Incorporating dried chipped sweet potato roots as an energy supplement in diets for dairy cows: experiences with on-farm dairy cattle feeding in western Kenya

K Otieno, L O Okitoi*, P J Ndolo* and M Potts**

Kenya Agricultural Research Institute-Kibos; P.O Box 1490, Kisumu, Kenya

otienokenneth@yahoo.co.uk

*Kenya Agricultural Research Institute, P.O Box 169-50100, Kakamega, Kenya

**International Potato Centre (CIP), P.O Box 22274, Kampala, Uganda

Abstract

An on-farm study was undertaken in western Kenya to investigate the potential of incorporating dried chipped sweet potato roots (DCSPR), fortified with protein source from poultry droppings (PD), as energy supplement for dairy cattle. Two sites, Amagoro in Teso and Kanduyi in Bungoma District, were selected for the study. Baseline data on feeding management and milk production was collected from the study sites followed by a joint extension-farmer sensitization workshop and a subsequent participatory feed formulation workshop in which farmers selected the supplement mixture composed of DCSPR, PD, and dairy meal at the ratio of 2:1:1 to try on their farms. A total of 12 and 10 farms participated in Bungoma and Teso respectively.

Out of these, 3 farms in Bungoma and 4 farms in Teso fed 4 kg/cow/day of the supplement for a period of five weeks and recorded data on type and amount of basal feed, supplements and milk yields. In Kanduyi where Napier grass was the major basal feed, the amounts fed ranged from 3 to 21kgDM/cow/day. The introduction of the supplement mixture on one of the farms where dairy meal was being fed at 2 kg/day, improved total weekly milk yields by 50.7%. In two other farms where the supplement was being fed at 1.5kg/cow/day total weekly milk yields improved by 11.9% and 21% respectively  when the amount was increased to 3kg/cow/day. Overall, the mean milk yields which were very low during the pre-trial period improved by 32.6% during the trial phase. In Amagoro natural grazing formed the main source of basal feed complemented with Napier grass and banana pseudo stems. The amounts of Napier grass fed ranged from 2.4kgDM.cow/day in one of the farms where the sweetpotato-based supplement was not fed throughout the trial to 21kgDM/cow/day in farms that used the supplement. When the production data from one of the farms in Teso together with the prevailing market costs of feeds and farmgate milk price, was used to run a livestock feeding strategies simulation model (LIFE-SIM) in order to determine the optimum bio-economic levels of DCSPR and PD in the supplement mixture, the best strategy was found to be one involving grazing on natural pastures complemented with Napier grass at the rate of 21kgDM/cow/day in the months of December to March when the pastures are of poor quality and this being reduced to 12kg DM/cow/day from April to December. Assuming the cow calves in January, the supplement mixture should be fed at the rate of 4 kg/cow/day from December through to May, and it would not be necessary to offer dairy meal.

Keywords: extension-farmer workshop, feed formulation, feeding strategies simulation, Napier grass

Introduction

Intensively managed dairy cattle, like pigs and poultry, require diets with a high concentration of energy and protein. This is often provided by concentrate feeds. However, it is estimated that concentrate feeds comprise only 12% of all feeds in the developing world as compared to 40% in the developed countries (Anon 1997). Inspite of the low use of concentrates in the developing world, a combination of population growth, rising incomes and urbanization, has created a surge in demand for livestock products which can only be met by increased use of concentrates.  The major component of livestock concentrate feed has been cereals, with an estimated 600 million tons (32%) of the average global cereal production of 1,854 million tons produced in the period 1990-1992 being used for livestock feed (Anon 1997). In intensive production systems feed typically accounts for 60% to 70% of the production costs. With sharp increases in world coarse grain prices over the past thirty years, Livestock production is faced with high, often prohibitive prices for feed concentrates. This has spurred the development of alternative feeding systems such as the sugarcane-based feeding systems of Colombia, Cuba, Vietnam and the Philippines.

In Kenya the policy changes associated with the present public sector reforms and market liberalization have altered the access of smallholder dairy producers to livestock services and marketing outlets (Owango et al 1998). While the costs of dairy inputs have kept on escalating, the liberalization of milk markets have brought in a stiff competition with the effect that the farm gate milk prices have remained low. The high costs of conventional energy and protein sources for animal feed formulation has pushed up the cost of dairy supplements beyond the resource capability of smallholders. The consequence of this is reduction in milk yields with the effect that the farmer may not normally be able to break even. It is in view of this that there is an increasing need to look for locally available alternative sources of feed supplements that are cost effective and of high quality.

