Comparative milk production potential of Indigenous and Boer goats under two feeding systems in South Africa

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1 Small Ruminant Research 55 (2004) Comparative milk production potential of Indigenous and Boer goats under two feeding systems in South Africa J.P.C. Greyling a,, V.M. Mmbengwa a, L.M.J. Schwalbach a, T. Muller b a Department of Animal Science, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa b Department of Chemical Pathology, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa Received 27 August 2002; received in revised form 20 November 2003; accepted 20 November 2003 Abstract The aim of the study was to investigate the milk potential of Boer goat and South African local Indigenous goat does, under intensive and extensive nutritional regimes. Thirty-six Multiparous does (18 Boer and 18 Indigenous) were allocated to intensive (complete diet) and extensive (natural pastures) environmental groups, following kidding. Does were hand-milked twice weekly and the milk production recorded. Body weight changes, milk fat, solid non-fat (SNF), lactose and protein contents of the milk were determined weekly. Overall Boer goat and Indigenous does produced more (P <0.05) milk under the intensive, compared to the extensive nutritional regime (3.1±1.5 l per day versus 0.8±0.7 l per day and 1.4±1.4 l per day versus 0.7±0.6l per day for the Boer and Indigenous does, respectively). The intensively reared Boer and Indigenous goat does reached peak lactation earlier (week 5). Level of nutrition had a significant (P <0.01) effect on milk production, with the intensively fed does producing more milk. The intensive Indigenous does produced milk with the highest mean fat content (7.5 ± 3.2%) at a milk yield of 1.4±1.4 l per day. Milk lactose content tended to decline as the lactation period progressed and milk yield decreased. Milk protein content tended to increase with advancement of the lactation period (mean of 4.2±1.0; 5.0±3.0; 5.0±2.0 and 4.5± 2.8% for Boer and Indigenous goats under intensive and extensive environments, respectively). Solid non-fat content was negatively correlated to milk yield. Breed had a significant (P <0.01) effect on SNF content, with Boer goat does producing a higher SNF. In the intensively maintained groups, feed intake was significantly (P <0.01) correlated to milk production, irrespective of the breed. Boer goats had the highest mean live weight (45.0±8.7 kg) and also produced the most milk. Principally the Boer goat doe can fulfill the function of providing milk to the rural, poorer communities in South Africa or alternatively be used to upgrade the Indigenous goat for increased milk production especially under improved nutritional management systems Elsevier B.V. All rights reserved. Keywords: Milk production; Goats; Nutritional regimes; Milk composition 1. Introduction With poverty, malnutrition and a growing human population in especially the rural areas of South Africa being the order of the day, alternatives in terms of a Corresponding author. Tel.: ; fax: address: lindehm@sci.uovs.ac.za (J.P.C. Greyling). source of animal protein have to be investigated. The possibility exists to look at the goat as a potential source of protein (milk and meat) and livelihood to help feed and uplift these rural communities. The high demand for goats and their products can be attributed to their hardiness and ability to survive and produce under harsh environments with low rainfall and minimal supplementation (Erasmus, 2000). The fact that goat milk also has certain therapeutic /$ see front matter 2004 Elsevier B.V. All rights reserved. doi: /j.smallrumres

2 98 J.P.C. Greyling et al. / Small Ruminant Research 55 (2004) properties has long been realized (Egwu et al., 1995). The goat, which has been identified as an acceptable and affordable source of animal protein in the form of meat and milk, with its lower maintenance requirements, compared to the cow, makes it an ideal animal for milk production by small scale farmers and rural households (Van der Nest, 1997). Goat milk production has the advantage that goat enterprises have lower capital investment requirements, concurrent with lower overall risks. As the South African Boer and Indigenous goat breeds are not generally used for dairy purposes, very little is known regarding the milk production potential these genotypes are the most abundant and freely available animals in the rural areas. These breeds are very adaptable, hardy and highly fertile and it is known that many of the rural communities milk these goats for household consumption even though these animals were not bred for this purpose (Casey and Van Niekerk, 1988). One of the main limiting factors of milk production is energy intake (Sahlu and Goetsch, 1998). It is the availability of glucose which largely controls the movement of water into milk (Gall, 1981) and milk production in goats depends on the net energy content of the forage, with green feed and pelleted hay recording a higher milk yield (Morand-Fehr and Sauvant, 1980). In practice, milk yield and composition is influenced mainly by the dietary supply of materials providing energy and protein (Thomas and Rook, 1983) something that is often deficient in rural farming systems. The main aim of this study was to determine the potential milk production (quality and quantity) of Boer and Indigenous feral does under intensive and extensive nutritional regimes. The extensive milk production regime simulated the rural small scale farming set-ups, where milk is produced off natural pastures with no nutritional supplementation. Thus in this study the goats, with their unique characteristics, are evaluated as possible milk producers to help in the social upliftment of the rural communities. 