Abstract
Daily feed intake during lactation was recorded on purebred Yorkshire (n = 1587), Landrace (n = 2197), and F1 Yorkshire x Landrace (n = 6932) litters from day 1 to 22 of lactation. Lactation feed intake (LFI) curves were predicted using a mixed model which included fixed effects of breed, season, parity group (PG), day of lactation, interactions of day with breed and PG, and a covariate for litter size after cross-fostering. Random effects included litter, contemporary group (herd-year-month), dam, and sire nested within breed. Least squares means for each day were used to define LFI curves by breed through day 22 of lactation. Yorkshire and Landrace LFI curves were not different (P = 0.09), though both differed from the LFI curve (P < 0.05) of F1 sows. Evaluation of the difference in feed intake between 2 consecutive days (DC) of lactation resulted in the following classifications: 3 periods for purebreds, day 1 to 6 (PB1), day 7 to 10 (PB2), and day 11 to 18 (PB3); 2 periods for F1 sows, day 1 to 5 (C1) and day 6 to 18 (C2). Average rate of change in intake (ARC), average daily intake (ADI), and variation from predicted LFI values (VAR) metrics were estimated for each period in both purebred and F1 sows. The lowest ARC and ADI metrics, but highest VAR (P < 0.05) in each period of lactation occurred in PG 1 sows and during the summer. An increase in ARC and ADI metrics resulted in higher 21-day litter weaning weights (P < 0.05), while decreasing VAR metrics late in lactation (PB3 and C2) resulted in higher 21-day litter weaning weights (LW21) and shorter wean-to-first-service intervals (P < 0.05). Heritability estimates for average daily lactation feed intake (ADFI), average rate of change (ARCT), and variation from predicted daily LFI values (VART) calculated over the entire lactation were 0.37, 0.24, and 0.16, respectively. Heritability estimates were variable across periods of lactation for ARC (0.03 – 0.17), ADI (0.09 – 0.36), and VAR (0.04 – 0.18)
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