The analyses show large variations in most of the production traits studied: nevertheless, the data support earlier suggestions that the Kenana might be among the most productive African dairy breeds. Although, for reasons which have already been discussed, growth and reproductive performance were not outstanding in the herd over the period studied, results from specific short-term studies of cattle under improved nutrition show that the performance of Um Banein cattle compares favourably with that of other Kenana herds and with other breeds.
An important point emerging from the analyses is that a large proportion of the variation in the major production traits can be accounted for by effects of year and year-group. Most traits showed improvement throughout the 1960s, but deterioration during the 1970s. Some traits then apparently showed a slight improvement during the 1980s.
The effects of management and climate are clearly important in the context of these analyses. A consideration of the rainfall (Figure 2) does not explain fully the variation in the traits, but a consideration of the livestock numbers (Figure 6) shows that the pattern would seem to be related to the very high stocking rates in the 1970s, which would have reduced the nutritional levels of all stock.
The destocking implemented since 1980 appears to have had a beneficial effect, despite a further reduction in the carrying capacity of the farm due to declining rainfall, irrigation problems and lack of funds for purchased feeds and fertilizers.
Excessive stocking rates not only reduced productivity per cow, but also total farm productivity. Table 29 illustrates this point in its comparison of 1969, the year with the highest performance, and 1979, the year with the highest stock numbers. It is therefore important that the station management should match stock numbers to the carrying capacity of the farm, taking into account the probable supply of home-grown fodder and the budget available for purchased feeds. These management policies should be related to immediate short-term possibilities as well as to a longer term plan.
Table 29. A comparison of cattle productivity and milk production in "best" and "worst" years at Um Banein.
|
Year |
Total cattle |
Total calvings |
Total milk production (kg) |
|
1969 |
430 |
175 |
366 625 |
|
1979 |
700 |
145 |
212 280 |
Variations due to management could also be minimised by reducing the rapid turnover of research staff. It is appreciated that some transfers and promotions are required, but in order to limit the disruptions due to these, it would seem preferable to define management guidelines for the longer term.
Herd size and structure
Culling policy
Calf rearing
Heifer rearing to first calving
Dairy cow management
In view of the importance of matching stock numbers to feed resources, the recommended herd size would be about 430 cattle, including 180 adult cows (Table 30). The cow herd could be increased to 220 without increasing total numbers if age at first calving were to be reduced to 3 years.
A carrying capacity of 430 cattle assumes that the pumping equipment currently being installed will operate satisfactorily on a permanent basis and that the station budget will not decrease in real terms; at present (January 1986) the station can only support a total herd of 200 animals and the increase in herd size to 430 head should only be attempted gradually, as and when fodder availability is assured.
Table 30. Suggested total herd size and composition at Um Banein.
|
Class of stock |
Herd composition |
|
|
% |
numbers |
|
|
Adult cows |
42 |
181 |
|
Heifers (3-4 yrs) |
10 |
42 |
|
Heifers (2-3 yrs) |
11 |
46 |
|
Heifers (1-2 yrs) |
12 |
50 |
|
Calves (0-1 yr)a |
23 |
101 |
|
Breeding and replacement bulls |
2 |
10 |
|
Total herd |
100 |
430 |
a Both sexes.
The data show that in the past a large proportion of culling has been due to such reasons as disease, digestive problems and infertility rather than due to milk production per se, although rather more culling on production has occurred in recent years.
Most disease and digestive problems appear to have been overcome as preventative animal health measures have become part of the normal management routine. Large numbers of animals have been culled for infertility in the past and although this might remain a major reason for culling, especially in older animals, the number of maiden heifers and younger cows in the breeding herd has been very high; this would seem to be related to the pre-1985 policy of keeping all females regardless of the dam's yield.
A new policy, implemented since 1985, was the culling of female calves from low yielding dams immediately after birth, unless they were needed as replacements.
A strict system of culling adult cows based on a "Most Probable Producing Ability" (MPPA) should now be followed, those animals with the lowest index being culled.
The MPPA is calculated as:
where
n = Number of records for the individual
r = Repeatability of the trait
In this formula, individual production records should be adjusted for lactation number, then expressed as deviations from herd-year mean and then averaged. Selection and culling policies based on this index would then be as outlined in Table 31. This system is to be recommended in that it gives a framework for culling on milk yield rather than the ad hoc basis apparently used previously. Bull calves not required for the herd or for distribution should be sold as soon after birth as possible, as should heifers not required as replacements.
