Rapid communication: mapping of leptin to bovine chromosome 4 by linkage analysis of a PCR-based polymorphism

Variation in bovine leptin gene affects milk fatty acid composition in New Zealand Holstein Friesian × Jersey dairy cows

Leptin is a protein hormone secreted from white adipose tissue. It regulates food/feed intake, body weight, immune function and reproduction. In our investigation, the polymerase chain reaction (PCR) amplification coupled with single-strand conformational polymorphism (SSCP) analysis was used to reveal variation in bovine leptin gene (LEP) in New Zealand (NZ) Holstein Friesian × Jersey (HF × J) dairy cows. Subsequent sequence analysis of a 430 bp amplicon spanning the entirety of exon 3 and part of the intron 2 region revealed three variant sequences (A3, B3 and C3) containing a total of five nucleotide substitutions, all of which have been reported previously. Using general linear mixed-effect model analyses, the presence of variant A3 (the most common variant) was associated with a decreased level of C15:1, C18:1 trans-11, C18:1 all trans, C18:2 trans-9, cis-12, C22:0 and C24:0 levels but increased levels of C12:1 and C13:0 iso (p<0.05). Variant B3 was associated with reduced levels of C6:0, C8:0, C11:0, C13:0 and C20:0 but increased C17:0 iso and C24:0 levels (p<0.05). Variant C3 was associated with decreased C17:0 iso levels but increased C20:0 (p<0.05) levels. In a genotype model, the A3B3 genotype was associated with increased levels of C22:0 and C24:0 but decreased C8:0, C10:0, C11:0, C13:0, C15:0 and grouped medium-chain fatty acid (MCFA) levels (p<0.05). Genotype A3C3 was found to be associated with decreased levels of C10:0, C11:0, C13:0 and grouped MCFA (p<0.05). This is the first report of findings of this kind in NZ HF × J cows, and they suggest that variation in exon 3 of bovine leptin gene could be explored as a means of decreasing the concentration of saturated fatty acids in milk.

Evaluation of candidate genotype of leptin gene associated with fertility and production traits in Hardhenu (Bos taurus × Bos indicus) cattle

The present study was conducted on Hardhenu cattle to screen genomic region of leptin gene with an objective to find the association of genotypes with fertility and production traits. The association analysis with traits under study was analysed by least squares analysis of variance by taking SNPs genotype as fixed effects in the statistical model. The genotypic frequencies with respect to targeted loci g.92450765 G > A indicated that AG (0.54) genotype was highest in Hardhenu cattle. Chi-squared tests showed that g.92450765G > A SNP meet with the Hardy-Weinberg equilibrium (p > .05).The association analysis revealed significant association of genotypes with total milk yield (TMY) and 305 days milk yield (MY) (p < .05). Service period (SP) and calving interval (CI) were also found significantly associated with genotypes (p < .05). Whereas, lactation length (LL), dry days (DD) and age at first calving (AFC) did not divulge any significant association with genotype. The AG and GG genotypes were associated with higher milk yields as compared to AA genotype, indicating that allele G was associated with superior milk performance. However, AA genotyped cattle found to be favourable with SP, CI and artificial insemination (AI) per conception compared to AG and GG genotyped cows. Chi-square analysis revealed that genetic variants of g.92450765 G > A SNP of leptin gene differ significantly with regard to reproductive disorders incidence (p < .05). The frequency of GG genotype (88.89%) in the affected animal group was very high followed by AG. The animals with GG genotype were found to be more susceptible to reproductive disorders as suggested by the higher odd ratio value (16.00) in logistic model. These observations and their differential association with the fertility and production traits can be utilized as an aid to selection for genetic improvement of antagonistic traits in dairy cows.

Identification of novel nucleotide sequence variations in an extended region of the bovine leptin gene (LEP) across a variety of cattle breeds from New Zealand and Nigeria

