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A database containing 12,110 farrowing records from 16 commercial farms was abstracted from the PigCHAMP[R] production information system. The farms were selected based on the willingness of producers to keep records and average weaning age. The ADFI records of 10,846 of these lactating sows were also obtained. Sows weaned at [less than or equal to] 7 and > 28 d after farrowing were excluded. Farrowing rate excluding sows culled for nonreproductive reasons after mating from the denominator was 85.5%. Parity, farrowing season, and the lactation length x ADFI interaction were associated with farrowing rate (P < .05) using a categorical additive linear model in the CATMOD procedure in SAS (1988). Parity 1 sows had a lower farrowing rate than parities 2 and [greater than or equal to] 6 (P < .05). The summer and spring groups had the lowest and second-lowest farrowing rates among the four seasons (P < .05). In the high ADFI ([greater than or equal to] 5.7 kg) group, no differences in farrowing rate were observed between lactation length groups. In the low ([less than or equal to] 4.2 kg) and medium (4.2 to 5.6 kg) ADFI groups, farrowing rate varied depending on lactation length. In conclusion, our results suggest that optimizing ADFI ([greater than or equal to] 5.7 kg) alleviates the negative effects of lactation length on farrowing rate. Key Words: Farrowing Rate, Lactation Duration, Feed Intake, Reproductive Efficiency

This experiment was conducted to determine the effects of gestational energy intake on glucose tolerance, LH profiles, and reproductive performance of first-litter sows. Sixteen pregnant gilts were assigned to either high energy (11 Mcal of ME/d; H) or normal energy (6.5 Mcal of ME/d; N) diets during gestation. They did not receive the treatment diets until 35 d of gestation and had free access to the same commonly used diet during lactation. A glucose tolerance test (1 g glucose per kg BW) was conducted after 18 h of feed deprivation on 110 d of gestation and 15 d of lactation. Blood samples were collected at -10, -5, 0 (immediately before glucose infusion), 2, 4, 6, 8, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100, 120, 150, and 180 min for assay of glucose and insulin concentrations. Blood samples were also taken on d 7, 14, and 21 of lactation and on 1 d postweaning for 6 h with 10-min intervals for LH characteristics. Sows in Group H had greater gain of BW and backfat during gestation (P < .001) and had less feed intake and greater weight loss during lactation (P < .002) than those in Group N. Sows in Group H (8.0 d) showed 1.6 d longer (P = .07) weaning-to-estrus intervals than those in Group N (6.4 d). After glucose infusion, insulin levels in Group H were higher (P < .05) than those in Group N. Lower LH concentrations on 1 d postweaning were found (P < .05) in sows in Group H than in Group N. This study indicates that energy intake during gestation is negatively related to feed intake during lactation. Reduced feed intake during lactation of sows having high gestational energy impairs glucose tolerance, suggesting that interaction of insulin with LH secretion may influence weaning-to-estrus intervals. Key Words: Energy Intake, Glucose Tolerance, Insulin, Luteinizing Hormone, Sows

Daily feed intake during lactation was recorded for 20,296 lactating sows on 30 commercial farms in the United States. Each lactation feed record was categorized into one of six patterns: RAPID, rapid increase in feed intake; MAJOR, major drop; MINOR, minor drop; LLL, low feed intake throughout lactation; LHH, low intake during the 1st wk then an increase in feed intake for the remainder of lactation; and GRADUAL, gradual increase. A database containing 24,340 farrowing records and 19,015 subsequent litter records were abstracted from the PigCHAMP[R] data files of the farms enrolled in the study. Multiple regression analyses revealed that ADFI during lactation had nonlinear or linear associations with weaning-to-first service interval (WSI), weaning-to-conception interval (WCI), litter weight at weaning (WWT), and subsequent litter size (SLS). Sows having LLL and LHH had longer (P < .01) WSI and WCI than the other patterns. Sows with MAJOR had a longer WCI (P < .05) than females with RAPID. Further, sows having MAJOR had lighter (P < .01) WWT than those with RAPID, MINOR, and GRADUAL. Sows having MAJOR had a higher (P < .01) proportion of females culled for anestrus relative to RAPID. Furthermore, sows exhibiting a drop in feed intake in either wk 1 or 2 were more likely to be culled for anestrus than sows having no drop. These results suggest that both the amount and pattern of feed intake during lactation influence subsequent reproductive performance. Key Words: Lactation, Sows, Feed Intake, Reproductive Disorders, Weaning Weight, Reproductive Efficiency

