Sequence Variation Of the α-Lactalbumin Gene In Holstein and Nellore Cows

The α-lactalbumin is a subunit of lactose-synthase, an enzyme responsible for lactose production, a disaccharide that influences milk production. Sequence variations of bovine α -lactalbumin have been associated with differences in milk yield. This study aimed to analyze allelic frequency differences at position ? 1689 (g. A > G) and + 15 (g. A > G) of the α-lactalbumin gene in Holstein (Bos taurus) and Nellore (Bos indicus) cows. Blood samples were analyzed from 34 Holstein, 104 Nellore, and 99 Dairy Nellore cows using PCR-RFLP. The different RFLP patterns were sequenced and a novel sequence variation on nucleotide ? 46 was identified. An adenine at this position was designated as the A allele and a guanine was designated B allele. The frequencies of alleles A ? 1689, A ? 46, and A + 15 differed between Holstein and both Nellore breeds. The results show that differences in α-lactalbumin allelic variants in the 5′-flanking and the 5′-UTR region might be associated with differences in milk production between Holstein cows and cows from Nellore breeds. However, the lack of difference between Nellore and Dairy Nellore suggests that other sequence variantions that regulate milk production might be responsible for the selection of Dairy Nellore cows with superior milk production.     

Genetic polymorphism of the kappa-casein gene in Brazilian cattle

Frequencies of kappa-casein gene alleles were determined in 1316 animals from the Brazilian Bos indicus genetic groups (Sindhi cows, Gyr sires, Gyr cows, Guzerat sires, Guzerat cows, Nellore sires, and Gyr x Holstein crossbreds) by means of polymerase chain reaction-restriction fragment length polymorphism analysis using two independent restriction nucleases (Hinf I and HaeIII). The genotyping of kappa-casein alleles (A and B) is of practical importance, since the B allele is found to correlate with commercially valuable parameters of cheese yielding efficiency. The frequencies of the B allele of kappa-casein among breeds ranged from 0.01 to 0.30. The Sindhi breed had the highest frequency for the B allele (0.30), while the frequencies of this allele in other breeds ranged from 0.01 to 0.18. A wide variation in the B allele frequency among B. indicus breeds was found suggesting that molecular selection for animals carrying the B allele could impact breeding programs for dairy production.     

DGAT1 K232A polymorphism in Brazilian cattle breeds

Recent reports identified DGAT1 (EC 2.3.1.20) harboring a lysine to alanine substitution (K232A) as a candidate gene with a strong effect on milk production traits. Our objective was to estimate the frequency of the DGAT1 K232A polymorphism in the main Zebu and Taurine breeds in Brazil as well as in Zebu x Taurine crossbreds as a potential QTL for marker-assisted selection. Samples of 331 animals from the main Brazilian breeds, Nellore, Guzerat, Red Sindhi, Gyr, Holstein, and Gyr x Holstein F1 were genotyped for DGAT1 K232A polymorphism (A and K alleles) using the PCR-RFLP technique. The highest frequency of the A allele was found in the Holstein sample (73%) followed by Gyr x Holstein F1 (39%). Gyr and Red Sindhi showed low frequencies of A alleles (4 and 2.5%, respectively). The A allele was not found in the Nellore and Guzerat samples. Our results could be used to guide association studies between this locus and milk traits in these breeds.     

The impact of a leptin gene SNP on beef calf weaning weights

Prior research indicates that a SNP at position 305 of exon 2 in the leptin gene affects milk production in dairy cows. Dairy cows with at least one copy of the T allele have been shown to have higher milk production than CC cows. If that effect carries over to beef breeds, it is reasonable to expect that CT and TT beef cows will wean heavier calves than CC beef cows. We tested this hypothesis for a herd of mixed breed cows using anova. Results indicated that both crossbred CT and TT beef cows wean significantly heavier beef calves than CC crossbred beef cows. A lack of observations generally hinders detection of significance in other breeds. However, two other comparisons were found to be significant. The results suggest further investigation into the link between leptin genotype and calf weaning weights. Aside from interest to animal scientists, these results have the potential to alter mating and replacement selection decisions by cow-calf producers, given the importance of weaning weights on profitability.     

