Dietary guanidinoacetic acid as arginine spare molecule for beef cows at late gestation: Effects on cow’s performance and metabolism, and offspring growth and development

We aimed to assess whether guanidinoacetic acid (GAA) affects the performance, metabolism, and placental vascularization of pregnant beef cows during late gestation as well as its impact on the offspring’s performance. Twenty-eight pregnant Brahman cows, averaging 532±15.1 kg and carrying male (n=15) and female (n=13) fetuses, were used. The basal diet consisted of 688 g/kg corn silage, 147 g/kg sugarcane bagasse, 47.7 g/kg corn, 89.6 g/kg soybean meal, 6.86 g/kg urea, and 21.2 g/kg mineral mixture (DM basis). Cows were fed the experimental diets from 180 to 270 days of gestation. The following treatments were evaluated: control (no addition of GAA) or addition of 0.2 % GAA to the total diet (DM basis). There was no effect (P≥0.37) of GAA on voluntary intake. Similarly, GAA addition did not affect (P≥0.54) cows performance variables, except for ribeye area (REA), which had a lower (P<0.01) variation compared to the initial REA in cows fed dietary GAA compared to the control group. Dietary GAA increased (P≤0.02) both serum nitric oxide and placental vascularization compared to cows fed the control diet. There was no effect (P≥0.43) of GAA on urine and serum creatine concentrations. In contrast, dietary GAA increased (P≤0.03) plasma concentration of arginine, ornithine, citrulline, and tyrosine compared to the control. Conversely, dietary GAA decreased (P<0.02) plasma methionine concentration. Dietary GAA increased AGAT activity (P<0.03) in the liver, with no differences observed (P>0.68) on GAMT activity. There was no effect (P≥0.15) of GAA on performance of the offspring. Addition of GAA in maternal diet did not affect skeletal muscle fiber number (P>0.09) and diameter (P>0.23) of the offspring. Guanidinoacetic acid decreases skeletal muscle mobilization and enhances placental vascularization of beef cows during late gestation. However, providing GAA seems to not affect the performance of the offspring.