J Ullmo, Le profit, París, 1969, p 51.

Evidence arising from the present study highlighted that neonatal teat access is linked with udder location. In Chapter 5, neonatal suckling behaviour was recorded and variation in suckling latency was not entirely explained by the birth condition of piglets or by maternal behaviour. The results of this study emphasized the role of teat location on the udder. Posterior and anterior teats located in the upper row were the most suckled; this behaviour seems to be a frequently recorded pattern (De Passille et al., 1988; Vasdal and Andersen, 2012). The time delay from birth to suckling and from the first contact with the mammary gland to suckling was also shorter when neonates suckled for the first time from a teat located in the posterior or anterior section. In Chapter 4, udder morphology trait measurements pointed out a similarity in the conformation of the teats located in the posterior and anterior part of the udder. In these two portions of the udder, teat length and diameter are smaller on average and, by observing the teat seeking behaviour, it seems that neonatal piglets suckle more easily from teats with small dimensions. In addition, teats located in the posterior and anterior part of the udder are also closer to the abdominal mid-line; this might suggest that the height above the pen floor or poor exposure of the lower row might prevent teat access. A comparison between suckled and un-suckled teats showed that piglets suckled for the first time more frequently from teats with larger inter-teat distance within the same row, allowing more space for the siblings to suckle. That trait is of vital importance in hyperprolific sows, where the fights over a teat increase with increased litter size (Milligan et al., 2001; Andersen et al., 2011). From our results, it seems that posterior teats also play an important role in colostrum intake but this assertion is not supported by previous study outcomes. However, a recent study showed that mammary gland productivity per se cannot be considered a factor affecting piglet distribution along the udder (Skok et al., 2013). From the literature it seems that in intensive farms piglets mainly suckle from the anterior-middle teats, whereas in wild boar it has been reported that piglets prefer posterior teats, where the leg provides a protection from competition (Fernández-Llario and Mateos-Quesada, 2005). Skok et al. (2013) suggested that selection for increased hindquarter muscularity could have altered piglet territoriality on the udder. In this thesis, piglet teat seeking behaviour was observed only until the first teat was suckled. It might be that piglets instinctively suckled first from a teat located in the rear part of the mammary gland as did their ancestors, but then found the anterior part safer or more productive. Another assumption is that anterior teats are

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easy to keep at the beginning of the farrowing because there is less competition, and later on piglets that started to suckle undisturbed from the front sections should have more energy to fight to keep the position. The results from our study showed that 65% of the time siblings suckled for the first time from the same teat as suckled by a previous littermate, and that 41% of the teats first suckled were located in the posterior part versus 33% in the anterior part of the udder. Teat order position is quickly settled; it has been reported that it becomes established around four hours after birth (McBride et al., 1965; Hemsworth et al., 1976). Another possible explanation for the lower weight gain of the piglets that suckle from the posterior teats could be explained by the different

physiological conformation of the mammary glands. Kim et al. (2000) and Nielsen et al. (2001) reported that posterior glands have lower weight than other glands and they found a correlation between wet weight and piglet weight gain. Moreover, posterior glands are prone to loose attachment and become firm, which is likely to occur with increasing parity number (Aziz et al., 1995). Phenotypic correlations of udder traits with sow

reproductive and productive traits showed that litter size and litter weight gain at ten days was negatively correlated with teat diameter and length and tended to be negatively correlated with larger udder dimensions. These results indicate that large udder size, impairs teat access, affecting piglet performance. This statement is valid without considering the inter-teat distance from the same row, since the results presented in the suckling behaviour study showed an associated with the teat suckled during the first contact with the udder and this traits, but later on the genetic investigation the outcomes showed negative correlation between this traits and the performance at ten days. The evidence presented in th suckling behaviour might be biased by other factors, such as the distance of the teats from the abdominal mid line, the safety of the position, the odour of the udder, the grounding of the mother as has been previously proved. Nevertheless considering also the negative relationship between this traits and the number of stillborn it is advisable to include this traits maybe with a single measurement from the first teat to the last ones in the same row.

However, estimated colostrum IgG concentration was not related with piglet performance at ten days in this study, possibly because infectious disease challenge was not high in this early stage.

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Overall, the outcomes of this research have produced a detailed description of the traits and a scientific base that accounts for modern hyperprolific sows and highlights the main causes of variation. In summary, a sow with a good quality udder must have a sufficient number of teats positioned in two parallel rows, equidistant within the same row and close to the abdominal mid-line. Furthermore, it is now possible to state that the better maternal qualities of the Meidam breed include also the udder morphology traits.

Altogether, these results can be summarised to distinguish between two main shapes: the parallel rows and the arch rows. This simplification allows a quick interpretation of the data and highlights the main characteristics that determine a good quality udder (Figure 8.1).

Figure 8. 1 Udder morphology shape A: average udder morphology, “arch shape”. B: good udder

morphology: “parallel shape”