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Serum protein - bound iodine levels in growing and pregnant sheep Lee, Winston Keh Chin

Abstract

Changes in serum protein-bound iodine (PBI) levels were estimated in pregnant and non-pregnant mature ewes during the months from August to March. The PBI levels in ewes appeared to be elevated by low temperature (P < 0.001) and depressed by high temperature. The estrous cycle affected the PBI levels in ewes. The peak of PBI level was within 48 hours of estrus period. Breed differences played an important part on PBI levels; the Dorset breed generally had a higher PBI level than the Suffolk crossbred animal. The PBI levels in pregnant ewes became significantly higher (P < 0.05) than in the control after the third week of pregnancy. This increase in PBI level was followed by a significant increase (P < 0.05) in body weight gain at the seventh week of pregnancy. Toward the end of pregnancy (last seven weeks) the ewes with twin lambs had a significantly higher PBI level than the ewes with single lambs. The higher PBI levels remain elevated after parturition until the end of the lactation period. The PBI levels of lambs implanted with 3 and 6 mg diethystilbestroi (DES) were determined. Female lambs had a higher PBI level than mature ewes. Ten days after DES implantation, a significant (P < 0.001) increase in PBI levels was observed. This was followed by an increase in body weight gain over the control of 35% and 37% for 3 and 6 mg DES implants respectively during the remaining part of the experiment. There was a difference in the response to DES treatment between sexes. The wethers grew faster than the female lambs; this difference in growth rate can be reduced by treating the ewes with a larger dose of DES. Iodinated casein (protamone trade name, 1% thyroid activity) fed at 0, 0.25, 0.5 and 1 gm and also in combination with 1.75 mg DES were fed daily to growing lambs. The results showed that Protamone feeding to lambs as well as in combination with DES, caused a significant increase in PBI levels over the controls (P < 0.001). Blood glucose measurements showed a parallel with PBI in fluctuation. The blood sugar levels of lambs were found to be higher than those of mature ewes. DES and Protamone feeding caused an increase rate of gain over the control (DES 13.2 lb; 0.25 gm Protamone 8.7 lb)and improved feed efficiency (DES 1:3.4; Protamone 1:3.9 and control 1:5.6).

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