Comparative gene frequencies of nucleoside phosphorylase from cattle of Bos taurus and Bos indicus derivation in Brazil

1. Two nucleoside phosphorylase (NP) phenotypes were detected in 844 animals from four distinct genetic groups of Bos taurus and Bos indicus derivation. 2. Bos indicus breeds like Guzerat (Kankrej), Gir, Nellore (Ongole) and Indubrazil presented an NP-H frequency of 1.00, 0.928, 0.776 and 0.754 respectively, while the Canchim breed, a Bos taurus-Bos indicus crossbred cattle (5/8 Charolais-3/8 Zebu) presented a frequency of 0.372. 3. The high frequency detected from the NP-H allele in the Bos indicus breeds strongly suggests that this enzyme is a genetic marker for cattle and that it probably has a very high frequency in all Indian breeds.     

Associations between two novel rSNPs in 5'-flanking region of the bovine casein gene cluster and milk performance traits

Ten evolutionary conservative sequences with high identity level to homological sequences in other mammal species were revealed in 5'-flanking region of casein's genes cluster. Five novel SNPs located inside of the evolutionary conservative regions were identified. The binding sites were revealed to be present in one allelic variant of four detected SNPs. So these SNPs were considered as rSNPs. Significant differences of allelic frequencies were revealed between beef cow's group and dairy cow's group in two rSNPs (NCE4, NCE7, p<0.001). Different alleles of those two rSNPs were shown to be associated with some milk performance traits in Black-and-White Holstein dairy cows. Significant difference of protein percentage has been found between cows with G/G and A/A genotypes (P<0.05) and A/G and A/A genotypes (P<0.05) for NCE4 polymorphism. The groups of animals with genotypes G/G and A/G for NCE7 polymorphism were significantly different in milk yield at the first lactation (kg) (P<0.01), milk fat yield (kg) (P<0.05) and milk protein yield (kg) (P<0.01). For the last trait the difference was significant also between cows with genotypes G/G and A/A for rSNP NCE7 (P<0.05).     

Differences between Brahman and Holstein cows in response to estrus synchronization,superovulation and resistance of embryos to heat shock

Embryos from Bos indicus are more resistant to elevated culture temperature (i.e. heat shock) than embryos from some Bos taurus breeds. The present experiment was designed to determine if Brahman embryos have greater resistance to heat shock than Holstein embryos at a stage in development before the embryonic genome was fully activated. A second objective was to test breed effects on estrus synchronization and superovulation responses. A total of 29 Brahman and 24 Holstein cows were subjected to estrus synchronization using gonadotropin releasing hormone (GnRH) and prostaglandin F2alpha (PGF2alpha) superovulation. Embryos were collected at 48 h and day 5 after insemination. There was a tendency for a lower proportion of Brahmans to be detected in standing estrus than Holsteins. There were no differences between breeds in the proportion of cows detected in estrus using both tailpaint and standing estrus as criteria or in interval from PGF2alpha to estrus. The degree of synchrony in estrus was greater for Brahmans. Superovulation response was generally similar between breeds. At 48 h after insemination, there was a tendency for a greater proportion of Brahman oocytes to have undergone cleavage. Uncleaved oocytes were cultured for an additional 24 h-at this time, cleavage rate was similar between breeds. When embryos reached the 2-4-cell stage, they were heat-shocked for 4.5 h at 41 degrees C. This heat shock reduced the proportion of embryos that developed to the blastocyst stage but there was no breedxtreatment interaction. At day 5 after insemination, the number of embryos recovered was too low to allow comparison of breed effects. In conclusion, genetic effects on cellular thermotolerance that make Brahman embryos more resistant to heat shock are not expressed at the 2-4-cell stage. There were few differences between Brahman and Holstein in response to estrus synchronization and superovulation. The fact that cleavage tended to occur earlier in Brahman than Holstein embryos suggests breed differences in timing of ovulation, fertilization or events leading to cleavage.     

