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Evaluation of cassava energy source in dairy cow concentrate feeds in Kenya


Materials and methods
Results
Discussion
References


I. A. Sanda and J. N. Methu

Results are presented of two experiments carried out to investigate the optimal inclusion level of cassava root meal (CRM) in dairy concentrates using. respectively 12 and 10 lactating cows in 3x3 and 2x2 latin square designs. The treatments included isonitrogenous diets A, B. C containing 0, 200 or 450 g/kg CRM respectively in experiment I, and diets A and B with 0 or 570 g/kg CRM respectively in experiment II. Total substitution of maize meal with cassava had no significant effect on the in vivo digestibility of either the dry matter or organic matter. Complete substitution of maize meal with cassava meal was economical and was associated with a reduction in the feed cost of Ksh. 328 (US $ 10) per tonne. Thus, cassava meal is an acceptable ingredient in concentrate feeds and it can totally replace maize meal in the concentrate diets for cows producing approximately 12 kg of milk per day.

Cassava (Manihot esculenta Crantz) is widely grown in many tropical countries for its edible roots. In Kenya, the main producing areas are western and coastal regions, below 1500m (Acland 1973). The cassava plant is tolerant to drought, it can produce relatively high yields in soils of low fertility, and can withstand suboptimal agronomic conditions. These qualities make cassava an ideal crop for semiarid areas of Kenya which are being inhabited by people moving from high to low potential areas because of high human population pressures.

In 1988, the area estimated to be under cassava cultivation in Kenya was 53 500 ha and the projected production was 450 000 tonnes. This gives an average yield of 8 tonnes/ha. However, the yields can be as high as 25 tonnes/ ha (Acland 1973).

Most of the roots produced are consumed in the households, and the surplus is sold in local markets. At the Kenya coast, some of the fresh roots are sold to the cassava starch manufacturing factory. Domestic demand for cassava food fluctuates according to the supply of cassava substitutes (mainly maize) and market prices vary according to the supply. In the producing areas, particularly in western Kenya, cassava is sold in the market in the form of dry chips. The fresh roots are peeled, cut into chips and fermented before sun-drying or just sun-dried after being cut into chips. Fermentation and sun-dying reduce the content of the cyanogenic glucosides (Ravindra et al. 1983). Cassava, a high calorie and low protein (about 2-2.5%) source, needs to be combined with complementary protein sources such as oil seed cakes and/or nonprotein nitrogen compounds such as urea in animal feeds.

Information on the use of cassava as livestock feed is scanty. Abate (1981) noted a decrease in the growth rate of beef calves offered a concentrate diet containing cassava as the main source of energy. Also, dairy cows receiving cassava root meal (CRM) as the sole concentrate ration showed no significant reduction in milk yield (Anon. 1984). Work from other countries indicate that cassava root meal can replace cereals such as oats (Mathur et al. 1969) and barley (Brigstocke et al. 1981) in dairy cow concentrate diet as the main source of energy. In these trials there was comparable performance in milk yield, butterfat and liveweight gains. Brigstocke et al. (1981) also noted that diets containing cassava were cheaper. Animals on CRM-based diets have been shown to require higher mineral supplementation, particularly sulfur, than those fed on cereal-based diets (Lisovets and Lipyenchik 1982).

In Kenya, the energy component of the concentrate rations in livestock feed is mainly supplied by cereals and the by-products of cereal milling industries, with maize being the most widely used. Maize is also a staple food of most people apart from its being used in the formulation of monogastric diets, hence, there is need to exploit alternative sources of energy in animal feed formulation to release more maize for human consumption.

The purpose of the experiments described here was to evaluate the potential of CRM as energy source in the dairy concentrate feed in order to identify the optimal inclusion level.

Materials and methods

Diets: In experiment I, ground cassava chips and maize meal were used as main energy sources in formulating three isonitrogenous concentrate rations. The levels of both ingredients were varied to determine the effect of partial replacement of maize with CRM on milk yield. The dry cassava chips were mainly the peeled and fermented type, procured from local markets in western Kenya. The concentrate diet without cassava had maize inclusion level of 546 g/kg whereas those with cassava had reduced maize levels of 346 and 96 g/ kg respectively. These concentrate diets are denoted as rations A, B and C, as shown in table 1.

