Faecal nitrogen excretion as an approach to estimate forage intake of wethers

Data from twenty‐two digestibility trials were compiled to examine the relationship between faecal N concentration and organic matter (OM) digestibility (OMD), and between faecal N excretion and OM intake (OMI) by wethers fed tropical or temperate forages alone or with supplements. Data set was grouped by diet type as follows: only tropical grass (n = 204), only temperate grass (n = 160), tropical grass plus supplement (n = 216), temperate grass plus supplement (n = 48), tropical grass plus tropical legume (n = 60) and temperate grass with ruminal infusion of tannins (n = 16). Positive correlation between OMD and either total faecal N concentration (Nfc, % of OM) or metabolic faecal N concentration (Nmetfc, % of OM) was significant for most diet types. Exceptions were the diet that included a tropical legume, where both relationships were negative, and the diet that included tannin extract, where the correlation between OMD and Nfc was not significant. Pearson correlation and linear regressions between OM intake (OMI, g/day) and faecal N excretion (Nf, g/day) were significant for all diet types. When OMI was estimated from the OM faecal excretion and Nfc‐based OMD values, the linear comparison between observed and estimated OMI values showed intercept different from 0 and slope different from 1. When OMI was estimated using the Nf‐based linear regressions, the linear comparison between observed and estimated OMI values showed neither intercept different from 0 nor slope different from 1. Both linear comparisons showed similar R² values (i.e. 0.78 vs. 0.79). In conclusion, linear equations are suitable for directly estimating OM intake by wethers, fed only forage or forage plus supplements, from the amount of N excreted in faeces. The use of this approach in experiments with grazing wethers has the advantage of accounting for individual variations in diet selection and digestion processes and precludes the use of techniques to estimate forage digestibility.     

Intake and digestibility in cattle fed low-quality tropical forage and supplemented with nitrogenous compounds

The effects of supplementation with nitrogenous compounds on intake, digestibility, and microbial protein synthesis in cattle fed low-quality tropical forage were assessed. Five rumen fistulated crossbred Holstein × Gir heifers were used, with initial average live weight of 180 ± 21 kg. Signal grass (Brachiaria decumbens) hay (48.6 g kg⁻¹ of crude protein (CP), on a dry matter (DM) basis) was used as roughage. Five treatments were defined according to nitrogen supplementation level (0, 20, 40, 60, and 80 g of CP kg⁻¹ above the CP level of the hay). A mixture of urea, ammonium sulfate, and albumin at the ratios of 4.5:0.5:1.0, respectively, was used as nitrogen source. The experiment consisted of five experimental periods, according to a 5 × 5 Latin square design. The average CP contents in the diets were 51.9, 71.1, 86.0, 116.7, and 130.2 g kg⁻¹, on a DM basis. A quadratic effect was detected (P < 0.10) of the CP levels in the diets on DM and neutral detergent fiber intake (kg/day), with maximum response at the levels of 102.4 and 100.5 g CP kg⁻¹ DM, respectively. The average daily concentration of rumen ammonia nitrogen showed increasing linear pattern (P < 0.01) as function of CP levels in the diet, with estimated value of 9.64 mg dL⁻¹ equivalent to the maximum DM intake. Microbial nitrogen flow in the intestine was linearly and positively related (P < 0.01) with the CP levels in the diet.     

Comparative digestion, rumen fermentation and kinetics of forage diets by steers and wethers

Four rumen fistulated wether and beef steers were used to evaluate differences in dry matter digestibility (DMD) between cattle and sheep. They were fed either perennial ryegrass or switchgrass hay at an ad libitum or restricted level for four experimental periods. Significant ruminant species X forage and ruminant species X level of intake (P less than .05) interactions were observed for digestible dry matter. The steers digested the switchgrass 7 percentage units greater than the wethers while ryegrass was digested equally. Digestibility differences between the steers and wethers were 6 percentage units at the ad libitum level of intake and 1 unit at the restricted level of intake. Crude protein digestibility tended to be greater (P less than .10) for sheep with a 7 unit difference for switchgrass and a 3 unit difference for ryegrass. The mean ruminal solids retention time of the digesta was approximately (P less than .01) 50% greater (26.0 vs 17.4 h) in cattle, with no difference in ruminal liquid dilution rate (LD) between animal species. Total ruminal volatile fatty acid concentration differed (P less than .01) with level of intake; however, no influence due to intake on the molar proportion of acetate (P greater than .10) or propionate (P greater than .10) was evident in spite of a difference (P less than .01) in LD. Rumen pH (P less than .05) and osmolality (P less than .01) were affected by both level of intake and forage, with the ryegrass and high level of intake decreasing pH and increasing osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intake and digestibility of low-quality meadow hay by cattle receiving various levels of whole shelled corn