Studies undertaken by Otieno et al (2002) showed that there were higher returns when dairy cows were supplemented with a mixture of sun-dried milled sweet potato roots, poultry litter and dairy meal in a ratio of 1:2:1 compared to when they were supplemented with either 2 kg dairy meal as most farmers do in western Kenya, or 4 kg/cow/day which is the recommended rate by the extension services. This showed that there was a potential benefit in incorporating sweet potato roots and poultry droppings in dairy rations. Sweet potato roots are a rich source of carbohydrates and as such constitute an energy source when incorporated into livestock feeds. It is rich in highly digestible starch and sugars and has a positive effect on the metabolizable energy intake (Ruiz 1982). Since the chemical structure of the starch does not differ significantly with that of cereals, it can replace cereals in livestock feeds. Indeed, studies have shown that sweet potato meal is 91% as efficient as corn meal per unit of gain when used as substitute for corn in fattening diets for steers (Grimes 1941). When dried, roots are known to have 88-100% the feeding value of grain for dairy and fattening beef cattle (Morrison 1958). The wide range of protein content in roots (1.39 - 8.60%) shows that, through selection, some varieties of sweet potato can supply energy and protein equal to maize (Olumide 1992). It is also rich in carotene and is a good source of vitamin A, ascorbic acid, Vitamin B1 (also called thiamine), Vitamin B2 (also called riboflavin), Nicotinic acid (also called niacin), vitamin C, Iron and Potassium. However, they contain low amounts of crude protein, fat and fiber.

Although sweet potato roots have a high content of carbohydrates, the low levels of protein means that when it is used as livestock feed, an additional source of protein has to be included so as to meet the protein requirements of the animal. A lot of research has been undertaken in the past on the use of poultry litter as a source of nitrogen in supplements for lactating cows. Economic studies (Smith and Wheeler 1979) have shown that the nitrogen in poultry litter is utilized up to ten times more efficiently when recycled through ruminants as a feed compared to its use as a fertilizer. It contains considerable amounts of nutrients, particularly nitrogen. The crude protein (CP) content varies between 14.6 and 30.0% on dry matter basis depending on the source (Smith and Wheeler 1979; Kayongo and Muinga 1984). About 50% of the CP is true protein while uric acid constitutes a little more than half of the total non-protein nitrogen (NPN). In general, poultry litter can supply 30 - 90% of the protein requirements of ruminants and is rich in minerals, particularly calcium and phosphorus. Studies by Kayongo and Irungu (1986) have shown that inclusions of broiler litter of upto 30% substituting all cotton seed cake as protein source in supplements for lactating heifers on Rhodes grass leys, does not reduce milk yield. Odhuba et al (1986) also showed that broiler litter when included upto 30% as a source of nitrogen in semi-intensive feedlot rations had no adverse effect on dry matter intake or digestibility of the ration. All the supplemented steers gained at a significantly (p<0.05) higher rate and had better carcass grades than the non supplemented animals. The study also concluded that sunflower seed cake could be replaced almost completely by broiler litter in rations for finishing steers.

The purpose of this study was:

(i) to expose farmers to the existing knowledge and methodologies regarding incorporating sweet potato roots and poultry droppings into dairy rations
(ii) to use farmer knowledge of their production systems and adapt this information to their specific circumstances
(iii) to evaluate socially and economically the potential of the new system compared to existing dairy feeding procedures, and
(iv) to create awareness of the results within a wider community of farmers and extension workers.

Materials and methods 

Study sites

The study was undertaken in two selected sites in Bungoma and Teso Districts. The selection of sites was based on (i) availability of a good number of dairy cows (ii) availability of sweet potato with farmers (iii) presence of frontline livestock extension staff for project implementation and follow-ups. The selected study site in Bungoma District was Bukembe location in Kanduyi Division. The location had strong women groups undertaking dairy projects and it was also well covered by frontline livestock extension officers who were a valuable link for project implementation. The site in Teso was selected from two adjacent locations (Kamuriai and Amagoro). The area falls within the lower midland zone two (LM₂) which is a marginal sugar cane zone with a long cropping season and lower midland zone three (LM₃), a cotton zone with a medium to long cropping season.