Leptin is mainly secreted by white adipose tissue in animals. Leptin acts by stimulating or inhibiting the release of a neurotransmitter, which eventually results in a decrease in food/feed intake and an increase in energy expenditure. In this investigation, the polymerase chain reaction (PCR) coupled with single-strand conformation polymorphism (SSCP) analysis was used to reveal nucleotide sequence variations in bovine leptin gene (LEP) in 338 cattle of a variety of breeds farmed in New Zealand (NZ) and Nigeria. These included NZ Hereford, Angus, Shorthorn, and crossbred Holstein-Friesian  ×  Jersey cattle and the Nigerian Sokoto Gudali, Red Bororo, White Fulani, and crossbred Holstein-Friesian  ×  White Fulani cattle. Sequence analysis of three regions of bovine LEP that encompassed selected coding and non-coding regions, revealed a total of 12 nucleotide sequence variations (six in exons and six in introns). Of these, three are reported here for the first time, whereas nine have been previously described. Some of the variations identified were common in both the NZ and Nigerian cattle breeds, while others were peculiar to particular breeds from a specific region. The sharing of common variants across different breeds irrespective of geography may indicate an evolutionary relationship, just as the differences within a breed might be attributable to either selective pressure for specific traits or random genetic drift. The detection of both new and previously documented variations in bovine LEP suggests that the gene is highly variable.

Characteristics of dairy productivity of Holstein heifers depending on their genetic potential

The study presents the results obtained in DNA testing of allelic polymorphism by PCR-RFLP based methods for the leptin and stearoyl-coenzyme A desaturase genes and the interaction of their complex genotypes on the milk productivity indicators of Holstein heifers of Tatarstan population. The study was carried out among 471 Holstein cow-heifers by Integrated Agricultural Production Centre “Stud farm named after Lenin” of Atninsky district of the Republic of Tatarstan in 2016–2018. All complex LEP/SCD1 genotypes were identified through the study. The maximum frequency was observed in the combination of heterozygous genotypes LEPTCSCD1TC 149 animals (31.5 %). Milk productivity test, based on the complex genotypes LEP and SCD1, showed that a significantly high level of productivity for 305 days of lactation was 7314.4 kg, and in heifers with a complex genotype LEPTTSCD1CC was minimal (6337.4 kg) in comparison with indicators of milk yield of heifers with other complex genotypes. According to the content of the mass fraction of fat, reliably the best indicators were established in a subpopulation of animals with a complex TT/TC genotype 3.87 %. The content of the mass fraction of protein was maximal for animals with a complex CC/CC genotype.

Association of leptin gene polymorphism with economic traits in crossbred cattle

The present investigation was carried out to identify two polymorphisms in leptin gene by PCR-RFLP and to examine the possible association of the identified genotypes with growth, production and reproduction traits in 205 female crossbred cattle (½ Holstein Friesian × ½ Hariana). One fragment of 330 bp comprising partial intron 2 and exon 3, and another fragment of 94 bp comprising partial exon 2 of leptin gene were amplified, and digested with HphI and Kpn2I restriction enzymes, respectively, for identification of genotypes. The animals with HphI-RFLPCT and Kpn2I-RFLP-AV genotypes had significantly higher birth weight than the HphI-RFLP-CC and Kpn2IRFLP- AA genotypes respectively. The HphI-RFLP locus had significant effect on body weight at 12 months of age, age at first calving and average daily milk yield, while, Kpn2I-RFLP had significant effect on first lactation milk yield and average daily milk yield. Therefore, leptin gene could be used as a marker for genetic selection of economic traits in cattle.

Association of the leptin gene with carcass characteristics in Nellore cattle

Advances in DNA technology have created biotechnological tools that can be used in animal selection and new strategies for increasing herd productivity and quality. The objective of the present work was to associate the genotypes of leptin gene exon 2 polymorphisms with productive traits in Nellore cattle. Blood was collected from Nellore males and PCR-RFLP reactions were performed with the restriction enzymes Cla I and Kpn 2I. The gene frequencies resulting from digestion by Cla I were 0.60 and 0.40 for allele A and T, respectively; the genotypic frequencies were AA = 0.20 and AT = 0.80. The gene frequencies from digestion by Kpn 2I were 0.81 for allele C and 0.194 for allele T; the genotypic frequencies were CC = 0.62 and CT = 0.38. The populations in both cases were not in Hardy-Weinberg equilibrium (p > 0.05), and the TT genotype was not found. Significant associations were noted between leptin gene exon 2 polymorphisms and five productive traits in Nellore cattle: carcass fat distribution, the intensity of red muscle coloration, pH, marbling, and post-slaughter fat thickness.

Association of bovine leptin polymorphisms with energy output and energy storage traits in progeny tested Holstein-Friesian dairy cattle sires

Background

Leptin modulates appetite, energy expenditure and the reproductive axis by signalling via its receptor the status of body energy stores to the brain. The present study aimed to quantify the associations between 10 novel and known single nucleotide polymorphisms in genes coding for leptin and leptin receptor with performance traits in 848 Holstein-Friesian sires, estimated from performance of up to 43,117 daughter-parity records per sire.

