Nutritional efficiency of feed-restricted F1 Holstein/Zebu cows during the middle third of lactation.

OBJECTIVE

The objective of this study was to evaluate the effects of different levels of quantitative feed restriction on nutrient intake and digestibility, nitrogen balance, efficiency and feeding behavior, and productive performance in F1 Holstein/Zebu cows during the middle third of their lactation.

METHODS

Sixty F1 Holstein/Zebu cows with 111.5 ± 11.75 days of lactation and an initial body weight (BW) of 499 ± 30 kg (mean ± SEM) were used. The experimental design was completely randomized with the following diet levels of feed restriction: 3.39%, 2.75%, 2.50%, 2.25% and 2.00% of BW, with 12 replications for each level.The experiment lasted for 63 days, of which each period lasted 21 days with the first 16 days for diet adaptation followed by 5 days for collection of data and samples.

RESULTS

For each 1% of BW diet restriction, there was a decrease in dry matter intake of 5.26 kg/day (p <0.01). There was no difference in daily milk production (p = 0.09) under the restriction levels of 3.39% to 2.0% of BW. When corrected for 3.5% fat, milk production declined (p = 0.05) 3.46 kg/day for each percentage unit of feed restriction.

CONCLUSION

Restricting the feed supply for F1 Holstein/Zebu cows in the middle third of their lactation period altered nutrient intake, nitrogen balance and ingestive behavior but did not affect milk production or feed efficiency. However, considering the observed body weight loss and decrease in milk production corrected for 3.5% fat, restriction of no less than 2.5% BW is recommended.