Two trials were conducted to evaluate the effects of whole shelled corn supplementation on intake and digestibility of low-quality meadow hay by cattle. In Trial 1, four ruminally cannulated steers (avg BW 418 kg) were used in a latin square design with four treatments (no corn or corn fed at .25%, .50% or .75% of BW). Hay DMI decreased (P = .002) linearly .43 g for each gram of increase in corn intake. In contrast, total diet DMI increased (P = .001) linearly as level of corn supplementation increased. Apparent DM digestibility of the diet increased (P = .026) linearly, whereas hay DM digestibility was not affected (P greater than .05) by supplemental corn, although the DM digestion coefficient for hay alone was 24% higher than for hay fed with corn at .75% of BW. Ruminal ammonia concentration and pH were not affected (P greater than .05) by treatments; however, ratio of acetate:propionate and acetate:butyrate responded (P less than or equal to .097) quadratically to increased corn supplementation. Corn supplementation resulted in a cubic (P less than or equal to .081) decrease in meadow hay NDF disappearance from nylon bags suspended in the rumen at all incubation intervals after 4 h. In Trial 2, 45 crossbred, nonlactating, pregnant cows (avg BW 474 kg) were used in a completely randomized design with three treatments (no corn, .91 and 1.81 kg corn.hd-1.d-1). Cow performance was not altered (P greater than .05) by treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of forage offering method on performance,rumen fermentation,nutrient digestibility and nutritional behaviour in Holstein dairy calves

The potential effect of dietary forage supplementation on the performance and rumen development in dairy calves is well established. However, limited research has been directed to the comparative effects of forage offering methods on calf performance. The objective of the present study was to determine the effects of forage provision methods (total mixed ration or free choice) on the performance, nutrient digestibility, rumen fermentation and nutritional behaviour in newborn calves. Forty‐five Holstein dairy calves (3 days of age and 41 ± 2 kg of body weight) were assigned to the following three groups (n = 15): (i) starter without forage provision (CON), (ii) starter supplemented with 10% alfalfa hay (AH) as a total mixed ration (AH‐TMR) and (iii) starter and AH as a free‐choice provision (AH‐FC) for a period of 70 days. All the calves were offered 5 l of milk/day from day 3 to 50, and 2.5 l/day from day 50 until weaning on day 56. Dry matter intake (DMI) was greater (p < 0.01) in the AH‐TMR and AH‐FC treatments than in the CON during the pre‐ and post‐weaning periods. Calves fed the AH‐FC diet showed the highest post‐weaning DMI among the treatments. The calves receiving ad libitum forage tended (p = 0.08) to increase crude protein digestibility and overall volatile fatty acids (VFA) concentrations in the rumen. No differences were observed among the treatments at the time spent on standing, lying, eating and performing non‐nutritive oral behaviours. Compared to CON calves, animals in the AH‐TMR treatment spent more time (p < 0.05) ruminating. In conclusion, our data suggest that forage supplementation in both forage offering methods increased total DMI, ruminal pH and ruminating time in dairy calves. Hence, there is no benefit in the free‐choice provision of AH in dairy calves.     

