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The objective of this study was to evaluate the effects of glycerol supplementation on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in the total tract of steers. Eight ruminally cannulated Simmental steers (450±12 kg) were used in a replicated 4×4 Latin Square arrangement of treatments with experimental period of 21 days long. The treatments were: control (without glycerol), LG, MG and HG with 100, 200 and 300 g glycerol per head per day, respectively. Diet consisted of 60% corn stover and 40% concentrate (dry matter [DM] basis). Dry matter intake (averaged 9 kg/day) was restricted to a maximum of 90% of ad libitum intake. Ruminal pH (range of 6.58 to 6.23) was linearly (P<0.05) decreased, whereas total VFA concentration (range of 93.40 to 99.61 mM) was linearly (P<0.03) increased with increasing glycerol supplementation. Ratio of acetate to propionate decreased linearly (P<0.02) from 4.56 to 3.64 as glycerol supplementation increased due to the increased in propionate production. In situ ruminal NDF degradation of corn stover was improved but the CP degradability of concentrate mix was decreased with increasing doses of glycerol. Urinary excretion of purine derivatives was quadratically (P<0.02) changed with altering glycerol supplementation (65.0, 65.7, 71.1 and 67.2 mmol/d for control, LG, MG and HG, respectively). Similarly, digestibilities of OM, NDF and CP in the total tract were also linearly increased with increasing glycerol. The results indicate that glycerol supplementation potentially improves rumen fermentation with increased propionate production and feed digestibility in the total digestive tract of beef cattle. It suggests that feeding glycerol stimulates the ruminal microorganisms or digestive enzymes in a dose-dependent manner. Under the current experimental conditions, the optimum glycerol dose was about 200 g glycerol per head per day.

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The objective of this study was to evaluate the effects of malic acid (MA) on feed intake, milk yield and composition, blood metabolites and energy balance in early lactation Holstein dairy cows from 1 to 63 day in milk (DIM). Twenty-eight multiparous Holstein dairy cows, blocked by lactation number, previous 305-d mature equivalent milk production, and expected calving date, were arranged into four groups in a randomized block design. Treatments were: control (without MA), LMA, MMA and HMA with 70, 140 and 210 g malic acid per cow per day, respectively. The supplement of food grade MA (99.8% of MA) was hand-mixed into the top one-third of the daily ration. Cows were fed ad libitum a total mixed ration consisting of equal proportion of forage and concentrate. Milk yield increased (P=0.04), but feed intake and milk components were not affected (P>0.05) by MA supplementation. The energy balance, expressed as the difference between energy input and output, tended to be higher (P=0.08) for MA supplemented cows during the 63-DIM period MA and supplemented cows showed a trend (P=0.07) toward less loss of BW during the 63-day period, especially during the first 21-day of lactation. Concentrations of plasma glucose and serum insulin were higher for cows fed LMA, MMA, and HMA relative to control and linearly (P<0.01) increased with increasing MA supplementation. Concentrations of non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA) and urine ketones were lower for MA-supplemented cows at 7, 14 and 21 DIM of lactation and linearly (P<0.01) decreased with increasing MA supplementation. Although feed intake was not affected, milk yield increased, MA-supplemented cows experienced higher concentrations of plasma glucose and serum insulin, lower concentrations of plasma BHBA and NEFA, and lower concentrations of urine ketones, suggesting that nutrient digestibilities and energy availability may have been improved.

