USE OF BODY ENERGY RESERVES IN BEEF COWCALF NUTRITION

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USE OF BODY ENERGY RESERVES IN BEEF COW-CALF
NUTRITION

• Goals in feeding beef cows
• Optimize production efficiency
• Produce a calf that fits into an acceptable
  weight and quality
• Produce a calf every 365 days
• Post-partum interval must be no longer than 83
  days
• Beef cows must produce 3 dominant follicles
  before observed ovulation
• Therefore, first dominant follicle must be
  produced by 41 days post-partum
• Since first ovulation occurs 7 to 14 days after a
  cow comes out of negative energy balance,
  positive energy balance must be achieved by 31
  days post-partum
• Minimize feed costs
• Since 33 to 40 of the costs associated with beef
  cow-calf production are required for stored
  feeds, grazing needs to be optimized in relation
  to production/acre and length of season
• Maximize biological efficiency

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RELATIONSHIP OF BIOLOGICAL EFFICIENCY AND FEED
AVAILABILITY

• Maximum DMI at
  Max DMI, kg/yr
• ___Breed__ efficiency efficiency
  3500 7500
• gm calf
  kg/yr gm calf
• weaned/kg DMI/
  weaned/kg DMI/
• cow exposed
  cow exposed
• Red Poll 47.1
  3790 47 24
• Angus 41.3
  4111 39 17
• Hereford 35.1
  4281 30 13
• Pinzgauer 46.9
  5473 38 44
• Gelvieh 44.5
  5475 29 36
• Braunvieh 39.4
  7031 33 42
• Limousin 39.4
  7498 33 42
• Simmental 41.5
  8609 26 42
• Effects of feed availability on biological
  efficiency
• Rebreeding rates
• Weaning weights
• Implications
• Biological type should match feed resources
• Feed to optimize reproduction

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FEEDING TO MAINTAIN REPRODUCTION

• Maintaining reproductive performance requires
  given levels of body fat
• No less than 15.8 carcass lipid or 13.5 empty
  body fat at parturition
• Can be as low as 12.4 empty body fat at
  parturition if fed at 130 of NRC energy
  requirement for 60 days post-partum
• Empty body fat at breeding should be 15 for
  optimal pregnancy rates
• Cows should not exceed 20 carcass lipid or 17.8
  empty body fat
• Body weight
• Although NRC publications prior to 1996 used body
  weight, most producers dont weigh cows
• Body weights of pregnant cows can be confounded
  with conceptus

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USE OF CONDITION SCORING FOR BEEF COWS

• Systems
• 9-point visual system (NRC/Oklahoma)
• 9-point palpation system (Tennessee)
• 5-point visual system (Purdue)
• Limitations
• All systems are subjective
• Different systems make it difficult to
  standardize relative to nutrient requirements
• Advantages
• Dont require weighing of cows
• Less confounded by pregnancy than body weights
• Related to body weight
• Relationship with BW change
• Purdue 1 BCS unit change 68 kg (5-point
  system)
• NRC 1 BCS unit change 50 kg (9-point
  system)
• Relationship varies with age
• Mature cows 1 BCS unit change 34 kg (9-point
  system)
• Primiparous heifers 1 BCS unit change 68 kg (9
  point system)

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• Relationship of body condition score to body
  composition
• Component BCS
  Change/BCS (5-point) BCS BW
• r
  
  r
• Carcass lipid .63
  
  .70
• Carcass protein .36
  
  .59
• Empty body lipid .48
  5.5-66 units .74
• Empty body protein .26
  .2-1 units .47
• Hot carcass weight
  
  .95
• Backfat
  .075-.29 cm
  .62
• Relationship of BCS from different systems to
  body lipid
• BCS
  System
• 9-pt 5-pt NRC, 9-pt.
  Texas, 9-pt. Purdue, 5-pt
• 
  Empty body lipid,
• 1 1
  3.77 0
  3.1
• 2
  7.54 4
• 3 2
  11.30 8
  8.7
• 4 15.07
  12
• 5 3
  18.89 16
  14.9
• 6
  22.61 20
  

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• Relationship of body condition score to
  reproduction
• Body condition score at calving is the primary
  factor related to reestablishment of cyclic
  activity in beef cows
• Cows that calve at BCS gt 5 (9-point system) will
  exhibit estrus regardless of post-partum
  nutrition regime
• Feeding extra energy post-partum to cows that
  calve at BCS lt 4 will increase the percentage of
  cows exhibiting estrus in a finite breeding
  season
• Richards (1986)
• Days to first estrus
  Days to conception 1st service conception
• Post-partum
  Calving BCS
• nutrition lt 4 gt 5
  lt 4 gt5 lt 4
  gt 5
• High (.45kg/d) 60 51
  91 84 67
  59
• Mod. ( 0 kg/d) 60 46
  91 85 65
  67
• Low (-.68 kg/d) 56 50
  88 82 54
  70
• L/H (5 kg corn/d 67 49 91
  87 75
  70
• 14-d before
• and through
• breeding)

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• Houghton (1990)
• (Pre- last 90
  days) and Post- through breeding
• 
  energy intake
• LL
  LH ML MH
• Parturition
• BCS (5-point) 2.5 2.7
  3.3 3.2
• Empty body lipid 11.9 13.0
  16.8 16.7
• Post-partum
• BCS 2.5
  2.8 3.1 3.4
• Empty body lipid 11.4 13.7
  16.8 16.7
• Post-partum interval, d 72.6 54.3
  65.7 68.4
• Cycling, (60 days) 33.3 56.3
  52.9 54.3
• L 70 NRC
• M Maintenance
• H 130 NRC
• All cows started at condition score 3 on 5-point
  scale at 190 days of gestation

