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| Livestock Research for Rural Development 20 (8) 2008 | Guide for preparation of papers | LRRD News | Citation of this paper |
The demand for energy and animal protein among rural communities in South Africa is increasing on a daily basis. The inflation rate has resulted in many rural people having no disposable income to afford a balanced diet. Attempts by government to supply these people with food have proved costly. However, the majority of households in these rural communities keep Nguni goats mainly for meat production. The aim of the study was to assess whether indigenous Nguni and Boer Goats produce high quality milk that can be used as nutritional supplement in rural communities namely two groups of Boer Goats, one o which was intensively feed and the other extensively feed. Two groups of Nguni goats were similarly treated. Milk samples from all four groups were analysed using Milko-scan 103: F.P.L., apparatus model 102, F.P.
The results obtained indicated that the intensively managed goat does had a maximum milk fat yield of 8.79 + 2.58% and 8.86 + 3.68% in weeks 1 and 8 for Boer and Nguni does respectively. The Boer goats in the intensive feeding system yielded a maximum of 6.48 + 2.11% lactose in week 9, whilst a maximum lactose content of 6.95 + 2.47% was recorded during week 10 for Boer goats in the extensive feeding system and 8.86 + 3.68% and 7.48 + 4.52% were recorded for Nguni goats (intensive and extensive, respectively) during the same week (week 8 and 6). Boer goats does fed intensively yielded maximum and minimum mean milk protein contents (%) in weeks 4 and 6 respectively, whilst the same breed under extensive feeding, yielded maximum and minimum protein contents during weeks 5 and 9, respectively. The intensively fed Boer and Nguni goats showed a peak mean milk SNF content in weeks 2 and 8 respectively, whilst the extensively fed animals reached their maximum values during weeks 10 and 6 (Boer and Nguni goats does respectively). It can be inferred from the results obtained that milk from these two types of goats is of high nutritional values.
Keywords: lactose, milk fat, protein, rural, solid non-fat
The majority of the people in South Africa live in rural areas (Aliber et al 2005). There is an increase in urban poverty as a result of an ever increasing rural to urban migration. The majority of these populations depend on social grants and informal business (Ortmann and King 2007) for survival and a balanced diet is not within their financial reach.
Most rural communities in South Africa inherited livestock from their parents. Common livestock inherited are beef cattle (of the Nguni breed of cattle), sheep and goats (Boer goats and Nguni goats). Of particular importance are goats because they provide three major products. The Nguni tribes (the Zulu, Xhosa etc) use their goats mostly for meat, milk and skin production but milk consumption from goat is not popular in other parts of South Africa. On the other hand the Venda, Pedi and Tsonga readily use goat milk for their household requirements (Casey and Van Niekerk 1988).
It is well known that goat milk is more nutritious than cow milk, hence can provide the much needed nutrients for children and people living with HIV/AIDs especially from poor rural communities (Beck 1989). The therapeutic properties of goat milk have long been researched, especially for infants (Egwu et al 1995). Goats are resistant to drought and require less fodder than cattle. They also reproduce faster than cattle. Indeed goats can play a very important role in milk supply in the rural areas provided there is proper management of goat milk production. This is one of the reasons why goats are sometimes referred to as the “poor man’s cow” (Steele 1996).With poverty, malnutrition and a growing population in the rural areas of South Africa being the order of the day, solutions have to be found to help feed and provide a possible source of income to these people (Mmbengwa 1999).
Goat milk is richer in iron than human, cow and sheep milk (Beck 1989), but poorer in copper (Steele 1996). It has a selenium content (1.25 g/100 ml) similar to that of human milk, but higher than that of bovine milk (Steele 1996). This aspect could be important, as selenium is an “anti-oxidant” factor reported to contribute toward the prevention of cancer and cardiovascular diseases (Steele 1996).
