Fetal development in the pig in relation to genetic merit for piglet survival1

Genetic trends for body composition and blood plasma parameters of newborn piglets were estimated through the comparison of two groups of pigs (G77 and G98, respectively) produced by inseminating Large White (LW) sows with semen from LW boars born either in 1977 or in 1998. Random samples of 18 G77 and 19 G98 newborn piglets were used for whole carcass and tissue sampling. Plasma concentrations of glucose, albumin and IGF-1 were determined on 75 G77 and 90 G98 piglets from 18 litters. The G98 piglets had less carcass dry matter, protein and energy (P , 0.01) than their G77 counterparts. When expressed in g/kg birth weight, livers were lighter (P , 0.001) and contained less glycogen (P , 0.01) in G98 piglets, with no difference in the activity of the hepatic glucose-6-phosphatase between G98 and G77 piglets. Concentrations of protein, DNA, RNA in longissimus dorsi muscle were unaffected by selection. Plasma concentrations of glucose (P , 0.05) and IGF-1 (P , 0.01) were lower in G98 than in G77 piglets. On the whole, 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.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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

Canario

Père

Tribout

et al. 2007

“…They also show that these mechanisms are strongly influenced by genetic factors so that selection for lean carcasses may lead to important changes in the functioning of basic endocrine systems that are necessary for a whole range of physiological regulations including responses to stress. For instance, cortisol concentrations have been shown to be the strongest biological predictor of the estimated breeding value for piglet survival (Leenhouwers et al, 2002), and this may be one factor explaining the high survival rate of Meishan piglets despite their larger litter size and smaller birth weight, as compared with Large White or Landrace (Legault and Caritez, 1982). A better understanding of these processes and the exploration of the molecular mechanisms underlying genetic variation (Ousova et al, 2004;GuyonnetDuperat et al, 2006;Murani et al, 2006) will allow to optimise selection for carcass composition and meat quality but spare basic endocrine mechanisms that are necessary for survival and adaptation.…”

Section: Discussionmentioning

confidence: 99%

Stress neuroendocrine profiles in five pig breeding lines and the relationship with carcass composition

Foury

Geverink²,

Gil³

et al. 2007

Stress neuroendocrine systems (hypothalamic-pituitary-adrenal axis and sympathetic nervous system) were studied in 100 female pigs from each of the five main genetic lines used in Europe for pork production: Pié train, Large White, Landrace, Duroc and Meishan. Levels of cortisol and catecholamines were measured in urine collected at the farm, after transportation to the slaughterhouse and the next morning before slaughter. With the exception of the Pié train line that showed intermediate levels of cortisol despite its extreme leanness, a significant positive relationship was found between basal cortisol levels and fatness, both across and within (except in Pié train and Duroc) lines. Basal cortisol levels were 2.46-fold higher in Meishan (20.46 ng/mg creatinine) than in Large White pigs (8.30 ng/mg creatinine), the two extreme breeds. Post-transportation levels were highest but proportional to basal levels, suggesting that the adrenal reactivity to adrenocorticotropic hormone is a major source of variability between lines. Levels of catecholamines were less variable between lines but correlated also with fatness, partlyviapartial correlations with cortisol levels. In serum collected at exsanguination, creatine kinase activity was correlated with muscularity across the five breeds. However, this was due to a much larger activity than expected in Pié train pigs, although all animals were negative for the allele of the ryanodine receptor gene responsible for stress sensitivity. Serum glucose levels were inversely related to fatness. These data show that the differences between breeds or lines can be utilised by cross-breeding and that this can lead to changes in stress hormones and in turn to some degree of changes in carcass traits.

“…Another example of the positive influence of stress hormones on robustness traits can be found in the work on newborn piglet survival by Leenhouwers et al (2002), who showed that piglet viability is a heritable and piglet-intrinsic trait. The only biological characteristics correlated (positively) with the estimated breeding value for piglet survival were the size of the adrenal glands and the concentration of cortisol in cord blood collected at birth.…”

Section: Cortisol Production and Robustnessmentioning

confidence: 99%

Breeding for robustness: the role of cortisol

Mormède

Foury

Terenina

et al. 2011

Robustness in farm animals was defined by Knap as 'the ability to combine a high production potential with resilience to stressors, allowing for unproblematic expression of a high production potential in a wide variety of environmental conditions'. The importance of robustness-related traits in breeding objectives is progressively increasing towards the production of animals with a high production level in a wide range of climatic conditions and production systems, together with a high level of animal welfare. Current strategies to increase robustness include selection for 'functional traits', such as skeletal and cardiovascular integrity, disease resistance and mortality in various stages. It is also possible to use global evaluation of sensitivity to the environment (e.g. reaction norm analysis or canalization), but these techniques are difficult to implement in practice. The hypothalamic-pituitaryadrenocortical (HPA) axis is the most important stress-responsive neuroendocrine system. Cortisol (or corticosterone) released by the adrenal cortices exerts a large range of effects on metabolism, the immune system, inflammatory processes and brain function, for example. Large individual variations have been described in the HPA axis activity with important physiopathological consequences. In terms of animal production, higher cortisol levels have negative effects on growth rate and feed efficiency and increase the fat/lean ratio of carcasses. On the contrary, cortisol has positive effects on traits related to robustness and adaptation. For instance, newborn survival was shown to be directly related to plasma cortisol levels at birth, resistance to bacteria and parasites are increased in animals selected for a higher HPA axis response to stress, and tolerance to heat stress is better in those animals that are able to mount a strong stress response. Intense selection for lean tissue growth during the last decades has concomitantly reduced cortisol production, which may be responsible for the negative effects of selection on piglet survival. One strategy to improve robustness is to select animals with higher HPA axis activity. Several sources of genetic polymorphism have been described in the HPA axis. Hormone production by the adrenal cortices under stimulation by adrenocorticotropin hormone is a major source of individual differences. Several candidate genes have been identified by genomic studies and are currently under investigation. Bioavailability of hormones as well as receptor and post-receptor mechanisms are also subject to individual variation. Integration of these different sources of genetic variability will allow the development of a model for marker-assisted selection to improve animal robustness without negative side effects on production traits.