The economic feasibility of concentrate supplementation of lactating Sanga cows grazing natural pasture in the dry season

P K Karikari, K Asare and S A Okantah*

Faculty of Agriculture, KNUST, Kumasi, Ghana

*Animal Research Institute, C.S.I.R., Achimota, Ghana

pk.karikari@yahoo.com

Abstract 

An experiment was carried out for 120 days to assess the economics of dry season feed supplementation in an emerging peri-urban dairy production system in the Kumasi district of Ghana.  Fifty three Sanga cows were divided into four treatment groups T1, T2, T3 and T4, and were fed 0, 1, 1.5 and 2 kg, respectively, of a home-made concentrate supplement containing 18% crude protein.  The cows were milked once a day in the mornings and allowed to suckle during the day. 

Daily partial milk yields were 1.7, 2.1, 2.6 and 2.7 L for the cows supplemented with 0, 1, 1.5 and 2 kg concentrate, respectively.  Cows fed 1.5 kg concentrate generated the highest net income from milk sales.  They produced 53% more milk and 16.6% more milk revenue than the control cows.  Their daily partial milk yield was not significantly different (P>0.05) from that of cows fed 2 kg concentrate supplement, but was significantly higher (P<0.05) than that from other groups.  It was found that feeding 2 kg concentrate supplement a day to Sanga cows in the Kumasi district may not give the best of economic returns even though milk yield may be increased.  Concentrate supplementation at the current rate and duration did not significantly (P>0.05) influence postpartum resumption of ovarian cyclicity and pregnancy rate in cows neither did it influence calf weight gain.  Given the large variability observed in individual cow performance, it was suggested that selection of more productive cows or culling of less productive ones could be used in conjunction with feed supplementation to improve milk yield and income therefrom in Sanga cows.

Keywords: beef cattle, economics, milk income, partial milk yield, peri-urban, pregnancy

Introduction

Most farmers in the Kumasi district of Ghana are crop farmers.  In recent years, however, many of them have started rearing cattle on commercial basis, even though most of the cattle enterprises in the district remain sideline activities.

The Sanga which are crosses between the N’Dama or the West African Shorthorn (WASH) and the Zebu form the bulk of milk-cattle in the Kumasi district.  The milk yield of the Sanga cow is low since the parent stock from which they come produce only 120 L to 1300 L per lactation of between 120 and 360 days (Payne 1990).  While these production figures would be discouraging in Europe, they emphasise the importance of the measures which could be taken to increase productivity of cattle in Africa. 

Like much of Africa, it is usually difficult to get enough quality feed for cattle during the dry season in the Kumasi district.  One way of improving the performance of grazing cattle during periods of scarcity of feed would be to use concentrate supplementation.  Feed supplementation could increase milk off-take and milk suckled by the calf in systems where partial milking is done (Little et al 1994).  It could also put the lactating cow in a relatively good condition, which would enhance reproductive efficiency (Tegegne et al 1992; Dhiman et al 1997; Zhang and Zhang 1998). 

The positive effect of supplementation on milk production has been widely reported (Dhiman et al 1997; Granzin et al 1998; Wohlt et al 1998).  Little et al (1994) reported that cotton seed cake and sesame oil meal fed to lactating N’Dama cows in the Gambia significantly increased milk yield.  It has also been reported that the use of supplementary urea molasses blocks during the cold season in China resulted in milk yield increases of 14% in black yak cows and 20% in white yak cows (Zhang and Zhang 1998).  Concentrates have also been used to achieve improvements in milk yield (Aston et al 1998).  However, the low genetic potential of tropical livestock and high prices of grain and oil seed cakes in many tropical countries call for a careful analysis of the economic implications of concentrate feed supplementation before farmers are advised to resort to it.  The objective of the present study was, therefore, to assess the economic feasibility of supplementing lactating Sanga cows with home-made concentrate during the dry season.

Materials and methods 

Experimental site

The experiment, which lasted for 120 days, was carried out at Kentinkrono in the Kumasi district of Ghana.  Kumasi is located at an altitude of about 290 m above mid-sea level and 06^o43’ N, 01^o36’ W of the equator.  The vegetation is semi-deciduous forest, and the climate is described as hot and humid.  The months of November to February inclusive, constitute the dry season.  The mean monthly precipitation for the dry season months is 42 mm, 23 mm, 5.6 mm and 65 mm for November, December, January and February, respectively.  The respective relative humidities are 95, 89, 83 and 41percent during the morning (06.00 h) and 57, 50, 40 and 41percent during the afternoon (15.00 h).  The mean daily temperature for the dry season is about 26^oC, but may vary from 18^oC in the night to 35^oC in the afternoon.  The duration of sunshine for the dry season is about 5.8 h.

