Effect of soybean meal supplementation on pre-and post-partum productivity of Angora goats in communal rangelands of Molimo-Nthuse in Lesotho

J W Ng’ambi, L Khitsane*, D Norris and C A Mbajiorgu

Department of Animal Production, University of Limpopo, P/B X1106, Sovenga 0727, South Africa
*Lesotho College of Education, Maseru, Lesotho
anayochukwumbajiorgu@gmail.com

Abstract

Twenty four Angora goat does were used in a study aimed at determining the effect of pre- and post-partum soybean meal supplementation on productivity of the doe and on kid birth weight, growth rate and mortality in the communal rangelands of Molimo-Nthuse area of Lesotho. A randomised block design with three treatments and eight replicates was used to test treatment effects from one month before kidding up to two months after kidding. The three treatments were grazing natural pastures only (S1), daily 50-g soybean meal supplementation per doe plus grazing natural pastures (S2), and daily 100-g soybean meal supplementation per doe plus grazing natural pastures (S3).  

Kid birth weights of 2.15, 2.32, and 2.89 kg for S1, S2 and S3, respectively, were obtained. Kid birth weights from does on S3 were higher (P<0.05) than those from does on S2 and S1. Total milk yields over the first two months of lactation were 17.92, 23.17, and 29.65 kg per doe for animals on S1, S2, and S3, respectively. Does on S3 produced more milk (P<0.05) than those on S1 and S2. Does on S3 produced milk higher (P<0.05) in lactose than milk from does on S1 and S2. Kids from does on S1, S2, and S3 grew at 75.96, 83.33, and 98.23 g per day, respectively. Supplementation increased (p<.0.05) kid growth rates. Kid growth rate was positively correlated (r = 0.69; P<0.05) with birth weight. However, kid growth rate was poorly correlated (r = 0.0485; P>0.05) with milk yield. A daily 100 g soybean meal supplementation of does reduced kid mortality from 37.5 % (S1 and S2) to 12.5 %.  

This study demonstrated that minimal full fat soybean meal supplementation can offset the detrimental effects of both maternal and offspring undernutrition during the critical stages of the reproductive cycle of Angora goats in communal rangelands. 

Keywords: birth weight, growth rate, mortality, milk composition, milk yield

Introduction

Angora goats play an important role in the economy of Lesotho. They provide a source of income through the sales of their mohair, meat or the animals themselves. In 2000 the value of mohair sales alone was above R14 million (Bureau of Statistics 2001). However, most studies indicate that over the past 30 years Angora goat population, mohair production and mohair yield per goat have been declining at annual rates of 0.5, 1.2 and 0.01 %, respectively (Hunter 1987; Ng’ambi and Belete 1999). These studies indicated poor nutrition as being the most important cause of high kid mortality and low productivity of Angora goats in Lesotho. 

In Lesotho, Angora goats depend, mainly, on natural pastures in communal rangelands to meet their nutrient requirements. These natural pastures are very limiting in a number of nutrients, the most limiting one being protein. This is more severe during winter months when there are low temperatures which do not sustain plant growth (Hunter 1987; Phororo 1979). Unfortunately, this is the time when Angora goat does in Lesotho are pregnant. As a result, nutrients provided to the growing foetus are limiting. Poor pre-partum nutrition results in does giving birth to lighter kids (Bajhau and Kennedy 1990). Birth weight of an Angora goat kid is positively related to its growth, survival, adult weight and subsequent performance (Bajhau and Kennedy 1990; Shelton and Basset 1970). Poor post-partum nutrition of Angora goat does will result in less milk produced for their kids which, apparently, depend entirely on this milk during the first two months after birth. Undernutrition during this time may lead to kids developing nutritional diseases or it may expose them to infection and hence death. Over 50 % of Angora goat kids in Lesotho die within two months of their birth (Hunter 1987; Lawry 1986). 

The effects of pre- and post-partum protein supplementation on productivity of Angora goat does and their kids in the rangelands of Lesotho have not been studied. Such information and data would be useful in improving the productivity and sustainability of Angora goat population in the rangelands of Lesotho. The main objective of this study, therefore, was to determine the effect of minimal and strategic pre- and post-partum soybean meal supplementation on the productivity of the doe and on kid birth weight, growth and mortality in the communal rangelands of Molimo-Nthuse area of Lesotho.  
 

