Milk production and economic impact of strategic supplementation of prepartum Bunaji cows in the peri-urban areas of derived savanna of southwestern Nigeria

O A Olafadehan and M K Adewumi*

Department of Animal Production Technology, Federal College of Wildlife Management, P.M.B. 268, New Bussa, Niger State
oaolafadehan@yahoo.com
^*Department of Animal Science, University of Ibadan, Ibadan
mkadewumi@yahoo.com

Abstract

Twenty prepartum Bunaji cows with an average weight of 295±3.72 kg balanced for their parity and weight were used to investigate the effects of dry season supplementary feeding during the last trimester of pregnancy on the milk production and economic benefit of such intervention in an on-farm experiment. A completely randomized design was used with 4 treatments: A, range grazing (RG) only (control); B, RG + maize bran (MB); C, RG + MB + PKC (palm kernel cake) and D, RG + MB + DBG (dried brewer’s grains). There were 5 cows per treatment. The feeding trial lasted for last trimester of pregnancy while milk production was measured throughout lactation.

Supplemented cows produced higher milk (P <0.05) than their non-supplemented counterparts at various stages of lactation; 3months, 6months and weaning. Among the supplemented cows,  total milk yield (TMY) was more (P <0.05) pronounced in cows on treatment D than those on treatment B. Yields of milk constituents followed the same trend as the milk yield. TMY was significantly (P< 0.05) and directly related (R² = 0.97) to the lactation length. Net economic benefit was best in supplemented cows on treatment D and least (P <0.05) for grazing non-supplemented cows on treatment A.

The results underscored beneficial effects of strategic supplementation of prepartum cows in a smallholder dairy production system.

Key words: agroindustrial by-products, cost-benefit, lactation, milk yield, smallholder dairy production

Introduction

Small-scale dairy production around densely populated urban centres is expanding in sub-Saharan Africa and elsewhere in developing countries in other regions. Domestic milk production in Nigeria is largely by smallholder agropastoral producers who often settle around the major cities and sell their dairy products in urban centres (Ehoche et al 2001). Although the demand for dairy products in the country is high (Jansen 1992) and estimated cattle population is also high (FLD 1993), milk output from smallholder systems is low.

 Inadequate feed supplies remain a major constraint to sustainable cattle production in general, and milk production in particular, in smallholder production systems. In the emerging peri-urban dairy production systems, poor quality of feed resources has invariably resulted in low milk production (Adewumi 1997).  Although producers in these production systems face a host of constraints to production, inadequate nutrition among milking animals, especially during the dry season, is considered one of the major limitations to dairy productivity (Olafadehan 2007). Inadequacy relates to both quantity and quality. Protein is usually the limiting factor but energy can be critical in certain periods; so is mineral deficiency (Kapu 1975; Lufadeju et al 1987; Adamu et al 1993). This is because the quality of range vegetation which is the major feed resources for agropastoral herds fluctuates due to seasonal pattern of forage growth. The grasses which are mostly annuals, are nutritious at the beginning of the rains but with the onset of dry season there is rapid decline in nutrient contents especially nitrogen and phosphorus (Ehoche et al 2001). At this time, the low quality of natural pastures and the inefficient use of fibrous crop residues result in inadequate feeding of the stock with adverse implications on reproductive efficiency and milk production as feed nutrients become inadequate to support the potential yield of the animals  (Preston and Leng 1984; Adamu et al 1993). Thus, the nutritional requirements of dry-pregnant and lactating cattle for milk synthesis and let-down are not sufficiently met. It is therefore generally recognised that for cattle dependent on range forages, supplementary feeding with additional protein sources at an affordable cost is essential during the dry season. Due to relatively cheap price and availability of agroindustrial by-products such as maize bran (MB), palm kernel cake (PKC) and dried brewer’s grains (DBG), they can be used to alleviate the problem of inadequate nutrition and boost the productivity of grazing cattle.