Results

All single nucleotide polymorphisms were segregating in this sample population and none deviated (P > 0.05) from Hardy-Weinberg equilibrium. Complete linkage disequilibrium existed between the novel polymorphism LEP-1609, and the previously identified polymorphisms LEP-1457 and LEP-580. LEP-2470 associated (P < 0.05) with milk protein concentration and calf perinatal mortality. It had a tendency to associate with milk yield (P < 0.1). The G allele of LEP-1238 was associated (P < 0.05) with reduced milk fat concentration, reduced milk protein concentration, longer gestation length and tended to associate (P < 0.1) with an increase in calving difficulty, calf perinatal mortality and somatic cells in the milk. LEP-963 exhibited an association (P < 0.05) with milk fat concentration, milk protein concentration, calving difficulty and gestation length. It also tended to associate with milk yield (P < 0.1). The R25C SNP associated (P < 0.05) with milk fat concentration, milk protein concentration, calving difficulty and length of gestation. The T allele of the Y7F SNP significantly associated with reduced angularity (P < 0.01) and reduced milk protein yield (P < 0.05). There was also a tendency (P < 0.1) for Y7F to associate with increased body condition score, reduced milk yield and shorter gestation (P < 0.1). A80V associated with reduced survival in the herd (P < 0.05).

Conclusions

Several leptin polymorphisms (LEP-2470, LEP-1238, LEP-963, Y7F and R25C) associated with the energetically expensive process of lactogenesis. Only SNP Y7F associated with energy storage. Associations were also observed between leptin polymorphisms and calving difficulty, gestation length and calf perinatal mortality. The lack of an association between the leptin variants investigated with calving interval in this large data set would question the potential importance of these leptin variants, or indeed leptin, in selection for improved fertility in the Holstein-Friesian dairy cow.

Leptin gene polymorphism in Iranian native Golpayegani and Taleshi cows

The objective of the present investigation was to study genetic variations in the exon II of leptin gene in Iranian Golpayegani and Taleshi cows. Blood samples were collected from 76 Golpayegani and 64 Taleshi cows randomly selected from Delijan city (Esfahan province) and Talesh city (Guilan province) in Iran, respectively. Genomic DNA was extracted from 100 micro litters of blood using guanidium thiocyanate-silica gel method. A 94 bp fragment from exon II of the bovine leptin gene was amplified using the polymerase chain reaction. Digestion of PCR products with Bsp13I restriction enzyme differentiated C and T alleles. The T allele frequencies were 0.29 and 0.45 in Golpayegani and Taleshi breeds, respectively. The frequencies of the genotypes CC, CT and TT were 0.42, 0.58 and 0 in Golpayegani and 0.36, 0.36 and 0.27 in Taleshi cows. The average heterozygosities were 0.41 and 0.50 in Golpayegani and Taleshi breeds, respectively. The chi2 test did not confirm the Hardy-Weinberg equilibrium in both populations.

Bovine gene polymorphisms related to fat deposition and meat tenderness

Leptin, thyroglobulin and diacylglycerol O-acyltransferase play important roles in fat metabolism. Fat deposition has an influence on meat quality and consumers' choice. The aim of this study was to determine allele and genotype frequencies of polymorphisms of the bovine genes, which encode leptin (LEP), thyroglobulin (TG) and diacylglycerol O-acyltransferase (DGAT1). A further objective was to establish the effects of these polymorphisms on meat characteristics. We genotyped 147 animals belonging to the Nelore (Bos indicus), Canchim (5/8 Bos taurus + 3/8 Bos indicus), Rubia Gallega X Nelore (1/2 Bos taurus + 1/2 Bos indicus), Brangus Three-way cross (9/16 Bos taurus + 7/16 Bos indicus) and Braunvieh Three-way cross (3/4 Bos taurus + 1/4 Bos indicus) breeds. Backfat thickness, total lipids, marbling score, ribeye area and shear force were fitted, using the General Linear Model (GLM) procedure of the SAS software. The least square means of genotypes and genetic groups were compared using Tukey's test. Allele frequencies vary among the genetic groups, depending on Bos indicus versus Bos taurus influence. The LEP polymorphism segregates in pure Bos indicus Nelore animals, which is a new finding. The T allele of TG is fixed in Nelore, and DGAT1 segregates in all groups, but the frequency of allele A is lower in Nelore animals. The results showed no association between the genotypes and traits studied, but a genetic group effect on these traits was found. So, the genetic background remains relevant for fat deposition and meat tenderness, but the gene markers developed for Bos taurus may be insufficient for Bos indicus.

