Effects on sow reproduction and piglet performance of replacing soybean meal by a mixture of sweet potato leaves, water spinach and fresh cassava foliage in the diets of Mong Cai and Yorkshire sows

Hoang Nghia Duyet, Truong Thi Thuan and Nguyen Duc Son

Hue University of Agriculture and Forestry
Hue, Vietnam
duyethue2004@yahoo.com

Abstract

The effects on the reproductive performance of Mong Cai (MC) and Yorkshire (Y) sows of three levels of foliage in the diets in gestation and lactation were evaluated. Dietary treatments 0L, 50L and 100L corresponded to replacement of 0, 50 and 100%, respectively, of the soybean meal in gestation and lactation diets by a foliage mixture consisting of equal parts of water spinach, cassava leaves and sweet potato leaves on a dry matter (DM) basis.

 DM and nutrient intakes were not affected by treatment in gestation. Litter size at birth was not influenced by dietary treatment, but mean piglet live weight and total litter live weight (LW) at birth were significantly lower (P<0.05) in treatment 100L for Y sows. Treatment 100L resulted in significantly lower mean piglet and total litter weaning weight for both MC and Y sows, but the differences between 0L and 50L were not significant. Sow feed consumption to produce 1 kg of piglet at weaning was higher in treatment 100L than in 0L and 50L. Sow LW losses during the lactation period, and weaning to service interval, were higher for treatment 100L for both MC and Y sows. The differences for all other parameters measured between 50L and 0L were small and non-significant.

It is concluded that the optimum level of replacement of soybean meal by a mixture of foliages in pregnancy and lactation diets is 50% for both MC and Y sows. MC sows appear to be better adapted to high levels of foliages in the diet than Y sows.

Keywords: Foliage, litter size, litter weight, live weight loss, oestrus

Introduction

In Vietnam around 285,000 ha are used for growing sweet potato, nearly 300,000 ha for cassava and about 250,000 ha for water spinach (Lich Le Ba 1996; Nga Lam Quanget al 2000). All of these crops produce leafy biomass which is traditionally used by farmers in Central Vietnam for feeding to pigs, especially the sows of the local Mong Cai breed.

Vietnam has about one million Mong Cai (MC) sows (50% of the total sow population), concentrated in Northern and Central Vietnam (Lich Le Ba 1996). However, recently Yorkshire (Y) pigs have been imported in order to improve pork quality. Traditional feeding of MC sows in Central Vietnam is based on large amounts of vegetables, such as sweet potato leaves, water spinach, and fresh cassava foliage. These forages are very useful as feeds for MC sows, because the sows do not become so fat during pregnancy, and the milk production is higher. They also provide vitamins and minerals. Hoang Nghia Duyet (2003) and Hoang Nghia Duyet et al (2004) showed that sweet potato leaves could be fed to MC sows at levels of from 30 to 40 % (DM basis) in pregnancy and 20 to 30 % in lactation, with similar reproductive performance as when only soybean and fish meal were the main sources of protein.  .

The objective of the research reported in this paper was to extend the work with forages, by using mixtures of leaves at levels from zero to 100% replacement of soybean meal, and by comparing responses in MC sows with those of the exotic Yorkshire breed,

Material and methods

Experimental design

Two factors were tested, breed and protein source:

Breed:

Nine local MC sows and nine Yorkshire (Y) sows were used in the experiment, and were followed for one complete reproductive cycle.

Protein source

Soybean meal and a mixture of water spinach, cassava leaves and sweet potato leaves were compared as protein supplements. Three dietary treatments were compared as supplements to the basal diet of rice bran and cassava root meal (Tables 1 and 2):

·         0L: 100% of dietary protein supplied by soybean meal (no green foliage supplied).

·         50L: 50% of the protein was supplied by soybean meal and 50 % by a mixture of water spinach, cassava leaves and sweet potato leaves (equal parts of each foliage on DM basis)

·         100L: 100% of the supplementary protein was supplied by the forages..

Table 1. Content of DM and crude protein in the diet ingredients
	DM, %	Crude protein, % in DM
Rice bran	87.8	11.6
Cassava root meal	87.4	3.3
Soybean meal	88.5	41.8
Sweet potato leaves	13.4	17.8
Water spinach	10.6	19.8
Cassava leaves	25.7	25.6

Animals

Nine MC and nine Y sows in parities 3 to 5 were selected from Tien Phong farm. Initial live weights were 80 - 90 kg for the MC sows, and 180- 200 kg for the Y sows. Within breed they were allocated at random to the three diets. All sows were mated by AI with semen from the same Y boar and were kept in individual pens with concrete floors. The sows were introduced to the experimental diets three weeks after mating.