 The study was therefore designed to (1) examine the effects of dry season supplementation with agroindustrial by-products on the milk production of pregnant Bunaji cows under agropastoral production systems and (2) determine the economic benefits of feed supplementation of agropastoral herds.

Materials and methods 

Study area

The study was conducted on-farm among the agropastoralists settled in the peri urban areas of Oyo town in the derived savanna of Oyo State which has been reputed to have the highest concentration of agropastoral farmers in south-western Nigeria (Okoruwa 1994). It lies roughly between longitude 3^○ 4^/ West, 6^○ 4^/ East of Greenwich and latitude 6⁰ 10^/ and 9⁰ 10^/ North of the equator. The study area is bounded in the north by the southern guinea savanna zone and in the south by the interface between the lowland rain forest and southern parts of the derived savanna. Annual rainfall is between 1,500 and 2,000mm and follows a bimodal distribution. The temperature ranges from 22 - 33⁰C while the wet season lasts for 8.0 - 8.5 months starting from mid-March to mid-November. A peri-urban area is the area lying within a circle of a maximum of 25 km radius from the outskirts of the specified urban centre (Mohammed 1990).

Cattle management practices of the agropastoralists in the study area

Milk production in the study area is based largely on indigenous Bunaji cattle breed kept by Fulani herdsmen who grow food crops in addition to their primary cattle herding activities. Food crops commonly grown include maize, sorghum, millet and cowpea while dominant forages and browseable plants include Andropogon spp, Hyperrehenia spp, Pennisetum spp, Daniella oliveri, Tephrosia spp, Mimosa spp, Afzelia Africana and Parkia spp. Cattle are herded to the fields in the morning  after milking to graze natural forages and crop residues. They are returned in the evening and corralled during the night in the open field, near the homestead. Unweaned calves are tied by ropes to separate them from their dams. Cows are partially milked once a day in the morning, the remainder of the milk being suckled by the calves.

Experimental animals, design and management

Twenty (20) gestating dual purpose dairy Bunaji cows in their 2^nd and 4^th lactation with average weight of 294.50 ± 3.75kg were used for the experiment. The cows were selected when they were in the last trimester of their pregnancy which was determined by interviewing the herd owners. The cows were balanced for weight and parity (lactation number) and separated into 4 groups of 5 cows each. The groups were randomly assigned to 4 treatments: range grazing (RG), A; RG + 100% MB, B; RG + 60% MB + 40% PKC, C and RG + 60% MB + 40% DBG, D in a complete randomized design.

Supplements were offered individually, early in the morning before grazing throughout the last trimester of pregnancy spanning February to May 2003, at 20% of the daily dry matter intake calculated at 3% body weight which represents a nutritional stress period when forage is scarce and of low quality while the crop residues on range are exhaustively grazed. After feeding, animals were grazed on natural range. Common salt was offered to individual animals throughout the experimental period. Supplement or feed intake was estimated as the difference between what was offered and rejected after each day feeding. However, feed refusal was very small and virtually negligible as all the cows finished their feed before going out for grazing.

Milking procedure

Milking of the cows began one week after calving to allow calves access to colostrum, but milk production records began two weeks after calving and continued throughout lactation which was taken as the time the dams dried up or calves were naturally weaned as practised under traditional systems of management. The daily milk offtake (ie extractble milk for human consumption) record which was taken at two weeks intervals, in one litre measuring cylinder, was averaged and multiplied by 30 to obtain a monthly offtake for each dam. Hand milking was done in the morning between 0.700 to 0.800 hours local time while calves were used to initiate milk let-down. Partial milking was done in order to reserve milk for sucking calves which were prevented from sucking the dams while on range by a means of Fulani apparatus called “Toide” that was placed around the calf neck.  Estimated milk yield (MY) at 3 months, 6 months and weaning was calculated from the sum of the milk offtake (MO) and calf’s growth (CG) x 9 (Agyemang et al 1993). Calf’s growth x 9 gave the estimate of the milk consumed by the calves.
 

