Influence of urea–calcium mixtures as rumen slow-release feed on in vitro fermentation using a gas production technique

In this experiment the effects of different urea products (urea [U] and urea–calcium mixtures [UCM]) on rumen fermentation were investigated in dependence of different energy sources by using in vitro techniques. The 7 × 2 factorial arrangement followed a completely randomised design using seven urea products (U100, U40CaCl₂, U50CaCl₂, U60CaCl₂, U40CaSO₄, U50CaSO₄ and U60CaSO₄) in combination with cassava chips (CC) or corn meal (CM). Compared with other treatments, the cumulative gas production (96 h) was significantly increased for U60CaCl₂ + CC and U60CaSO₄ + CC (p < 0.01), which was combined with a higher in vitro true digestibility (p < 0.01). In addition, the concentration of volatile fatty acids in the fluid of U60CaCl₂ + CC and U60CaSO₄ + CC was significantly higher than in other treatments. Urea treatments (U100 + CC and U100 + CM) caused the highest concentration of ruminal ammonia nitrogen (p < 0.01), which was significantly decreased by all UCM products in combination with CC, but not with CM. The highest levels of total bacteria, Fibrobacter succinogenes and anaerobic fungi were found for treatment U60CaCl₂ + CC and U60CaSO₄ + CC (p < 0.05). The findings revealed that the utilisation of U60CaCl₂ and U60CaSO₄ in combination with cassava chips improved the ruminal fluid fermentation in terms of NH₃-N and volatile fatty acid concentration, digestibility of energy and increased the fibrobacter concentrations.     

Influence of urea calcium mixture supplementation on ruminal fermentation characteristics of beef cattle fed on concentrates containing high levels of cassava chips and rice straw

The purpose of this study was to evaluate the effects of various N sources in concentrates containing high levels of cassava chips, with rice straw as the basal forage, on rumen ecology, rumen microbial counts, microbial crude (CP) protein synthesis, and digestibility of nutrients. Four ruminally fistulated crossbred (Brahman × native) beef steers with initial body weight (BW) of 400 ± 40.2 kg were randomly assigned according to a 4 × 4 Latin square design. The dietary treatments were different sources of N in the concentrates and were: T1 = urea (control; urea); T2 = soybean meal (SBM); T3 = urea CaCl₂ mixture (U-Cal); T4 = urea CaSO₄ mixture (U-Cas). All steers were kept in individual pens and supplemented with concentrate at 5 g/kg of BW daily. The experiment was 4 periods, and each lasted 21 d. During the first 14 d, all steers were fed their respective diets ad libitum and for during the last 7 d, they were moved to metabolism crates for total urine and fecal collection. Dry matter intake ranged from 9.8 to 10.5 kg daily and was not altered by diet, while digestibility of NDF differed among treatments and was highest with U-Cas supplementation (P<0.05). Ruminal NH₃ N and plasma urea N with U-Cal, U-Cas, and SBM diets were lower compared with the urea supplemented group (P<0.05). Ruminal volatile fatty acid concentrations were not altered by treatments. Total viable, and cellulolytic bacteria, differed among treatments and were highest with U-Cas (9.1 × 10¹¹, and 4.0 × 10⁹ cfu/mL, respectively). In addition, efficiency of rumen microbial CP synthesis based on organic matter (OM) truly digested in the rumen was increased by SBM or U-Cal supplementation, and was highest with U-Cas supplementation (18.2 g of N/kg of OM truly digested in the rumen). Supplementation of U-Cas to a concentrate containing a high level of cassava chips improved rumen ecology and microbial CP synthesis in beef cattle, suggesting that urea calcium mixtures can replace soybean meal or urea in beef cattle diets without adverse affects on rumen fermentation and other rumen parameters.     

