Characterizing inter-individual responses of dairy cows to concentrate reduction

Background and objectives In dairy systems, concentrate allocation is commonly based on milk yield, days in milk and parity, assuming homogeneous responses among cows with similar characteristics. We hypothesized that cows differ in their short-term adaptive strategies when concentrate supply is reduced. The objective was to characterize inter-individual variability in milk yield and feed intake responses following a decrease in concentrate allowance. Data collection Sixty Holstein cows (one-third primiparous) were fed a common balanced base ration delivered individually via electronic weighing troughs and received concentrate through an automatic feeder. Each 6-week sequence comprised 3 weeks at 4 kg/d concentrate ( C4 phase ) followed by 3 weeks at 1 kg/d ( C1 phase ); the sequence was repeated three times. Cows were assigned to one of two treatments: FLEX (ad libitum access to the base ration) or FIX (base ration intake during C1 limited to the individual average intake recorded during the preceding C4 phase). Research methods Individual response profiles were defined using predefined quantitative thresholds established by an expert group. Compensation in base ration intake was expressed as kg additional base ration per kg concentrate reduction and classified as B0 (<0.30), B+ (0.30 ≤ B+ ≤ 0.80), or B++ (>0.80). Milk yield response was expressed as kg milk change per kg concentrate reduction and classified as M0 (>−0.30), M− (−0.80 ≤ M- ≤ −0.30), or M−− (<−0.80). Results With an average decrease of 2.40 kg DM/d concentrate supply, FLEX cows increased base ration intake by 1.35 kg DM/d and decreased milk yield by 1.24 kg/d while FIX cows maintained base ration intake (-0.08 kg DM/d) and decreased milk yield by 2.43 kg/d. Milk response profiles were equally distributed in FLEX cows whereas most FIX cows exhibited moderate to high milk losses. Marked variability was observed in both intake compensation and milk responses within treatments. Contributions Access to base ration modulates milk response to concentrate reduction and provides evidence of substantial inter-individual variability in short-term adaptive strategies. By proposing quantitative response profiles combining intake and milk changes, it contributes a phenotyping framework for identifying response profiles that could eventually support the development of individualized feeding approaches.