1. Calving Season and Weaning Management Calving time Calving time –Spring-reasons: 1. Grasses and forages have their highest nutritive value in the spring, and therefore most animals in the wild have their young in the spring 2. Weather more conducive to survival of calves 3. Minimum housing needs 4. More economical to feed dry in winter 5. Tradition in U.S.

2. Calving Season and Weaning Management Calving time Calving time –Fall-reasons: 1. Calves weaned in spring when feeder prices are generally more favorable 2. More steady supply of feeders if also calving in the spring –Regardless of calving season chosen, one should strive to calve within a 40 to 60 period- reasons: 1. More uniform calf crop resulting:

3. Calving Season and Weaning Management Creep feeding: Creep feeding: –Advantages : 1. Increases weaning weights by about 50 lb. 2. Eases the stress on 2, 3 and 4 year old cows 3. Eases the stress on drought-shortened and over populated pasture 4. Lowers the stress on calves at weaning and makes adaptation to feedlot diets easier 5. Fall born calves maintained in drylot substitute creep feed for lack of pasture 6. Prepares calves for early weaning program

4. Calving Season and Weaning Management Creep feeding: Creep feeding: –Disadvantages: 1. Calves may lose some condition if going into backgrounding program following weaning 2. Requires extra labor, equipment, feed and management 3. Not easily adapted to large pastures or range conditions

5. Calving Season and Weaning Management Creep feeds: Creep feeds: –Can start as early as about 6 weeks of age –Many producers start at 3-4 mo. of age (~ July 1 when grass is short) 10-11% salt of total creep DM will limit intake to about 2.5 lb. daily DM intake –Consideration: 1. 1. 2. 2. 3. 3.

6. Calving Season and Weaning Management Creep feed examples: Creep feed examples: 1.All oats – may or may not be processed 2.Cracked corn 62.5 lb Oats 37.5 lb a.b.c.d.

7. Calving Season and Weaning Management Implanting: Implanting: –May improve weaning weight –If implant at birth, may need to reimplant 70 to 100 days later to get full benefit of 50 lb. weight increase

8. Calving Season and Weaning Management Implanting: Implanting: –Concerns: 1. Steer and heifer calves implanted during nursing period, may not respond as well to implants during feeding period – research contradictory on this

9. Calving Season and Weaning Management Implanting: Implanting: –Concerns: 2. Reproduction: a. Bulls implanted as calves suffer at least 50% reduction in testicular size and similar reduction in futility b. Recent research by Montana and Kansas workers has shown no detrimental effects on fertility 1.) Previous research has shown lowered 1.) Previous research has shown lowered conception rates and incidences of fertility c. Conclusion: do not implant nursing calves that are potential breeding stock

10. Calving Season and Weaning Management Early weaning: Early weaning: –Considered to be any weaning age younger than 6 to 7 months –Situations promoting early weaning: 1. 2 and 3 yr. old cows 2. Cows with twins 3. Drought conditions or insufficient pasture 4. Fall calving 5. to accelerate rebreeding in late calving cows

11. Calving Season and Weaning Management Early weaning: Early weaning: –ISU study: Crossbred cows – 42 day. breeding season Crossbred cows – 42 day. breeding season Spring calving = late March through early May Spring calving = late March through early May Fall calving = late August through early October Fall calving = late August through early October

12. Postpartum Estrus Distribution Postpartum interval to estrus (days) Calving Time Weaning Age Fall45%Spring 45 % Spring 200 % 214.51.1.5 4242.014.314.1 6342.562.931.4 849.317.429.4 84+.53.217.3 No heat 1.21.17.3 Total100.0100.0100.0

13. Effect of Season and Age of Calf at Weaning on Reproductive Performance of Cows Calving Time Weaning Age Fall45Spring45Spring200 In heat and bred during breeding season (%) season (%)97.598.988.6 First service conception (%) 66.069.165.7 Services per conception 1.571.481.54 Pregnancy rate of those bred (%) 80.584.079.6 Pregnancy rate of total (%) 78.583.270.2 Avg. da. of breeding season conception occurred conception occurred161517

14. Death Loss of Calves through 365 Days of Age Calving Time Weaning Age Fall45Spring 45 and 200 Age at Time of Death (Days) Dead at birth 4.46.9 0 – 45 1.88.0 46 – 90 2.0.4 91 – 200 5.31.1 201 – 365.5.2 Total14.016.6

15. Effect of Season and Weaning on Calf Performance Calving Time Weaning Age Fall45Spring 45 and 200 Wt., 45 da. 155153151 Wt., 90 da. 222210238 Wt., 200 da. 468447468 Wt./ da. of age 2.342.242.34