2. Materials and methods Thirty-six multiparous, lactating does (18 Boer and 18 Indigenous feral goats) with singleton lambs were used in the study. These animals were sub-divided into four groups, i.e. 18 (2 9) Boer and 18 (2 9) Indigenous does. Two groups (9 does from each breed) were subjected to an intensive (high energy) feeding regime and two groups (9 does from each breed) were subjected to an extensive, natural (low energy) feeding regime. The intensive groups were fed a pelleted diet of 2 kg per day, following an initial adaptation period of 2 weeks (14% CP; 8.9 MJ/kg DM). Animals were housed individually and feed intake was recorded daily. The extensive groups were allowed to graze on natural pastures (80% red grass (Themeda triandra); 15% of species weeping love grass (Eragrostis species), finger grass (Digitaris eriantha) and drop seed grass (Sporabolus fimbriatus)) ad libitum (6.7% CP). In these groups, feed intake could not be recorded. Water was freely available to all animals. Milk production was recorded twice weekly from the first week following parturition for a 12-week observation period. Prior to the first hand-milking session, the kids were separated from the dams for a 2 h period and then allowed to suckle the dams for a 45 min period, after which they were separated from the dams. After separation, the first milking to drain the udder commenced. Each doe was injected with 1 ml oxytocin (Fentocin, Phenix) i.m., 5 min prior to milking, thereafter hand milking was performed to drain the udder and removal of as much as possible of the residual milk (Zamiri et al., 2001). This volume of milk was ignored and discarded. This procedure was repeated after 2 h and this time milk output was recorded and sampled. Milk production of this 2 h period was extrapolated to 24 h, to give the total daily milk production. Milk samples (50 ml) from each milking were kept (4 C) and analyzed for milk fat (F), protein (P), lactose (L) and solid non-fat (SNF) content by a Milko-scan 103:FPL apparatus on the same day. Daily feed intake was recorded only for the does fed intensively. All does in the intensively fed group were individually fed a 2 kg pelleted diet for the entire observation period, regardless of feed intake, milk production and breed. All does and kids were weighed weekly throughout the observation period to monitor body weight changes during this observation period (up to weaning).

3 J.P.C. Greyling et al. / Small Ruminant Research 55 (2004) The mean daily milk production, daily feed intake, body weight changes as well as the milk composition were analyzed using a one-way ANOVA in a 2 2 factorial design. Data analysis was carried out using the General Linear Models Procedures (SAS, 1991). Effects were considered significant at the 0.05 level or less. 3. Results 3.1. Milk production Maximal (mean 3.7 ± 1.4 l per day at week 4) and mean milk yield (3.1 ± 1.5 l per day) in the intensive Boer does was higher (P <0.05) than the respective peak (1.9 ± 7.0 l per day at week 5) and mean (1.4 ± 1.4 l per day) milk yield in the intensive Indigenous does (Fig. 1). On the other hand, maximal yield (1.1 ± 0.7 l per day at week 8) and mean milk yield (0.8 ± 0.7 l per day) in the extensively maintained Boer goats did not differ significantly than the respective peak (0.8 ± 2.0 l per day at week 9) and mean (0.7 ± 0.6 l per day) milk yield over the observation period in the Indigenous extensive group (Fig. 1). In both breeds the peak and mean milk production of the intensively maintained does was higher (P <0.05) than in the extensively maintained animals Milk composition The intensively managed Boer and Indigenous goats recorded a maximum fat concentration (8.8 ± 2.6 and 8.9 ± 3.7%) in weeks 1 and 8 of lactation, respectively, compared to the maximum fat yield (8.2 ± 1.9 and 7.5±4.5%) in weeks 1 and 5 for Boer and Indigenous goats, respectively, under extensive conditions. The intensively managed Indigenous goats produced the highest mean milk fat content (7.5 ± 3.2%) for the entire observation period (Table 2). An overall correlation of r = was recorded between milk yield and milk fat. The mean milk lactose content (%) over the 12-week lactation period is graphically illustrated in Fig. 2. Boer does managed intensively, recorded the highest mean daily milk lactose content (5.0 ± 0.7%), compared to the other treatment groups. The level of nutrition was found to have a significant (P <0.05) effect on the milk lactose concentration, with the intensively managed Boer goats recording a higher lactose content. There was a trend of the Boer goat producing a higher lactose content throughout the trial. An overall correlation of r = was recorded between the lactose content and the daily milk production Milk Yield (l/day) BI BE II IE Lactation period (weeks) BI = Boer intensive BE = Boer extensive II = Indigenous intensive IE = Indigenous extensive Fig. 1. Mean milk production (l per day) for Boer and Indigenous goat does in intensive and extensive feeding regimes, for a 12-week period post-partum.

