Role of leptin in farm animals: a review

The discovery of hormone leptin has led to better understanding of the energy balance control. In addition to its effects on food intake and energy expenditure, leptin has now been implicated as a mediator of diverse physiological functions. Recently, leptin has been cloned in several domestic species. The sequence similarity suggests a common function or mechanism of this peptide hormone across species. Leptin receptors are expressed in most of tissues, which is consistent with the multiplicity of leptin functions. The main goal of this review was to summarize knowledge about effect of leptin on physiology of farm animals. Experiments point to a stimulatory action of leptin on growth hormone (GH) secretion, normal growth and development of the brain. Surprisingly, leptin is synthesized at a high rate in placenta and may function as a growth factor for fetus, signalling the nutritional status from the mother to her offspring. Maturation of reproductive system can be stimulated by leptin administration. Morphological and hormonal changes, consistent with a major role of leptin in the reproductive system, have also been described, including the stimulation of the release of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin. Leptin has a substantial effect on food intake and feeding behaviour in animals. Administration of leptin reduces food intake. Its level decrease within hours after initiation of fasting. Leptin also serves as a mediator of the adaptation to fasting, and this role may be the primary function for which was the molecule evolved.     

Concentrating, purifying and detecting waterborne parasites

There has been recent emphasis on developing better methods for detecting diseases of zoonotic and veterinary importance. This has been prompted by an increase in human disease agents detectable in environmental samples, the potential for bioterrorism, and the lowering of international trade barriers and expansion of personal travel, which are bringing previously considered exotic diseases to new geographical localities. To appreciate the complexities of developing detection methods and working with environmental samples, it is appropriate to review technologies currently in use, as well as those in development and presently limited to research laboratories. Discussion of parasite detection would not be possible without including methods for parasite sampling, concentration, and purification because it is often necessary to process large sample volumes prior to analysis, and no reliable methods are available for significantly amplifying parasites in vitro. Reviewing proven methods currently in use will provide a baseline for generating, accepting and implementing the more sensitive and specific methods under development today.     

Effects on animal performance and sward composition of mixed and sequential grazing of permanent pasture by cattle and sheep

Previous experiments have shown that mixed or conjoint grazing, when two or more animal species are grazed together, can lead to improved performance of one or more of the species and a higher total output per unit area. Sequential grazing systems, when different animal species graze an area in succession, also have the potential to improve productivity. This experiment directly compared these two approaches for integrating the grazing of cattle and sheep when pastured on improved permanent pasture. Four treatments were compared: 1) sheep only from May to October (S/S); 2) cattle only from May to July followed by sheep only from August to October (C/S); 3) cattle and sheep from May to July, sheep only for the rest of the growing season (C + S/S); and 4) cattle and sheep from May to October (C + S/C + S). Each treatment was replicated three times. From May until weaning at the end of July the plots were grazed by steers and ewes and lambs, and from weaning until October by steers and lambs. Sward heights were maintained at 6 cm using a “put and take” stocking system. Animal performance and sward composition data were collected during three growing seasons, 2001–2003. During the pre-weaning period lambs grazing plots which were grazed only by sheep had significantly poorer growth rates than those grazing plots where there was mixed grazing. Lambs grazing the sheep only plots also had lower liveweight gain during the post-weaning period, with the highest growth rates being recorded on the C + S/C + S treatment. Carrying capacity and total liveweight gain per unit area post-weaning were also consistently higher for the C + S/C + S treatment, while carrying capacity pre-weaning was highest for the C/S treatment. Measurements of clover content in the grazed horizon and botanical separation of material from quadrat cuts indicated that even under relatively controlled conditions choice of grazing system can influence sward composition. However, there was no clear link between any single sward change and the growth of the animals, indicating that the improved performance of cattle and sheep under mixed grazing is the result of a combination of factors, rather than a response to a particular sward parameter.     

Effect of different dietary ratios of sunflower and linseed oils on growth and carcass traits of rabbits

As part of an experiment aiming to modify the meat fatty acid profile, this work studied the growth and carcass traits as affected by various dietary ratios of sunflower oil and linseed oil. A diet without added oil served as a control (C). Four other diets were equally 4% oil-enriched but they differed in the incorporation ratios of sunflower oil (S) to linseed oil (L), i.e. 4% S to 0% L (diet 4%S), 3% S to 1% L (diet 3:1%SL), 2% S to 2% L (diet 2:2%SL) and 0% S to 4% L (diet 4%L). The oil-rich diets had slightly higher digestible energy contents (11.4 vs 10.6 MJ/kg) than the C feed. In each group 10 litters of 7 to 9 Pannon White kits per litter were studied in the pre-weaning period from 21 to 35 days old. Growth and slaughter traits were assessed with 50 and 30 rabbits per group, respectively. No significant effects of diets were found on litter and doe performances. The only significant differences in growth performance of the C, 4%S, 3:1%SL, 2:2%SL and 4%L rabbits were for the 35–49 day feed intake (88, 86, 84, 84 and 83 g per day, respectively, P = 0.046), the 35–84 day growth rate (36, 38, 37, 35 and 37 g/day, P = 0.034) and the 84-day body weight (2608, 2703, 2664, 2565 and 2628 g, respectively, P = 0.022). There were several significant differences in carcass traits including the weight of reference carcass (1357, 1391, 1388, 1380 and 1369 g, respectively, P = 0.004) and left longisimus dorsi meat (78, 79, 81, 81 and 76 g, respectively, P = 0.046) of rabbits. The diets had major effects on the L*, a* and b* colour values (lightness, redness and yellowness) of meat and fat. Carcass colour of the C and 4%S rabbits was closer and the 4%L rabbits was further from the European consumer's preference of light coloured, less red and slightly yellow rabbit meat. Our result reveals the importance of age and body weight at slaughter. Taking the growth and slaughter performances and, the recent belief of human health benefits from lower n− 6/n− 3 FAs dietary ratios into account, the 2:2%SL diet seems most appropriate if the interests of the raisers, meat processors and buyers are considered equally.     

Population structure and genetic diversity of worldwide Nova Scotia Duck Tolling Retriever and Lancashire Heeler dog populations

The aim of this study was to research the population structure and genetic diversity of the Nova Scotia Duck Tolling Retriever (NS) and the Lancashire Heeler (LH) dog breeds. Data consisted of nearly all the worldwide registration history for both breeds, including 28 668 NS and 4 782 LH individuals. A reference population, including the females born between 1999 and 2008, was defined for genetic analyses for each breed. Average depth of the pedigrees known for the reference population dogs was 12.9 complete generation equivalents in the NS and 6.0 in the LH. Only a small fraction of the born dogs were used later for breeding. Effective number of founders was 9.8 in the NS and 15.2 in the LH. More than 50% of the genetic diversity in the reference population was explained by two ancestors in the NS and five in the LH. Average inbreeding coefficients in the reference populations were 0.26 in the NS and 0.10 in the LH. Average kinships were 0.26 and 0.08 and realised effective population sizes 18 and 28, respectively. Failure to use available genetic resources for sustainable breeding has resulted in depletion of genetic variation in both breeds. To increase genetic variation, a larger proportion of the dogs should be used in reproduction and the contributions of reproducing animals should be equalized. In the LH, it is necessary to use the unregistered farm dogs in breeding. In the NS, crosses with another breed are needed.     

Accidental entrapment of cats in front-loading washing machines

Two clinical cases of accidental entrapment of cats in front-loading washing machines are described. One cat died the day after presentation as a result of aspiration pneumonia and head trauma, despite supportive care. The second cat survived with supportive treatment, but developed dermatologic complications 10 d later.