Abstract

 The aim of the present studies was to evaluate the potential utilization of local forages as sources of protein in diets for growing pigs in Cambodia. The research was conducted in four experiments of which one trial was on agronomy and the other three trials with pigs.

The first experiment was a study on the effect of level of effluent from plug-flow biodigesters loaded with pig manure as fertilizer for mulberry (Morusalba) trees. The trial included six treatments with four replications, divided into 4 blocks according to a Complete Randomized Block Design. The effluent application levels were: 0, 100, 250, 400, 550 and 700 kg N / ha / year). Effluent was applied every 7 days. Mulberry foliage was harvested (cutting height 60 cm above ground level) after 3 months and again at 2 month intervals. Dry matter biomass yield of mulberry foliage increased linearly with increasing amount of effluent N applied. Crude protein content of leaves increased with effluent level but there were no changes in the stems. Soil content of N and OM increased in direct relationship with the quantity of biodigester effluent.

The second experiment was on the effect of replacing rice bran and fish meal by fresh or dried mulberry leaves on digestibility and nitrogen retention in pigs. Two trials were conducted in this study. In trial 1, a double 4x4 Latin square design in a 2x4 factorial arrangement was used. The treatments were levels of mulberry leaf meal (MLM) of 0, 15, 30 and 50% on a dry basis in diets based on rice by-products fed to 8 young castrate male Mong Cai pigs with a mean weight of 15 kg. Apparent digestibility of DM and organic matter tended to increase with increasing levels of dietary MLM. N balance indices improved with the inclusion of MLM in the diet, and this effect was significant for N retention when expressed as proportion of the digested N. In trial 2, six Large White castrate male pigs, weighing on average15 kg, were allocated, according to a balanced two period change-over design (Gill 1978; Gill and Magee 1976) to two diets containing mulberry leaves, either in sun-dried, milled form or chopped fresh. There were no effects of treatment on coefficients of apparent digestibility of DM, organic matter and N but dry leaves tended to be associated with slightly lower digestibility values. N balance tended to be better in pigs fed fresh mulberry leaves compared to mulberry leaf meal. 

The third experiment was on the effect of fresh mulberry leaves and sweet potato vines on growth performance of pigs fed a basal diet of broken rice. Twelve crossbred pigs (range of 15 to 20 kg weight) were allocated to three treatments with 4 replications in a completely randomized design (CRD) and fed a basal diet of broken rice (restricted to 2% of LW as DM) supplemented with fresh mulberry leaves, fresh sweet potato vines or a mixture of the two foliages. The overall period of 0-90 days, intakes of DM and crude protein, and live weight gain were highest for pigs fed the diet supplemented only with sweet potato vines with lowest values for pigs fed only mulberry leaves as the supplement. There was a tendency for feed conversion to follow a similar pattern.  DM intake and growth rate were positively correlated (R² = 0.83). It was found that the benefits of the sweet potato vines are their superior palatability compared with mulberry leaves, which resulted in higher intakes of DM and crude protein and better pig performance.

The final experiment was on the effects of combinations of mulberry leaves and ensiled taro foliage (leaves and stems) on digestibility and N retention of growing pigs fed a basal diet of cassava root meal and sugar palm syrup. Four castrated male crossbred pigs (Large White X Local breed) of average live weight 34kg were given four diets according to a 4*4 Latin square design. In each Latin square there were 4 periods each of 12 days, 7 days for adaptation and 5 days for faeces and urine collection. The total intake of DM and organic matter were higher in the treatments that contained Taro silage. As the percentages of fiber and NDF were lower in the Taro silage than in the mulberry leaves, this was reflected in lower intakes of these fractions on the treatments with ensiled taro foliage. There were no consistent differences in apparent digestibility of DM, OM, CP and NDF among the diets. The values were relatively high for all the treatments reflecting the low (cassava root) or zero (sugar palm syrup) levels of fiber and NDF in these feed ingredients, which together represented 49% of the diet DM. Four of the essential amino acids (Arginine, lysine, methionine and threonine) apparent digestibilities were higher in the diets containing ensiled Taro foliage with the highest value tending to be on the diet with mixed mulberry silage and Taro silage. Values for N retention, expressed as g/day or as a percentage of N intake or N digested, were highest for the diet with mixed silages from mulberry and Taro with a tendency for the Taro silage (ETCS) to be also better than the diets with fresh and ensiled mulberry only (FMCS and EMCS). When the data for N retention were corrected for differences in N intake, the differences in N retention were more pronounced in favor of the dies containing ensiled Taro.

The overall conclusion is that mulberry leaves, either fresh, dried or ensiled, can be the only protein supplement for growing pigs. However, the results will be better when the mulberry leaves are fed in combination with fresh sweet potato vines or ensiled Taro foliage.

Keywords: Adaptation, biomass, crude protein, cassava root meal, digestibility, DM intake, fertilizer, feed conversion, leaves, mulberry, petioles, pigs, palatability, sugar palm syrup, soil, stems, taro.

chivphiny.phdthesis