END OF FEEDING TRIAL REPORT FOR THE ASESSEMENT OF THE FFECT OF
SWEETPOTATO VINES SILAGE ON LACTATING ANKOLE X FRESIAN CROSS
BRED DAIRY COWS
BY
1Nampijja Z.; 1Lutwama V.; 2Kyalo, G.; 2Mayanja S.; 3Grant F.; 4Kabirizi J.; 5Namagembe A.; 6Lugoloobi S.; 6Wasswa R. and 1Galla N.A
1Makerere University, Uganda; 2International Potato Centre (CIP), Uganda; 3CIP- Tanzania; 4Kyakuwa Farm, Uganda; 5National Livestock Resources Research Institute, Uganda; 6Sight
Farm, Nakyesasa, Wakiso district;
Table of Contents
List of tables....................................................................................................................................3
Summary of results..........................................................................................................................4
Background......................................................................................................................................5
Objectives.....................................................................................................................................5
Materials and methods.....................................................................................................................6
Description of experimental site..................................................................................................6
Experimental animals and experimental design...........................................................................6
Experimental diets........................................................................................................................8
Sweetpotato vine silage production..........................................................................................8
Chloris gayana (rhodes grass) hay...........................................................................................9
Homemade dairy pellets...........................................................................................................9
Chemical analysis......................................................................................................................10
Statistical analyses.....................................................................................................................10
Results............................................................................................................................................11
Chemical composition of the feedstuffs.....................................................................................11
Dry matter intake and live weight changes................................................................................12
Milk yield and composition.......................................................................................................13
Cost of supplementation.............................................................................................................14
Discussion......................................................................................................................................15
Conclusion and recommendation..................................................................................................16
Acknowledgements........................................................................................................................16
References......................................................................................................................................17
2
LIST OF TABLES
Table 1: Allocation and changeover of experimental diets.............................................................7
Table 2: Chemical composition (as offered) of the mineral blocks used in supplementing the
experimental cows*.........................................................................................................................8
Table 3: Simple formula for making homemade dairy pellets........................................................9
Table 4: Chemical composition (g/kg DM) of the feeds used in feeding the lactating dairy cows
.......................................................................................................................................................11
Table 5: Dry matter intake and live weight changes of cows fed the experimental diets.............12
Table 6: Milk yield and composition from cows fed the experimental diets................................13
Table 7: Economics of supplementing dairy cows with varying levels of SPVS.........................14
3
Summary of results
Seasonal feed shortages coupled with the high prices of feed supplements are key constraints to
investment and profitability of smallholder dairy production in Uganda. This study was
conducted to evaluate the effect of sweetpotato vine silage (SPVS) supplementation on lactating
Ankole x Fresian crossbred dairy cattle. Four primiparous cows in their early lactation were
randomly allotted to a basal diet of Chloris gayana hay supplemented with dairy pellets and four
graded levels of SPVS (0, 10, 20 and 30% of the daily ration) in a 4X4 Latin square design. The
animals were given a one-week adaptation period followed by a two weeks’ data collection
period for each diet. Dry matter intake (DMI), live weight changes, milk yield and composition
were determined. Dry matter intake improved with addition of SPVS with intake being highest in
cows that were fed the highest SPVS level (P < 0.05). In vitro organic matter digestibility
increased with SPVS supplementation level. Animals fed diets with 0, 10 and 20% SPVS levels
of supplementation lost weight, however, there were no significant differences (P ≥ 0.05) in body
weight changes with increasing supplementation level. Milk yield increased with SPVS
supplementation although there were no significant differences between the different SPVS
supplementation levels. Milk fat differed (P ≤ 0.05) with supplementation, but there was no
consistent trend observed. Considering profit margins, supplementing dairy cows with SPVS at a
level of 10% of their daily feed intake was most profitable and yielded Uganda shillings 1,290 on
daily basis. In conclusion, SPVS supplementation improved digestibility, DMI and milk yield
but supplementation beyond 10% of the daily feed intake was not cost effective.
