Evaluation of local feed resources, their response on intake, growth, milk yield and composition and product properties of Namibian indigenous goats
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Date
NOVEMBER, 2016
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Abstract
The study evaluated alternative local feed resources as potential protein supplements for dairy goats.
Four linked-experiments were carried out in this research. The first experiment, a survey was
conducted to investigate farmer’s indigenous knowledge on woody plants available in Omatako,
Guinas, Tsandi, Daurês, Gibeon and Kongola constituencies of Namibia. Structured questionnaire
was randomly administered through face to face interviews with farmers. Sixty (60) households were
selected using purposive sampling strategy and GPS-point reading to evenly-space the points in the
villages. Information on gender, age, level of education of farmers, type of livestock species reared
and predominant woody plant species in the constituencies and their multiple uses were captured.
The results from the survey revealed that farmers had profound knowledge on native woody plant
species in their constituencies. Most households interviewed were male-headed (73 %), aged
between 41- 60 years (43 %) and had at least primary (53.3 %), secondary (35.0 %), and very few
with no education (3.3 %) background. The highest number of cattle (39 %) and goats (31 %) were
recorded in Guinas, sheep (77.7 %) in Gibeon and chicken (34.1 %) in Kongola. A. erioloba and C.
apiculatum were predominantly listed across all the constituencies, and A. hereroensis, C. collinum
and R. trichotomum were the least common species listed as they were confined to certain
constituencies. About 47 % of famers indicated to harvests pods and leaves for animal feeding,
whereas 53.3 % do not harvest. C. mopane, Z, mucronata, G. bicolor, A. erioloba and T. sericea
were used in the treatment diarrhoea in cattle and goats, whereas, B. albitrunca was used to improve
fertility in breeding bulls.
The second experiment (Feed evaluation) determines the chemical composition and in-vitro gas
production of 17 woody plant species collected during the survey from 6 constituencies. Woody
plant pods (3) and leaves (16) were randomly collected by hand during wet {January}, early dry
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{May} and late dry {September} season. Chemical analysis of each sample was performed in
duplicates and in vitro gas fermentation was replicated in 5 runs of 48 hours with 77 units in each
run. Gas production readings were recorded at 3, 6, 9, 12, 24, 36 and 48 hours of incubation. Mean
values for NDF were highest noted in P. nelsii leaves (499.9 g/kg DM) and lowest in Z. mucronata
leaves (317.9 g/kg DM). ST concentrations were detected highest(15.5 g/100g DM) in D. cinerea
pods and lowest in A. karoo leaves (1.9 g/100g DM).DM, OM, NDF and ST were significantly
higher in dry season than in wet season (P>0.005) whereas, CP, Ash and ADF were not affected by
season and location of study (P>0.05). Ca, P and Se concentrations were high in wet season than in
dry season. P concentration differed by location with Kongola (3.6 g/kg) having highest value than
others. There was a significant positive correlation between NDF and ADF (r=0.62), ST and ADF
(r=0.46) but all these were negatively correlated to gas production parameters (P<0.05). CP had a
weak relationship with cell-wall constituents and gas production parameters.
Among the 17 woody plant species, AE and DC pods were selected for further animal feeding based
on chemical composition and in vitro gas production. An on-station feeding trial was conducted to
determine the effect of AE and DC pod supplementation on intake, doe weight changes, growth of
kids and estimate milk yield consumed by the kids on metabolic body weight basis. Forty eight (48)
indigenous lactating does with average weight of 35 kg from parity 2 and 3 were allocated in a 2x3
factorial arrangement of treatments as a CRD with 6 does per treatment. The main factors were 2 pod
types {AE; DC} at 3 different feeding levels {20; 40; 60 %}, benchmarked against positive
{Commercial feed} and negative control {non-supplemented} resulting in 8 treatment diets.
Phosphate-salt lick and water were available at ad libutum. The result showed that daily intake of
does on Comm (430.9 gDM/day) were higher and lowest in AE (289.3 gDM/day) however, does on
DC had the highest gain (38.9g) and lowest on Nosupp group (28.1 g), whereas does on AE had
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slightly higher final weight (35.6 kg). Kids from does on Comm had the highest ADG (114.4g) and
lowest in AE (98.6g). When AE and DC were compared without the treatment controls, does on
DC40 had highest intake (316.6 g DM/day), ADG (106.9 g) of kids and better weaning weights (15.6
kg). On average, milk consumption of kids per metabolic body weight was between 1.34 and 2.75 kg
DM/M
0.75
/day. Does supplemented with AE60 and DC60 indicated reduced intake, growth and lower
milk consumption of kids.
In the last experiment, milk obtained from the animal feeding trial was collected every second week
to determine the effect of AE and DC pod supplementation on milk composition. Milk composition
data was analysed in a 2x3 factorial arrangements of treatments as a CRD. In the 10
th
week of the
feeding trial, 16 litres (2 litres per treatment) of milk was collected for the processing of fresh milk,
fermented-sour milk and yoghurt for sensory evaluation. Sensory evaluation was assessed in a 3x8
factorial arrangements of treatments resulting in 24 products samples offered for testing by 20
panelists. Sensory evaluation using trained team was done to confirm the descriptive characteristics
of the products mainly; the color, aroma, flavour, texture, consistency and overall productivity. A 5-point Hedonic scale ranging from 1 to 5 was used to rate the products, where; 1= like very much, 3=
neither like nor dislike and 5= dislike very much. The results indicated that AE and DC pod
supplementation had no effect on total solids, fat, protein, solid-non-fat and ash; however, Ca and P
concentrations in milk increased with DC rate and declined with AE rate. Fermented-sour milk and
yoghurt were significantly rated highest for colour, aroma and overall palatability (P<0.05), whereas
fresh milk mean scores were not significantly different (P>0.05).Panellist did not detect any
unpleasant odours or off-flavours in the dairy products. The study concluded that supplementation
with AE and DC pods improved performance (intake, growth, milk yield) in goats. Supplementing
with 40 % DC was recorded to be superior in improving milk in lactating does and growth of kids.
Description
A thesis submitted to the Department of Animal Science, Faculty of Agriculture, College of Agriculture and Natural Resources Kwame Nkrumah University of Science and Technology, in fulfilment of the requirements for the degree of Doctor of Philosophy (Animal Nutrition),