Effect of pregnancy on the genetic evaluation of dairy cattle

We investigated the effect of stage of pregnancy on estimates of breeding values for milk yield and milk persistency in Gyr and Holstein dairy cattle in Brazil. Test-day milk yield records were analyzed using random regression models with or without the effect of pregnancy. Models were compared using residual variances, heritabilities, rank correlations of estimated breeding values of bulls and cows, and number of nonpregnant cows in the top 200 for milk yield and milk persistency. The estimates of residual variance and heritabilities obtained with the models with or without the effect of pregnancy were similar for the two breeds. Inclusion of the effect of pregnancy in genetic evaluation models for these populations did not affect the ranking of cows and sires based on their predicted breeding values for 305-day cumulative milk yield. In contrast, when we examined persistency of milk yield, lack of adjustment for the effect of pregnancy overestimated breeding values of nonpregnant cows and cows with a long days open period and underestimated breeding values of cows with a short days open period. We recommend that models include the effect of days of pregnancy for estimation of adjustment factors for the effect of pregnancy in genetic evaluations of Dairy Gyr and Holstein cattle.     

The study of the SNP in the corticotropin-releasing hormone gene (exon 2) and milk production traits in cattle

The aim of this study was estimate the relations between CRH C22G and milk production traits (milk yield, yield of protein and fat, content of protein and fat in milk). The study was carried on 169 Polish Holstein-Friesian strain Red-and-White cows kept in the south-western region of Poland. The CRH C22G (exon 2) polymorphisms were detected using PCR-RFLP method. The genotype and allele frequencies were estimated and they were as follows: CC - 0.89, CG - 0.09, GG - 0.02; C - 0.93, G - 0.07. Statistically significant (P < or = 0.05) associations between CRH C22G genotypes and milk production traits like milk yield and protein yield in the second lactation were found. Moreover, the obtained results should be verified by conducting research on a larger group of animals and various cattle breeds.     

Single nucleotide polymorphisms, haplotypes and combined genotypes of LAP3 gene in bovine and their association with milk production traits

Leucine aminopeptidase 3 (LAP3) is an aminopeptidase which catalyses the removal of N-terminal amino acids and is involved in protein maturation and degradation. In this study, we detected the polymorphisms of LAP3 gene by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing methods in 916 individuals from three Chinese cattle breeds including Chinese Holstein, Luxi Yellow and Bohai Black. One novel single nucleotide polymorphism (SNP) (g.24564G>A ss196003366) and four previously deposited SNPs in the GenBank database (g.24794T>G, g.24803T>C, g.24846T>C, g.25415T>C) were detected. Three of the SNPs (g.24794T>G, g.24803T>C, g.24846T>C) were firstly found to be linked completely and regarded as a SNP g.24794M>N by PCR-SSCP and DNA sequencing in the tested breeds. The allelic frequencies and genetic indices of the SNPs were different in three Chinese cattle populations. The SNPs and their genetic effects on milk production traits in Chinese Holsteins were evaluated. Least squares analysis showed that cows with genotype MM had higher fat percentage and protein percentage than genotype NN (P<0.05); and the cows with g.25415T>C-CC genotype had higher protein rate than ones with TT genotype (P<0.05). In addition, eight haplotypes and 23 combined genotypes were identified based on the nine genotypes and the association between combined genotypes and milk production traits were analyzed. Statistic results showed that the cows with genotype combination MAT/MGC have higher protein and fat rate and lower SCS. Our finding demonstrated that the LAP3 gene possibly contributed to conducting association analysis and can be used as molecular marker in milk production traits and other performance for animal breeding.     

