Postnatal development of the ovine uterus primarily involves uterine gland morphogenesis or adeno... more Postnatal development of the ovine uterus primarily involves uterine gland morphogenesis or adenogenesis. Adenogenesis involves the budding differentiation of the glandular epithelium (GE) from the luminal epithelium (LE) and then GE proliferation and coiling/branching morphogenetic development within the stroma between birth (postnatal day or PND 0) and PND 56. Insulin-like growth factor (IGF)-I and IGF-II mRNAs were previously found to be expressed only in the endometrial stroma, whereas the IGF receptor (IGF-1R) mRNA was most abundant in epithelia and in stroma, suggesting that an intrinsic IGF system regulates postnatal development of the uterus. Given that the biological activities of IGFs are modulated by a family of six IGF binding proteins (IGFBPs) and specific proteases, the objective was to determine the effects of age and estrogen disruption on expression of IGFs, IGFBPs and pregnancy-associated plasma protein A (PAPP-A or IGFBP-4 protease) in the ovine uterus. In Study O...
Angus bulls and heifers from lines divergently selected for serum IGF-I concentration were used t... more Angus bulls and heifers from lines divergently selected for serum IGF-I concentration were used to evaluate the effects of IGF-I selection line on growth performance and feed efficiency in 2 studies. In study 1, bulls (low line, n = 9; high line, n = 8; initial BW = 367.1 ± 22.9 kg) and heifers (low line, n = 9; high line, n = 13; initial BW = 286.4 ± 28.6 kg) were adapted to a roughage-based diet (ME = 1.95 Mcal/kg of DM) for 24 d and fed individually for 77 d by using Calan gate feeders. In study 2, bulls (low line, n = 15; high line, n = 12; initial BW = 297.5 ± 34.4 kg) and heifers (low line, n = 9; high line, n = 20; initial BW = 256.0 ± 25.1 kg) were adapted to a grain-based diet (ME = 2.85 Mcal/kg of DM) for 32 d and fed individually for 70 d by using Calan gate feeders. Blood samples were collected at weaning and at the start and end of each study, and serum IGF-I concentration was determined. Residual feed intake (RFI) was calculated, within study, as the residual from the linear regression of DMI on midtest BW 0.75 , ADG, sex, sex by midtest BW 0.75 and sex by ADG. In study 1, calves from the low IGF-I selection line had similar initial and final BW and ADG, compared with calves from the high IGF-I selection line. In addition, DMI and feed conversion ratio were similar between IGF-I selection lines; however, calves from the low IGF-I selection line tended (P < 0.10) to have lesser RFI than calves from the high IGF-I selection line (−0.26 vs. 0.24 ± 0.31 kg/d). In study 2, IGF-I selection line had no influence on performance or feed efficiency traits. However, there was a tendency (P = 0.15) for an IGF-I selection line × sex interaction for RFI. Bulls from the low IGF-I selection line had numerically lesser RFI than those from the high IGF-I selection line, whereas in heifers, the IGF-I selection line had no effect on RFI. In studies 1 and 2, weaning and initial IGF-I concentrations were not correlated with either feed conversion ratio or RFI. However, regression analysis revealed a sex × IGF-I concentration interaction for initial IGF-I concentration in study 1 and weaning IGF-I concentration in study 2 such that the regression coefficient was positive for bulls and negative for heifers. These data suggest that genetic selection for postweaning serum IGF-I concentration had a minimal effect on RFI in beef cattle.
