1. Cold Weather Feeding Strategies

2. What Influences Calf Growth? Nutrition Health Genetics Environment

3. Biology of Cold Stress Maintaining body temperature requires energy –Cold stress increases maintenance energy reqt Calves have limited capability to regulate their body temperature –Immature metabolism Preruminant – lack of ruminal fermentation –Lack of appreciable fat stores –Must consume enough calories to generate enough heat

4. Thermoregulation Thermoneutral zone –Range where maintenance energy requirements are relatively constant –50-80°F for young calves Lower critical temperature –Temperature at which maintenance energy requirements increase –More energy required to maintain core body temperature, at the expense of growth and immune function From the book The Development, Nutrition, and Management of the Young Calf; Davis and Drackley, 1998

5. Age Effects on Lower Critical Temperature Age Lower Critical Temperature Newborn Calf 50°F Month-old Calf 32°F Dry dairy cow 8°F Calves experience cold stress at moderate temperatures Lower critical temperature decreases with age, greater energy intake, and ruminal development Cattell, 1999

6. Environmental Effects on Critical Temperature Solar Environment Critical Temperature Dry, calm, sunny-7°F Dry, calm, overcast8°F Dry, calm, night22°F Dry, 10 mph wind, overcast 27°F Raining, 10 mph wind, overcast 35°F Housing environment impacts degree of cold stress Key Factors –Free of drafts –Dry –Deep bedding allows for: Insulation Nesting behavior Increased lying time Drier hair coat Cattell, 1999

7. Temperature Effects on Maintenance Energy Requirements Body Weight (lbs) ADG, lbs/day Metab. Energy Mcal/day 20-20 Needed, lbs/day 1000.001.750.84 1000.502.291.10 1000.722.601.25 Body Weight (lbs) ADG, lbs/day Metab. Energy Mcal/day 20-20 Needed, lbs/day 1000.003.251.56 1000.503.811.83 1000.724.101.97 70°F 10°F 85% Increase

8. Impacts of Cold Stress on Calves Deplete body fat reserves –Young calves dont have much anyway! –Can literally starve to death Depressed immune function –Energy not available to fight disease –Poor response to treatment Decreased growth performance

9. Key Management Practices Calf jackets Straw > wood chips or sand

10. Effect of Bedding Type Hill et al., 2007, PAS, 23:656 Straw: 82 lbs of gain thru d 56 Shavings: 73 lbs of gain thru d 56

11. Key Management Practices Calf jackets Straw > wood chips or sand Air quality –As barns get closed up, airborne bacteria may increase – greater respiratory and scours problems –Maintain air flow while eliminating draft Water availability –Offer warm water for 30 minutes twice daily

12. Cold Weather Calf Management Objectives –Exceed maintenance energy requirements and maintain desired growth rates –Focus on young calves <3 weeks old Nutritional strategies –Increase amount of powder 10 12 oz per 2 quarts –Utilize a fat supplement 2 to 4 oz/calf/day –Increase liquid feeding rate 2 2.5 to 3 quarts/feeding –Add a 3 rd feeding 2 quarts/feeding fed 3X

13. Considerations for Strategies Does the farm use bottles or pails? –Bottle size limits how much liquid is fed 2 quart bottles are common 3 quart bottles are available –Will be a factor in what strategy is recommended Key question: Increase energy density, feed more volume, or both?

14. Strategy #1: Increase Solids Percentage Standard mixing rates –8 oz dissolved in 2 quarts fed twice daily (12% solids) –10 oz dissolved in 2 quarts fed twice daily (15% solids) –12 oz dissolved in 2 quarts fed twice daily (18% solids) 18% solids is maximum recommended! –Ability to increase intake is limited w/ this approach –Mix rate of 12 oz/2 quarts is upper limit

15. 100 lb Calf – 20-20 MR 70°F 20-201.251.50 Protein ADG (lb/day)0.720.91 Energy ADG (lb/day)0.721.07 Energy balance, Mcal/d+0.85+1.37 10°F 20-201.251.50 Protein ADG (lb/day)0.720.91 Energy ADG (lb/day) Weight Loss Energy balance, Mcal/d-0.65-0.12 32°F 20-201.251.50 Protein ADG (lb/day)0.720.91 Energy ADG (lb/day) Weight Loss 0.41 Energy balance, Mcal/d-0.09+0.43

