Metabolic and hormonal control of energy utilization and partitioning from early to mid lactation in Sarda ewes and Saanen goats.

In a recent study, we observed that starch-rich diets used in mid lactation induced lower milk production persistency and higher body fat accumulation in dairy ewes compared with dairy goats. Because these species differences could be linked to hormonal mechanisms that drive energy partitioning, in the same experiment, we explored the evolution of metabolic and hormonal status during lactation to test this hypothesis. Twenty mature Sarda dairy ewes and 20 mature Saanen goats [15-134 ± 11 d in milk (DIM), mean ± SD] were compared simultaneously. In early lactation, each species was allocated to one dietary treatment: high-starch diet [HS: 20.4% starch, on dry matter (DM) basis], whereas from 92 ± 11 DIM, each species was allocated to 1 of 2 dietary treatments: HS (20.0% starch, on DM basis) and low-starch (LS: 7.8% starch, on DM basis) diets. Blood samples were collected in the morning to analyze glucose, nonesterified fatty acids (NEFA), growth hormone (GH), insulin, and insulin-like growth factor I (IGF-I). Data were analyzed using the PROC MIXED procedure of SAS with repeated measurements (SAS Version 9.0). The HS and LS diets applied in mid lactation did not affect metabolic status of the animal within species; thus, only a comparison between species was carried out. From early to mid lactation, plasma glucose concentration was higher in ewes than in goats (54.57 vs. 48.35 ± 1.18 mg/dL), whereas plasma NEFA concentration was greater in goats than in ewes (0.31 vs. 0.25 ± 0.03 mmol/L). Goats had higher plasma GH concentration and lower plasma insulin content than ewes (4.78 vs. 1.31 ng/mL ± 0.47; 0.11 vs. 0.26 µg/L ± 0.02). Plasma IGF-I concentration did not vary between species. The comparison of metabolic and hormonal status of lactating Sarda dairy ewes and Saanen goats, carried out by studying simultaneously the 2 species in the same stage of lactation and experimental conditions, suggests that the higher insulin and glucose concentration observed in Sarda ewes explains why they partitioned more energy toward body reserves than to the mammary gland, especially in mid lactation. This can justify the negative effect of high-starch diets in mid-lactating Sarda ewes. Conversely, the highest GH and NEFA concentration observed in Saanen goats explain why they partitioned more energy of starch diets toward the mammary gland than to body reserves and justify the positive effect of high-starch diet in mid lactation. Together, these different responses contribute to explain why specialized dairy goats, such as the Saanen breed, have a higher milk production persistency than specialized dairy sheep breeds, such as the Sarda.

The effect of parity number on the metabolism, inflammation, and oxidative status of dairy sheep during the transition period.

The objective of this study was to evaluate whether dairy sheep during the transition period are affected by their parity numbers with regard to (1) body weight (BW), body condition score (BCS), and production performance (milk yield and composition) and (2) metabolic, inflammation, and stress biomarkers. For this purpose, 30 Sarda dairy ewes [15 primiparous (PRP) and 15 multiparous (MUP) ewes] were recruited on d 90 of gestation. Each group was homogeneous according to age, BW, and BCS. Sampling was carried out at -60, -30, -7, 0, +30, and +60 d from lambing. The MUP ewes showed a higher BW (46.32 vs. 38.71 kg) and larger litter size (1.45 vs. 1.06 kg) but a lower BCS (2.47 vs. 2.70) than the PRP ewes. Furthermore, the MUP ewes had lower concentrations of glucose (3.49 vs. 4.27 mol/L), cholesterol (1.63 vs. 1.81 mmol/L), free fatty acids (0.47 vs. 0.62 mmol/L), and triglycerides (0.22 vs. 0.25 mmol/L) compared with PRP ewes. With regard to inflammation and oxidative stress parameters, the PRP group had higher haptoglobin (0.48 vs. 0.18 g/L) and paraoxonase (187.90 vs. 152.11 U/L) activity than the MUP group. Overall, the MUP ewes were characterized by greater milk production performance and greater feed intake, resulting in a better energy balance, than the PRP ewes. Interestingly, these findings highlighted a different metabolic and inflammatory response over the transition period between PRP and MUP ewes, with the latter displaying lower concentrations of inflammatory-related biomarkers.

Excretion pattern of aflatoxin M1 in milk of goats fed a single dose of aflatoxin B1.

