Influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide on ruminant nitrogen metabolism: I. In vitro urea kinetics and substrate digestion

Two in vitro digestion experiments were conducted to evaluate the influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on in vitro urea kinetics, substrate digestion, and fermentation characteristics. In Exp. 1, in vitro incubations were conducted in 50-mL test tubes containing .25 g of ground fescue hay to which 0, 6.5, 13, 26, or 52 mg of NBPT in a buffered ruminal fluid innoculum was added. Tubes were incubated in triplicate at 39 degrees C and replicated on consecutive days, with NH3 N and urea concentrations measured at 0, 10, 30, 60, 120, 240, and 360 min. Samples for VFA analysis were collected at 6 h, and incubations were continued through 48 h to estimate true digestibility (based on NDF analysis). Increasing the dose of NBPT tended (P < .12) to linearly depress the rate of urea hydrolysis and decreased (P < .0004) subsequent NH3 N formation. Although total VFA concentration at 6 h increased linearly (P < .03), acetate:propionate and estimated true digestibility decreased (P < .01) with increasing NBPT concentration. In Exp. 2, we compared in vitro urea kinetics and digestion of forage-only or mixed forage-grain substrates in response to addition of NBPT. In vitro incubations were conducted in 50-mL test tubes containing either .5 g of ground fescue hay or .5 g of a ground fescue hay and ground corn mixture (50:50, DM basis) to which 0, 6.5, 13, 26, or 52 mg of NBPT in a buffered ruminal fluid innoculum was added. Tubes were incubated in triplicate at 39 degrees C and replicated on consecutive days, with NH3 N and urea concentrations measured at 0, .5, 1, 2, 4, 8, 12, 24, and 48 h. At 48 h, samples for VFA analysis were collected and true digestibility (based on NDF analysis) was estimated. No (P > .10) NBPT dose x substrate interactions were detected. Increasing the dose of NBPT depressed (P < .003) the rate of urea hydrolysis and subsequent NH3 N formation, regardless of substrate. Although total VFA concentration was unaffected (P > .10), the acetate:propionate and estimated true digestibility decreased (P < .002) with higher NBPT addition. In both experiments, the rate of urea degradation was not different (P > .20) from zero for the 26 and 52 mg NBPT treatments, indicating that nearly complete inhibition of urease had been achieved. We conclude that NBPT can be used to reduce the rate of NH3 N release from dietary urea and, thereby, offers the potential to improve nonprotein nitrogen utilization in ruminants.     

脲酶抑制剂氢醌对绵羊营养物质消化率和氮代谢的影响

以饼类饲料饲喂反刍动物时，饲料的真蛋白质平均只有３０％通过瘤胃，而其余７０％则在瘤胃内被微生物降解，所产生的氨只有８０％被转化成微生物蛋白质，其余的２０％则在肝脏内合成内源尿素，参加尿素再循环的代谢途径。Satter等（１９７５）认为，饲料蛋白质在瘤胃内大量降解时增加了内源尿素周转环节，造成浪费。当日粮内含有尿素时，由于尿素分解太快，氨的释放速度超过了微生物对其利用的速度，使微生物对尿素的利用量减少。因此，在日粮中使用脲酶抑制剂是减缓瘤胃内尿素的分解速度，增加小肠菌体蛋白质的供应量，节约优质蛋白质的…     

Effect of diet composition and feed intake level on diet digestibility and ruminal metabolism in growing lambs.

