B Mosimanyana and B Kiflewahid
Animal Production Research Unit, Department of Agricultural Research, Private Bag 0033, Gaborone, Botswana
Introduction
Ingredient analysis and nutritive value
On-farm feeding trial
Materials and methods
Results
Results
Conclusion
References
The need to increase milk production by the pert-urban small-scale farmers in Botswana is seen as a major objective by the Ministry of Agriculture during the current six-year National Development Plan; (NDP6-1985-91). Achievement of such objectives require investigating additional feed resources for livestock nutrition. Land suitable for arable farming is used mainly for cash and subsistence crops rather than for forage cropping.
To compensate for the increased need for milk on one hand and to examine the production potential of small farms, a research project was conducted and sponsored by the Animal Production Research Unit (APRU) of the Ministry of Agriculture, Botswana and the International Development Research Centre (IDRC) of Canada.
The objectives of this work were to:
1. Increase milk production by the animals owned by the small scale farmers.2. Investigate the feeding and nutritive value of forages and by-products introduced to milking cows on-farm and on-station.
3. Technical and economic evaluation of new interventions, such as the introduction of dual-purpose crossbreds and fodder crops.
The project area included four villages situated between 15 -20 km from Gaborone. The average rainfall was 316-414 mm in 1985.
At the end of the harvest season in June, 1985 all project farmers were encouraged to collect crop residues and legumes from their farms. Previous estimates of cereal crop residues for sorghum, millet and maize were 1.22, 1.15 and 1.16 ton of dry matter (DM) per hectare, respectively (Mosienyane 1983). In 1985 the average DM yield of lablab hay (Lablab purpureus) was 1.2 ton per hectare. Dry matter yield of cereal crop residues and lablab hay from farmer's fields ranged from 120 kg to 2,940 kg per farm (table 1). The wide variation in cereal stover yield was attributed to the low rainfall during 1985.
Table 1. Cereal stover yield and legume hay harvested by Project farmers in 1985.
|
Area |
Maize, Sorghum and Millet kg/farm |
Lablab kg/farm |
|
Oodi |
120 - 2,940 (3) |
360 (1) |
|
Bokaa |
120 - 560 (4) |
180-600 (2) |
|
Kopong |
160 - 360 (2) |
80 (1) |
|
Mmopane |
120 - 620 (2) |
120 (1) |
During the 1984/85 harvest period samples of cereal and legume crop residue and lablab hay were randomly collected from all farmers for laboratory analysis and nutritive value estimation (table 2).
Table 2. Composition of stovers and fodder legumes collected by Project Farmers (1984-85).
|
Feed |
Composition (%) of Dry Matter (1) |
|||||
|
Organic Matter |
Crude Protein |
Crude Fibre |
Ash |
Ca |
P |
|
|
Maize stover |
90.97 |
7.84 |
28.29 |
9.03 |
0.278 |
0.123 |
|
Sorghum stover |
91.58 |
5.56 |
32.82 |
8.42 |
0.379 |
0.103 |
|
Millet stover |
88.66 |
5.23 |
39.42 |
11.34 |
0.309 |
0.043 |
|
Lablab |
88.59 |
16.14 |
22.68 |
11.41 |
1.688 |
0.131 |
|
Velvet bean |
91.70 |
16.27 |
25.14 |
8.30 |
2.540 |
0.135 |
|
Cowpea stover |
94.19 |
13.63 |
26.3 |
5.81 |
1.425 |
0.132 |
|
Sorghum bran (2) |
97.32 |
11.48 |
3.15 |
2.68 |
0.381 |
0.310 |
(1) Means represent data from four replicate samples per farmer's field
(2) Sorghum bran (moroko) from Gababe Village Sorghum Millers
The in vitro digestion coefficients of the crop residues and fodder legumes harvested by farmers are given in table 3. Digestibility of dry matter (DMD) and organic matter (OMD) were lower for the cereal stovers (maize, sorghum and millet) than those of the fodder legume and cowpea stover. Digestibility of maize stover exceeded those of sorghum and millet stovers. The results show that higher digestibility coefficients were related to higher crude protein and lower crude fibre contents (tables 2 and 3).
It is clear that cereal crop residues need to be fed in association with supplements of higher crude protein and energy contents to meet the animals requirements for growth and milk production.
