Effect of minimal supplemental feeding with lucerne during late gestation on pre-weaning performance of goats grazing Themeda triandra and Tarconanthus camphoratus

M L Mashiloane and O M Ntwaeagae

Vaalharts Agricultural Research Station, Department of Agriculture, Land Reform and Rural Development, Northern Cape, Private Bag X9, Jan Kempdorp 8550. South Africa
mashiloane01@yahoo.co.uk

Abstract

The objectives of this study were to determine if minimal supplemental feeding with lucerne during late gestation has effect on weight gain of does and birth weight, weaning weight and pre-weaning growth rate of their kids. Thirty-six late-pregnant does were allocated in a Randomised Complete Block Design (RCBD) to three levels of lucerne treatment in a minimal supplemental strategy. The strategy requires that animals be fed at least half their daily dry matter requirement with a high nutrient feedstuff to supplement natural grazing. Effects of minimal supplementation with lucerne were analyzed using Mixed procedures of SAS. There were no significant differences in doe weight gain between all treatments, and the same applied for kid performance traits. Minimal supplemental feeding with lucerne did not affect weight gain of does and pre-weaning performance kids.

Key words: Gestation, kid performance, nutritional constraints

Introduction

One of the major constraints to livestock production in semi-arid areas is poor nutrition caused by feed shortages particularly in the dry season (Ndlovu and Sibanda 1993; Mlambo et al 2004). With an annual average rainfall of less than 600 mm and an average grazing capacity of more than 10 hectares per livestock unit, the Northern Cape (NC) Province cannot be an exception to the abovementioned constraint. Productivity in goats is measured as increased conception rates, kid survival and increased growth rates. All these parameters of productivity have hardly been met by the existing goat herds at the Koopmansfontein Research Station of the NC and this could be indicative of the conditions in the Province or at least parts thereof. The inefficiency of production is evidently more apparent in the spring mating season. This breeding season coincides with a period of good veld condition as it is the onset of rainfall season and the period of regrowth for most grass species and shrubs. The spring breeding season can therefore be successfully applied by veld (rangeland) goat producers. However, Goromela et al (1997) reported that natural pastures are characterized by fast growth and early maturity followed by rapid decline in nutritive value. The decline in nutritive value is more severe in sour veld than in sweet veld. Changes in nutritional value of feed resources result in irregular growth patterns and low milk yields in goats (Das and Sendalo 1991). The decline in quality of the natural pastures coincides with late stage of gestation of the spring mated does. Given the decline in feeding quality it is worth mentioning that eighty percent of foetal growth occurs during the last two months of pregnancy and this leads to a significant increase in the does’ net nutrients requirements (Ocak et al 2005). Several studies have revealed that quality and quantity of nutrients (notably protein and energy) in late pregnancy are critical for good kid’s growth and survival (Litherland et al 2000; Ocak et al 2005; Robinson et al 1999), hence supplemental feeding of veld grazing does in late gestation with a high quality protein feed is necessary if viable productivity is to be maintained. However, most farmers cannot afford expensive commercial supplements; therefore alternatives are required (Mlambo et al 2004). Leguminous fodder plants, such as lucerne, have a high crude protein content (>15%) particularly in the leaves, and are rich in vitamins and minerals and hence are putatively useful as a supplement to low quality roughages (Nsahlai et al 1996). Therefore the aim of this study was to investigate the possibility of enhancing pre-weaning performance in kids of Themeda triandra and Tarconanthus camphoratus veld grazing does through the use of lucerne in a minimal supplemental strategy during late gestation. The hypotheses that were tested in this study were if minimal supplemental feeding with lucerne during late gestation has effect on weight gain of does and birth weight, weaning weight and pre-weaning growth rate of their kids.

Materials and methods 

The site of the study was at Koopmansfontein Research Station of the Northern Cape Department of Agriculture and Land Reform. The station is situated 50 km east of Danielskuil. The area experiences summer rainfall with an annual average of 419.5 mm and has veld with a carrying capacity of 10 ha/LSU. The natural veld pasture at the Koopmansfontein Research Station consists mainly of Themeda triandra grass and Tarconanthus camphoratus shrub, and is the only feed source for goats on the farm. Performance of does and kids on this veld is remarkedly low.

The South African Boer Goat breed was used in the current study. The breed is well known for its characteristic hardiness, high productivity and efficient use of low quality rangeland pastures (Casey and Van Niekerk 1988). Animals used in this study were does aged between three and five years. A sample of 36 pregnant does from the herd mated in the spring season was randomly selected from the herd on the station. Management in terms of nutrition and health of the sample herd was similar to that of other goats on the farm up until the does were allocated to different treatment groups. Non control groups were allowed a two weeks adaptation period to the supplementary feeding regime prior to collection of experimental data. 

A formulated strategy for minimal supplementation entails feeding the animals with a supplemental feed only as a limited portion of their daily intake in addition to the feed obtained from the natural pastures. This strategy requires that the weight of the animals be known so that animals will only be allocated half of their estimated daily dry matter intake (1.5% of body weight). In this way animals are expected to get the benefits of a high protein supplement while farmers will be able to reduce production costs by cutting on costs of supplementary feed.

