Effects of inclusion of cassava leaf in the diets on the performance of pregnant sows

Bui Huy Nhu Phuc and Brian Ogle*

University of Agriculture and Forestry, Ho Chi Minh City, Vietnam
bphuc.ldanh@hcm.fpt.vn
* Swedish University of Agricultural Sciences, Sweden

Abstract

In total 40 Yorkshire x Landrace pregnant sows from the 2 ^nd to the 5 ^th litter were allocated to 4 dietary treatments, and given diets with 0 (CLM0), 10 (CLM10), 20 (CLM20) and 30 % (CLM30) inclusion of cassava leaf meal (CLM). Treatment groups were balanced for breed and litter number. The sows were fed the experimental diets from 21 days of pregnancy to farrowing.

For treatments CLM0, CLM10, CLM20 and CLM30 the mean number of piglets born/litter was 9.9, 12.7, 11.2 and 11.7, respectively, and number weaned/litter 8.50, 10.1, 9.18, and 9.33, respectively. Birth weights per piglet were 1.59, 1.42, 1.67 and 1.43 kg, and total litter weight 15.5, 17.6, 16.9 and 16.6 kg, respectively. The mean weaning weights per piglet were 6.31, 6.11, 6.20 and 6.56 kg , respectively, and total weaning weights per litter increased by on average 5.6 % in the CLM fed groups, and were 54.2, 61.6, 56.8 and 61.4 kg/litter, respectively.

It was concluded that up to 30 % of cassava leaf meal can be included in the diet of pregnant sows without any detrimental effects on reproduction.

Keywords: cassava leaf, pregnant sows, litter size, piglet weight.

Introduction

Cassava (Manihot esculenta Crantz) is a widely grown crop in most countries in the tropical regions of Africa, Latin America and Asia, and ranks as one of the main crops in the tropical countries (Calpe 1992). Dried cassava leaves (CL) are a good source of protein, minerals, and vitamins. The yield of cassava leaves (as dry matter, DM) as a by product of root harvesting may amount to as much as 4.6 tones/ha (Ravindran et al 1990). With adequate irrigation, fertilization and harvested from 4 months of age in a cycle of 60 - 75 days, annual leaf DM yields of over 21 tons/ha can be obtained (Ravindran 1993).

Numerous reports have shown that cassava leaf has a high but variable protein content (170 to 400 g/kg CP on a dry matter basis), with almost 0.85 of the crude protein fraction as true protein (Ravindran 1993). While cassava leaf protein is low in sulfur amino acids (Gomez and Valdivieso1984), the content of most other essential amino acids is higher than in soybean meal (Eggum 1970). However, the high fiber content of leaf meals is a major factor limiting their exploitation as a source of protein and other nutrients for non-ruminant animals (Just 1982a,b). Sows should be able to digest high fibre diets more efficiently than growing pigs, and pregnant sows can use high fiber diets at up to 9-12% crude fibre in the diet DM. Anti-nutritional factors, such as HCN and tannins, can possibly limit the use of this product in sow diets. However very little research has been done on the effects of cassava leaf meal (CLM) on sow performance.

Therefore, the main objectives of this study were to determine the optimum level of inclusion of sun-dried cassava leaves in diets for pregnant sows with respect to effects on reproductive performance.

Materials and methods

Animals

In total 40 Yorkshire and Landrace sows at 21 days of pregnancy, and from 3^rd to 6^th litter were allocated into 4 treatments (10 sows per treatment) to determine the effects of cassava leaf meal in the pregnancy diet on performance. The sows were balanced for breed and litter number among treatments.

Experimental diets

Four levels of cassava leaf meal of 0, 10, 20, and 30% CLM (of DM) were included in the basal diet to give treatment CLM0, CLM10, CLM20, and CLM30 respectively. The basal diet included maize, cassava root meal, rice bran, soybean meal, fish meal and mineral and vitamin supplements. Oil was added to treatment CLM30 to balance the energy content. CLM replaced rice bran (on a w/w basis). The feed formulation and chemical composition of the diets are shown in Table 1.

Table 1. Ingredient and chemical composition of the experimental diets
	CLM0	CLM10	CLM20	CLM30
Maize	371	370.2	379.6	379.2
Cassava root meal	100	100	100	100
Rice bran	373.2	273.2	173.2	73.2
Cassava leaf meal	0	100	200	300
Oil	0	0	0	5.3
Soybean meal	60	60	54	52
Fish meal	68.5	68.5	68.5	68.5
Limestone	13.2	13.2	9	5.3
Salt	3.8	3.8	3.8	3.8
Monocalcium phosphate	4.7	5.5	6.3	7.1
Premix	3	3	3	3
Total
Chemical composition
ME (kcal/kg)*	2971	2947	2938	2957
Crude protein	14.7	15.5	16.2	16.96
Ether extract	6.50	6.13	5.80	5.44
Crude fiber	5.68	5.97	6.25	6.53
Lysine*	0.92	0.98	1.03	1.09
Methionine*	0.31	0.33	0.34	0.36
Calcium	0.84	0.95	0.91	0.89
Phosphorus	0.76	0.73	0.70	0.67
*Calculated values

Cassava leaves were collected at root harvesting time, and sun dried for 2 days then ground to pass a 1 mm screen before mixing with the other ingredients. The cassava leaf meal was included in the diets from the 21^st day of pregnancy to farrowing.

Pens and feeding regime

Sows were kept in individual pens with a concrete floor during the pregnancy period, and in crates in lactation. Piglets had a closed heated areas to protect them against the cold for 2 weeks after birth.

