## Energy requirements and energy in feeds

**Energy Requirements:**

The equations for basal metabolic rates (BMR) in carnivores are higher than for herbivores or omnivores with predicted daily energy requirements of 50-70 kcal/kg /day for lions (McNab 2000; Munoz-Garcia and Williams, 2005). A maintenance requirement of 115-130 kcal/kg for lions in zoos is proposed which is approximately 3.5kg per day for adult male lions and 2.7kg per day for adult female lions based on diets containing 1.75 kcal/g (AZA, 2012). A factorial approach might allow for the most appropriate extrapolation of energy requirements for lactating exotic felids (Kienzle, 1998):

MElact kcal/d = MEmat + [%N*(MEo + MEog)]/Efficiencymilk

Where Efficiencymilk is the conversion factor for maternal ME intake to milk ME output, which has been assumed to be 70% in cats (Kienzle, 1998). %N is the proportion of the offspring’s energy derived from nursing, MEo is the maintenance energy requirement for the offspring and MEog is the energy for offspring growth. AZA (2012) used milk output and intake studies (Hendricks & Wamberg, 2000b; Kienzle, 1998) and energy estimated for lion maintenance and growth the reformulated the above equation to become:

MElact kcal/d = 125*BWm0.75 + [%N*(125*Σ(BWo0.75) + 1.8(ADGo))]/0.7

Where ME = metabolic efficiency, BWm = maternal bodyweight, measured in kg; BWo = weight of each offspring, measured in kg; and ADGo = combined growth of offspring, average daily gain measured in g.

The above equations are suggested by AZA (2012) as a means for zoo staff to calculate the energy requirements of a lactating female lioness, and will be employed in this proposed feeding strategy. It is generally adequate to assume growth to be linear in young animals, as has been observed in the wild by Schaller (1972) and Smuts et al. (1980). Lion cubs should be monitored with regular weight checks and visual assessments to determine appropriate feeding rates.

**Energy in feeds:**

Regular assessment of feed is important as composition varies between products, manufacturers and even lots (Allen et al, 1995). AZA (2012) suggest the following equation by Clauss et al. (2010) to be appropriate for estimating metabolizable energy (ME) in carnivores:

ME kcal/kg = 39.9*(%CP+%NFE) + 90.0*(%Fat)

Where %CP = percentage of crude protein and %NFE = percentage nitrogen free extract (which can be estimated as 100-CP-Fat-Fiber-Ash).

**Equations useful for calculating energy needs and consequently, appropriate amounts of a diet:**

**Basal Metabolic Rate (BMR) =**70 X body weight in kilograms.75 (Kleiber) or 91.8 X body weight in kilograms.813 (McNab)

Estimated energy for maintenance may be 2 times BMR.

Energy Content or Metabolizable Energy (ME)

**ME (kcal/kg)**= 10((3.5 X crude protein) + (8.5 X crude fat) + (3.5 X carbohydrate or nitrogen free extract/NFE))

**NFE =**100 – (crude protein % + crude fat% + crude fiber% + moisture% + ash%)

**Worked Example:**Adult lion weight = 202kilograms

Nutrient analysis of meat mix:

37.2 % protein

39.6 % fat

9.1 % ash

1.1% fiber

41.6 % moisture

**1. Calculate estimated BMR energy needs:**

**Kleiber equation = 70 X body weight in kilograms.75**

70 X 202.75 = 3751 kcal

**McNab Equation = 91.8 X body weight in kilograms.813**

91.8 X 202.813 = 6872 kcal

__Range 3751- 6872 kcal/day__

**2. Calculate estimated maintenance energy needs:**

**Equation: BMR X 2**

(3751- 6872) X 2

__Range 7502 – 13744 kcal/day__

**3. Calculate metabolizable energy content of the diet:**

**Equation: NFE = 100 – (crude protein % + crude fat% + crude fiber% + moisture% + ash%)**

NFE = 100 – (37.2+39.6+ 6.1 + 1.1 + 41.6 + 9.1)

__NFE = 34.7__

**Equation: ME (kcal/kg) = 10((3.5 X crude protein) + (8.5 X crude fat) + (3.5 X carbohydrate or NFE)**

ME (kcal/kg) = 10((3.5 X 37.2) + (8.5 X 39.6) + (3.5 X 34.7))

__ME = 5883 kcal/kg__

4. Calculate kilograms of diet needed to meet estimated maintenance range:

4. Calculate kilograms of diet needed to meet estimated maintenance range:

7502 kcal/day ÷ 5883 kcal/kg = 1.3 kilograms

13744 kcal/day ÷ 5883 kcal/kg = 2.3 kilograms

__Range 1.3 – 2.3 kilograms of diet__