A fair amount of work has been carried out in different countries on the composition of goat milk. The composition and characteristics of milk from different breeds of goats from various countries have been reported by many authors (Haenlein 1980), (Jenness 1980). Most reports on the composition of goat milk give the analysis of milk from a single goat or a small number of animals (Mba et al 1975, Storry et al 1983, Merin et al 1988).
The objective
of this study was to determine the quality of Boer and Nguni goat milk with
respect to macro-nutrients such as protein, milk fat, lactose and SNF. The
aim was to establish whether the use of this milk should be recommended for
rural communities.
The study was conducted at two different locations. Extensive and intensive groups of animals were kept at Paradys Experimental Farm (UOFS) and the small-stock building on the campus of the University of the Free State, respectively. The experimental farm is situated approximately 20 km south of Bloemfontein. It is located at latitude of 28.34° south, longitude of 25.89° east and an altitude of 1412 metres above sea level. The small-stock facility is situated near the building of the Faculty of Agriculture on the main campus in Bloemfontein. This location is also 1412 metres above sea level. The relative humidity varies between 40 and 90%, whilst the mean annual rainfall varies between 500 and 550mm and occurs predominantly during the summer months of December to April.
Thirty-six multiparous does were used for this study. These animals were divided into four groups, namely 18 (2x9) Boer goats and 18 (2x9) indigenous feral goats does. Two groups were subjected to an extensive natural low-energy feeding regime whilst the other two groups were put on an intensive high-energy feeding regime. Each doe in the intensive feeding regime received 2000g/day of ram and ewe feed, whilst the extensive feeding groups were allowed to graze at adlib. The does were randomly allocated to the groups according to breed, with an equal number of Boer and Nguni feral goats in each feeding regime.
The animals in the intensively fed (high-energy) group were subjected to this particular diet for two weeks prior to the collection period. Thereafter, the data was collected from all the extensive and intensive feeding systems at the same time during the week. During the experimental period, clear fresh water was always freely available.
The intensive group was fed a lamb, ram and ewe pellet diet from Senwesco Feeds Ltd. The intake was recorded daily by subtracting the weight of individual feed refusals from the total amount of feed offered to the individual animal. The extensive group was allowed to graze freely on animal pasture. The pasture consisted of 80% red grass (Themeda triandra), 15% of a species of finger grass (Digitaria eriantha) and weeping love grass (Eragrostis species) and 5% of other minor species. In this group, feed intake could naturally not be measured. Water was freely available to all the animals.
Milk yield was measured twice a week for each group from within one week following parturition until the 100th day of lactation. Prior to the first milking, the kids were separated from the dams for a two-hour period. Then, just before the commencement of the first milking, the kids were allowed to suckle the dams adlib for 45 minutes, after which they were separated from the dams. Immediately after the kids were separated, the first milking commenced. Each doe was injected with 1 ml oxytocin (Fentocin) intramuscularly, 5 minutes before milking. Thereafter hand milking was performed in order to empty the udder. The second milking followed after an interval of two hours, once again, after an injection of 1 ml of oxytocin. The output of the second milking was used to measure the milk production of each doe.
Milk samples from the Tuesday and Friday milkings of the extensive group and samples from the Monday and Thursday milkings of the intensive group were stored in a refrigerator at 4°C until analysed. This was done to allow the researcher to collect samples from the extensive group on Wensday and Fridday. The milk samples were analysed for milk fat, protein, lactose and solid non-fat using a Milko-scan 103: F.P.L. apparatus model 102, F.P. A beaker filled with 200 ml deionised water (40°C) was placed in the apparatus under the pipette to activate the process. All the components of the milk were measured and displayed. A note was made of each milk component namely fat (F), protein (P), lactose (L), and solid non fat (SNF). The activation and full measurement cycle were repeated three times and the average for each component was calculated. This analysis was carried out at the laboratories of the Dairybelle Company in Bloemfontein, 10 km from the University of the Free State.
The mean percentages of protein, fat, solid non-fat and lactose in the milk were analysed using one-way ANOVA with treatments in a 2x2 factorial design. Data analysis was carried out using the general linear models procedures of the Statistical Analysis Systems Institute (SAS 1991).
