The effects of late gestation nutrient restriction of dams on beef heifer intake, metabolites and hormones during an ad libitum feeding trial.

This study's objective was to determine if nutrient restriction during late gestation affected beef heifer feed intake, body weight (BW) gain and endocrine regulation during a 10-week feeding trial. During the last 100 days of gestation, control (CON) dams were fed to increase body condition score (BCS). Whereas, nutrient-restricted dams (NR) and NR dams protein supplemented 3 days/week (NRS) were fed to decrease BCS by 1.2. After parturition, all cow-calf pairs were moved to a common pasture and fed in excess of requirements until weaning. At 15 months of age, heifers were randomly sorted into two pens and adjusted to a commercial total mixed ration over a 2-week period. Blood samples and BW were taken at the initiation of feeding and on a biweekly basis for the duration of the feeding trial. Feed intake was monitored for 10 weeks using a GrowSafe System. After 10 weeks, an intravenous glucose tolerance test (IVGTT) was performed on 21 randomly subsampled heifers. During the feeding trial, NR heifers consumed more feed than CON and NRS heifers. Heifers from NR dams tended to increase BW compared to NRS and CON heifers when adjusted for initial BW. Heifers from NR and NRS dams had a greater increase in BCS compared to heifers from CON dams. Plasma glucose and insulin concentrations during the feeding trial increased in NR heifers compared to the other groups beginning at 2 and 4 weeks respectively. Plasma leptin concentrations were increased in the NR and NRS heifers compared to the CON heifers beginning at week 4 of feeding. During the IVGTT at the conclusion of the feeding challenge, plasma glucose and insulin were increased in NR heifers compared to other treatment groups. These results show that nutrient restriction during late gestation alters appetite and endocrine regulation in heifer offspring.