Lambs (29 +/- 2.5 kg) were fed three diets at various intakes to determine whether diet composition or level of intake was reflected in changes in diet digestibility or ruminal fluid characteristics. In Exp. 1, a 90% concentrated, pelleted diet or a whole shelled corn diet with a pelleted protein supplement was fed at three levels of intake: ad libitum and 92.5 and 85% of ad libitum (n = 15). Exp. 2 compared the 90% concentrate diet with diets in which the energy density was diluted to 55 or 72.5% concentrate by including alfalfa hay as a possible method of restricting energy intake (n = 6). Lambs were adapted to diets for 13 d; feces were collected for 6 d and ruminal fluid was collected 0, 3, and 6 h after feeding on the day following fecal collection. Restricting intake in Exp. 1 did not affect DM digestibility or digestibility of CP or starch. Digestibility of ADF was increased (P less than .10) by restricting intake. Ruminal fluid pH, ammonia concentration and VFA concentrations were affected little by either restricted intake level. Digestibility of DM was 4% higher (P less than .001) and starch 5% higher (P less than .001) for the whole shelled corn diet than for the pelleted, high-concentrate diet. Ruminal pH of lambs fed the whole shelled corn diet was higher and fluctuated less than the ruminal pH of lambs fed the high-concentrate, pelleted diet. In Exp. 2, diet digestibility was reduced (P less than .01) and ruminal pH was increased (P less than .002) by addition of hay. Restricted feeding of lambs did not seem to increase diet digestibility or alter ruminal conditions.     

Effects of corn processing and dietary fiber source on feedlot performance, visceral organ weight, diet digestibility, and nitrogen metabolism in lambs

In Exp. 1, early-weaned Targhee and Polypay crossbred lambs (60 ewes and 66 rams; initial BW 24 +/- 1.0 kg) were used in a 2 x 3 factorial experiment to determine the effects of corn processing (whole shelled corn [WSC] or ground and pelleted corn [GC]) in combination with supplemental fiber (none [control]; soybean hulls, SBH [highly digestible]; or peanut hulls, PH [highly indigestible]) on DMI, ADG, feed efficiency, and visceral organ weight. For the total trial, WSC resulted in a 4% increase (P < .01) in ADG vs GC, and supplemental fiber resulted in increased (P < .01) DMI and ADG vs the control diet. Experiment 2 was conducted using 12 Targhee and Polypay crossbred wether lambs (initial BW 25 +/- 7 kg) to determine the effects of corn processing and fiber source in high-concentrate diets on diet digestibility and N retention using the same diets as in Exp. 1. Lambs fed WSC had greater (P < .001) apparent N digestion, true N digestion, and N retention (P < .01) than those fed GC. The apparent digestibilities of DM, OM, and NDF were greater (P < .001) for WSC than for GC diets. Peanut hulls resulted in decreased (P < .01) DM, OM, and NDF apparent digestibilities compared with the control and SBH diets. Starch digestion was not affected (P > .10) by diet. Whole corn resulted in improved DM, OM, NDF, and N digestibility compared with GC. Overall, both the SBH and PH diets resulted in greater DMI and ADG than the control diet, which lacked supplemental fiber.     

Influence of protein degradability in range supplements on abomasal nitrogen flow, nitrogen balance and nutrient digestibility

Two metabolism trials were conducted with yearling steers fed mature native forage to measure the effect of supplemental protein degradability on selected metabolic variables. Supplements contained 40% crude protein equivalence. In Trial 1, four abomasal-cannulated steers weighing 290 to 379 kg were fed supplements containing the following N sources: (1) 15% corn, 85% urea (U); (2) 100% soybean meal (SBM); (3) 10% corn, 40% soybean meal, 50% urea (SBM-U) and (4) 14% corn, 36% blood meal, 50% urea (BM-U). Equal portions of the daily diet (2.2% of body weight) were fed every 2 h. Treatment differences were not significant for organic matter digestibility, abomasal organic matter flow, nonammonia N flow, feed N flow, bacterial N flow and efficiency of microbial protein synthesis. There was a positive (P less than .05) relationship between quantity of slowly degraded protein fed and nonammonia N flow (r = .97) or feed N flow (r = .98). Escape N was determined to be 21.5, 16.5 and 54.2% in SBM, SBM-U and BM-U supplements, respectively. In the second trial, no supplement, SBM, SBM-U and BM-U were fed in a N balance trial. Dry matter, crude protein and neutral detergent fiber digestibilities were higher (P less than .05) for steers fed supplemented diets. Acid detergent fiber digestibility was higher (P less than .05) for steers supplemented with SBM than steers fed the unsupplemented diets. Nitrogen retention was greater (P less than .05) for cattle fed SBM and BM-U than for cattle fed SBM-U or no supplement.(ABSTRACT TRUNCATED AT 250 WORDS)     

Energy source and ionophore supplementation effects on lamb growth, carcass characteristics, visceral organ mass, diet digestibility, and nitrogen metabolism.