4 100 J.P.C. Greyling et al. / Small Ruminant Research 55 (2004) Table 1 Mean (±S.D.) milk production and composition for Boer and Indigenous does managed under different nutritional regimes Intensive management Extensive management Boer goat Indigenous goat Boer goats Indigenous goats Milk production (l) 3.1 ± 1.5 a 1.4 ± 1.4 b 0.8 ± 0.7 c 0.7 ± 0.6 c Milk fat (%) 6.1 ± 2.2 a 7.5 ± 3.2 a 6.4 ± 2.1 a 6.0 ± 2.1 a Milk protein (%) 5.0 ± 1.0 a 5.0 ± 2.0 a 5.0 ± 3.0 a 4.5 ± 2.8 ac Milk lactose (%) 5.0 ± 0.7 a 4.3 ± 1.0 b 4.5 ± 0.6 b 4.5 ± 0.4 b SNF (%) 10.4 ± 6.5 a 9.9 ± 1.5 b 10.7 ± 5.1 a 9.6 ± 1.9 b Rows with different letters differ significantly (P <0.05). The mean milk protein content (%) for the Boer and Indigenous goat does is presented in Table 3. The Boer goat (extensive group) produced the highest mean daily milk protein content (5.0 ± 3.0%), compared to the other groups (Table 1). Level of nutrition had a significant (P <0.05) effect on the milk protein content in the Indigenous does, with the intensive group having a higher milk protein content than the extensive group. The extensively managed Boer goat does generally yielded milk with a similar milk protein content similar to that of the intensive group. A correlation coefficient of r = was recorded between milk protein content and daily milk production. The solid non-fat content showed that breed played a significant (P <0.01) role, with the Boer goat (extensive group) having the highest overall SNF content for the observation period (10.7 ± 5.1%) (Table 1) Feed intake The maximum and minimum feed intake (1.6 ± 0.6 and 0.5±0.5 kg per day) for Boer goats were recorded during weeks 7 and 9 following parturition, respectively and the corresponding intakes (1.0 ± 0.5 and 0.6 ± 0.4 kg per day) for the Indigenous goats during weeks 1 and 8, respectively (Fig. 3). A relatively large variation in feed intake was recorded throughout the observation period. The Boer goats had a significant (P <0.05) greater feed intake than the smaller framed Indigenous does. A correlation coefficient of r = 0.7 (P <0.05) and r = 0.4 was recorded between feed 6 5 Milk lactose (%) BI BE II IE Lactation period (weeks) BI = Boer intensive BE = Boer extensive II = Indigenous intensive IE = Indigenous extensive Fig. 2. Mean milk lactose content (%) for Boer and Indigenous goat does in intensive and extensive feeding systems.

5 J.P.C. Greyling et al. / Small Ruminant Research 55 (2004) Table 2 The mean (±S.D.) milk fat content (%) for Boer and Indigenous goat milk under different nutritional management systems Week Boer goats Indigenous goats Intensive feeding Extensive feeding Intensive feeding Extensive feeding Mean S.D. Mean S.D. Mean S.D. Mean S.D No significant differences between groups. intake and milk production for Boer and Indigenous goats, respectively Live weight Boer goat does (45.0 ± 8.7 kg) were significantly (P <0.05) heavier than the Indigenous does (32.3 ± 6.1 kg) in the intensive group, while the same tendency was observed for goats managed extensively (42.3 ± 8.0 and 29.3±4.5 kg, respectively). After week 3 of the lactation period, the Boer and Indigenous (extensive groups) does showed a slight (6.9%) decrease in body weight, while the goats in the intensive groups showed a slight increase (3.1%). The birth weights of the kids (only singletons) did not differ significantly between breeds and the nutritional regimes. For the intensive and extensive groups, the average daily gain (ADG) for the observation period was g versus 90.4 g and 75.8 g versus 56.4 g for Boer and Indigenous goat kids, respectively. The mean live weight gain was 13.3 and Table 3 The mean (±S.D.) milk protein content (%) for Boer and Indigenous goat does under different feeding regimes Week Boer goats Indigenous goats Intensive feeding Extensive feeding Intensive feeding a Extensive feeding a Mean S.D. Mean S.D. Mean S.D. Mean S.D a Values in these columns differ significantly (P <0.05).