Effect of different levels of concentrate on ruminal microorganisms and rumen fermentation in Nellore steers

The aim of this study was to investigate the effect of different dietary levels of concentrate on feed intake, digestibility, ruminal fermentation and microbial population in steers. Eight Nellore steers fitted with ruminal cannulas were used in a double 4 × 4 Latin square design experiment. The dietary treatments consist of four different proportions of concentrate to roughage: 30:70, 40:60, 60:40 and 80:20% in the dry matter, resulting in Diets 30, 40, 60 and 80, respectively. The roughage was corn silage, and the concentrate was composed of corn, soybean meal and urea. Apparent digestibility of organic matter and crude protein showed a linear association with concentrate proportion (p = 0.01), but the increased concentrate levels did not affect the digestibility of fibre. The lowest ruminal pH-values were observed in animals fed with Diet 80, remaining below pH 6.0 from 6 h after feeding, while in the other diets, the ruminal pH was below 6.0 not before 12 h after feeding. After feeding Diet 80, the ammonia concentration in the rumen was significantly the highest. Higher dietary concentrate levels resulted in a linear increase of propionic acid concentrations, a linear reduction of the ratio acetic acid to propionic acid (p < 0.01) and a linear increased synthesis of microbial nitrogen (p < 0.001). The predicted production of methane was lower in diets with greater amounts of concentrate (p = 0.032). The population of methanogens, R. flavefaciens and R. albus decreased with higher concentrate levels, while the population of S. ruminantium increased (p < 0.05). The results indicate that greater amounts of concentrate do not decrease ruminal pH-values as much as expected and inhibit some cellulolytic bacteria without impairing the dry matter intake and fibre digestibility in Nellore steers.     

Formulating rations with cassava meal to promote high live weight gain in crossbred Limousin bulls

Formulating rations with high energy and protein feeds such as cassava and locally sourced protein meals is an important strategy to increase live weight gain (LWG) of crossbred bulls in Indonesia. Current systems of production for Indonesian smallholders fatten bulls using cut and carry. Formulating a diet for an optimal combination of available feeds will increase production and potential profitability for smallholders. An experiment was conducted to evaluate the effect of using cassava meal in the diet at levels of 70C, 60C, 50C, 40C and 30C% (with most of the remainder being the protein meals) on the LWG of Limousin × Ongole bulls so as to determine the optimum combination of cassava meal and protein meals for LWG. Thirty bulls were allocated in a completely randomized block design with 6 blocks based on initial live weight (LW) and 5 treatments based on level of cassava meal. The combination of cassava meal (with 2% urea) and protein meals significantly affected LWG with the highest (1.35 kg/day) recorded at 40C (40% cassava meal, 40% protein meals and 20% maize stover). The LWG and nutrient intake increased curvilinearly with decreasing cassava meal and increasing protein meals (P < 0.05). Measured cassava meal inclusion in the final ration as a consequence of the changes in intake was 60, 56, 47, 37 and 28% for the designated 70C, 60C, 50C, 40C and 30C treatments, respectively. Dry matter intake reached 96 g/kg^0.75 per day or equal to 2.24% LW at this 40% level of inclusion. At the 70C treatment with 60% cassava meal and 9% protein meals, DM digestibility (69.1%) was lowest and that value increased as the proportion of cassava meal decreased and was highest at the 40C treatment (75.8%). Feed treatments significantly affected rumen pH, ammonia N (NH₃N) and volatile fatty acid concentrations (P < 0.05). There was no significant effect on protozoal population (P > 0.05). Rumen pH ranged from 6.3 to 6.9. It was concluded that a combination of 40% dried cassava meal and 40% protein meals with roughage (20%) maximized intake and LWG and beyond that level of cassava meal inclusion, LWG and intake decreased markedly.     

Intake and digestion by lambs of dwarf elephant grass (Pennisetum purpureum Schum. cv. Mott) hay or hay supplemented with urea and different levels of cracked corn grain