In Exp. 1, 72 Targhee lambs (initial BW 22.1+/-.3 kg) were used to determine the effects of energy source (alfalfa pasture vs limit-fed, all-concentrate) and ionophore addition on performance, visceral organ mass, and carcass characteristics. There were no differences (P > . 10) in ADG or gain/ feed due to ionophore supplementation. Lambs that grazed alfalfa had greater (P < .05) liver, omasum, abomasum, small intestine, cecum, and large intestine weights than did lambs fed the concentrate diet. Lambs fed the concentrate diet had greater (P < .01) hot carcass weights, larger (P < .01) loin eye areas, and greater (P < .001) dressing percentages than lambs that grazed alfalfa. In Exp. 2, lambs offered the concentrate diet had greater (P < .001) DM and OM digestibilities than lambs offered alfalfa (89.5 and 91.1 vs 72.4 and 74.2%, respectively). Apparent and true N digestibilities were greater (P < .001) for the concentrate diet than for alfalfa (90.9 and 101.7 vs 77.7 and 91.9%, respectively). Likewise, grams of N retained per day were twice as great (P < .001) with the concentrate diet than with alfalfa (14.9 vs 6.0 g/ d). The greater visceral organ mass and resulting increases in energy and protein requirements in lambs that grazed alfalfa were probably responsible for the lesser hot carcass weight and dressing percentage compared with lambs fed 100% concentrate.     

Influence of dirlotapide, a microsomal triglyceride transfer protein inhibitor, on the digestibility of a dry expanded diet in adult dogs

The objectives of this study were to evaluate the effects of dirlotapide, a microsomal triglyceride transfer protein inhibitor, on apparent nutrient digestibility of an expanded dry dog food, on defecation frequency and fecal consistency. Eighteen beagles were randomized to either placebo ( n  = 6) or dirlotapide ( n  = 12). Testing was divided into a 21-day adaptation phase (days −21 to −1) and a 35-day treatment (digestibility testing) phase (days 0–35). During the treatment phase, dogs were administered oral dirlotapide (0.3 mg/kg) or placebo (0.06 mL/kg) once daily. For digestibility testing, feces were collected over two periods for 7 days each starting on days −9 and 28. All dogs were fed a commercial adult dog food throughout the study. Food intake was adjusted to maintain body weight during adaptation, followed by pair-feeding placebo dogs the amount of food ingested by the dirlotapide dogs during the treatment period. Dogs in both groups had reduced food intake and lost similar amounts of body weight during treatment. Dogs receiving 0.3 mg dirlotapide/kg once daily had a small but significant ( P  = 0.018) decrease (6.16 ± 2.22%, mean ± SD) in crude fat digestibility compared with the placebo-treated food-restricted dogs, but no difference in crude protein, dry matter, or energy digestibility was observed. Fecal consistency and volume and defecation frequency were similar between groups. Dirlotapide effectively reduced appetite and energy intake without affecting nutrient digestibility, except for a minimal decrease in fat digestibility.     