The feedstuffs used in dairy animals must be able to give consumers confidence about the wholesomeness of milk with regard to aflatoxin contamination. The aim of this study was to determine the excretion patterns of aflatoxin M(1) (AFM1) in the milk of dairy goats fed a single dose of pure aflatoxin B(1) (AFB1), which can occasionally occur if feeds are infected by hot-spot growth of molds that produce aflatoxins. Five dairy goats in midlactation were administered 0.8 mg of AFB1 orally. Individual milk samples were collected for 84 h after AFB1 dosage. Aflatoxin M(1) was found in milk in the highest concentration. In all goats, AFM1 was not detected in milk before AFB1 administration, but was detected in the first milking following AFB1 administration. The excretion pattern of AFM1 concentration in milk was very similar in all goats even if the values of the concentration differed between animals. The peak values for AFM1 concentration in milk was observed in milk collected during the milking at 3 and 6h. After the peak, the AFM1 in milk disappeared with a trend that fitted well a monoexponential decreasing function, and the toxin was not detected after 84 h. Only about 0.17% of the amount of AFB1 administered was detected as AFM1 in milk, and about 50% of this was excreted in the first liter of milk yielded after AFB1 intake. Correct procedures to prevent growth of molds, and consequent AFB1 contamination, on the feedstuffs for lactating goats represent the key to providing consumers a guarantee that milk is not contaminated by AFM1.

The effect of dietary iodine supplementation in dairy goats on milk production traits and milk iodine content.

Dairy products offer an important source of iodine for humans, particularly infants and children. An adequate iodine content in the diet of lactating animals must guarantee a suitable milk iodine concentration. In this experiment, the effects of iodine supplementation of dairy goat diets on the iodine concentration, milk yield, and milk composition of goat milk were studied. Thirty crossbred dairy goats of the Sarda population were divided into 3 groups supplemented with 0 (control group), 0.45 (group 1), or 0.90 (group 2) mg of KI/d per goat. The dose of KI (76.5% of iodine) was dissolved in water and orally administered with a syringe every day for 10 wk. Mean milk iodine concentrations were 60.1 +/- 50.5, 78.8 +/- 55.4, and 130.2 +/- 62.0 microg/L (mean +/- SD) in the control group, group 1, and group 2, respectively. The extent of iodine enrichment in milk was approximately 31% in group 1 and 117% in group 2 compared with the control group. Milk yield was not influenced by KI supplementation and averaged 1,229, 1,227, and 1,179 g/d in groups 0, 1, and 2, respectively. Milk urea nitrogen concentration was significantly lower in the KI-supplemented groups (32 and 33 mg/dL in groups 1 and 2, respectively) than in the control group (37 mg/dL). Iodine supplementation of dairy goat diets can increase milk iodine content without adverse effects on milk production traits.

Milk and cheese fatty acid composition in sheep fed Mediterranean forages with reference to conjugated linoleic acid cis-9,trans-11.

Two experiments were undertaken to evaluate the effect on milk and cheese fatty acid composition of feeding different fresh forages to dairy sheep both in winter (experiment 1, growing stage of the forages, early lactating ewes) and in spring (experiment 2, reproduction stage of the forages, midlactating ewes). Four forage species were compared: annual ryegrass (RY, Lolium rigidum Gaudin), sulla (SU, Hedysarum coronarium L.), burr medic (BM, Medicago polymorpha L.), and a daisy forb (CH, Chrysanthemum coronarium L.). The forages were cut twice daily and offered ad libitum to 4 replicate groups of Sarda dairy sheep (groups RY, SU, BM, and CH). The CH forage was particularly rich in linoleic acid in both periods, whereas BM and SU forages were rich in linolenic acid in winter and spring, respectively. Milk fatty acid composition was affected by the forage in both experiments. Milk conjugated linoleic acid and vaccenic acid contents were higher in CH and BM groups (winter) and CH group (spring) than in the other groups. No differences were observed when comparing fatty acid profile between milk, 1-d-old cheeses, and 60-d-old cheeses within experimental groups, suggesting that the fatty acid recovery rates during cheese making and ripening were not affected by the feeding regimens. After stepwise discriminant analyses of the pooled data, the milks and cheeses sourced in the different feeding regimens differed among them. Based on these results, we conclude that it is possible to manipulate the fatty acid profile of sheep dairy produce to maximize the content of beneficial fatty acids by the use of appropriate fresh forage-based regimens.