This study was carried out to evaluate intake, digestibility, ruminal fermentation, nitrogen (N) retention and ruminal microbial protein synthesis in lambs fed dwarf elephant grass (Pennisetum purpureum Schum. cv. Mott) hay or hay supplemented with urea and 0, 5, 10 or 15 g/kg of live weight (LW) of cracked corn grain. Ten lambs (mean LW of 28 ± 0.9 kg), housed in metabolic cages, were used in a double 5 × 5 Latin Square experiment. Except fibre intake and digestibility, which was higher, the intake and digestibility of the others feed components, as well as ruminal microbial protein synthesis and N retention were lower in non-supplemented lambs. Corn supplementation increased total dry matter (DM) (P<0.05), organic matter (OM), non-structural carbohydrate (NSC) and energy intake (P<0.01) but decreased total neutral detergent fibre (aNDFom) (P<0.01) intake, as well as OM and aNDFom intake from the hay (P<0.01). Apparent DM, OM and energy digestibility, as well as OM true digestibility (OMTD) increased (P<0.01), and aNDFom digestibility decreased linearly (P<0.01) as corn supplementation increased. Total N intake was not influenced but, apparent and true N digestibility, as well as urinary N excretion decreased (P<0.01), and ruminal microbial N entering the small intestine increased linearly (P<0.01) as corn supplementation increased. However, the efficiency of ruminal microbial protein synthesis was similar for all treatments. Mean ruminal pH values and ammonia N concentrations decreased linearly (P<0.01) with level of corn supplementation. Ammonia N and amino acid, as well as peptide concentrations in ruminal fluid were quadratically related (P<0.01) with the time after feeding. Corn supplementation had a linear additive effect on total dry matter and digestible energy intake, as well as on N retention, but a linear negative effect on hay intake and on fibre digestibility. However, decreased forage digestibility by animals was probably neither related to lower ruminal pH, which values were always higher than 7.0, nor related to ruminal sugar concentrations, which were similar for all treatments.     

A process for protein enrichment of cassava by solid substrate fermentation in rural conditions

An artisanal static process for protein enrichment of cassava by solid-state fermentation, developed in laboratory and tested on pilot units in Burundi (Central Africa), provides enriched cassava containing 10.7% of dry matter protein versus 1% before fermentation. Cassava chips, processed into granules of 2-4-mm diameter, are moistened (40% water content) and steamed. After cooling to 40 degrees C, cassava is mixed with a nutritive solution containing the inoculum (Rhizopus oryzae, strain MUCL 28627) and providing the following per 100 g dry matter: 3.4 g urea, 1.5 g KH(2)PO(4), 0.8 g MgSO(4).7H(2)O, and 22.7 g citric acid. For the fermentation, cassava, with ca. 60% moisture content, is spread in a thin layer (2-3 cm thick) on perforated trays and slid into an aerated humidified enclosure. The incubation lasts +/- 65 h. The production of protein enriched cassava is 3.26 kg dry matter/m(2) tray. The effects of the variation of the nutritive solution composition and the inoculum conservation period on the protein production are equally discussed.     

控释肥及其与尿素配合施用对水稻生长期N_2O排放的影响

通过田间试验,采用静态箱法研究相同施氮量条件下,施用尿素、控释肥及尿素与控释肥配施(尿素与控释肥以3:7配合施用)对稻田N2O排放的影响.结果表明:与单施尿素处理相比,配施处理和控释肥处理水稻生长期N2O排放量分别减少40.4%和59.6%(P<0.05),其中烤田期分别减少65.1%和83.9%;与配施处理相比,施用控释肥处理N2O排放量略微减少(P>0.05),其中烤田期减少53.9%.施用控释肥可增加水稻产量,与尿素处理相比,施用控释肥和配施处理水稻产量分别增加7.8%和9.8%(P>0.05).施用控释肥使土壤无机氮峰值出现时间延后,烤田期N2O排放减少.水稻生长期N2O排放通量与土壤氧化还原电位(Eh)和土壤温度均无明显相关性(P>0.05).     

Cassava meal and cassava peel meal in diets for growing pigs

Experiments were conducted to study the inclusion of 0, 30, 45 and 60% sun-dried, ground cassava tubers (CM) in growing rations; and of 15 and 30% CM plus 15 and 20% sun-dried, ground cassava peel (CPM) in finishing rations of Large White and local pigs. Growing pigs receiving rations containing CM or CPM grew slightly but non-significantly faster and were slightly more efficient in feed conversion than pigs on the control diet. Generally, Large White pigs appeared to utilise CM better than local pigs while local pigs utilised CPM better than Large White pigs. Carcasses of control pigs had significantly higher dressing values than those of pigs on the substituted rations. Cassava meal, being more digestible than CPM, increased the digestibility of CM—CPM mixtures.     

