Stocker Programs, Feedlot Performance and Carcass Merit

1. Stocker Programs, Feedlot Performance and Carcass Merit Jim Oltjen University of California, Davis April 10, 2008

2. UC Sierra Foothills Research & Extension Center

3. UC Davis Feedlot

4. Outline • Compensatory growth • Using Davis Growth Model for performance and carcass traits • Growing phase feed quality effects • Growing phase length effects • Previous nutrition effects on carcass merit and maintenance • Physiology of growth and fat development • Latest Research on: • Patterns of marbling • Length of stocker phase effects on fat distribution • Length of stocker phase effects on rate of marbling and subQ fat gain • Residual feed intake relationship with maintenance requirements • New model to predict fat distribution

6. Compensatory growth in beef cattle From: Sainz et al., 1995

7. Compensatory gain in feedlot steers Sainz et al., 1995

8. Compensatory gain in feedlot steers Sainz et al., 1995

9. Compensatory gain in feedlot steers Sainz et al., 1995

10. Davis Growth Model Net energy Ttrtrttr Rtrttr r Fat (kg) Maintenance Protein

11. Davis Growth Model (Oltjen et al. 1986) Biological processes: Cell proliferation and hypertrophy Homeorrhetic control Metabolizable Energy Intake Biological processes: Synthesis and degradation Heat production Biological processes: maintenance Efficiency of conversion into net energy is related to both quantity and concentration of metabolizable energy in the diet

12. Effect of diet quality in growing phase to a constant BW endpoint (327 kg)

13. Stocker cattle’s rate of gain is linear from 2 to 3 Mcal ME/kg DM assuming cattle are fed ad libitum or have adequate available forage.

14. (growing phase to 327 kg BW)

15. Finishing daily gain is inversely and nearly linearly related to previous growing phase performance.This hardly varied whether cattle were fed to equal body weight or fat content endpoints.

16. (growing phase to 327 kg BW)

17. Steers fed to an equal body weight endpoint were more sensitive to previous growing phase ration energy compared to steers fed to a constant fat endpoint. Those fed higher energy diets as calves reached acceptable carcass fatness at much lighter weights.

18. Effect of growing phase length(MEC = 1.87 Mcal/kg)

19. Finishing period performance (growing phase MEC 1.87 Mcal/kg)

20. Finishing period performance (growing phase MEC 1.87 Mcal/kg)

21. (growing phase MEC 1.87 Mcal/kg)

22. Steers fed to an equal body weight endpoint were more sensitive to the length of the growing period compared to a constant fat endpoint.

23. Calf fed’s reach carcass fatness before desirable slaughter weights, confirming previous work that medium or small frame steers require a growing period before slaughter, particularly if not implanted.

24. Calf fed’s reach carcass fatness before desirable slaughter weights, confirming previous work that medium or small frame steers require a growing period before slaughter, particularly if not implanted. Conversely, if we use longer growing periods due to increased cost of grain, cattle will have to be fed to larger weights for acceptable fatness, further exacerbating the progressive trend to larger carcasses in the industry.

25. Intermuscular Fat Subcutaneous Fat Intramuscular Fat

26. Compensatory growth in beef cattle a a a b b a a a b b a ab b c c From: Sainz et al., 1995

27. Compensatory growth in beef cattle a a ab ab b a ab b ab b a ab ab b b From: Sainz et al., 1995

29. Compensatory gain in feedlot steers Sainz et al., 1995

30. Compensatory gain in feedlot steers Sainz et al., 1995

31. Compensatory gain in feedlot steers SEM a b b Sainz et al., 1995

32. Growth curves

33. Allometric growth

34. Frame score and total body fat

35. Growth gradients among adipose depots

37. From: Bruns et al. (2004) J. Anim. Sci. 82:1315-1322

38. UC Sierra Foothills Research & Extension Center

40. From: Sainz & Vernazza-Paganini, 2004

41. From: Sainz & Vernazza-Paganini, 2004

42. From: Sainz & Vernazza-Paganini, 2004

43. UC Sierra Foothills Research & Extension Center

45. Gain in 12th rib fat gain (BF. µm/day) in high and low growth cattle backgrounded at two ME levels

46. Gain in intramuscular fat gain (IMF. %/day) in high and low growth cattle backgrounded at two ME levels

47. UC Davis Feedlot

49. Residual Feed Intake • More efficient steers with negative RFI ate less (12%). • RFI was related to maintenance energy requirements (r=0.42). • No ‘significant’ association with carcass traits. • Myofibrillar protein degradation rates were positively related to maintenance energy requirements (r=0.76), but were not related to RFI (r=-0.14). A genetic trait related to RFI should be used in prediction models to account for differences in maintenance. Eventually adjust for protein synthesis/degration rate differences which are explicitly represented in the Davis Growth Model.

50. Intermuscular Fat Subcutaneous Fat Intramuscular Fat