1. Nutrition Programs for Growing Heifers José Eduardo P. Santos VMTRC

2. Goals of a Nutrition Program for Growing Heifers 1. Achieve puberty and sexual maturity early 2. Achieve adequate body weight, height, and frame size at calving 3. Decrease age at first calving with adequate body size, without compromising mammary development and lactation performance 4. Economically sound

3. Feeding Program for Growing Heifers  Divided into: Preweaning feeding program Prepubertal feeding program Postpubertal feeding program

4. The Dairy Production Cycle Maternity Pen Calf Hutch/Calf pen Group Pens Weaning Breeding Age Heifer Bred heifer Springing Heifer Fresh High Group Medium Group Low Group Far-off dry cows Close-up dry cows

5. Target Growth for Holstein Heifers  Prepubertal period: 3 to 9 months BW gain: 1.6 to 1.8 lbs/d Wither height: 1.4”/month  Breeding period: 13 months BW: 780 lbs 49 to 50” wither height BCS: 3.0 - 3.5

6. Postpubertal Period  10 months to calving BW gain: 1.8 to 2.0 lbs/d Wither height: 0.5 to 0.6”/month  Prepartum (22 - 24 months): BW: 1350 to 1400 lbs pre-calving or 1200 lbs after calving Height: 54-56” at the withers BCS < 4.0 at calving (3.25 - 3.75)

7. Heifer Weight in Herds with Different Production Levels (Heinrichs and Losinger, 1998)

8. Lactation Performance  Intrinsic factors that affect milk production during first lactation: Number of milk secreting mammary cells (Tucker, 1981) Genetics Mammary development during the allometric phase (Sejrsen and Purup, 1997) Ability of the animal to compete for feed and to deliver nutrients to the mammary gland Body size

9. Mammary Gland Development  Four Phases: Fetal life: Basic structure: stroma, circulatory system, and few ducts Isometric: first 60 to 90 days of life Gland grows at the same rate of the body: stroma and blood vessels Allometric: 3 to 9 months (puberty) Gland grows at a faster rate than the rest of the body: fat pad and ducts (Sinha and Tucker, 1969) Determines the number of milk-secreting cells that will be present during lactation Isometric: After puberty

10. Two Schools  European (Danish): Kris Sejrsen and colleagues Accelerated growth rates during the allometric phase is detrimental to mammary development and milk yield potential  American : M. VanAmburgh, M. VandeHaar and others Negative effects of accelerated growth rates during the prepubertal period can be overcome by diet formulation

11. Danish Data  Growth rates above 1.6 lbs/d during the prepubertal period: Reduce parenchymal DNA in the mammary gland Decrease milk production during first lactation (10 to 20% lower) Mechanism: not clear, but seems to be associated with reduced sensitivity of mammary cells to IGF-I

12. Effect of Prepubertal Feeding Level on Milk Production (Hohenboken et al., 1995)

13. Effect of ADG During Puberty on Mammary Gland Secretory Tissue Ratio CP/ME < 55 g CP/Mcal ME

14. Effect of ADG During Puberty on Mammary Gland Secretory Tissue Ratio CP/ME 55 83 8968

15. Effect of Prepubertal ADG on Performance During First Lactation (Van Amburgh et al., 1998) a ab b a b a,b P < 0.05 CP:ME = 62.3, 66.7, 63.5 g/Mcal

16. Recommendations  Formulate diets to achieve and ADG of 1.7 to 1.8 lbs/d  Adjust CP content of the diet  Ratio CP to ME: 64 g/Mcal  Hoffman (1998) suggested that protein quality may be an issue. However, response to RUP sources is not consistent in growing heifers Maximize microbial protein

17. Data from Cornell University (Elrod and Butler, 1993) Excess degradable protein in diets of breeding heifers might decrease conception rates CP : 21% RDP = 82.5% of CP CR dropped from 82 to 60%

18. Effect of Ionophores on Rumen Bacteria (Gram +)  ExtracellularIntracellular  ATP  H + H + ADP  H + H +  K + K +  Na + Na +  H + H + M M

19. Rumen Fermentation CHO Protein Microbial Protein + NH3 Glucose Pyruvate Propionate Acetate + Butyrate CO2 + CH4 + H2

20. Use of Ionophores in Diets for Growing Heifers  Control coccidiosis  Ionophore-resistant bacteria (Gram - ) produce more propionate and less acetate Increase efficiency of energy utilization  Reduce DMI  May or may not increase ADG  Increase feed efficiency  May reduce age at puberty

21. Influence of Ionophores on Performance of Growing Cattle (167 trials with 11,414 animals) Lanna (1997)

22. Guidelines for Feeding Growing Heifers  Adjust energy content of diets to promote an ADG of 1.7 to 1.8 lbs/d  ME content of the diet 1.0 to 1.2 Mcal/lb of DM  NEg: 0.40 to 0.45 Mcal/lb of DM  Energy requirements for breeding heifers: Maintenance: 780 lbs = 14 Mcal/d 1 lb of gain is equivalent to 4.3 Mcal of ME

23. Guidelines for Feeding Growing Heifers  Limit CP to no more than 16 or 17% for heifers with BW greater than 300 lbs  Maintain a CP:MP ratio of 64 g of CP for every Mcal of ME  Add Ionophores to the diet: Monensin: 200 to 300 mg/hd/d or 20 to 30 ppm Lasalocid: 200 to 300 mg/hd/d or 20 to 30 ppm

24. Prepartum Heifers  Feed a high energy low NDF diet NEL: 0.72 to 0.75 Mcal/lb NDF: 32 to 35% NFC: 38 to 42%  Use high quality forages (Corn silage)  Avoid ingredients with high fat content dietary fat < 3.5%

25. Prepartum Heifers  Keep CP at 14 to 15% during the last 3 to 4 weeks prepartum  Close-up heifer group should be consuming 22 to 25 lb of DM/hd/d (1.6`- 1.7% of BW)  Feed a low Na and K diet to minimize udder edema

26. Cost of Feeding Replacements  California (1999 - 2000) 4 to 12 months: $ 100.00 to 120.00/ton DM 13 to 23 months: $ 80.00 to $ 95.00/ton DM