Effect of benzoic acid on growth performance, nutrient digestibility, nitrogen balance, gastrointestinal microflora and parameters of microbial metabolism in piglets

In order to investigate the effects of benzoic acid on growth performance, nutrient digestibility, nitrogen balance and gastrointestinal microflora of piglets, we conducted a performance experiment and a separate balance study. The performance experiment involved four different dietary treatments: (1) basal diet (negative control); (2) basal diet supplemented with benzoic acid at 5 g/kg; (3) basal diet supplemented with benzoic acid at 10 g/kg; (4) basal diet supplemented with potassium diformate at 12 g/kg. Each dietary treatment was assigned to nine replicate groups, each consisting of two piglets. Live weight, daily weight gain, feed intake and feed conversion ratio were monitored as performance parameters over a 35-day period. Supplementation of the diet with benzoic acid resulted in a dose-dependent increase in feed intake and body weight gain and an improved feed conversion ratio. Piglets fed the diet supplemented with benzoic acid at 10 g/kg outperformed the control piglets in mean feed intake, body weight gain and feed conversion ratio by 9%, 15% and 6% respectively. Growth performance of the piglets fed the diet with benzoic acid at 10 g/kg was similar to that of piglets fed the diet supplemented with potassium diformate. In the balance experiment three groups of six piglets each were fed either a control diet or diets supplemented with benzoic acid at 5 or 10 g/kg respectively. Benzoic acid did not significantly affect nutrient digestibility but increased nitrogen retention. Piglets fed the diets supplemented with benzoic acid at 5 or 10 g/kg retained 5% and 6% more nitrogen, respectively, than control piglets. Supplementation of benzoic acid did not influence the pH value or the concentration of ammonia in the gastrointestinal tract but reduced the number of bacteria in the digesta. In the stomach the number of total aerobic, total anaerobic, lactic acid forming and gram-negative bacteria was reduced; in the duodenum the presence of benzoic acid reduced the number of gram-negative bacteria and in the ileum the number of total aerobic bacteria in a dose-dependent manner. Benzoic acid also considerably reduced the concentration of acetic acid in the duodenum. In conclusion, the data of this study suggest that benzoic acid exerts strong antimicrobial effects in the gastrointestinal tract of piglets and therefore enhances growth performance and nitrogen retention.     

Effect of oak (Quercus persica) acorn level on apparent digestibility,ruminal fermentation,nitrogen balance and urinary purine derivatives in pregnant goats

The aim of this experiment was to investigate the effect of dietary oak (Quercus persica) acorn (OA) level on dry matter intake (DMI), apparent nutrient digestibility, nitrogen (N) utilization, ruminal fermentation, protozoa population and urinary purine derivatives (PD) during the last 60 days of goat pregnancy. Twenty‐four multiparous pregnant goats (41.7 ± 2.3 kg BW) were assigned to one of three experimental diets consisted of control diet (C, without OA) and diets containing 20 (OA₂₀) or 40 g/100 g of OA (OA₄₀) on a DM basis in a completely randomized block design. Goats fed OA₄₀ had lower DMI (p < .01), DM (p < .01), OM (p < .01) and NDF (p < .05) digestibility, ruminal NH₃‐N concentration (p < .01), N intake (p < .01) and N retention (p < .01). Crude protein digestibility and ruminal acetate and total volatile fatty acid (VFA) concentration were lower in animals fed OA‐contained diets (p < .01), whereas ruminal propionate concentration was higher in goats fed the C diet (p < .01). Animals fed OA₄₀ had higher faecal N excretion and lower urinary N excretion (p < .01). Urinary PD was lower in goats fed diets containing OA in relation to those fed the C diet (p < .01). Total protozoa population decreased linearly with increasing OA level in the diet (p < .05). These results suggest that feeding OA, especially high level, has negative impacts on DMI, nutrient digestibility, VFA concentration, N retention and urinary PD excretion that may have adverse effects on metabolism and performance of pregnant goats.     