16. Strategy #2: Use KCAL (7-60 Fat Supplement) What is KCAL? –7% crude protein, 60% fat supplement How much do we feed? –2 or 4 oz/calf/day How much fat if KCAL is added to a 20-20? –2 oz/calf/day = 24% Fat –4 oz/calf/day = 27% Fat

17. Strategy #2: Areas of Caution, Solids % with KCAL Influence of KCAL on Milk Replacer Solids Percentage KCAL Feeding Rate, oz/day Mixing RateNone2 oz4 oz 10 oz/2 quarts15.0%16.5%18.0% 12 oz/2 quarts18.0%19.5%21.0% Take-Home Message: Increase MR powder mix rate OR add a fat supplement, NOT BOTH

18. Strategy #2: Use KCAL (7-60 Fat Supplement) 10°F 20-20 4 oz/d fat1.25 Protein ADG (lb/day)0.78 Energy ADG (lb/day)0.09 32°F 20-20 2 oz/d fat1.25 Protein ADG (lb/day)0.75 Energy ADG (lb/day)0.28 32°F 20-20 4 oz/d fat 1.25 Protein ADG (lb/day)0.78 Energy ADG (lb/day)0.56 10°F 20-20 2 oz/d fat1.25 Protein ADG (lb/day)0.78 Energy ADG (lb/day) Weight Loss Take-Home Message: 2 oz/calf/day – not enough energy 4 oz/calf/day – recommended feeding level during moderate cold

19. Strategy #3: Increase Liquid Feeding Rate Mixing Rate (oz/2 quarts) Effect of Liquid Feeding Rate on MR Intake (lbs/day) 1.501.252.0 fed 2X 1.8751.562.5 fed 2X 2.251.8753.0 fed 2X 12 oz 10 oz Quarts

20. 100 lb Calf – 20-20 MR 70°F 20-201.251.56 1 1.875 2 Protein ADG (lb/day)0.720.961.20 Energy ADG (lb/day)0.721.151.56 10°F 20-201.251.56 1 1.875 2 Protein ADG (lb/day)0.720.961.20 Energy ADG (lb/day) Weight Loss 0.58 32°F 20-201.251.56 1 1.875 2 Protein ADG (lb/day)0.720.961.20 Energy ADG (lb/day) Weight Loss 0.510.97 1 10 oz powder dissolved into 2 quarts, calves fed 2.5 quarts twice daily 2 10 oz powder dissolved into 2 quarts, calves fed 3 quarts twice daily, or 2 quarts three times daily

21. Strategy #4: Add a 3 rd Feeding of MR Solution Ideal Approach –Spread out feedings –Reduce risk of refusals Implementation Issues –Labor –Inconvenience Feed an extra 1-2 quarts at noon

22. Feeding Program All winter Add KCAL @ 4 oz/calf/day Mix MR @ 12 oz/2 quarts OR Feed an extra 1-2 quarts daily Daytime temp < 20°F Mix MR @ 10 oz/2 quarts

23. Economics Strategy Energy Allowable Gain @ 32°F, lbs/dFeed cost, $/day Cost/lb of gain @ 32°F MR, 10 oz rate, 2 quarts twice daily Weight loss$1.20HIGH MR, 12 oz rate, 2 quarts twice daily 0.41$1.44$3.51 MR, 10 oz + 2 oz KCAL, 2 quarts twice daily 0.56$1.54$2.75 MR, 10 oz rate, 2.5 quarts twice daily 0.51$1.50$2.94 Assumed $0.96/lb for 20-20 MR; $0.085/oz for KCAL fat supplement

24. Conclusions Calves need more calories during cold weather for maintenance, growth, and immune function Focus on housing and bedding will decrease maintenance energy requirements Increasing liquid feed intake and fat supplementation are effective strategies Good calf starter management is key Focus efforts on calves 3 wks old!!!