包膜控释尿素与普通尿素配施对冬小麦生长发育及土壤硝态氮的影响

应用大田试验研究了不同用量的包膜控释尿素(PCU60,释放期为60 d)与普通尿素(U)配合基施(10%PCU60+90%U,PU1;20%PCU60+80%U,PU2;30%PCU60+70%U,PU3;40%PCU60+60%U,PU4)对冬小麦产量、氮肥利用率等生物学性状及土壤硝态氮累积的影响,并对PCU60氮素田间溶出特征及25℃静水溶出特征进行了比较分析.结果表明:在施氮量相等的条件下,与习惯施肥处理相比,PU4处理冬小麦各项指标均显著提高:增产5.6%、氮肥利用率提高14.6%、氮素总累积量提高7.2%、成熟期总茎数提高2.6%、成熟期地上部总生物量提高7.5%、经济效益增加984.3元·hm-2.各处理0～100 cm土层硝态氮总累积量在39.70～49.93 kg·hm-2,其中,PU4处理总累积量最低,为39.70 kg·hm-2.埋袋试验表明,释放期为60 d的包膜控释尿素氮素释放规律与小麦氮素吸收特性基本吻合.     

Effects of protein and energy supplementation on growth,forage intake,forage digestion and nitrogen balance in meat goat kids

The objective of this study was to further the understanding of the effects of dietary protein and energy supplements on growth, performance, feed intake and grass forage digestibility in growing meat goat wethers. In Experiment 1, an 18% CP complete goat pellet was offered alone (control diet, C) or added (+), or not, as supplement to three grass hays (coastal bermudagrass, CB; Tifton 85 bermudagrass, T; and sorghum-Sudan grass hay, SS), to Boer-cross wethers (n = 72). The resulting seven diets were offered ad libitum. In Experiment 2, four wether goats in metabolism crates were used in a 4 × 4 Latin square design and fed a SS basal diet ad libitum with treatments consisting of no supplement, supplemental urea (200 mg/kg BW daily), supplemental dextrose (0.2% BW daily), or urea + dextrose (200 mg/kg BW daily and 0.2% BW daily, respectively). In Experiment 1, average daily gain (ADG) were −3.8, −5.0 and −6.6 g/day for goats consuming CB, T and SS, respectively, and 69.2, 61.6 and 58.1 g/day for supplemented CB (CB+), T (T+) and SS (SS+), respectively, as compared to 245.8 g/day for ad libitum access to C. Supplementation in Experiment 1 increased (P < 0.01) ADG for all hays when compared to hay-only diets. In Experiment 2, protein and energy supplementation increased (P < 0.01) nitrogen retention but did not impact diet digestibility. The beneficial effects of supplements in Experiment 1 and the increase in nitrogen retention in Experiment 2 cannot be explained by improvements in ruminal fiber utilization, but could be due to post-ruminal nutrient supply and/or increased ruminal microbial protein synthesis.     

持续施用缓/控释尿素条件下水田土壤NH3挥发与N2O排放特征

以持续9年施用不同缓／控释尿素的水田棕壤为试验对象,以普通大颗粒尿素为对照,研究了持续施用不同缓／控释尿素条件下水田土壤NH₃挥发与N₂O排放特征.结果表明: 与普通大颗粒尿素(U)相比,除1% 3,4－二甲基吡唑磷酸盐(DMPP)+U处理 NH₃挥发增加了25.8%外,其他缓／控释尿素肥料处理对NH₃有明显的减排效果.树脂包膜尿素(PCU)对NH₃减排效果最明显,为73.4%,硫包膜尿素(SCU)为72.2%,0.5% N-丁基硫代磷酰三胺(NBPT)+1% DMPP+U为71.9%,1% 氢醌(HQ)+3% 双氰胺(DCD)+U为46.9%,0.5% NBPT+U为43.2%,1% HQ+U为40.2%,3% DCD+U为25.5%, 1% DMPP均与施用普通大颗粒尿素差异显著;所有缓／控释尿素处理与对照相比均可显著减少N₂O排放.1% DMPP+U对N₂O减排效果最明显,为74.9%,PCU为62.1%,1% HQ+3% DCD+U为54.7%,0.5% NBPT+1% DMPP+U为42.2%,3% DCD+U为35.9%,1% HQ+U为28.9%,0.5% NBPT+U为17.7%,SCU为14.5%,均与施用普通大颗粒尿素差异显著.比较0.5% NBPT+1% DMPP+U、SCU、PCU对NH₃和N₂O减排的综合效果,3种肥料作用相近,且均明显优于其他处理,但包膜材料的成本较抑制剂高数倍.因此,同时添加脲酶和硝化抑制剂的缓释尿素是减少水田氮素损失及环境污染的首选氮肥.     