Polymorphisms in the bovine leptin promoter associated with serum leptin concentration, growth, feed intake, feeding behavior, and measures of carcass merit

Leptin is the hormone product of the obese gene synthesized and secreted predominantly by white adipocytes. It functions as a lipostatic signal regulating BW, food intake, energy expenditure, reproduction, and certain immune system functions. Although previous studies have identified polymorphisms in the coding regions of the leptin gene in cattle that show considerable associations with feed intake, milk quality and quantity, and carcass fatness, no such associations have been reported for the leptin promoter. The current study reports associations between SNP in the 5' untranslated promoter region of the bovine leptin gene with serum leptin concentration, growth, BW, feed intake, feeding behavior, and carcass merit in hybrid cattle (n = 150). The study showed that animals with the TT genotype of a less frequent cytosine/thymine (C/ T) substitution (UASMS2; frequency of thymine allele equals 0.21) detected at position 528 in the bovine leptin promoter (GenBank Accession No. AB070368) show 48 and 39% increases in serum leptin concentration (P < 0.001), 39 and 31% increases in backfat thickness (P < 0.001), and 13 and 9% increase in marbling score (P = 0.01), compared with CC or CT genotypes, respectively. Animals with the TT genotype also show significantly higher feed intake (P < 0.001), growth rate, metabolic BW (P < 0.05), and live weight at slaughter (P < 0.10). Animals with the GG genotype of a more frequent cytosine/guanine (C/G) substitution (UASMS3; frequency of G allele equals 0.59) at position 1759 in the bovine leptin promoter (GenBank Accession No. AB070368) also show higher feed intake (P = 0.001), growth rate (P < 0.10), and BW (P < 0.01). The thymine allele of UASMS2 and the guanine allele of UASMS3 were separately associated with higher feeding duration (P < 0.05). The two SNP show significant linkage disequilibrium and could also be relevant in predicting other characteristics, such as milk yield and quality in cattle. These results, however, represent the initial associations of the polymorphisms with these traits, and further efforts are required to validate these findings in other populations.

Effect of polymorphisms linked to LEP gene on its expression on adipose tissues in beef cattle

In cattle, genetic markers at the leptin (LEP) gene and at those linked to the gene have been described as affecting calving interval (markers LEPSau3AI and IDVGA51), or daily weight gain (BMS1074 and BM1500). This work investigated the effect of these alleles on LEP mRNA levels in cattle subcutaneous and omental adipose tissues. A sample of 137 females of a Brangus-Ibage beef cattle herd was analysed to evaluate the distribution of the polymorphisms; then, animals having at least one of the IDVGA51*181 (allele 181 at marker IDVGA51; six animals), LEPSau3AI*2 (four), BMS1074*151 (13), BM1500*135 (six) alleles and a control group composed of animals without any of these alleles (four animals) were submitted to surgery to obtain omental and subcutaneous adipose tissues. Leptin mRNA expression was quantified by TaqMan RT-PCR, using 18S rRNA as internal control and adjusted for the effect of body condition score, through regression analysis. Omental fat had LEP gene expression 33% lower than the subcutaneous tissue. Carriers of IDVGA*181 and BMS1074*151 showed subcutaneous fat leptin mRNA levels higher than the controls. Leptin controls feed intake and coordinates reproduction; therefore, animals with higher LEP gene expression will probably have lower daily weight gain than others with similar forage offer and nutritional condition and probably will also have longer calving interval.

Mutation in the Sp1 motif of the bovine leptin gene affects its expression

Leptin is expressed mainly by adipocytes and plays a crucial role in the regulation of energy expenditure, food intake, and adiposity. Using PCR-heteroduplex analysis and sequencing, we investigated a C/G substitution in the promoter region of the bovine leptin gene. Application of the electrophoretic mobility shift assay showed that the C-->G transversion decreased the leptin gene promoter binding capacity for nuclear proteins. With real-time PCR and Western blotting, we showed that the leptin expression level was higher in cattle with the CC than with the GG genotype.

