Endocrine and metabolic changes during altered growth rates in beef cattle

Area of Science:

• Animal Science
• Ruminant Nutrition
• Metabolic Physiology

Background:

• Dietary intake significantly impacts growth performance and metabolic profiles in livestock.
• Understanding the physiological responses to feed restriction and subsequent realimentation is crucial for optimizing animal production.

Purpose of the Study:

• To investigate the effects of feed restriction and realimentation on key metabolic indicators in growing steers.
• To assess changes in hormones and metabolites related to growth and nutrient utilization.

Main Methods:

• Two groups of steers were used: one fed ad libitum (control) and another subjected to feed restriction followed by ad libitum feeding.
• Blood samples were collected during different growth phases and analyzed for growth hormone (GH), insulin-like growth factor-I (IGF-I), triiodothyronine (T3), thyroxine (T4), glucose (GLU), nonesterified fatty acids (NEFA), and blood urea nitrogen (BUN).

Main Results:

• Restricted steers showed elevated GH and decreased IGF-I, T4, and GLU compared to controls.
• During realimentation, GLU, IGF-I, T4, and BUN levels increased.
• Blood urea nitrogen decreased during early realimentation, indicating enhanced nitrogen utilization efficiency for protein synthesis.
• IGF-I levels surpassed control levels during realimentation and remained elevated at the final weight.

Conclusions:

• Feed restriction alters key hormonal and metabolic profiles in steers.
• Realimentation leads to a rapid recovery of metabolic status, with enhanced nitrogen utilization and sustained higher IGF-I levels.
• These findings suggest improved protein synthesis efficiency following a period of feed restriction and realimentation.