To determine the effect of breed and estradiol-17f3 on selected hormones and metabolites, ovariec... more To determine the effect of breed and estradiol-17f3 on selected hormones and metabolites, ovariectomized (>13 mo) Angus (n = 14) and Brahman (n = 12) cows were paired by age and body weight and randomly assigned as either nonimplanted controls (CON) or implanted with estradiol (E2) for 45 d. After Day 7 and through Day 42, plasma concentration of somatotropin was greater for E2 than CON cows (treatment X day, P < 0.05). During an intensive blood sampling on Day 36, E2 cows tended (P < 0.10) to have greater somatotropin pulse amplitudes than CON cows, but other parameters of somatotropin release were not affected (P > 0.10) by E2 treatment. The effect of breed was apparent on Day 36 as Brahman cows had greater (P < 0.05) somatotropin pulse amplitude, basal secretion, and mean concentration than Angus cows. Overall, plasma concentration of IGF-I was greater (P < 0.01) for E2 than CON cows (158.3 vs. 104.2 ng/ml) and was greater for Brahman than Angus cows (164.1 vs. 98.4 ng/ml). However, there was a trend (P < 0.10) for a treatment × breed × day interaction for IGF-I (i.e., the magnitude of increase in IGF-I concentration was greater in E2-Angus than E2-Brahman cows). After Day 7 and through Day 42, total plasma IGF binding protein (IGFBP) activity was greater (P < 0.01) for E2 than CON cows. Ligand blotting revealed at least five forms of IGFBP activity, and E2 cows had greater (P < 0.05) binding activity of IGFBP-3 and the 30-and 32-kDa IGFBP than CON cows. Brahman cows had greater (P < 0.05) IGFBP-3 and the 32-kDa IGFBP than Angus cows. After Day 14 and through Day 42, concentration of urea nitrogen (PUN) was greater (P < 0.001) for CON than E2 cows (treatment × day, P < 0.001). Brahman had greater (P < 0.01) PUN than Angus cows (16.6 vs. 14.2 mg/dl). Plasma concentration of glucose was greater (P < 0.01) for E2 than CON cows (78.9 vs. 76.4 mg/dl) but was not affected (P > 0.10) by breed. In summary, these data suggest that some, but not all, of the positive effects of estradiol on peripheral concentration of IGF-I and IGFBP activity can be attributed to increased somatotropin. Moreover, breed influenced basal and E2-induced secretion of somatotropin and IGF-I such that differences between Brahman and Angus cows in plasma IGF-I concentrations were abated within 3 wk of estradiol implantation. Thus, breed influences the metabolite and hormonal response of cattle to estrogenic implants.
Postnatal development of the ovine uterus primarily involves uterine gland morphogenesis or adeno... more Postnatal development of the ovine uterus primarily involves uterine gland morphogenesis or adenogenesis. Adenogenesis involves the budding differentiation of the glandular epithelium (GE) from the luminal epithelium (LE) and then GE proliferation and coiling/branching morphogenetic development within the stroma between birth (postnatal day or PND 0) and PND 56. Insulin-like growth factor (IGF)-I and IGF-II mRNAs were previously found to be expressed only in the endometrial stroma, whereas the IGF receptor (IGF-1R) mRNA was most abundant in epithelia and in stroma, suggesting that an intrinsic IGF system regulates postnatal development of the uterus. Given that the biological activities of IGFs are modulated by a family of six IGF binding proteins (IGFBPs) and specific proteases, the objective was to determine the effects of age and estrogen disruption on expression of IGFs, IGFBPs and pregnancy-associated plasma protein A (PAPP-A or IGFBP-4 protease) in the ovine uterus. In Study O...