4
Background
The seasonal variability in quantity and quality of milk produced by smallholder dairy farmers is
affected by many factors among which is feed quality and quantity. The dry seasons experienced
in Uganda greatly impact on both the quality and quantity of the feed resource base for dairy
animals resulting into reduced productivity and profitability. However, Uganda is among the top
countries in Africa in production of sweetpotatoes (SP) whose residues can be used as animal
feed. Sweetpotato vine silage contributes 40% of the feed resource during the dry season. The SP
vines are bulky, highly perishable and a lot is wasted despite their potential contribution to the
feed resource base for smallholder zero grazing systems.
Sweet potato vine (SPV) silage technology as a technique for prolonging the shelf life of SPV
was tested in Masaka and Kamuli districts under CIP-led RTB ENDURE project as one of the
interventions to reduce feed cost and feed shortage and improve pig production in smallholder
pig production systems in Uganda. The results showed improved performance of pigs fed sweet
potato silage supplemented with a homemade concentrate (Mutetikka et al., 2016). Reports from
dairy farmers in Wakiso, Mukono and Masaka districts showed that dairy farmers had resorted to
supplementation of their lactating dairy cows with SPV silage to buffer variation in quality and
quantity of feed during the prolonged drought. The used SPV silage to improve the diet of their
animals reported to have observed increase in milk yield (Daaki, 2018; personal
communication). However, no research has been conducted in Uganda to assess performance of
lactating dairy cows fed Sweetpotato Vine Silage (SPVS). There was therefore a need to conduct
on-farm trials to verify farmers’ observations.
Objectives
To determine the effect of supplementing crossbred dairy cows with SPV silage on milk
yield, milk composition and live weight gains.
To disseminate information on production and utilization of SPSV technology to dairy
cattle farmers.
5
Materials and methods
Description of experimental site
The study was conducted at Site Farm located in Nakyesasa village, Busukuma sub-county,
Wakiso District. The District lies in the Central region and about which is about 18 Km from
Kampala city along the Kampala- Busiika road. Selection of the farm was based on; willingness
of the farm owner to participate in the study; willingness of the farm owner to allow other
farmers to visit the experimental site for purposes of monitoring and evaluation of the trial and to
learn from participating farmer; having sweetpotato as one of the major crops grown on the farm;
having at least four early lactating mono-porous crossbred dairy cows.
Experimental animals and experimental design
Four lactating crossbreed Friesian dairy cows with exotic blood level of about 83% (first calving)
in their early lactation (3 months after calving) with an average milk yield of 9.21 ± 1.68 liters
per day and average body weight of 422.92 ± 26.15 kg were identified for use in the feeding
trial. Four diets were offered to the animals in a 4 x 4 Latin Square change over design with four
periods each lasting two weeks. Animals were given an adaptation period of one week before the
start of data collection for every period. Apart from the adaptation week before the
commencement of the experiment, were all animals fed on six (6kg) of SPVS, the rest of the
adaptation periods animals were fed on the treatments diets that they received during the data
collection periods. The basal diet consisted of Rhodes grass hay which was offered to ad libitum
to the experimental animals. Each of the animals was supplemented with four (4kg) of dairy
pellets in addition to the SPVS treatment diets so as to provide at least above 12 % CP required
for moderate levels of production (ARC, 1980). The SPVS was offered at 0, 10, 20 and 30% of
the total daily intake. The percentage inclusions translated into 0, 6kg, 12kg, 18kg of SPVS
representing diet I, II, III, IV respectively. The SPVS was offered to the animals following the
order indicated in Table 1 below. The SPVS was offered routinely at 10: 00am while Dairy
pellets were offered in equal proportions just before milking both at 5:00 am and 4:00 pm, and
were consumed during the milking period. Before adding each day's ration, the leftover feed was
removed and weighed. The daily feed intake was determined by subtracting the refused feed of a
6
given day from the total feed offered that day. Feeds were sampled and taken to the laboratory
for chemical analyses.
