Changes in heat production by mature cows after changes in feeding level

Area of Science:

• Animal Science
• Nutritional Physiology
• Metabolic Regulation

Background:

• Feed restriction impacts an animal's metabolic rate and heat production.
• Understanding realimentation dynamics is crucial for optimizing livestock production and welfare.
• Previous studies suggest adaptation periods can be lengthy and influenced by feeding levels.

Purpose of the Study:

• To quantify changes in heat production in cows after a period of feed restriction.
• To determine the effect of varying realimentation feeding levels on the dynamics of heat production.
• To investigate the time course of metabolic adaptation to refeeding in cattle.

Main Methods:

• Forty 4-year-old cows were subjected to feed restriction (50.0 g DM/MBS) for 91 days, with heat production measured periodically.
• Following restriction, cows were realimented at four different levels (50.0 to 75.5 g DM/MBS) for 175 days, with ongoing heat production measurements.
• A final phase involved realimenting all cows to the highest level (75.5 g DM/MBS) to assess recovery, with heat production measured over 112 days.

Main Results:

• Heat production decreased rapidly within the first 7 days of feed restriction and continued to decline over 91 days.
• Upon realimentation, heat production increased rapidly within 7 days, with sustained adaptation observed in cows fed higher levels (T75.5 and T67.0).
• Heat production scaled for metabolic body size showed a tendency to differ among treatments (P = 0.11), with daily heat production increasing by 2.5 kcal/d.

Conclusions:

• There is no significant lag in heat production during the realimentation phase in cows.
• Increased recovered energy during realimentation is closely linked to a rapid elevation in heat production.
• The level of realimentation influences the duration and extent of metabolic adaptation in heat production following feed restriction.