Effects of intraruminal infusion of propionate on the concentrations of ammonia and insulin in peripheral blood of cows receiving an intraruminal infusion of urea

Effects of a blend of live yeast and organic minerals or monensin on performance of dairy cows during the hot season

The objective of this study was to evaluate the effects of feed additives on intake and digestibility of nutrients, milk yield and composition, feeding behavior, and physiological parameters of dairy cows during the hot season. Forty Holstein cows were assigned to a randomized block design experiment with a 2 × 2 factorial treatment arrangement to evaluate (1) control diet without inclusion of additives; (2) monensin (MON), 20 mg/kg diet dry matter sodium monensin (Rumensin; Elanco); (3) Milk Sacc+ (MS+), inclusion of 40 g/cow per d of Milk Sacc+ (a blend of live yeast and organic minerals, Alltech); and (4) combination of MON and MS+. The average temperature-humidity index throughout the experimental period was 73 ± 2.84 (standard deviation). The experiment lasted 11 wk, including 2 preliminary weeks for covariate adjustments. Cows fed MS+ increased dry matter intake (% body weight), milk yield, 3.5% fat-corrected milk, and solids yield, and cows fed MON had greater milk urea nitrogen content in comparison with counterparts. Feeding MS+ increased the intake of feed particles with size between 8 and 19 mm and decreased the intake of particles shorter than 4 mm compared with other treatments. Rumination time (min/d) and chewing time (min/kg of neutral detergent fiber) were lower for cows fed MS+. Physiologic parameters (i.e., heart and respiratory rates, and body temperature) were not affected by the treatments. Overall, the use of monensin did not differ from control, and Milk Sacc+ improved performance of cows.

The rate and pattern of urea infusion into the rumen of wethers alters nitrogen balance and plasma ammonia

Changes in N balance, urinary excretion of purine derivative (PD), urea, creatinine and ammonia and plasma ammonia, glucose, urea, insulin and IGF-1 were examined in four wethers (37 ± 2.6 kg BW). The animals were fitted with permanent ruminal catheters, fed lucerne hay (9.4 MJ/day; 23 g N/day; 7 g soluble N/day, 6 equal meals/day) and treated with contrasting rates of urea infusion into the rumen: first, a continuous infusion (CT), at 3.2 mg urea-N/min for 10 days and then a discontinuous infusion (DT) at 156 mg urea-N/min for 4 min; in 6 daily doses with the meals for 7 days. N balance was calculated from pooled samples of faeces and urine. Jugular blood samples were collected before and 1.5 h after the morning meal (M1) on days CT10, DT2, DT4 and DT6. N retention decreased during DT (p = 0.01) due to a significant increase of N excretion in urine (4 g/day; p = 0.009) and faeces (1 g/day; p = 0.02). Dry matter (p < 0.001) and N digestibility in vivo (p = 0.01) decreased significantly during DT. Urinary urea and PD excretion were not altered by treatment. Significant linear (p = 0.004) and quadratic (p = 0.001) effects were observed for plasma ammonia in M1 (from 170 CT10 to 235 μm DT2 and returned to 120 μm DT6). No changes were observed in plasma glucose, urea, insulin and IGF-1. Results indicate that changes from CT to DT reduced N retention in sheep due to enhanced urinary N excretion, but it was not associated with changes in urinary urea or PD excretion; or plasma concentrations of insulin and IGF-1. As the dry matter (DM) an N digestibility could account a 0.23 of the decrease in N retention; the largest fraction of the reduction in N retention remained unexplained by the results.

The prediction of rumen fermentation characteristics in sheep given grass silage diets

Eight change-over design experiments (each a duplicated 3 × 3 Latin square design using six rumen-fistulated wether sheep, live weight 50 to 60 kg) measured rumen fermentation patterns for 24 perennial ryegrass silages. Sheep were offered 800 g dry matter (DM) per day of each silage in two equal meals at 09.00 and 17.00 h. Samples of rumen liquor were taken on days 19 and 21 of each 21-day period, at 08.50 h and at 1·5-h intervals until 16.30 h. Rumen samples were analysed by gas chromatography; silages by high-performance liquid chromatography and by near infra-red reflectance spectroscopy (NIRS) using samples scanned after drying at 100°C (NIRSdry) or in the fresh state (NIRSwet).

