Estimation of genetic trends from 1977 to 1998 for farrowing characteristics in the French Large White breed using frozen semen

Abstract

The objective of the study was to estimate genetic trends from 1977 to 1998 in the French Large White (LW) breed for stillbirth and associated traits measured at farrowing using frozen semen. Two groups of pigs (G77 and G98) were obtained by inseminating LW sows with semen from LW boars born either in 1977 or in 1998. A second generation was produced by inter se mating in each group. Farrowing was thoroughly supervised through both direct observations and video recording all long farrowing on a total of 137 first-and second-parity litters produced by sows from this second generation (68 G77 and 69 G98 litters, respectively). Measurements included birth time, weight and birth characteristics (including orientation, presence of cyanosis or oedema, membrane obstruction, umbilical cord length/content) of each piglet, as well as sow traits (weight and backfat thickness, farrowing duration, litter size and within-litter variation of weights at birth). The data were analysed using linear or generalised linear mixed models, according to the definition of the trait (continuous or binary data). The importance of several effects to piglet probability of stillbirth was then quantified by computing the reduction of variance associated with the addition of each effect in the model. Litter size did not significantly differ in first parity, but was higher in G98 second-parity sows: the differences for global (including pre partum dead piglets) and total numbers of piglets born per litter were 12.3 6 1.1 and 11.3 6 0.6, respectively. G98 sows also had a higher number of stillbirths in both parities (10.7 6 0.3 stillborn per litter). Piglets from G98 litters were heavier at birth (1130 6 40 g for birth weight adjusted for litter size), without any increase in within-litter heterogeneity of birth weight. No significant difference was detected between G77 and G88 groups for farrowing length and the distribution of time interval between piglet births. G98 stillborn piglets had longer and more often empty umbilical cords at birth. G98 piglets born alive also had more often umbilical nodes than G77 piglets. These characteristics were considered as indicators of increased farrowing difficulties and risk of hypoxia at birth in G98 pigs. Time of birth of each piglet, sow fatness at farrowing and time of first placenta expulsion were the main factors of variation of the piglet's probability of stillbirth.

Estimation of genetic trends from 1977 to 1998 of body composition and physiological state of Large White pigs at birth

“…Randomly chosen males and females from each of the two groups of pigs were kept for breeding and produced three successive generations of pigs by inter se mating. Further details on the experimental design are given in Tribout et al (2003), Canario (2006) and Canario et al (2007).…”

“…The main reproductive performances of their dams, i.e. sows from the second generation, are given by Canario et al (2007). Sows were weighed and ultrasonically measured for backfat thickness on day 111 of gestation.…”

“…Sow parturition was observed continuously through video supervision from an adjacent room. Each expelled piglet was immediately caught, dried, classified as dead or alive and weighed as described in Canario (2006) and Canario et al (2007).…”

“…10%, 15% and 26% of the mean were reported by Tribout et al (2003 and in the French Large White over the period 1977 to 1998 by comparing pigs issued from boars born either in 1977 or 1998. Yet, selection is likely to have affected many other traits, such as farrowing survival, which has been shown to decrease by Canario et al (2007). This deterioration could be related to differences in piglet maturity at birth.…”

Estimation of genetic trends from 1977 to 2000 for stress-responsive systems in French Large White and Landrace pig populations using frozen semen

“…The expected correlation between cortisol and ECLC was confirmed in G98 pigs; however, no relationship between adrenaline and carcass composition measures was found. On the same experimental design, other studies have estimated genetic trends for traits measured at farrowing in the LW breed (Canario et al, 2007a and2007b). The results suggest that the improvement in lean growth rate and in sow prolificacy from 1977 to 1998 has resulted in a lower maturity of piglets at birth.…”