Milk Yield = Milk Offtake + (Calf Growth x 9).

Milk samples for constituent analysis were collected once every two months into bottles containing a pinch of potassium dichromate (K₂CrO₄) powder to maintain homogeneity and prevent clotting. The samples were kept chilled later and analysed for milk components.

Cost-benefit analysis

The cost of the supplementary feeds consumed by the animals throughout the feeding trial was computed for each cow. Monthly milk yield for each cow was aggregated over the entire lactation period. While the feed was costed at the prevailing market prices as at 2003, milk was priced using the producers’ prices in order to quantify the net benefits from the feeding intervention.

Chemical analysis

The proximate constituents of the experimental diets were determined according to AOAC (1990) methods. Gross energy contents of feeds were determined using Gallen-Kamp ballistic bomb calorimeter (Modal CB- 370). The neutral detergent fibre and acid detergent fibre components were determined by methods of Van Soest et al (1991). Milk samples were analysed for total solids, butterfat, crude protein, ash and lactose using the procedures of AOAC (1990).

Statistical analysis

Data were analyzed using the procedure of statistical analysis software (SAS 1999) and treatment means were compared using Duncan’s procedure of the same software. Relationship between milk yield and duration of lactation was determined using correlation and regression analyses.

Results and discussion 

The proximate composition of the supplemental diets is presented in Table 1. The crude protein contents of the supplemental diets B, C and D, respectively, were higher than the 11% recommended for dry-pregnant cows (NRC 1988). The gross energy values of the diets which increased progressively from treatment B to D were fairly similar. Addition of PKC and DBG to MB appears to improve the nutritive quality of MB.

At 3 months of lactation, total milk yield (TMY) was significantly (P< 0.05) lower in the non-supplemented control group A compared to the supplemented groups B to D (Table 2). Among the supplemented groups, although TMY was highest in group D, it was similar to that of group C but significantly (P < 0.05) lowest in group B. The TMY values were lower than the milk yield values of 424 and 369 kg reported by Otchere (1986) and Mohammed (1990) for Bunaji cows at 3 months of lactation under traditional systems of management. The disparity in the milk yield could be due to variations in the rations used as supplements and parity of the experimental animals.

TMY at 6 months of lactation differed (P < 0.05) among the treatments (Table 2). It was significantly (P < 0.05) higher in supplemented cows on treatments C and D than in the non-supplemented control group A which produced similar quantity of milk as cows on treatment B. However, TMY was not influenced by supplement types as yield was similar among the supplemented cows. The significantly higher milk production of supplemented cows than their non-supplemented counterparts could be attributed to their improved plane of nutrition during pregnancy. Steaming up has been reported to improve milk yield of the animal in the ensuing lactation (Foot et al 1963; Sial and Shah 1968; Ogunsiji 1974; Otchere 1986; El-Tayeb and Takla 1992 and Akinnusi 2001).  TMY values were much lower than the value of 550kg at 6 months of lactation indicated by Otchere (1986) for prepartum supplemented Bunaji cows in the northern guinea savanna of Nigeria. The differences in the milk yield could be due to variations in the environmental conditions, season and the milking techniques, which depend on the milker’s experience and discretion.

TMY at weaning, which gives the milk production per lactation, was superior (P < 0.05) in supplemented cows on treatments B, C and D compared to those without supplementation on treatment A (Table 2). Moreover, milk yields of cows on treatments C and D were comparable but higher than that of cows on treatment B. While the TMY values of 436 – 591 kg /cow/lactation in present study compared favourably with the value of 531 kg/cow/lactation reported by (NAPRI 1995), it was higher than the value of 281 kg/cow/year obtained by Otchere (1986), but lower than the milk yield value of 640kg/cow/lactation indicated by Mohammed (1990) for traditionally managed Bunaji cows. The variations in milk yield/cow/lactation could be as a result of differences in the lactation length of the animals, frequency and intensity of milking. The better milk yield of supplemented cows was obviously a response of the animals to extra nutrients and energy consumed by them unlike the non-supplemented cows that depended solely on the lignified, less digestible and inadequate forages available during the critical dry season. The significant differences observed in milk yields among the supplemented cows is a reflection of the quality of concentrate rations used as supplements which has been demonstrated to affect the milk production of traditionally managed Bunaji cows (Otchere 1986; NAPRI 1995; Agyemang et al 1998 and Agyemang 2000).