Methodology 

Study site 

This study was carried out between May 2000 and May 2001 in the Molimo-Nthuse area of Lesotho.  Molimo-Nthuse is between 29.5° south latitude and 27.9° east longitude. It is about 2275 metres above sea level. Annual precipitation ranges from 800 to 1000 mm with most of the rain falling in January and February.  Annual temperature ranges from –10 °C in winter to 32 °C in summer (Bureau of Statistics 1987). The communal rangelands have natural pastures. The natural pastures are dominated by such grass species as Themeda triandra, Aristida bipartita and Festuca caprina. Details of vegetation have been described by Mpiti-Shakhane (2000). The rangelands are ideal for livestock grazing.  However, the condition of the rangelands is estimated to be poor, particularly in winter. 

Goats, treatments, design and data collection 

Twenty four Angora goat does, in their second lactation (about two years old) were used in this study.  They were all shorn on 1^st May 2000 and mated to the same buck in May 2000 as this is the recommended breeding month for this area (Hunter 1987; Phororo 1979). The goats were herded on communal natural pastures throughout the experiment.  After grazing during the day, the animals were kept in a well ventilated shed during the night. During the entire experimental period animals were allowed access to clean water and salt.  At the beginning of the experiment all the animals were treated for internal parasites with Seponver Plus (Janssen Pharmaceutical Ltd. SA) at 2 ml per 5 kg live weight. In September 2000 when the Angora goat does were 4 months pregnant, they were allotted to the three treatments as specified in the next section. 

Angora goat does in their fourth month of pregnancy and with an initial mean live weight of 28 + 5 kg were grouped according to similarity in live weight. Within each group the animals were allocated at random to three treatments in a completely randomised block design (Steel and Torrie 1960).  Each treatment, therefore, had 8 replicates. The three treatments were as follows: Ad-libitum grazing of natural pastures and no supplementation (S1); Ad-libitum grazing of natural pastures and 50 g full fat soybean meal supplementation per goat per day (S2); Ad-libitum grazing of natural pastures and 100 g full fat soybean meal supplementation per goat per day (S3). The animals were on these treatments from one month before kidding up to two months after kidding.  Supplements were given every morning at 08:00 hours. Thereafter, animals were allowed to graze for a period of 8 hours per day. Full fat soybean meal was obtained from Lesotho Flour Mills in Maseru, Lesotho. Angora goat kids were weighed at birth and thereafter (up to two months old) weighed once per week using an electronic weighing scale. Milk intake and hence yield was estimated once per week (Thursday) for a period of two months after kidding.  A modification of a technique used by Owen (1957) and Banda (1999) was used to estimate milk intake. Following overnight separation, kids were weighed at 08:00 hours. For the next one hour kids were allowed to suckle their dams. Kids were then weighed and separated from their dams at 09:00 hours.  The difference in weight was taken as a measure of milk intake by the kids and hence milk yield.  At 16:00 hours kids were again weighed and allowed access to their dams for one hour and then re-weighed.  The combined estimate of milk intake during the two periods was taken to represent that day’s milk intake and hence milk yield.  Additionally, milk samples were drawn from each doe once per week (Tuesday) for two months after kidding. At the end of the experiment does were shorn on 1^st May 2001 at the Lekubane shearing shed.  Grease weight of mohair shorn from each doe was obtained.  For ease of reference this is referred to as mohair yield in the following sections. 

Nutrient analysis 

Samples of Soybean meal were analysed for dry matter, ash, organic matter, energy and crude protein, following the methods described by Association of Official Analytical Chemists (2004). All the milk samples were analysed for butterfat content, crude protein, lactose and total solids using Milkoscan 103: FPL at Dairybelle in Bloemfontein, South Africa. 

Data analysis 

Growth rates of kids were calculated by regressing live weight on time over a period of 8 weeks (SAS 2000). Analysis of variance according to a randomised block design was done with the SAS (2000) program. Least significant differences (LSD) were used to test between treatment means. Data from does that lost their kids were not included in the analysis and hence considered as missing values. Correlation analysis was used to estimate the relationships (r) between birth weight and growth rate, and between milk yield and growth rate.  The Chi Square test was used to separate differences in kid mortality rates between the treatments (SAS 2000). 
 

Results 

Results of the chemical analysis of the full fat soybean meal supplement on dry matter basis are CP 403 g / kg, Energy 13.2 ME MJ/ kg, Ash 54 g / kg and Organic matter 946 g / kg.  Results of milk yield and composition are given in Table 1. 