Influence of diet on calcium metabolism, tissue calcification and urinary sludge in rabbits (Oryctolagus cuniculus)

Rabbits absorb more calcium (Ca) from their diet than they require, and excrete surplus via urine, which therefore contains a typical 'sludge'. This makes rabbits susceptible to Ca-containing uroliths. But given the Ca content of diets of free-ranging specimens, and the limited reports of urinary sludge and Ca contents in free-ranging lagomorphs, we can suspect that rabbits are naturally adapted to high urinary Ca loads. We fed four groups of New Zealand hybrid rabbits [n = 28, age at start 5-6 weeks) pelleted diets consisting of lucerne hay only (L, Ca 2.32% dry matter (DM)], lucerne:oats 1:1 (LG, Ca 1.36%), grass hay only (G, Ca 1.04%), or grass:oats 1:1 (GG, 0.83%) for 25 weeks, with water available ad libitum. Diets were not supplemented with Ca, phosphorus, or vitamin D. Rabbits on diets LG and GG had lower food and water intakes, lower faeces and urine output, grew faster and had higher body mass at slaughter (mainly attributable to adipose tissue). Apparent Ca digestibility decreased in the order L-LG-G/GG. Rabbits on L had larger and heavier kidneys, more urinary sediment at sonography, and a higher urinary Ca content than the other groups. No animal showed signs of urolithiasis/calcinosis at X-ray, sonography, or gross pathology. Kidney/aorta histology only sporadically indicated Ca deposits, with no systematic difference between groups. Under the conditions of the experiment, dietary Ca loads in legume hay do not appear problematic for rabbits, and other factors, such as water supply and level of activity may be important contributors to urolithiasis development in veterinary patients. However, due to the lower Ca content of grass hay, the significantly lower degree of urinary sludge formation, and the significantly higher water intake related with grass hay feeding, grass hay-dominated diets are to be recommended for rabbits in which urolithiasis prevention is an issue.     

Effects of plane of nutrition on growth,feed intake,digestibility and nitrogen balance in Murrah graded male buffalo (Bubalus bubalis) calves in Nepal

An experiment was conducted using 17 male buffalo calves to assess the effects of plane of nutrition on dry matter intake (DMI), daily gain (DG), body size measurement, apparent digestibility and nitrogen (N) balance. To attain 250 kg BW, the calves were allocated into three groups: H, L‐H and L, receiving the concentrate at 1.50% of BW, 0.75% of BW until 190 kg BW and 1.50% thereafter and 0.75% of BW, respectively. The animals had ad libitum access to urea‐treated rice straw (UTRS). The DMI of UTRS through the experiment was higher in L and L‐H than H, showing 3.52, 2.90 and 2.62 kg/day, respectively (P < 0.01), but the total DMI did not differ among the treatment groups. The DG throughout the experiment was high in the order of H, L‐H and L, showing 0.72, 0.57 and 0.45 kg, respectively (P < 0.01). The digestibility of DM, organic matter, crude protein, neutral and acid detergent fiber and N retention were higher in H than in L (P < 0.05). The findings of this study thus revealed the greater DG has an advantage of shortening the growing period around 3 months, and consequently increasing benefit in fattening of buffalo calves in Nepal.     

Effects of supplementary desalted mother liquor as replacement of commercial salt in diet for Thai native cattle on digestibility,energy and nitrogen balance,and rumen conditions

Four Thai native cattle were used in a 4 × 4 Latin square design experiment to evaluate the availability of desalted mother liquor (DML) as replacement of salt in concentrate. Each cattle was assigned to one of the following concentrate feeding treatments: C1, 1% NaCl was added as salt; C2, 2% NaCl was added as salt; D1, 1% NaCl was replaced by DML; D2, 2% NaCl was replaced by DML, on a dry matter (DM) basis. The animals were fed rice straw and experimental concentrates (40:60) at 1.9% of body weight on a DM basis, daily. Acid detergent fiber expressed exclusive of residual ash (ADFom) digestibility in DML treatment was higher than salt treatment (p < .05) and D2 feeding showed the highest value (60.8%). There were no significant differences in blood metabolites, nitrogen retention, ruminal ammonia nitrogen, methane emission or energy efficiency among treatments. Molar percent of acetate on volatile fatty acids in rumen fluid 4 hr post‐feeding tended to be higher in DML treatment than salt treatment (p = .08). The results indicated that adding DML could improve ADFom digestibility and salt could be replaced by DML up to 2% as NaCl in concentrate without adverse effects on nitrogen balance, rumen conditions, blood metabolites and methane emission.     