Except at 6 months of lactation while milk yield of supplemented cows on treatment C was higher than that of those on treatment D, milk yields at 3 months and weaning (ie milk yield per lactation) were consistently highest for cows in group D possibly because the diet had highest amount of crude protein and energy (Table 1) which are essential for building up body reserves needed for milk synthesis during pregnancy and lactation. It has been confirmed that milk production during lactation depends on the degree of body reserves build up or fatness during pregnancy because lactating animals rely on their body reserves for milk synthesis during the ensuing lactation (Moe and Flat 1969 and Moe et al 1971). Though not reported in this report, estimation of the body condition or degree of fatness of the experimental cows during pregnancy followed the same trend as the total milk yield per lactation. Also, the diets contained dried brewer’s grains which contain high amount of undegradable protein, making them a good source of rumen by-pass protein (Merchen et al 1979) that remains intact and becomes available in the abomasum and small intestine where they are utilized by the animals.

Total milk yield per lactation was positively and significantly correlated (r = 0.98, P < 0.01)) with cow’s lactation length. The best-fit regression equation (R² = 0.97) for predicting milk yield from the lactation length of the cow is shown in Figure1.

The highly significant contribution of lactation length to total milk yield is supported by various reports on Bunaji cows and other cattle breeds (Camoens et al 1976; Adeneye and Bamiduro 1985 and Adeneye 1993).  Adeneye (1993) reported that lactation length is a major determinant of milk production, though both the period of calving and lactation number also had recognizable effect.

Yield of milk constituents

Mean milk yields of milk components, total solid (TS), fat, solids-not fat (SNF), lactose, ash and gross energy are presented in Table 3.The amount of TS of milk of 397, 430 and 451 g/day for supplemented cows on treatments B, C and D, respectively was significantly (P < 0.05) higher than those of the non-supplemented cows on treatment A (343 g/day).

Variations also existed in the amount of TS produced among the supplemented cows with yields being higher (P < 0.05) for cows on treatment D than B which produced similar amount as cows on treatment C. Non-supplemented cows in group A produced lower amount of butterfat compared to the supplemented groups B, C and D. The yields of butterfat in groups C and D were similar but considerably (P<0.05) higher than the butterfat yield of group B. Non-supplemented cows in group A produced less amount of SNF than the supplemented cows in groups B - D. Variations in the amount of SNF produced among the supplemented cows were not significant. Yield of milk protein, which varied (P <0.05) among the treatments, followed the same trend as yield of TS. Unlike milk protein, prepartum supplementary feeding of Bunaji cows had no discernible effect on the quantity of ash (minerals) produced during lactation. Lactose yield was similar among the supplemented cows but was higher (P < 0.05) in treatments C and D than treatment A which produced similar amount as treatment B. Yield of gross energy followed the same trend as the yields of TS and protein.

Average daily yields of the various milk components were consistently higher for supplemented cows compared to non-supplemented cows. Among the supplemented cows, average daily yields for the various milk components were consistently highest for Bunaji cows on dietary treatment D because the diet favoured highest milk yield. The mean daily yields of milk constituents by Bunaji cows obtained in this study were lower than the values reported by other workers (Adebowale 1976; Apori 1988 and Belewu 1995). This was due to the lower milk yield values obtained in this study. The differences in daily yields of milk constituents are largely due to the variations in the milk yield which, in this study, must have been affected by differences in the composition of the experimental diets fed to the cows and genetic milk production ability of the cows. As the dietary CP increased from 12.98% in B to 15.49% in D, milk protein yield increased correspondingly from 110 to 127 g/day or by 17 g/day which is lower than 38.30g/day reported by Tona (1999), as the difference in the yield of milk protein among supplemented Bunaji cows, probably due to differences in the rations fed. It was also lower than 67.18 g/day obtained by Davies (1992) possibly because of breed differences among the lactating cows. A much higher increase in milk protein yield of 180g/day reported by Dhiman et al (1993) is largely due probably to differences in the rations and breeds of animals.

