303. NUTRIENT INTAKE OF BOS INDICUS HEIFERS DURING EARLY AND MID-GESTATION CAUSES CHANGES TO PLASMA CONCENTRATIONS OF TRIIODOTHYRONINE (T3) AND THYROXINE (T4) OF THEIR PROGENY

Abstract

Fetal and postnatal growth are mediated by thyroid hormones (TH). Maternal nutrient intake during gestation can program postnatal TH concentrations. This may have significant economic implications for beef cattle production. We investigated the effect of feeding beef heifers high (H = 240%) and low (L = 70%) levels of recommended daily crude protein intake during the first and second trimesters of gestation in a two-by-two factorial design on progeny (n = 68) plasma concentrations of free and total triiodothyronine (FT3 and TT3) and free and total thyroxine (FT4 and TT4) from birth until weaning at 6 mo of age. Exposure to low compared to high protein diets during the second trimester resulted in increased plasma FT3 concentrations relative to TT3 (P = 0.04) at birth. For male progeny, exposure to low compared to high protein diets during the first trimester resulted in greater plasma FT4 concentrations from birth until weaning (P = 0.02). Also for males from birth until weaning, LH had greater plasma TT3 concentrations than HH (P < 0.01). For female progeny, HH had greater plasma TT3 concentrations relative to TT4 than HL from birth until weaning (P = 0.03). Plasma concentrations of FT3 were positively associated with average daily gain relative to birth weight at 1 (r = 0.41; P < 0.01) and 3 mo FT3 (r = 0.41; P < 0.01). Heifer protein intake during the first and second trimesters of gestation has a permanent effect to progeny plasma TH concentrations and these changes are associated with the postnatal growth pathway.

(1) Micke GC, Sullivan TM, Magalhaes RJS, Rolls PJ, Norman ST, Perry VEA. Heifer nutrition during early- and mid-pregnancy alters fetal growth trajectory and birth weight. Anim Reprod Sci. 2010; 117: 1–10.