Baseline data collection

Once the project sites in each District were agreed on, physical visits were made to the sites to select the actual farm households. These were selected on the basis of the farmer having dairy cows (lactating or in-calf) and growing sweet potato. Some baseline data on land use and livestock inventory was then collected from each of the selected households using a pre-designed data sheet. All the farmers who had been selected in each Division to participate in the project were invited for a one day extension-farmer sensitization and training workshop. The farmers were accompanied by at least two frontline livestock extension staff from the same Divisions. The workshop had the objectives of (i) introducing the project, its objectives and implementation strategies (ii) reviewing the current status of dairy feeding management in the Districts (iii) providing the participants with the available information on sweet potatoes and the use of sweet potato roots in livestock feeding, and (iv) developing, in a participatory manner, the action plans. In a way, the workshop was also a means for creating rapport for future interactions during the project implementation.

In order to gain more insight into the livestock feeding practices and strategies in the selected sites, each of the selected farms was supplied with data sheets for recording type and amount of forage fed, type and amount of supplement fed, and milk yield on a daily basis by farmers who had earlier been trained on data recording. This preliminary data collection period of about seven weeks was also meant to give the farmers adequate practice and skills in farm data recording before the actual feeding trials.

After the preliminary data collection period, all the participant farmers were again invited for a two-day participatory feed formulation workshop. The farmers were once again accompanied by at least two frontline livestock extension staff from the same Divisions. The workshop had the objectives of (i) reviewing the experiences during the period of feeding and milk yield data collection as indicated above (ii) to learn in a participatory manner, the factors affecting milk production, and with this knowledge,(iii) formulate a dairy supplement using dried chipped sweet potato roots (DCSPR) and poultry droppings (PD). During this workshop, a number of sweet potato-based supplements were suggested by the participants. The available feeding materials in both the Divisions at that time were reviewed with the aim of developing a basal feeding package based on the available feedstuffs and a supplementation regime based on Sweet potato roots. The following feedstuffs were found to be available in various amounts depending on individual farms: Forages (Napier grass, local grass, maize stalks, maize husks, banana pseudo stems, sweet potato vines, and groundnut leaves/haulms); DCSPR; PD; commercial dairy meal and mineral salt (Mac lick super).

Formulation of supplement

At the time the study was undertaken, a 70 kg-bag of commercial dairy meal costed KES 1,050.00, which worked out to KES 15 per Kg. The aim was therefore to formulate a supplement that would cost less but without reducing milk yield. Various formulations were suggested and farmers asked to choose their preferred combinations based on resource availability in each farm. The various supplement formulations and the type and amount of ingredient in each are presented in table 1. The farmers added their own formulation (supplement E), which, according to them, was appropriate for those who could not be able to use poultry droppings. Since the recommended rate for dairy meal was 4 kg/cow/day, the total amount for each of the supplement, excluding mineral salt, was maintained at the same level, but ensuring that there was at least 1 kg of the sweet potato roots in each option.

The farmers indicated that the choice of supplements would depend on the season hence the majority chose supplement A as the most appropriate for both dry and wet season. This choice was based on the fact that although the supplement had higher levels of DCSPR, it had low levels of poultry droppings whose supply can be a constraint and no requirement for dairy meal which is expensive. However, when farmers were asked to choose the supplement which they would like to go and try immediately on their farms, they chose supplement C. The reason for this choice was that the supplement was more balanced, given that the farmers were already sensitized on the basic principles of the requirements for milk production.

Farmers harvested their own sweet potatoes and prepared their own DCSPR. The method used by the farmers to process sweet potatoes for feeding was by chipping and dehydration. This consists of chopping the roots into small pieces or chips then spreading the pieces or chips over a flat surface to expose them to sun light and wind. The moisture was extracted by evaporation to obtain a final product with a moisture content of about 15%. In order to accelerate the process, the sweet potato chips were turned and mixed regularly at least every two hours on the first day of drying, and three or four times the second day, using a wood rake.