Net benefits of supplementary feeding of gestating grazing Bunaji cows

Comparative cost advantage of feed supplementation of in-calf grazing Bunaji cows is shown in Table 4.

Cost of feeding was significantly (P<0.05) higher in cows on treatment B than for those on treatments C and D which were similar. Cost of feed per kilogramme of milk produced was similar for treatments C and D which was significantly (P<0.05) less than treatment B. Using surveyed producers’ price of N120/litre of fresh milk, the value of milk yield was significantly (P<0.05) affected by prepartum supplementary feeding. Even among the supplemented cows, value of milk yield was significantly (P<0.05) better in treatments C and D than in treatment B. Net benefit was significantly (P<0.05) higher in supplemented cows than in non-supplemented ones. While net benefits were similar for cows on treatments C and D, it was significantly (P<0.05) more in these two treatments than for cows on treatment B. Differential and relative benefits followed similar pattern with cows on treatments C and D recording similar benefits but superior to that of treatment B (P<0.05) whose benefits were significantly higher compared to that of control group A.

Cost of feed per kilogramme of milk produced showed that treatment D was more economical since animals consumed less amount of feed to produce more milk. This could be attributed to the fact that the animals consumed the least amount of feed and produced highest quantity of milk. Net benefit was higher in supplemented cows compared to their non-supplemented counterparts.  Among the supplemented cows, net benefit was highest for cows on treatment D. The higher net economic benefit in supplemented cows over and above that of non-supplemented cows was a reflection of the higher milk yield resulting from the supplementary feeding. Differential benefits showed that cows in supplemented groups B, C, and D had higher benefits of N 8, 625.49, N 14, 604.38 and N 16, 284.15, respectively than the non-supplemented control group. Also supplementary feeding resulted in benefits 16.5, 27.9 and 31.1% higher in groups B, C and D, respectively than in the control group. This implies that benefits as much as 16.5 to 31.1% could be made by supplementary feeding of gestating grazing Bunaji cows. The differences obtained in net benefits among the supplemented cows were a reflection of the effect of quality and price of feeds used as supplements. It is thus important to take these two factors into consideration when grazing animals are to be supplemented. Treatment D with highest quality due to highest CP and energy contents gave the highest benefit. The result is in line with the findings of Otchere (1986), Agyemang et al (1998), Ouologuem et al (1999) and Agyemang (2000) but contradicts that of Ehoche et al (2001). The cost of feeding the animals and the milk yield might likely be responsible for the variations in results. Agyemang et al (1998) reported 5 to 8 fold margin of milk yield value over feed cost when home-grown forage legumes were used to supplement Bunaji cows.

Conclusions 

• Supplementary feeding of gestating Bunaji cows in the last trimester of pregnancy under agropastoral  management systems significantly improved their milk production.

  
  

• Cost-benefit analysis based on milk yield gave highest net economic benefit in cows supplemented with 60% MB and 40% DBG    

  
  

• The results showed that adoption of agroindustrial by-product supplementation of  prepartum Bunaji cows  would increase the income of smallholder dairy farmers.

Acknowledgements 

The assistance of Mr. A.A. Busari of International Livestock Research Institute, Ibadan, Nigeria in locating the agropastoralists and supervising the field work is herby acknowledged.

References 

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Received 1 November 2007; Accepted 17 December 2007; Published 1 March 2008

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