Association of single nucleotide polymorphisms in the leptin gene with carcass and meat quality traits of beef cattle1

Studies with different populations are required to properly characterize the robustness of associations of polymorphisms in candidate genes with economically important traits across beef cattle populations before this sort of genetic information can be used efficiently in breeding and management decisions. The objective of this study was to evaluate the association of previously reported SNP in the bovine leptin gene with carcass and meat quality traits from a large sample of crossbred beef cattle. Five SNP (UASMS1, UASMS2, UASMS3, E2JW, and E2FB) were genotyped on 1,111 crossbred bulls, heifers, and steers. The measured traits included fat, lean, and bone yield (%) by partial rib dissection, grade fat, LM area, HCW, quality grade, LM i.m. fat, and tenderness evaluation of LM and semitendinosus muscle. Only four SNP were analyzed (UASMS1, UASMS2, E2JW, and E2FB), because UASMS1 and UASMS3 were completely linked. A uni-variate mixed-inheritance animal model was used to evaluate the association of either genotypes or haplo-types with the traits. The two leptin exon 2 SNP were associated with fat and lean yield and grade fat (E2JW, P < 0.01; E2FB, P < 0.05), and they interacted in their effect on LM tenderness (P < 0.01). The leptin promoter SNP were either not associated with any of the traits (UASMS2) or with fat yield only (UASMS1). Three haplotypes (TCAC, CCAT, TTAC) were at high frequency in the population (88%) and had similar effects on all the traits. Compared with the common haplotypes, one haplotype (CCTT) showed a significantly different effect on fat and lean yield and grade fat (P < 0.01), and one haplotype (TTTT) had a different effect on LM tenderness (P < 0.03). Therefore, important associations between SNP within the leptin gene with lean yield, fatness (fat yield and subcutaneous fat), and tenderness were detected. Results confirm some of the previously reported associations, but diverge with respect to others, showing that further efforts are required to validate some prospective associations.

Genetics and physiology of leptin in periparturient dairy cows

In dairy cattle, the increase in milk yield has been accompanied by a more negative energy balance (EB) during early lactation and a decrease in fertility. As the hormone leptin is involved in regulation of nutritional status and reproductive function this hormone is an interesting protein to investigate during the periparturient period in dairy cattle. This study was performed to get insight into the function of leptin during the periparturient period and to perform an association study between polymorphisms in the bovine leptin gene and leptin receptor gene and fertility as well as production traits. Leptin concentrations in the periparturient cow undergo remarkable changes; leptin concentrations were high during late pregnancy and declined to a nadir at parturition. Genetic analysis of the leptin gene indicated that a combination of three polymorphisms located at a 135 bp region of the leptin promoter explained most of the variance in prepartum leptin concentrations. The two extreme genotype combinations could be used to investigate the function of leptin concentrations in pregnant cows. A polymorphism located on intron 2 of the leptin gene explained a significant part of the variation in milk yield. On the promoter region of the leptin gene an SNP was detected that was associated with first postpartum luteal activity (FPLA). This SNP could be a candidate marker for fertility in dairy cows. Another SNP on the leptin promoter was associated with energy balance and dry matter intake (DMI) where a higher dry matter intake occurred together with a higher energy balance. Two genotype combinations of the aforementioned three associated SNPs were defined which had a good milk yield together with a good energy balance and fertility. Calculations of an economical value per trait have to validate if one of these genotype combinations would be a possible candidate to be used in selection.