日粮蛋白水平和叶酸补充方式对奶公牛营养物质消化率、氮平衡以及血液代谢产物的影响

为了揭示日粮蛋白水平和叶酸补充方式对奶公牛营养物质消化率、氮平衡以及血液代谢产物的影响。试验选用8头9月龄、体重为(286.8±2.3) kg的中国荷斯坦奶公牛,随机分为4组,采用2[正常日粮(NPD)与高蛋白日粮(HPD)]×2[日粮补充3.6 mg/kg的叶酸(FA)或过瘤胃叶酸(RPFA)]因子的4×4拉丁方设计。结果显示,HPD显著提高了干物质、有机物、粗蛋白、粗脂肪、粗纤维、中性洗涤纤维和酸性洗涤纤维的消化率(P0.05),RPFA较FA仅提高了粗脂肪的消化率(P0.05)。采食氮、消化氮、沉积氮和沉积氮/消化氮随着日粮蛋白水平的提高而显著增加(P0.05)。RPFA显著提高了采食氮、粪氮和沉积氮(P0.05),降低了尿氮和尿氮/总排泄氮(P0.05)。HPD和RPFA均提高了血清中葡萄糖、白蛋白、总蛋白和叶酸(P0.05),降低了游离脂肪酸、乙酰乙酸和同型半胱氨酸(P0.05)。HPD显著提高了血清中尿素氮和甘油三酯(P0.05),而RPFA有相反的结果(P0.05)。HPD对血清β-羟丁酸浓度无影响(P0.05),但RPFA显著降低了其浓度(P0.05)。结果提示,在添加叶酸的前提下日粮蛋白水平为15.02%时可提高营养物质消化率和利用率,过瘤胃叶酸较叶酸提高了蛋白质利用率。     

Effect of human growth hormone-releasing factor and(or) thyrotropin-releasing factor on growth, carcass composition, diet digestibility, nutrient balance, and plasma constituents in dairy calves

Sixty male dairy grain-fed calves, raised from 70 to 223 kg BW in individual crates, were used in a 2 X 2 factorial arrangement to determine the effect of administration of human growth hormone-releasing factor (1-29)NH2 (GRF) and(or) thyrotropin-releasing factor (TRF). Calves received twice-daily s.c. injections of .9% NaCl (control), GRF (5 micrograms/kg BW), TRF (1 micrograms/kg BW) or GRF (5 micrograms/kg BW) plus TRF (1 micrograms/kg GTRF). Average daily gain and days on feed were not affected by treatments, but TRF treatment increased (P less than .05) total intake of dry matter (DM) and feed conversion ratio: 3.00, 3.02, 3.08, and 3.22 kg DM/kg weight gain for control, GRF, TRF, and GTRF, respectively. During two 7-d periods, after 66 and 75 d of treatment, feces and urine were collected from 40 calves (5 per treatment per period). Treatment with GRF increased (P less than .05) digestibility of DM, nitrogen (N), and energy and tended (P less than .20) to increase N retention. At slaughter, withers height was increased (P = .05) by GRF and carcass length was increased (P less than .05) by TRF. Pituitary and liver weights were increased (P less than .05) by TRF. The combination of GRF and TRF slightly increased (P less than .10) protein content and decreased (P less than .05) fat content of the 9-10-11th rib section. After d 1, GRF treatment chronically increased (P less than .05) insulin concentrations and also increased (P less than .10) IGF-I concentrations on d 29 and 57. In summary, chronic treatment with GRF and(or) TRF did not improve growth or efficiency, although GRF increased digestibility of DM, N, and energy and the GRF plus TRF combination resulted in slightly leaner carcasses.     