The results are shown in figure1 below.
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As shown in figure 1 above the intensively managed does had a maximum milk fat yield of 8.79 + 2.58% and 8.86 + 3.68% in weeks 1 and 8 for Boer and Nguni does, respectively.
However, the intensively managed Nguni goat does produced the highest milk fat mean (7.47 + 3.23%) for the entire observation period, compared to all the treatment groups (figure 1). On the other hand, the extensively managed Boer goat group (6.39 + 2.08%) produced the second highest milk fat mean content.
It was also observed that the extensive group showed a maximum milk fat yield of 8.16 + 1.85% and 7.48 + 4.52% in weeks 1 and 6 for Boer and Nguni goat does, respectively, whilst the intensively managed counterpart produced the least milk fat (4.76 + 1.8% and 5.93 + 1.55%) in weeks 6 and 1 for the Boer and Nguni goats, respectively.
>From these results, it can be inferred that the type of feed and breed had a significant (P<0.01) effect on milk fat, with intensively managed Nguni goat does yielding more milk fat than the Boer goat does in an intensive nutritional system. In the extensive system, the Boer goat does produce more milk fat than the Nguni goat does. An overall correlation coefficient (r) of 0.073 was observed between milk yield and milk fat.
The lactose content of goat milk
The results are shown in figure 2 below.
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From figure 2 above, the Boer goats in the intensive feeding system yielded a maximum of 6.48 + 2.11% lactose in week 9, whilst a maximum lactose content of 6.95 + 2.47% was recorded during week 10 for Boer goats in the extensive feeding system and 8.86 + 3.68% and 7.48 + 4.52% were recorded for Nguni goats (intensive and extensive, respectively) during the same week (week 8 and 6).
The minimum mean lactose contents (4.78 + 1.26% and 4.73 + 0.37%) for Boer and Nguni goats under extensive conditions were noted in week 2. In the intensively managed goats, the lowest levels were observed during the first and the last weeks (week 1 and week 12) for the Boer and Nguni does, respectively (4.76 + 1.80 and 4.93 + 0.47). The Nguni goat does under the intensive feeding regime produced the highest mean daily milk lactose content (8.86 + 3.68%), compared to the other treatment groups.
>From these results, the feeding regime was found to have a significant (P<0.01) effect on the lactose yield, with the intensively fed animals recording a higher lactose content. The Boer goat does generally yielded a higher lactose percentage than the Nguni goat does in both nutritional management systems. Boer goat does therefore showed a trend of producing higher milk lactose content throughout the trial. A correlation coefficient of r = 0.103 was found between lactose content and the mean daily milk yield for the entire experiment. This is in agreement with various previous findings (Haenlein 2004).
The protein content in goat milk
The results are shown in figure 3 below.
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The mean milk protein content (%) per week for Boer and Nguni goat does under different nutritional management systems is shown in figure 3 above. Boer goats does fed intensively yielded maximum and minimum mean milk protein contents (%) in weeks 4 and 6 respectively, whilst the same breed under extensive feeding yielded maximum and minimum protein content during weeks 5 and 9, respectively (figure 3).
The intensively fed Nguni goats’ protein yield was highest and lowest in weeks 8 and 9, respectively. The extensively fed Nguni goats produced maximum and minimum milk protein percentages in weeks 6 and 9 respectively.
The Boer goat extensive group yielded the highest mean daily milk protein percentage (4.95 + 1.95%). Feed had a significant (P<0.01) effect on the milk protein content in the Nguni goat does, with the intensive group having a higher milk protein content than the extensive group. The Boer goat does on the extensive feeding regime yielded higher milk protein content than the intensive group. The production of protein varied throughout the trial, with either one of the breeds exceeding the other at various stages. A correlation of r = 0.125 was recorded between milk protein content and the mean daily milk yield.
The solid non-fat (SNF) content of goat milk
The results are shown in figure 4 below.