Three novel SNPs of the bovine Tf gene in Chinese native cattle and their associations with milk production traits

Transferrin (Tf) is a β-globulin protein that transports iron ions in mammalian cells. It contributes to innate immunity to microbial pathogens, primarily by limiting microbial access to iron. Thus, polymorphisms present in bovine Tf could potentially underlie inherited differences in mastitis resistance and milk production traits. We detected three novel single-nucleotide polymorphisms of the Tf gene in Chinese native cattle by screening for genetic variation of Tf in 751 individuals of three Chinese cattle breeds, namely China Holstein, Luxi Yellow and Bohai Black, using PCR-RFLP and DNA sequencing techniques. The three new SNPs, g.-1748G>A ss250608649, g.13942T>C ss250608650, and g.14037A>G ss250608651, had allele frequencies of 85.9, 86.3 and 92.5%, 64.5, 73.3 and 65.0%, and 67.6, 73.7 and 60.0%, respectively. SNP g.-1748G>A was located in the 5' flanking region of Tf. SNP g.14037A>G was located in intron 8 of Tf. SNP g.13942T>C, located in exon 8 of Tf, was a synonymous mutation (TTA > CTA), encoding a leucine (326 aa) in the Tf protein. Associations of the Tf SNPs with milk traits were also analyzed. Significant (P < 0.05) relationships among the Tf polymorphisms, somatic cell scores (SCS), and milk productive traits were observed. Cows with genotypes TT (g.13942T>C), GG (g.-1748G>A) and AG (g.14037A>G) had a lower SCS and higher protein levels and 305-day milk yield. Nineteen combinations of different haplotypes from the three SNPs were identified in Chinese Holstein cattle. The haplotype combination ATA/GCA, GCA/GCA and GCG/ GTA was dominant in cows with a lower SCS, a higher protein level and a higher 305-day milk yield, respectively. Moreover, the gene expression level of Tf was higher in mastitis-affected mammary tissues than in normal mammary tissues. These results suggest that the Tf gene affects milk production, as well as mastitis-resistance traits, in Chinese Holsteins.     

Suitability of cross-bred cows for organic farms based on cross-breeding effects on production and functional traits

Data from 113 Dutch organic farms were analysed to determine the effect of cross-breeding on production and functional traits. In total, data on 33 788 lactations between January 2003 and February 2009 from 15 015 cows were available. Holstein–Friesian pure-bred cows produced most kg of milk in 305 days, but with the lowest percentages of fat and protein of all pure-bred cows in the data set. Cross-breeding Holstein dairy cows with other breeds (Brown Swiss, Dutch Friesian, Groningen White Headed, Jersey, Meuse Rhine Yssel, Montbéliarde or Fleckvieh) decreased milk production, but improved fertility and udder health in most cross-bred animals. In most breeds, heterosis had a significant effect (P < 0.05) on milk (kg in 305 days), fat and protein-corrected milk production (kg in 305 days) and calving interval (CI) in the favourable direction (i.e. more milk, shorter CI), but unfavourably for somatic cell count (higher cell count). Recombination was unfavourable for the milk production traits, but favourable for the functional traits (fertility and udder health). Farm characteristics, like soil type or housing system, affected the regression coefficients on breed components significantly. The effect of the Holstein breed on milk yield was twice as large in cubicle housing as in other housing systems. Jerseys had a negative effect on fertility only on farms on sandy soils. Hence, breed effects differ across farming systems in the organic farming and farmers can use such information to dovetail their farming system with the type of cow they use.     

Growth and reproductive development from weaning through 20 months of age among breeds of bulls in subtropical Florida

To determine the effect of breed on growth and reproductive development, weaned bulls in each of 2 yr were managed as a single group for approximately a year. In Year 1, the study group consisted of 24 Angus, 24 Brahman, 20 Hereford and 14 Senepol bulls, while in Year 2, it contained 25 Angus, 17 Brahman. 13 Romosinuano and 9 Nellore x Brahman bulls. Body and testicular growth measurements were recorded at 6-wk intervals. At approximately 1 yr of age and quarterly thereafter (4 periods), bulls were evaluated for libido, pubertal status, and GnRH-induced LH and testosterone secretion. Significant breed-by-age interactions occurred for most growth measurements. Brahman bulls (Bos indicus ) were (P < 0.05) older and heavier at puberty than Angus, Hereford, Senepol and Romosinuano bulls (Bos taurus ). Libido scores were lowest for Brahman and Nell ore x Brahman bulls (Bos indicus ). highest for Angus and Hereford bulls (temperate Bos taurus breeds) and intermediate for Senepol and Romosinuano bulls (tropical Bos taurus breeds; P < 0.05). Differences were not consistent among breeds or between years for GnRH-induced LH secretion. In both years, basal testosterone concentrations and areas under the GnRH-induced testosterone curve were higher (P < 0.05) for Angus and Hereford bulls (temperate breeds) than for Brahman, Senepol, Romosinuano and Nellore x Brahman bulls (tropical breeds). In conclusion, reproductive development of Senepol and Romosinuano bulls (tropical Bos taurus breeds) was more similar to Angus and Hereford bulls (temperate Bos taurus breeds) than to Brahman and Nellore x Brahman bulls (Bos indicus ).     

