Six years of industry changes are covered in the latest survey of the pork industry from USDA's National Animal Health Monitoring System (NAHMS).

NAHMS' "Changes in the U.S. Pork Industry 1990-1995" compares results of the 1990 National Swine Survey and the Swine '95 Study. The 34-page booklet reports changes in industry demographics, health and productivity, and management.

NAHMS officials point out that some of the changes seen during the survey period are magnified by changes in how a few of the questions are phrased.

Demographic Changes The 1990 national survey covered 18 states representing 95"percent" of the U.S. hog population. The Swine '95 Study was conducted in the top 16 hog states representing 91"percent" of the hog population.

In the six years from 1990 through 1995, hog and pig inventory estimates increased about 7"percent". Year-to-year inventories changed only slightly, but the overall trend was upward.

"Breeding inventory made up approximately 12"percent" of total inventory over the 1990-1995 period, but showed a general downward trend indicating a more productive industry," the NAHMS report indicated.

As expected, the number of U.S. hog operations declined by more than 30"percent" during the survey period, showing a steady drop annually, culminating with nearly a 13"percent" decline from 1994 to 1995. The trend is illustrated in Figure 1.

The smallest herds still dominate the industry scene, but they are showing a steady decline. While other, smaller size categories continue to decline in production, the category of 2,000 or more head is grabbing a growing proportion of U.S. hog inventory, at 44"percent" in 1995.

Overall, there were nearly 4 million more hogs and pigs in 1995 than in 1990. Notable increases were seen in Alaska, California, Colorado, Mississippi, Missouri, North Carolina, Oklahoma, Utah and Wyoming. North Carolina, Oklahoma and Wyoming more than doubled their total hog inventory. Only Alaska (from 40 to 50) and New Jersey (from 700 to 750) reported increases in the number of hog operations from 1990 to 1995.

World pork production climbed 8"percent" during the survey period, led by Ireland, Korea, Mexico, China, Taiwan and France, all with production increases of 20"percent" or more. Major production declines were experienced in Germany, Switzerland, several eastern European countries, the former Soviet Union and Japan. The U.S. came in at a 11"percent" increase for the period.

Health, Productivity >From 1990 to 1995, reported stillbirths and mummies per litter plummeted nearly 25"percent", while born alive per litter reportedly decreased 1"percent". "Therefore, though the total pigs born per litter dropped (10.34 to 10.02), the percent born alive per litter increased from 91.59"percent" to 93.51"percent"," the report indicated. Preweaning deaths per litter decreased 20"percent".

There has been a steady increase in the number of pigs saved per litter each year since 1990, going from about 7.9 in 1990 to about 8.3 in 1995.

Crushing or "laid ons" were by far the leading cause of preweaning deaths in the report (Figure 2.) There was a significant drop in piglet deaths traced to scours. A slight rise in preweaning deaths of "unknown origin" was also reported.

There was essentially no difference in the number of nursery pig deaths from 1990 to 1995. In weaned pigs weighing under 40 lb., just under 2.5"percent" died in the nursery phase.

However, the causes of nursery deaths are notable. Scours was identified as the leading cause in 1990 (25.1"percent"), while respiratory problems made up the highest mortality (32.4"percent") in 1995. Starvation and unknown ailments also accounted for a larger percentage of nursery pig deaths in 1995 than in 1990 (Figure 3 on page 34).

In the grow-finish phase, only minor differences were noted between the two NAHMS studies. The percentage of grow-finish hogs that died averaged around 2"percent".

Scours problems increased from 1.9"percent" to 7.1"percent" from 1990 to 1995. Respiratory problems declined from 47.9"percent" in 1990 to 39.5"percent" in 1995, but still remained the leading cause of death in grow-finish pigs. Lameness caused about 8"percent" of deaths in both surveys, while deaths caused by trauma dropped from 8.6"percent" to almost 7"percent". Other known problems and unknown maladies accounted for a large percent of the grow-finish deaths in both surveys, 33.7"percent" in 1990, escalating to 38.6"percent" in 1995.