The treatments consisted of three levels of lucerne hay, allocated each to 12 does in late pregnancy (average six weeks before parturition) subsequent to a South African spring mating season. Trough feeding was done near water points in camps. Treatment levels were: Control = Animals in late gestation grazed on natural veld, S2 = Animals in late gestation minimally supplemented with lucerne hay equivalent to 1.5 % of group average body weight once in two days and S1 = Animals in late gestation minimally supplemented with lucerne hay equivalent to 1.5 % of group average body weight once daily. The crude protein (CP) and metabolizable energy (ME) content of lucerne hay used for supplementation was 19.20 % and 7.50 MJ/kg with average moisture content 10.37 %. The experimental design was a Randomized Complete Block Design (RCBD) with three levels (groups) of treatment and two blocks of farm site (to cater for terrain differences). Kids born in all treatment groups were allowed 24 hours suckling access during and after the experiment and the supplementation ceased at the end of six weeks after which treatment groups were recombined to rear their kids to weaning in a uniform environment.    

The weight of does at the start of the trial, weekly weights of does before parturition, birth weights and kid weaning weights (three months/early weaning) were recorded during the experimental period. A standard formula (adg = (final mass - initial mass)/ days) for estimation of growth rate was applied to the data to derive the estimate.

Variation in observations was modelled as:

y₁ = t_i + s_j + b_j + w_k + a_{k  +}  e_ijk   and  

 y₂ = t_i + w_k + a_k  + p_{l +}  e_ilk.

Where:

y₁ is the observation of kid performance,
t_i is treatment class variable for the i^th group ,
s_j is the sex class of the j^th individual kid,
b_j is the birth status (single/twin birth) of the j^th kid,
w_k is the covariate starting mass effect of the k^th doe,
a_k is the covariate effect of age of dam for the k^th doe and
e_ijk is the residual error associated with all effects.  

In the second model,

y₂ is the observation of doe weight gain,
t_i is treatment class variable for the i^th group,
w_k is the covariate starting mass effect of the k^th doe,
a_k is the covariate effect of age of dam for the k^th doe,
p_l is the pregnancy (twin / single pregnancy) class effect of the l^th pregnancy class and
e_ilk is the residual error associated with all effects.

Effects of sex, birth status, pregnancy type and covariates of doe age and starting weight were included to enhance the fit of the models. Preliminary analysis indicated no difference in main plot effect of farm site and hence was excluded in the variance analysis. Mixed procedures of SAS (2003) were used to analyze for variation and least square means of treatment classes were compared by Duncan’s Multiple Range Test at 0.95 probability.

Results and discussion 

Mean values for changes in live weight of the does and kids are presented in Table 1. Change in weight of does in treatment was 1.53 kg, 1.49, and 1.50 for control, S2 and S1 respectively and they did not differ (P > 0.05). The average birth weight of 3.94 kg for the control was tantamount to the higher limit of the range for birth weight of between 3 kg and 4 kg for the breed population data as indicated by Lu (2003). Observations of birth weight in treatment classes were also within this range and they also did not differ with each other or the control group. The average weaning weight (100 d) was higher for the control group although not different ( P > 0.05) to the two treatments. This could be expected as the average initial and final weights were higher in the control group than treatment groups. Heavier does are known to wean heavier kid than their counterparts. Pre-weaning growth rates also did not differ by treatment. In comparison to estimates by Lu and Potchioba (1988), the pre-weaning growth rates in the experimental herd were considerably low At 95.6 g/day, 73.6 g/day and 76.4 g/day for the control, S2 and S1 respectively.  Lu and Potchoiba (1988) estimated that at weaning (100 days), kids can weigh in the range of 20 to 25 kg with a pre-weaning growth rate of 291 g/day (for period between birth and 100 days). 

The non difference in doe and kid traits could possibly be explained by the low level of adaptation to the supplementation diet. It is expected that animals will adapt to an introduced diet but it is arguable whether the process of adaptation will take as long/short in grazing animals as it would in penned animals. Another possible scenario is that extra protein supplied by the supplement in the applied strategy was not enough to elicit differences in performance in the period of experimentation. Goats adapt their browsing patterns to the environment in order to ensure maximum available nutrient intake. Animals are thought to have current output goals (such as maintenance, growth, level of fatness and gestation) which they seek to achieve through their feeding behaviour (Kyrizakis 1997) and hence they are expected to choose the diet that allows them to meet their goals (James et al 2001).  Despite a well established increased requirement for nutrients in the last quarter of pregnancy, a study by Carson et al (2004) indicated that high birth weights and similar lamb outputs at weaning was possible for ewes lambing on natural pastures as compared to those in intensive systems. Carson et al (2004) furthermore indicated that the performance of lambs from ewes on grass can be satisfactory. Findings of the current study are in contradiction with conclusions made about providing supplemental protein which is said to stimulate voluntary intake and improve livestock performance (Kartchner 1980; Del Curto et al 1990 and Horney et al 1996). These findings also differ with those in studies of James et al (2001); Ocak et al (2005); Robinson et al (1999) and Goromela et al (1997) in which positive results in alignment with supplemental feeding with high nutrient forage during pregnancy were reported.

Conclusions 

• The use of lucerne in a minimal supplemental strategy did not affect weight gain of does during late pregnancy which is considered very high.

  
  

• Treatment also did not have effect on observed performance of kids as measured by birth weight, weaning weight and pre-weaning growth rate.

  
  

• It was concluded that supplementing with lucerne in a minimal supplemental strategy during late gestation was not effective in enhancing pre-weaning performance in kids of Themeda triandra and Tarconathus camphoratus veld grazing does.

References 

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Received 15 September 2009; Accepted 13 October 2009; Published 1 November 2009

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