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The objective was to evaluate the effects of selenium-yeast (SY) supplementation on rumen fermentation, lactation performance and feed digestibilities in dairy cows. Twenty-eight multiparous (2.5±0.3 parity) Holstein dairy cows, averaging 625±18.2kg of BW, 63±3.0days in milk and average daily milk production of 26.2±0.5kg/cow were used in a replicated 4×4 Latin square experiment. Treatments were: control, LSY, MSY and HSY with 0, 150, 300 and 450mg selenium yeast (Sel-Plex®, 1g/kg selenium, produced from Saccharomyces cerevisiae CNCM I-3060) per kg of diet dry matter (DM), respectively. Experimental periods were 45days with 30days of adaptation and 15days of sampling. Ruminal pH was lower for MSY than for control and was linearly (P=0.03) decreased, whereas total VFA concentration was linearly and quadratically (P≤0.01) increased with increasing SY supplementation, with the least for control, followed by LSY and HSY, and the highest for MSY. Ratio of acetate to propionate was lower for LSY, MSY and HSY than for control, and was linearly and quadratically (P≤0.01) decreased as SY supplementation increased due to an increase in molar proportion of propionate. Ruminal ammonia N content was lower (P≤0.01) for MSY and HSY than for control and was linearly decreased (P≤0.01) with increasing SY supplementation. Dry matter intake, proportions and yields of milk fat, protein and lactose were not affected (P>0.05). Milk yields and 4% FCM were higher (P≤0.05) for LSY and MSY than for HSY and control. Milk selenium content was linearly and quadratically (P≤0.01) increased as increasing SY supplementation, with the least for control, followed by LSY and MSY, and the highest for HSY. Digestibilities of DM, organic matter (OM), crude protein (CP), ether extract (EE), aNDF and ADF in the total tract were higher (P<0.01) for LSY and MSY than for control and HSY. The results indicate that supplementation of diet with SY improved rumen fermentation, milk yields, milk selenium, and feed digestion. It was suggested that the SY stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum selenium-yeast dose was about 300mg per kg diet DM.

▼ The objective was to evaluate effects of feeding salt-tolerant forages cultivated in salt-alkaline land on intake, average liveweight gain, physiological responses and slaughtering performance in lamb. Sixty first generation (F1) lambs of a cross between Chinese Inner Mongolian Fine-wool and German Mutton Merino (3.0+/-0.12months; 23.5+/-0.83kg of body weight [BW]), were arranged into four treatments. Treatments were: control (51% corn stover and 49% concentrate, dry matter [DM] basis), LSTF, MSTF and HSTF in which the mixture of salt-tolerant forages (Dahuria wildrye grass, Weeping Alkaligrass and Erect Milkvetch by a ratio of 45:35:20) replaced either one-third, two-thirds or all of the corn stover, respectively. Lambs were fed twice daily at 0700 and 1900h with water provided ad libitum during the 60-day growth trial. Average liveweight gain, pulse rate, respiratory rate, rectal temperature, liveweight at slaughter and bone weight were not different between treatments. With increasing the inclusion of salt-tolerant forages in the diet, DM, NDF and ADF intake linearly (P=0.001) increased to be higher (P<0.01) for LSTF, MSTF and HSTF diets than for control, but CP intake was unchanged. Feed conversion rate linearly (P=0.001) increased with the least for control, followed by LSTF, the highest for MSTF and HSTF diets. Carcass weight and meat weight linearly (P<0.03) increased to be higher (P<0.02) for LSTF, MSTF and HSTF diets than for control. Dressing percentage, meat percentage and the ratio of meat to bone linearly increased for being higher (P<0.05) with LSTF, MSTF and HSTF diets than with control. Average longissimus muscle area quadratically (P=0.005) increased with the least for control, followed by HSTF, the highest for LSTF and HSTF diets. Results indicate that feeding salt-tolerant forages to lambs as partial or sole forage source can be beneficial for increasing feed intake and increase meat production.

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The objective of this study was to evaluate the effects of LaCl₃ supplementation on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in the total tract of steers. Eight ruminally cannulated Simmental steers (420±20kg) were used in a replicated 4×4 Latin square experiment. The treatments were control (without LaCl₃); La-low; La-medium and La-high with 450, 900 and 1800mg LaCl₃ per steer per day, respectively. Diet consisted of 600g/kg corn stover and 400g/kg concentrate (dry matter [DM] basis). Dry matter intake (averaged 9kg/day) was restricted to a maximum of 90% of ad libitum intake. Ruminal pH (range of 6.59–6.42) was quadratically (P<0.04) changed, whereas total volatile fatty acids (VFA) concentration (range of 74.16–88.61mM) was linearly (P<0.01) and quadratically (P<0.01) increased with increasing La supplementation. Ratio of acetate to propionate decreased linearly (P<0.01) from 3.28 to 1.79 as La supplementation increased due to the increased in propionate production. In situ ruminal neutral detergent fibre (aNDF) degradation of corn stover was improved but the crude protein (CP) degradability of soybean meal was decreased with increasing La supplementation. Urinary excretion of purine derivatives was quadratically (P<0.01) changed with altering La supplementation (75.5, 81.0, 82.4 and 70.6mmol/day for control, low-, medium- and high-LaCl₃ supplementation, respectively). Similarly, digestibilities of organic matter, aNDF and CP in the total tract were also linearly and quadratically increased with increasing La supplementation. The present results indicate that supplementation of diet with LaCl₃ improved rumen fermentation and feed digestion in beef cattle. It was suggested that the La stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum La dose was about 900mg LaCl₃ per steer per day.