Induction and persistence of pituitary and ovarian activity in the out-of-season lactating dairy goat after a treatment combining a skeleton photoperiod, melatonin and the male effect

Thirty-two out-of-season Saanen dairy goats were involved in a 2 X 2 factorial experiment using (1) extra-light treatment (equivalent to long days) from 18 January to 19 March, at the end of gestation and the onset of lactation and (2) daily melatonin injections (equivalent to short days) from 20 March to 30 June. Hence, there were 4 groups of 8 goats each: CC (control-control), EC (extra-light-control), CM (control-melatonin) and EM (extra-light-melatonin). In each group teasers (males and androgenized females) were introduced on 30 May. Serial blood samples were taken for measurement of LH pulsatility on 30 April and 30 May. Ovarian activity was followed by plasma progesterone assay and laparoscopy. Oestrous behaviour was checked daily from 30 May to 15 July. The number of LH pulses was not modified by the treatments (extra light or melatonin). Melatonin treatment increased the basal concentration of LH (Groups CC + EC = 0.30 ng/ml; Groups CM + EM = 0.38 ng/ml; P less than 0.02) and the amplitude of pulses (Groups CC + EC = 1.24; Groups CM + EM = 2.44 ng/ml; P less than 0.02); the highest amplitude was observed for females in Group EM. Melatonin-treated females ovulated earlier after introduction of teasers than did untreated goats (Groups CM + EM = 2.3 days; Groups CC + EC = 6.1 days; P less than 0.001), but treatments did not modify ovulation rate (mean 2.1) or percentage of goats experiencing a short luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)     

稳定性氮肥配合秸秆还田对水稻产量及N2O和CH4排放的影响

以中国科学院辽宁沈阳农田生态系统国家野外科学观测研究站连续两年的试验平台为依托,以潮棕壤为供试土壤,开展了稳定性氮肥配合秸秆还田对水稻产量及N₂O和CH₄排放的影响研究,设置对照(CK)、尿素(U)、尿素+脲酶抑制剂+硝化抑制剂(U+I)、秸秆还田(S)、秸秆还田+尿素(S+U)、秸秆还田+尿素+脲酶抑制剂+硝化抑制剂(S+U+I)6个处理.结果表明: 与CK相比,尿素显著提高了水稻产量、N₂O和CH₄累积排放及全球增温潜势.硝化抑制剂和脲酶抑制剂与尿素配施可显著减缓N₂O的累积排放.秸秆还田显著增加了N₂O和CH₄累积排放、全球增温潜势和温室气体排放强度.S+U+I处理水稻产量最高,但温室气体排放强度也显著高于其他处理;U+I处理产量略低于S+U+I,但温室气体排放强度最小.秸秆单独还田处理作物产量与对照相比无显著差异.在东北潮棕壤发育的水田中,S+U+I和U+I是相对较优的施肥模式.     

稳定性氮肥配合秸秆还田对水稻产量及N2O和CH4排放的影响

以中国科学院辽宁沈阳农田生态系统国家野外科学观测研究站连续两年的试验平台为依托,以潮棕壤为供试土壤,开展了稳定性氮肥配合秸秆还田对水稻产量及N₂O和CH₄排放的影响研究,设置对照(CK)、尿素(U)、尿素+脲酶抑制剂+硝化抑制剂(U+I)、秸秆还田(S)、秸秆还田+尿素(S+U)、秸秆还田+尿素+脲酶抑制剂+硝化抑制剂(S+U+I)6个处理.结果表明: 与CK相比,尿素显著提高了水稻产量、N₂O和CH₄累积排放及全球增温潜势.硝化抑制剂和脲酶抑制剂与尿素配施可显著减缓N₂O的累积排放.秸秆还田显著增加了N₂O和CH₄累积排放、全球增温潜势和温室气体排放强度.S+U+I处理水稻产量最高,但温室气体排放强度也显著高于其他处理;U+I处理产量略低于S+U+I,但温室气体排放强度最小.秸秆单独还田处理作物产量与对照相比无显著差异.在东北潮棕壤发育的水田中,S+U+I和U+I是相对较优的施肥模式.     