At Week Four of lactation, Angora goat does on 100 g of soybean meal supplementation (S3) produced significantly (P<0.05) more milk than those on no soybean meal supplementation (S1) and those on 50 g of soybean meal supplementation (S2). However, there were no significant (P>0.05) differences in milk production between does on S1 and S2 diets at Week 4 of lactation. Total milk production figures over the 8 weeks of lactation were 17.92, 23.17, and 29.65 kg/doe for treatments S1, S2, and S3, respectively. Total milk produced by does on S3 diet was significantly (P<0.05) more than milk produced by does on S1 diet. However, there were no significant (P>0.05) differences in total milk produced by does on S1 and S2 diets, and milk produced by does on S2 and S3 diets. At fourth week of lactation, Angora goat does on S3 diet produced milk with 63.1 g butterfat per kg, and this was significantly different from 52.3 g butterfat per kg milk produced by unsupplemented does. No significant (P>0.05) differences in butterfat content were observed between treatments S1 and S2, and between S3 and S2. There were no significant (P>0.05) differences between treatments in protein content of the milk. However, does on S3 produced milk which was significantly (P<0.05) higher in lactose than the milk produced by does on S1 and S2. Angora goat does on S3 produced milk with significantly (P<0.05) higher total solids (177.4 g/kg) than that produced by does on S1 (160.5 g/kg). However, no significant (P>0.05) differences in total solids were observed between milk produced by does on S1 and S2, and between S2 and S3. There were no significant (P>0.05) differences between treatments in annual mohair yields (P> 0.05). Results of the effect of pre- and post-partum soybean meal supplementation of Angora goat does on kid birth weight, growth rate and milk conversion ratio are presented in Table 2.

Angora goat does on 100 g of soybean meal supplementation gave birth to kids with significantly (P<0.05) higher birth weights than those from unsupplemented does and those from does supplemented with 50 g of soybean meal. However, there were no significant (P>0.05) differences in birth weights of kids from unsupplemented does and those from does supplemented with 50 g of soybean meal. Angora goat kids from does on S1, S2 and S3 diets grew at 74.75, 82.14, and 98.40 g per day, respectively, over the 8 weeks. The differences in growth rates were significant (P<0.05). Angora goat kids from does on S3 diet had a significantly (P<0.05) better milk conversion ratio (3.22) than kids from does on S1 (4.11) and S2 (3.72) diets. Kid growth rate was positively and significantly (P<0.05) correlated with birth weight (r = 0.694). However, kid growth rate was not significantly (P>0.05) correlated with milk yield during the first two months after birth (r = 0.0485).  Angora goat kids from does on S3 diet had a lower mortality rate of 14.3 % compared to 37.5 % from S1 and S2 diets (P<0.05). 
 

Discussion 

Angora goat production in Lesotho is based on communal pastures. The system is of low levels of inputs and farmers act to minimize costs (Phororo 1979; Lawry 1986).  Thus, the animals depend on natural pastures which are of low nutritive values, particularly during winter months (Mpiti-Shakhane 2000). These rangeland pastures are very deficient in protein and energy (Phororo1979; Goebel et al 1986).

This study has shown that full fat soybean meal supplementation in late pregnancy (last month) and early lactation (2 months after kidding) had marked effect on does and kids. Angora goat does supplemented with 100 g soybean meal daily gave birth to heavier kids, 2.90 kg as compared to 2.15 kg for the unsupplemented ones.

Elsewhere, various researchers have observed similar positive responses to protein feed supplementation in goats grazing native pasture species (Bajhau and Kennedy 1990; Epstein and Hertz 1964; Huston et al 1993). These authors concluded that positive responses observed when goats were grazing native grass species supplemented with protein feeds were due to the limiting metabolisable protein and energy in the grasses. Supplementation with limiting nutrients during foetal growth impacts on developmental changes that affect size of the kid at birth (Bajhau and Kennedy 1990). Lighter kid birth weights among unsupplemented does in the present study may have been an indication of inadequate pre-partum nutrition in the diet. The daily kid growth rates of 74, 82 and 98 g for treatments S1, S2 and S3, respectively, observed in this study are similar to those reported elsewhere for goats (Adogla-Bessa and Aganga 2000; Bajhau and Kennedy 1990; Sangare and Pandey 2000).   