Effects of feeding sorghum-sudan, alfalfa hay and fresh alfalfa with concentrate on intake, first compartment stomach characteristics, digestibility, nitrogen balance and energy metabolism in alpacas (Lama pacos) at low altitude

The objective was to evaluate effects of feeding sorghum-sudan- or alfalfa-based diets on intake, first compartment stomach characteristics, digestibility, nitrogen balance and energy metabolism in alpacas at low altitude (793 m). Six mature alpacas (42 ± 2.3 kg of body weight) were used in a replicated 3 × 3 Latin square experiment. The treatments were: sorghum-sudan diets (SSD), alfalfa hay diets (AHD) and fresh alfalfa diets (FAD), respectively. Alpacas were housed in metabolism crates and diets were fed for 21 days with 11 d of adaptation and 10 d of sampling. Alpaca was supplemented concentrate with 160 g per alpaca per day and forages were fed at 12 h intervals with water provided ad libitum. First compartment stomach pH and ammonia N were unaffected by forage source, whereas total VFA concentration was different between diets, with the least for FAD (46.8 mM), followed by AHD (51.8 mM) and the highest for SSD (56.1 mM). Ratio of acetate to propionate was greater for AHD and SSD than for FAD diets. The molar proportion of acetate decreased, whereas the molar proportion of propionate increased for FAD relative to AHD and SSD. Redox potential was lower for SSD than for FAD. Surface tension was greater for FAD than for SSD and AHD. Osmolality was lower for FAD than for SSD and AHD. First compartment pressure and methane production tended to be higher for FAD than for SSD (P < 0.06) and AHD (P < 0.07). Digestibilities of DM, OM and EE were not different between diets. However, the digestibility of CP was lower for AHD relative to SSD and FAD. Digestibilities of NDF and ADF were greater for SSD than for AHD and FAD. Intakes of gross energy (GE) and N were greater for AHD than for FAD and SSD. Digestible energy (DE) was the highest in AHD followed by SSD and FAD. Metablizable energy (ME) was different with the lowest for FAD (3.9 MJ/day), followed by SSD (5.4 MJ/day) and the highest for AHD (8.1 MJ/day). Energy retained was followed the same trend as ME. The results demonstrate variable responses of alpacas to feeding sorghum-sudan or alfalfa diets in terms of dry matter intake, first compartment stomach characteristics, digestibility, nitrogen balance and energy metabolism at low altitude.     

Effect of rumen-degradable protein balance deficit on voluntary intake, microbial protein synthesis, and nitrogen metabolism in growing double-muscled Belgian Blue bulls fed corn silage-based diet

Two trials were conducted to evaluate the effect of rumen-degradable protein balance (OEB) deficit on voluntary intake (trial 1), microbial protein synthesis, and N metabolism (trial 2) in growing double-muscled Belgian Blue bulls. In trial 1, six bulls (339 +/- 26 kg of initial BW) were used in a replicated 3 x 3 Latin square and received a diet of 60% corn silage and 40% concentrate with ad libitum intake (DM basis). Three concentrates were formulated by adding urea at the expense of barley to give similar dietary contents of intestinal digestible proteins, NE for fattening, and fermentable OM, but with different levels of OEB. Thus, 2 levels of OEB deficit (-23.7 and -9.2 g of OEB/kg of DM) were compared with a diet providing a slight OEB surplus (5.3 g of OEB/kg of DM). Voluntary DMI decreased linearly (P = 0.02) with decreasing rumen-degradable protein balance. This decrease in intake could explain the linear decrease in ADG observed when negative OEB diets were fed. In trial 2, six bulls (304 +/- 12 kg of initial BW) with cannulas in the rumen and proximal duodenum were used in a replicated 3 x 3 Latin square and fed diets similar to those used in trial 1 at an intake level of 85 g of DM/kg of BW(0.75). Diurnal variations of ruminal NH(3)-N and plasma urea-N concentrations were greatly influenced by the level of OEB in the diet. No differences in NDF and starch degradation in the rumen, microbial N flow at the duodenum, or efficiency of microbial protein synthesis in the rumen were noted among the levels of OEB in diets. The reductions of the OEB value from 5.3 g/kg of DM to -9.2 g/ kg of DM and -23.7 g/kg of DM were associated with reductions of 26.5 and 48.8% in urinary N output. Absolute amounts of N retained by the bulls increased significantly with the level of OEB in diets. Indeed, 51.4% of the incremental supply of N was excreted between -23.7 and -9.2 g of OEB/kg of DM diets, and 74.6% of the incremental supply of N was excreted between -9.2 and 5.3 g of OEB/kg of DM diets. Feeding diets characterized by an adequate intestinal digestible protein supply and a OEB close to -10 g of OEB/kg of DM could be a feeding strategy to reduce N losses from the farm with little effect on the animal performance and voluntary intake. Reduced OEB may reduce N excretion in the environment but may also result in decreased N retention.     

