Effective Rumen Degradable Protein Research Articles

Relationships between dietary factors and nitrogen partitioning to milk and urine in temperate grazing dairy cattle

ABSTRACT Urinary nitrogen (UN) excretion and milk production traits of 35 groups of 15 grazing cows each were measured over two years. Urine volume and N concentration were measured with urine sensors and daily UN excretion was calculated for four consecutive days. Milk yield, composition and cow liveweight (LW) were used to estimate daily dry matter intakes (DMI) based on back-calculated animal energy requirements and feed metabolisable energy (ME). Different N fractions in the diet were estimated using laboratory data and protein digestion equations. Mean estimates of N intake and UN excretion were 460 and 227 g N/d, respectively. Urinary-N represented 52% of the N consumed, which aligns with indoor N balance studies. Urinary N excretion was weakly correlated (r = 0.29) with dietary N intake, but moderately correlated (r = 0.63–0.67) with diet N concentration, diet N:ME ratio, and diet effective rumen degradable protein (ERDP). The ERDP balance had moderate to strong correlations with N utilisation efficiency (r = −0.89) and the UN expressed relative to N intake (r = 0.59) and N in milk (r = 0.78). These relationships illustrate the potential of urine sensors and energy-based estimations of intake to assess the influence of dietary management strategies to mitigate UN excretion from grazing animals.

Effect of processing with ozone on in vitro and in situ ruminal degradability and intestinal digestibility of feather meal protein

This study aimed to investigate the effect of processing feather meal (FM) with ozone (O3) gas on nutrient content, ruminal degradability, and intestinal digestion of crude protein (CP) using in vitro and in situ techniques. Experimental treatments were designed as control (not-processed), O3-processed FM for 12 h (h; treat 1), O3-processed FM for 24 h (treat 2), and O3-processed FM for 48 h (treat 3). Five Ghezel sheep equipped with ruminal cannulas were used to measure the nutrient degradability and to obtain ruminal fluid for in vitro gas production. Processing with O3 gas significantly decreased dry matter (DM), ether extract (EE), and Ash content of the FM compared to the control (P < 0.05). Processing FM by O3 increased the volume of in vitro gas production (P < 0.05). The soluble and potentially degradable fractions of the DM and CP showed a significant increase with increasing processing time (P < 0.05). Processing with O3 gas increased quickly degradable protein (QDP), rumen degradable protein (RDP), effective rumen degradable protein (ERDP), and digestible undegradable protein (DUP) content as a proportion of feather meal CP. Still, undegradable dietary protein (UDP) decreased significantly. Intestinal digestibility of rumen undegradable protein (RUP) and Metabolize Protein (MP) content of the FM was also significantly increased with increased processing time and the highest values were achieved after 48 h of processing (P˂0.05). According to the results of this experiment, it can be concluded that processing FM using O3 for 48 h increases its nutritional value in ruminant nutrition.

Canola as a potential forage.

The nutritive quality of four cultivars of canola forage (Brassica napus L.), Orient, Midas, Global, and Hybrid (Cobra × Regent), which were harvested in the early-spring period, were compared with green-winter barley (GWB) in terms of their yields, chemical composition, in vitro gas production variables, in situ crude protein (CP) degradation, and predicted dry matter intake (PDMI). Data were statistically analyzed using a completely randomized design with four replications and three samples per replication. The study was based on a randomized complete block design, and data were analyzed using SAS, general linear model procedure for normal distribution. The canola dry matter (DM) yield was highest in Orient cultivar and lowest in Midas (P < 0.05). Organic matter (OM), CP, neutral detergent fiber (NDF), and lignin(sa) concentration of the four cultivars ranged from 862 to 865, 218 to 247, 295 to 340, and 35 to 53 g/kg DM, respectively. The estimated OM disappearance (OMD), effective degradability of CP, effective rumen degradable protein (ERDP), digestible undegradable protein, and metabolizable protein (MP) of the forages were from 636 to 671 g/kg, 878 to 910, 172 to 193, 1.9 to 3.4, and 112 to 126 g/kg DM, respectively. Compared to Global and Hybrid cultivars, Orient and Midas contained higher CP, OMD, ERDP, MP concentration, and PDMI, but lower NDF, acid detergent fiber (ADF), and lignin(sa) concentrations (P < 0.05). The level of glucosinolates in the forages ranged from 0.38 to 1.51 µmol/g DM, which is below the detrimental level for ruminants. Compared to winter canola cultivars, GWB had higher DM yield (P < 0.003), NDF, lignin(sa), PDMI (P < 0.01), and digestible undegradable protein (P < 0.04), but had lower OMD (P < 0.03), ERDP (P = 0.01), and MP (P < 0.009). Based on the obtained results, the variation in the nutritive quality among the canola cultivars is relatively small, and the Orient cultivar, which is most comparable to GWB, was judged to be nutritionally the best among the cultivars.

