Developing Heifers Earl H. Ward

What are the Goals? Start Cycling Early Calve at age of 24 Months Prefer to calve in the first 21 days of calving season Rebreed quickly Longevity in the Herd

Puberty Ideally – heifers reach puberty about 60 days prior to the beginning of the breeding season Increases chances of becoming pregnant and calving earlier in the season Inverse relationship between postweaning growth and age at puberty Age @ Puberty Postweaning Average Daily Gain

Nutrition Plane of nutrition influences reproductive performance in heifers and cows Delayed Gain = Lower Feed Cost with no adverse affect on pregnancy performance Can’t Have Production without Reproduction Can’t Have Reproduction without Nutrition

Dry Lot vs Pasture Dry lot is a “false” environment Heifers developed in a dry lot, then turned out for breeding will have a period of weight loss, potentially due to re-learning grazing skills SDSU research (Perry et al., 2013) Drylot = -3.5 lbs/d ADG for first week Range = 2.0 lbs/d ADG for first week 27 Days later = no difference in ADG

Pelvic Area Calving difficulty results in major economic loss to the beef cattle industry. Estimated losses resulting from dystocia equal or exceed $750,000,000 annually. David J. Patterson and William O. Herring - University of Missouri Using pelvic measurements to estimate deliverable calf size (birth weight) Time of measurement Heifer age Heifer weight Pelvic area Pelvic area per birth weight ratio Estimated calf birth weight Before breeding 12-13 months 600 pounds 140 cm2 2.1 67 pounds 160 cm2 76 pounds 180 cm2 86 pounds Pregnancy exam 18-19 months 800 pounds 2.7 200 cm2 74 pounds 220 cm2 82 pounds

Reproductive Tract Score Rectal Palpation or Ultrasound

Heifer Size @ Breeding Decades of research set the guidelines of 60-65% of mature weight Results have changed over time BW has less impact now due to: Shift from calving at 3 yo to 2 yo Selection pressure on age of puberty (scrotal circ) New Recommendation is 55-65% (Funston – University of NE)

Heifer Size @ Breeding 55% 60% 65% 1000 550 600 650 1100 605 660 715 1200 720 780 1300 845 1400 770 840 910

Timeline Birth Weaning Breeding Calving 6-7 Months @ 7-8 Months

Questions? Ho Heifers