cow_and_feedlot_managment - Beef Cattle Energetics Point of...

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1 Beef Cattle Energetics Point of Inflection= IM Point of Inflection= IM Point of Inflection= IM + }
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2 Point of Inflection= IM + } - } Energy Reserves In livestock production, 0 EB is rarely achieved Beef cows Periods of poor forage quality/availability Result in negative energy balance » OK to be negative as long as managed properly Periods of excellent forage quality/availability Results in positive energy balance » Important to be in positive energy balance heading into breeding season Energy Reserves • Important to have energy reserves – Optimal management of body reserves is critical for economic success of a beef cow operation Energy Reserves • Important to have energy reserves – Either extreme (excessive fat or thin) can cause • Metabolic problems • Decrease in milk production – Decrease in calf performance • Calving difficulties • To fat animals is a waste of resources • Decrease in reproductive efficiency Energy Reserves • Assumption is that excess energy is captured in the form of fat – True for animals in moderate to fat condition – In thinner animals, evaluating protein
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3 Chemical Composition Energy reserves Energy required for body reserves is related to the energy content of the tissues NRC (1996) estimates that 5.82 Mcal are required for 1 kg of gain Energy Reserves for BCS Example • 500 kg, gaining from BCS 4 to 5 – Diet = + 3 Mcal/d 207 Mcal (NRC Table) / 3 Mcal/d = 69 d for animals to gain 1 BCS (~35 kg) Example • 500 kg, losing condition from BCS 5 to 4 – Diet is – 3 Mcal/d – 1 Mcal of tissue = 0.8 Mcal of diet • Use of body reserves is 25% more efficient than diet 207 Mcal (NRC Table) x 0.8/ 3 Mcal/d = 55 d for animals to lose 1 BCS (~35 kg)
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4 Body Condition Scores • 1 - Emaciated • 2 - Very thin •3 -Th in • 4 - Moderately thin • 5 - Moderate (ideal) • 6 - Moderately fleshy • 7 - Fleshy • 8 - Very fleshy • 9 - Obese BCS 3 BCS 7 Body Condition Scores BCS 3 BCS 5 BCS 6 BCS 7
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5 BCS 9 BCS is a practical indicator of nutritional status and its effect on reproduction in the postpartum cow Short et al., 1990; Williams, 1990; Wagner et al., 1988; Randel, 1990 Prepartum Energy Balance Effects on BCS at Calving BCS = EB bcs (0.58 ± 0.09) + 5.62 ± 0.12 (R 2 = 0.65) Adapted from Hess et al., 2005 -3 -2 -1 0 1 2 34567 BCS @ calving EBbcs, Mcal/d Relationship Between BCS at Calving and BCS at Breeding BCS breeding = BCS calving (0.70±0.06) + 1.39±0.30 (R 2 = 0.47) 3 4 5 6 7
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This note was uploaded on 05/11/2011 for the course ANSC 324 taught by Professor Unknown during the Spring '11 term at Purdue University-West Lafayette.

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cow_and_feedlot_managment - Beef Cattle Energetics Point of...

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