September, 1996 ^. Volume 19, Number 8

At the recent annual meeting of the American Society of Animal Science in Rapid City, South Dakota many swine related research papers were presented. The following seven papers that are summarized have some potential for rapid application in the swine industry.

• Researchers from the Netherlands reported on production and reproduction data from Dutch Landrace pigs. This data set included 32,811 gilts from 228 herds. To determine the optimal management of first parity sows on-farm test results of all gilts were related to longevity of the sows and total number of live piglets produced. For longevity in Dutch Landrace it was determined that the optimum weight at 180 days of age was 176-242 pounds and the optimum ultrasonic backfat was 10-16 mm. Age at first mating was optimal at 240 days. Lesser age at first mating had a negative effect on total pigs born alive and higher age at first mating had a negative effect on longevity.

• Billy Flowers, NCSU, reported on a study designed to determine the paternity of pigs born to sows bred with heterospermic mating regimes. The mating regime consisted of an initial natural service followed by two AI. Seventeen mature boars were used for both natural service and AI with a single, different boar used for each mating and matings arranged such that every possible combination of boars occurred an equal number of times. Paternity was determined by DNA fingerprinting using blood samples from pigs, sows, and boars. In litters with two and three sires represented, one boar sired the majority (p < .05) of pigs 84% and 76%, respectively. In litters with three sires and more than 13 pigs the distribution among sires tended to more uniform than in smaller litters (66%, 26% and 8% vs. 84%, 11% and 5%). In litters with three sires, boars used for the first (37%) and second (35%) AI sired more (p < .05) pigs than boars used for natural service (28%). In litters where natural service and first AI produced all the pigs, more pigs (p < .05) were offspring of the AI (76%) than natural service (24%). In litters where all the pigs were produced by the two AI matings, more pigs (p < .05) were sired by the first (70%) than second (30%) AI boar. These results indicate, that in this herd, the majority of pigs in a litter produced by heterospermic mating were sired by a single boar that bred the sow between 12 and 24 hours after first detected estrus.

• Researchers at the University of Guelph designed an experiment to manipulate the sows weaning to estrus interval using the light dark cycle to facilitate successful timed inseminations. This type of procedure may allow sows to be inseminated at a specific hour with regard to weaning time, thereby eliminating the need for heat detection. Over a 4 week nursing period 48 multiparous sows were maintained on a 14 hour light and 10 hour dark cycle. The light period was from 4:00 AM to 8:00 PM. Sows were randomly assigned one of 4 weaning times 4:00 AM, 10:00 AM, 4:00 PM and 10:00 PM. At weaning sows were placed in crates, injected with 1000 IU of PMSG, and maintained on the light dark cycle. Blood samples were collected serially over a 5 day period to determine the time of lutenizing hormone (LH) peak as an indicator of onset of estrus. Weaning to LH peaks were from 92 h to 110 h (18 h), 74 h to 110 h (36 h), 80 h to 134 h (54 h), and 74 h to 116 h (42) for the 4:00 AM, 10:00 AM, 4:00 PM, and 10:00 PM groups respectively. Ranges in weaning to LH peak were significantly greater (P < .05) for sows weaned at 4:00 PM and 10:00 PM than those weaned at 4:00 AM or 10:00 AM. Sows weaned at 4:00 AM more frequently exhibited onset of estrus during the light hours (P < .05). This trial would indicate that sows subjected to this light dark cycle and weaned at 4:00 AM may be successfully inseminated at 88 hours and 104 hours post weaning.

• Age at first mating was demonstrated to have an effect on gilt removal rate and litter size of parity one sows by University of Minnesota researchers. Computerized records of 24,056 females from 20 commercial farms were analyzed to investigate the influence of gilt age at first mating on reproductive performance and longevity. Gilt age at first mating ranged from 170 to 320 days. Removal rate of gilts was significantly (P < .001) effected by age at first mating. Gilts bred before 210 days of age tended to have a higher removal rate at parity 0. Removal rate of parity 1 females increased as age at first mating increased. Age at first mating also influenced (P < .001) litter size in parity 1 sows. Approximately .14 more total born and .11 more born alive pigs were achieved by each increase of 10 days of age at first mating. Age at first mating did not effect litter size during the later parities. These results would indicate that an age of 210-250 days at first mating may be preferred.

• Sow productivity differences between normal and stress-gene carrier Landrace females were evaluated by researchers from the University of Tennessee and Iowa State University. A total of 841 Landrace females, 641 normal and 218 stress carrier, were evaluated for differences in pigs born alive, pigs at 21 days, litter weight at 21 days, survival to 21 days, and farrowing interval. The results of this investigation indicated no significant differences in maternal performance between normal and PSS carrier dams. This study indicates that factors other than maternal performance should determines whether PSS carrier females are retained for breeding purposes.

