Leptin in farm animals: where are we and where can we go?

Abstract

Fat affects meat quality, value and production efficiency as well as providing energy reserves for pregnancy and lactation in farm livestock. Leptin, the adipocyte product of the obese (ob) gene, was quickly seen as a predictor of body fat content in animals approaching slaughter and an aid to assessing reproductive readiness in females. Its participation in inflammation and immune responses that help animals survive infection and trauma has clear additional relevance to meat and milk production. Furthermore, almost a decade of discoveries of nucleotide polymorphisms in the leptin and leptin receptor genes has suggested useful applications relating to feed intake regulation, the efficiency of feed use, the composition of growth, the timing of puberty, mammogenesis and mammary gland function and fertility in cattle, pigs and poultry. The current review attempts to summarise where research has taken us in each of these aspects and speculates on where future research might lead.Keywords: leptin, farm animals, production efficiency, fat, body composition ImplicationsLeptin has not yet delivered the initial expectations of animal scientists eager for a robust and reliable marker of body and carcase fat in farm livestock, but its close association with fat and fat deposition continue to cast it as a potential aid for enhancing production efficiency, reproductive success and immune function. Polymorphisms in the leptin and leptin receptor genes provide powerful additional tools for enhanced selection to meet aspirations for increased global animal production within an overarching need to contain and reduce environmental impacts. IntroductionFat is important in all livestock production as it affects product quality and production efficiency and provides the energy reserves for pregnancy and lactation. The discovery of the obese (ob) gene and its product leptin (Zhang et al., 1994;Halaas et al., 1995) and their links to body fat (Frederich et al., 1995;Maffei et al., 1995) excited animal scientists, who quickly saw potential for leptin as a predictor of body composition in animals approaching slaughter and of reproductive readiness in females (Hossner, 1998). Its involvement in inflammation and in the immune responses that help animals survive infection and trauma, also has clear relevance and attention turned to using leptin, directly or indirectly, to influence production characteristics with feed intake, body composition, puberty, mammary gland function, immune response and the reproductive pathway all possible targets. Associations of production traits with polymorphisms in the leptin and leptin receptor genes pointed to additional applications.Among the many reviews of leptin, those by ), Baile et al. (2000, Ingvartsen and Boisclair (2001), Chilliard et al. (2005) and Barb et al. (2006) stand out as most relevant to livestock with Williams et al. (2002), Barb and Kraeling (2004), Barb et al. (2005) and Zieba et al. (2005) emphasising its involvement in reproduction. Those by Ahima and Flier (2000) and Harris (200...

Single-Nucleotide Polymorphisms in the LEPR Gene Are Associated with Divergent Phenotypes for Age at Onset of Puberty in Davisdale Ewes1

“…Leptin concentration increases during pubertal development in heifers [30] and in sheep [8], and leptin has been proposed to signal that the critical thresholds for body fat mass have been reached and thus are considered permissive for onset of puberty [10,31].…”

“…Control of age at onset of puberty is known to be influenced by genetics, with moderate heritability [6,7]. Factors such as body weight, growth, and body fat are important regulators of age at onset of puberty [8][9][10][11]. Because sheep are seasonal breeders, measuring age at onset of puberty can be complex, and we have recently observed that the proportion of ewe lambs that failed to attain puberty before 1 yr of age (i.e., during their first breeding season) varied from 9% to 35%, while the average age of those ewes that did attain puberty remained relatively constant (approximately 8 mo).…”

Effect of chronic infusion of leptin and nutrition on sexual maturation of zebu heifers1

“…It has been postulated that leptin acts as a permissive signal to the occurrence of puberty (Wylie, 2010). Therefore, insuffi cient nutrient availability or depleted body reserves followed by depressed plasma leptin would attenuate the ability of other signals to trigger puberty or even act as an absolute gating mechanism for puberty (Cunningham et al, 1999).…”

Research Article Study of genetic variability in pigs after the traditional breeding program.

“…Among the molecular markers associated with characteristics of economic interest are the genes, among which we can mention: DGAT1 (diacylglycerol acyltransferase 1), a gene that encodes the enzyme of the same name acting in the metabolism of intestinal fat absorption, lipoprotein synthesis, adipose tissue formation, and lactation (Nonneman and Rohrer, 2002;Cui et al, 2011); LEP (leptin) and LEPR (leptin receptor) are important regulators of appetite, metabolism, reproduction (Wylie, 2011;Georgescu et al, 2014), and the deposition of intramuscular fat ); H-FABP (heart-type fatty acid binding protein) is related to the regulation of fatty acid uptake and intracellular transport (Gerbens et al, 1999;Chao et al, 2012); MC4R (melanocortin 4 receptor gene) is an important genetic marker for characteristics related to backfat thickness, feed intake, and growth rate (Jokubka et al, 2006;Óvilo et al, 2006); SREBF1 (sterol regulatory element binding transcription factor) involved in the differentiation of adipocytes, as well as cholesterol and fatty acids (Stachowiak et al, 2013); and GH (growth hormone) that influences economically important characteristics such as carcass weight and fat thickness (Franco et al, 2003;Bižienė et al, 2011).…”