Use of F1 progeny of HolsteinxZebu cross cattle as oocyte donors for in vitro embryo production and gene microinjection

This study was designed to determine the possibility of using F1 crossbreed cattle (Holstein x Zebu) as donors of oocytes for in vitro fertilization (IVF) and for pronuclear gene microinjection into in vitro-produced embryos. In the first part of the experiment oocytes from Bos taurus (Holstein), Bos indicus (Zebu) and F1 crossbred Bos taurus x Bos indicus (Holstein x Zebu) genotypes were inseminated with Bos taurus (Holstein) semen and were allocated for in vitro embryo production using conventional IVF procedures. No differences were observed on the in vitro maturation (IVM) rates between breeds (Holstein x Holstein:85%, Zebu x Holstein:84% and Zebu x Holstein x Holstein:88%). Holstein cows yielded the highest number of cumulus oocyte complexes (6.8 per ovary) for in vitro maturation, differing (P<0.05) from Zebu x Holstein and Zebu x Holstein x Holstein F1 by 5.1 and 5.8, respectively. However, the Holstein breed also yielded the lowest percentage of cleavage (45.1 vs 71.9% for Zebu x Holstein and 65.1% for Zebu x Holstein x Holstein). Of the 3 genotypes, the hybrid F1 breed was the most efficient source of oocytes for the production of embryos capable of reaching morulae and blastocyst stages (76 250 ; P< 0.001). In the second part of the study, 599 oocytes from the F1 breed were fertilized in vitro, 1 group of 150 oocytes was used for the determination of the optimal pronuclear visualization period. The highest number of oocytes with 2 pronuclei was observed between 24 to 28 h after IVF (27 to 42%). The remaining 399 oocytes were microinjected with a gene construct bearing the bacterial lacZ gene as the reporter for gene expression. Survival of embryos to microinjection was 73.8%, and 45.5% of them (50 110 ) cleaved in culture. Of the microinjected embryos, 1 out of 50 showed beta-galactosidase activity. These findings indicate that a tropical crossbreed of cattle (Zebu x Holstein x Holstein) can be used as a source of oocytes for IVF programs and gene microinjection studies.     

Correction: Periconceptional Heat Stress of Holstein Dams Is Associated with Differences in Daughter Milk Production and Composition during Multiple Lactations

The fertility of lactating Holstein cows is severely reduced during periods of heat stress. Despite this reduction in fertility, however, some inseminations conducted during heat stress result in successful pregnancies from which heifer calves are born. Many of these heifer calves are retained and raised to enter the milking herd as replacement animals. Heat stress experienced by these females around the time they were conceived may confer long-lasting effects that alter subsequent milk production capacity. The objective of this study was to examine the relationship between periconceptional heat stress and subsequent milk production of primiparous cows. National Dairy Herd Improvement Association data was obtained from Dairy Records Management Systems. Records included Holstein cows that had completed at least one lactation in one of three states with large populations of dairy cattle and which are known for having hot, humid summers: Georgia, Florida or Texas. Dates of conception were calculated by subtracting 276 d from the recorded birth date of each individual cow. Records for cows conceived within the months of June, July, and August were retained as heat stress-conceived (HSC) cows (n = 94,440); cows conceived within the months of December, January, and February were retained as thermoneutral-conceived (TNC) contemporaries (n = 141,365). In order to account for the effects of environmental conditions on total milk production for a given lactation, cows were blocked by season of calving (winter, spring, summer or fall). Adjusted 305-day mature-equivalent milk production was evaluated with a mixed model ANOVA using SAS, in which random effects were used to account for variability between herds. Of the cows that calved in the summer, fall and winter, TNC cows had higher milk yield than the HSC cows in all states. Interestingly, the cows that calved in the spring presented a unique relationship, with HSC cows producing more milk. Overall however, heat stress at the time of conception is associated with lower milk production during the first lactation. While this association does not prove cause and effect, it does provide justification for additional investigation into whether heat stress around the time of conception results in long-term, detrimental consequences for the conceptus.     

