2.- MATERIAL Y MÉTODOS:

The microclimate in a pig pen depends on floor type. Relative humidity and inside temperature were numerically highest in the pens with wooden floors and lowest in the pens with a clay floor (Chapter 6). This may be related to more evaporation due to floor fouling (Voermans and Hendriks, 1995). In their literature review, Gonyou et al. (2006) showed a significant effect of space allowance on ADG. The results of Guingand and Granier (2001) and of Spoolder et al. (2000) show that floor type does not influence growth performance very much if animals are in their thermal comfort zone and if they have the same feed intake. However, in the current study, floor type was associated with differences in growth performance and small differences in feed intake. Pigs reared on wooden floor pens reached a higher final weight and had a higher ADG than pigs on the concrete and clay floor. This can be partly explained by the fact that microclimatic conditions in the wooden floor pens under the tropical climatic conditions are superior compared to other floor types (Chapter 6). Pigs reared on wooden floor pens grew slightly faster than those on other

GENERAL DISCUSSION

___________________________________________________________________________

floor types. These growing pigs also ate slightly more when housed on wooden floors, a finding in accordance with the Hansen et al. (1982).

The situation in the farrowing pens is complicated since suckling piglets have higher temperature requirements than lactating sows. The upper limit of the zone of thermal comfort (i.e. above the higher critical temperature) is around 22°C for the sow, whereas the lower limit is around 30°C for suckling piglets (Black et al., 1993). When the environmental temperature rises above the evaporative critical temperature of the sow, the sow can only control body temperature by increasing heat loss through evaporation or by reducing its heat production by eating less. Black et al. (1993) and Messias de Bragança et al. (1998) report a decrease in voluntary feed intake of 40 % and 43 % in lactating sows when the temperature is raised from 18° to 28°C and 20° to 30°C, respectively.

Piglet mortality within the first three days of life remains a problem in intensive swine farms (Spicer et al., 1986). Mortality rates vary between 10 and 20 % (Tuchscherer et al., 2000) depending on the housing system. In an earlier study with data obtained over 5 years on 761 farrowings of sows, Grissom et al. (1990) found an overall pre–weaning death loss ranging from 12.2 to 24.2 %. This mortality level is higher in pens than in crate systems. Preweaning mortality may be associated with stress and this may explain the lower risk for influenza A infections according to Ewald et al. (1994). Less stomach and intestinal disorders were found by Christensen et al. (1995) in pigs on straw systems compared to slatted floors. The studies here indicate that nursing piglets kept with the sows may best be housed on wooden floors as this results in less diarrhoea and mortality compared to concrete clay floors. The present study however did not measure welfare parameters of lactating sow which may be compromised on wooden slatted floors. The piglets raised on the concrete floor and clay ground floor had a higher frequency of diarrhea and higher mortality.

CONCLUSIONS

1. Diets used for both fattening pigs and sows in three ecological zones – Upland, Lowland and Coastal areas in Central Vietnam have poor overall nutritive

CHAPTER 7

___________________________________________________________________________

163

value, especially diets in Upland areas. Intake in nutrients and energy is considerably below requirements.

2. Pigs on smallholder farms can improve production if the pigs are fed a higher protein level in their diet. This can not only supply more pig meat for the farmer and a higher profitability and as such increase the rural economy in Central Vietnam.

3. Genotypes such as F1 and F2 show better growth performance and carcass

quality compared to local Mong Cai pigs under typical Vietnamese climatic conditions. Animals with the highest protein gain like F₂ require the highest dietary protein (amino acid) levels to support their higher rate of protein deposition. Because the innate fat level in the body of Mong Cai pigs is high, it can not be expected that this can be changed considerably by a high dietary crude protein content. An increase above the optimum will not change growth rates and backfat measurement considerably.

4. Increasing dietary crude protein levels in pig diets increases protein deposition rate in all pig genotypes commonly held in Vietnam. Genetically lean pigs have higher growth rates and give leaner carcasses compared to Mon Cai pigs at all dietary crude protein levels under practical conditions in Vietnam. The present results confirm previous data with regard to breed in relation to energy partitioning between protein and lipid deposition.

5. Increasing the dietary lysine level from 0.75 to 1.20 % showed a possitive effect on performance of Mong Cai sows during lactation and piglets. The sows fed the diet supplemented with lysine decrease weight loss compared to sows without supplemental lysine in their feed. In these studies, the optimum level based of Mong Cai lactating sows was approximately 1.02 % lysine. The level during lactation has no effect on the number of piglets in the beginning of lactation but can affect the number of weaned piglets providing opportunities to increase pig performance in Vietnam.

6. High dietary lysine level in the sow diets increases piglet weight of Mong Cai sows at 21d (from 0.20–0.52 kg/piglet) and weaning weight (from 0.3–1.95 kg/piglet) compared to piglets born from sows fed no supplemental dietary lysine. Again pig performance in Vietnam can be increased by supplementation of diets with lysine.

GENERAL DISCUSSION

___________________________________________________________________________

7. Wooden floors had a positive effect on sow and piglet performance under the typical, tropical Vietnamese climatic conditions.