Enteric Methane Production Potential of Non-Leguminous Forages

The present study was undertaken to assess the methane production potential of multi-cut nonleguminous forages viz. rye grass and guinea grass harvested through four cuts using in sacco degradation and in vitro gas production (IVGP) procedures. Results revealed that irrespective of cuts, rye grass had higher (P<0.01) rapidly soluble fraction than guinea grass, with a reverse trend (P<0.01) for insoluble but potentially degradable fraction and rumen undegradable fraction (UDF). The rate for the latter was highest (P<0.01) for the younger grasses (I cut) and lowest (P<0.01) for the III cut. The rumen UDF of DM increased (P<0.01) with advancement of cuts. Rye grass had higher (P<0.01) effective rumen degradable protein (ERDP) and lower (P<0.01) rumen undegradable protein (RUDP) than that in guinea grass. The RUDP as % of CP was higher (P<0.01) in guinea grass than that in rye grass. Almost similar trend (P<0.01) was observed in the digestion kinetic parameters for NDF degradability. The IVGP data showed that irrespective of cuts, rye grass produced higher (P<0.01) net gas, lower (P<0.01) methane resulting in higher (P<0.01) partitioning factor. The ME (P<0.01) was higher in rye grass. The young forage from I and II cuts showed higher (P<0.01) net gas production as compared to III and IV cuts. The methane production increased (P<0.01), while digestibility of OM and NDF decreased (P<0.01) with the increase in number of cuts. The availability of ME varied from 6.78 (IV cut) to 8.66 (II cut). Rye grass produced higher (P<0.01) TVFA, acetate, propionate and butyrate than that produced by guinea grass. It was concluded that irrespective of cuts, rye grass had higher nutritional worth with lower methane production as compared to that produced by guinea grass. The methane production increased, while the digestibility decreased with the increase in number of cuts.

Short communication: Relationship between the efficiency of utilization of feed nitrogen and 15N enrichment in casein from lactating dairy cows

The objective of the present study was to evaluate the relationship between the efficiency of conversion of feed N into milk N [N-use efficiency (NUE)] and 15N enrichment of milk casein from lactating cows fed corn silage-based diets. Samples of feeds and milk were obtained from 3 experiments with lactating dairy cows. All diets were based on corn silage and were designed to evaluate the effects of (1) diets with different ratios of effective rumen-degradable protein to fermentable metabolizable energy (experiment 1), (2) different proportions of quickly and slowly rumen-degradable protein (experiment 2), and (3) synchronizing the availability of fermentable metabolizable energy and effective rumen-degradable protein in the rumen (experiment 3). Although no significant effect of diet on casein δ15N values was detected, casein was more enriched than the diet in each of the experiments. Nitrogen-use efficiency was negatively related to adjusted Δ15N (casein δ15N − diet δ15N) for experiments 1 and 2 individually and when combining data from all 3 experiments. The relatively low values for Δ15N suggest that these productive animals were using dietary N efficiently, with a high proportion of N going to milk protein and less to urea. The weak, although significant, relationship between NUE and adjusted Δ15N, is consistent with relatively little variation in hepatic deamination and transamination, with variation in rumen efficiency having the predominant effect on NUE. The present study confirms the lower 15N enrichment in protein when NUE is high and the potential to use N-isotope fractionation as a marker of NUE.

Ruminal protein degradability of a range of tropical pastures

The rumen degradability parameters of the diet selected by two to four oesophageal-fistulated Brahman steers grazing a range of tropical pastures were determined by incubation of extrusa in nylon bags suspended in the rumen of rumen-fistulated (RF) Brahman steers. The effective protein degradability (Edg) was determined by measuring the rate of disappearance of neutral detergent insoluble nitrogen (NDIN) less acid detergent insoluble nitrogen (ADIN) in the incubated extrusa. Six to eight RF steers also grazed each of the pastures along with the oesophageal-fistulated steers, to allow determination of key rumen parameters and rumen particulate matter fractional outflow rates (FOR). The seven pastures studied included: native tropical grass (C4) pasture (major species Heteropogon contortus and Bothriochloa bladhii), studied in the early wet (NPEW), the wet/dry transition (NPT) and the dry (NPD) seasons; introduced tropical grass (C4) pasture (Bothriochloa insculpta), studied in the mid wet season (BB); the introduced tropical legumes (C3), Lablab purpureus (LL) and Clitoria ternatea (BP); and the temperate grass (C3) pasture, ryegrass (Lolium multiflorum, RG). Using the measured particle FOR values in calculations, the Edg estimates were very high for both C4 and C3 species: 0.82–0.91 and 0.95–0.98 g/g crude protein (CP), respectively. Substitution of an assumed FOR (kp = 0.02/h) for the measured values for each pasture type did not markedly affect estimates of Edg. However, C4 tropical grasses had much lower effective rumen degradable protein (ERDP) fractions (23–66 g/kg DM) than the C3 pasture species RG and LL (356 and 243 g/kg DM, respectively). This was associated with a lower potential degradability and degradation rate of organic matter (OM) in sacco, lower in vitro organic matter digestibility (IVOMD) and CP concentrations in the extrusa, and lower ammonia-N and branched-chain fatty acid concentrations in rumen fluid for the tropical grasses. As tropical grass pastures senesced, there was a decline in Edg, the ERDP and rumen undegradable protein (UDP) fractions, the potential degradability and degradation rate of OM and the IVOMD. These results provide useful data for estimating protein supply to cattle grazing tropical pastures.

