Feeding low-quality date leaves as a substitute to conventional forages in dairy cows diet: effects on digestibility, feeding behavior, milk yield, and feed efficiency.

This study investigated the possibility of integrating date leaves (DL) as a partial or complete substitute for conventional forage fibre sources into the diet of dairy cows. Nine Holstein cows were assigned to a replicated 3×3 Latin square design, and offered 1 of the 3 diets containing no DL (DL-0), or finely chopped DL partially (50%, DL-50) or completely (100%, DL-100) substituted for lucerne hay and maize silage. The replacement of the forages by DL was established such that the forage NDF (24.5%) was similar across diet despite the decreased forage: concentrate ratio from 0.45:0.55 to 0.33:0.67. Diets were similar in concentration of crude protein and starch, while the indigestible forage NDF (iNDF) increased from 7.2 to 15.4% of DM. Results showed that increasing DL inclusion linearly decreased nutrient intake and digestibility. Moreover, a trend toward a linear decrease in milk yield and percentage of milk protein and lactose were observed with increasing DL proportion in the diet. However, ruminal volatile fatty acids concentration, milk fat content, and feed efficiency were similar across the treatments. A quadratic trend was observed for eating and ruminating time by feeding DL, with the highest values found for cows fed DL-50. Replacing forages with finely chopped DL was effective to meet the fibre requirement, but reduced feed intake and milk yield possibly because of increased forage iNDF. However, conventional forages can be partially replaced with DL in the diet, particularly under forage shortage, because of maintained gross milk yield efficiency and reduced feed cost.