Effect of stage of pregnancy, maternal feeding level and fetal sex on fetal gut length in Holstein×Zebu cows*

Abstract Text: Lower gut development at birth is suggested as one hypothesis for explain the lower development during the whole life of calves from cows that were low fed throughout gestation. These calves can have lower absorption of immunoglobulin right after birth and consequently lower immune capacity and be more susceptible to diseases that can impair the normal development. Forty-one nonlactating multiparous Holstein×Gyr cows, pregnant from the same Gyr bull, were used in an experiment to assess the effect of stage of pregnancy, maternal feeding level and fetal sex on fetal gut length. Cows were fed either HIGH (ad libitum, n=18) or LOW(DMI restricted to 1.15% of BW in DM basis, n=23) feeding level of the same diet (93% corn silage and 7% concentrate). Fetal sex was confirmed by ultrasonography at 55 days of gestation. Cows were separated at random into four groups, which were harvested at 100, 200, 240 and 270 days of gestation (n = 4/5, 5/6, 5/6 and 4/6 for HIGH/LOW fed cows at 100, 200, 240 and 270 days, respectively) with at least two cows gestating same sex fetuses being harvested at each time. At harvest, fetuses were collected and dissected and gut was emptied and separated into small and large intestine, which were measured. Data were analyzed in a 2×2×4 factorial with two feeding level, two fetal sex and four stages of pregnancy. There were no significant interactions (P>0.19) among feeding level, fetal sex and days of pregnancy on gut length. Small intestine and total gut length were not affected by feeding level (P=0.86 and 0.75, respectively) and fetal sex (P=0.87 and 0.71, respectively). Large intestine was longer (P=0.049) in female (134.9 cm) than in male fetuses (123.4 cm) but was not affected by feeding level (P=0.16). Fetal small and large intestine and total gut length increased (P<0.001) as the pregnancy age increased but were not different between 240 and 270 days of gestation (P=0.64, 0.78 and 0.62, respectively). The average fetal gut length was 431, 976, 1272 and 1361 cm at 100, 200, 240 and 270 days of gestation, respectively. The results suggest that female fetuses have longer large intestine than male fetuses, although the explanation for this finding is still inconclusive and requires further studies.

*Funded by INCT-CA, CNPq and FAPEMIG.

Keywords: fetal programming, gut development, maternal nutrition