Effects of exogenous fibrolytic enzymes on ruminal fermentation and digestibility of total mixed rations fed to lambs

This experiment was designed to study effects of exogenous fibrolytic enzymes on digestibility and ruminal fermentation of total mixed rations (TMR) with different forage:concentrate (F:C) ratios. The experimental design was a 6×6 Latin square with six ruminally cannulated Ramboulliet lambs (58 ± 7.4 kg body weight) used in a 3×2 factorial arrangement of treatments using three forage:concentrate (F:C) ratios (400:600, 500:500, 600:400 kg/kg) and two (0 or 2 g) levels of fibrolytic enzymes/kg TMR dry matter (DM). Exogenous fibrolytic enzymes increased the soluble fraction of DM (P<0.01) and ruminal in situ disappearance rate of DM and neutral detergent fibre (aNDF; P<0.001). However, there were no differences among treatments in DM and aNDF in vivo digestibility due to enzyme addition to the diet. Feed intake and N balance were also not affected by enzymes, and ruminal fermentation patterns were unchanged. Exogenous fibrolytic enzymes improved ruminal disappearance rates of DM and aNDF, but had no impact on lamb performance or ruminal fermentation.     

控释肥及其与尿素配合施用对水稻生长期N2O排放的影响

通过田间试验,采用静态箱法研究相同施氮量条件下,施用尿素、控释肥及尿素与控释肥配施(尿素与控释肥以3∶7配合施用)对稻田N₂O排放的影响.结果表明：与单施尿素处理相比,配施处理和控释肥处理水稻生长期N₂O排放量分别减少40.4%和59.6%（P<0.05）,其中烤田期分别减少65.1%和83.9%;与配施处理相比,施用控释肥处理N₂O排放量略微减少（P>0.05）,其中烤田期减少53.9%.施用控释肥可增加水稻产量,与尿素处理相比,施用控释肥和配施处理水稻产量分别增加7.8%和9.8%（P>0.05）.施用控释肥使土壤无机氮峰值出现时间延后,烤田期N₂O排放减少.水稻生长期N₂O排放通量与土壤氧化还原电位（Eh）和土壤温度均无明显相关性（P>0.05）.     

Simultaneous inclusion of sorghum and cottonseed meal or millet in broiler diets: effects on performance and nutrient digestibility

Two experiments were conducted to investigate the use of sorghum, cottonseed meal and millet in broiler diets and their interaction when they are used simultaneously. In Experiment 1, a corn-soybean meal control diet was compared with eight experimental treatments based on low tannin sorghum (S30, S45 and S60), cottonseed meal (CM15, CM40) or both ingredients included in the same diet (S30/CM40, S45/CM25 and S60CM15). Results showed that BW gain was not affected by the inclusion of sorghum or cottonseed meal. However, feed intake tended to be affected by the cereal type with the highest values with sorghum-based diets. Feed conversion ratio increased (P<0.001) with sorghum-based diets compared with the control diet, whereas a combination of cottonseed meal and sorghum in the same diet did not affect the feed conversion ratio. Significant differences (P<0.001) were observed in apparent ileal digestibility (%) of protein and energy with the cottonseed meal and sorghum/cottonseed meal-based diets having lower protein and energy digestibility compared with corn-based diets. In Experiment 2, a control diet was compared with six diets in which corn was substituted at 60%, 80% or 100% by either sorghum or millet and other three diets with simultaneous inclusion of these two ingredients (S30/M30, S40/M40, S50/M50). Single or combined inclusion of sorghum and millet resulted in similar feed intake and growth performance as the control diet. Apparent ileal digestibility of protein and energy was higher with millet-based diets (P<0.001). Total tract digestibility of protein in sorghum and millet-based diets tended to decrease linearly with the increasing level of substitution. Sorghum-based diets resulted in lower total tract digestibility of fat compared with millet and sorghum/millet-based diets (P<0.001). Higher total tract digestibility of starch were obtained with the control diet and millet-based diets compared with the sorghum-based treatments. Results of the two experiments suggest that broiler growth performance was not affected by the dietary level of sorghum, millet or cottonseed meal. Nutrient digestion can, however, be affected by these feed ingredients.     