For experiment II the same feed ingredients as in experiment I were used, but molasses was included to formulate two isonitrogenous concentrate rations. Ration A had maize at a level of 570 g/kg while ration B had CRM replacing all the maize at the same level. Molasses was added at a level of 2% to reduce dustiness and to improve the palatability of the cassava diet which had urea. The detailed formulation of the diets is shown in table 1.

Animal and experimental design: In experiment I twelve cows, four each of Friesian, Ayrshire, and their F1 cross-in 2nd-4th week lactation and 4th-20th week lactation-were divided into four groups with one cow of each genotype in each group. The animals varied in live weight from 366 kg to 470 kg at the beginning of the experiment. They were allocated to the three treatments in a 3x3 latin square design which was replicated four times to consist of three periods each of 30 days, 7 days being allowed for adaptation to different diets and 23 days as the feeding period. Period 2 however had an adjustment period of 12 days because two animals had to be replaced in group III, one because of chronic eye problem and the other due to misrecording of her genotype. Similarly, one animal was replaced in group IV because of lameness.

Table 1. The physical composition of the concentrate diets based on maize and cassava root meal (g/kg, air dry basis)

Ingredient

Experiment I

Experiment II

A

B

C

A

B

Maize meal 546 346 96 570 0
Cassava root meal 0 200 450 0 570
Cotton seed cake 318 318 318 290 290
Wheat bran 136 136 136 110 110
Molasses 0 0 0 30 30
Urea (46% N) 0 4.8 10.8 0 19.6
Mineral premix a 30 35 35 30 35

Cost per kg b 3.79 3.71 3.53 3.81 3.48

Notes: a The mineral premix as Maclik from Wellcome Kenya Ltd.
b The costs per kg of diet are for 1988, in Ksh (Kenya shillings)

For experiment II, ten cows in 2nd-5th week lactation and 7th-28th week lactation were divided into five pairs according to their milk yield during the previous two weeks. They weighed an average of 460 kg at the commencement of the experiment. The experimental design was a 2x2 latin square with five replications. Two periods, each of 42 days, with 14 days for adjustment to the diets were used in the trial.

Feeding and management of the animals: In both experiments, the cows grazed pastures predominantly composed of Rhodes grass (Chloris gayana) from 0800 to 1530 h and were offered the concentrate feed at each milking around 0700 and 1600 h everyday. Concentrates were fed according to the mean weekly milk yield, at the rate of 400 g/kg of milk produced, and were offered in two equal portions, one for each milking.

Milk yield was recorded at each milking and butterfat content was determined. The cows were weighed once a week and accorded other normal management practices.

Intake and digestibility: In a supplementary trial, the digestibility of the concentrate rations in each experiment was determined in conventional metabolism stalls using steers. The basal diet of chopped grass hay (mainly Themeda spp.) was fed, allowing feed residue of 20 percent. In experiment I, three steers per ration with mean weights ranging from 462-510 kg were used during a collection period of 7 days, following an adjustment period of 16 days. The concentrates were fed at a rate of 6 kg/steer/day, a figure obtained from an average amount of concentrate consumed by the cows when on the feeding trial. In experiment II, four steers per ration, with mean weights ranging from 272-278 kg, were used over collection and adjustment periods similar to those in experiment I. The steers received concentrates at an average daily rate of 5 kg/steer.

Analytical methods: The analytical methods followed in both experiments were similar. Two samples of milk were taken once each period from morning and evening milk for butterfat determination once every 2 weeks. Fresh feed and fecal samples were pooled at the end of the digestibility experiments and subsamples taken for analysis according to AOAC (1975).

Since three cows were introduced into experiment I, their missing values (milk yield, butterfat and body weight from period 1) were estimated using the missing data technique in a latin square (Kwanchai and Arturo 1984).

Digestibility coefficients of hay alone and the total ration (concentrate + hay) were determined directly while those for the concentrate portion were calculated by differences as described by Giger and Sauvant (1983). The digestibility coefficients thus obtained were used as reference to performance study on lactating cows.

The data obtained on intake, digestibility and performance were subjected to variance and covariance analyses and differences between treatment means tested using Student's t-test (Snedecor and Cochran 1980).

Results

Table 2 shows the chemical composition of the concentrate diets based on maize and cassava which were similar in crude protein, crude fibre and ash.

