High leptin in pregnant mink (Mustela vison) may exert anorexigenic effects: a permissive factor for rapid increase in food intake during lactation

Risk factors associated with diarrhea in Danish commercial mink (Neovison vison) during the pre-weaning period

BACKGROUND

Pre-weaning diarrhea in mink, also known as "sticky kits", is a syndrome and outbreaks occur every year on commercial mink farms in all mink producing countries. Morbidity and mortality can be considerable on a farm with huge economic consequences for the farmer as well as compromised welfare for the mink kits. Although efforts have been taken to identify etiologic agents involved in outbreaks, the syndrome is still regarded as multifactorial and recurring problems on the same farms draw attention to management and environmental risk factors. In the pre-weaning period from May to June 2015, a case control study was carried out on 30 Danish mink farms. Data concerning management, biosecurity, hygiene, feed consumption, antibacterial prescription and production efficiency were analyzed.

RESULTS

The proportion of 1-year old females, farm size (total number of females), energy supply per female in the late gestation period, and dogs accessing the farm area were significantly associated with being a case farm. Case farms were prescribed almost twice the amount of antibacterials per gestational unit (female and litter) as in control farms. Farmers on case farms spent significantly more time nursing and treating the animals and experienced more females with mastitis compared to farmers on control farms. No significant differences in cleaning practices or hygienic measures between case and control farms were found and there were no differences in drinking water quality, bedding material, composition neither of color types nor in management regarding litter equalization.

CONCLUSIONS

Results from this study showed an association between the occurrence of pre-weaning diarrhea on mink farms and parity profile, farm size and feeding intensity in the gestational period. The access of dogs to the farm area was a significant risk factor, but needs further clarification.

Endocrinologic Adaptations to Wintertime Fasting in the Male American Mink (Mustela vison)

The aim of this study was to investigate the endocrine response to wintertime starvation in the male American mink (Mustela vison) fasted for 16 hrs, 2 days, 3 days, 5 days, or 7 days (n–10 per group). After 2 days of fasting, the plasma leptin concentrations decreased, along with the triiodothyronine, testosterone, and progesterone levels, and the blood monocyte counts. Leptin also seems to trigger the response to fasting in mustelids by inducing immunosuppression and downregulation of the reproductive and thyroid axes. The dramatic increase in the peptide YY concentrations after 3 days of fasting may be required to suppress gastrointestinal processes during food scarcity. The plasma insulin levels decreased, and those of glucagon increased after 5 days of fasting in association with efficient glucose sparing and lipid mobilization. Body energy stores cannot be wasted for growth during nutritional scarcity and, thus, the growth hormone levels of the minks decreased after 5 days of fasting. The plasma noradrenaline and cortisol concentrations also decreased after 3 and 7 days without food, respectively. The plasma ghrelin, adiponectin, resistin, thyroxine, adrenaline, or estradiol levels did not respond to fasting. The endocrine response to food deprivation is remarkably similar in divergent mammalian orders, indicating that the hormonal signals enhancing survival during nutritional scarcity must be evolutionarily old and well conserved.

Play in juvenile mink: litter effects, stability over time, and motivational heterogeneity

Mink are potentially ideal for investigating the functions of play: deleterious effects of early social isolation suggest a crucial developmental role for play; and huge numbers of highly playful juvenile subjects can be studied on farms. We collected descriptive data on 186 pairs from 93 litters, half provided with play-eliciting environmental enrichment objects in their home cages, to test three hypotheses: (1) play frequency is subject to litter effects; (2) relative playfulness is stable over time; (3) play sub-types share a single, common motivational basis. We found weak litter effects that were driven by stronger litter effects on general activity, and weakly stable individual differences in both total and rough-and-tumble play. Experimentally increasing object play did not inhibit rough-and-tumble play, showing these sub-types are not motivational substitutes. Frequencies of these sub-types were also uncorrelated, and changed differently with time of day and age, further supporting this conclusion.

Effects of dietary protein level on nutrients digestibility and reproductive performance of female mink (Neovison vison) during gestation

The objective of this study was to determine whether nutrient digestibility and reproductive performance of pregnant mink (Neovison vison) were affected by different dietary protein levels. One hundred and twenty female mink were randomly assigned to four groups, receiving diets of fresh material with different protein levels. The dietary protein levels, expressed as percentage of dry matter (DM), were 32, 36, 40 and 44% respectively. These values corresponded to average 320, 360, 400 and 440 g protein/kg DM, respectively. Results were as follows. All of crude protein digestibility, nitrogen (N) intake, N retention increased along with dietary protein level increasing. Low protein level (32%) significantly reduced the above indicators (P < 0.05). DM digestibility and ether extract digestibility were not affected by dietary protein level. Results of mated females, barren females, kids per litter, live born kids per mated female, birth survival rate, and birth weight showed that mink achieved optimal reproductive performance when dietary protein level was 36%. In conclusion, dietary protein was anticipated to significantly influence some nutrients' utilization. Adopting the appropriate dietary protein level allow better reproduction performance. The most preferable reproductive performance was achieved when diet contained 275.5 g digestible protein per kg DM for female mink in gestation.

