Extrusion of whole cottonseed enhances nutrient utilization, rumen fermentation, and circulating metabolites and amino acid profiles in heat-stressed lactating Holstein cows

This study aimed to evaluate the effects of feeding extruded whole cottonseed (EWC) on performance, nutrient digestibility, feeding behavior, ruminal fermentation characteristics, metabolic responses, and amino acid profiles in dairy cows under heat stress condition. Thirty-two multiparous cows (104 ± 14.5 days in milk; mean ± SD) were used in a completely randomized design and assigned to two dietary treatments: a control treatment containing raw whole cottonseed (RWC) and a treatment diet containing EWC. Mean temperature-humidity index (THI) during the experiment was 75.9 ± 1.01, representing moderate, sustained heat stress throughout the study period. There was a treatment × time interaction for DMI, with cows fed EWC showed higher DMI from days 8 to 21. Cows fed EWC produced more milk with greater concentrations of protein, lactose, and solids-not-fat, whereas milk fat percentage decreased. The yields of energy-corrected and fat-corrected milk per DMI, feeding and resting behaviors did not differ between groups. Rumen acetate concentration was lower, whereas propionate concentration tended to higher in EWC-fed cows. Apparent total-tract digestibility of DM was greater and CP digestibility tended to be greater in cows fed EWC, whereas NDF digestibility did not differ. Cows fed EWC exhibited higher blood concentrations of cholesterol and albumin, as well as an increased albumin-to-globulin ratio, while showing a tendency for reduced alkaline phosphatase activity compared with those fed RWC. Furthermore, EWC-fed cows had higher plasma concentrations of glycine, trends for higher arginine, and urea-cycle-related amino acids (AA) including citrulline and ornithine, compared with cows receiving RWC. These findings indicate that inclusion of EWC was associated with greater milk yield and improved milk protein and lactose concentrations, coinciding with enhanced nutrient digestibility and altered ruminal fermentation patterns in cows exposed to moderate heat stress.