Milk yield, milk fat and liveweight: For experiment I the mean milk yield and butterfat content are shown in table 3. There was no significant difference in milk yield between treatments. The milk yield was 11.7 kg/day for the ration without cassava, and 11.1 and 11.6 kg/day for the rations with 200 and 450 g cassava per kg, respectively.

The differences in the pretrial period and the differences between the concentrate feeds were not significant. There were no significant differences in milk fat concentrations for the rations A, B and C.

Differences in liveweights of the cows were not significant; mean figures were 415 kg, 416 kg and 417 kg for the cows offered rations A, B and C, respectively.

Table 2. The percentage chemical composition of the diets based on maize and cassava root meal

Component (%)

Experiment I

Experiment II

Hay

A

B

C

Hay

A

B

Dry matter 91.39 91.45 91.79 91.73 83.56 89.84 89.86
Crude protein 3.44 17.99 17.85 17.71 3.74 16.67 18.79
Crude fibre 39.77 7.03 7.25 7.35 38.00 7.21 7.34
Ash 9.98 5.08 5.50 6.00 10.14 5.26 6.17

Note: The ingredients of diets for experiments I and II are as composed in table 1

For experiment II there was no significant difference in milk yields for the treatments without- and with-cassava (table 3). The % butterfat for each of the diets without- and with-cassava was 4.2% (table 3). The liveweight of the cows on rations A and B were 483 kg and 481 kg respectively, the difference not being significant.

Intake and digestibility: Results of dry matter and organic matter intake and digestibility of the different diets with- and without-cassava in each of the experiments are summarized in tables 4 and 5.

Table 3. Mean milk yield and butterfat content of cows on maize and cassava root meal based concentrate diets


Milk/butterfat

Experiment I

Experiment II

A

B

C

A

B

Milk yield (kg/day) 11.7 11.1 11.6 11.3 11.1

SEM
+0.27
+0.16

F-test
NS
NS
Butterfat % 3.7 4.0 3.7 4.2 4.2

SEM
0.09
0.00

F-test
NS
NS

Notes: The ingredients of diets for experiments I and II are as composed in table 1
SEM = standard error of mean, NS = not significant

Table 4. Mean Intake and digestibility of concentrate diets by steers


Factor

Experiment I

Hay

A

B

C

SED

Dry matter intake (kg/day) 7.4a 10.7b 11.3b 11.2b 0.5
Organic matter intake (kg/day) 6.6a 9.9b 10.4b 10.3b 0.4
Dry matter digestibility (%)a 48.7 nd nd nd
Dry matter digestibility, hay + concentrate (%) nd 52.3a 57.8a 57.7a 2.6
Dry matter digestibility, concentrate alone (%) nd 61.4a 67.1a 67.1a +4.7
Organic matter digestibility (%)a 52.7 nd nd nd
Organic matter digestibility, hay + concentrate (%) nd 58.2a 60.7a 60.6a 2.5
Organic matter digestibility, concentrate alone (%) nd 63.2a 68.7a 68.7a 4.6

Notes: The ingredients of diets for experiment I are as composed in table 1 Means with different letters within a row are significantly different (P < 0.50)
SED = standard error of difference, nd = not determined
a Digestibility of hay alone was Included in the ANOVA

Table 5. Mean intake and digestibility of concentrate diets without cassava by steers


Factor

Experiment II

Hay

A

B

SED

Dry matter intake (kg/day) 3.7a 8.2b 7.8b 0.3
Organic matter intake (kg/day) 3.3a 7.6b 7.2b 0.3
Dry matter digestibility (%)a 46.8 nd nd
Dry matter digestibility, hay + concentrate (%) nd 57.3a 59.1a 2.3
Dry matter digestibility, concentrate alone (%) nd 66.1a 68.0a 3.4
Organic matter digestibility (%)a 51.3 nd nd
Organic matter digestibility, hay + concentrate (%) nd 59.6a 61.5a 2.1
Organic matter digestibility, concentrate alone (%) nd 66.1a 68.3a 3.0

Notes: The ingredients of diets for experiment II are as composed in table 1
Means with different letters within a row are significantly different (P < 0.50)
SED = standard error of difference, nd = not determined
a Digestibility of hay alone was included in the ANOVA

Discussion

It is evident from the nonsignificant differences in milk yield and butterfat (table 3) that cassava could replace maize totally in concentrate rations for lactating dairy cows. This was not surprising considering the nonsignificant differences in total dry matter and organic matter digestibility coefficients of the diets compounded from cassava and maize sources. It is clear from tables 4 and 5 that higher levels of cassava (up to 570 g/kg of the concentrate diet) had no adverse effect on DM and OM intake and digestibility of the rations. Similarity in digestibility coefficients of DM and OM in diets containing 0, 21 and 42 % CRM had been reported by Ahmed (1977). Recently Abate (1983) noted that total substitution of maize with cassava in weaner beef calf concentrate feed had no significant effect on DM digestibility.