In order to determine the optimum bio-economic levels of DCSPR and PD in the supplement mixture, the production data collected on-farm from one of the farms together with the prevailing market costs of feeds and farm gate milk price, was then used to run a livestock feeding strategies simulation model (LIFE-SIM) developed by Quiroz et. al.(2005). A series of year-round feeding options were simulated in the model to determine the one that resulted in optimal economic returns.

Results  

Baseline data from study farms

The majority of the animals in the study site in Bungoma were Friesian and Aryshire crosses with Sahiwal crosses found on three farms only. Some two Guernseys were also found on one farm. The ages of the animals ranged between 2 and 9 years old. The average milk yield for the lactating cows was 6.0 liters/cow/day, with a range of 1.0 to 10.0 litres. Only six farmers out of the twelve farms surveyed fed dairy meal, and they offered between 1.0 and 2.0 kg/cow/day. Only two farmers offered mineral salt (Maclick), while one farmer fed poultry droppings, and another farmer fed brewers waste. Silver leaf desmodium (Desmodium uncinatum) was found to be grown and fed to the cows in five farms.

The majority of the cows in Teso District (Amagoro and Kamuriai locations) were Friesian crosses with a few (4) Aryshire crosses. The average milk yield of the lactating cows was 10.5 litres with a range of between 5 and 16 litres. Only three farmers out of the ten surveyed did not feed dairy meal. The average amount of dairy meal fed per cow per day was between 0.5 and 2 kg. One farmer fed Sunflower cake while molasses was only fed on one farm. Mineral salts (mostly Maclick super-brick) was offered on all farms except one.

Pre-trial Feeding management and milk production

i) Feeding management

Pre-trial data on feeding management was continuously recorded in three farms in Bungoma for seven weeks and in four farms in Teso for eight weeks. During this period, the major source of basal feed in Bungoma from the month of July onwards, was grazing on natural pastures complemented with Napier grass. The amount of Napier grass offered ranged from  2.4 kgDM/cow/day to 10.2 kgDM/cow/day. Other sources of basal feed included chopped dry maize stalks, maize husks, local grass (mainly couch grass) and sweet potato vines.

In Teso, the major source of basal feed over the same period was Napier grass. The amounts offered varied from farm to farm with the lowest being 3.0 kgDM/cow/day and the highest 33.0 kgDM/cow/day respectively. The farmer who was feeding higher amounts of Napier was also offering a range of other basal feeds including maize stalks and was occasionally supplementing with dairy meal and sweetpotato vines.

In both Bungoma and Teso, the farms that offered higher amounts of Napier grass plus a range of other basal feeds tended to be those in which milk yields were higher, either because the animals were in early stages of lactation or were genetically high yielders. This shows that the quantity and quality of feeding in many farms was closely related to animal productivity. This was clearly evident in one of the farms where the total amount of fresh forage offered went down with time as the total weekly milk yield declined (Figure1).

ii) Milk yields (litres/week)

The detailed records of the lactating cows selected for monitoring in Teso and their total milk yields over the four week trial period is shown in table 2.

Two of the cows (Akapeli and Daisy) were in post-peak lactation, hence the low total yields compared to Ikakol and Akapel. The mean daily yields ranged from 6.51 to 13.4 litres/cow/day, with a mean yield of 10.4 litres/cow/day. In Bungoma detailed records were taken for three animals (table 3).

One of the cows (Neto-Maua) was well past peak lactation although it had higher yields than Maua (BGM12) which was reported to be an Aryshire cross but looked more of a local breed. Its very low mean yields are also indicative of a local breed. The mean daily yields in Bungoma ranged from 6.07 litres to 11.3 litres, with a mean yield 6.46 litres/cow/day, which was much lower than the yields recorded in Teso.

On-farm feeding trials

After the participatory feed formulation workshop, a number of farmers started feeding the selected sweetpotato-based supplement on their farms. A few farms were selected for closer monitoring and recording of the feeding and milk yield data. In each farm only one cow was selected for monitoring although the feeding was the same for all the cows in a given farm. The cows selected for the trial had to be lactating and representative of the herd (where there were more than one lactating cow). The recording started in mid-march and the majority of the cows monitored were at this time in their fourth month of lactation.

a) Kanduyi, Bungoma

The basal feed in all the trial farms in Bungoma was generally Napier grass with occasional supply of couch grass (Digitaria scalurum)  and wild sunflower, Tithonia (Tithonia diversifolia). The amount of Napier grass offered ranged from a mean of 10 kgDM/cow/day to 17.0 kgDM/cow/day (Figure 2). The amounts fed on individual farms, however, ranged from as low as 3.0 kgDM/cow/day to 21.0 kgDM/cow/day.