Table 1: Allocation and changeover of experimental diets
Diets (Based on SPVS supplementation)
Animal Name Period 1 Period 2 Period 3 Period 4
Juliet
Natendo
Nabukenya
Namwanje
II
I
IV
III
III
IV
I
II
IV
III
II
I
I
II
III
IV
The animals were enclosed in individual kraals and were treated against internal and external
parasites before commencement of the experiment and throughout the experimental period. The
animals had free access to clean drinking water and mineral block licks (chemical composition
presented in Table 2). Milking was done twice a day at 5:00 am and at 4:00 pm and the total
daily yields were recorded. Milk samples were collected during the second week of data
collection on each diet, mixed thoroughly and taken to the laboratory to be analysed for protein,
milk fat, total solids and ash. The live body weight changes (kg) of the animals in each treatment
were determined by taking initial weights after the adaptation period for the animals in each
treatment, and subtracting it from the final weights at the end of each data collection period.
7
Table 2: Chemical composition (as offered) of the mineral blocks used in supplementing the
experimental cows*
Ingredient Level (%)
Phosphorus 0.20
Calcium 0.14
Magnesium 0.50
Iron 0.15
Cobalt 0.005
Copper 0.03
Iodine 0.015
Manganese 0.02
Zinc 0.03
Selenium 0.001
Sodium 38
*As guaranteed by the manufacturers Supplied by Coopers Uganda Limited, Kampala (Uganda).
Experimental diets
Sweetpotato Vine silage production
Sweetpotato vines were purchased from both Owino market in Kampala district and farmers’
fields in Seguku and Nakyesasa villages, Wakiso district. After harvesting, the vines were wilted
for 2 to 3 hours depending on the source. Vines from the market already had lower moisture
content compared to those from the field. The wilted material was chopped using a motorized
forage chopper to length of about 2 cm for ease of compaction so as to increase the quality and
storability of silage. It is easier to displace air during ensiling when small pieces are cut. The
chopped sweetpotato vines were weighed and spread on a tarpaulin to be mixed thoroughly with
maize bran. Maize bran was added to chopped vines in a ratio of 1: 10. Maize bran was used
instead of molasses because the bran reduces the quantity of effluent from the sweetpotato silage
(Kabirizi et al., 2017). The mixture was put in polythene tube silos in small quantities and
compressed until the bag was full. The bags were firmly tied with a sisal string excluding the air
8
in order to encourage anaerobic fermentation. The polythene tubes silos were stored in a well-
ventilated store free from rodents until they were ready for use.
Chloris gayana (Rhodes grass) hay
Rhodes grass hay was purchased from the National Livestock Resources Research Institute
(NaLIRRI) in Wakiso district. At the institute the grass was cut when about 10% of the crop had
flowered. The cut material was left in the field to dry for 2 days. The dry grass was raked into
heaps and later baled using a simple bottomless wooden baling box.
Homemade dairy pellets
The pellets were produced using maize bran, cotton seed cake, mineral premix, Calliandra leaf
hay meal and molasses in proportions shown in Table 3. The different ingredients were
thoroughly mixed and after mixing, the mash was delivered to the pellet mill feeder for pelleting.
The extruded pellets had a moisture content of 16-17%, these were then dried to a moisture
content below 12%.
Table 3: Simple formula for making homemade dairy pellets
Ingredient Quantity (kg)
Maize bran 52
Cotton seed cake 18
Mineral premix 2
Calliandra calothyrsus leaf hay 9
Molasses (liters) 18
9
Chemical analysis
Feed samples were oven dried at 600C for 48 hours in a forced draught oven and then ground
through a 1mm sieve for chemical analyses. Dry matter, ash and nitrogen (Kjeldahl-N) in feeds
and refusals as well as milk composition (CP, butterfat and total solids) were determined
according to procedures outlined by AOAC (1990). Acid detergent fibre, NDF and acid insoluble
ash were determined according to procedures outlined by Van Soest and Robertson (1985).
