172 
Table 15 
Dry matter intake and energy available for fattening of caribou predicted from estimates of available 
live biomass and relationships between daily intake versus biomass (Fig. 11). 
Lactating females 
Cohort (83 kg BW) 
Period 1 2 3 4 
Available live biomass (g m) 35 43 52 50 
Drv matter intake (85% of peak, Fig. 11) 
(kg d7!) 2.90 3.35 3.10 3.55 
tg d-! (kg9:75)-1] 105 122 131 129 
Gross energy intake, GE| 
[kcal d”'(kg 0.75)" 514 598 642 633 
Metabolizable energy intake, MEI 
(Mcal d!) ; 6.35 7.37 7.95 7.86 
[kcald (kg 0.75) ] 231 268 289 286 
Energy requirements, ER 
[kcal d™! (kg 0.75) '] 
maintenance 190 190 190 190 
milk production 86 78 de 59 
total 276 268 263 249 
MEI/ER 0.84 1.00 1.10 1.15 
Energy available for fattening 
(keal a7!) 715 1017 
fikealidle” (kg O75) 1] 26 37 
Body weight gain 
(gd!) Tie 
(kg 50d) ere 
Nonlactating female Males 
(83 kg BW) (115 kg BW) 
5 1 2 3 4 5 1 2 3 4 5 
25 35 43 52 50: 30 85. 438 52 50.2 285 
2.90 2.54 2.88 2.08 3.02 2.54 3.09 348 3.65 3.62 3.09 
106) 92) 405 9112-110 92 88 99° 04 108s ae 
514 451 516 550 541 451 429 483 508 504 429 
6.35 5.55 641 682 6.71 555 6.78 766 8.04 7.97 6.78 
231 202° 233 248. 244. 202 193 218 229 227, 198 
190 190 190 190 190 190 190 190 190 190 190 
54 
244 
0.95 1.06 1.23 1.30 1.28 1.06 1.02 1.15 1.21 1.20 1.02 
330 1182 1595 1485 330 105 983 1370 1299 105 
12 43 58 54 12 3 28 39 of 3 
SO..128 lis 161 36 4 106 148 141 #11 
— 5.34 — — 4.17 — 
Periods 1-5 were respectively 21-30 June 1, 1-10, 11-20, 21-31 July, 1-10 August. 
Metabolizable energy intake = dry matter intake x gross energy of food (4.9 kcal g!) x energy digestibility 
(0.55) x metabolizability of digested energy (0.82). 
Energy requirement for maintenance = 
2 x fasting metabolic rate [97 kcal a! (kg 0.75)"1]; energy 
requirements of lactation = energy output in milk/efficiency of milk synthesis (0.74). 
Body weight gain = energy available for fattening x efficiency of fattening (0.39)/energy content of new 
tissue [3.6 kcal g (FW) ]. 
The calculations indicated that the duration 
of eating in lactating females (Fig. 10b) leads to 
intakes of 2.9 - 3.6 kg d!' (105-131 [gd°! 
(kg°:7°)-'], which were as high or higher than 
intakes estimated for bulls (3.1 - 3.6 kg d''). 
When expressed per unit metabolic body size 
[gd°'(kg°:7°)-'] food intakes for non-lactating 
females were similar to the bulls but consider- 
ably lower than estimates for the lactating fe- 
males. 
(c) Prediction of forage removed by the 
Prudhoe Bay caribou population. To estimate 
the amount of forage removed by the caribou 
population at Prudhoe Bay, the estimates of 
individual food intakes in Table 15 must be 
multiplied by the number of animals in the 
cohort. Also, an estimate must be made of the 
amount of forage eaten by the yearlings and 
calves in the population. In the absence of 
empirical data on the grazing intake of calves 
and yearlings, the following assumptions were 
made: 
(1) Food intake of calves was assumed to 
increase with age from 38 [g d'! (kg®:75)"'] at 
3 wk to 88 [g d'! (kg?:7°)'] at 6 wk. These 
intakes were 30-70% of adult values. Body 
weight gain was set at approximately 400 g dit 
(calculated from data for reindeer calves). 
(2) Intake of yearlings was assumed to be 
114 [g d! (kg®:75)°'], and body weight gain 
was set at 250gd"'. 
Calculations were made on the likely food 
intake for each cohort for each period based on 
the mean population size for that period (Fig. 2) 
and the mean herd proportions for 1972 and 