Dairy meal and sweet potato vines as supplements were only fed on one farm out of the three farms where complete feeding records were available. On this farm, the cow was initially being supplemented with dairy meal at the rate of 2.0 kg/day. The sweetpotato-based supplement mixture was then introduced in the third week of feeding at the rate of 3.0 kg/day, complementing the dairy meal. However, in the fourth and fifth weeks, no dairy meal was fed. The introduction of the sweetpotato-based supplement improved total weekly milk yield by 50.7% between the third and fourth week of feeding.There was, however, a slight drop in yield between the fourth and fifth week when dairy meal was not included. This shows that there was a complementarity between dairy meal and the sweetpotato-based supplement.

On another farm, the farmer had already started feeding the sweet potato-based supplement by the time the trial phase started although the amount being fed was low at 1.50 kg/day. This amount was, however, increased to 3.0 kg/day in the fourth week, resulting into an increase in the total weekly milk yield by 11.9%. Continued supplementation with the same amount gave an increase of 15.2% between the fourth and fifth week of feeding, showing an improved response over time. Similar to this farm, another farmer who was already feeding the sweet potato-based supplement by the time the trial phase started, but again at a much lower rate of 1.0 kg/day, increased the amount to 1.5 kg/day in the second week and then to 3.0 kg/day during the third and fourth weeks. When the amounts were increased from 1.0 kg/day to 1.5 kg/day, weekly total milk yield improved by 5.0%. When the amount was increased to 3.0 kg/day in the third week of feeding, milk yield increased by 21.0% between the third and fourth week and more or less stabilized at this level in the fifth week.

The mean daily milk yields during the pre-trial period for all the farms was rather low averaging 4.3 litres/cow/day. This, however, improved to 5.7 litres/cow/day during the trial phase representing 32.6% improvement. It would be interesting to see what happens if the supplementation with the sweet potato-based supplement was commenced immediately post-calving.

b) Amagoro, Teso

The basal feed in all the trial farms in Teso, unlike in Bungoma, was mainly natural grazing complemented with Napier grass and banana pseudo stems. The amount of Napier grass offered ranged from a mean of 10.0 kgDM/cow/day to 15.4 kgDM/cow/day (Figure3).

The amounts fed on individual farms ranged from 6.6 to 21.0 kgDM/cow/day, which was higher compared to Bungoma. The mean daily milk yields ranged from 6.14 litres to 14.2 litres/cow/day which was also much higher than the mean yields recorded in Bungoma.

In one of the farms cows were largely open grazed due to shortage of Napier grass for zero-grazing as a result of drought. Due to the drought, the farmer was not able to feed the sweetpotato-based supplement but relied on dairy meal. Since the amount of dairy meal offered in this farm was reasonable at the rate of 3.0 to 4.0 kg/day, the milk  yields remained stable upto the fourth week, except for a slight drop during the second and third week when the cow became sick. The drought also affected one other farm where the Napier was also affected by the Napier ‘stunting disease’ resulting into low yields. In yet another farm, banana pseudo-stems formed a major part of the basal feed. This, together with Napier grass, was offered daily in unspecified quantities. The farmer also supplemented with some dairy meal. When the sweetpotato-based supplement was introduced in the second week, there was a 12.9% increase in milk yield between the second and third week. This improved to 15.3% between the third and fourth week indicating a potential for further improvement in yield.

One farmer who was fairly innovative, was compounding his own supplement mixture which was slightly different from what was selected during the participatory feed formulation workshop. The farmer was mixing 2.0 kg of the dried chopped sweetpotato roots with 1.0 kg of poultry droppings, 1.0 kg of ground spoilt maize grains and 50 gm mineral salt. The 4kg mixture was fed in the morning and evening totaling 8 kg per day. According to the farmer, when the animal was supplemented with dairy meal alone, it took about five days before realizing any significant increase in milk yield. However, with the “own mixture”, the response was almost immediate. At the time of starting the feeding of the mixture, the cow was in its tenth month of lactation. Between that month and the eleventh month of lactation there was 87.8% increase in monthly total milk yield. This was inspite of the fact that the cow’s milk yield had started dropping by the fifth month of lactation. The animal was generally a high yielder, giving upto 18.0 litres of milk/day at calving. During the twelfth month of lactation the yields were still relatively high at between 5.14 litres and 6.9 litres/day.