Intake and digestion of wheat forage by stocker calves and lambs

Because wheat forage contains high concentrations of N, NPN, digestible DM, and water, beef cattle and sheep require an adaptation period before positive BW are seen. The objective of the present experiment was to determine the impact of length of exposure of lambs and steers to wheat forage on BW gains, N retention, and forage digestibility. Sixteen steer calves (average BW = 210 +/- 12 kg) and 20 wether lambs (average BW = 31.5 +/- 2.0 kg) were randomly assigned to 1 of 2 treatment groups. Group 1 grazed a wheat pasture for 120 d during the winter, whereas group 2 was wintered on dormant warm-season grass pastures plus warm-season grass hay and plant-based protein supplements. In the spring (April 5), all lambs and steers grazed wheat pasture for 14 d and were then housed in metabolism stalls and fed freshly harvested wheat forage to determine forage digestibility and N metabolism. Data were analyzed for lambs and steers separately as a completely randomized design, using the individual animal as the experimental unit. Lambs and steers grazing wheat pasture for the first time in the spring had less ADG during the first 14 d than lambs (80 vs. 270 g, respectively; P = 0.01) and steers (1.06 vs. 1.83 kg, respectively; P = 0.09) that had grazed wheat pastures all winter. Digestibility of DM, NDF, and ADF fractions and N metabolism of freshly harvested wheat forage by lambs and steers were not different (P > 0.10) between the 2 treatment groups. Less ADG during the first 14 d of wheat pasture grazing is most likely the result of less DMI by nonadapted animals and is not due to diet digestibility or N metabolism.     

Performance, body composition and carcass characteristics of finishing steers as influenced by previous forage systems

To evaluate effects of previous forage systems on feedlot performance, yearling Hereford steers (average initial weight of 249 kg) were grazed on tall fescue (TF), smooth bromegrass-red clover (BG-RC) or orchardgrass-red clover (OG-RC) pastures before finishing. Serial slaughter was utilized during the first 2 yr of this study to determine changes in carcass characteristics throughout finishing, while steers were slaughtered at approximately 29% body fat during the third year. Steers grazing TF entered the feedlot at lighter weights and maintained lighter weights throughout finishing (P less than .05) even though dry matter intakes and feed conversions were similar (P greater than .05) among treatments. Steers that previously grazed TF had less (P less than .05) body fat, body protein, fat thickness and marbling, smaller (P less than .05) ribeye areas and lower (P less than .05) USDA yield and quality grades than than those that grazed BG-RC and OG-RC. However, linear contrasts indicated that steers grazing TF were compensating in ribeye area, marbling and quality grade as days in feedlot increased. This was confirmed in the third-year study, since carcass characteristics were similar among all steers. During the third year, linear and quadratic contrasts indicated that steers that grazed TF partially compensated in body protein. As days in feedlot increased, live and hot carcass weights, body fat, fat thickness, kidney, pelvic and heart fat, marbling, and USDA yield and quality grades increased (P less than .05), while ribeye area and body protein plateaued. Although carcass characteristics were similar among treatments, steers backgrounded on TF entered the feedlot at lighter weights, and partially compensated in weight after 134 d of finishing.     

Flavomycin effects on performance of beef bulls and nutrient digestibility in wethers

For 28 weeks a feeding experiment was conducted to determine the effects of dietary flavomycin on performance of beef bulls. In the first and second half of the trial, 40 animals (average initial weight 352 kg) had free access to corn silage or beet pulp, respectively, both supplemented with an appropriate concentrate containing 0 or 10 mg/kg of the antibiotic. Daily flavomycin intake was 39 to 46 mg when the animals were on the corn silage diet and 51 to 54 mg when they were fed the beet pulp diet. The animals fed the corn silage-based diet supplemented with flavomycin showed a non-significant improvement of daily gain (1.4%) and feed conversion (2.3%). When the beet pulp-based diet was fed, flavomycin significantly increased daily gain (15.2%, P less than 0.002) and feed conversion efficiency (9.1%, P less than 0.03). For the overall feeding experiment the positive effect of flavomycin feeding was 6.7% on body weight gain (P less than 0.09) and 5.2% on feed conversion (P less than 0.13). Flavomycin did not affect carcass yield of beef bulls. Also the effect of flavomycin on diet digestibility was studied in wethers fed a mixture of beet pulp and concentrate, containing 0 or 10 ppm flavomycin. No significant effect from the antibiotic on digestion of dry matter, crude protein, fibre, fat, ash and N-free extract was observed.     

