[Nutrient digestibility and nitrogen utilization in lactating cows under restricted protein supply and subsequent...

Area of Science:

• Animal Nutrition
• Ruminant Physiology
• Metabolic Studies

Background:

• Dietary protein is crucial for dairy cow health and productivity.
• Understanding the impact of protein deficiency and subsequent recovery is vital for optimizing feeding strategies.

Purpose of the Study:

• To investigate the effects of a short-term crude protein deficiency on nutrient digestibility and nitrogen metabolism in dairy cows.
• To determine if residual effects on nutrient utilization and nitrogen balance persist after realimentation.

Main Methods:

• Four pairs of monozygotic twin cows were subjected to a 17% crude protein deficiency for four weeks.
• Nutrient digestibility and nitrogen balance parameters were measured during deficiency and subsequent realimentation periods.
• Milk yield and composition were monitored to assess performance impacts.

Main Results:

• Protein restriction significantly decreased apparent digestibility of dry matter, organic matter, N-free extracts, crude fiber, and nitrogen.
• Urine nitrogen excretion was reduced by 47%, leading to a 14% decrease in total nitrogen retention.
• Feed nitrogen utilization for milk nitrogen was slightly higher during protein deficiency.
• No significant residual effects on nutrient digestibility or nitrogen balance were found after realimentation.
• A persistent 6% reduction in milk yield was observed, unexplained by changes in digestibility or nitrogen balance.

Conclusions:

• Short-term crude protein deficiency negatively impacts nutrient digestibility and nitrogen utilization in dairy cows.
• While short-term deficiency does not appear to cause lasting changes in digestibility or nitrogen balance, a persistent reduction in milk yield warrants further investigation.