Bio-economic performance

The bio-economic analysis of a series of feeding options showed the best option for the case study to be one involving grazing on natural pastures complemented with Napier grass at the rate of 21.0 kgDM/cow/day in the months of December to March when the pastures are of poor quality and this being reduced to 12.0 kg DM/cow/day from April to December. Assuming the cow calves in January, the DCSPR+DP supplement mixture should be provided at the rate of 4.0 kg/cow/day from December through to May, and it is not necessary to offer dairy meal. Table 4 shows the model outputs for the biological parameters on a monthly basis for twelve months.

The bio-economic data for the same are summarized in table 5, showing a gross margin of KES 36,310.00 over the same period.

The results show that there was still room (54% shortfall) for improving on the actual milk production given a potential lactation yield of 2,683.00 kg thereby improving on the gross margin.

Discussion

Shortage of basal feeds remains a major constraint to dairy production in both Teso and Bungoma Districts. The shortage is mainly due to lack of grazing land and the seasonal availability of forage as influenced by rainfall patterns. The small parcels of land averaging 5.0 acres and 6.5 acres for Kanduyi and Amagoro respectively, have to be shared between various crop enterprises which include: maize, sorghum, fingermillet, sweetpotato, cassava, cotton, beans, groundnuts, fodder crops, vegetables and, in addition, sugarcane in the case of Kanduyi. The seasonality of feed supply, especially natural grazing, is also a major constraint in the absence of fodder conservation. The period between August 2004 and November,2004 and that between December 2004 and March,2005 were the most critical periods when most of the farmers in Kanduyi were affected by drought (figure 4). Although the monthly total rainfall was much lower in Amagoro, the pattern was similar to that in Kanduyi. In both sites there was hardly any farm where feed conservation was being practiced.

Although Napier grass is an important complementary feed to grazing in both Districts, the levels offered were in some cases very low.  During the preliminary feeding period, levels as low as 2.4 kgDM/cow/day and 3.0 kgDM/cow/day were recorded in Kanduyi and Amagoro respectively. There was, however, an improvement during the trial phase with the lowest levels being 6.0 kgDM/cow/day in Kanduyi and 6.6 kgDM/cow/day in Amagoro. In farms where higher levels of upto 21.0 kgDM/cow/day were being offered, there was evidence of wastage. This calls for a need to conserve the excess fodder on such farms and also adopt proper feeding management. The use of banana pseudo stems as a complementary feed was common in some farms in Amagoro, particularly during periods of drought. Although banana pseudo stems, with an ME content of about 9.0 MJ/kg, can form a good source of energy, its dry matter intake is restricted by the high moisture content (less than 10%DM) and moreover, its crude protein content at about 7.0 % of dry matter is also low. However, just like dry maize stalks and husks, banana pseudo stems play an important role in filling the basal feed gaps.

Although there was some evidence of farmers supplementing their cows with dairy meal and mineral salts, the practice was not consistent. The amounts of dairy meal offered were generally low ranging between 1.0 kg and 2.0 kg/cow/day. The most common mineral salt used was the mineral block and it was not easy to estimate the amount consumed per cow/day.

It is evident that the main feeding practice for dairy cows in Kanduyi and Amagoro is semi-zero grazing and it relies largely on natural pastures and Napier grass as the two major sources of energy. The quantities and qualities of these feedstuffs is often limiting at farm level and it is therefore unlikely that animals would be able to achieve a total daily dry matter intake (DMI) above 1.5% of their body weight throughout the year. For an Aryshire cow weighing roughly 500 kg live weight, this would be equivalent to a DMI of 7.5 kg/day. Assuming such an animal yields 10.0 litres of milk/day, it would require about 105.0 MJ ME/day. A DMI of 7.5 kg would provide about 60.0 MJME/day, assuming the average metabolizable energy (ME) content of the grass is 8 MJ ME/kgDM. This leaves a deficit of 45.0 MJ ME which has to be met from other sources. If one assumes that sweetpotato roots has ME content of about 9.0 MJ, the 2.0 kg offered in the supplement chosen by the farmers in this study would provide 18.0 MJ ME/day which still leaves a deficit of 27.0 MJ ME. This deficit can be met either with an additional 3.0 kg/day of the dried sweetpotato roots or about 2.0 kg/day of dairy meal. The fact that there is still an additional energy requirement after supplementing with the 2 kg DCSPR is confirmed partly by the fact that there was better performance on farms where the DCSPR was complemented with dairy meal.

