The transition period in dairy cows (3 weeks prepartum until 3 weeks postpartum) is associated with substantial mobilization of energy stores, which is often associated with metabolic diseases. Nicotinic acid (NA) is an antilipolytic and lipid-lowering compound used to treat dyslipidaemia in humans, and it also reduces non-esterified fatty acids in cattle. In mice the G-protein coupled receptor 109A (GPR109A) ligand NA positively affects the secretion of adiponectin, an important modulator of glucose and fat metabolism. In cattle, the corresponding data linking NA to adiponectin are missing. Our objective was to examine the effects of NA on adiponectin and AMPK protein abundance and the expression of mRNAs of related genes such as chemerin, an adipokine that enhances adiponectin secretion in vitro. Differentiated bovine adipocytes were incubated with pertussis toxin (PTX) to verify the involvement of GPR signaling, and treated with 10 or 15 µM NA for 12 or 24 h. NA increased adiponectin concentrations (p ≤ 0.001) and the mRNA abundances of GPR109A (p ≤ 0.05) and chemerin (p ≤ 0.01). Pre-incubation with PTX reduced the adiponectin response to NA (p ≤ 0.001). The NA-stimulated secretion of adiponectin and the mRNA expression of chemerin in the bovine adipocytes were suggestive of GPR signaling-dependent improved insulin sensitivity and/or adipocyte metabolism in dairy cows.

SUM M ARYThe current study was conducted to determine chemical composition, nutrient content and availability, metabolizable energy (ME) content and nutritive value of sainfoin hay for ruminants. Three ruminally cannulated Holstein cows were used for in situ and in vivo experiments, to determine rumen degradability and digestibility of sainfoin hay. Apparent total tract digestibility of nutrients was determined with feeding of sainfoin hay as the sole diet to achieve 10% more than maintenance energy requirements. Six Zandi ewes were used in the palatability experiment. Means for dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF) and condensed tannins (CTs) of sainfoin hay were: 940·4 g/kg and 93·43, 12·13, 47·87, 43·33 and 2·13 g/kg DM, respectively. In situ effective degradability of CP and DM were 0·38 and 0·54 g/g with a ruminal outflow rate of 0·05/h, respectively. OM apparent digestibility was in the range of 0·592-0·689, respectively, for Tilley & Terry and total faecal collection assays. ME content of sainfoin hay, according to different methods (gas production, in vitro and in vivo determined digestible organic matter in dry matter (DOMD)) was in the range 6·87-10·11 MJ/kg DM. Metabolizable protein (MP) content was 483·4 g/kg CP. Sainfoin was more palatable than alfalfa for sheep. It was concluded that sainfoin has a potential use in ruminant rations, especially if environmental conditions are not suitable for alfalfa production.

This study aimed to evaluate the effects of different supplemental fat sources [soybean oil (SBO) as a source of n-6 fatty acid and fish oil (FO) as a source of n-3 fatty acids] in the starter feed of milk-fed dairy calves during the hot season. Forty Holstein calves (3 d of age; 39.67 kg of body weight; ten calves per group) were randomly assigned to the experimental treatments as follows: (1) starter feed supplemented with no fat source (CON), (2) starter feed supplemented with 3% SBO (DM basis), (3) starter feed supplemented with 3% FO (DM basis), and (4) starter feed supplemented with an equal mixture of SBO and FO (1.5% each, DM basis). The milk feeding schedule was constant for treatments and all calves were weaned on d 65 of age. Results show that calves had greater starter intake, average daily gain, and body length when fed SBO compared to other treatments. However, feed efficiency was increased and inflammatory indicators (tumor necrosis factor-alpha, serum amyloid A and haptoglobin) concentrations were reduced in the calves fed FO compared to the other treatments. In summary, it was revealed that SBO rich in n-6 FA improved starter intake and growth performance, while FO rich in n-3 FA could improve the immune function of calves. Due to the current experimental condition, an equal mixture of SBO and FO (1.5% each, DM basis) can be recommended to have an optimum growth performance and immune function while the calves are reared under the heat conditions.

