Heifer Development OSU Beef Team Growing Phase Lesson 4

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 mo to calve as 2-yr-olds

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.

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

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

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

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)

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

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.

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

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

Target weights and gain for developing replacement heifers Stage of developmentAge, months Target weight, lbs % of mature Target gain Lbs/day Weaning Period Post-weaning to breeding Breeding to calving Calving to rebreeding nd breeding nd calving

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

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

Dry matter intake required for a 600 lb heifer Gain, lbGrass hayCorn silage90% grain NW NW 23.6?14.5

Limit-fed corn for replacement heifers ItemCorn silage- hay Limit fed corn Initial wt, lb Final wt, lb Gain, lb/d DMI, lb/d Concentrate Silage Hay Conception, %8390 Calving date3/53/4

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

Effect of winter nutrition level during heifer development on subsequent performance of replacement heifers Grain, lbs/hd/ day # of heifers Initial Weight, lbs ADG, winter period, lbs Breeding wt., lbs % bred as yearlings (60 days) % rebred WWT first calf, lbs

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

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

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

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

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

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.

Minerals Also see page 24

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

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

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