The two major sources of protein during the feeding trial were poultry droppings (PD) and dairy meal. The crude protein (CP) content of PD has been reported as varying between 14.6 and 30.0% on dry matter basis depending on the source (Smith et al 1979; Kayongo and Muinga 1984). The PD used during this study may have varied in quality from farm to farm, but was mostly from local birds with a few farmers using PD from commercial layers. Assuming on average a CP content of 20%, the 1.0 kg PD added to the DCSPR provided 200g of CP. When this is converted to digestible crude protein (DCP) using the equation, %DCP=0.929%CP-3.8, as suggested by Holter and Reid (1959), this is equivalent to 151gDCP/cow/day. The 500 kg live weight Aryshire cow discussed earlier would require 348gDCP/day. This leaves a deficit of 197gDCP/day. In farms where at least 1 kg of dairy meal was fed, this supplied an additional 150g CP(104.6 gDCP/day). The deficit then becomes 92.4 gDCP. This can be bridged by an additional 1.0 kg of either PD or dairy meal.

Given the scarcity of basal feed and the need to provide the animals with sufficient energy and protein for both maintenance and milk production, the semi-zero grazing system remains the appropriate feeding practice in these farms. Under such a system, natural grazing would be the major source of energy complemented with at least 6.0 kgDM of Napier grass/cow/day. To supplement the energy from grazing and Napier grass, provision of 2.0 kg DCSPR plus 2 kg dairy meal/cow/day is recommended. An addition of 2.0 kg PD/cow/day to the mixture would be the major source of protein, the balance being met from the 2.0 kg of dairy meal fed.

As observed in Teso, the level and intensity of dairy cow feeding by farmers tends to be closely linked to cow productivity, in this case milk yields. High yielding cows are either those of good genetic quality or those in the early stages of lactation. Generally the majority of the farmers do not have good quality cows and are therefore not keen on going an extra mile to feed them. In cases where the cows were relatively high yielding, levels and intensity of feeding was high, with a variety of feeds being offered. Some of the feeds may not be of high nutritional value but they play an important role in meeting the dry matter deficits and mineral deficiencies, given the low levels and inconsistent mineral supplementation. For example, Tithonia diversifolia (wild sunflower) leaves which were being fed in two farms in Teso, has mean levels of CP (19.8%), Calcium (2.0%) and Phosphorus (0.3%) comparable to the mean levels in Leucaena leaves (CP=25.9%; Ca=2.36%; and P=0.23%), which is a major forage legume.

Conclusion 

• It is evident from the study that where the main feeding practice for dairy cows is semi-zero grazing which relies largely on natural pastures and Napier grass as the major sources of energy, the quantities and qualities of these feedstuffs at farm level is often limiting and it is therefore unlikely that animals would be able to achieve a total daily dry matter intake (DMI) above 1.5% of their body weight throughout the year.

  
  

• In such a situation where the cost of commercial dairy meal is also prohibitive, the energy and protein deficit can be effectively met by supplementing with dried chipped sweet potato roots fortified with poultry droppings.

Acknowledgements  

The authors thankfully acknowledge the logistical support provided by the Centre Director, KARI-Kakamega on behalf of the Director KARI. The study was financially supported by the International Potato Center (CIP), Kampala Office for which the authors are most grateful. It would not have been possible to accomplish the study without the dedication of the farmers in Kanduyi, Bungoma and Amagoro, Teso who participated in the feeding trial. We equally appreciate the support provided by the District Livestock offices in both Bungoma and Teso Districts and particularly the roles of Mr. G Sudi and Mr. J M Okisegere in farmer mobilization and monitoring of the trials.

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Received 17 January 2008; Accepted 22 February 2008; Published 10 June 2008

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