ahmed et al., J. Anim. Sci. 9:In Press. Birth Weight, kg Heat stress Lower body weight Decreased IgG absorpbon Reduced reproducbve efficiency Milk Production (kg) Weeks After Calving Decreased milk yield 11

12 Does it Pay to Cool Dry Cows? Does it Pay to Cool Dry Cows? net present value, $ per cow per year $24. / 11 lbs / $2, $2. / 11 lbs / $1, $2. / 11 lbs / $2, $2. / 11 lbs / $3, $1.4 / 11 lbs / $2, $2. / 6.6 lbs / $2, $2. / 2.2 lbs / $2, Net Present Value, barn needs to be built Heat stress days Does it Pay to Cool Dry Cows? net present value, $ per cow per year $24. / 11 lbs $2. / 11 lbs $1.4 / 11 lbs $2. / 6.6 lbs $2. / 2.2 lbs Net Present Value, no barn Heat stress days 12