Group I afferent fibers: effects on cardiorespiratory system.

In anesthetized cats, we examined cardiorespiratory activity during excitation of large afferent fibers from muscle proprioceptors. We found that selective stimulation of group I fibers with electric impulses at 200-300 Hz induces an increase in pulmonary ventilation from control value (mean +/- SE) of 486 +/- 8 to a maximum of 544 +/- 8 ml/min and an increase in mean systemic arterial pressure from control value of 151 +/- 2 to a maximum of 160 +/- 2 mmHg. Neither of these increases was produced by the same stimulation when applied during anodal block of volleys of group I fibers. Hyperpnea could be obtained independently from changes in cardiovascular activity, and the pressor response could be obtained during artificial ventilation at constant tidal volume after curarization. Consequently, it appears that respiratory and cardiovascular responses to stimulation of group I fibers can be independent of each other.

Short-term dietary effects on reproductive wastage after induced ovulation and artificial insemination in primiparous lactating Sarda ewes.

Short-term effects of nutrition on conception rate (CR), ovulation rate (OR), ova and embryo losses (OEL) during the first 50 days following insemination and total reproductive wastage after ovulation (TRW), were investigated in primiparous lactating Sarda ewes after oestrous synchronisation and cervical [corrected] artificial insemination (AI). Eighty ewes grazing a green high-quality pasture were offered one of three iso-energetic supplements from day 14 before to day 2 after AI: whole maize grain (M); soyabean meal (S); maize gluten meal (G); or served as controls (C). Supplements G and S were iso-nitrogenous but provided different amounts of rumen undegradable digestible protein. The intake of herbage and digestible dry matter, measured by the n560 mg/l was associated with lower CR. Ranking by ovulation groups of CR was single

Effect of dietary iodine on thyroid hormones and energy blood metabolites in lactating goats.

Aim of this work was to evaluate if long-term dietary supplementation of potassium iodide (KI) to dairy goats can influence metabolic and hormonal parameters. Thirty Sarda crossbred dairy goats were divided into three groups, which were orally administered 0 (control group; CON), 0.45 (low iodine group; LI) or 0.90 (high iodine group; HI) mg of KI/day, respectively. The daily dose of KI (76.5% of iodine) was administered as salt dissolved in water for 8 weeks. Plasma contents of nonesterified fatty acids (NEFA), urea, glucose, insulin, free triiodothyronine (FT(3)) and thyroxine (FT(4)) were determined weekly. Iodine supplementation increased significantly the FT(3) hormone (P = 0.007) and FT(3)/FT(4) ratio (P = 0.001) and tended to influence the FT(4) hormone (P = 0.059). An iodine level × week of sampling interaction for NEFA (P = 0.013) evidenced a temporary concentration increase in supplemented groups. The 'Revised Quantitative Insulin Sensitivity Check Index' increased with KI supplementation (P ≤ 0.01). Blood urea nitrogen (BUN) and insulin were lowered (P ≤ 0.01) by iodine supplementation (groups LI and HI; P ≤ 0.01). The glucose concentration evidenced an iodine level × week of sampling interaction (P = 0.025) due to an unexpected and temporary increase of its concentration in the CON group. Glucose concentration was decreased by KI supplementation only in LI group (P < 0.05). In conclusion, the daily supplementation of low doses of KI can improve insulin sensitivity and decrease BUN in dairy goats.

Reflex respiratory responses to continuous and intermittent stimulation of afferent fibres from muscles in cats.

In anaesthetized cats, reflex respiratory responses were evoked by electrically stimulating proximal ends of cut nerves to gastrocnemius-soleus muscles of the left hindlimb. The direction of these responses, in the excitatory or inhibitory sense, depended on the types of afferent fibres stimulated and on the mode of stimulation. Continuous stimulation, delivered with stimuli of 0.1 ms at 200 or 300 Hz, in all cases induced excitatory responses, consisting of increases in pulmonary ventilation, mainly caused by increases in tidal volume. Intermittent stimulation, which consisted of brief trains of stimuli repeated at 2-3 Hz, induced excitatory responses when afferent fibres with conduction velocities higher than 20 m/s were stimulated, while it induced inhibitory responses, consisting of decreases in pulmonary ventilation, tidal volume and respiratory frequency, when fibres with conduction velocities below 20 m/s were simultaneously stimulated with the high-conduction velocity fibres.