In the present study, it has been shown that soybean meal supplementation in the late pregnancy and early lactation improved kid growth rates. A daily supplementation of 100 g soybean meal per doe in late pregnancy and early lactation increased kid growth rate by 31 percentage points. Other authors have observed similar results (Bajhau and Kennedy 1990; Sangare and Pandey 2000; Shelton 1965; Wahome 1986). These authors showed that where some nutrients were limiting in the diets of grazing does, nutritional supplementation in late pregnancy and early lactation increased growth rates of kids by 20 to 40 percentage points. They attributed the high kid growth rates to the high kid birth weights and high milk yields in supplemented goats. Bajhau and Kennedy (1990) and Shelton (1965) found that kid birth weight and milk yield were positively and significantly correlated with kid growth rate. Kid birth weight, milk yield and milk composition seem to have, also, played important roles in the determination of kid growth rates in the present study. Thus, kid birth weight was positively and significantly correlated with kid growth rate (r = 0.694).  Angora goat does supplemented with 100 g of soybean meal produced kids with higher birth weights. These kids grew faster than those from unsupplemented does and those from does supplemented with 50 g of soybean meal. The high growth rates in kids with high birth weights could be attributed to the fact that these kids were more mature at birth and their physiological systems were more developed to respond better to good nutrition (Bajhau and Kennedy 1990; Wahome 1986). The higher kid growth rates observed in soybean meal supplemented treatments could, also, be accounted for in terms of milk yield and composition. Angora goat does supplemented with 100 g of soybean meal produced more milk than unsupplemented does and those supplemented with 50g of soybean meal. Similarly, does supplemented with 100g of soybean meal produced milk which was higher in lactose content compared to the one in milk produced by does in the other two treatments.  Because the kids depended entirely on milk during the first two months after birth, those which consumed more milk were expected to attain higher growth rates (Bajhau and Kennedy 1990). It can be suggested that unsupplemented does were not getting sufficient nutrients for optimal milk production.  Consequently, the low growth rates in kids from unsupplemented does were indicative of poor nutrition available to the kids. Indeed, Goebel et al (1986) and Mpiti-Shakhane (2000) indicated that natural pastures in the rangelands of Lesotho are limiting in protein and energy contents during winter months.  

All Angora goat kid deaths in the present study occurred within the first two months after birth.  However, the majority of deaths, about 90 %, occurred within the first two weeks after birth. Unfortunately, this period coincided with snowing in the area. Kids from unsupplemented does had a mortality rate of 37.5%. This is high but similar to farm level kid mortality rates reported by Ng¢ambi and Matebesi (2001) in the same area. However, 37.5 % is lower than farm level kid mortality rates of above 50% reported by Hunter (1987) and Lawry (1986) in Lesotho. They attributed the high kid mortality rates to poor nutrition, and, also, to low ambient temperatures during kidding time in the communal rangelands of Lesotho. Soybean meal supplementation in late pregnancy and early lactation increased kid birth weights and milk yield but decreased kid mortality.  

Similar results have been observed in goats (Awemu et al 1999; Bajhau and Kennedy 1990; Rattner et al 1994) and sheep (Kelly 1992). They attributed the high rates of survival to high kid birth weights and milk yields. They also showed that kids with high birth weights had higher energy reserves and were, therefore, able to withstand harsh environmental conditions faced immediately after birth. Because of their comparatively small surface area they were, also, able to conserve more heat and hence were not prone to hypothermia. Bajhau and Kennedy (1990) showed that such kids were more mature at birth, their physiological systems were more developed and they were, therefore, more resistant to environmental stresses. On the basis of these studies it would appear that unsupplemented goats and those supplemented daily with 50 g soybean meal in the present study were not getting enough nutrients for foetal growth and milk production. Thus, kids from such treatments had higher mortality rates.  
 

Conclusions

• This study has demonstrated that minimal and strategic full fat soybean meal supplementation can offset the detrimental effects of both maternal and offspring undernutrition during the critical reproductive stages of Angora goats grazing natural pasture species in the communal rangelands of Molimo-Nthuse area in Lesotho.

• A daily supplementation of 100 g full fat soybean meal per doe during the last month of pregnancy and during the first two months of lactation can improve doe milk production and composition, kid birth weight and growth, and reduce kid mortality by 25 percentage points. 
   

Acknowledgement

The authors wish to thank Lesotho Mohair Trust for their financial support to carry out this study.
 

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Received 28 August 2007: Accepted 19 September 2007: Published 1 January 2008

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