Fluid and particulate retention times in sheep as influenced by intake level and forage morphological composition

Objectives of this study were 1) to measure small-particle and liquid mean retention time (MRT) of 12 grass hays similar in NDF (61.3 +/- 1.9% NDF) but differing in morphological composition and to relate passage rates to proportions of blade, sheath and stem and 2) to evaluate the influence of MRT of small and large blade and stem fractions and large sheath fractions, in addition to morphological composition, on intake and digestibility of the 12 hays. In each of two periods, 24 sheep (wethers) were offered one of 12 hays at three consecutive levels of feeding: (L1) ad libitum, allowing 15% refusal; (L2) restricted to 100% of hay consumed ad libitum by an individual wether during L1; and (L3) 1.8% of BW on a DM basis. Hays offered included two sorghum-sudan, four barley, four oat and two pearl millet. Marked particles were pulse-dosed in L2 and L3. Large and small particles of stem and leaf were extracted with neutral detergent and marked with Cr or rare earth metals. Marked large and small stem particle MRT generally were longer (P less than .05) than those of corresponding large and small blade particles. Large sheath particles generally had an intermediate (P less than .05) MRT between those of large stem and blade particles. Mean retention times of marked fractions were lower (P less than .05) in L2 than in L3. Small particle MRT in L2 was longer than MRT for liquid, though correlations were high (r = .74 to .86, P less than .01). Large particles were retained longer than small particles. Particle size, morphology, and percentage of stem in the forage influenced the mean retention time. Use of representative samples of all fractions fed to measure retention times may lead to a better understanding of ruminal function and to improvements in explanations of intake regulation, because marked fractions do not behave identically for all forages.     

Intake and digestibility of low-quality native grass hay by beef cows supplemented with graded levels of soybean hulls

Twelve Hereford cows and four mature, ruminally cannulated Hereford x Angus heifers were fed supplements providing either 0 (control), 1, 2, or 3 kg/d of soybean hulls and including 440 g of protein/d (cottonseed meal was used to equalize protein intake) to determine the effects of supplementation on intake and utilization of low-quality native grass hay. Cattle were housed in individual pens and fed coarsely chopped (5-cm screen) native grass hay harvested in mid-November (4.1% CP, 76.9% NDF). Hay OM intake peaked (quadratic, P = .04) at 10.1 kg/d with 1 kg of soybean hulls and decreased when 2 kg (9.8 kg/d) or 3 kg (9.1 kg/d) of soybean hulls were fed. Although hay intake decreased when soybean hulls replaced cottonseed meal, feeding 3 kg soybean hulls decreased hay OM intake by only .64 kg. Total OM digestibility increased linearly (P = .009) with added increments of soybean hulls (45.8%, 46.2%, 46.6% and 48.6% for 0 through 3 kg soybean hulls/d, respectively), indicating that hulls were more digestible than the hay. Digestibility of NDF was not affected (P = .14) by level of soybean hull supplementation, although ADF digestibility increased (linear, P = .03). Increases in OM intake and digestibility with soybean hulls combined to increase digestible OM intake (linear, P = .0001). Soybean hull supplementation increased ruminal VFA concentrations (linear, P = .04) and the molar proportion of propionate (linear, P = .006).(ABSTRACT TRUNCATED AT 250 WORDS)     

Meat composition and palatability of Holstein and beef steers as influenced by forage type and protein source.

This experiment determined meat composition and palatability changes resulting from feeding Holstein (HOL) and crossbred beef (XB) steers diets containing corn silage (CS) or alfalfa haylage (AH) (forage type) and soybean meal (SM) or fish meal (FM) (protein source). Fifty-nine steers (30 HOL and 29 XB) were randomly assigned to diet combinations for a 2 x 2 x 2 (breed x forage x protein) factorial arrangement. Steers were fed to a fat-constant end point (fat depth over the longissimus muscle measured by ultrasound: 1.0 cm XB, .6 cm HOL). Proximate and fatty acid analysis and sensory evaluation were conducted on a rib eye roast and steaks, respectively, removed from the left side of each carcass at ribs 9 to 12. Proximate analysis of the longissimus muscle showed no significant difference (P greater than .05) in moisture, protein, or fat content due to breed, forage, or protein treatment. Forage type had no significant effect (P greater than .05) on amount of individual fatty acids found in longissimus muscle. However, total polyunsaturated fatty acids were higher (P greater than .05) for AH than for CS-fed animals. Longissimus muscle from steers fed FM had higher palmitoleic and lower stearic acid contents (both P less than .05) than longissimus muscle from animals fed SM. Muscle from HOL had higher palmitoleic and lower stearic acid contents than that from XB steers (both P less than .05). There was no significant interaction (P greater than .05) of breed with either diet treatment for individual fatty acid contents.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intake,digestibility and rumen dynamics of neutral detergent fibre in cattle fed low-quality tropical forage and supplemented with nitrogen and/or starch