Angus bulls and heifers from lines divergently selected for serum IGF-I concentration were used t... more Angus bulls and heifers from lines divergently selected for serum IGF-I concentration were used to evaluate the effects of IGF-I selection line on growth performance and feed efficiency in 2 studies. In study 1, bulls (low line, n = 9; high line, n = 8; initial BW = 367.1 ± 22.9 kg) and heifers (low line, n = 9; high line, n = 13; initial BW = 286.4 ± 28.6 kg) were adapted to a roughage-based diet (ME = 1.95 Mcal/kg of DM) for 24 d and fed individually for 77 d by using Calan gate feeders. In study 2, bulls (low line, n = 15; high line, n = 12; initial BW = 297.5 ± 34.4 kg) and heifers (low line, n = 9; high line, n = 20; initial BW = 256.0 ± 25.1 kg) were adapted to a grain-based diet (ME = 2.85 Mcal/kg of DM) for 32 d and fed individually for 70 d by using Calan gate feeders. Blood samples were collected at weaning and at the start and end of each study, and serum IGF-I concentration was determined. Residual feed intake (RFI) was calculated, within study, as the residual from the linear regression of DMI on midtest BW 0.75 , ADG, sex, sex by midtest BW 0.75 and sex by ADG. In study 1, calves from the low IGF-I selection line had similar initial and final BW and ADG, compared with calves from the high IGF-I selection line. In addition, DMI and feed conversion ratio were similar between IGF-I selection lines; however, calves from the low IGF-I selection line tended (P < 0.10) to have lesser RFI than calves from the high IGF-I selection line (−0.26 vs. 0.24 ± 0.31 kg/d). In study 2, IGF-I selection line had no influence on performance or feed efficiency traits. However, there was a tendency (P = 0.15) for an IGF-I selection line × sex interaction for RFI. Bulls from the low IGF-I selection line had numerically lesser RFI than those from the high IGF-I selection line, whereas in heifers, the IGF-I selection line had no effect on RFI. In studies 1 and 2, weaning and initial IGF-I concentrations were not correlated with either feed conversion ratio or RFI. However, regression analysis revealed a sex × IGF-I concentration interaction for initial IGF-I concentration in study 1 and weaning IGF-I concentration in study 2 such that the regression coefficient was positive for bulls and negative for heifers. These data suggest that genetic selection for postweaning serum IGF-I concentration had a minimal effect on RFI in beef cattle.
To determine the effect of breed and estradiol-17f3 on selected hormones and metabolites, ovariec... more To determine the effect of breed and estradiol-17f3 on selected hormones and metabolites, ovariectomized (>13 mo) Angus (n = 14) and Brahman (n = 12) cows were paired by age and body weight and randomly assigned as either nonimplanted controls (CON) or implanted with estradiol (E2) for 45 d. After Day 7 and through Day 42, plasma concentration of somatotropin was greater for E2 than CON cows (treatment X day, P < 0.05). During an intensive blood sampling on Day 36, E2 cows tended (P < 0.10) to have greater somatotropin pulse amplitudes than CON cows, but other parameters of somatotropin release were not affected (P > 0.10) by E2 treatment. The effect of breed was apparent on Day 36 as Brahman cows had greater (P < 0.05) somatotropin pulse amplitude, basal secretion, and mean concentration than Angus cows. Overall, plasma concentration of IGF-I was greater (P < 0.01) for E2 than CON cows (158.3 vs. 104.2 ng/ml) and was greater for Brahman than Angus cows (164.1 vs. 98.4 ng/ml). However, there was a trend (P < 0.10) for a treatment × breed × day interaction for IGF-I (i.e., the magnitude of increase in IGF-I concentration was greater in E2-Angus than E2-Brahman cows). After Day 7 and through Day 42, total plasma IGF binding protein (IGFBP) activity was greater (P < 0.01) for E2 than CON cows. Ligand blotting revealed at least five forms of IGFBP activity, and E2 cows had greater (P < 0.05) binding activity of IGFBP-3 and the 30-and 32-kDa IGFBP than CON cows. Brahman cows had greater (P < 0.05) IGFBP-3 and the 32-kDa IGFBP than Angus cows. After Day 14 and through Day 42, concentration of urea nitrogen (PUN) was greater (P < 0.001) for CON than E2 cows (treatment × day, P < 0.001). Brahman had greater (P < 0.01) PUN than Angus cows (16.6 vs. 14.2 mg/dl). Plasma concentration of glucose was greater (P < 0.01) for E2 than CON cows (78.9 vs. 76.4 mg/dl) but was not affected (P > 0.10) by breed. In summary, these data suggest that some, but not all, of the positive effects of estradiol on peripheral concentration of IGF-I and IGFBP activity can be attributed to increased somatotropin. Moreover, breed influenced basal and E2-induced secretion of somatotropin and IGF-I such that differences between Brahman and Angus cows in plasma IGF-I concentrations were abated within 3 wk of estradiol implantation. Thus, breed influences the metabolite and hormonal response of cattle to estrogenic implants.
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