This study created and used a database containing 25,719 farrowing and 19,393 subsequent litter records abstracted from the PigCHAMP[R] records of 30 commercial farms and daily feed intake records of 25,040 of these lactating sows. Each lactation feed record was categorized into one of six patterns: RAPID, rapid increase in feed intake following farrowing; MAJOR, major drop in feed intake during lactation; MINOR, minor drop; LLL, low feed intake throughout lactation; LHH, low feed intake during the first week then increasing for the remainder of lactation; and GRADUAL, gradual increase in feed intake throughout lactation. At the herd level, patterns RAPID, MAJOR, MINOR, LLL, LHH, and GRADUAL were observed in 22.8%, 32.9%, 27.8%, 1.0%, .8%, and 14.7% of sows, respectively. On a sow basis, across all feed intake records of all farms, patterns RAPID, MAJOR, MINOR, LLL, LHH, and GRADUAL were observed at frequencies of 17.8%, 38.3%, 25.8%, 1.2%, 1.5%, and 15.4%, respectively. Using logistic regression, the risk factors affecting the occurrence of MAJOR and MINOR patterns were lower parity, thicker backfat, higher room temperature, and greater feed intake during early lactation. Average daily feed intake and the day of peak intake were 5.2 (1.4 SD) kg/sow and 12.6 (4.6 SD) d after farrowing. Regression coefficients of factors affecting ADFI derived from multiple regression analyses were 247 g for parity, 9 g for weaning litter weight (kg), -13 g for room temperature ([degrees] C), 62 g for lactation length (d), and -.4 g for energy density (kcal/kg). This study demonstrated substantial individual sow and farm variation in overall feed intake and pattern of feed intake during lactation. It also identified key risk factors (i.e., parity, lactation length, room temperature, weaning litter weights, energy density) for ADFI and pattern of feed intake on commercial farms. Key Words: Sows, Lactation, Feed Intake, Feeding Behavior

Thirty-six primiparous sows were assigned to one of five treatments designed to mimic the lactation feed intake patterns observed in a previous study of commercial farms: high energy intake (HHH) or low energy intake during each week of a 3-wk lactation (LLL), or reduced intake during wk 1 (LHH), wk 2 (HLH) or wk 3 of lactation (HHL). The metabolizable energy intake of sows was either 16.5 (H) or 6.5 (L) Mcal/d. Diets were equal in lysine, providing 45 g/d. The HHH sows had a shorter (P < .05) weaning-to-estrus interval (9 [+ or -]3.2 d) than the sows in the LLL (23 [+ or -]3.5 d), HLH (22 [+ or -]3.5 d), and HHL (18 [+ or -]3.2 d) groups. The LH pulse frequencies of HHH (d 14:1.5 pulses/8 h; d 21:2.1 pulses/8 h) were greater (P < .05) than those of LLL (.2 pulses/8 h) and HLH (.5 pulses/8 h) on d 14 and those of LLL (0 pulses/8 h) and HHL (.9 pulses/8 h) on d 21 of lactation. No differences (P >.1) in mean serum concentrations of LH were observed among treatment groups either on d 21 of lactation or on d 1 postweaning. When fed a low-energy diet, sows had lower (P < .05) concentrations of serum insulin and plasma glucose than did sows fed a high-energy diet. Our results indicate that energy intake during lactation influences circulating insulin and glucose levels and LH pulse frequency and amplitude during mid-lactation and during the postweaning period. Key Words: Lactation, Sows, Luteinizing Hormone, Insulin, Glucose, Energy