Herd management

Sanga cows belonging to two cluster herds were used in this experiment.  Each cluster herd consisted of animals belonging to different people, but kept on the same grazing land under different herdsmen.  Cows in an area were treated as if they were managed by one person and distributed among the four treatment groups.  All the experimental animals in an area were managed essentially the same way.  They were grazed in the same area, usually between 08.30 and 17.00 h.  The animals were provided with adequate water both in the morning and in the evening.  Breeding was not controlled and occurred throughout the experimental period.  Calves were grazed with their dams, although very young calves less than two weeks old were not grazed.

All herdsmen practised partial milking.  Under this system calves were separated from their dams in the evening to prevent suckling till the next morning.  The calves were brought to suckle for a few minutes to stimulate milk let down before milking.  Milking was done only in the morning, usually before 07.00 h.  Milking usually started two to three weeks after calving.

Experimental design

Fifty three Sanga cows lactating throughout a period of four months were used in the experiment.  The cows were in two cluster herds (Herd 1 and Herd 2) at Kentinkrono in the Kumasi district of Ghana.  Cows in each of the cluster herds were grouped into four treatments T1, T2, T3 and T4 in a completely randomized design, which took their body weights into consideration.  Treatment groups T1 and T3 contained 12 cows each while T2 and T4 groups contained 14 and 15 cows, respectively.  Cows in treatment T1 received no concentrate (control).  The daily amounts of concentrate supplied to cows in treatments T2, T3 and T4 were 1, 1.5 and 2 kg, respectively.  The concentrate contained about 18% crude protein and consisted of rice bran (50%), cottonseed cake (30%), maize (16), common salt (2%) and oyster shells (2%).

Milk yield, progesterone and chemical analyses

The mean daily partial milk yield for the week preceding the experiment was calculated for each participating cow and used as a covariant in the statistical analysis.  The recording of the daily partial milk yield was continued for each cow throughout the experiment.

Milk samples from individual cows were taken twice a week for progesterone assay.  Samples were kept on ice until they were centrifuged in the laboratory at 2,000 g in a refrigerated centrifuge (4^oC).  The skimmed milk samples were kept at -18^oC until assayed for progesterone.  The FAO/IAEA solid-phase technique (IAEA 1993) was used for the progesterone assay.  The intra- and inter- assay coefficients of variation were 6.3% and 8.7%, respectively.  Progesterone levels >2.0 nmol/L in two or more consecutive samples were deemed to indicate ovarian cyclicity.  A cow which maintained high (>2.0 nmol/L) progesterone levels for more than three weeks was considered pregnant (Mohamed et al 1990).  The proximate analysis of the concentrate used was done by the AOAC methods (AOAC 1997). 

Calf weights

Calves were weighed at the beginning and at the end of the experiment to estimate body weight gain.

Statistical analysis

The statistical analyses of the data were carried out using Systat computer statistical package (SYSTAT 1990).  The data were subjected to analysis of covariance.  The terms for the covariance analysis were treatment, herd, treatment X herd interaction, and the covariant was the initial (last week before experiment) partial milk yield.  The monthly means for daily partial milk yield were also calculated.  Using the technique of regression analysis, the rate of change in monthly milk yield was determined for each cow and then for the treatments and herds.  The chi-square test was used to determine the significance of proportion of cows cycling versus those not cycling as well as pregnant versus empty cows between treatments.

Results 

Table 1 shows the proximate analysis of samples of the experimental concentrate. 

Results of the covariance analysis are presented in Table 2. 

The overall treatment means for the daily partial milk yields were 2.62, 2.24, 2.14, and 2.24 L for November, December, January and February, respectively.  The monthly mean milk yield for treatment in November was significantly (P<0.05) higher than the means for the other months.

Table 3 presents the rate of monthly milk yield decline according to treatment and herd. 

The partial milk production and net income derived from the sale of partial milk extracted during the 120-day period are presented in Table 4. 

The postpartum ovarian function of the cows and body weight gain of calves are reported in Table 5. 

Both chi-square (χ²) tests on cows showing cyclic ovarian activity versus those not showing cyclic ovarian activity (χ² = 5.95; df=3), and those pregnant versus empty cows (χ² = 3.37; df=3) were not statistically significant (P>0.05).

