Social interactions, feeding patterns, and feed efficiency of same- and mixed-parity groups of lactating cows

Social dynamics in group-housed animals can have important impacts on their welfare, feed efficiency, and production potential. Our objectives were to: 1) evaluate the effects of parity social grouping competition behavior, feeding patterns, 2) investigate cow-level relationships between production, efficiency. Fifty-nine Holstein cows (144.5 ± 21.8 starting DIM, mean SD) housed a freestall pen with 30 Roughage Intake Control (RIC) bins. We evaluated [primiparous (PR, n = 29) vs. multiparous (MU, 30)] group composition at bunk [same-parity (SM, 39) mixed-parity (MX, 20, 50% each parity)] 2 × factorial design (SM-MU: 20; SM-PR: 19; MX-MU: 10; MX-PR: 10) Within pen, groups 9 to 10 considered subgroups assigned treatments defined by sets 5 bins (2:1 stocking density). Feed patterns recorded via continuous video first hour after morning delivery 24-h RIC data, respectively. Residual intake (RFI) was calculated as difference predicted observed dry matter (DMI) accounting for known energy sinks. Linear models used interactions competition, Within-cow correlations performed RFI. Cows MX, compared SM, involved more competitive [mean (95% CI): contacts: 11.5 (8.1,16.3) 7.2 (5.5,9.3) events; displacements: 4.0 (3.0,5.3) 2.1 (1.7,2.7) events, replacements: 3.5 (2.6,4.7) 1.9 (1.5,2.5) events]. MX those SM had visits/meal [ 4.3 (3.9, 4.8) 3.7 (3.4, 3.9) visits/meal] longer meals (31.2 27.4 0.9 min/meal) tended higher RFI (0.41 0.3 −0.21 0.2) therefore less efficient. Multiparous PR greater DMI per day (29.3 0.6 25.5 0.4 kg/d) meal [4.2 (4.0, 4.4) 3.4 (3.2, 3.6) kg/meal], faster eating rates [0.14 (0.13, 0.15) 0.12 (0.11, 0.13) kg/min], fewer visits/d [26.6 (24.0, 29.4) 32.8 (29.7, 35.9)]. Regardless or parity, shorter latencies visit be Overall, individual cow- group-level among efficiency play an role dynamics. At 2:1 density, lactating may potentially negative animal welfare implications that should when selecting strategies farm.