Mean intake of DM was 737 g/day. The range of silage composition was as follows (mean, range, s.d., g/kg DM unless specified): metabolizable energy (ME MJ/kg DM) 11·1, 8·8 to 12·6, 0·81; pH 4·0, 3·6 to 5·0, 0·34; lactic acid 86, 4 to 139, 42·6; butyric acid 4·7, 0·1 to 46·7,10·2. Rumen measurements varied substantially both diurnally and between silages. Mean diurnal rumen values for the 24 silages (mean, range, s.d.) were: pH 6·76, 6·55 to 7·09, 0·155; ammonia (mg/l) 132, 70 to 247, 47·7; total volatile fatty acids (TVFA mmol/l) 58·2, 45·8 to 72·0, 8·97; (acetate+butyrate)/propionate (ABP) 3·2, 2·2 to 4·8, 0·56.

Partial least-square models were developed to predict rumen fermentation (means for six sampling times) using either the silage chemical composition (CHEM g/kg DM unless specified: DM, ME (MJ/kg DM), crude protein (CP), ammonia (NH3, g N per kg total N), neutralizingvalue (meq per kg DM), sugar, lactic, formic, acetic, propionic and butyric acids and ethanol) or silage NIRSdry or NIRSwet. Prediction performance was assessed comparing values for R2, standard error of cross validation (SECV) and SD/SECV (s.d. of reference population! SECV) obtained by the ‘leave one out’ cross validation method. NIRSwet gave slightly better prediction accuracy overall than NIRSdry but both were superior to prediction from chemical composition. Values for R2, SECV and SD/SECV for pH were 0·23, 0·14, 1·09; 0·76, 0·08, 2·01 and 0·72, 0·08, 1·89 for CHEM, NIRSdry and NIRSwet respectively. Corresponding values for rumen ammonia (mg/l) were 0·48, 35·2, 1·35; 0·69, 27·1, 1·76 and 0·70, 26·3, 1·81; for TVFA 0·52, 6·73, 1·33; 0·80, 4·06, 2·21 and 0·93, 2·47, 3·63; for rumen ABP ratio 0·69, 0·32, 1·78; 0·76, 0·30,1·88; 0·72, 0·30,1·85. The silage predictors with greatest influence in the CHEM model for rumen ABP ratio were sugar, CP and lactic acid (negative) and butyrate and ethanol (positive). NIRS shows considerable promise as a means of predicting rumen fermentation of animals given grass silage diets.

Intraruminal infusion of n-butyric acid induces an increase of ruminal papillae size independent of IGF-1 system in castrated bulls

The objective of this study was to explore morphological alterations of rumen papillae induced by n-butyric acid in relation to the insulin-like growth factor (IGF) system in adult castrated bulls. Three animals fitted with rumen cannula were fed twice daily at a low and high nutritional level (LL and HL), i.e., at 1.1 x maintenance (M) and 1.6 x M, respectively. Diets contained artificial dried grass and concentrate (74:26 and 52:48). Bulls received no (B0) or daily intraruminal infusions of 500 g n-butyric acid (B500) over 14 d. The infusion started 1 h after the morning feeding (9:00) and lasted for 3.5 h. Thus, four treatments (BOLL, B500LL, BOHL, and B500HL) were compared. Blood and rumen mucosa samples from the atrium ruminis were taken at the last day of each period. Length, width and surface of rumen papillae were greater (p < 0.001) in BOHL than in BOLL. Treatment with n-butyric acid resulted in an increase of the papillae surface of 20-40% (p = 0.047) for both nutritional levels as compared to periods without n-butyric acid treatments. The higher nutritional level and intraruminal n-butyric acid infusion induced epithelial cell death. The percentage of proliferative cells was doubled by n-butyric acid treatment. The mRNA of IGF-1 and IGF type 1 receptor (IGF-1R), as well as IGF-1R binding capacity were unaffected by butyric acid treatments. The abundance of IGF-1 mRNA tended to be lower (p = 0.1) and IGF-1R abundance was lower (p = 0.03) in response to the HL. The plasma IGF-1 concentration was lower with butyric acid treatment (p < 0.01), but was unaffected by the nutritional level. In conclusion, under described experimental preconditions of daily short-time intraruminal n-butyric acid infusion alterations of rumen papillae morphology is not mediated by ruminal IGF type 1 receptor and by local IGF-1 expression in papillae in castrated bulls.

