Diurnal feeding patterns have been described for wild foraging pigs (Signoret et al. 1975) as well as commercial 'ad libitum' fed pigs (Hall, 1997). Restricted feeding is used in some breeding programs for selection of lean meat growth. In this experiment, we investigated whether feeding regime affects the feeding patterns of pigs.

Insulin-like growth factor-I (IGF-I) is a naturally occurring polypeptide produced in the liver, muscle and fat tissues. It is known to be associated with growth and development during the post-natal growth period. Evidence for strong genetic correlations between juvenile IGF-I and performance traits would suggest this physiological measure would be useful as an early selection criterion. This paper reports estimates of genetic parameters from 9 trials where IGF-I was measured in juvenile pigs. All trials involved populations undergoing active selection for improved performance (e.g. efficient lean meat growth). Juvenile IGF-I was moderately heritable (average h2: 0.31) and influenced by common litter effects (average c2: 0.15). Genetic correlations (rg) between juvenile IGF-I and backfat (BF), feed intake (FI) or feed conversion ratio (FCR) traits were generally large and positive: rg averaged 0.57, 0.41 and 0.65, respectively. Phenotypic correlations (rp) between juvenile IGF-I and BF, FI or FCR were much lower (rp averaged 0.21, 0.09, and 0.15, respectively) as residual correlations between IGF-I and these performance traits were low, consistent with being measured at very different times. Correlations (genetic or phenotypic) between juvenile IGF-I and growth traits (e.g. lifetime daily gain or test daily gain) were relatively low, with average values within ± 0.09 of zero. Results from the trials reported here, and several physiological studies, indicate that information on juvenile IGF-I concentration can be used as an early physiological indicator of performance traits traditionally measured later in life. There is a clear role for juvenile IGF-I to facilitate pre-selection and more accurate selection of livestock for hard to measure traits, such as FCR, in pig breeding programmes.

Pigs adapt their feeding patterns to the level of feed restriction by modifying their feed intake in the early hours of the day (McSweeny et al, 2003). This observation led to the investigation of a new feeding-pattern trait, defined as the percentage of the total daily feed intake eaten between midnight and 0600 h (P6AM). This trait (μ=35%) is specific to the feeding system studied and may provide additional information for genetic improvement of performance traits. The aim of this experiment was to estimate genetic correlations between P6AM and economically important traits.

Individual feed intake data were recorded using electronic feeders for 278 animals in a commercial group-housed environment. A reduction in feed intake compared to the expected was observed. Factors influencing this reduction in feed intake are described. Recommendations are made for using these factors in the operation of electronic feeders to minimise the reduction in feed intake.

Insulin-like growth factor-I (IGF-I) is a naturally occurring polypeptide produced in the liver, muscle and fat tissues. It is known to be associated with growth and development during the postnatal growth period. Evidence for strong genetic correlations between juvenile IGF-I and performance traits would suggest this physiological measure would be useful as an early selection criterion. This paper reports estimates of genetic parameters from 9 trials where IGF-I was measured in juvenile pigs. All trials involved populations undergoing active selection for improved performance (e.g. efficient lean meat growth). Juvenile IGF-I was moderately heritable (average h 2: 0.31) and influenced by common litter effects (average c 2 : 0.15). Genetic correlations (r g) between juvenile IGF-I and backfat (BF), feed intake (FI) or feed conversion ratio (FCR) traits were generally large and positive: r g averaged 0.57, 0.41 and 0.65, respectively. Phenotypic correlations (r p) between juvenile IGF-I and BF, FI or FCR were much lower (r p averaged 0.21, 0.09, and 0.15, respectively) as residual correlations between IGF-I and these performance traits were low, consistent with being measured at very different times. Correlations (genetic or phenotypic) between juvenile IGF-I and growth traits (e.g. lifetime daily gain or test daily gain) were relatively low, with average values within ± 0.09 of zero. Results from the trials reported here, and several physiological studies, indicate that information on juvenile IGF-I concentration can be used as an early physiological indicator of performance traits traditionally measured later in life. There is a clear role for juvenile IGF-I to facilitate pre-selection and more accurate selection of livestock for hard to measure traits, such as FCR, in pig breeding programs.