Effect of tannin-containing hays on enteric methane emissions and nitrogen partitioning in beef cattle1.

The objective of this study was to determine whether feeding tannin-containing hays to heifers and mature beef cows influences enteric methane (CH4) emissions and nitrogen (N) excretion relative to feeding traditional legume and grass hays. Fifteen mature beef cows (Exp. 1) and 9 yearling heifers (Exp. 2) were each randomly assigned to treatment groups in an incomplete bock design with 2 periods and 6 types of hays with 3 hays fed each period (n = 5 cows and 3 heifers per treatment). Groups were fed tannin-containing [birdsfoot trefoil (BFT), sainfoin (SAN), small burnet (SML)] or non-tannin-containing [alfalfa (ALF), cicer milkvetch (CMV), meadow bromegrass (MB)] hays. Each period consisted of 14 d of adjustment followed by 5 d of sample collection. Nine cows and 9 heifers were selected for the measurement of enteric CH4 emissions (sulfur hexafluoride tracer gas technique), and excretion of feces and urine, while dry matter intake (DMI) was measured for all animals. The concentration of condensed tannins in SAN and BFT was 2.5 ± 0.50% and 0.6 ± 0.09% of dry matter (DM), respectively, while SML contained hydrolyzable tannins (4.5 ± 0.55% of DM). Cows and heifers fed tannin-containing hays excreted less urinary urea N (g/d; P < 0.001) and showed lower concentrations of blood urea N (mg/dL; P < 0.001) than animals fed ALF or CMV, indicating that tannins led to a shift in route of N excretion from urine to feces. Additionally, cows fed either BFT or CMV showed the greatest percentage of retained N (P < 0.001). Enteric CH4 yield (g/kg of DMI) from heifers (P = 0.089) was greatest for MB, while daily CH4 production (g/d) from heifers (P = 0.054) was least for SML. However, digestibility of crude protein was reduced for cows (P < 0.001) and heifers (P < 0.001) consuming SML. The results suggest that tannin-containing hays have the potential to reduce urinary urea N excretion, increase N retention, and reduce enteric CH4 emissions from beef cattle. The non-bloating tannin-free legume CMV may also reduce environmental impacts relative to ALF and MB hays by reducing N excretion in urine and increasing N retention.

Reporting temporal fluctuations of hepatic C16 and C18 fatty acids during late gestation and early lactation in dromedary camel.

Based on current knowledge, C16 and C18 fatty acids (FA) are considered the most functional FA in hepatic metabolism. Although these FAs have been satisfyingly investigated in cattle, other species such as camel have been neglected. For this reason, the current study was designed to scrutinize changing patterns of C16 and C18 FAs in 10 dromedary camels from the last 2 months of gestation to the first months of lactation. Camels were grazed on natural pasture and supplemented with a balanced ration. Liver biopsies were obtained through blind biopsy technique at about 60, 45, 30, and 15-day antepartum (AP), and at 3, 15, 30, 45, and 60 post-partum (PP). Data were analyzed by the ANOVA procedure of SPSS with repeated measurements. From 15-day AP, saturated FA content of the liver declined (P < 0.01) and 15-day PP reached its peak (P = 0.02). At 30-day PP it went down (P < 0.01), and re-elevated at 45-day PP (P < 0.01) but remained at a steady state for the duration of the study. Mono-unsaturated and polyunsaturated FA content of hepatic tissue were constant throughout AP, albeit observed to peak at 15-day AP compared with 45 (P = 0.04) and 30-day AP (P < 0.01) for mono-unsaturated FAs, and with 60-, 45-, and 30-day AP (P ≤ 0.01) for polyunsaturated FAs. The palmitic acid content of the liver reached a nadir at 30-day AP (P < 0.01), increased sharply (P < 0.01) at the next sampling time-point, and had a trend to escalate until 3-day PP. Palmitoleic acid levels were unchanged from 60- to 30-day AP, decreased at 15 AP and 3-day PP, increased at 15-day PP, then remained constant until the end of the study period (P ≤ 0.04). Stearic acid content started to grow at 15-day AP and reached its peak at 15-day PP (P < 0.01). At 30-day PP, stearic level in liver dropped abruptly (P < 0.01), then intensified at 45-day PP and did not change after; hepatic content of stearic acid was lower during AP compared with PP time-points. Other C18 FAs changed significantly during the study period. These results suggest that parturition could have a profound effect on FA composition and other metabolites in camel liver. Further research is required to establish the metabolic mechanism behind these changes.

