| Summary: | 碩士 === 國立中興大學 === 畜產學系 === 87 === The objectives of this experiment were to investigate the extent of association between regulating small intestinal energy metabolism and growth performance in broiler chicken basing on the effects of administration of either T3, which broadly enhances whole body energy metabolism, or dopamine (Dopa), which declines intestinal oxygen uptake, on the growth performance and small intestinal oxygen consumption.
The objectives of the first experiment were to investigate an optimal way, either peritoneally injection or dietary supplementation, of administration of T3 or dopamine to broiler chicks during 6-15 day-old on their growth performance, intestinal weights, and weights of other organs. Six 6-day-old chicks were randomly allotted into one of the 11 treatments. The 11 treatments were peritoneally injected 0, 0.37, 0.74, 1.48, and 2.96mole T3/(Kg BW) , or 0, 0.07, 0.14, 0.28, and 0.56mole Dopa/(Kg BW) as well as a control that was without injection. After 4 replications, there was a total of 264 chicks used. The results showed that the heart weight % of feed-deprived body weight of the chicks injected 2.96mole T3/(Kg BW) was higher than that of control. Other variables measured were not significantly different among the treatments. Another trial in the experiment 1, Six 6-day-old chicks, after body weight measured, were randomly allotted into 9 treatments, namely, dietary supplementation of 0.56, 1.12, 2.24, and 4.48mole T3/(Kg diet), or 0.40, 0.80, 1.60, and 3.20mole Dopa/(Kg diet) as well as a control that was not supplemented. After 4 replication proceeded, there was a total of 216 chicks used. The results of this trial showed that the effects of T3(X, mole/kg feeds) on body weight gain(Y1,g) and feed consumption(Y2,g) were Y1=310-21.5X (R2=0.868; P=0.0001) and Y2=398-22.3X (R2=0.765; P=0.0001), respectively. The feed conversion ratio, the weight of liver, the weights of various intestinal segments, the length of duodenum , the gizzard weight % of feed-deprived body weight (FDBW), the duodenal length of per Kg FDBW, the jejunal length, the ileal length, and the weight per cm jejunal length all had similar linear responses. However, the effect of dietary T3 supplementation (X, mole/Kg diet) on the heart weight (Y4, g) was Y4=2.58+0.98X-0.17 X2 (R2=0.526; P<0.01). The weight of pancreas, the weight of gizzard, and the heart weight % of FDBW or the pancreas weight % of FDBW all had similar second order curve response. The regression of the heart weight % of FDBW (Z1, %) on dietary Dopa supplementation (X1, mole/Kg diet) was Z1=0.64+0.24 X1-0.23 X12+0.05 X13 (R2=0.868; P<0.0379).
The objective of the second experiment was to understand the effects of T3 or Dopa supplement in diet of 6-12 day-old broiler chicks on their small intestinal oxygen consumption and their sodium pump(Na+, K+-ATPase) oxygen consumption percentage in the small intestine. One hundred and twenty six-day-old broiler chicks, after body weight measured, were randomly allotted into 5 treatments, namely, dietary supplementation of 0.7, and 2.4mole Dopa/(Kg diet), or 1.9, and 3.8mole T3/(Kg diet) as well as a control that was not supplemented. They were replicated four times. At age of 12 days, three chicks randomly taken from each treatment were pooled in a group and fed with commercial chicken feeds until 48 day-old. The results showed the effect of dietary T3 supplement (X, mole/Kg diet) on duodenal oxygen consumption (Y14, mole O2 min-1g-1) was that Y14=2.64+0.33X (R2=0.164; P=0.0144). Both the jejunal oxygen consumption, and the jejunal sodium pump oxygen consumption percentage had the similar linear response. The feed conversion ration, the body weight gain, the gizzard weight, the lengths of various intestinal segments, the jejunal weight, the gizzard weight % of FDBW, the ileal density (mg/mm2), the length and weight of the caeca, and the length and weight of small intestine all decreased as the dietary supplement of T3 increased. However, the effect of dietary supplement of T3 (X, mole/Kg diet) on abdominal fat pad weight (Y17, g) was that Y17=2.12+1.26X-0.20X2 (R2=0.789; P=0.0001). The pancreas weight, the thyroid weight, the ileal weight, the thyroid weight % of FDBW, and the abdominal fat pad weight % of FDBW all had similar second order curvilinear response. The partial correlation analysis showed that the weight and the length of the small intestine negatively correlated with body weight gain, and the oxygen consumption of the various small intestinal segments had negative correlation with their respective densities (mg/mm2). When T3 was supplemented in the diet of 6-12 day-old chicks, the abdominal fat pad weight and the thyroid weight % of FDBW were lowered (P<0.001). This implied that T3 enhanced energy metabolism, which in turn caused decrease in abdominal fat, and thyroid gland shrunk was due to its feedback inhibition. Diet supplemented with T3 for 6-12 day-old broiler chicks made no significant influences on either the abdominal fat pad weight % or the thyroid weight % of FDBW when they were 50 day-old. Supplement of 0.7, and 2.4mole Dopa/(Kg diet) or 1.9, and 3.8mole T3/(Kg diet) to the diet for 14 days broiler chicks had no influence on their small intestinal oxygen consumption. After corrected by FDBW, the small intestinal oxygen consumption at age of 14 days in the treatments mentioned previously, however, increased 28.0, 16.3, 21.6, and 43.2%, respectively. Supplement of 1.9, or 3.8mole T3/(Kg diet) in diet during 6-12 day-old decreased the body weight gain of the birds by 13.6 and 20.3%, respectively. The breast muscle weight measured at age of 14 days also decreased 16.5 and 11.1% by the same T3 treatments. Whereas, the breast muscle weight at age of 14 days was decreased 3.6 and 4.8% by dietary supplement of 0.7, and 2.4mole Dopa, respectively. （Key Words: Broiler Chicks,Triiodothyronine, Dopamine, Small Intestinal Energy Metabolism ）
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