J.A. RILEY, K. AGYEMANG, R.H. DWINGER, P. JEANNIN, A.S. GRIEVE and D.A. LITTLE
Introduction
Materials and methods
Results
Discussion
References
The Gambian national herd of some 300,000 N'Dama cattle, represents a resource which could make an important contribution to the nutrition of the rapidly growing human population. The cattle are still kept in a traditional system of semi-extensive management as described by Dunsmore et al., (1976). It is common for cattle owners to employ herdsman who receive the milk produced twice daily as payment for their services. This naturally leads to a conflict between the well-being of the calf and the "earnings" of the herdsman. In certain herds, notably those belonging to members of the Fula tribe, cows are milked in the mornings only. The calves are allowed to suckle the dams in the evening prior to tethering overnight.
At present, the productivity of cattle kept under this traditional system of management is rather low. Calf mortality in the first year of life approaches 20%. Surviving calves grow very slowly, weighing as little as 70 kg at one year of age. In a ten-month lactation, cows will produce approximately 300 litres of milk for human consumption. Mature animals may lose up to 25% of their body weight during the dry season. Very few heifers calve before four years of age and calving intervals may be over twenty months.
One of the most important factors contributing to this low productivity is poor nutrition. The production system relies on grazing on native pastures/bush throughout the year. During the long dry season between November and June, forage becomes very scarce. Early in the dry season, some crop residues become available for grazing in the fields following harvest, but these are insufficient to prevent dry season weight loss. Supplementary feeding of cattle is not practiced, with the exception of the provision of groundnut hay and millet bran to work oxen, whose condition must be maintained for the work season which starts at the beginning of the rains.
It seemed probable that small inputs of supplementary feed, especially protein, during the dry season would substantially improve the overall productivity of N'Dama cattle. Particularly susceptible to limited feed intake and quality are animals with high nutrient requirements, such as lactating cows and very young calves. Therefore, in January 1987, feeding trials began in three villages in The Gambia to assess responses throughout the dry season to small inputs of a protein supplement in recently calved cows and in young suckling calves.
The experiments took place in the villages of Pirang, Keneba and Nioro Jattaba. Pirang has a low trypanosomiasis risk and is situated in the coastal Combos region of The Gambia. Nioro Jattaba and Keneba, both in the Kiang area, have a low-to-medium trypanosomiasis risk. Nioro Jattaba is a Fula village in which cows are milked only once each day, while in the other two villages the Mandinka owners are accustomed to having their cattle milked twice daily.
In Pirang and Keneba, the effect of supplementation on the growth rate and survival of young suckling calves was studied. Forty-five calves born between August and December 1986 were used in each village. The calves were divided into three treatment groups of 15 animals each, which were balanced as far as possible for initial liveweight, age and sex. The treatments were no supplementation (TO), 300g of groundnut meal/week in three meals of 100g (T1) and 600g of groundnut meal/week in three meals of 200g (T2). The calves were fed their supplements in individual plastic bowls on Mondays, Wednesdays and Fridays or Tuesdays, Thursdays and Saturdays. All animals had access to a mineralized salt lick. Blood samples were taken once each month for determination of PCV percent and for examination for trypanosomes. The animals were weighed monthly on electronic scales. No other changes in traditional village management were made. Feeding started in January 1987 and continued until late June of the same year.
Recently calved cows were used for supplementation trials in Nioro Jattaba. Group 1 consisted of 69 cows which had calved between August and December 1986. These were divided into three treatment groups according to initial liveweight and calving date. One group received 1 kg of groundnut meal three times each week (T1), the second group received 2 kg three times each week (T2) and the third formed the control group (TO). Feeding commenced in January 1987 and continued until the end of June 1987. A second group of animals (Group 2) consisted of 69 cows. They had calved between September 1986 and February 1987. They were divided into three treatment groups as described above. Group 2 was supplementary-fed from the end of March 1987 until the end of June 1987.
Weights were recorded of the dams and their calves on a monthly basis. Blood samples were also taken for determination of PCV and identification of trypanosomes. The volume of milk extracted for human consumption was measured on one occasion each month. All experimental cows and their calves had access to mineralised salt licks. The rainy season began with a storm on June 7th but feeding continued until all measurements for the month had been completed. Data were analysed by least squares (Harvey, 1977).
Keneba trial
A total of four animals left the experiment during the five-months feeding period. No results from these animals were included in the final analysis of data.
Total weight gained during the five-month experiment was from 13.2 kg in the control group to 18.5 and 18.1 kg for T1 and T2, respectively. This difference was not significant (P>0.05). Feeding the calves had no significant effect on the amount of milk extracted from their dams for human consumption. Likewise, supplementation had no clear effect on the changes in PCV shown by the calves as the dry season progressed.
Pirang trial
The calves were initially very reluctant to eat the supplement provided. By April most calves had begun to eat but a few refused to do so throughout the entire experiment. Only data from those animals which were eating well by the end of the experiment were included in the analysis. The rates of liveweight gain were not significantly different between the treatment groups; in fact calves in T2 performed no better than the control group. The rate of growth of calves in Pirang which did not receive any dry season supplement was considerably better than that of similar calves in Keneba. This was presumably due to the higher rainfall in the Pirang area than in Keneba during 1986 (1296 and 598 mm, respectively).
