80
The effects of maternal energy restriction during mid-gestation on growth performance, gene expression, and immune function in the resultant beef offspring
Fetal or developmental programming evaluates the effects of maternal alterations on the developing fetus and the potential adverse effects later in life. To understand these potential consequences in beef cattle the objectives of this research were to determine the effects of maternal nutrient restriction during mid-gestation on offspring growth performance, subcutaneous adipose tissue gene expression, and the humoral immune response in the resultant beef offspring. Pregnant beef cows (84 ± 11 d of gestation, 4 ± 1 yr, 495 ± 58 kg, 4.9 ± 0.5 BCS) were allotted to one of two dietary treatments: 1) Control (n = 76) fed to achieve and/or maintain BCS 5.0-5.5; or 2) Restricted (n = 75) fed to lose 1 BCS over the ensuing 91 d treatment period of mid-gestation. Following treatment cows were commingled and managed as a common group through weaning. Cow data was analyzed using PROC GLM (SAS). Progeny data were analyzed as a completely randomized design using PROC GLM and Repeated Measures in PROC MIXED (SAS) for growth performance and immune response, respectively. Fold differences in progeny gene expression were determined using Relative Expression Software Tool (REST). A subsample of weaned calves was used to measure humoral immune response. Two additional subsamples were sampled at weaning and harvest to evaluate gene expression. Control cows maintained or gained condition where Restricted cows lost condition (P<0.05) during the mid-gestation treatment period. Mid-gestation treatment did not affect (P>0.05) birth weight, weaning weight, or adjusted 205-d weaning weight of progeny. Expected gender differences occurred with steers having heavier (P<0.05) birth weights, weaning weights, and adjusted 205-d weaning weights compared to heifers. No differences (P>0.05) were observed between treatments during the feeding period on live cattle performance variables including ADG, DMI and G:F. No differences were detected (P>0.05) in subcutaneous adipose tissue gene expression in the weaning or final subsample. Calves from Restricted cows had lower antibody titers (P<0.05) in response to a novel antigen during the receiving period. These results suggest a mild loss in body condition encountered by a cow during mid-gestation will not affect adipose differentiation or growth throughout the post-natal period in beef cattle offspring. However, these conditions imposed on the cow during mid-gestation may have an adverse impact on antibody production during the receiving period in the resultant calf.
Keywords: Fetal programming, cattle, growth