The objective of this work was to evaluate the effects of nitrogenous compounds and/or starch supplementation on the intake, digestibility and rumen dynamics of neutral detergent fibre (NDF) in cattle fed low-quality tropical forage. Four crossbred heifers (Holstein × Zebu) with a body weight 231.9 ± 15.5 kg and fitted with ruminal cannulae were used. The forage fed to the animals consisted of low-quality signal grass (Brachiaria decumbens Stapf.) hay, with an average crude protein (CP) level of 51.6 g/kg, on a dry matter (DM) basis. Four treatments were evaluated: control, without supplementation; supplementation with nitrogenous compounds (CP of the roughage was raised to 100 g/kg), on a DM basis; supplementation with starch at a ratio of 200 g/kg DM of roughage; and supplementation with nitrogenous compounds and starch as described above. A mixture of urea, ammonium sulphate and albumin was used as a source of nitrogenous compounds at a ratio of 4.5:0.5:1.0. The experiment was carried out according to a 4 × 4 Latin square design in a 2 × 2 factorial arrangement. There was a positive effect of the nitrogenous compound supplementation on the DM and NDF intake (P < 0.01). In contrast, starch supplementation decreased forage intake (P < 0.10). Nitrogen supplementation increased the digestibility coefficient of DM and NDF (P < 0.05). Supplementation with nitrogen and starch together increased the microbial assimilation of nitrogenous compounds in the rumen (P < 0.05). We observed that nitrogen supplementation increased the estimated weighted degradation rate of NDF by 14.8%, whilst starch supplementation decreased this rate by 32.5%.     

Intake,digestibility and nitrogen utilization in cattle fed tropical forage and supplemented with protein in the rumen,abomasum,or both

Background: There is little information in the tropics with regard the comparative understanding of how an increased nitrogen supply in the rumen or in the intestines affects efficiency of nitrogen utilization in cattle. This study evaluated the effects of supplementation with nitrogenous compounds in the rumen, abomasum, or both on intake, digestibility and the characteristics of nitrogen utilization in cattle fed tropical forage. Four rumen- and abomasum-fistulated Nellore bulls(227 ± 11 kg) were used. Four treatments were evaluated: control, ruminal supplementation(230 g/d of supplemental protein in the rumen), abomasal supplementation(230 g/d of supplemental protein in the abomasum), and ruminal and abomasal supplementation(115 g/d protein in both the rumen and the abomasum).The basal forage diet consisted of Tifton 85 hay with a crude protein(CP) level of 78.4 g/kg dry matter. Casein was used as a supplement. The experiment was conducted using a 4 × 4 Latin square.Results: There were no differences between the treatments(P 0.10) with regard to forage intake. The intake and total digestibility of CP increased(P 0.01) with supplementation. The nitrogen balance in the body increased(P 0.01) and muscle protein mobilization decreased(P 0.01) with supplementation, regardless of the supplementation site.The efficiency of nitrogen utilization did not differ among the treatments(P 0.10).Conclusions: The supplementation of cattle fed tropical forage with protein in the rumen, abomasum, or both similarly increased the nitrogen accretion in animal, which reflects improvements on nitrogen status in animal body.     