Nioro Jattaba trial
Group 1
The provision of groundnut meal to lactating cows during five months of the dry season had a highly significant effect on the amount of body weight loss. Total weight loss was reduced from 38 kg (17% of initial liveweight) in the control group to 30 kg (14%) in T1 and 18 kg (8%) in T2. The calves of supplemented dams grew significantly faster than the calves of control dams. For example, the daily liveweight gain of the control calves over the five-month period was 110g, significantly lower than that of calves in T1 (141g/day; P<0.001). As cows in Nioro Jattaba are milked only once each day, this improvement in the performance of their calves was mainly due to the increase in milk yield (see below). The calves, however, were also seen to be eating groundnut meal from their dams' buckets. This will have contributed to the increased growth rate.
Supplementation of lactating females resulted in an increase in milk output for human consumption. Both levels of feeding helped to prevent the very steep decline in milk output observed in the control group as the dry season progressed. The increase in milk yield between May and June coincided with the beginning of the rainy season and the ensuing rapid growth of vegetation. The total yield of milk during the five-months experimental period was increased from 56.6 litres in the control group to 77.4 litres in cows receiving 3 kg of groundnut meal each week (P<0.01). The total yield of cows in T2, at 103 litres, was almost double that of the control group (P<0.001). The provision of supplementary protein during the dry season had no significant effect on the PCV levels of the cows. PCVs in all groups tended to fluctuate from month to month, but cows which were supplementary-fed seemed able to maintain their haematocrits at a slightly higher level. Only one animal was removed from the treatment groups.
It is too early to determine the effect of feeding on the reproductive performance of the cows. At the end of June herdsmen reported that a total of six experimental cows had been served: one in To, two in T1 and three in T2.
Group 2
Both levels of supplementation with groundnut meal during the last three months of the dry season reduced weight loss by 10 kg. As in Group 1, feeding the cows improved the growth performance of their calves. For example, daily liveweight gain was improved from 119g in the control group to 153g in T1 (P<0.05) and to 171g in T2 (P<0.01).
Milk yield throughout the experiment was increased from 45.9 litres in the control to 55.6 litres (P<0.05) in cows receiving 3 kg of groundnut meal each week and to 59.1 litres (P<0.05) in T2. Three cows left the experiment in Group 2, one from each treatment group.
It is interesting to note that the milk extracted from control animals was higher in Group 2 than that of similar animals in Group 1 during the same period. The reason for this is not known, as all aspects of management were very similar. In Group 2, the differences between T1 and T2 were not statistically significant for any of the production parameters recorded.
The differences in weight gain between the control group and the two treatment groups of calves in Keneba were not significant, although the daily rate of liveweight gain during the five-months feeding period was increased by about 40% by both treatments. It must be said, however, that the level of supplementation was extremely low. Calves in T1 received only about 6.3 kg and those in T2 about 12.6 kg of groundnut meal during the whole feeding period. In this context, the supplement was used very efficiently for growth. At first sight this response seems promising, but in fact the performance of all calves in Keneba was very poor compared to that in other villages. The increased growth rate of the supplemented calves was due, almost entirely, to a loss of weight in the control group between March and April. The depression in growth between March and April in the control group coincided with an increase in the amount of milk extracted by the herdsman from the dams of this group of calves. It is possible that any benefit of supplementation will be lost during the subsequent rainy season.
The effect of poor rains in Keneba on the availability of vegetation was compounded by several bush fires which destroyed large areas of standing hay. Efforts to discourage burning of bush, for whatever -purpose, may have an important effect on the productivity of cattle in Keneba. The population of cattle in the Kiang area, however, is not excessive and large amounts of groundnut hay in the vicinity had not been used by the time the rains began. This could be used profitably for the feeding of calves with a minimum of effort by the herd owners.
In Nioro Jattaba, feeding small amounts of groundnut meal to lactating cows produced very important responses in terms of calf liveweight gain, milk yield and reduced weight loss. However, the response most obvious to the cattle owners, that in milk yield, would not on its own be sufficient to justify the feeding of groundnut meal. This supplement costs one dalasi (D) per kg at the factory, not taking into account transport costs. The price of milk in Nioro Jattaba is approximately 2.25D per litre. Therefore, the value of the increased milk output was 47D in T1 and 104D in T2, respectively. On the other hand, the overall economic response is less easy to assess. Any reduction in calving interval is likely to have a large effect on the profitability of cattle production in Gambian villages. Nevertheless, it is unlikely that groundnut cake will ever be used on a large scale due to cost and distribution problems.
In conclusion, this series of experiments has shown that supplementation of suckling calves or recently calved dams has a profound effect on improving productivity of N'Dama cattle kept under traditional management conditions. However, it is probable that supplements other than groundnut cake, such as cotton seed or sesame cake, would be economically more attractive for use by the village farmer in The Gambia.
Dunsmore, J.B., A. Blair Rains, G.D.N. Lowe, D.J. Moffatt, I.P. Anderson and J.B. William. 1976. The agricultural development of The Gambia: an agricultural, environmental and socioeconomic analysis. Land Resource Study 22.
Harvey. W.R. 1977. User's guide for Least-Squares and Maximum Likelihood Computer Program. Colombus: Ohio State University.
