|Hohenshell, L - IOWA STATE UNIVERSITY|
|Cunnick, J - IOWA STATE UNIVERSITY|
|Ford, S - IOWA STATE UNIVERSITY|
|Kattesh, H - UNIV. OF TENNESSEE|
|Zimmerman, D - IOWA STATE UNIVERSITY|
|Wilson, M - IOWA STATE UNIVERSITY|
|Lay, D - IOWA STATE UNIVERSITY|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 8, 1999
Publication Date: N/A
Interpretive Summary: Traditionally, pigs were weaned between 21 and 28 d of age. However, an emerging trend in modern swine production is to wean at a much earlier age (i.e., 10 d of age) to allow for moving the pigs to an offsite facility. Several advantages to this early weaning strategy have been reported, such as more piglets per sow per year, improved feed efficiency and growth rate, ,and leaner tissue content. Often, this improved performance has been attributed to a lack of immune system stimulation at offsite facilities. Because the mechanisms by which early weaned pigs attain their growth advantage remain unclear, we evaluated the behavioral, stress and growth characteristics of pigs weaned at 8 to 13 d of age as compared to pigs weaned at 27 to 34 d of age. Results from this study indicated that most of the differences between early and late weaned pigs are evident soon after weaning, but disappear by the time pigs reach market weight. Thus, it is evident that the increase in growth resulting from early weaning strategies is more complex than merely a lack of immune challenges to early weaned pigs. Most likely, the increased growth reported for early weaned pigs cannot be attributed to a single factor, but more likely to several factors including nutritional, environmental, and hormonal. Both industry and academic scientists working in the area of neonatal growth and performance in swine will find that this information adds to our current knowledge base regarding the effects of early weaning on growth and performance of the pig. This information will be particularly interesting to swine producers who are considering different weaning strategies for their herds.
Technical Abstract: Segregated- and medicated-early-weaning are technologies used to optimize the productivity and health of pigs, but these practices may also cause aberrant behaviors indicative of stress. Thus differences in early (10 d of age) and late (30 d of age) weaned pigs were investigated. At weaning, piglets were housed in groups of 4 in 16 pens (8 pens per treatment) into the same facility, thus they were not segregated. Body weights were recorded at birth, weaning, and approximately 42, 65, 102, 137, 165 (at slaughter) d of age. One-minute, instantaneous scan samples during a 10-min duration (at 0600, 1000, 1400, and 1800) were used to record the frequency of lying, standing, sitting and total number of drinks, feeder investigations, and time spent playing/fighting on 2, 3, and 4 d after weaning. Five-minute, direct observations were conducted on each pig at approximately 40, 60, 80 and 150 d of age. Direct observations were also made of the entire pen for 10 min at approximately 50, 95, 123, and 160 d of age to record aberrant behaviors. At 62 d of age, a handling and blood collection stress was imposed. At 165 d of age, a second stress test was conducted in response to rough handling and transport. Early weaned pigs spent more time playing/fighting (P<.006) than late weaned pigs during the 4 d after weaning, manipulated conspecifics more often at 40 d of age (P<.002), had greater percent hemoglobin (P<.03) during stress test 1, had greater ADG at 42 d of age (P<.03), and greater hypothalamic growth hormone releasing hormone receptor mRNA at slaughter (P<.06). Late weaned pigs had greater ADG between 137 and 165 d of age (P<.03). Overall, most differences found between early weaned and late weaned pigs were evident soon after weaning, but disappeared prior to slaughter.