Association of restriction fragment length polymorphisms of swine leucocyte antigen class I genes with production traits of Duroc and Hampshire boars

Summary. Restriction fragment length polymorphism analyses of swine leucocyte antigen (SLA) class I genes were performed on 70 Duroc and 38 Hampshire boars from the 1986-87 national performance tests of each breed in the USA. Few boars were inbred. Southern blotting and hybridization procedures were performed on genomic DNA, isolated from white blood cells, using Pvu II endonuclease and a swine major histocompatibility complex (MHC) class I probe. Durocs had an average of 11 restriction fragments, with the most common being in 63% of the boars and the least common appearing in only one boar. Hampshire boars had an average of 12 restriction fragments, with the most common appearing in 73% of the boars and the least common appearing in only one boar. Least squares procedures and stepwise regression methods were used to examine the association between DNA restriction fragments and the selection index (INDEX), average daily gain (ADG), average backfat thickness (BF), loin muscle area (LEA), and age at 104kg (DAY104). In the Duroc breed one DNA restriction fragment was associated with decreased INDEX ( P < 0.05) and decreased ADG ( P < 0.05) whereas two other fragments were associated with increased BF ( P < 0.05). In the Hampshire breed two restriction fragments were associated with an increase in INDEX ( P < 0.05). Cluster analyses were used to group pigs of each breed on the basis of similar RFLP patterns. One cluster group in the Duroc breed was associated with lower average INDEX values ( P < 0.05), greater average DAY104 ( P < 0.05), and a larger mean LEA ( P < 0.05). In the Hampshire breed one cluster group was associated with lower INDEX ( P < 0.05). These results suggest there may be an association between swine MHC class I genes and performance traits in swine. The use of SLA class I restriction fragments, as genetic markers, may have potential in the future for improving pig performance.     

Further Studies on the Suitability of Various Media Containing Antibacterial Antibiotics for the Enumeration of Moulds in Food and Food Environments

Oxytetracycline–glucose–yeast extract agar (OGYA), gentamicin–glucose–yeast extract agar (GGYA) with the antibiotic added separately or sterilized with the medium, chlortetracycline–Rose Bengal agar (CRA), chloramphenicol-streptomycin agar (PYA) and to a lesser extent, oxytetracycline–gentamicin–glucose–yeast extract agar (OGGYA) with or without Rose Bengal added, have been compared for the selective enumeration of moulds in foods. The results obtained from dried cereal products show that the media are almost equally productive and selective when applied to such foods, but Rose Bengal limits the size of mould colonies. When examining fresh proteinaceous foods, such as minced meat and chicken, CR agars and to a certain extent gentamicin-containing agars show the distinct advantage of being much more inhibitory towards the psychrotrophic Gram negative rods that predominate in the associated flora of such foods. Oxytetracycline–glucose–yeast extract agar lost its bacteriostatic properties when heavily challenged with proteinaceous substrates and/or incubated for longer periods at 37° or even at 25°. For such applications chloramphenicol was found to be the antibiotic of choice.     

Arrangement of sperm within the spermatheca of fleas, with remarks on sperm displacement

The arrangement of sperm within the spermatheca of the impregnated rabbit flea is described. The numerical superiority of the sperm injections from the numerous later matings suggests that a modified form of sperm displacement probably occurs in this species.