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• While high body condition scores at parturition
  may decrease post-partum interval, high condition
  scores at breeding will reduce conception rates
• Post-partum BCS PPI, d Breeding BCS 1st
  service conception,
• 2 88.5
  2 100
• 3- 69.7
  3- 94
• 3 59.4
  3 80
• 3 51.7
  3 70
• 4- 30.6
  4- 67
• Post-partum BCS change (5-point system)
  Pregnancy rate,
• lt 3 with decreasing BCS
  69
• lt 3 with increasing BCS
  100
• 3 with no change in BCS
  100
• gt 3 with decreasing BCS
  94
• gt 3 with increasing BCS
  75

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• Relying on post-partum energy supplementation may
  not be effective because some breeds respond with
  greater milk production
• Peak milk
  210-day total
• kg/kcal ME/BW.75
  kg/kcal ME/BW.75
• Intercept Slope
  Intercept Slope
• Angus 9.4 -
  929 3
• Braunvieh 6.7 .027
  501 7
• Charolais 6.4 .019
  568 4
• Gelvieh 5.8 .030
  477 6
• Hereford 8.5 -
  1,191 -
• Limousin 6.9 .014
  -1,387 26
• Simmental 10.9 -
  -1,495 30
• Although maximum rebreeding rate and gross return
  occurs at condition score 5, maximum weaning rate
  occurs at condition score 4.7 and maximum net
  return occurs at condition score 4.3.

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BODY CONDITION SCORE EFFECTS ON ENERGY RESERVES

• Energy in body condition
• Body condition score (5-point system)
  Mcal/kg BW change
• 1
  2.57
• 2
  3.82
• 3
  5.06
• 4
  6.32
• 5
  7.57
• The reason for this difference is that weight
  change at condition score 1 is 17 fat, but is
  77 fat at condition score 5
• Implications
• It takes more energy to increase condition score
  at a higher condition score than a lower
  condition score
• Loss of body condition at a high body condition
  provides more energy than loss of body condition
  at a low body condition score
  

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• Calculation of energy from body reserves
• Body composition from BCS
• Proportion of empty body fat AF .037683CS
• Proportion of empty body protein AP .200886 -
  .0066762CS
• Proportion of empty body water AW .766637 -
  .034506CS
• Proportion of empty body ash AA .078982 -
  .00438CS
• Empty body weight, kg EBW .851SBW
• Total ash, kg TA AA x EBW
• Calculation of total fat and protein reserves
• AA1 .074602
• AF1 .037683
• AP1 .194208
• EBW1, kg TA/ AA1
• Total fat, kg TF AF x EBW
• Total protein, kg TP AP x EBW
• Total fat1, kg TF1 EBW1 x AF1
• Total protein1, kg TP1 EBW1 x AP1
• Calculation of mobilizable energy
• Mobilizable fat FM TF - TF1

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Example 1

• If a beef cow with a shrunk BW of 485 kg at a BCS
  4 has a NEm requirement of 10.46 Mcal/day is
  consuming alfalfa hay with a NEm conc of 1.43
  Mcal/day at 10.9 kg/d, how long will it take for
  this cow to increase to a condition score of 5?
• NEm requirement, Mcal/day
  
  10.46
• NEm fed, Mcal/day
  1.43 x 10.9
  15.59
• NEm excess or deficient, Mcal/day
  fed-reqt
  5.13
• AF at CS4
  .037683 x 4
  0.1507
• AP at CS4
  .200886-.0066762 x 4
  0.1742
• AA at CS4
  .078982-.00438 x 4
  0.0615
• EBW at CS4
  .851x485
  412.74
• Total ash at any BCS
  EBW x AA
  25.3675
• AF at CS5
  .037683 x 5
  0.1884
• AP at CS5
  .200886-.0066762 x 5
  0.1675
• AA at CS5
  .078982-.00438 x 5
  0.0571
• EBW at CS5
  25.3675/.0571
  444.26
• Total fat at CS4, kg
  412.74 x .1507
  62.2000
• Total protein at CS4, kg
  412.74 x .1742
  71.8993
• Total fat at CS5, kg
  444.26 x .1884
  83.6986

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Example 2

• If a beef cow with a shrunk BW of 485 kg at a BCS
  4 has a NEm requirement of 10.46 Mcal/day is
  consuming mature bromegrass hay with a NEm conc
  of 0.94 Mcal/day at 9.7 kg/d, how long will it
  take for this cow to decrease to a condition
  score of 3?
• NEm requirement, Mcal/day
  
  10.46
• NEm fed, Mcal/day
  0.94 x 9.7
  9.12
• NEm excess or deficient, Mcal/day
  fed-reqt
  -1.34
• AF at CS4
  .037683 x 4
  0.1507
• AP at CS4
  .200886-.0066762 x 4
  0.1742
• AA at CS4
  .078982-.00438 x 4
  0.0615
• EBW at CS4
  .851x485
  412.74
• Total ash at any BCS
  EBW x AA
  25.3675
• AF at CS3
  .037683 x 3
  0.1130
• AP at CS3
  .200886-.0066762 x 3
  0.1809
• AA at CS3
  .078982-.00438 x 3
  0.0658
• EBW at CS3
  25.3675/.0658
  385.52
• Total fat at CS4, kg
  412.74 x .1507
  62.2000
• Total protein at CS4, kg
  412.74 x .1742
  71.8993
• Total fat at CS3, kg
  385.52 x .1130
  43.5638

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• Mcal NE required for
  each CS at CS 5 mature wt of
• Condition score 450
  550 650
• 2
  126 154 182
• 3
  141 173 204
• 4
  162 198 235
• 5
  186 227 269
• 6
  217 266 314
• 7
  267 314 371
• 8
  309 378 446
• 9
  377 461 545