Effect of Different Sources of Supplemental Zinc on Performance, Nutrient Digestibility, and Antioxidant Enzyme Activities in Lambs.

Zinc (Zn) is an essential element in the growth of all animals and plays structural and catalytic roles in many enzymes and functional proteins. Two completely randomized trials were conducted to evaluate the effects of different sources of zinc on performance, nutrient digestibility, blood mineral profile, and antioxidant enzyme activities in male growing lambs on a barley-based diet. The first trial was conducted for 70 days and consisted of 30 lambs (30.8 ± 2.8 kg mean body weight, 4-5 months of age) which were randomly allocated to five treatments consisting of a basal diet (19.72 mg Zn/kg DM), or the basal diet supplemented with 30 mg Zn/kg DM, added as either zinc-sulfate (ZnSulf; inorganic), zinc-methionine (ZnMet), zinc-proteinate (ZnProt) or zinc-glycinate (ZnGly). For the second trial, to measure the effects of dietary Zn on nutrient digestibility, four lambs from each group of the first experiment were randomly allocated to individual digestibility cages for 12 days (first 7 days as an adaptation period followed by 5 days of sample collection). Among the groups, dietary Zn supplementation above basal level significantly improved average daily gain, average daily feed intake, feed/gain ratio, and superoxide dismutase activity of red blood cells (P < 0.05). Glutathione peroxidase activity of lambs supplemented with organic Zn was significantly (P < 0.05) higher than inorganic and control groups. At the end of the trial, the concentration of plasma Zn, tri-iodothyronine (T3), thyroxine (T4), and the activity of alkaline phosphatase was increased (P < 0.05) in all groups receiving Zn as compared with controls (P < 0.05). In addition, thyroxine level in animals supplemented with Zn-methionine and Zn-proteinate was greater than in animals receiving Zn-glycine and Zn-sulfate. The results of the second trial revealed that the supplementation with Zn-methionine and Zn-proteinate increased the digestibility of crude protein (CP) and acid detergent fiber (ADF) compared to groups supplemented with Zn sulfate and control (P < 0.05). All organic sources of Zn improved organic matter (OM) digestibility compared to inorganic and control (P < 0.05). Results indicated that, regardless of source, supplementation of Zn in growing lambs improved growth performance, blood antioxidants, and thyroid hormone levels. Furthermore, Zn-methionine and Zn-proteinate supplementation appeared to improve the digestibility of CP, OM, and ADF more effectively than Zn-sulfate.

Urine volume and nitrogen excretion are altered by feeding birdsfoot trefoil compared with alfalfa in lactating dairy cows1.

Legumes that contain condensed tannins may have lower ruminal protein degradation than alfalfa. The present study investigated the effects of feeding birdsfoot trefoil (Lotus corniculatus L.) hay on lactational performance and N utilization and excretion. Eight multiparous Holstein cows in midlactation (150 ± 22.3 d-in-milk) were randomly assigned to 2 treatments [alfalfa hay-based total mixed ration (AHT) or birdsfoot trefoil hay-based total mixed ration (BHT)] in a crossover design with 2 experimental periods. Each experimental period lasted 17 d (14 d of adaptation and 3 d of sampling and total collection). Hays comprised approximately 50% of DM in experimental diets. There were no treatment effects on dry matter intake (DMI; 21.4 vs. 20.7 kg/d), milk yield (29.4 vs. 28.1 kg/d), milk fat concentration (3.20% vs. 3.21%), and milk protein concentration (3.20% vs. 3.16%) for AHT and BHT, respectively. In addition, dietary treatments did not affect milk yield/DMI or energy-corrected milk yield/DMI. In contrast, apparent crude protein digestion decreased in cows fed BHT compared with those fed AHT (60.7% vs. 69.1%). Concentration of milk urea-N decreased by feeding BHT compared with AHT (11.9 vs. 13.3 mg/100 mL), whereas total N excretion did not differ between AHT and BHT diets. However, cows fed BHT excreted more N in feces (194 vs. 168 g/d), whereas urinary N excretion was lower compared with cows fed AHT. The shift of N to feces resulted in a decrease in urinary N:fecal N ratio in cows fed BHT relative to those fed AHT. Overall results in the current study suggest that feeding birdsfoot trefoil in dairy diets shifts routes of N from urine to feces compared with feeding alfalfa hay, with little effect on lactational performance. Reduction in urinary N and any impact on environment may be attributed to functional effect of condensed tannins in birdsfoot trefoil hay.