Influence of nutrient intake and body fat on concentrations of insulin-like growth factor-I, insulin, thyroxine, and leptin in plasma of gestating beef cows.
Pregnant Angus x Hereford cows (n = 73) were used to determine the effects of amount of nutrient intake and BCS on concentrations of IGF-I, insulin, leptin, and thyroxine in plasma. At 2 to 4 mo of gestation, cows were blocked by BCS and assigned to one of four nutritional treatments: high (H = a 50% concentrate diet fed ad libitum in a drylot) or adequate native grass pastures and one of three amounts of a 40% CP supplement each day (M = moderate, 1.6 kg; L = low, 1.1 kg; or VL = very low, 0.5 kg; as-fed basis). After 110 d of treatment, all cows grazed dormant native grass pasture and received 1.6 kg/d of a 40% CP supplement. At 68, 109, and 123 d of treatment, cows were gathered, and plasma samples were collected by tail venipuncture (fed sample). After 18 h without feed and water, a second plasma sample was collected (fasted sample). At 109 d of treatment, BCS was greatest (P < 0.05) for H cows, similar for M and L cows, and least for VL cows. Concentrations of insulin and leptin were greater (P < 0.05) for H cows than for M and VL cows at 68 and 109 d, but similar for all groups at 123 d. Thyroxine in plasma was greatest (P < 0.05) for H cows at 68 d and similar for cows on all treatments at 123 d. Concentrations of IGF-I, insulin, and leptin in fed and fasted cows were positively correlated with BCS at 109 d. Body condition was predictive of concentrations of IGF-I, insulin, and leptin when cows had different nutrient intakes, but BCS accounted for less than 12% of the variation in plasma concentrations of IGF-I, insulin, and leptin when nutrient intake was the same for all cows. We conclude that amount of nutrient intake has a greater influence than body energy reserves on IGF-I, insulin, and leptin concentrations in the plasma of gestating beef cows.
Lents
C A
CA
Department of Animal Science, Oklahoma Agricultural Experiment Station, Stillwater 74078, USA.
Wettemann
R P
RP
White
F J
FJ
Rubio
I
I
Ciccioli
N H
NH
Spicer
L J
LJ
Keisler
D H
DH
Payton
M E
ME
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D050218:Body Fat Distribution / Q000662:veterinary*; D002417:Cattle / Q000097:blood / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D019587:Dietary Supplements; D004435:Eating / Q000502:physiology; D005260:Female; D007328:Insulin / Q000097:blood / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000502:physiology; D016018:Least-Squares Analysis; D020738:Leptin / Q000097:blood / Q000502:physiology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood / Q000502:physiology*; D012044:Regression Analysis; D013223:Statistics as Topic; D013974:Thyroxine / Q000097:blood / Q000502:physiology; D013997:Time Factors
D007328:Insulin; D020738:Leptin; D007334:Insulin-Like Growth Factor I; D013974:Thyroxine