Genetic aspects regarding piglet losses and the maternal behaviour of sows. Part 1. Genetic analysis of piglet mortality and fertility traits in pigs.

In spite of the improvement in management and the breeding goal of increasing the number of piglets born alive, piglet mortality is still a substantial problem in pig breeding. The objective of the first part of the study was to estimate genetic parameters for different causes of piglet losses and to investigate the relationship to litter-size traits. Data were collected on a nucleus herd from January till December 2004. Records from 943 German Landrace sows with 1538 pure-bred litters and 13 971 individually weighted piglets were included. Four different causes of piglet losses (LOSS) were evaluated. Additional analysed traits were underweight and runting. Furthermore, the fertility traits number of piglets born alive, born in total and stillborn piglets as well as the individual birth and weaning weights were analysed. The different LOSS were treated as a binary trait and subsequently the heritabilities were estimated using a threshold model. The most important LOSS was crushing under the sow (12.4%). The survival rate and crushing had a heritability of h2 = 0.03. The fertility traits piglets born alive, born in total and stillborn piglets were analysed with a linear model and heritabilities rank from h2 = 0.05 (stillborn) to h2 = 0.10 (born alive). The estimated heritabilities for birth- and weaning weight were both h2 = 0.10. The genetic correlations between number of piglets born alive and each LOSS trait were analysed bivariately. Of all piglets born alive 84.3% survive the lactation period. Survival decreased with increasing litter size (rg = -0.54 up to -0.78) and the probability of being crushed under the sow increased.

Genetic aspects regarding piglet losses and the maternal behaviour of sows. Part 2. Genetic relationship between maternal behaviour in sows and piglet mortality.

The aim of the study was to analyse the genetic background of different traits to characterise the maternal behaviour of sows and to evaluate the relationship to different causes of piglet losses - increasing piglet survival due to higher maternal abilities of the sow. A total of 1538 purebred litters from 943 German Landrace sows in the year 2004 were available for data analysis. Around 13 971 individually earmarked piglets were included in the analyses. Maternal abilities were characterised through the sow's reaction to the separation from her litter during the first 24 h after farrowing, and on day 21 of lactation, the reaction towards the playback of a piglet's distress call and the reaction towards an unknown noise (music). In 1220 of these litters, the sows were also scored for aggressiveness in the group when regrouped before entering the farrowing crates. To describe fertility, the number of piglets born alive, stillborn piglets, number of piglets born in total and the individual birth weight were utilised. Different causes of piglet losses were evaluated as binary traits of the dam with survival rate, different definitions for crushing by the sow, being underweight and runts. The heritability for being aggressive in the group was h2 = 0.32 and for the behaviour traits during lactation, the heritabilities ranged from h2 = 0.06 to 0.14. The genetic correlations showed that more-reactive sows had fewer piglet losses.

Health conditions of growing-finishing pigs in fully-slatted pens and multi-surface systems.

The health status of finishing pigs was investigated in 97 farms with either fully-slatted pens (SF, n = 39) or littered multi-surface systems with outdoor yard (MS, n = 58). Pigs (11,194) were checked twice by one person at the beginning and the end of the fattening period in summer or winter. Animal health was determined by the presence of skin and tail lesions, lameness, coughing and sneezing. Housing and management practices were recorded by answering a detailed questionnaire. After merging health information with the questionnaire the data were analysed using generalised mixed linear models. Prevalence rates of health disorders were low (tail = 0.9%; skin = 2.6%; lameness = 0.6 %, coughing = 2.2 %; sneezing = 9.5 %). Pigs exposed to MS showed a lower odds ratio (OR) for tail (OR = 0.22; p < 0.0001) and skin lesions (OR = 0.29; p = 0.002) compared to pigs on SF (OR = 1.0). Conversely, pigs kept in MS had a 3.0 times higher risk of lameness than pigs on SF. No significant housing effects were found for any of the respiratory disorders. Health disorders were strongly affected by the random herd effect (p < 0.0001) indicating the impact of farm layout, management practices and motivational aspects for the animal health status at farm level.

Factors influencing somatic cell score in Swiss dairy production systems.

The aim of this study was to analyse the influence of fixed effects on somatic cell score (SCS) in Swiss dairy production. Monthly milk recording results were investigated against the background of changing housing conditions from tie-stall barns to loose housing systems. Zone, housing system and calving age within lactation number had a significant effect on SCS, as well as the covariables milk yield per day, fat and protein percentage and days in milk. Highest SCS was observed in cows of valley situated farms. Concerning housing system, best values were recorded in tie-stall barns (2.53). SCS was 0.08 higher during the changing period (2.61), and 0.12 higher in loose housing systems (2.65). SCS increased continuously with lactation number, but the differences between the age classes within lactation number were not significant. The lactation curves for SCS resembled inverted milk yield curves and were different between the first lactation on the one hand and higher lactations on the other hand.