Higher Productivity Levels Tap Sows' Energy Reserves

Genetic selection for increased sow productivity, including number of pigs born alive, number weaned and litter weaning weight, has increased the demands for milk production during lactation. Without an increase in feed intake, lactating sows lose more body weight.

The objectives of this study were threefold: 1) to quantify and model the daily lactation feed intakes of two pure lines — Yorkshires and Landrace — selected for increased sow productivity — and pure line Durocs selected for postweaning performance; 2) to evaluate the incidence of transient (short-term) reductions in feed intake, and 3) to evaluate the relationship of feed intake to measures of sow productivity.

A total of 19,321 daily feed intake records (Figure 1) collected by Tempel Genetics, Inc., Gentryville, IN, over a 19-month period and representing 993 sow lactations were used in the study (44 Duroc, 450 Yorkshire, 499 Landrace).

Data was assigned to 21 contemporary groups defined as farrowing groups within 28-30-day periods. Five different corn-soybean-based lactation diets were fed during the study, ranging from 3.19 to 3.33 Mcal metabolizable energy (ME)/kg or roughly 1.45 to 1.51 Mcal ME/lb.

Daily ME intakes were calculated as the daily feed intake (lb./day) times the specific diets' calculated ME concentration (Mcal/lb.). Data was assigned to four seasons (Figure 2): summer (June 15-Sept. 14), fall (Sept. 15-Dec. 14), winter (Dec. 15-March 14), and spring (March 15-June 14).

Lactation records included the number of pigs after crossfostering, number weaned and litter weaning weight adjusted to a 21-day weight standard. Wean-to-first service interval was recorded for all sows (773) retained for rebreeding.

Sows were fed 3 lb. of feed within 8-12 hours after farrowing, then fed 8 lb. (4 lb. twice/day) the day after farrowing. When feed consumption reached 12 lb./day, sows were fed three times daily; at 16 lb./day, were fed four times, and at 20 lb./day, were fed five times daily. A preliminary analysis was conducted to evaluate the overall trend in daily feed intake relative to days of lactation.

Yorkshire and Landrace sows had greater feed intakes than Duroc sows in the study. Lactation feed intakes from Day 1 to Day 19 were less for the summer period than other periods — 19.1 vs. 22.3 Mcal ME/day). And 21-day litter weights were only slightly less for the summer period (138.7 lb. vs. 140.8 lb.).

Overall, sow feed and ME intakes had stronger relationships to 21-day litter weight than number weaned. In this study, sows with greater than average 21-day litter weights only consumed 12 to 14% of the additional energy required to produce each additional pound of 21-day weaning weight. Therefore, sows with greater-than-average 21-day litter weights were likely to lose more body weight during lactation.

Daily feed intake records showed that feed intake increased rapidly the first five days of lactation, moved through a series of increases and decreased through mid-lactation, then slowed from Days 17 to 21 of lactation. Previous data has shown feed intake peaks at Day 17.

Sow weight loss, especially empty body protein (used to predict nutrient requirements), increases the risk of increased days from weaning to first estrus.

Sow lactation feed intakes of this trial were substantially greater than those reported in the National Research Council (NRC) Nutrient Requirements for Swine (1998). Improved sow productivity, litter size and 21-day litter weight are important to reduce the cost of each weaned pig. Similarly, weaning weight is associated with days to market, although increased litter sizes and 21-day litter weights require greater energy intakes during lactation.

Seedstock suppliers should consider the measurement of and selection for increased lactation daily feed intake or sows with decreased lactation body weight loss or decreased predicted lean tissue loss. Increased days from weaning to estrus results in increased nonproductive days, decreased conception rates and decreased subsequent litter size.

Ongoing, intense selection for litter size and litter weight will likely result in sows tapping lean body tissue reserves during lactation. This data may encourage the selection for increased lactation feed intakes, which could in turn improve rebreeding rates and increase sow longevity.

Researchers: Allan Schinckel and M.E. Einstein, Purdue University; Clint Schwab, National Swine Registry; and V.M. Duttlinger, Tempel Genetics. Contact Schinckel by phone at (765) 494-4836 or e-mail aschinck@purdue.edu.

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