Table 3. In Vitro Dry and Organic Matter Digestibilities* of Stovers and Fodder Legumes collected by Dairy Project Farmers
|
Feed |
Dry Matter Digestibility (%) |
Organic Matter Digestibility (%) |
|
Maize stover |
59.1 |
53.2 |
|
Sorghum stover |
48.6 |
40.0 |
|
Millet stover |
40.1 |
28.9 |
|
Lablab |
60.5 |
53.8 |
|
Velvet bean |
55.2 |
49.0 |
|
Cowpea stover |
66.4 |
58.8 |
|
Sorghum bran |
56.9 |
48.3 |
* Each value is a mean of four replicate samples per farmer's field.
The rationale for introducing the legume fodders in the farming system was, therefore, to formulate diets that could satisfy nutritional requirements for pregnant and/or lactating dairy cows. As shown in table 3 the crude protein content of lablab (16.4%) and velvet bean (16.27%) were as high as that reported for lucerne hay (16.0% NRC 1970).
In the rural production situation the opportunity to improve the quality of cereal stover based diets is either by providing a high quality legume fodder or by feeding moroko (a by-product of the local milling process of sorghum) or by a combination of both.
As part of the programme to evaluate alternative management interventions three winter feeding systems were carried out for the on-farm trials involving twelve farmers in the project. The objectives of the comparative feeding trial were to determine voluntary feed intake and performance of lactating cows fed sorghum stover supplemented with either lablab or moroko. Bonemeal salt (1:1) or Dicalcium phosphate/salt (1:2) were available to animals at free choice.
On-farm trials
Twelve farmers were divided into three groups to carry out a winter feeding trial on crossbred Simmental and Tswana cows in groups each of four head. The crossbred Simmental were provided by Government on an exchange basis with the Tswana cows from farmers. The treatments (feed systems) used by these three groups of farmers to feed their lactating cows were:
- 85% sorghum stover and 15% lablab (TRT A)
- 75% sorghum stover and 25% moroko (TRT B)
- 100% sorghum stover (TRT C)
All treatments had ad libitum phosphate lick.
The average chemical composition of the sorghum stover based diets as fed during the trial are shown in table 4. Crude protein in sorghum stover (5.5%) was lower than the 7.0% maintenance requirements. Supplementation with either lablab (15%) or moroko (25%) increased the crude protein in the diet to 7.40% and 7.01% respectively. Table 4 also shows that the crude protein contribution to the diet by lablab and moroko were 37.7% and 39.4% respectively, implying therefore that 15% lablab and 25% moroko are equivalent in their contributions as supplements.
Table 4. Components and chemical analysis of diets used in the on-farm trial.
|
Chemical analysis: (DM basis) |
85% sorghum stover + 15% Lablab |
75% sorghum stover + 25% Moroko |
100% sorghum stover |
|
Organic matter |
91.10 |
93.00 |
91.60 |
|
Crude protein |
7.40 |
7.01 |
5.56 |
|
Crude fibre |
31.06 |
25.54 |
32.82 |
|
Ash |
8.90 |
7.02 |
8.42 |
|
Estimated TDN |
55.56 |
63.73 |
53.90 |
|
% contribution of crude protein content in the diet | |||
|
Sorghum stover |
62.3 |
60.6 |
100 |
|
Lablab |
37.7 |
- |
- |
|
Moroko |
- |
39.4 |
- |
Mean daily dry matter (DM) intake (kg) and DM intake (kg) per 100 kg of body weight during the trial period for the three treatments are giver in table 5. The higher intake of the moroko diet was attributed to the concentrated form of the bran which was fed first, before the sorghum stover. The DM intakes of the first and the third diets were close to the amount required to cover the requirement of suckling cows of 350 kg liveweight (NRC 1970).
Roughage consumption of 2 kg per 100 kg liveweight is considered satisfactory during the late stage of the lactation period (Crampton and Harris 1969). The average daily milk yield (kg) per herd and per cow during the milking period for the different treatments is given in table 6. Recorded daily milk yield does not include milk left for the calf. To initiate milk let down, calves were allowed 30 seconds to suckle before milking and put back to dams 1 hr after milking. The results showed that both Simmental crossbreds and Tswana cows on TRT B produced higher daily milk yields than cows on TRT A.
