title: Seasonal variation in growth of Berkshire pigs in alternative production systems.
abstract: OBJECTIVE
  The objective of the present study was to investigate the effects of farrowing month (FM), parity and sex on the growth performance of Berkshire swine raised in alternative production systems.
  
  
  METHODS
  A total of 40 farrowing records from 27 sows and 1,258 body weight (BW) records from 274 piglets collected over a two-year period were used for the analysis. The BWs were recorded at birth, weaning (28 d), 56, 84, 112, and 140 days. Any BW not recorded on schedule was recalculated to conform the days of age among corresponding BW records, using growth curves drawn with polynomial functions whose power was determined by the number of existing observations for each individual.
  
  
  RESULTS
  The mean parity (±standard deviation) of the sows was 3.42±2.14. The sows that farrowed in June had the lowest number of total born with an average of 6.25±2.22 piglets per sow. However, the lowest average number of piglets weaned at day 28 was found in sows that farrowed in May, as well as the highest number recorded for the stillborn piglets with an average of 2.67 piglets per sow. Moreover, the smallest increase in weight from birth to weaning occurred in piglets that were farrowed in May, which also corresponds with the average daily gain (ADG) of 0.29 kg and the last recorded weight measurement on day 140 of 41.69±1.45 kg. Contrastingly, the highest growth rate was found among pigs farrowed in June, with the largest increase in weight of 7.55 kg from birth to weaning, the highest ADG of 0.51 kg from birth to 140 day of age and the highest BW of 74.70±1.86 kg recorded on day 140.
  
  
  CONCLUSIONS
  Pigs farrowed in June also had the least number of piglets that died between birth and weaning. The zone of thermal comfort found in sows reared in indoor confinement systems did not improve the reproductive performance of the sows reared in an outdoor, alternative production system, while the growth performance of the piglets was improved when the ambient temperature was consistently hot or consistently cold.
authors.affiliation: Department of Animal Sciences, College of Agriculture and Environmental Sciences, North Carolina Agricultural and Technical State University, Greensboro, NC 27410, USA.
authors.forename: Hyeon-Suk
authors.initials: HS
authors.lastname: Park
authors.affiliation: Department of Animal Sciences, College of Agriculture and Environmental Sciences, North Carolina Agricultural and Technical State University, Greensboro, NC 27410, USA.
authors.forename: Sang-Hyon
authors.initials: SH
authors.lastname: Oh
keywords: Alternative Production System; Berkshire; Growth; Pig