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The objective was to evaluate effects of glycerol supplementation on feed intake, milk yield and milk composition, blood metabolites and energy balance in Holstein dairy cows from 4 to 63 days in milk (DIM). Thirty-six multiparous cows, blocked by lactation number, previous 305 day mature equivalent milk production and expected calving date, were arranged into four groups in a randomized block design. Treatments were: control (without glycerol), glycerol-low (LG), glycerol-medium (MG) and glycerol-high (HG) with 100, 200 and 300g glycerol per cow per day, respectively. The supplement of food grade glycerol (0.998g/g glycerol) was hand-mixed into the top one-third of the daily ratio. Cows were fed ad libitum a total mixed ratio consisting of equal proportions of forage and concentrate. Feed intake, milk yield and its components were not affected by glycerol supplementation. The energy balance, expressed as differences between energy input NE_I and output (NE_M+NE_L) in MJ per cow per day, was higher (P<0.04) as glycerol supplementation level increased, especially during the first 17 and last 20 days of the 63 day period. Glycerol-supplemented cows tended (P<0.06) toward less loss of BW, especially first 17 and last 20 days of the 63 day period. Concentrations of glucose in plasma were higher for cows fed glycerol relative to control (54.1mg/dL versus 58.1mg/dL, respectively) and linearly increased (P<0.01) with increasing glycerol supplementation level. Concentrations of non-esterified fatty acids, beta-hydroxybutyrate and urine ketones were lower for glycerol-supplemented cows at 7, 14 and 21 days of lactation and linearly (P<0.01) decreased with increasing glycerol supplementation. Although milk yield and feed intake were not affected, glycerol-supplemented cows has a more positive energy status (higher concentrations of plasma glucose, lower concentrations of plasma beta-hydroxybutyrate, lower concentrations of urine ketones), suggesting that net energy availability may have been increased.

▼ The objective of this study was to evaluate effects of isobutyrate supplementation on rumen fermentation, lactation performance and plasma characteristics of dairy cows. Twenty multiparous second filial generation (F2) cows of a cross between Chinese Jinnan Yellow and Holstein cows at 148+/-4.5 days in milk and 22.3+/-0.81kg milk production were used in a replicated 4x4 Latin square experiment. The treatments were: control (without isobutyrate), low (LIB), medium (MIB) and high (HIB) isobutyrate supplementation of 20, 40 and 60g per cow per day, respectively. Experimental periods were 30 days with 15d of adaptation and 15d of data collection. Dry matter (DM) intake was not affected by increasing isobutyrate supplementation, but milk yields were highest for the 40g/d isobutyrate supplementation level, where proportion of milk fat, true protein and lactose were minimized. Ruminal pH (6.38-6.24) and ammonia N (13.8-11.1mg/100ml) were linearly (P<0.01) decreased, whereas total VFA concentration (124-131mM) increased at a decreasing rate with increasing isobutyrate supplementation. The ratio of acetate to propionate increased linearly (P<0.01) from 2.77 to 4.43 as isobutyrate supplementation increased due to the increase in acetate production and decrease in propionate production. Digestibilities of OM in the total tract increased linearly (P<0.01) as isobutyrate supplementation increased, digestibilities of DM and EE were highest for the 40g/d isobutyrate supplementation level, digestibilities of CP, aNDF and ADF increased at a decreasing rate with increasing isobutyrate supplementation. Plasma concentrations of glucose and growth hormone linearly (P<0.03) increased, whereas concentrations of non-esterified fatty acids linearly (P<0.01) decreased. Results indicate that supplementation of this diet with isobutyrate changed the rumen fermentation pattern towards acetate production, improved digestion and modified plasma concentrations of glucose and growth hormone. This suggests that isobutyrate stimulated digestive microorganisms or enzymes in a dose-dependent manner with the optimum isobutyrate dose at about 40g per cow per day in terms of improved digestion.