Development of Replacement Heifers

1. Development of Replacement Heifers Oklahoma Cooperative Extension Service Oklahoma State University

2. Cow Herd Reproductive Efficiency Impacts Annual Gross Income • Fertility 5 times more important than growth rate. • Growth rate twice as important as carcass characteristics. • Infertility 5 times more important than respiratory diseases in affecting profitability within beef cattle industry.

3. Heifer Management is the CornerStone of Cow/Calf Production • Heifers are expensive whether raised or purchased. • Management of first-calf heifers affects lifetime productivity. • Lower rebreeding rates for heifers (as a group) considered normal through 2nd calf.

4. Heifer Management is the CornerStone of Cow/Calf Production (continued) • Heifers have unique challenges compared to mature cows. • Uniform calf crops begin with controlled breeding seasons and well developed heifers.

5. How Many Heifers Should I Keep?

6. Replacement Heifer Numbers • Match numbers to available resources. • North Dakota State University research suggests replacement rate for “typical” cow herd is 17%. • Previous research indicates one-half of heifers reaching 55% of mature weight were cycling by first breeding season. • Ninety percent of heifers will be cycling by first breeding if they reach 65% of their mature weight prior to breeding. • Research suggests saving 10-50% more heifers to breed than the producer thinks he will need.

7. Avoid Excessively Fat Heifers • More of a problem in purebred, seed stock, and herds using dairy stock as recipients of ET calves. • Excessively fat heifers can have reduced milking ability during their lactation. • Monitoring body condition on heifers can prevent the problem. • High protein creep feed (Oklahoma Silver), and post-weaning supplement (Oklahoma Gold) can increase weight gain without “over conditioning”

8. Replacement Heifers and Implants • Not recommended for “designated” replacement heifers. • No decrease in dystocia in implanted heifers compared to non-implanted heifers. • Some studies indicated a slight reduction in fertility. • Implanting at birth or close to puberty reduced reproductive performance • Implanting younger and lighter heifers once at 2-4 months of age will not reduce reproductive performance. • Do not reimplant heifers selected to be bred.

9. Immunization Strategies • Blackleg, and Malignant Edema vaccines at 2-4 months of age. • Brucellosis vaccine at 4-10 months of age. • 3-4 weeks prior to weaning and/or at weaning: IBR, BVD, PI3, 7-8 way Clostridial, Leptospirosis, Campylobacter, and deworm. Consult local veterinarian on detailed vaccines recommended for your area.

10. Immunization Strategies(continued) • Booster vaccines should be given 3-4 weeks following the first round of injections. • Yearling booster vaccination with BRD vaccines (if using a modified live virus vaccine, and then annual Lepto. and Campylobacter injections 30 days prior to breeding.

11. Weaning to Breeding Issues • Most heifers weaned at 7-10 months of age, weighing from 350-650 pounds. • Size, age, and extra nutritional demands suggest that heifers should be separated from mature cows and fed to gain 1.25-1.5 pounds per head per day. • If there is considerable variation in weight and age of heifers, divide them into smalls, and larges, and feed separately to gain appropriately.

12. Weaning to Breeding Issues(continued) • Puberty is affected by age, weight, breed and adverse environmental stresses. • Heifers must attain 65% of their mature weight by their first breeding season to be cycling, and breed successfully.

13. Growing Programs Research • “Timing” of gain research conducted independently by KSU, and OSU show similar results. • KSU researchers gained heifers at 0.55 lb. per day for first 5 mos., then 2.5 lb./day for last 2 mos. with reproductive performance results equal to heifers gaining 1.31 lb. per day for the entire 7 mos., and on 12% less feed. • OSU researchers gained heifers at 0.6 lb./day over the winter, and then 1.92 lb./day in the spring and showed that those heifers reached puberty 20-30 days sooner than the control heifers which were gained at a continuous rate over the entire feeding period.

14. Wheat Pasture Growing Program (pre-breeding) • Heifers will gain 1.5 lb/day over the winter grazing period. • They will be ready to breed in April or May. • Set aside “graze-out” patch to get heifers to breeding season and avoid severe weight loss when pulled off wheat pasture.

15. Wheat Pasture Growing Program (post-breeding) • Allow bred heifers limited access to wheat pasture such as every other day, or 1 day on and 2 days off. • Limiting access of wheat pasture for bred heifers will help prevent over-conditioned heifers and possible dystocia problems at calving.