6 102 J.P.C. Greyling et al. / Small Ruminant Research 55 (2004) Feed intake (kg/day) BI II Lactation period (weeks) BI = Boer intensive II = Indigenous intensive Fig. 3. Mean feed intake (kg per day) for Boer and Indigenous goat does in an intensive feeding regime for the first 12 weeks post-partum. 6.4 kg for the intensive and extensive Boer goat kids, while 7.6 and 4.7 kg for the intensive and extensive Indigenous kids, respectively. 4. Discussion 4.1. Milk production The high milk yields recorded in this trial demonstrate the potential of these goats, given an improved environment, to allow the maximum expression of the genes for milk production. According to Devendra and Burns (1970), milk production is largely affected by a combination of factors, namely, the use of improved breeds selected for milk production, a favorable nutritional environment and improved managerial practices. Results show the significant (P <0.01) beneficial effect that quality nutrition has on milk production and Boer goats demonstrated a higher mean daily milk yield (3.1 ± 1.5 l per day) in an improved nutritional regime, compared to 0.8 ± 0.7 l per day on natural pastures while intensively managed Indigenous feral goats had less potential in producing milk (1.4 ± 1.4 l per day). This is in agreement with other researchers, who found milk production of goats in the tropics to be generally low. Jamnapari, Beetal and Barbari breeds produce on average 0.75; 1.0 and 0.6 l per day per animal, respectively (Akinsoyinu et al., 1977). The Boer goat being a superior genotype for milk production is a possible alternative in the rural areas of South Africa to improve milk production of the Indigenous goat. This could possibly be done by cross-breeding of the Indigenous with the Boer goat. The quality of the diet to a large extent affects the lactation curve. The intensively managed Boer and Indigenous goat does reached peak lactation (3.6 ± 1.4 and 1.9 ± 7.0 l per day, respectively) earlier (week 5 of lactation), compared to their extensive counterparts (1.1 ± 0.7 and 0.8 ± 2.0 l per day, respectively) during weeks 8 and 9 of lactation similar to the findings reported by Zygoyiannis and Katsaounis (1986). The higher milk production in the intensive maintained Boer goat does can be attributed to genotype and nutritional environment (Morand-Fehr and Sauvant, 1980; Gall, 1981). Milk composition depends largely on the volume of milk produced (Zygoyiannis, 1988). The constituents of milk, namely fat, protein, lactose and SNF content, determine the value of the milk. The composition of milk is a function of several factors, e.g. breed, stage of lactation, climatic conditions, diet and season (Merin et al., 1988). According to Shamay et al. (2000) stressful environmental situations do not really change

7 J.P.C. Greyling et al. / Small Ruminant Research 55 (2004) milk yield and composition in goats and reflects their adaptation to harsh environments. In this study, the intensively managed Indigenous feral goats produced the highest mean fat content (7.5 ± 3.2%), compared to their intensive Boer goat counterparts with a mean of 6.1 ± 2.2%. This observation is in agreement with the finding that higher levels of milk production are associated with a lower fat content of milk (Flamant and Morand-Fehr, 1982; Zygoyiannis and Katsaounis, 1986). The fat content recorded in this study for the intensively managed Indigenous goats (7.5 ±3.2%) was lower than the 12% quoted by Zygoyiannis (1987), but higher than the 4.8 and 3.4% reported by Ehoche and Buvanendran (1983) and Muggli (1981). The decrease in goat milk fat content is attributed to a decrease in the molar proportion of acetic acid and an increase in the molar proportion of propionic acid in the rumen (Morand-Fehr and Sauvant, 1980). Generally an increase in milk production is associated with a decrease in milk constituents. However it is possible that frequent milking could stimulate synthesis of milk fat within the mammary gland and increase the total milk fat content. It is suggested that an increase in the milking frequency could be used to improve the efficiency of milk production (Negrão et al., 2001). The major carbohydrate in goat milk is lactose (Chandan et al., 1992). The highest mean milk lactose content (5.0 ± 0.7%) was produced by Boer goat does managed intensively. Lactose content values obtained are in line with other researchers (Simos et al., 1991; Chandan et al., 1992). The tendency of milk lactose content to decline with a decrease in milk production, as the lactation period progresses, is confirmed by Singh and Sengar (1990). The mean concentration of protein in goat milk is quoted as 4.5% (Zerfas et al., 1992), which is in agreement with that recorded mean (4.2 ± 1.0; 5.0 ± 3.0; 5.0±2.0 and 4.5±2.8% for Boer and Indigenous goats in the intensive