Synchrony of nutrient supply to the rumen and dietary energy source and their effects on the growth and metabolism of lambs

The objective of the current series of experiments was to assess the effects of dietary synchrony of OM and N supply to the rumen, achieved by altering the sequence of feeding individual ingredients and in diets with different energy sources, on the metabolism and performance of growing lambs. In Exp. 1, the in situ degradability coefficients of OM and N were determined for five feed ingredients and subsequently was used to formulate two diets, based either on barley or sugar beet pulp, to have a similar predicted nutrient content. Within each diet, specific ingredients were shifted between the 0900 and 1600 feeding to provide either a synchronous, intermediate, or asynchronous supply of OM and N to the rumen. In Exp. 2, these diets were fed at a restricted level to 48 growing lambs with an initial live weight of 25.1 +/- 4.22 kg and a slaughter weight of 41.4 +/- 1.94 kg. There was no significant effect of dietary treatment on live weight gain or feed conversion efficiency. Lambs fed the synchronous diets deposited more kidney knob and channel fat than lambs on the asynchronous or intermediate diets (P < 0.05), whereas lambs fed the barley-based diets deposited more carcass (P < 0.05) and noncarcass (P < 0.001) fat than lambs on the sugar beet-based diets. Lambs fed the asynchronous diets retained less energy over the course of the experiment than lambs on the intermediate or synchronous diets (P < 0.05), and had a lower energy efficiency (0.079, 0.097, and 0.093 MJ retained/ MJ of intake, respectively, P < 0.05). Lambs fed the barley-based diets retained more energy than lambs on the sugar beet-based (P < 0.001) and had a higher energy balance (0.095 vs. 0.084 MJ retained/MJ intake, respectively; P < 0.01). Plasma ammonia concentrations mirrored ruminal ammonia concentrations on the barley-based diets, but not sugar beet-based diets. In Exp. 3, lambs fed the sugar beet-based diets had a higher digestibility of OM and NDF (P < 0.001). By contrast, lambs on the barley-based diets had a higher level of purine derivative excretion and microbial N production (P < 0.001). The results indicate that neither dietary synchrony nor energy source significantly influenced growth rate. However, both the asynchronous and sugar beet pulp-based diets resulted in a lower efficiency of dietary energy use, and the avoidance of asynchronous patterns of nutrient release within the rumen can improve energy efficiency in growing lambs.

Hypophagic effects of ammonium are greater when infused with propionate compared with acetate in lactating dairy cows

The objective of this experiment was to determine interactions between hypophagic effects of propionate and ammonium in lactating dairy cows. Eight ruminally cannulated Holstein cows in mid-lactation were used in a duplicated 4 x 4 Latin square design experiment with a 2 x 2 factorial arrangement of treatments. Factors evaluated were type of volatile fatty acid (VFA; acetate vs. propionate) and type of salt (sodium vs. ammonium). Treatment solutions were infused continuously into the rumen at a rate of 16.7 mmol of VFA salts/min starting 2 h before feeding and ending 12 h after feeding. Hypophagic effects of ammonium were significantly greater for cows infused with propionate (4.3 vs. 12.1 kg/12 h; SEM = 1.3) compared with acetate (13.5 vs. 15.3 kg/12 h; SEM = 1.3; interaction P < 0.01). This interaction was attributed to a greater reduction in meal frequency for ammonium treatment compared with sodium treatment when infused with propionate (3.9 vs. 7.2/12 h; SEM = 0.8) compared with acetate (6.6 vs. 7.0/12 h; SEM = 0.8), indicating that infusion of ammonium propionate reduced hunger. Meal size was decreased by infusion of propionate compared with acetate, but was not affected by ammonium compared with sodium, indicating that ammonium did not affect satiety. Mechanisms to explain the interactions between ammonium and propionate on meal frequency and feed intake warrant further investigation.

Animal and dietary factors affecting feed intake during the prefresh transition period in Holsteins

Parity, body condition score (BCS), and dry matter intake (DMI) data of 699 Holsteins fed 49 different diets during the final 3 wk of gestation (prefresh transition period) were compiled from 16 experiments conducted at eight universities. The objectives of this study were to determine the effects of animal and dietary factors on DMI and to elucidate interactions between animal and dietary factors and among dietary factors on DMI during the prefresh transition period. Animal factors examined were parity and BCS, whereas dietary factors examined were rumen undegradable protein (RUP), rumen degradable protein (RDP), neutral detergent fiber (NDF), and ether extract (EE). DMI decreased 32% during the final 3 wk of gestation, and 89% of that decline occurred during the final week of gestation. Day of gestation, animal factors, and dietary factors accounted for 56.1, 19.7, and 24.2% of explained variation in DMI, respectively, and R2 of this linear multivariable model was 0.18. Cows had higher DMI than heifers. DMI decreased linearly as BCS, RUP, and NDF increased, decreased quadratically as EE increased, and increased quadratically as RDP increased. Moreover, the magnitude of DMI depression as animals approached parturition was affected by characteristics of animals and dietary nutrient composition. There were significant parity x EE, BCS x NDF, RUP x NDF, RDP x NDF, NDF x EE, and RUP x EE interactions on DMI. In conclusion, parity, BCS, and concentrations of organic macronutrients in diets affected DMI during the prefresh transition period, and the magnitude of DMI depression as animals approached parturition.