The nonsignificant differences in milk yield and butterfat content by cows offered diets without- and with-cassava is in line with reports of Mathur et al. (1969) who found that cassava could totally replace oats in the concentrate feed. Bristocke et al. (1981) studied the effect of replacing barley with cassava up to a level of 400 g/kg in the concentrate supplement for dairy cows and found that feeding them with cassava generally increased milk yield, but this was not apparent in the present experiments. Brigstocke et al. (1981) observed that feeding cassava to dairy cows produced no significant reduction on butterfat content. Similar results are obtained in the experiments reported here.

Since the cows were evaluated on the basis of milk yield, it could be expected that cows on diets with cassava received almost the same amount of concentrate feed as those on diets without cassava. The saving from inclusion of cassava in the concentrate ration varied according to the prevailing prices of the feed ingredients. Taking the price of dry chips at Ksh 2.50/kg and maize at Ksh 3.30/kg (1988 prices), total substitution of maize with cassava (diet A vs diet B in experiment II) was associated with a reduction in the cost of the feed ingredient of Ksh 328 (US $18) per tonne. The same costing procedure revealed that the feeds with cassava were cheaper (Abate 198 1, 1983) and that the weight gain of calves which received cassava over 8 months after supplementation was not significantly different from those which were offered maize. Similarly, Brigstocke et al. (1981) noted that it was cheaper to replace barley with cassava.

In both experiments, dry matter intake and digestibility were higher with the addition of only concentrate to the rations rather than the hay dust alone. No significant differences were observed between the groups receiving concentrate.

It is concluded that cassava root meal is an acceptable ingredient in the concentrate feeds and is a complete substitute for maize in diets for dairy cows producing approximately 12 kg of milk per day.

References

Abate, A N.1981. Three different sources of energy in supplementary rations of weaner beef calves. Pages 35-42 in Animal Production Research Department annual report. Muguga, Kenya.

Abate, AN. 1983. Digestibility of weaner beef calf supplements based on maize, cassava and millet. Pages 56-66 in Animal Production Research Department annual report. Muguga, Kenya

Acland, J.D. 1973. East African crops. Longman, London.

Ahmed, F.A. 1977. Feeding cassava to cattle as an energy supplement to dried grass. East African Agriculture and Forestry Journal 42: 368-371.

AOAC (Association of Official Analytical Chemists). 1975. Official methods of analysis (12th edition). Washington, DC, USA.

Anon. 1984. Annual report of the Ministry of Agriculture and Livestock Development, Kenya.

Brigstocke, T.D.A, W. S. Cuthbert, M. A. Lindeman, and P. N. Wilson. 1981. A comparison of a dairy cow compound feed with and without cassava given with grass silage. Animal Production 33: 19-24.

Giger, S., and D. Sauvant. 1983. Comparison of various methods to determine digestibility coefficients of concentrates and by-products by ruminants. Pages 243-248 in Feed information and animal production, edited by G.D. Robards and RG. Packham. Commonwealth Agricultural Bureaux, UK.

Kwanchai, AG., and G.A. Arturo. 1984. Statistical procedures for agricultural research (2nd Edition). John Wiley and Sons, New York.

Lisovets, S.I., and V. Lipyenchik. 1982. Use of cassava for feeding cattle. Nutrition Abstracts Review 52 (8):2105.

Mathur, M.L., S. R Sampath, and S. N. Gosh. 1969. Studies on tapioca: effect of 50 and 100 % replacement of oats by tapioca in the concentrate mixture of diary cows. Indian Journal of Dairy Science 22:193.

Ravindra, V., E. T. Kornegay, end K S. B. Rajaguru. 1983. Utilization of whole cassava plant as swine feed. Page 13 in World Review of Animal Production.

Snedecor, G.W., and W.G. Cochran. 1980. Statistical methods (7th edition). The Iowa State University Press, USA


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