Effects of long period feeding pistachio by-product silage on chewing activity,nutrient digestibility and ruminal fermentation parameters of Holstein male calves

The objective of this study was to determine the effects of pistachio by-product silage (PBPS) as a partial replacement for corn silage (CS) on chewing activity, nutrients digestibility and ruminal fermentation parameters in Holstein male calves over a 6-month assay. For this purpose, 24 Holstein male calves (4 to 5 months of age and 155.6±13.5 kg BW) were randomly assigned to one of the four dietary treatments (n=6). In these treatments, CS was substituted with different levels of PBPS (0%, 6%, 12% and 18% of dry matter (DM)). Nutrient digestibility was measured at the end of the experimental period (days 168 to 170). Ruminal fermentation parameters were determined on days 90 and 180 and chewing activity was determined on days 15 of the 3^rd and 6^th month of the experiment. Results showed that calves fed rations containing 6% PBPS spent more time ruminating (P<0.05) than the control group on the 3^rd and 6^th months. Feeding PBPS was found to have no effects on DM, organic matter (OM), ether extract or ash digestibility, but apparent digestibility of CP, NDF_om and ADF_om linearly decreased (P<0.01) with increasing substitutions. On days 90 and 180, ruminal concentrations of volatile fatty acids and NH₃–N linearly decreased (P<0.01) with increasing levels of PBPS in the diets; however, ruminal pH and molar proportions of acetate, propionate and butyrate were similar across the treatments. It was concluded that partial substitution of CS with PBPS (6% or 12%) would have no adverse effects on nutrient digestibility, total chewing activity and ruminal fermentation parameters.     

The partial replacement of soyabean meal and rapeseed meal with feed grade urea or a slow-release urea and its effect on the performance, metabolism and digestibility in dairy cows

The objectives of the study were to determine the effect of the partial replacement of soyabean meal and rapeseed meal with feed grade urea or a slow-release urea on the performance, metabolism and whole-tract digestibility in mid-lactation dairy cows. Forty-two Holstein–Friesian dairy cows were allocated to one of three dietary treatments in each of three periods of 5 weeks duration in a Latin square design. Control (C) cows were offered a total mixed ration based on grass and maize silages and straight feeds that included 93 g/kg dry matter (DM) soyabean meal and 61 g/kg DM rapeseed meal. Cows that received either of the other two treatments were offered the same basal ration with the replacement of 28 g/kg DM soyabean and 19 g/kg DM rapeseed meal with either 5 g/kg DM feed grade urea (U) or 5.5 g/kg DM of the slow-release urea (S; Optigen^R; Alltech Inc., Kentucky, USA), with the content of maize silage increasing. There was no effect (P > 0.05) of dietary treatment on DM intake, which averaged 22.5 kg/day. Similarly, there was no effect (P > 0.05) of treatment on daily milk or milk fat yield but there was a trend (P = 0.09) for cows offered either of the diets containing urea to have a higher milk fat content (average of 40.1 g/kg for U and S v. 38.9 g/kg for C). Milk true protein concentration and yield were not affected by treatment (P > 0.05). Milk yield from forage and N efficiency (g milk N output/g N intake) were highest (P < 0.01) in cows when offered S and lowest in C, with cows receiving U having intermediate values. Cows offered S also tended to have the highest live weight gain (0.38 kg/day) followed by U (0.23 kg/day) and C (0.01 kg/day; P = 0.07). Plasma urea concentrations were higher (P < 0.05) at 2 and 4 h post feeding in cows when offered U and lowest in C, with animals receiving S having intermediate values. There was no effect (P > 0.05) of treatment on whole-tract digestibility. In conclusion, the partial replacement of soyabean meal and rapeseed meal with feed grade urea or a slow-release urea can be achieved without affecting milk performance or diet digestibility, with the efficiency of conversion of dietary N into milk being improved when the slow-release urea was fed.