Association of BoLA-DRB3 alleles with tick-borne disease tolerance in dairy cattle in a tropical environment.

Tick-borne disease is one of the most harmful tropical diseases in dairy production. Selection of dairy cows for tolerance to tick-borne disease is a challenging concept for dairy breeders in the tropics. The objectives of this study were (1) to detect specific tick-borne pathogen in cattle of different genetics and (2) to examine the polymorphisms of DRB3.2 alleles in Thai dairy cattle and find the allelic association with tick-borne disease tolerance. Specific primers to Anaplasma marginale (AM), Babesia bigemina (BG) and Babesia bovis (BB) were used to detect the infections by PCR. The results showed that the high proportion of infections were found in Bos indicus (Sahiwal, n=95) and crossbred Holstein × Zebu (75:25 Holstein:Zebu, n=101), compared to high Holstein fraction crossbreed (≥ 87.5% Holstein, n=187). The proportion of triple infections was also highly found in high Holstein fractions crossbreed. This study confirmed that Zebuine (Bos indicus) had a higher degree of tolerance, even when infected by tick-borne pathogens, compared to high Holstein fraction crossbred. The associated alleles of DRB3.2 for tick-borne pathogen infection tolerance were found: DRB3*14 and *41 were found to be tolerant to A. marginale; *14 to B. bovis; and *10 and *51 to B. bigemina. These tolerance alleles could be used as potential markers for selection in dairy genetic evaluation. The associated alleles for susceptibility were also found: *2 was found to be susceptible to A. marginale; *3 and *16 to B. bovis; and *20 to B. bigemina. These susceptibility alleles could be used as markers for culling, and selection favoring susceptibility alleles should be considered to maintain heterozygote advantage and pathogen-specific memories in the herd.

Separation of bovine spermatozoa proteins using 2D-PAGE revealed the relationship between tektin-4 expression patterns and spermatozoa motility.

Poor semen quality has long been associated with bull infertility. However, the molecular basis in spermatozoa cells underlying the mechanisms of bull infertility remain unknown. The purpose of this study was to determine whether there is any protein in bovine spermatozoa related to semen quality. Semen samples from 18 Brahman bulls, 3 to 10 yrs of age, were assessed for semen quality in terms of spermatozoa motility and spermatozoa morphology. Spermatozoa extracts were separated using 2D-PAGE followed by staining with Coomassie blue. At least one duplicate gel was performed for each sample. Each gel was scanned with an ImageScanner System and analyzed for spots by ImageMaster 2D platinum software. The related protein spot(s) with semen quality was cut from the gel and identified by LC MS/MS. The results showed that at least 600 protein spots were detected in the spermatozoa extracts of the Brahman bulls. Of all these spots, there were 3 of 56 kDa at pI 6.4, 6.6 and 6.8 (Z(1), Z(2) and Z(3), respectively) that clearly showed different expression pattern among 18 Brahman bulls. Of 18 bulls (a) five showed the presence of spot Z(1) and Z(2) (pattern A) (b) one of spot Z(3) (pattern B) (c) five of spot Z(2) and Z(3) (pattern C) (d) one of spot Z(1) (pattern D) and (e) six of spot Z(2) (pattern E). Identification of spot Z(1), Z(2) and Z(3) by LC MS/MS had a similar result as matched to the tektin-4 protein of Bos taurus with a respective score of 171, 557 and 591. The statistical analysis of the 56 kDa protein patterns, tektin-4, indicated a significant effect on spermatozoa motility (P < 0.05) albeit non-significant on spermatozoa morphology. The bulls which showed pattern A had a higher percentage of spermatozoa motility than pattern E (P < 0.05) and not different from pattern C (P > 0.05). The statistical analysis also revealed that the presence of spot Z(1) had an effect on the percentage of spermatozoa motility (P < 0.01), whereas the presence of spot Z(2) and Z(3) had no effect (P > 0.05). The correlation coefficient between the relative protein content of spot Z(1) and the percentage of spermatozoa motility was 0.49. Our study demonstrates that the expression patterns of tektin-4 were a proxy for an effect on spermatozoa motility and consequently bull infertility. It may be that these protein patterns can be used as markers for improving bovine reproduction.

Detection of bovine leukocyte antigen DRB3 alleles as candidate markers for clinical mastitis resistance in Holstein x Zebu.

Bovine leukocyte antigen DRB3 alleles from Holstein x Zebu crossbred dairy cows (n = 409) were analyzed using the PCR-RFLP technique. Exon II of DRB3 was amplified using locus-specific primers (HLO30/HLO32), followed by digestion with 3 restriction enzymes (RsaI, BstyI, and HaeIII). Forty alleles were found with frequency ranging from 0.005 to 0.139. The most frequently detected alleles of Holstein x Zebu were DRB3*16, *51, *23, *11, *8, and *1, accounting for 61.12% of the alleles in the population. Detection of candidate alleles for clinical mastitis occurrence was performed by logistic regression. It was found that percentage of Holstein fraction in crossbred cows had a nonsignificant effect (P > 0.05). However, parity had a significant effect on mastitis occurrence. In addition, DRB3*1 and *52 were the most associated with the occurrence of clinical mastitis, whereas *15, *51, and *22 were associated with resistance in crossbred populations. This is the first report of association of DRB3*15 and *51 with mastitis resistance. The association was validated by examining the candidate alleles in another commercial population. Highly susceptible (n = 43) and resistant (n = 42) groups of Holstein x Zebu cows were investigated. The result confirmed that DRB3*1 and *52 could be considered as susceptibility alleles, whereas *15, *51, and *22 could be considered as resistant alleles in Holstein x Zebu raised under tropical conditions. In addition, allele effects on 305-d milk production were estimated by BLUP. It was shown that most alleles associated with high clinical mastitis occurrence were related to increased milk yield. This study revealed that allele DRB3*10 had the greatest effect on increasing milk yield with moderate resistance to clinical mastitis, which could be used as a potential marker for selection in dairy genetic evaluation.

Influence of amount and type of dietary fat on deposition, adipocyte count and iodine number of abdominal fat in broiler chickens.

This study described the relation between the type and amount of dietary fat on the deposition of abdominal fat by broiler chickens. It was hypothesized that at higher fat intakes, the well-known lowering effect of polyunsaturated fatty acids on the deposition of abdominal fat would be diminished. Experimental diets were formulated to contain three levels of added fat (3%, 6% and 9%). Each level had different proportions of the saturated fatty acids (SFA) and unsaturated fatty acids (UFA) by installing the ratios of 1:1, 1:2, 1:3, 1:4 and 1:5 with the use of tallow and soybean oil. Arbor Acres chicks, aged 7 days, were fed one of the 15 experimental diets until they were aged 42 days. Feed and water were provided ad libitum. There was no systematic effect of the dietary fat type and the amount on the weight gain and the feed intake. The lowest SFA:UFA ratio of 1:5 produced the lowest feed conversion rates, irrespective of the amount of the fat in the diet. The abdominal fat deposition was similar in the birds fed on diets containing either 3% or 6% added fat, but deposition was lower than in those fed 9% fat. A decrease in the SFA:UFA ratio of the diet was associated with a dose-dependent decrease in abdominal fat, irrespective of the amount of fat in the diet. This observation leads to the rejection of the hypothesis stated above. A decrease in the dietary SFA:UFA from 1:1 to 1:4 caused a decrease in the number of the fat cells per surface unit of breast meat. It is concluded that an increased intake of soybean oil at the expense of tallow reduced the abdominal fat deposition and the number of fat cells in the breast meat of broiler chickens.