and extensive environments, respectively). The mean protein content varied in this study between 3.8 ± 0.7 and 6.4 ± 2.4% in the intensively managed goats, compared to between 3.7 ± 0.5 and 7.2 ± 4.9% in the extensively maintained goats. Milk protein content, together with other milk constituents (except lactose), increases as the lactation period progresses (Singh and Sengar, 1990), although this was not evident in this study. The differences recorded (P <0.05) in protein content were not significant between the different breeds and only significant between nutritional regimes in the Indigenous (Table 3), with peak and minimum mean milk protein content being recorded at different stages of lactation. It may be concluded that in goats, energy balance is the most important factor in the determination of the milk fat and protein content. Milk production and composition are more dependent on the energy balance of the animal than on the composition of the diet (Bauman and Currie, 1980; Giger et al., 1987). Although milk protein content was consistently higher in the extensive Boer group from week 7 of lactation, the variation was also much greater in this group. The reason for this phenomenon is unclear. It would seem that there might be other factors barring breed and quality of the diet that have an effect. According to Zygoyiannis (1988) milk composition is also largely determined by the volume of milk produced. Simos et al. (1991), working with native Greek goats, recorded a mean SNF content of 14.1%, which is higher than the values recorded in this study (mean highest SNF content of 10.7 ± 5.1%). Simos et al. (1996) reported that SNF content, together with fat and protein content, to be negatively correlated to milk yield. Differences in the milk composition of goats have been attributed to factors such as age, breed, season, stage of lactation and plane of nutrition (Singh and Sengar, 1990). Feed intake is one of the main causes of a variation in milk production and the correlation between energy intake and milk production mid-way through the lactation is said to be as high as r = 0.83 (Hadjipanayiotou, 1995). The correlation between feed intake and milk production in the high producing goats (Boer goats in the intensive group) in the present study was r = 0.7 (P <0.01). So for example, Boer goats recorded the highest mean feed intake and milk production in this study (1.6 ± 0.6 and 3.1 ± 1.5 l per day, respectively). It is to be remembered that the higher feed intake of the Boer goats could also be attributed to their bigger frame-size and consequently higher maintenance requirements (mean live weight of 45.0 ± 8.7 kg versus 32.3±6.1 kg, respectively), when compared to the Indigenous goats. In the intensive and extensive groups, live weight decreased during early lactation (weeks 1 and 2), followed by the relative maintenance of body weight. The Indigenous does in the extensive group showed

8 104 J.P.C. Greyling et al. / Small Ruminant Research 55 (2004) a tendency to lose weight during the observation period. Weight loss in adult does at the onset of lactation is normally related to milk production during the first week of lactation only. This loss in body weight could generally attributed to the mobilization of body fat, which is stored during the dry period (Gall, 1981). In this study the animals in the extensive groups showed a greater decrease in live weight (due to being subjected to a poorer nutritional environment). A high quality diet is beneficial to the kid growth (via milk production) and milk yield has been shown to be affected by the number of lambs suckled and not by the number of lambs born (Zygoyiannis, 1987). In conclusion therefore it can be stated that the Boer goat has a higher genetic potential for milk production, compared to the Indigenous goat and the quality of the milk produced by both breeds is of similar quality to that of the dairy goat. Animals under the better nutritional regimes had a higher milk yield, although milk composition was not necessarily affected. Thus Boer goat does (and to a lesser extent the Indigenous does), given the abundance and adaptability of the breed, can fulfill the function of providing milk to the rural communities and be used to alleviate the problem of malnutrition and even serve as a possible source of income to the owners. It is thus recommended that Boer goats be kept for milk production (while also being a source of meat) in the poorer communities, who cannot afford to purchase dairy goats or dairy cows. It is also beneficial for these communities to nutritionally supplement their animals. Further studies are also suggested to evaluate the suitability of the processing of this milk into products (e.g. yoghurts, cheese, butter, etc.) for local consumption. 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