• University of Illinois scientists reported on the effects of group size and feeder type on growth performance, feed intake level, and feed intake pattern. Group sizes of 2, 4, 8 and 12 pigs per pen and feeder types of single space, conventional, and electronic feed intake recording equipment (FIRE) were investigated. Four hundred and sixteen pigs in 64 pens were fed ad libitum over a 4 week period from 57 to 105 pounds. Pigs on the FIRE feeder consumed less (p < .01), but grew at a similar rate and had an improved (p < .01) gain:feed ratio compared to pigs on conventional feeders. Feed intakes and growth rates declined (p < .05) with increasing group size; however, there was no effect of group size on gain:feed ratio. For pigs on the FIRE feeders, there was no effect of group size on the number of visits to the feeder each day; however, feeder occupation time per day was reduced (p < .01) for the larger group sizes and feed consumption rate was greatest (p < .05) for group sizes of 12 pigs. Diurnal feeding patterns were influenced by group size with pigs in the larger groups (8 or 12 pigs) spending proportionately more time in the feeder and consuming a greater proportion of their feed during the night time. This study suggests that the changes in feeding behavior shown by pigs in the larger groups were not sufficient to maintain feed intake levels and growth rates.

• Meat quality was evaluated in a project jointly conducted by PIC USA and the University of Wisconsin. Four hundred and seventy five pigs were randomly selected and evaluated at 4 major packing plants over two days at each plant. Slaughter day had a significant effect on meat quality with 52% of all loins classified as PSE occurring on one day. Also the majority (75%) of PSE loins were from stress-gene free pigs. These results would indicate that the predominant cause of PSE meat in this study was environmental.

Todd See

Space recommendations for finishing pigs have usually been 8 square feet per animal. This recommendation was used with pigs that went to slaughter at 220 to 230 lbs. Slaughter weights have moved progressively heavier in recent years, however. Average slaughter weights for may producers now approach approximately 250 lbs. How have the space allocation needs per animal changed as slaughter hogs were held to these heavier weights?

Researchers Mike Brumm and Jim Dahlquist recently reported (1996 Nebraska Swine Report) the results of their investigations into space requirements with barrows that were fed to 300 lbs. They selected 300 lbs. for an end weight since they recognized that many producers were already approaching 270 lbs. for an average sale weight. One hundred eighty single source barrows were used and were randomly allotted to test groups with space allocation treatments of 7 , 9, or 11 sq.ft. per pig. These space allocations were in addition to the space occupied by the feeders.

Each pen held 12 pigs. If a pig died or had to be removed from the trial for other reasons, the pen size was adjusted so that the space allocation per pig remained the same during the complete trial. This procedure was maintained until the pigs reached 300 or more lbs. As individual pigs reached the target weight of 300 lbs., they were removed and no additional pen space adjustments were made.

The building in which this study was conducted was a fully slatted, naturally ventilated confinement facility. A two-hole feeder and two nipple waterers were in each pen. Intermittent sprinklers were used in the summer which were activated at 80 degrees F.

The initial diet was a corn-soybean meal mix with 1.1 % lysine. The lysine content was reduced by 0.1 % at 100 lbs. This 0.1 % reduction was repeated again at 150, 200, and 250 lbs.

Table 1 outlines the pig performance observed in this trial.

By the end of the first 29 days on test, a linear decrease (P<.075) was observed in average weight and daily gain as the space allocation increased. However, by the end of 99 days on test the pigs with 9 sq. ft. per pig had the best performance and those with 11 sq. ft. per pig had the poorest. Overall, pig performance exhibited a significant quadratic effect of space allocation on average daily gain with the pigs with 7, 9, and 11 sq. ft. having daily gains of 1.85, 1.89, and 1.82 lbs. per day, respectively.

Carcass backfat, lean gain, and average daily feed intake were not influenced by space allocations. However, feed efficiency decreased (P<.075) as the space allocation increased.

A significant quadratic effect was observed in the variation of individual pig weights within a pen. The least variation occurred among those pigs that were allotted 9 sq. ft. while the most was among those with 7 sq. ft.

As the results in Table 1 suggest, barrows carried to 300 lbs. did well at 9 sq. ft. per pig, based on average daily gain and average daily feed intake.

Charles Stanislaw

Changing the pH of manure with an alkaline byproduct (ABP) may be one way to cut hog odors, according to research conducted at Iowa State University. ABP is an alkaline byproduct from coal-generator power plants, cement manufacturing and lime manufacturing. It is similar to talcum powder in consistency.

In the study, 24 tons of ABP was mixed with 440,000 gallons of hog manure and then added to an earthen storage basin. Air samples were then taken from the storage basin area and downwind of the field after the manure was top spread and analyzed by an odor panel at ISU. The researchers found a marked decrease in odors from ABP-treated hog manure, both when it was in a storage basin and when it was spread on top of a field.

"Our goal was to reduce but not eliminate odors," says Dwaine Bundy, a researcher at ISU involved with this project. "We also felt ABP-treated manure may be an alternative to injection since some land cannot handle injection."

Based on this research, Bundy says adding ABP to manure slurry is one solution for serious odor problems. But he also warns that since ABP gives an initial release of ammonia after agitation with manure, this solution is not recommended for pits in buildings.

HogHealth
Vol. 6, No. 1

Number of accesses to this file:
Last modified August 7, 2000.