The percent of operations with animals testing positive for Porcine Reproductive and Respiratory Syndrome (PRRS) increased from 1990 to 1995 to include nearly one-half of all tested operations with at least one sow.

Reported cases of both salmonella and Actinobacillus pleuropneumonia nearly doubled from 1990 to 1995. The cases of Transmissible Gastroenteritis and E. coli were nearly unchanged in the two surveys.

Serotypes responsible for salmonella infections in hogs continue to increase. The three most common serotypes of cholerasuis, derby and typhimurium continue to be the most commonly isolated. But each year, the trio account for a smaller proportion of the total, going from 82"percent" in 1990 down to 58"percent" in 1995.

Management Changes The percentage of operations using artificial insemination doubled over the six-year period, expanding from 3.8"percent" to 7.8"percent". Handmating of sows and gilts accounted for a fourth of the operations studied. Penmating still leads as the most commonly used breeding method, but declined from 67.1"percent" in 1990 to 53.7"percent" by 1995.

There was a noticeable trend of increased use of antibiotics as a prevention practice in both sows and gilts. Use of injectable antibiotics nearly doubled (from 15.9"percent" to 30.3"percent"), while use of antibiotics in water also climbed from 0.8"percent" to 6.6"percent".

Likewise, a trend of increased antibiotic use on boars was also identified. Injectable antibiotics use rose significantly from 1.5"percent" in 1990 to 22.3"percent" in 1995. Feed antibiotic use also rose sharply, from 10.9"percent" in 1990 to 38.4"percent" in 1995.

Half of all farrowing operations practiced all-in, all-out (AIAO) management in both surveys - 48.2"percent" in 1990, 46.2"percent" in 1995. The overall inventory of females managed as AIAO increased from 55.1"percent" to 65.5"percent".

"These results indicate that more, larger operations are using AIAO management in the farrowing phase," the report states.

The overall percentage of nursery pigs managed AIAO climbed more than 16"percent" from 53.5"percent" to 69.8"percent" during 1990 to 1995, while the number of operations practicing AIAO in the nursery remained virtually unchanged at nearly 48"percent".

In grow-finish, the percentage of hogs raised AIAO nearly doubled during the survey period, climbing from 23.9"percent" to 46.3"percent". The percentage of operations using AIAO in grow-finish rose from 30"percent" to 42.4"percent".

AIAO management by stage of operation is illustrated in Figure 3.

The NAHMS report also revealed the following industry changes:

* Overall, in 1995 compared to 1990, the average pig was weaned three days younger, stayed in the nursery 1.7 days longer and experienced about the same length of stay in the grow-finish phase (118 days).

* The vast majority of hog operations continue to be run by independent producers who market their own animals.

* Producers using a recordkeeping system slipped slightly from 92.5% in 1990 to 90.6% in 1995. Hand-held records continue to be used the most. Use of computers increased from 8.0% in 1990 to 13.2% in 1995.

* Vaccination against some common hog diseases has dropped from '90 to '95, including: erysipelas from 69.6% to 56.2%, E. coli scours from 49.9% to 47.4%, parvovirus from 65.6% to 54.1% and leptospirosis from 70.5% to 59.4%.

* Isolation and testing procedures decreased for new breeding stock and rose only slightly for feeder pigs.

* Producers in the survey reported a dramatic drop in the use of veterinarians for regular visits and consultations alike. Overall, use of veterinarians for any purpose declined from 75.4% in 1990 to 49.4% in 1995.

The NAHMS report explained that producers with finishing floors were less likely to use a veterinary consultant than those who farrowed sows. This may explain the large decline.

* On-farm burial or burning still largely dominates carcass disposal, accounting for 84% in 1990, 72.1% in 1995. On-farm composting sprang from virtually nothing in 1990 to 12% in 1995.

* Hog operations remained fairly close geographically. More than 70% are three miles apart or closer. Most reported the nearest known hog market to be more than five miles away. More than 15% of operations were within five miles of the nearest market in both years