Table 5. Voluntary feed intake by lactating cows during the trial period.
|
|
Diets |
||
|
TRT A |
TRT B |
TRT C |
|
|
Average Liveweight (kg) |
356.3 (1) |
356.5 (2) |
322.6 (3) |
|
DM Intake (kg/day) |
8.27 |
10.21 |
8.96 |
|
DM Intake/100 kg LW (kg/day) |
2.27 |
2.85 |
2.79 |
|
Crude Protein intake/100 kg LW (kg/day) |
0.17 |
0.20 |
0.15 |
(1) Data from 16 cows of 4 farmers.
(2) Data from 13 cows of 4 farmers.
(3) Data from 9 cows of 3 farmers.
Table 6. Average milk yield (kg) of Simmental Crossbred (SX) and Tswana (TS) cows fed sorghum stover based diets.
|
|
Diets |
||||
|
TRT A |
TRT B |
TRT C |
|||
|
Type of animals |
SX |
TS |
SX |
TS |
TS |
|
No. of cows |
5 |
13 |
5 |
13 |
14 |
|
Period (days) of milk yield recording |
118 |
92 |
123 |
91 |
41 |
|
Average milk yield: kg/herd/day |
13.5 |
22.1 |
20.5 |
27.3 |
21.0 |
|
Average milk yield kg/cow/day |
2.7 |
1.7 |
4.1 |
2.1 |
1.5 |
All cows lost weight from September to January primarily due to parturition as well as the drought conditions (table 7). By January 1986 SX and TS cows on TRT A and TRT B had lost 17.8, 15.6, 24 and 21% of their initial liveweight respectively. However, by March, 1986 the liveweight losses decreased to 6.6, 7.2, 10.7 and 10.1% of their initial liveweight respectively.
Table 7. Liveweight changes of Simmental Crossbred (SX) and Tswana (TS) cows on TRT A and TRT B diets.
|
Diet |
Liveweight kg |
|||
|
Breed |
Sept. |
Jan. |
Mar. |
|
|
TRT A
|
SX (n = 6) |
422 |
347 |
394 |
|
TS (n = 9) |
383 |
291 |
342 |
|
|
Average |
402 |
319 |
368 |
|
|
TRT B
|
SX (n = 6) |
417 |
352 |
387 |
|
TS (n = 14) |
357 |
282 |
321 |
|
|
Average |
387 |
328 |
354 |
|
On-station feeding trial
A comparative on-station partial milking system had been going on at the Research Station since 1981 using both Tswana and crossbred Simmental cows. Results from investigations on the partial milking system conducted by APRU indicated the improved potential for milk production by the Simmental crossbred cows as compared to the Tswana cows (APRU 1983/84). Response to supplementation (Dairy meal) was evident during the period after deterioration of range grazing quality in March. Both types of cows produced higher milk yields in this period when their feed was supplemented. The results showed no advantage in supplementation of the feed during the normal grazing season (APRU 1984). There was no improvement in the performance of either cow or calf to supplementation and therefore, unless feed costs are very low, supplementation must be regarded as of marginal benefit during active pasture fodder growth.
Lactating cows trial
The trial was redesigned using Tswana, half-bred Simmental and three-quarter-bred Simmental cows to evaluate milk production and response of both cow and calf performance to alternative feed supplements. Within a breed type, cows were randomly allocated to treatments in calving sequence. Tswana cows (TS) received so supplement, half-bred Simmental were divided into two groups, with or without moroko supplement, while the three-quarter-bred Simmental (SSX) received either moroko or dairy concentrate. Calves from either treatment were divided into two groups, with and without moroko. The herd was milked twice daily with recorded milk being total milk less that suckled by calf.
Table 8 provides the lactation data according to breed and supplementation treatment. The drought conditions which prevailed in 1984/85 meant that throughout the grazing season (20 weeks of lactation) the cows had to be fed additional fodder in the form of either crop residues or medium quality hay. Due to poor quality of the fodder, milk yields became low and continued declining progressively.
Table 8. Milk yields and lactation length of Tswana/Tuli (TS) half-bred Simmental (SX) and three-quarter Simmental cows (SSX) on diets supplemented with moroko or balanced concentrate.
|
Breed Type (no.) |
TS (18)* |
SX (20)* |
SSX (23)* | ||
|
Supplement |
Nil |
Nil |
Moroko |
Moroko |
Conc. |
|
Lactation yield (kg) |
274.7 |
525.4 |
583.5 |
691.4 |
725.6 |
|
Yield range (kg) |
98-475 |
410-741 |
255-928 |
452-970 |
605-1250 |
|
Lactation length (days) |
208 |
245 |
269 |
278 |
291 |
|
Range (days) |
108-298 |
209-295 |
216-309 |
190-332 |
271-329 |
|
Mean daily yield (kg/head) |
1.32 |
2.14 |
2.17 |
2.49 |
2.49 |
* Number of cows per breed.
