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Theriogenology 66 (2006) 8.
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ABSTRACT: 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.
Domestic Animal Endocrinology 29 (2005) 1.
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ABSTRACT: 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.
Vitamins and Hormones-Advances in Research and Applications 71 (2005).
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ABSTRACT: Modern pig farming is still confronted with high perinatal piglet losses which are mainly contributed to factors associated with the progress of piglet expulsion. Therefore the aim of this study was to identify sow- and piglet factors affecting the duration of the expulsive stage of farrowing and piglet birth intervals in spontaneous farrowing sows originating from five different breeds. In total 211 litters were investigated. Breed affected duration of the expulsive stage significantly: the shortest duration was found in Large White x Meishan F2 crossbred litters and the longest duration in Dutch Landrace litters. No effect of parity on the duration of the expulsive stage was found. An increase in littersize (P < 0.01), an increase in number of stillborn piglets per litter (P < 0.05) and a decrease of gestation length (P < 0.05, independently of littersize) all resulted in an increased duration of the expulsive stage of farrowing. A curvilinear relationship between birth interval and rank (relative position in the birth order) of the piglets was found. Besides that, piglet birth intervals increased with an increasing birth weight (P < 0.001). Stillborn (P < 0.01) and posteriorly presented (P < 0.05) piglets were delivered after significantly longer birth intervals than liveborn and anteriorly presented piglets. The results on sow- and piglet factors affecting duration of the expulsive stage and piglet birth intervals obtained in this study contribute to an increased insight into (patho) physiological aspects of perinatal mortality in pigs
Theriogenology 64 (2005) 7.
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ABSTRACT: Large White×Meishan F2 crossbred gilts (n=57) were observed continuously during farrowing while the placentae of their offspring were labeled in order to examine the duration of farrowing and placenta expulsion in relation to maternal-, piglet- and placental traits and the duration of birth interval in relation to birth weight, birth order and placental traits. Independently from each other, litter size, gestation length and offspring directed aggression significantly (P0.05) affected duration of farrowing. An increase in litter size was associated with an increase of duration of farrowing and an increase in gestation length was associated with a decrease of duration of farrowing. Aggressive gilts took longer to farrow, compared to non-aggressive ones. After taking into account litter size, gestation length and offspring directed aggression, placental thickness (i.e., placental weight corrected for placental surface area) was significantly (P<0.05) related to duration of farrowing, i.e., litters with on average thicker placentae took longer to farrow. The latter effect is the result of the fact that individual placental thickness significantly (P<0.01) affected individual birth interval, independent of birth weight. The piglet has to break its own membranes to be able to start its journey through the uterus towards the birth channel. Apparently, a thicker placenta offers more resistance and thus prolongs the process of birth. Independent of placental thickness, birth interval significantly (P<0.01) decreased with an increase in birth order (first born to last born). The high variation of birth intervals for the last born piglets, caused a slight increase in average birth interval for the latter piglets. Litters with on average more areolae per placenta took significantly (P<0.001) less time to be born than litters with on average less areolae per placenta (independent of total number of piglets born and other placental traits), while birth intervals within litters were not affected by this trait. Thus, these results are probably due to a gilt trait rather than a piglet trait. Since the number of areolae represent the number of uterine glands present, the gilt trait might be uterine development. Duration of placenta expulsion significantly (P<0.01) increased with an increase of duration of farrowing. Furthermore, the first placenta was expelled significantly (P<0.01) earlier relative to last piglet when duration of farrowing was protracted, while there was no relation of the time interval between first placenta and last piglet and the duration of placenta expulsion. In conclusion, the most important finding of this study is that placental thickness rather than birth weight appears to play an important role in the duration of birth intervals and as a result, of duration of parturition in gilts
Theriogenology 62 (2004) 1-2.
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ABSTRACT: Leptin concentrations in body fluids and tissues undergo dynamic changes during the periparturient period. Polymorphisms in the leptin gene have been shown to be associated with differences in leptin concentration during late pregnancy but not during lactation. As the promoter of leptin regulates the expression of leptin, polymorphisms in this region could play an important role in the differences in leptin expression observed during the periparturient period. We sequenced the leptin promoter and discovered 20 SNP in a 1.6-kbp region of the bovine leptin promoter. Fourteen of these SNP were genotyped for all animals and these were found to be associated with leptin concentrations during late pregnancy but not during lactation. Three of these SNP are located in a 135-bp promoter region and together explained 14.3% of the variance in prepartum leptin concentrations which indicates that this region might be important for pregnancy-induced leptin synthesis. In the association study of the 14 SNP with dairy traits three were separately found to be associated with fertility, energy balance and protein yield. These might serve as markers for future breeding programmes for better fertility and energy balance without significantly influencing milk yield in dairy cattle
Animal Genetics 36 (2005) 2.
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Journal of Animal Science 83 (2005) 1.
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Journal of Animal Science 82 (2004).
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Dier en arts 19 (2004) 6/7.
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Animal Genetics 34 (2003) 2.
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Journal of Animal Science 81 (2003).
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ABSTRACT: Behavioral estrus and components of litter size at Day 35/36 of pregnancy were studied in gilts with prolactin receptor (PRLR) genotype AA (n=9), AB (n=25), and BB (n=22). This PRLR polymorphism (two alleles, A and B) has been associated with litter size, although it is not known whether the polymorphism itself causes differences in litter size or whether it is a marker for a closely linked causative gene. Estrus length in three successive estrous cycles was not affected by genotype, but estrous cycle length tended (P<0.1) to be longer for AA gilts compared to AB and BB gilts. AA gilts had a significantly (P<0.05) higher ovulation rate (21.5±0.9) than BB gilts (18.7±0.6), resulting in a numerically higher number of embryos at Day 35/36 (17.0±1.3, 15.6±0.8, and 13.7±0.9 for AA, AB, and BB gilts, respectively) which may lead to a subsequent difference in litter size. Ovulation rate of AB gilts (20.0±0.5) was intermediate. Genotype affected the total weight of the ovaries (P<0.05). Even after subtraction of the total weight of corpora lutea, ovarian weight in AA gilts was highest (16.6±1.0 g), in BB lowest (13.4±0.6 g), and in AB gilts intermediate (15.0±0.6 g; P<0.05). Unlike AB gilts, in AA and BB gilts uterine length was adapted to litter size, which led to longer (P<0.05) uteri for AA gilts (669±28 cm) compared to BB gilts (566±18 cm). Furthermore, embryos of AA gilts had heavier placentae (52.5±3.4 g) and larger implantation surface areas (309±19 cm2) than embryos of BB (42.0±2.3 g, P<0.05; 256±12 cm2, P<0.1) or AB (43.2±2.0 g, P<0.1; 257±11 cm2, P<0.05) gilts. Results of this experiment show that the PRLR gene or a very closely linked gene affects porcine ovaries, uterus, and placenta in a way that might lead to differences in litter size. Since other genes and also environmental factors, however, might change the effect within the 112 days to parturition, it is preferable to state that the PRLR gene is a candidate gene for ovulation rate rather than for litter size.
Theriogenology 59 (2003) 3-4.
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Journal of Animal Science 80 (2002).
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Livestock Production Science 78 (2002).
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ABSTRACT: 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.
Journal of dairy science 85 (2002).