Statistical analyses
The effects of the levels of SPVS on feed intake, body weight changes and milk yield and
composition were tested using Analysis of Variance (ANOVAs) of the General Linear Models
Procedure (GLM) in SAS (1990) for a balanced 4x4 Latin square design using the model below:
Xijk = + i + j + k + ijk; i , j and k = 1 ......a
Where: Xijk = the kth observation on the response variable under the ith treatment
= Over all mean
i = Treatment effect (i = 1…4)
j = Period effect (j = 1…4)
k = Animal effect (k = 1…4)
ijk = Random error effect
Differences among treatment means were compared using Tukey’s test of SAS (1990).
10
RESULTS
Chemical composition of the feedstuffs
Chemical composition of the different diet ingredients is presented in Table 4. Dry matter, NDF
and ADF levels of the ingredients were highest in the Rhodes grass hay (RGH). Sweetpotato
vine silage had a noticeably higher CP level than dairy pellets, and both had high ME levels.
Table 4: Chemical composition (g/kg DM) of the feeds used in feeding the lactating dairy
cows
RGH SPVS Dairy pellets
Proximate Component
Dry matter 830 266 680
Crude Protein 75 194 148
Neutral detergent fiber 780 333 157
Acid detergent fiber 441 186 59
Acid detergent lignin 137 59 40
Ash 104 85 74
ME (MJ/kg DM) 198 772 795
RGH = Rhodes grass hay, SPVS = sweetpotato vine silage
11
Dry matter intake and live weight changes
Intake of CP, NDF, ME and digestibility of the diets were observed to increase as the level of
SPVS supplementation increased (Table 5). There was a general DMI increase with increasing
levels of SPVS supplementation. Dry matter intake was recorded to be lowest at D0 and highest
at D30. There was a general body weight loss from D0 to D30, though a gain in body weight at
diet D30 was recorded. In vitro organic matter digestibility increased with level of
supplementation.
Table 5: Dry matter intake and live weight changes of cows fed the experimental diets
Diets
Parameter D0 D10 D20 D30 SEM
Dry matter intake (kg/day)
Rhodes grass hay 4.1 4.2 4.3 4.4 0.24
Sweetpotato vine silage 0.0 1.6 3.2 4.8 0.00
Dairy Pellets 2.7 2.7 2.7 2.7 0.00
Total DMI 6.8 d 8.5c 10.2b 11.9a 0.24
Total CP intake 0.7 1.0 1.3 1.7 0.02
Total ME intake 44.8 63.4 82.1 101.1 0.72
Total NDF intake 3.7 4.2 4.8 5.5 0.19
Total ADF intake 2.0 2.3 2.6 3.0 0.11
IVOMD (g/kg) 442.1 510.4 549.6 566.0 13.9
Total DMI (%BW) 1.6 2.0 2.4 2.8
Average final weights (Kg)
Live weight changes
414.8
-5.59c
415.4
-1.19a
418.9
-0.29a
432
1.52b
4.87
0.39
Diets D0, D10, D20 and D30 had sweetpotato vine silage at 0, 10, 20 and 30% levels, respectively. a,b,c,d Means
within a row with different superscripts differ significantly (P < 0.05). SEM = Standard error of the mean.
Calculated based on digestibility of individual ingredients.
12
Milk yield and composition
Daily milk yield increased with supplementation although there was no significant difference (P
≥ 0.05) with increasing levels of SPVS supplementation. Milk yield was lowest at D0 and
highest at D10 (Table 6).
There were significant differences (P < 0.05) in butter fat and total solids in milk from cows
across all the diets however, FCM increased and no significant difference (P ≥ 0.05) was
recorded between the levels of SPVS supplementation (Table 4).
Table 6: Milk yield and composition from cows fed the experimental diets
Parameter Diets
Milk yield (kg)
D0 D10 D20 D30 SEM
Daily yield 8.3 b 10.0a 9.8 a 9.9 a 0.26
Fat corrected milk 9.21b 10.21a 10.76a 10.82a 0.28
Milk composition (%)
Total solids 12.9 12.8 12.9 12.8 0.10
Butter fat 4.7a 4.1b 4.7a 4.6ab 0.14
Solids-not-fat 8.2b 8.6a 8.2b 8.2b 0.06
Diets D0, D10, D20 and D30 had sweetpotato vine silage at 0, 10, 20 and 30% levels, respectively. a,b Means within
a row with different superscripts differ significantly (P < 0.05). SEM = Standard error of the mean.