Sequence comparison of mitochondrial tRNA genes and origin of light strand replication in Bos taurus and Nellore (Bos indicus) breeds

Although the complete bovine mitochondrial DNA molecule has been previously sequencedand sequence comparisons of the mitochondrial displacement loop have been performed, detailed sequence information is limited on coding regions of mitochondrial DNA within and among breeds of Bos taurus and Bos indicus. This study analysed polymorphism of the mitochondrial DNA transfer RNA genes for trypto-phan, alanine, asparagine, cysteine, tyrosine and the origin of light strand replication among Ayrshire, Canadian, Belgium Blue, Brown Swiss, Hereford, Jersey, Limousine, Piedmon-taise, Red Angus, Simmental (Bos taurus) and a Nellore (Bos indicus). Nucleotide sequence analysis of a 420-bp fragment of mitochondrial DNA comprising the five transfer RNA genes showed 100% homology among single individuals of the Bos taurus breeds. The Nellore breed showed guanine to adenine substitutions in the DHU arm of asparagine tRNA and in the origin of light-strand replication. This equates to a 0.5% sequence difference between the Nellore andBos taurus breeds and may reflect an independent evolutionary origin of the species.     

Novel SNPs of the Bovine PRLR Gene Associated with Milk Production Traits

The single nucleotide polymorphisms (SNPs) within exon 10 of the prolactin receptor gene (PRLR) were detected in Chinese Holstein cows using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing methods, and their genetic effects on milk production traits were evaluated in this study. Two newly detected SNPs (g.9206G→A and g.9681C→T) caused amino acid variations E378K and A536V, respectively, which were then preliminarily predicted at the topological level. Statistical results indicated that the two SNPs were significantly associated with milk yields, and cows with the combined genotype GGCC showed superior milk performance. A putative phosphorylation site was identified at residue 378K ([ST]-×-[RK]), which offers a partial explanation for the associations. These results suggest that the two novel SNPs within exon 10 of the PRLR gene associated with milk production traits are useful genetic markers in a selection program for Holstein dairy cattle.     

Differences in the rumen methanogen populations of lactating Jersey and Holstein dairy cows under the same diet regimen

In the dairy cattle industry, Holstein and Jersey are the breeds most commonly used for production. They differ in performance by various traits, such as body size, milk production, and milk composition. With increased concerns about the impact of agriculture on climate change, potential differences in other traits, such as methane emission, also need to be characterized further. Since methane is produced in the rumen by methanogenic archaea, we investigated whether the population structure of methanogen communities would differ between Holsteins and Jerseys. Breed-specific rumen methanogen 16S rRNA gene clone libraries were constructed from pooled PCR products obtained from lactating Holstein and Jersey cows, generating 180 and 185 clones, respectively. The combined 365 sequences were assigned to 55 species-level operational taxonomic units (OTUs). Twenty OTUs, representing 85% of the combined library sequences, were common to both breeds, while 23 OTUs (36 sequences) were found only in the Holstein library and 12 OTUs (18 sequences) were found only in the Jersey library, highlighting increased diversity in the Holstein library. Other differences included the observation that sequences with species-like sequence identity to Methanobrevibacter millerae were represented more highly in the Jersey breed, while Methanosphaera-related sequences and novel uncultured methanogen clones were more frequent in the Holstein library. In contrast, OTU sequences with species-level sequence identity to Methanobrevibacter ruminantium were represented similarly in both libraries. Since the sampled animals were from a single herd consisting of two breeds which were fed the same diet and maintained under the same environmental conditions, the differences we observed may be due to differences in host breed genetics.