Discussion 

The cows in the T4 group were expected to produce more milk than they did.  The limited effect of the supplementation may be due in part to Sanga cows partitioning less of their energy for milk production.  The fact that supplemented cows produced significantly (P<0.05) more milk than non-supplemented cows suggests the need for improved feeding of lactating cows in the area during the dry months.  The significantly higher milk yield at the commencement of the dry season in November suggests that feed availability and/or quality may be better during the rainy season.  Lactating Sanga cows may, therefore, need little or no concentrate feed in the rainy season.

The results suggest that 1.5 kg of concentrate per day (Treatment T3) containing 18% CP may be the most economically viable level of supplementation for Sanga cows in the Kumasi district (Tables 2 and 4).  The daily partial milk yield of 2.6 L produced by cows in treatment group T3 was not significantly different from the 2.7 L produced by cows in T4 group, but was significantly higher (P<0.05) than the 1.7 L and 2.1 L produced by those in treatments T1 and T2, respectively.  The T3 cows also produced the highest net income from milk sales (Table 4).  T1 cows generated about cedis  177, 975/month (US$ 17.80) while T3 cows generated about cedis 207, 513/month (US$ 20.75).  Each T3 cow, therefore, generated an additional cedis 29,538 (US$ 2.95) per month compared to non-supplemented (T1) cows.  The T3 cows produced 53% more milk and provided 16.6% more revenue from milk than their T1 counterparts.  One other finding worthy of note is the fact that feeding 2 kg/day of a concentrate containing 18% CP to Sanga cows may not yield the highest net returns in the Kumasi area even though it may increase the quantity of milk for the market.  The experiment has also shown that the present plane of nutrition is inadequate even for a low milk producing cow like the Sanga to realise its potential in the dry season.  It would, therefore, seem unwise to import high yielding dairy cattle from abroad to the area if the feed situation cannot be markedly improved.  The high producing, early maturing European breeds require a high plane of nutrition, which is very difficult to provide under tropical conditions, and in any case environmental conditions are likely to interfere with the conversion of feed even if adequate standards can be maintained.

The trend of the present results was expected as higher levels of nutrition allow for higher percentages of nutrients to be available for milk production.  This is because maintenance requirements of cows are roughly proportional to their body weight, but remain fairly constant regardless of the level of milk production.  The raw materials from which milk constituents are derived, and the energy for the synthesis of some of these in the mammary glands, are supplied by the feed.  A cow fed at a higher plane would, therefore, be expected to produce more milk (Mcdonald et al 1981).

It could be deduced from the present results that substantial amounts of money could be realised if the partial milking system is encouraged and a market found for the extracted milk.  In this experiment, a Sanga cow supplemented with 1.5 kg/day of a concentrate containing 18% CP could generate about cedis 1,383,417 (US$ 138.34) net income from milk every year, if a 200-day milking period is assumed.  The effect of dairying on the local economy could, therefore, be enormous if all cows in the district were properly fed and milked.  A greater part of the potential revenue from milk is lost to the economy because many local farmers are not interested in milk production.  A campaign to bring to the fore the profitability of peri-urban dairying is, therefore, advocated.  The fact that inadequate feeding could hamper profitable dairying also needs to be stressed.  Table 3 confirms that cows are more persistent in milk production if feeding is improved.  It is possible that apart from improving milk yield, the duration of milk production may also be prolonged by proper feeding of lactating cows under the partial milking system (Matthewman 1993).  Even though the present cows did not significantly (P>0.05) differ in the time taken to resume ovarian cyclicity postpartum and pregnancy rate, some earlier reports have shown that supplemented cows can have superior reproductive performance (Little et al 1994; Dhiman et al 1997;  Granzin et al 1998; Wohlt et al 1998).

The large variability in performance observed among individual cows suggests that selection of more productive cows or culling of less productive ones in conjunction with feed supplementation could be used to significantly enhance the productivity of Sanga cows in less endowed environments.  Improved management of stock would, therefore, be necessary if the peri-urban milk industry is to succeed in the Kumasi area.

Conclusions and recommendations 

• It is concluded that with proper feeding of lactating cows, peri-urban dairying could be a significant component of the agricultural economy of the Kumasi area. 

  
  

• Researchers should, however, help to overcome the primitive trait in the Sanga which is connected with the temperamental function of milk let down to make it a more useful milk animal. 

Acknowledgements 

The authors acknowledge the substantial support of the International Atomic Energy Agency for this work.  They also desire to thank Mr F.A. Kwarteng of the Animal Science Department of the Kwame Nkrumah University of Science and Technology in Kumasi for laboratory assistance.

References 

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Received 27 July 2008; Accepted 19 September 2008; Published 5 December 2008

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