The effect of long term under- and over-feeding of sheep on milk and plasma fatty acid profiles and on insulin and leptin concentrations

Abstract

<jats:p>Since sheep's milk is mainly used for cheese making and milk chemical composition and fatty acids (FA) profile affect cheese yield and quality, the objective of this study was to determine the effects of different feeding levels on milk chemical composition and FA profile, as well as on plasma FA profile, and on insulin and leptin concentrations. Twenty-four sheep were assigned to three homogeneous sub-groups. Throughout the experimental period each group was fed the same diet but in quantities which met 70% (under-feeding), 100% (control) and 130% (over-feeding) of their respective energy and crude protein requirements. The results showed that the underfed sheep had higher milk fat content compared with overfed. In blood plasma the concentrations of C<jats:sub>18:0</jats:sub>and C<jats:sub>18:1</jats:sub>in the underfed sheep were significantly higher compared with control and overfed sheep. The concentrations of leptin and insulin were significantly higher in overfed compared with underfed sheep. Underfeeding reduced the concentrations of short chain FA (SCFA) and medium chain FA (MCFA) and increased that of C<jats:sub>18:0</jats:sub>and mono unsaturated FA (MUFA) in sheep milk fat compared with controls and overfed. The concentrations of C<jats:sub>18:0</jats:sub>, long chain FA (LCFA) and monounsaturated FA (MUFA) in milk were significantly higher and those of SCFA, MCFA and saturated FA (SFA) significantly lower in the underfed compared with the overfed sheep. In conclusion, long term under- and over-feeding affected the sheep milk chemical composition and FA profile which consequently has an impact on milk products yield (cheese and yogurt) and quality (human health).</jats:p>

The effects of diet and arginine treatment on serum metabolites and selected hormones during the estrous cycle in sheep

“…Results from our study report that U ewes had approximately 2-fold less serum leptin compared with C ewes, whereas the O ewes had 2.5-fold more leptin than the C ewes. These results are consistent with other studies reporting enhanced leptin concentrations in overfed nonpregnant animals compared with control and/or underfed nonpregnant animals [10,19,45,71,74,75]. We also observed that leptin concentrations were less in mid-luteal phase than at estrus or early luteal phase in overfed ewes, suggesting that leptin is involved in the regulation of the estrous cycle.…”

“…Because insulin is influenced by dietary intake, overfeeding and underfeeding can drastically impact insulin concentrations in circulation [9,12]. In nonpregnant ewes, serum insulin levels were increased in ewes fed excess diet compared with restricted or maintenance control diets [13,14,19,59]. These results are consistent with the results from our study wherein serum insulin concentrations were increased in O ewes and reduced in U ewes.…”

“…In ruminants, overfeeding caused an increase in ovulation rates and insulin, IGF1, and leptin concentrations [3,6,7,17], whereas underfeeding decreased insulin and leptin serum concentrations [13,18,19]. Furthermore, circulating P4 concentration in ruminants can be affected by diet [8,20].…”

The impact of diet and arginine supplementation on pancreatic mass, digestive enzyme activity, and insulin-containing cell cluster morphology during the estrous cycle in sheep

“…Insulin concentration in serum was greater in OF than CON and UF ewes in the current study. Similarly, greater insulin concentration in overfed and lower insulin concentration in underfed animals were reported by others [10,23,[32][33][34][35]. In this study serum insulin concentration was not affected by treatment with Arg.…”

Effects of Inclusion of Schizochytrium spp. and Forage-to-Concentrate Ratios on Goats’ Milk Quality and Oxidative Status

“…The plasma fatty acid analysis was carried out with the method of Bondia-Pons et al [25] as previously described by Tsiplakou et al [26]. Milk samples were analyzed for fatty acid according to the method of Nourooz-Zadeh and Appelqvist [27] as described by Tsiplakou et al [28].…”