1. Heifer Development OSU Beef Team Growing Phase Lesson 4

2. Puberty (age, weight, breed) When they 1 st ovulate and show an estrus or heat period Heifers born early in the calving season are usually heavier at weaning and reach puberty earlier than late-born calves Heifers must reach puberty at 13-14 mo to calve as 2-yr-olds

3. Puberty occurs at about 60-65% of mature body weight Conception is higher on the 3 rd estrus than the 1 st estrus Therefore, should cycle at least once before breeding season.

4. Weight at Puberty Recent research has suggested that development of heifers to 50 to 57% of mature body weight may present an economic advantage over developing heifers to 60 to 65% of mature body weight (for review see Endecott et al., 2013). However further research is necessary to assess the relative effects of these two strategies on cow longevity and economic efficiency. Endecott et al., 2013

5. The following weights should be attained about a month prior to breeding: Frame Score 13579 Estimated Weight at 1 st estrus, lbs 580623728803880

6. Puberty and Scrotal Circumference Bulls with larger scrotal circumference sire heifer that reach puberty at an earlier age. In those breeds that have a scrotal circumference EPD, breeders should use them to improve age at puberty

7. Age at puberty can be decreased 3 ways By selecting a breed with younger age at puberty By selecting within a breed for younger age at puberty By crossbreeding with another breed that has a similar or younger age at puberty (hybrid vigor)

8. MARC data on puberty (1 = earlier, 5 = later) Jersey1 Holstein2 Gelbvieh2 Hereford-Angus3 Simmental3 Limousin4 Charolais4 Chianina4 Brahman5

9. Bull Exposure & Puberty Exposing heifers from weaning to breeding to surgically altered (gomer) bulls can reduce age at puberty days. However, results have been variable.

10. Target Weight Concept Heifer Weighs 450 lbs Puberty likely at 675 lbs Have 160 days to grow (2 cycles before breeding) (675-450)/160 = 1.4 lbs of gain/day However, gain need not be constant

11. Ideally Weigh every 30 to 60 days If can’t weigh all, 10-20% representative of the group

12. Target weights and gain for developing replacement heifers Stage of developmentAge, months Target weight, lbs % of mature Target gain Lbs/day Weaning Period 8450411.75 Post-weaning to breeding 9500451.25 Breeding to calving 1468462.8 Calving to rebreeding 2388080.4 2 nd breeding 2792784.4 2 nd calving 36101292.2

13. Feeding Heifers Most economical are high forage rations supplemented with grains, grain by- products, protein concentrates, minerals and vitamins

14. Energy Requirements from Weaning to Breeding (14 months) Target gain 1.5 – 2.0 lbs/d Free choice hay + supplement.5 to 1% BW from supplement Corn, soyhulls, byproducts Corn silage + 5 lbs hay (~ free choice) Limit-fed grain

15. Dry matter intake required for a 600 lb heifer Gain, lbGrass hayCorn silage90% grain 010.46.65.5 1.118.310.68.6 1.7 NW17.111.5 2.2 NW 23.6?14.5

16. Limit-fed corn for replacement heifers ItemCorn silage- hay Limit fed corn Initial wt, lb578574 Final wt, lb860844 Gain, lb/d1.681.61 DMI, lb/d16.412.0 Concentrate--10.2 Silage13.2-- Hay3.11.7 Conception, %8390 Calving date3/53/4

17. Other Example Rations Page 22 Notice how forage quality affects rations Nutrient requirements on page 21

18. Effect of winter nutrition level during heifer development on subsequent performance of replacement heifers Grain, lbs/hd/ day 02.75.4 # of heifers112113112 Initial Weight, lbs496502493 ADG, winter period, lbs0.070.500.80 Breeding wt., lbs506577613 % bred as yearlings (60 days)69.273.983.5 % rebred67.375.487.1 WWT first calf, lbs405433443

19. Individual Weight Versus Group Weights If a group of similar breed-type heifers averages 650 lbs, some may only weigh 500 lbs. Heifer born in a short calving season with have less variability Deworming may improve uniformity Do you have adequate bunk space? Wide variation – feed in 2 groups One set fed for higher rate of gain

20. Heifer Weight Ranges at Weaning (60 day calving season) 2.5 lb/d × 60 d = 150 lbs difference Growth and milk production genetics = 100 lbs difference Total = 250 lbs

22. Feeding Strategies Large group, split them Use of commercial formulations Don’t forget mineral/vitamins

23. Mineral Requirements Mineral supplementation is needed year-round (every day)!

24. Major Mineral Deficiencies Phosphorus Magnesium (in Spring) Sodium chloride (salt) Trace minerals (especially Selenium and Copper) Calcium (if grain more than 10 lbs/day)

25. OARDC Mineral Mix abc % TM Salt33.02 Dicalcium phosphate25.00 Mag Ox25.00 Limestone6.90 Ground corn10.00 EDDI.08 a Target intake of 3 oz/day. Keep dry, place near water or loafing area. Replenish once/week. b Commercial mineral mixes + Vit. A and E. c Selenium injection at birth if WMD problems.

26. Minerals Also see page 24

27. Vitamin Requirements No dietary requirements for B vitamins Vitamin D synthesis from sunlight A and E present in fresh forage; depleted over time in hay Supplement (mineral mix) or injectable pre-calving if repro problems

28. Water Requirements Lack of water decreases feed intake Cattle do not readily consume frozen water Cattle do not readily consume hot water Cattle do not readily consume shuddy water

29. Cost of production through growing phase $400-$550?