Low protein provision during the first year of life, but not during foetal life, affects metabolic traits, organ mass development and growth in male mink (Neovison vison)

Low protein provision in utero and post-partum may induce metabolic disorders in adulthood. Studies in mink have mainly focused on short-term consequences of low protein provision in utero whereas the long-term responses to low protein (LP) provision in metabolically programmed mink are unknown. We investigated whether low protein provision in utero affects the long-term response to adequate (AP) or LP provision after weaning in male mink. Eighty-six male mink were exposed to low (19% of ME from CP; crude protein) or adequate (31% of ME from CP) protein provision in utero, and to LP (~20% of ME from CP) or AP (30-42% of ME from CP) provision post-weaning. Being metabolically programmed by low protein provision in utero did not affect the response to post-weaning diets. Dietary protein content in the LP feed after weaning was below requirements; evidenced by lower nitrogen retention (p < 0.001) preventing LP mink from attaining their growth potential (p < 0.02). LP mink had a lower liver, pancreas and kidney weight (p < 0.05) as well as lower plasma IGF-1 concentrations at 8 and 25 (p < 0.05) weeks, and a higher incidence of hepatic lipidosis at 25 weeks (p < 0.05). Furthermore, LP mink had a higher body fat (p < 0.05) and lower body CP content (p < 0.05) at 50 weeks of age. It is concluded that some effects of low protein provision in utero can be alleviated by an adequate nutrient supply post-partum. However, long-term exposure to low protein provision in mink reduces their growth potential and induces transient hepatic lipidosis and modified body composition.

Effect of late gestation low protein supply to mink (Mustela vison) dams on reproductive performance and metabolism of dam and offspring

Protein malnutrition in utero that induces permanent changes in metabolism has been investigated intensively in various animals in recent years, but to the best of our knowledge, not yet in the mink, a strict carnivore. In the present study, minks were fed either a low-protein (LP) diet, i.e., with a protein:fat:carbohydrate ratio of 14:51:35% of metabolisable energy (ME), or an adequate-protein diet (AP), i.e. 29:56:15% of ME, from when implantation was completed until parturition (17.9 +/- 3.6 days). Respiration and balance experiments were performed during both gestation and lactation. Plasma concentrations of leptin, IGF-1, and insulin were determined by radioimmunoassay; the relative abundances of glucose-6-phosphatase (G-6-Pase), fructose-1,6-bisphosphatase (Fru-1,6-P2ase), phosphoenol-pyruvate carboxykinase (PEPCK), and pyruvate kinase (PKM2) were determined in liver, and abundances of adiponectin and leptin in adipose tissue were determined by real-time quantitative PCR (q PCR). The protein supply only affected quantitative metabolism traits during the period of differentiated feeding. The dietary composition was reflected in the nitrogen metabolism and substrate oxidation, but no effects remained during lactation. The LP dams tended to have a smaller liver mass in relation to body weight than did AP dams (2.5% vs. 2.9%; p = 0.09), significantly less leptin mRNA (p < 0.05), and 30.6% fewer kits per mated female (p = 0.03). Furthermore, F1-generation kits exposed to protein restriction during foetal life (FLP1; 10.3 g) had a lower birth weight (p = 0.004) than did F1-generation kits exposed to adequate protein (FAP1; 11.3 g). Differences remained significant until 21 days of age (120.4 g vs. 127.6 g; p = 0.005). The FLP1 foetuses displayed a lower abundance of Fru-1,6-P2ase mRNA (p = 0.007) and of PKM2 mRNA (p = 0.002) than did FAP1 foetuses. Whether these changes during foetal life cause permanent changes in the glucose homeostasis of the offspring and result in the transmission of epigenetic phenotypic changes, as seen in the rat, needs further investigation.

Feeding mink (Neovison vison) a protein-restricted diet during pregnancy induces higher birth weight and altered hepatic gene expression in the F(2) offspring

Malnutrition during foetal life can induce modifications in the phenotype of an individual. The present study aimed to observe effects of low foetal life protein provision on modifications of the phenotype and changes in the progeny of 1-year-old female mink (F(1) generation) offspring of mothers fed a low-protein diet. Traits studied included reproductive performance, energy and protein metabolism, and key hepatic enzymes associated with glucose homeostasis and metabolic hormones. The F(0) generation offspring were fed either a low-protein (14 % of metabolisable energy (ME) from protein - FLP1) or an adequate-protein (29 % of ME from protein - FAP1) diet for the last 17.9 (sd 3.6) d of gestation. The F(1) dams were studied at birth and at 1 year of age, during their first reproductive cycle, after maintenance on an adequate diet from birth and thereafter. Metabolic traits during gestation and lactation were largely unaffected by foetal life protein provision, but birth weight in the F(2) generation was higher (P = 0.003) among FLP2 kits than among FAP2 kits. Furthermore, the relative abundance of pyruvate kinase mRNA was significantly (P = 0.007) lower, and fructose-1,6-bisphosphatase mRNA tended (P = 0.08) to be lower in FLP2 foetuses than in FAP2 foetuses, showing some similar difference in the F(2) generation and F(1) generation foetuses, suggesting an effect on some hepatic enzymes affecting glucose homeostasis being transmitted from the F(1) to the F(2) generation. These findings indicate that even though energy and nitrogen metabolism displayed no effect of protein provision during early life, programming effects still appeared at the molecular level in the following generation.