13
Cost of supplementation
The cost of feeding increased with levels of supplementation which resulted into negative profits
at higher SPVS supplementation (Table 7). On the other hand, additional income due to
supplementation increased at D10 and thereafter decreased with incremental SPVS
supplementation levels. The most profitable level of supplementation was achieved when diet
D10 was fed.
Table 7: Economics of supplementing dairy cows with varying levels of SPVS
Diets
Cost of
supplementation
Increase in milk
yield Additional income Profit
D0 0 0 0 0
D10 1410 1.8 2700 1290
D20 2820 1.5 2250 -570
D30 4230 1.6 2400 -1830
Cost of producing SPVS is Ushs 235/kg and price of milk is Ushs 1500/liter
14
Discussion The recorded crude protein content (194g/kg) in this study was higher than what was earlier reported (Khalid et al. 2013, Negesse et al. 2016, Lutwama et al. 2016). These variations are attributable to difference in varieties, foliage to stem ratio and part of the vines that are being ensiled (Aregheore, 2004; Zereu et al. 2014). The dry matter level of 226g/kg in SPVS is within the range reported by (Murugan et al. 2012). The high CP and dry matter levels reported in this study therefore makes SPVS a good feed resource and supplement for diets with limiting protein (Nambi-Kasozi et al. 2016).
Dry matter intake as a percentage of body weight was lowest in cows fed diet D0 possibly due to either rumen fill or limitation of intake as a result of low palatability of the Rhodes grass hay. Dry matter intake and digestibility of the diets increased with supplementation level due to the increase in organic matter digestibility contributed by the SPVS. High In vitro organic matter digestibility of SPVS subsequently improves intake of the basal diet to enhance rumination and raise the rumen pH. These observations are in agreement with Megersa et al. 2012; Ali et al. (2019)
The observed loss of average body weight over the feeding period despite the increasing ME values as the supplementation levels were increased is in agreement with what was earlier reported by Gross et al. (2011). These observations are due to the DMI, milk yield and body weight changes which usually occur in the first phase (4 months) of lactation in primiparous cattle. The weight loss could probably be attributed to a potential negative energy balance or taken as a normal phenomenon in premiparous lactating cows that are experiencing increasing levels of milk yield (Poncheki et al., 2015).
Milk yield was higher and similar in cows fed the different SPVS supplementation levels. This result is due to increased DMI intake hence more nutrient ingestion and nitrogen utilization with increasing SPVS supplementation (Ali et al. 2019). Butter fat content improved with SPVS supplementation though there were no consistent results within levels of supplementation. This can be as a result of increasing levels of fibrous material in the diets known to balance the acetate to propionate levels in the rumen liquor as acetate is a major milk fat precursor ( Kawas and Mahgoub, 2005).
15
Conclusion and recommendation
From this study it can be concluded that SPVS can be used to improve the quality of feed, feed
intake, productivity and quality of milk and profitability as well as buffering the feed shortages
among smallholder dairy farming communities. Sweet potato vine silage has a high crude protein
content which makes it a suitable supplement for lactating dairy animals being fed protein
deficient diets. Supplementing lactating dairy animals with up to 10% SPVS increases body
weight gain and milk yield resulting into a profitable dairy enterprise. Supplementing dairy
animals beyond 10% of the daily feed intake would increase milk yield and body weight but
would not be cost effective.
Farmers should produce SPVS and supplement the basal diet at 10% in order to enjoy the
following benefits;
• An improvement on the nutritional content of the animal diet,
• An increase in milk yield which translates into increased profits,
• Sustaining milk production through the dry spells, periods of feed scarcity and,
• Maintaining the body condition scores of the animals
Acknowledgements
The study was supported by the International Potato Center (CIP), conducted by Bavubuka
Twekembe youths and Kyakuwa Farm and hosted by Sight farm.
16
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