[Effect of phentolamine on the reflex increase in arterial pressure]. / Effetto della fentolamina sull'aumento riflesso della pressione arteriosa.

Experiments were carried out in anaesthetized and curarized cats to study the effects of the alpha-blocker phentolamine on arterial pressor response to stimulation of group I afferent fibers from gastrocnemius-soleus muscles. It has been found that increasing doses of phentolamine given i.v. cause a decreasing pressor response until complete disappearance occurs at 2.5 mg/Kg. It is concluded that pressor response is present only when the adrenergic control system is effective and, therefore, it is due mainly to an increase in peripheral vascular resistances.

Role of the heart and peripheral resistance in the reflex effect of group I afferent fibers on blood pressure.

Experiments were done on anesthetized and curarized cats to see whether the increase in blood pressure caused by electrical stimulation of group I afferent fibers is related to a direct reflex effect on the heart. The reflex effect of electrical stimulation of group I afferent fibers from the gastrocnemius-soleus muscles on the arterial pressure, the left ventricular pressure, the inotropic state of the left ventricle (dP50/dt) and the heart rate were compared before and after beta-blockade with propranolol (0.1 mg/kg intravenously) to reduce a possible direct effect on the heart. The same comparison was made before and after alpha-blockade with phentolamine (2.5 mg/kg intravenously) to keep the peripheral resistance constant. Electrical stimulation of group I afferent fibers caused an increase in the blood pressure, the left ventricular pressure and, to some extent, the inotropic state of the left ventricle and the heart rate. The beta-blockade had no significant effect on these increases, while the alpha-blockade abolished the increase in blood pressure. It is concluded that the effect of stimulation of group I afferent fibers on the blood pressure is not dependent on a direct reflex effect on the heart, but can be better explained by a reflex increase in the peripheral resistance.

[Behavior of the discharge of the Golgi tendon organs during subtetanic muscular contraction]. / Comportamento della scarica degli organi tendinei del Golgi durante la contrazione subtetanica muscolare.

In a series of isotonic muscle contractions induced by repetitive stimulation at frequencies higher than 0.1 Hz the pause in the afferent discharge of the muscle spindles tends to decrease as a function of time and as a function of frequency, while the afferent discharge of the Golgi tendon organs, as measured in the same experimental conditions, remains constant. The results support the hypothesis that the changes in the spindle are due to changes in the visco-elastic properties of the intrafusal muscle fibers (1). Since no muscolar tissue is present within the Golgi tendon organs (4) their afferent discharge and the pause, which occurs during the relaxation phase (3) do not change as seen in the spindles.

Group I fibers: pressor reflex and cardiac activity.

Experiments were performed on cats to see whether stimulation of group I afferent fibers from gastrocnemius-soleus muscles induced changes in cardiac activity, in addition to the increase in systemic arterial pressure already established. The results show that the increase in arterial pressure is accompanied by an increase in systolic left ventricular pressure, without any significant changes in cardiac inotropism and chronotropism. It is concluded that the cardiac innervation is not an important efferent pathway of the pressor reflex evoked by stimulating group I afferent fibers, and that the reflex increase in arterial pressure depends mainly on an increase in peripheral vascular resistance.

[Respiration during isometric contraction of the flexor or extensor muscles of the arm in humans]. / La ventilazione durante la contrazione isometrica dei muscoli flessori o estensori del braccio nell'uomo.

An increase in the instantaneous pulmonary flow and a decrease in the respiratory frequency has been found in man as a consequence of isometric contraction of either flexor or extensor muscles of the elbow. The delay of 200 to 900msec between the onset of the muscle contraction and the beginning of the flow increment suggests that the respiratory system increases its activity due to the proprioreceptor activation. As there is no significant difference in the results obtained during flexor or extensor contraction, the contribution of the two different receptor groups appears to be the same.

[Effects of passive movement of the arm on respiration in humans]. / Effetti del movimento passivo del braccio sulla respirazione nell'uomo.

Cyclic passive movements of the right arm at 1Hz induce an increase in pulmonary ventilation in man. This results from an increase in frequency of the respiratory cycles, mainly due to a shortening of the expiratory phase, and from an increase of the instantaneous flow. The delay between the beginning of the arm movements and the onset of the increase in flow is about 450msec.