1. Fitting cows to your environment Harvey Freetly U.S. Meat Animal Research Center, ARS, USDA

2. Efficiency = Outputs Inputs

3. Efficiency = Outputs Inputs Economic efficiency may not equate to biological efficiency

4. Factors effecting efficiency Feed efficiency Production life Biological Management Matching feed resources to requirements Labor

5. Adjust production cycle to match forage Management decisions can affect cow efficiency

6. Annual metabolizable energy requirement

7. Milk Fetus Activity Maintenance 64% 13% 8% 15% Annual metabolizable energy requirement

8. Given the majority of the annual feed is used for maintenance, what are the factors that contribute to the cost of maintenance?

9. A cow is at maintenance when she is neither gaining or losing energy (No change in body weight) Inputs (feed energy) = Outputs (heat energy)

10. Synthesis Degradation Tissues in the cow’s body are constantly be degraded and synthesized FoodHeat Synthesis and degradation are not 100% efficient

11. Factors affecting maintenance Cow size Milk production potential Genetics

12. The more tissue that is maintained, the more food energy is required to maintain the tissue Bigger cows take more feed to maintain their weight

13. Cow size increase maintenance requirement 6 lb hay

14. Selecting for bigger calf weaning weights typically increases cow size and the amount of feed required to maintain a cow

15. Bending the growth curve

16. Charolais – 1488 lb Simmental – 1301 lb Angus – 1179 lb Hereford – 1261 lb Jenkins and Ferrell, 1994 Big cows are not bad (Desirable cow size depends on available resources)

17. Ferrell and Jenkins, 1987 Increased milk potential is correlated with an increased maintenance in nonpregnant, nonlactating cows

18. A five pound increase in peak milk yield is correlated with a ~ 17% increase in maintenance

19. The increase in milk production is associated with an increase in liver weight

20. Metabolic energy required for maintenance of nonpregnant, nonlactating mature cows Breed Cross Daily Maintenance kcal/kg 0.75 Angus-Hereford130 Charolais – X129 Jersey – X145 Simmental - X160 Ferrell and Jenkins, 1984

21. Management decisions determine the amount of cow weight that is maintained at a given time of year

22. Maintaining lighter weight cows 1400 lb BCS 5 Cow

23. Freetly and Nienaber (1998) JAS 76:896-905 (112 d) (224 d) Nonpregnant-, nonlactating-cows

24. Energy retention in pregnant cow feed restricted during the second trimester and refeed restricted feed allocation in the third trimester Second Trimester Third Trimester Total Freetly et al. (2008) JAS 86:370

25. Jenkins et al., 1991 0.0193 Genetic variation in the ability of cows to adjust their metabolic rate to different levels of feed intake

26. Synthesis Degradation Synthesis Degradation Restricted feed Full feed

27. The second largest annual energy expenditure is for milk. Feed required by the cow increases with increased milk. Milk

28. Milk yield Persistency of lactation

29. Efficiency of milk production in first-calf beef cows Efficiency = 0.73 Freetly et al., 2006

30. Persistency of milk production can affect weaning weights Freetly and Cundiff, 1998

31. Persistency of milk production can affect weaning weights Freetly and Cundiff, 1998

32. There is considerable biological diversity among cows for maintenance and milk production

33. Development of marker-assisted technologies offer an opportunity to select cows for difficult to measure traits like maintenance

34. Fitting cows to your operation requires defining the your resources and market end points and then fitting the biological type to your environment

35. A good cow in one production environment may not be a good cow in another environment

36. Take advantage of the diversity that different types of cows offer in establishing a cow herd