Regulatory roles of leptin in reproduction and metabolism: a comparative review

Leptin plays an important role in signaling nutritional status to the central reproductive axis of mammals and appears to be at least a permissive factor in the initiation of puberty. The expression and secretion of leptin are correlated with body fat mass and are acutely affected by changes in feed intake. Moreover, circulating leptin increases during pubertal development in rodents, human females and heifers. Effects of leptin are mediated mainly via receptor activation of the JAK-STAT pathway; however, activation of alternative pathways, such as MAP kinase, has also been reported. Although the leptin receptor (LR) has not been found on GnRH neurons, leptin stimulates the release of GnRH from rat and porcine hypothalamic explants. Moreover, leptin increases the release of LH in rats and from adenohypophyseal explants and/or cells from full-fed rats and pigs. In contrast, stimulation of the hypothalamic-gonadotropic axis by leptin in cattle and sheep is observed predominantly in animals and tissues pre-exposed to profound negative energy balance. For example, leptin prevents fasting-mediated reductions in the frequency of LH pulses in peripubertal heifers, augments the magnitude of LH and GnRH pulses in fasted cows, and enhances basal secretion of LH in vivo and from adenohypophyseal explants of fasted cows. However, leptin is incapable of accelerating the frequency of LH pulses in prepubertal heifers, regardless of nutrient status, and has no effect on the secretion of GnRH and LH in full-fed cattle or hypothalamic/hypophyseal explants derived thereof. Similar to results obtained with LH, basal secretion of GH from anterior pituitary explants of fasted, but not normal-fed cows, was potentiated acutely by low, but not high, doses of leptin. Mechanisms through which undernutrition hypersensitize the hypothalamic-gonadotropic axis to leptin may involve up-regulation of the LR. However, an increase in LR mRNA expression is not a requisite feature of heightened adenohypophyseal responses in fasted cattle. To date, leptin has not been successful for inducing puberty in ruminants. Future therapeutic uses for recombinant leptin that exploit states of nutritional hypersensitization, and identification of genetic markers for genotypic variation in leptin resistance, are currently under investigation.

Short communication: effect of leptin gene polymorphisms on breeding value for milk production traits

New molecular techniques focused on genome analysis open new possibilities for complex evaluation of economically important traits in farm animals. Milk production traits are typical quantitative characteristics controlled by a number of genes. Mutations in their sequences may alter animal performance as well as their breeding values. In this study, we investigated the effect of 3 restriction fragment length polymorphisms (RFLP): HphI, Kpn2I, and Sau3AI in the leptin gene, on bull breeding values for milk, fat, and protein yield, and fat and protein content. One hundred seventeen Polish Black and White AI bulls were genotyped. Pedigree analysis indicated a relatively close relationship between the bulls. Statistical analysis indicated that the HphI polymorphism has a significant effect on milk and protein yield. Animals with the TT genotype had approximately 2x higher estimated breeding values for milk and protein yields. No effect was found for the other 2 polymorphisms.

Leptin Gene Polymorphisms and Their Phenotypic Associations

In an era of rapidly increasing prevalence of human obesity and associated health problems, leptin gene polymorphisms have drawn much attention in biomedical research. Leptin gene polymorphisms have furthermore drawn much attention from animal scientists for their possible roles in economically important production and reproduction traits. Of the polymorphisms reported for exonic, intronic, and promoter regions of the leptin gene, 16 have been included in association studies in humans, 19 in cattle, and 6 (all exonic or intronic) in pigs. In humans, associations have been found with overweight or (early-onset) obesity, non-insulin-dependent diabetes mellitus, prostate cancer, and non-Hodgkin's lymphoma. In cattle, associations have been found with feed intake, milk yield traits, carcass traits, and reproduction-related traits, and in pigs with feed intake, average daily gain, carcass traits (backfat/leanness), and reproduction performance traits. Many of the polymorphisms were only included in a limited number of association studies, or the phenotypes studied varied largely for a given polymorphism between studies. Therefore, many of the associations found for these polymorphisms need to be confirmed in future studies before firm conclusions can be drawn.

Association of leptin gene polymorphisms with serum leptin concentration in dairy cows

Leptin is a hormone produced by adipocytes, and its expression is regulated by body fatness and energy balance. This study describes the association of four leptin gene polymorphisms in dairy cows (R4C, A59V, RFLP1, and BM1500) with circulating leptin concentrations during the periparturient period. A59V is located at a between-species conserved region of leptin, and R4C might have effect on the tertiary structure of the leptin protein because of the presence of an extra cystein. RFLP1 is an intronic SNP and BM1500 is a microsatellite located 3.6 kb downstream of the leptin locus. The four polymorphisms were genotyped in 323 HF heifers with known pedigree. Leptin concentrations were determined biweekly from 30 days before until 80 days after parturition. The effect of genotype on leptin concentrations was modeled by fitting a spline in ASREML describing leptin concentrations as a function of days relative to parturition for each genotype/allele. Surprisingly, associations were found during pregnancy, but not during lactation. This indicates that the polymorphism could be more effective during pregnancy. If further studies demonstrate that more leptin-binding protein (Ob-Re) is present in this stage, it is hypothesized that a structural difference in the leptin protein could cause a sub-optimal binding stringency to Ob-Re. Free leptin could be cleared faster than bound leptin, and this could result in lower leptin concentrations during pregnancy for the polymorphism. The effects found might be ascribed to R4C. However, more study on the Ob-Re receptor, like binding stringencies between R4C and wild-type leptin and glycosylation during pregnancy, would provide more insight in the results found.

