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 express 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. Due to a limited number of observations in late lactation, LFI data from days 19 to 22 were not included. 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 1–5 (C1) and day 6–18 (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 purebred and F1 sows. Parity group 1 in both purebred and F1 sows had the lowest ARC and ADI metrics, but highest VAR (P<0.05) in each period of lactation. Similar differences were observed for seasonal effects (P<0.05) as LFI curves during summer months represented lower ARC and ADI and higher VAR values compared to all other seasons. For all breeds, increased 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 and shorter wean-to-first service intervals (P<0.05). Average rate of change increased more quickly in early periods (PB1, PB2, C1) and was lower in late lactation (PB3, C2). An increase in average rate of change in intake, average daily intake, and decreased variation from predicted LFI values during a period of lactation resulted in improved measures of maternal performance.
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