Early- and mid-lactation milk traits are associated with piglet growth during lactation

Preweaning piglet growth is tied to milk quality and consumption. To determine the relationship of milk traits from parity 1-4 dams and piglet growth, early- and mid-lactation (day 2 and day 16) milk samples were collected from 48 litters and analyzed for protein, fat, somatic cell count (SCC), lactose, other solids (solids excluding protein and fat), total solids, and milk urea nitrogen (MUN). There were no interactions of parity by day therefore only main effects were tested. Milk volume and percent MUN were greatest (P < 0.05) from fourth parity dams. Nulliparous dams had elevated (P < 0.05) SCC. Several milk traits were different by day. Percent milk protein, fat, and total solids were greater (P < 0.05) from day 2 milk, while percent milk lactose and other solids were greater (P < 0.05) from day 16 milk. Each milk trait was categorically identified as high, moderate, or low at 1/4, 1/2, or 1/4 distribution, respectively. Mixed models were used to determine the association of individual milk traits with piglet lactation growth (gain calculated from body weights at birth, day 10, and day 25 weaning; WN). Moderate levels of day 2 milk protein were associated with the greatest (P < 0.05) gain during lactation in comparison to low and high levels. High levels of day 2 milk lactose and day 2 other solids were both related (P < 0.05) to piglet gain over the lactation period. Evaluation of day 16 milk traits with piglet gain over lactation indicated high levels of fat, other solids, and total solids had the greatest (P < 0.05) gain in comparison to moderate and low levels of each trait. Within phase of lactation weight gain, association of day 2 or day 16 milk traits with early weight gain (birth to day 10) or late weight gain (day 10 to WN) were performed. The greatest (P < 0.05) early weight gains were associated with moderate levels of day 2 protein, high levels of day 2 lactose and day 2 other solids, and low levels of day 2 MUN. High levels of day 2 milk lactose and day 16 milk fat were associated (P < 0.05) with piglet gain during late lactation (day 10 to weaning). Genetic selection or improved management that allows for favorable milk traits at critical periods of lactation for improved weight gain will improve pig production.