16. Ionophores in Growing Programs • Monensin, and Lasalocid feed additives approved for growing programs for replacement heifers. • Texas and Wyoming research indicates that heifers consuming 200 mg. of Monensin per head per day reached puberty at an earlier age than heifers not consuming Monensin in feed supplements. • Stocker cattle gains are increased by 0.1-0.2 lbs. per head per day when fed 100-200 mg./hd/day of an ionophore in feed supplements. • Heifers would gain an additional 15-30 lb/hd over a 150 day growing period.

17. Culling Decisions after Breeding • Pregnancy test heifers 60 days after removing the bulls. • Cull all open heifers immediately after testing. • Lifetime studies show 55% reproductive rate for sub-fertile heifers that failed to conceive after their first breeding season. • Immediate culling will reduce the winter feed bill. • Immediate culling will allow marketing them as feeder heifers at higher market prices (age/perceived public health issues, etc.)

18. Body Condition at Calving • Research proves those cows that maintain adequate body condition to calving, return to estrus sooner than cows that lost considerable condition prior to calving. • Body condition scoring (1 to 9 system) is more accurate in estimating stored energy reserves (fat) than weight measurements. • BCS accounts for 85-91% of the variation in stored body energy in cows, and can be easily used to monitor changes in body condition to facilitate management practices such as sorting, supplementation, etc. • Cows in thin body condition at calving return to estrus slowly, usually not in time to calve within a year.

19. What About Thin Heifers at Calving? • OSU study divided 81 heifers into 2 groups in November: 1 group lost body condition until calving, the other maintained body condition until calving. • At calving they were further divided to either (1) gain weight and body condition postpartum, or to maintain body condition postpartum.

20. Thin Heifers at Calving (continued) • Thin heifers at calving which were allowed to gain weight and condition through breeding had a rebreeding rate of 66%. • BCS 5 or better heifers at calving which were allowed to maintain condition through breeding had a rebreeding rate of 91%.

21. Thin Heifers (continued) • Heifers fed to maintain weight and condition postpartum to breeding received 4 lb./hd./day of cottonseed meal at $0.13/lb. for 69 days for a total cost of $36 per head. • Heifers fed to gain weight and condition received 28 lb./hd./day of a 12% CP grain mix at $0.073/lb. for a total cost of $141. • The improvement in reproductive rate (66% vs. 36% pregnant) of the thin heifers was not enough to offset the feed expense. • The results of this study concur with numerous other university experiment station studies.

22. Thin Cows (continued) • The data shows young cows that calve in thin body condition (BCS 3 to 4) cannot gain enough body condition postpartum to match the rebreeding rates of moderately conditioned (BCS 5.5) cows that maintain or lose very little condition postpartum.

23. Thin Cows (continued) • Cows must be rebred by 85 days postpartum to calve again the same time next year. • None of the cows in thin condition recycled in time to maintain a 12 month calving interval.

24. Sorting Heifers from Cows • First calf heifers are usually the most difficult to get rebred for reasons such as growth requirements, calving, lactation, involution and repair of the reproductive tract, limited dentition, and rebreeding. • They are additionally subjected to “bossing” and abuse by larger, mature cows when fed together, and cannot gain on the lower quality forage the mature cows consume.

25. Sorting (continued) • North Dakota State U. researchers recorded age and weight distribution of commercial cow herds over a 21 year period to illustrate the differences in sizes by age of the “typical” cow herd. • To provide heifers a chance to achieve the same reproductive efficiency as the mature cows, they often need to be sorted off to themselves and treated separately as a group

26. Summary • Properly immunize heifers at 2 months, weaning, and at 1 year of age according to a veterinarian’s recommendations. • Heifers must reach 65% of their mature weight by the start of the breeding season. • The most economical growing program for replacement heifers is going to utilize standing or harvested forages as a major portion of the diet. Heifers may be grown slowly then given higher energy feed to accelerate the rate of gain to achieve the required 65% of mature size by the start of the breeding season

27. Summary (continued) • Utilize the highest quality hays and/or the best pastures because young cattle cannot utilize low quality roughage as well as the mature cows. • Use an ionophore to improve feed utilization and hasten the onset of puberty. • Breed replacement heifers 3 to 4 weeks ahead of the adult cows.

28. Summary (continued) • Cull all open heifers after the first breeding season. • Grow bred heifers adequately so that they are in the body condition score 6 at calving time. • Sort young cows (2 and 3 year olds) from older cows to insure adequate feed intake for young, growing, but smaller cows.