The low calf weaning weights underline the importance of good calf management. Weaning at 60 days can be recommended to maximise profit. Milk should be given at the rate of 10% and 8% of liveweight for the first and second month respectively. Special attention to the nutrition of weaned calves (i.e. 4 to 12 months old) is recommended to avoid deaths. This applies especially to those calves born in the wet summer and being reared over the winter and hot summer.
Research at Um Banein shows that a concentrate is required and that molasses-based supplements do not appear to be capable of producing the growth rates required in Kenana calves of this age.
Heifers will inevitably be reared on a system based on the poorer forages available and so it is unlikely that maximum growth rate can be achieved economically; however, dry-season supplementation based on molasses/urea diets has been shown to support growth rates that allow heifers to calve first at 36 months old and this should be adopted as station policy. Improved nutrition will also help to improve the poor reproductive performance.
An important point arising from the analyses is the importance of matching stock numbers to feed resources not only in the long-term but also in individual years. Subjecting dairy cows to prolonged nutritional stress reduces annual production, and in this context the dry summer is the most critical period at Um Banein. One of the easiest ways to overcome the shortage of good-quality feed is to conserve sorghum as high-quality silage rather than as low-quality straw. If straw has to be fed, adequate supplementary feed should be provided. Minerals, which have been used only sporadically, should be provided routinely.
The shape of the lactation curve at Um Banein implies that feeding pre- and immediately post-parturition is inadequate and that high-quality forage and concentrate should be provided during these periods.
Table 31. Proposed selection policy for Um Banein based on "Most Probable Producing Ability" of cows.
|
Herd |
Percentage of herd |
Current yield(kg)a |
Destination of calves group
|
||
|
|
range |
||||
|
Elite ('E')
|
10
|
2107
|
1725-2760
|
Bulls: |
stud at Um Banein, other stations or nucleus herds |
|
Heifers: |
Um Banein herd |
||||
|
'A'
|
30
|
1568
|
1445-1724
|
Bulls: |
distribution in traditional sector |
|
Heifers: |
Um Banein |
||||
|
'B'
|
30
|
1161
|
800-1444
|
Bulls: |
curled for meet |
|
Heifers: |
culled (unless numbers from 'E' end 'A' groups insufficient to maintain Um Banein herd) |
||||
|
Low yielders ('L')
|
10
|
342
|
5-799
|
Bulls: |
culled |
|
Heifers: |
culled |
||||
|
(Cows: |
culled as soon as numbers in other groups sufficient) |
||||
|
First calf heifers |
20 |
- |
- |
|
- |
a Station average yield currently assumed to be 1445 kg.
The drop in production after the sixth lactation implies that most cows should be considered for culling at that stage unless in the 'E' or 'A' groups.
Two-month weaning
Post-weaning growth (weaning to 1 year)
Heifer rearing
Genetic potential of the kenana
Supplementary feeding
Reproduction
The research carried out at Um Banein should be of an applied nature aimed at helping producers overcome the main constraints on milk production. Surveys in the Singa area and at the Gezira Dairy Co-operative (Devine, pers. comm.) have shown that cows do not produce to their genetic potential in farmers' herds and that feeding is the principal factor limiting milk production. Thus research and development on applied nutrition should be the priority.
Some aspects requiring further study are listed below.
Further studies should be carried out to provide information on the types and quantities of forage and concentrate ingredients which can be used in this system. Earlier weaning may also be attempted.
At present, results indicate that a concentrate is needed to maintain adequate growth rates and that molasses-based diets are not adequate; further work on the most cost-effective concentrate is required.
Heifers will normally be reared on rainfed grazing and crop stubbles, with irrigated fodder being used for milking cows and calves; thus work should continue on dry-season supplementation. Molasses/urea-based diets have been shown to be useful in this respect and further studies should be carried out in addition to trials on treatment of crop residues.
The current analyses show that the true potential of the Kenana is still not known. A trial should thus be carried out on a group of 'E' cows using high-energy (sorghum grain) and high-protein concentrates together with ad lib green fodder or silage for a complete lactation cycle. A parallel trial could also be conducted using the other main Sudanese breed, the Butana: animals from Atbara Research Station should be brought to Um Banein for this comparison.
Such an experiment can only be carried out if adequate funding is provided, and at present the station cannot carry out such work due to lack of funds. (Work is possible with calves and heifers as the additional cost is small.)
A series of trials should be carried out to assess production from ad lib feeding of the main forages, alone and with varying levels of concentrate, to establish the response curves to concentrate feeding in the Kenana. Further studies should also be carried out on the total amount and the distribution of concentrate feeding over the whole lactation.
The fact that fertility and fecundity appear to be higher in the hot summer than in other seasons warrants further study as it seems to conflict with the observed effects in most other areas of similar ecology and with related types of cattle.