The amount of feed (DM basis) was the same within breed and treatment (Table 2). In the lactation period the sows were fed increasing amounts up to five days after farrowing, and from then onwards feed was offered feed ad libitum.

Growing and processing of the foliages and experimental diets:

Sweet potato, water spinach and cassava plants were purchased from local farmers, and were harvested by taking some of the leaves from cassava and sweet potato plants grown for root production. Both leaves and stems of water spinach, grown in the low-lying areas of the farms, were harvested. The foliages were chopped into 0.5 -1 cm lengths and mixed in the ratio of 1:1:1 (DM basis) (8, 10 and 4 parts by weight, respectively, on fresh matter basis) and then fed the following day. Before feeding,  the foliages and concentrate meals were weighed and mixed according to treatment, and fed 2 times per day.

Stastistical analysis

Data were treated by analysis of variance (ANOVA) using the General Linear Model (GLM) of the MINITAB (2000) software. Sources of variation were diet, breed, interaction diet x breed and error.
 

Results and discussion

Daily allowances were restricted during pregnancy, and there were no feed refusals. The foliage mixture made up 25% of the DM of diet 50L and 40% of the DM of diet 100L. In lactation, neither of the breeds was able to consume the planned amount of dry matter on the forage diets (Figure 1) which was only about 80% of the planned amount for the 100L diets. There was an indication that the Mong Cai sows were able to consume more than the Y sows on the all-forage supplements.

Figure 1: Amounts of DM consumed during lactation expressed  as a fraction of the 0L diet = 1

Live weight at mating and farrowing, live weight gain during pregnancy, and litter size and weight at birth did not differ among treatments (Table 3), and were within normal ranges for the two breeds. Litter birth weight from MC sows was not affected by diet,  but for the Y sows litter live weight at birth was lower in treatment 100L (P<0.05), probably as a result of the lower DM  intakes of the sows on the high foliage diet.

Total litter weight at 21 days of age did not differ between treatments 0L and 50L, in both MC and Y sows, but was lower on the 100L diet (Table 4). Litter size at weaning was not affected by diet in both MC and Y sows.  Feed conversion ratio (kg feed/ kg piglet) was better for treatments 0L and 50L compared with 100L and for both MC and Y sows.

Live weight losses during lactation were higher in treatment 100L than in 0L and 50L and were more marked in Y than in MC sows. The mean number of days to re-mating of the sows was higher in treatment 100L than in treatments 0L and 50L, with the effect being more marked for Y than for MC sows. The relationship between live weight loss during lactation and days from weaning to mating (Figure 2), and the marked differences between breeds for these parameters (Figures 3 and 4), indicates that the Y sows were less able to adapt to the all-foliage supplement than the MC sows.

Figure 2: Relationship between loss in live weight during lactation and days from weaning to mating (dark blue dots are the Y sows)

Figure 3: Mean values for percentage weight loss during lactation for Mong Cai and Yorkshire sows	Figure 4: Mean values for days from weaning to mating percentage for Mong Cai and Yorkshire sows

Conclusions

• A mixture of foliages (sweet potato leaves, water spinach and cassava leaves) can replace 50% of a conventional protein supplement for both MC and Yorkshire sows without affecting piglet performance or sow reproduction

  
  

• Replacing 100% of the soybean meal by a foliage mixture increased live weight losses of the sows and the interval from oestrus to mating, and reduced piglet weight gains to weaning, the effects being more marked for Yorkshire than for MC sows.

  
  

• Mong Cai sows are better adapted to high levels of foliage in the diet than Yorkshire sows.

References

Hoang Nghia Duyet 2003 The effect of sweet-potato stem levels in the diet on productivity of Mong Cai sows. Science and Technology Journal of Agriculture and Rural Development, No 6 (2003), p. 707.

Hoang Nghia Duyet, Nguyen Dinh Son, Nguyen Van An and Truong Thi Thuan 2004 Effect of high dietary levels of sweet potato leaves on the reproductive performance of pure and crossbred Mong Cai sows; Livestock Research for Rural Development (15) 6 Retrieved May 2, 2004, from http://www.lrrd.org/lrrd15/6/duye156.htm

Lich Le Ba 1996 Livestock production of Vietnam in the passing years and development orientations to year 2000. National Seminar on Animal Sciences and Development to Year 2000. p 13.

Nga Lam Quang, Ulf Magnusson and Brian Ogle, 2000 Evaluation of the reproductive performance of an indigenous pig breed in Vietnam (Mong Cai) and cross-breed fed on local and conventional feeds. Proceedings of National Seminar-Workshop on Sustainable Livestock Production on Local Feed Resources. Ho Chi Minh City, Vietnam, January 18 - 20, 2000. p 83. http://www.mekarn.org.sarpro/nga.htm

Received 15 January 2010; Accepted 15 February 2010; Published 1 March 2010

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