The effects of supplementation are summarised in Table 8. In the SX group there was only a small response to feeding moroko, mainly towards the end of lactation when the roughage diet was mainly maize/sorghum stover. The lactation yields were not significantly different (P>0.10) between animals fed moroko or no-moroko (Table 8). Mean lactation lengths between the two feed treatments were significant (P<0.10). There were 269 days for animals consuming moroko versus 245 days for those who were not supplemented.
There were no differences (P>0.10) in total lactation yield and lactation length in the SSX fed moroko versus those fed the dairy concentrate (Table 8). Comparisons between the breeds revealed higher lactation yield for SX and SSX compared to TS because of greater lactation persistence of the former. Milk yields in the SSX were 2.5 times those of the TS group.
The TS cows had a net post-calving gain of 1.6% while the unsupplemented and supplemented SX gained 5.1 and 6% respectively. There was no effect of the level of supplementation on the SSX who gained on average 6% of post-calving liveweight. The poor performance of the cows can be attributed to the drought conditions that prevailed during the trial.
Table 9 shows the performance of calves fed with or without moroko. The progeny of the TS cows were bred from pure Tswana or Tuli whilst those of SX and SSX were bred by a Simmental bull. The results are expressed in terms of liveweight gain to 210 and 305 days corrected for sex and date of birth. Liveweight gains were generally poor, reflecting both the rate of milk extraction (twice per day) and the poor fodder situation. Liveweights at 210 days from weaning were 40% below the expected weights of ranch calves of these breeds under good grazing conditions. However, by 305 days, when the calves were weaned, liveweights were 25% lower than those from APRU ranches.
Table 9. Mean liveweight gains (kg) of calves reared by TS, SX and SXX breeds on-station.
|
|
Birth to 210 days |
Birth to 305 days |
|||||
|
Calf treatment |
Calf treatment |
||||||
|
Cow Breed |
Cow Treatment |
Nil Moroko |
Plus Moroko |
Mean |
Nil Moroko |
Plus Moroko |
Mean |
|
TS (17)* |
Nil Moroko |
83.6 |
93.7 |
88.7 |
105 |
113 |
109.0 |
|
SX (16)*
|
Nil Moroko |
81.0 |
86.0 |
83.5 |
97.9 |
119 |
108.5 |
|
Plus Moroko |
107.4 |
102.3 |
104.9 |
120.6 |
147 |
133.8 |
|
|
SSX (19)*
|
Plus Moroko |
77.4 |
83.4 |
80.4 |
97.3 |
117.8 |
107.6 |
|
Dairy concentrate |
86.3 |
100.0 |
93.2 |
109.0 |
133.3 |
123.7 |
|
|
Mean |
|
87.1 |
93.0 |
90.1 |
105.9 |
127.0 |
116.5 |
* Number of cows per breed.
The potential for self-sufficiency in feeding dual purpose cattle based on crop residues was confirmed for milk production.
Cereal crop residues are available to all farmers and since they are low in crude protein content, there is a need to supplement them with high protein legumes (cowpeas) and fodder crops (lablab) or locally produced milling by-products (moroko). The feeding systems based on natural grazing (summer) and feeding of conserved crop residues (winter) are the most practical.
Further research is needed to investigate economic methods of allocating land for both feed for human consumption and livestock. Conservation methods for crop residues and other legumes should continue to assess the full benefits to be derived from these fibrous materials.
APRU 1983. Livestock and range Research in Botswana. Annual Report.
APRU 1984. Livestock and range Research in Botswana. Annual Report.
APRU 1985. Livestock and range Research in Botswana. Annual Report.
Crampton D.W. and Harris L.E. 1969. Applied Animal Nutrition. 2nd Edition. W.H. Freeman and Co., San Francisco, USA.
Mosienyane B.P. 1983. Crop Residues for Animal Feeding. The Bulletin of Agricultural Research in Botswana 1:3.
NDP 1985. National Development Plan 1985-9. Ministry of Finance and Development Planning. Government Printer, Gaborone.
NRC 1970. Nutrient Requirements of Domestic Animals, No 3. National Research Council, Washington D.C.
