Particle size of wheat straw from genetically improved wheat affects the production performance and feeding behavior of Sahiwal cows.

The current study was designed to evaluate the effect of particle size (PS) and inclusion level of wheat straw (WS) obtained from genetically improved wheat on the performance and feeding behavior of Sahiwal cows. Twelve multiparous, mid-lactating Sahiwal cows (DIM 135 ± 25, mean ± SD; 12.8 ± 1.6 kg/d milk, 331 ± 21 kg of BW) were split into groups of 4 and subjected to each of four treatments in a 2*2 cross-over design. For experimental diets, TMR differed in the length and inclusion level of the WS component in that diet, (1) straw chopped with a 2 cm screen (Fine chopped- FC, and inclusion, i.e., FCA = 20% and FCB = 30%) or (2) straw chopped with a 4 cm screen (long chopped-LC, and inclusion, i.e., LCA = 20% and LCB = 30%). The increased dry matter (DM) intake (9.10 kg/d) and crude protein (CP) intake (1.25 kg/d) were observed in FCA. The diets with the shorter PS and higher inclusion (i.e., FCB) exhibited higher neutral detergent fibre (NDF) intake (3.77 kg) and acid detergent fibre (ADF) intake (2.72 kg). The findings of digestibility showed higher DM-digestibility in LCA (55.24%). Meanwhile, the higher digestibility of CP (52.9%) and ADF (36%) was found in LCB, and NDF (38.5%) was observed in LCA. Moreover, cows receiving FCA diets showed improved milk (15.5 kg/d), 3.5%FCM (17.76 kg/d), fat (0.683/d Kg), and protein (0.516 kg/d) yields and production efficiency. However, the milk composition was improved in cows fed with LCB diets. Furthermore, the behavioural activities showed higher eating (i.e., 228.3 min/day), rumination (391 min./day), and chewing (617.9 min./day) activities in LCB diets. Whereas, the lying activity (568.5 min/day) was greater in FCA-fed cows. Our study suggests that incorporating fine-chopped WS @ 20% improves the overall production performance and feeding behavior of the cows.