ORIGINAL ARTICLE: Effects of supplementing rice straw with Leucaena (Leucaena leucocephala) and Madras thorn (Pithecellobium dulce) foliages on digestibility,microbial N supply and nitrogen balance of growing goats

A total of 12 crossbred (Boer × Anglo‐Nubian) goats were chosen from a commercial farm on the basis of similar body weight (25.0 ± 3.1 kg). The goats were housed in individual pens and allowed 3 weeks to adapt to experimental conditions. The goats were randomly allocated to three treatments in a 3 × 3 Latin square experiment (replicated four times). Within each period, each goat was given rice straw as roughage plus the respective treatment diet. The diets were iso‐nitrogenous and iso‐energetic containing cassava pulp, molasses, urea and commercial mineral and vitamin mix. The experimental treatments were (i) soybean meal (SBM), (ii) partial substitution of SBM with Leucaena (Leucaena leucocephala) foliage and (iii) partial substitution of SBM with Madras thorn (Pithecellobium dulce) foliage. Nutrient intakes, ruminal characteristics (pH, ammonia nitrogen and volatile fatty acids), nitrogen balances, plasma urea nitrogen and microbial N supply were not significantly different among treatments. The results of this study indicate that protein foliages from locally grown shrubs and trees can substitute imported feedstuff concentrates (e.g. SBM) as protein supplement for goat production.     

Influence of S. babylonica extract on feed intake, growth performance and diet in vitro gas production profile in young lambs

An experiment was completed to determine the effect of Salix babylonica (SB) extract supplementation to the diet of growing lambs. Eighteen Katahdin × Pelibuey male lambs (14?±?2 kg live body weight) were divided randomly in individual cages into three groups and fed three diets varying in SB: a control group was fed on total mixed ration (TMR) without SB (SB0), an SB25 group was fed on TMR plus SB extract at 25 mL/lamb/day, and an SB50 group was fed on TMR plus SB extract at 50 mL/lamb/day on dry matter intake (DMI), average daily gain (ADG), feed efficiency, and in vitro gas production (GP) in lambs fed on TMR. In vitro GP of the TMR fed to lambs was recorded at 2, 4, 6, 8, 10, 12, 24, 48, and 72 h of incubation with 0, 0.6, 1.2, and 1.8 mL extract per gram of DM. Addition of SB extract at low and high doses improved the DMI of lambs by 59.9 and 33.2 %, respectively. Relative to the control, low and high extract doses achieved greater lamb ADG during the experimental period. The asymptotic GP increased (P?<?0.05) with increasing dose of SB extract without affecting the rate of GP or the initial delay before GP begins. Linear increases for in vitro GP with advancing time with different SB extract doses were observed. It is suggested that the use of S. babylonica extract with the rate of 25 mL/lamb/day is beneficial to young lamb’s performance growth and thus can be safely used as a feed additive in diets without any negative effects on animal health.