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The intensively fed Boer and Nguni goats showed a peak mean milk SNF content in weeks 2 and 8 respectively, whilst the extensively fed animals reached their maximum values during weeks 10 and 6 (Boer and Nguni goats does respectively). The minimum mean milk SNF content was observed in weeks 6 and 9 respectively for Boer and Nguni goat does in the intensive feeding system (Figure 4).
The Boer goats in the extensive group produced the highest mean daily milk SNF content for the entire period (10.69 + 5.13%), followed by the Boer goats in the intensive group (10.42 + 6.47%). The Nguni goat does of the extensive group produced the lowest milk solid non-fat content with a mean daily content of 9.55 + 1.90%.
These results
show that type of breed plays a significant (P<0.01) role in SNF content, with
the Nguni goat intensive group having the highest milk SNF content. The
production of SNF content (%) varied throughout the observation period for both
breeds in the different feeding systems, with indigenous Nguni goat does
(intensive group) producing more than all the groups during weeks 5, 10 and 11
(Figure 4).The correlation coefficient between mean daily milk SNF content (%)
and mean daily milk yield was r = 0.271.
Several researchers have researched the composition of goat milk and compared it with milk from other species (Parkash and Jenness 1986, Jenness 1980). The fat, protein, SNF and lactose contents of milk depend largely on the volume of milk produced (Zygoyiannis 1988). These constituents of milk determine the value of the milk. The production of goat milk has traditionally been of major importance in several countries where climatic conditions are not favourable for cattle production and dairy farming.
In addition, increasing importance has in recent years been attached to the role goat milk can play in human health if included in the diet. It can often be tolerated by children and infants who suffer from hypersensitivity (allergy) to cow milk. This is due to the fact that the average diameter of the fat globules in goat milk is only 3.5 mm. Merin et al (1988) has indicated that the composition of goat milk varies somewhat and is a function of several factors such as breed, the stage of lactation, climatic conditions, diet and the season of the year.
The Nguni feral goat does produce the highest mean fat content (7.5 + 3.2%) with a mean milk yield of (l.42 + 1.37 ℓ/day). The Boer goat does, on the other hand, produced a mean fat content of 6.1 + 2.2%, with a higher mean milk production of 3.1 + 1.5 ℓ/day. This observation agrees with the findings of Flamant and Morand-Fehr (1982), who indicated that a high level of milk production is associated with a lower fat content of the milk. Zygoyiannis and Katsaounis (1986) also found the trend towards a lower milk fat content in goats with a higher total milk yield. Similarly, Simos et al (1996) found a negative correlation between higher milk yield and fat content. Working with Indigenous goats in Germany, Gall (1981) found that the overall values of the measured milk constituents, especially fat, were related to the milk yield of the goats. It was further indicated that the amount of milk fat could be related to both the genetic potential of the goats, and to the comparatively low milk yield associated with the nutritional environment (Gall 1981).
The 7.5 + 3.2% milk fat content of the intensively housed Nguni goats was lower than the 12% mean daily fat content of Indigenous goats (Capra prisca) cited by Zygoyiannis (1987), but higher than the 4.75% and 3.37% reported by Ehoche and Buvanendran (1983) and Muggli (1981), respectively.
Whilst the value of 6.1 + 2.2% mean fat content recorded for Boer goat does was lower than the 6.9 + 0.1% mean daily milk fat content cited by Akinsoyinu et al (1977), this value (6.9 + 0.1%) was also higher than the fat content reported by Lythgoe (1940) and Mitchell (1962) for goats and than that cited by Adeneye et al (1970) for White Fulani cows, though it was lower than the 7.5% reported for ewe’s milk (Ling et al 1961).
These values are in turn lower than the 7.5 + 3.2% found for the Nguni goat does in the intensively fed group investigated in this trial. The lower goat milk fat content in other goats is attributed to the smaller proportion of acetic acid and larger proportion of propionic acid in the rumen (Armstrong and Blaxter 1964, Mba et al 1975, Morand-Fehr and Sauvant 1980).
