Effect of Floor Density and Feeding System on The Weights of Bursa of Fabricius and Spleen as Well as the Plasma Triiodothyronine Level of Bayang Duck

MATERIALS AND METHODS

An experiment used 80 Bayang Ducks since 2 weeks old with mean initial body weight 132 ± 0.39 g, until finishing of 6 weeks experimental period. Treatments were two floor density i.e. D₁ 0.48 m²/duck and D2 0.08 m²/duck as well as feeding system i.e. F1 ration feeding and F2 free choice feeding.

Feedstuffs consisted of green maize, rice bran, fish meal, soy-bean cake, coconut cake, bone meal and coconut oil. The ration (F1) was formulated from all upper feedstuffs with its energy and crude protein contents of 3000 kcal/kg and 22 % respectively for starter ducks (< 4 weeks old) as well as 2800 kcal/kg and 18 % for the grower ones (4-8 weeks old) (NRC, 1994). The treatment of free choice feeding (F2) was served from the all feedstuffs and each of them in the same amount with the feedstuff was used in formulating the ration (F1).

The measured variables consisted of:

All the collected data were analyzed with Split Plot Design in Completely Randomized Design (Steel and Torrie, 1993).

RESULTS AND DISCUSSION

As showed in Table 1, 2 and 3, analysis of variance resulted in significantly difference in the effect of floor density as well as feeding system (P < 0.05) on bursa of Fabricius weight, spleen weight and triiodothyronine (T3) in blood plasma.

Treatment effect on relative weight of bursa of fabricius and spleen

Table 1 showed that average weight of bursa of Fabricius of Bayang Duck rearing in floor density D1 was 1.211 g/kg bw. It was significantly higher than that rearing in floor density D2 (1.094 g/kg bw). The duck consumed ration feeding (F1) also had significantly higher average weight of bursa of Fabricius (1.176 g/kg bw) that of free-choice feeding (1.128 g/kg bw).

Table 2 showed the same trend on spleen relative weight. Table 2 showed that average weight of spleen of the duck rearing in floor D1 was 1.079 g/kg bw. It was significantly higher than that rearing in floor D2 (0.922 g/kg bw). The duck consumed ration feeding (F1) also had significantly higher average weight of bursa of Fabricius (1.029 g/kg bw) that of free-choice feeding (0.973 g/kg bw).

Reduction of relative weight of bursa of Fabricius and spleen because of low floor density indicated that there had accured disturbances of disposal of the in body accumulated heat to the environment. That condition logically caused heat stress in the duck. Yunianto et al. (1999) reported that heat stress in animal stimulated the increment of plasma corticosterone hormone and Siegel (1995) found that corticosterone eliminated growth of lymphoid organs (bursa of Fabricius and spleen). It could lead into disturbances of immune system production in the body and reduction in growth rate of the animal. Reduction of growth rate and low amount of lymphocyte which were due to the corticosterone increment in blood plasma approved through several experiments by Kusnadi (2004 and 2006), Kusnadi et al. (2005), Onbasiler et al. (2008) and Zulkifli et al. (2000). Hecker et al. (2002) and Puvadolpirod and Thaxton (2000) also summarized their experimental results that reduction of relative weight of bursa of Fabricius and spleen occurred in the low floor density as well as in the treatment of exogenous corticosterone hormone in broiler chicken.

In Tables 1 and 2 were also displayed that average relative weights of bursa of Fabricius and spleen with ration feeding were 1.176 and 1.029 g/kg bw, respectively. They were significantly higher in comparison to those of free choice feeding (1.128 and 0.973 g/kg bw). It could be understood that free choice feeding had potentiality of nutrient deficiency which reduced growth rate and include lymphoid organs (Sunder et al., 2008). An experiment from Kwak et al . (1999) also resulted in reduction weight of bursa of Fabricius, spleen and thymus because arginine deficiency.

Treatment effect on plasma triiodothyronine (T₃): Table 3 showed that average hormone T3 level of the duck raising in the floor D1 (1.262 nmol/L) was significantly higher than that of the duck in the floor D2 (1.129 nmol/L). As effect of feeding system, T3 level of the duck with ration feeding (1.259 nmol/L) was significantly higher than that of free choice feeding (1.132 nmol/L).

Triiodothyronine (T3) has function in metabolic process through increment of oxygen consumption (Shibata et al., 2007) and its effect much more optimal at condition of the comfortable temperature zone, which resulted in higher growth rate (Decuypere dan Buyse, 2005). However, reduction of plasm T3 level in stress condition negatively affected the growth rate (Gerart et al., 1996, Kusnadi et al., 2009 and Sugito et al., 2007). It was approved that crowed ducks in floor caused difficulty in loosing body heat into the environment. Finally, the duck could decrease both growth rate as well as weight of lymphoid organs. The way to subtract accumulated body heat, the duck drank much and decreased feed consumption. Meanwhile, synthesis and secretion of the active calorigenic hormone T3 were also decrease (Decuypere and Buyse, 2005).

Table 1:	Treatment effect on average relative weight of bursa Fabriciusi (g/kg bw)
a,bMean with different superscript in same row/column differ significantly (p<0.05)

Table 2:	Treatment effect on average relative weight of lymph (g/kg bw)
a,bMean with different superscript in same row/column differ significantly (p<0.05)

Table 3:	Treatment effect on average of plasma triiodothyronine level(nmol/L)
a,bMean with different superscript in same row/column differ significantly (p<0.05)

The low level of hormone T3 with free choice feeding might be due to deficient nutritional consumption. Its effects on reduction of growth rate and T3 synthesis were approved by lower feed consumption and lower body weight of the F2-ducks in comparison to those of F1 (Kusnadi and Rahim, 2009). Decuypere and Kuhn (1984) reported that blood plasma T3 of poultry was under effect of environmental temperature, age, healthy status and feeding.

Conclusion: It could be summarized that relative weights of bursa of Fabricius as well as spleen and T3 level in blood plasma were higher with floor density 0.48 m²/duck or with ration feeding than those with floor density 0.08 m2/duck or with free-choice feeding.