400
We based our modelling on an average cattle herd, which included a total of 48.5
animals out of which 18 were cows. Although pastoralists practice random mating,
we assumed a peak calving season at the beginning of the dry season on December
1. We estimated the birth weight of calves to 20 kg and daily weight gains of 500 g
during the suckling period, enabling calves to reach 50 BW kg when weaned at 5
months at the end of the rainy season. Figures for weight gains according to feeding
intensity (Table 2) were obtained from feeding experiments undertaken both at the
HLH Farm (Selemani et al. 2015) and elsewhere, in Tanzania and Kenya. The
weight gains were assumed to be similar for steers, bulls and heifers. Steers and
bulls kept for meat were presumed slaughtered at 480 kg live body weight (LBW),
and dressing percentage was 50. The bottom line in Table 1 shows the age at slaughter of the three systems.
We used information from pastoralists, extension worker and researchers to estimate age at first calving, mortality, calving intervals and herd replacement rates.
Time for first calving can be lowered from three to two years for heifers, with regular concentrate supplementation as in the LSS and MSS alternatives. Although some
heifers calve at 2 years, average calving age in the TS is 3 years. For cows in all
treatments, we modelled biannual calving due to low feed intake. Across treatments,
the replacement rate for cows and animal mortality was 14 and 15%, respectively.
In Table 3, based on the information from the pastoralists, we present some
essential price estimates used for the modelling. The cost of concentrates was calculated from a standard feed mixture, corresponding with the composition of the
feed used in the feeding experiments and consisting in 70% maize bran, 27% sunflower seed cake, 2% mineral mix and 1% salt.
Traditionally, livestock graze rangelands and also consume after-harvest crop
residues on agropastoralists’ fields. These crop residues have limited market value
due to their low energy contents and high transaction costs in bringing them to feeding places. The crop residues may have an alternative economic benefit to be
included when modelling. Since manure is naturally left behind when cattle graze
on residues or for feedlots, manure could be relocated to the field; we have not differed between systems.
Table 2 Parameters for weight gains and supplementation levels for females, steers and bulls
System
TS
a
LSS
b
MSS
b
Supplementary feeding, concentrates, kg/animal/day:
Dry season
0
0.3
0.4
Rainy season
0
0.2
0.3
Body weight gain (BWG), g/animal/day:
Dry season
0.12
0.22
0.28
Rainy season
0.34
0.38
0.52
Average
0.22
0.29
0.39
Age at slaughter, years:
6.0
4.5
3.5
a
Traditional system: basal diet, mainly grazing for all animals, occasional supplementation with
crop by-products
b
Low and medium supplementation systems: basal diets + different levels of concentrate supplementation
A. S. Ringheim et al.
We based our modelling on an average cattle herd, which included a total of 48.5
animals out of which 18 were cows. Although pastoralists practice random mating,
we assumed a peak calving season at the beginning of the dry season on December
1. We estimated the birth weight of calves to 20 kg and daily weight gains of 500 g
during the suckling period, enabling calves to reach 50 BW kg when weaned at 5
months at the end of the rainy season. Figures for weight gains according to feeding
intensity (Table 2) were obtained from feeding experiments undertaken both at the
HLH Farm (Selemani et al. 2015) and elsewhere, in Tanzania and Kenya. The
weight gains were assumed to be similar for steers, bulls and heifers. Steers and
bulls kept for meat were presumed slaughtered at 480 kg live body weight (LBW),
and dressing percentage was 50. The bottom line in Table 1 shows the age at slaughter of the three systems.
We used information from pastoralists, extension worker and researchers to estimate age at first calving, mortality, calving intervals and herd replacement rates.
Time for first calving can be lowered from three to two years for heifers, with regular concentrate supplementation as in the LSS and MSS alternatives. Although some
heifers calve at 2 years, average calving age in the TS is 3 years. For cows in all
treatments, we modelled biannual calving due to low feed intake. Across treatments,
the replacement rate for cows and animal mortality was 14 and 15%, respectively.
In Table 3, based on the information from the pastoralists, we present some
essential price estimates used for the modelling. The cost of concentrates was calculated from a standard feed mixture, corresponding with the composition of the
feed used in the feeding experiments and consisting in 70% maize bran, 27% sunflower seed cake, 2% mineral mix and 1% salt.
Traditionally, livestock graze rangelands and also consume after-harvest crop
residues on agropastoralists’ fields. These crop residues have limited market value
due to their low energy contents and high transaction costs in bringing them to feeding places. The crop residues may have an alternative economic benefit to be
included when modelling. Since manure is naturally left behind when cattle graze
on residues or for feedlots, manure could be relocated to the field; we have not differed between systems.
Table 2 Parameters for weight gains and supplementation levels for females, steers and bulls
System
TS
a
LSS
b
MSS
b
Supplementary feeding, concentrates, kg/animal/day:
Dry season
0
0.3
0.4
Rainy season
0
0.2
0.3
Body weight gain (BWG), g/animal/day:
Dry season
0.12
0.22
0.28
Rainy season
0.34
0.38
0.52
Average
0.22
0.29
0.39
Age at slaughter, years:
6.0
4.5
3.5
a
Traditional system: basal diet, mainly grazing for all animals, occasional supplementation with
crop by-products
b
Low and medium supplementation systems: basal diets + different levels of concentrate supplementation
A. S. Ringheim et al.