The major carbohydrate in goat milk is lactose (Chandan et al 1992). In this study, the highest mean lactose content of 5.0 + 0.7% was produced by Boer goat does which were managed intensively. This value is higher than the values of 4.5% and 4.66% reported by Chandan et al (1992), but lower than the 5.83% in native Greek goats reported by Simos et al (1991).
Boer goats maintained under intensive conditions produced a maximum and minimum mean milk lactose content in weeks 5 and 1 of the lactation period, respectively. This concurs with the findings of Singh and Sengar (1990), who stated that milk lactose content declined with a decrease in milk yield, as the lactation period progressed. In their study all the breeds showed a decline in milk lactose content as the lactation period progressed.
In the same study, the milk lactose content exhibited variations between the 7th week and the end of lactation (Simos et al 1996). In the present study such variations were observed one week earlier. This confirms the fact that milk lactose is positively correlated with milk yield, which is known to be significantly (P<0.05) influenced by the feed status of the animal.
Interest in the protein content of milk is growing. Human health concerns in respect of animal fats have resulted in the development of a milk processing system that places less economic emphasis on milk fat, but more emphasis on milk protein (De Peters and Fergurson 1992, Hadjipanayiotou 1995). The Nguni goats showed very high levels of milk fat and protein compared to the Saanen goat (Donkin 1998).
The mean concentration of protein in goat milk is 4.5% (Zerfas et al 1992). In this trial, the milk of the Boer goats on the extensive feeding regime had a maximum and minimum mean milk protein content (7.21 + 4.91% and 3.65 + 0.53) in weeks 11 and 6 respectively. The Nguni does (extensive group) also attained maximum and minimum levels (5.61 + 3.84% and 3.81 + 0.65%) during approximately the same time, namely in weeks 11 and 4. However, figure 3 shows that the intensively managed breeds, achieved maximum and minimum levels of mean milk protein at different periods in lactation. Milk protein content, together with the other milk constituents (except lactose), increase as the lactation period progresses (Singh and Sengar 1990).
Agnihotril and Prasad (1992) have also found the protein, fat and total solid content in Jamanapari and Barbari goat milk to be more than in the milk of the European goat breeds. This could be the case, as these breeds are low milk producers (0.75 and 0.6 kg/day, respectively), compared to the European goats (Akinsoyinu et al 1977).
These researchers also report a mean daily protein content of 3.91 + 0.01%, which is less than was found in this study (4.20 + 0.97%, 5.03 + 2.96%, 4.95 + 1.96% and 4.54 + 2.79% for Boer and Nguni goats in intensive and extensive environments). The protein content did, however, not differ significantly between different breeds and feeding regimes.
The composition and characteristics of goat milk from different breeds and countries have been reported by many authors (Haenlein 1980, Jenness 1980). Most of these reports do not place much emphasis on the SNF content of the milk. Simos et al (1991), working with native Greek goats, recorded a mean SNF content of 14.12%, which is higher than the values recorded in this study.
With the highest mean SNF content (10.69 + 5.13%) produced by Boer goats which grazed on natural pasture for the entire experiment, it is possible that the SNF content of milk is determined by genetic factors in the breed, rather than the energy intake of the animal.
In this study
the Boer goat group, under extensive feeding conditions, had a mean daily milk
production of 0.78 + 0.67 kg. This quantity was the second lowest when
compared with other groups but this breed yielded the highest SNF content,
together with high fat and protein content, which are usually negatively
correlated with milk yield. In the present trial it was found that the
breed has a significant (P<0.01) influence on SNF content, with Boer goat does
yielding a higher SNF content that the Nguni goat does under their respective
feeding systems.
Without the
contributions of the University of the Free State and the National Research
Foundation (SA), this study would have not been possible. Furthermore, wish to
thank the UNISA language services.
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Received 4 October 2007; Accepted 22 May 2008; Published 5 August 2008