A new mutation in the coding region of the bovine leptin gene associated with feed intake

An experimental cattle population was screened for polymorphisms in the leptin gene and five SNPs were found in the regions containing the coding sequences. The association of these polymorphisms with feed intake and fat-related traits was evaluated. The results suggest an association between a polymorphism in exon 2, described here for the first time, and feed intake. Individuals with genotype A/T at this position had 19% greater mean feed intake than individuals with genotype A/A. There was also evidence for a link between leptin haplotypes and some fat-related traits.

Genetic polymorphisms in porcine leptin gene and their association with reproduction and production traits

Leptin (LEP), the product of the leptin gene, is a 16-kDa protein synthesised by adipose tissue and is involved in regulation of feed intake, energy balance, fertility, and immune functions. Using bi-directional polymerase chain reaction amplification of specific alleles (bi-PASA) and PCR-restriction fragment length polymorphisms (PCR-RFLP), we have successfully detected genetic polymorphisms of LEP intron 1 and exon 3, respectively, in Landrace, Yorkshire, and Duroc. Chi-square statistics were used to calculate homogeneity of genotypic frequencies of 2 candidate genes for 3 breeds of animals. Effects of exon 3 polymorphisms on reproduction traits such as litter sizes of sows in the first parity and 1–4 parities were evident (P < 0.05) in Landrace, and 1–4 parities in Yorkshire. Polymorphisms of intron 1 affected (P < 0.05) only litter sizes of the first parity in Duroc. Effects of exon 3 polymorphisms on production traits such as average daily gain and feed efficiency were evident (P < 0.05) in Landrace and Yorkshire, respectively. Polymorphisms of intron 1 affected (P < 0.05) only backfat thickness in Duroc. Our data also show that the higher the reproduction traits, the lower the genotypic frequencies. Further, the better the production traits, the higher the genotypic frequencies were. These data suggest that the long-term selection of favourable traits in pig production may be partially attributed to the effects of LEP polymorphisms on reproduction and production traits.

Associations between leptin gene polymorphisms and production, live weight, energy balance, feed intake, and fertility in Holstein heifers

Leptin is a 16-kDa protein synthesized by adipose tissue and is involved in regulation of feed intake, energy balance, fertility, and immune functions. Since evidence of a genetic correlation between start of luteal activity and energy balance, milk yield, and live weights is present, we investigated the association of genetic differences in the bovine leptin gene with these traits. Between 1990 and 1997, a total of 613 Holstein-Friesian heifers of two genetic groups with known pedigree were followed from parturition until d 105 of lactation. During the first 15 wk of lactation live weight, feed intake, and milk yield were measured for 565 cows. The start of luteal activity was set at the first day with a progesterone concentration higher than 3 ng/ml. In addition to the interval between calving and start of luteal activity, analyses were performed for average milk yield, percentage fat, protein, and lactose in milk, dry matter intake, feed intake, energy balance, and live weight over the first 15 wk of lactation. All 613 cows were genotyped for two restricted fragment length polymorphisms and for the BM1500 microsatellite, all located at the leptin gene locus. Significances of the genotype effects were estimated using the approximated F-statistic provided by ASREML. Fixed effects were year-season, genetic group, and a quadratic polynomial for age at calving. Animal was fitted as a random effect including the additive relationship between animals to account for background genes. Firstly, each genotype effect was fitted in turn, and secondly the other restriction fragment length polymorphisms were fitted as a cofactor to take into account effects of linkage disequilibrium. Thirdly, sire x genotype interaction was investigated. Heifers with the RFLP1-AB genotype produce 1.32 kg/d more milk and consume 0.73 kg/d more food compared with the RFLP1-AA genotype. No effects were found for start of luteal activity. When linkage disequilibrium with the other markers was taken into account and DMI was included as fixed effect in the model a 0.96 kg/d higher milk yield was still found. Assuming that no pleiotropic effects on traits such as immunity and milk production in later lactations exist, future breeding programs favoring the RFLP1 B-allele can yield a higher milk production without negatively affecting energy balance and fertility. The prospects are good because in this study the frequency of the RFLP1 AB- and BB-genotypes were only 18.5 and 0.2%, respectively.