A note on causes of boar removal in Cuban pig farms

M J Acosta and M Rueda

Swine Research Institute. PO Box No. 1, Punta Brava. La Habana, Cuba
mjesus@iip.co.cu   ;   mihermamrs28@yahoo.com.mx

Abstract

Main causes of boar removal were studied in Cuban commercial pig farms. There was a selection at random of 16 pig breeding farms corresponding to the pig enterprises of Matanzas, Holguín, Granma, and Santiago de Cuba. A total of 540 breeding boars from the L35, CC21, H x L35, and CC21 x L35 pig genotypes and on average 28 months of age were evaluated. Breeding system was by natural mating. Boar herd size (small, 8 and 27 or large, 47 and 58 boars) and causes of boar removal (end of useful life, non reproductive and reproductive origin) were analyzed according to a 2x3 arrangement.

Dam/sire ratio (15.0 to 16.8) was lower than that conceived (17.0). Overall, causes of boar removal due to reproductive characteristics accounted for 43.2%, whereas non reproductive characteristics and end of useful life of boars caused sire replacement to 30.3 and 26.5% respectively. Neither herd size nor causes of boar removal were significantly different (P>0.05) among the examined pig breeding farms.

It is suggested that performance of boar removal index should periodically be conducted in all pig breeding farms belonging to Cuban commercial pig farms.

Key words: Management, pigs, reproduction

Introduction

Boars play an important role in pig farms, since they contribute near 50% of the productive results (Leman and Rodefer 1976; Flowers 1997,  2002; Langeduk 2001). The boar is a very sensitive animal to abrupt changes in their management, which in the end, determine changes in spermatic quality. This is the reason why it should be tried to achieve the greatest stability in animal life from the point of view of boar management.

From the practical point of view, it is important to have fertile boars showing a good spermatic production, as much in quality as in quantity, independently of the type of mating that they do, although this aspect is more important when artificial insemination is used for reproduction purposes in pig production (Rutten et al 2000; Wilson 2002; Robinson and Buhr 2005). On the other hand, although under artificial insemination or direct mating regime, the major percentage of boar removal is due to spermatic pathologies, sires are usually eliminated due to other causes, such as foot diseases and low sexual libido (Flowers 1997; Arias et al 2004).

In Cuba, the practical rule for boar removal is not stud replacement when another young animal is selected from the point of view of an outstanding estimated breeding value (for review, see Robinson and Buhr 2005). In this connection sire arrival to Cuban pig farms for male reproductive activity is according to the boar replacement index recommended, which would not surpass 40% per annum (IIP 2001).

If comparison is made to studies on waste of sows and its causes which is systematically carried out in other countries (Langeduk 2001; Stalder et al 2004) and in Cuba (Pujals 1985; Calderón et al 1988), little it is known on the exact nature of sire removal (Rutten et al 2000; Wilson 2002). This is not an exception in Cuba, even from the point of view of intensive conditions of pig production (Caballero et al 2001). This work was designed with the objective of studying the main causes of replacement of sires that are used in the genetic program of national crossing in domestic swinish farms.

Materials and methods 

Main causes of boar removal in 16 pig breeding farm belonging to four out of the 13 large-scale Cuban enterprises were evaluated during one year-production cycle. The enterprises were selected at random, and there were those corresponding to Matanzas, Holguín, Granma and Santiago de Cuba, and a total of 540 boars from the L35, CC21, H x L35, D x L35 y CC21 x L35 genotypes and on average 28 months of age were evaluated. Breeding system was by breeding in natura. Boar herd size (small, 18 and large, 53) and causes of boar removal (end of useful life, non reproductive and reproductive origin) were analyzed according to a 2x3 arrangement. As defined by Cuban national standards (IIP 2001), boar must be replaced when, as a result of periodical reproductive evaluations, a decrease in their semen quality, andrological status or fertility was noted. IIP (2001) recommendations for boar removal include also a prolonged lack of libido in sires, even after being subjected to reproductive inactivity, and to impairment of body condition, such as foot lesions. The characteristics of the examined enterprises are shown in table 1.

Animal management and feeding were those recommended by Cuban standards of pig production (IIP 2001). The breeding system used was by natural breeding. Contrasts of means were done by analysis of variance, following Steel et al (1997) recommendations for comparison of causes of boar removal, between pig enterprises with small (Matanzas and Granma, 27 and 8) and big (Santiago de Cuba and Holguín, 58 and 47) boar herd size. An analysis of proportions was undertaken to compare boar removal per cent among the four evaluated pig enterprises.

Results and discussion 

The dam/sire ratios, found ranged from 15.0 to 16.8, which were lower than the 17.0. recommended in Cuban large-scale pig production enterprises (IIP 2001) and by others (Leman and Rodeffer 1976). In fact, these results indicate an under-exploitation of reproductive females in many of the pig farms evaluated.

Table 2 shows a comparison among the four pig enterprises from the point of view of boar removal per cent. It was observed that in the hot environment of Cuba, boar removal in Matanzas pig farms (58.4%) and Granma (73.3%) was significantly (P <0.001) higher than that of Santiago de Cuba (24.2%) and Holguín (13.4%), indicating that animal management recommendations were very differently applied in different places of the country which were examined in the present study. It has been recommended that the Cuban boar replacement index must be fixed in 40% (IIP 2001). In this connection, information here in provided, could indicate that the management of removal of sires in the above mentioned farms was very variable.

Overall, causes of boar removal due to reproductive characteristics accounted for 43.2%, whereas non reproductive characteristics and end of useful life of boars caused sire replacement of  30.3 and 26.5% respectively. A detailed record of causes of boar removal is listed in table 3. Different authors (Córdova et at 2001; Robinson and Buhr 2005) have claimed that sires should be replaced as soon as sperm evaluation, or andrological and fertility per cent fall to undesirable values. In this context, it has been argued that given the adequate food to a boar is a very important factor for improving its optimal reproductive capacity (Wilson 2002; Wilson et al 2004); and therefore, avoiding shortage of useful work before its logical end. Feeding management in this investigation was not recorded, and it was not known its implication on the results shown in table 3. In this context, other non reproductive factors causing boar removal, such as foot diseases and arthritis, had no precedent in Cuban reports concerning boar management. It is well known that environmental conditions can influence management of breeding boars and its productivity (Wettermann et al 1979; Kunavongkrit et al 2005). The origin of foot diseases could be caused by unsuitable conditions for boar housing, rather than others such as those of nutritional origin.

Details of the analysis of variance conducted in the above described values, from the point of view of boar herd size is shown in table 4. As to be expected a great variability was found in all the evaluated indices. Probably this was the reason to understand a no significant (P>0.05) interaction in the determined measurements. Even though, 44.6% of boar removal was near the Cuban standard when large boar herds (P<0.05) were examined, as compared to small boar herds (8.4%). These results indicated that either non reproductive or reproductive causes were predominant in the four evaluated pig enterprises.

According to the present evaluation, replacement of sire in the examined Cuban pig farms was above the recommended indices for those conditions that are adequate for industrial, large-scale pig production. Some could be the causes for a sub-optimal boar performance, which should be matter of further analyses, such as housing (Leman and Rodeffer 1976; Corcuera et al 2002), feeding (Pollman 2002; Wilson 2002) and environmental temperature (Wettermann et al 1979; Kunavongkrit et al 2005), among others. It is also recommended to analyze the status of housing and boar management, as well as to undertake, in periodical manner, the spermatic evaluation of breeding boars.

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Received 26 February 2008; Accepted 27 January 2009; Published 18 April 2009

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