During the pregnancy period sows were fed restricted diets, with the daily feed allowance according to the following schedule. In the first stage (from the 1^st day after insemination to 84^th day of pregnancy) the sows were fed 1.6 to 1.8 kg/day. In the second stage (from day 84 to 107) they were fed 3.0 to 3.5 kg per day. In the lactation period (from farrowing to weaning of the piglets) the sows were fed ad libitum a diet without cassava leaves. Piglets were fed a commercial pre-starter (21.5% crude protein) from day 7 to weaning (28 days). Sows and piglets were given free access to water from nipple drinkers.

Chemical analysis

Cassava leaves and the experimental diets were analysed for crude protein (CP), ether extract (EE) and crude fiber (CF) according to AOAC (1998). NDF was determined by the method of Van Soest et al (1991).   Energy and amino acid concentrations were calculated from feed composition tables.

Observations

Sow performance was evaluated with respect to feed intake in both pregnancy and lactation periods, weight gain during pregnancy and weight loss during lactation. The effect of cassava leaf fiber on the occurrence of MMA problems was also determined with respect to the rectal temperature of the sows after farrowing. Weaning to service interval was also recorded

Piglet performance included data on litter size, survival rate at birth and weaning, weight at birth and at weaning and finally an economic evaluation was carried out based on a comparison of feed costs among treatments.

Statistical analysis

The General Linear Model of Minitab Statistical Software Version 13 (2001) was used. Least -square means (LSM) were compared statistically using the Tukey test (P<0.05). Regression analyses of the effect of level of CLM inclusion against number of piglets born and weaned were done using the regression models in the Microsoft Excel spreadsheet.

Results and discussion

Chemical composition of diets

Chemical composition of CLM was: CP, 22.5%; lipids, 5% and fiber, 8.8 %. The replacement of rice bran by CLM did not change the energy content of the diets significantly, but led to increases in the CP content. The fiber content of the diets increased gradually with inclusion level of CLM, the difference amounting to 0.3% CF for each 10% increase in CLM inclusion (Table 1)

Effects of inclusion level of CLM on sow performance

The number of piglets born was higher in the groups fed CLM than in the control group, by 1.3 to 2.8 piglets/litter. The highest litter size was for the treatment CLM10.

 

Table 2. Effects of inclusion of CLM in the diet on the performance of pregnant sows
	CLM0	CLM10	CLM20	CLM30	SEM
Number of sows	10	9	10	10
No of piglets born/litter	9.9	12.7	11.2	11.7	0.92
No of weaned pigs/litter	8.5a	10.1 b	9.2 a	9.4 a	0.35
Birth weight (kg/litter)	15.5	17.6	16.9	16.6	1.34
Birth weight  (kg/piglet)	1.6	1.4	1.7	1.4	0.07
Weaning weight/litter (kg)	54.0	61.6	56.8	61.4	3.1
Weaning weight (kg/piglet)	6.2	6.1	6.2	6.6	0.22
a b Means within rows with different superscripts differ (P<0.05)

The highest number weaned was for the treatment CLM10.  and was 10.1 piglets/litter. On average the number of piglets weaned in the CLM fed groups was 1 piglet/litter higher than in the control group. Due to higher litter size, the total weaning weights per litter were higher in the CLM fed groups, the differences ranging from 2.8 to 7.6 kg/litter.

The higher performance of the CLM fed groups was possibly due to the higher content of vitamins and minerals and the better amino acid profile of CLM than of rice bran. Especially beta-carotene can increase the production of uterine specific proteins which support embryo survival. It also contains a basic glycoprotein with iron-binding capacity and a group of acidic proteins with immuno- suppressive capabilities. Beta-carotene also increases the production of progesterone during the initial formation of the corpora lutea.

Feed intake

The sows consumed similar amounts of feed during pregnancy because feed was restricted (Table 3). There were no feed refusals recorded during the experimental period, even at the highest level of inclusion of cassava leaf meal.

Table 3. Effects of inclusion level of CLM on feed intake of sows and weight changes during the experiment
	CLM0	CLM10	CLM20	CLM30	SEM
Feed intakes, kg/day
Pregnancy	2.3	2.3	2.3	2.3	0.01
Lactation	4.9	4.9	5.0	5.1	0.04
Weight changes, kg
Pregnancy
Initial weight at  21 days	194	193	191	200	7.7
Weight at 107 days	235	233	230	238	6.9
Weight gain	40.6	40.0	39.5	38.3	3.2
Lactation
After farrowing	221	217	216	219	7.2
At weaning	201	197	198	201	6.3
Weight loss	20.0	19.9	18.1	17.3	3.4
%  weight loss	9.05	9.17	8.38	7.25

Body weight changes

The mean weight gain during pregnancy was around 40 kg. There were no differences among treatments both during pregnancy and lactation

The average body temperatures of the sows during the 5 days after farrowing for treatments CLM0 to CLM30 were 38.7, 38.7, 38.6, 38.6 ^°C, respectively. This shows that sows in the experiment did not have MMA problems. There were no differences in weaning to service interval among treatments, and it ranged from 5.2 to 5.3 days.

HCN

There were no sign of toxicity recorded in sows and piglets during the experiment. It can be concluded therefore that the CLM used in the experiment was safe for animals, even at the high level (CLM30) of inclusion in the diet. This might have been due to the fact that the HCN level in dried leaves was low, as other studies have shown that 90 % of HCN is eliminated during sun drying (Bui Huy Nhu Phuc et al 2001).

Conclusions

• Pregnant sows can utilize high fiber diets, and so cassava can be a useful feed ingredient for sows during pregnancy. It is not only high in protein but also in vitamins and minerals. It can give good reproductive performance.

References

AOAC 1998 Official methods of analysis, Association of Official Analytical Chemists, 13^th edn. Washington DC.

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