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Context Interest in studying heat stress (HS) has increased significantly due to the problems associated with increasing global warming. Heat stress has very destructive effects on the health and performance of livestock. Aims Our objective was to investigate the effects of heat stress on in vivo and in vitro ruminal metabolism in fat-tailed Iranian sheep. Methods Fourteen intact non-lactating and non-pregnant mature fat-tailed Makoei ewes (67.5 ± 2.5 kg BW) were kept indoors for 24 h/day and randomly assigned to HS (33.0–41.0°C and a temperature–humidity index (THI) of ≥83 for 24 h/day) or thermoneutral (TN; 24.5 ± 2.3°C and a THI of 66.1 ± 2.5) condition in two consecutive experimental periods. At the end of first experimental period, the animals in each group were exchanged with another group. The ewes were fed a total mixed ration two times a day, composed of lucerne hay (33%) and corn silage (1:2) to meet their maintenance metabolisable energy and protein requirements. Key results HS ewes had lower dry-matter (DM) intake than did TN ewes (P < 0.05). HS increased the in vivo DM, organic matter (OM) and neutral detergent fiber digestibility (P < 0.05), but crude protein digestibility was not affected. Total volatile fatty acid concentration and pH were not affected by HS. However, propionate molar percentage was increased and N-NH3 concentration was decreased by HS. In vitro gas production of three different tested feeds was lower in rumen fluid collected from HS than that from TN group, but DM and OM digestibility and methane emission were decreased only in the case of Orchard grass (P < 0.05). Conclusions and implications In general, HS had detrimental effects on DM intake and in vitro nutrient digestibility but increased in vivo nutrient digestibility, and changed microbial population.

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Series of in vitro trials were conducted to evaluate dose–response effects of walnut leaf ethanolic extract (WLEE) on ruminal fermentation, microbial populations, mitigation of methane emission and acidosis prevention. The treatments were conducted according to a 5 × 3 factorial arrangement in a completely randomised design formulated to contain corn (corn-based diet, CBD) and barley grain (barley-based diet, BBD), or equal amounts of barley and corn (barley and corn diet, BCD), consisting of either basal diets alone (0) or basal diets with 250, 500, 750 or 1000 µL of WLEE (W0, W250, W500, W750 and W1000 respectively) per litre of buffered rumen fluid. Three fistulated cows fed diets containing alfalfa hay and concentrate mixes (same as the control diet) plus minerals and vitamins were used for collection of ruminal fluid. The asymptote of gas production and methane emission was decreased and lag time increased in a linear and quadratic manner with an increasing dose of WLEE (P &lt; 0.001). However, gas production rate reduced linearly as WLEE dose increased (P &lt; 0.001). Methane production was significantly reduced linearly (L) and quadratically (Q) when walnut ethanolic extract was increased from 250 to 1000 μL/L (L and Q; P &lt; 0.001). The addition of WLEE significantly altered the volatile fatty acid profile in comparison to control, reducing the molar proportion of acetate and increasing that of propionate (P &lt; 0.001), and also decreased the ammonia-N concentration (L, P &lt; 0.001). Dry-matter and organic-matter in vitro digestibility coefficients were negatively affected by WLEE supplementation (L and Q; P &lt; 0.001). Although anti-acidosis potential of WLEE was significantly lower than that of monensin, W1000 increased medium culture pH compared with uncontrolled acidosis and the lower doses of WLEE. The populations of Fibrobacter succinogenes, Ruminococcus flavefaciens and R. albus were significantly reduced by WLEE, although to different magnitudes, depending on the corn and barley grain proportions in the diet. Results of the present study indicated that increasing addition levels of WLEE have noticeable effects on rumen microbial population and fermentation characteristics. It can be concluded that WLEE can potentially be used to manipulate ruminal fermentation patterns.

Rumen fluid from slaughtered animals is one of the wastes of slaughterhouses released to the environment that, due to its high nitrogen and phosphorus contents, can lead to soil and groundwater pollution. Meanwhile, it contains ruminal microbes and some bioactive compounds such as enzymes, minerals, vitamins and organic acids. This study was designed to examine the potential of rumen fluid as a feed additive. Therefore, the effects of spray-dried rumen fluid (SDR) with 1% maltodextrin on the performance, blood metabolites and some cytokines of sucking dairy calves during the pre-weaning phase were investigated. Forty male Holstein calves, with a mean weight of 39.4 ± 3.7 kg and 7 ± 1 days old, were randomly assigned to four groups (n = 10 calves per group) in a completely randomized design. Experimental treatments were: control diet with no additive (CON); control diet with 0.5 g/day of SDR (SDR0.5); control diet with 1 g/day of SDR (SDR1); and control diet with 1.5 g/day of SDR (SDR1.5). Daily feed intake and average daily gain of calves were not affected by feeding SDR as a feed additive. Cholesterol concentration was significantly affected by the 20th and 40th days of the experiment and decreased linearly by increasing SDR feeding level. Levels of liver enzymes, including aspartate aminotransferase and alanine aminotransferase, in the blood decreased by feeding SDR at day 40 of the experiment. Serum concentration of interleukin-6 at day 20 was not affected by dried rumen fluid feeding, whereas at day 40, a significant effect was observed among experimental treatments. The lowest value was recorded for SDR1.5 v. control calves. At day 20, the serum concentration of interferon-γ was influenced by supplementing SDR, and the highest value was recorded for SDR1.5 calves. The inclusion of SDR with 1% maltodextrin in suckling dairy calves had beneficial effects on the stimulation of calves’ immune system.