In vitro rumen fermentation and digestibility of buffaloes as influenced by grape pomace powder and urea treated rice straw supplementation

This study aimed to investigate the effect of grape pomace powder levels and roughage sources on gas kinetics, digestibility and fermentation of swamp buffaloes by using in vitro techniques. The experimental design was a 2 × 4 factorial arrangement in a completely randomized design. Factor A was two sources of roughage (untreated rice straw, RS, and 3% urea treated rice straw, UTRS) and factor B was four levels of grape pomace powder (GPP) supplementation (0, 2, 4, 6% of substrate) on a dry matter basis. Results revealed that GPP supplementation at 2, 4 and 6% of substrate influenced gas kinetics. Cumulative gas production tended to be lower in the supplemented group. In vitro true digestibility was higher in the GPP supplementation at 2% with UTRS while microbial mass was higher in the supplemented groups. Supplementation of GPP significantly increased the total volatile fatty acids, especially propionate. Calculated methane production was subsequently decreased in the supplemented groups. Bacterial population was higher while protozoal population was lower by GPP supplementation. It could be concluded that supplementation of GPP at 2% of the substrate with UTRS improved in vitro true digestibility, rumen fermentation end‐products as well as reducing methane production.     

体外发酵技术研究秸秆粗饲料营养价值及降解特性

为了探究粗纤维饲料对反刍动物的营养特性,本试验研究了2种农作物秸秆(稻秸,麦秸)的发酵特性和动态降解率。试验分3组(稻秸组,麦秸组,混合组:50%稻秸+50%麦秸),采用瘤胃体外发酵技术,测定粗饲料的发酵参数变化。结果表明:三种粗饲料累计产气量和干物质(DM)降解率均随时间延长而增加,产气和DM降解主要集中在12~48 h。发酵12 h时,麦秸组和混合组累计产气量显著高于稻秸组(P0.05),麦秸组和混合组差异不显著。发酵24 h时,麦秸组累计产气量显著高于稻秸组和混合组(P0.05),稻秸组和混合组差异不显著。发酵36~72 h时,累计产气量均呈现麦秸组混合组稻秸组(P0.05)。发酵24 h时,稻秸组干物质降解率、中性洗涤纤维(NDF)降解率、发酵液中氨态氮(NH4-N)浓度均显著高于麦秸组和混合组(P0.05),乙酸浓度显著高于麦秸组(P0.05),而菌体蛋白(MCP)浓度呈现麦秸组混合组稻秸组(P0.05)。发酵48 h时,麦秸组乙酸浓度与酸性洗涤纤维(ADF)降解率均显著高于稻秸组和混合组(P0.05)。发酵72 h时,麦秸组ADF降解率显著高于混合组和稻秸组(P0.05)。结果提示,禾本科粗饲料在瘤胃内降解规律基本一致,主要发生在12~48 h,稻秸DM、NDF、ADF降解高峰期要早于麦秸及二者混合,稻秸的营养价值略高于麦秸。     

Intake,digestibility and metabolism in sheep fed with increasing levels of spineless cactus (Nopalea cochenillifera Salm-Dyck)

Tropical Animal Health and Production - The objective of this study was to evaluate the effect of the substitution of Tifton 85 hay (Cynodon spp.) with spineless cactus (Nopalea cochenillifera) on...     

多营养补充对黄牛氮平衡和草料营养物质消化率的影响

按 2个 3× 3的拉丁方设计研究了利用舔砖进行多营养补充对黄牛氮平衡和草料营养物质消化率的影响。结果表明 :多营养补充可明显改善黄牛的增重速度 (P<0 .0 1)和饲料转化率 (P <0 .0 5) ,使黄牛的日增重在单喂稻草、氨化稻草和干草的基础上分别提高了2 4 .99%、16 .12 %和 2 2 .92 % ;可提高牛对草料中 DM、OM、CP、NDF和 ADF等成分的摄入量并减少这些成分的粪中排泄量 ;显著 (P<0 .0 5)提高草料中 DM、OM、NDF和 ADF的消化率和极显著 (P<0 .0 1)提高 CP的消化率 ;明显改善黄牛的氮平衡 ,显著 (P<0 .0 5)增加氮的摄入量和存留量 ,极显著 (P<0 .0 1)提高氮和蛋白质的利用率。说明多营养补充不失为提高养牛生产水平的有效途径