Nutritive value of forage species grown in the warm temperate climate of Australia for dairy cows: Herbs and grain crops

The objective of this study was to quantify the nutritive characteristics of 6 grain crops and 4 herb forages over 4 seasons, when all species were grown at the same site, under the same climatic and edaphic conditions, and with soil moisture and nutrient availability being non-limiting to growth. The forages grown were maize ( Zea mays), sorghum ( Sorghum bicolor), millet ( Pennisetum americana), wheat ( Triticum aestivum), triticale ( Triticum × secale), oats ( Avena sativa), fodder radish ( Raphanu sativa), rape ( Brassica rapa), chicory ( Cachorium intybus) and plantain ( Plantago lanceolata). The in sacco degradation characteristics of organic matter (OM) and crude protein of herbages were measured in the rumen of cannulated sheep in order to calculate the availability of effective rumen degradable protein (ERDP), rumen by pass protein, metabolisable protein (MP) and the synchrony index ( I s), which describes the efficiency of utilization of degradable nitrogen (N) and OM for microbial protein synthesis (MPS) in the rumen. In this study, all grain crops except maize had a ERDP/fermentable metabolizable energy (FME) ratio varying from 14 for millet to 23 for wheat, well above the ratio of 11 required for optimum MPS in the rumen of dairy cows. In contrast, maize had the lowest ERDP/FME ratio of 3, indicating that ERDP would be limiting MPS in the rumen. The availability of MP varied from 58 g/kg DM in maize to 153 g/kg DM in wheat and all forage species except maize were be able to meet the MP requirement of high-producing dairy cows (30 L/milk/day) provided they were able to consume 11 to13 kg DM/cow/day of the forage. The availability of MP from herbs varied from 95 g/kg DM in fodder radish to 163 g/kg DM in plantain, which would be sufficient for high-producing cows, however, most dairy cows could not consume sufficient forage to achieve these high levels of production due to very high nitrate content in rape (mean of 11.1 g/kg DM) and fodder radish (mean of 8 g/kg DM).

Nutritive value of forage species grown in the warm temperate climate of Australia for dairy cows: Grasses and legumes

Abstract The objective of this study was to quantify the differences in the nutritive value over 4 seasons, of 7 C 3 temperate grasses, 2 C 4 tropical grasses and 11 clover species used as forages for dairy cows. The nutritive value was assessed in terms of nutrient content and the availability of effective rumen degradable protein, rumen by pass protein, metabolisable protein (MP) and fermentable metabolisable energy. All species were grown in plots as monocultures under conditions of non limiting nutrients and moisture and harvested by mechanical means. All species had a high crude protein content and this resulted in a high effective rumen degradable protein: fermentable metabolisable energy ratio varying from 15, for cowpeas ( Vigna unguiculata ) to 29 for birdsfoot clover ( Lotus corniculatus ), and all were above the ratio of 11 required for optimal microbial protein synthesis in the rumen of dairy cows. The calculated availability of MP varied from 105 g/kg dry matter (DM) for cowpeas to 173 g/kg DM for berseem clover ( Trifolium alexandrinum ) indicating that all forages would be able to meet the requirements of dairy cows producing up to 30 L/milk/day, provided they were able to consume over 19 kg DM of forage/cow/day. Grasses had much higher hemicellulose (neutral detergent fibre minus acid detergent fibre) content than legumes. Kikuyu ( Pennisetum clandestinum ), a C 4 grass, had a higher proportion of hemicellulose content than the C 3 temperate grasses. Perennial ryegrass ( Lolium perenne ) and kikuyu had a similar metabolisable energy (ME) density (9.9 MJ/kg DM) in summer. The mean ME density of perennial ryegrass, prairie grass ( Bromus wildinowii ) and short rotation ryegrass ( Lolium multiflorum ) winter was similar at 10.6 MJ/kg DM and slightly higher than cocksfoot ( Dactylus glomeratus ), phalaris ( Phalaris tuberosa ) and fescue ( Fescue arundunicea ) which had a mean ME density of 10 MJ/kg DM. All forages grown were able to satisfy MP and ME requirements of dairy cows producing up to 30 L milk/cow/day, provided they were able to consume sufficient forage to achieve this level of production.

Evaluation of protein degradation characteristics and metabolisable protein of elephant grass ( Pennisetum purpureum) and locally available protein supplements

Degradation characteristics of crude protein (CP) and metabolisable protein (MP) of feeds for early-weaned, growing and finishing beef bulls were evaluated in three experiments. Feeds in experiment 1 were fresh elephant grass (FEG) and molasses supplemented with sweet potato vines (SPV) in diet 1, supplemental (GCM) compounded from gliricidia, cottonseed cake (CSC), maize bran and NaCl in diet 2 and a commercial concentrate (CC) in diet 3. Feeds in experiment 2 were basal maize stover mixed with molasses (MSM) and FEG supplemented with SPV in diet 1, GCM in diet 2 and CC in diet 3. In experiment 3, MSM and FEG were supplemented with compounded supplemental protein feeds with varying levels of gliricidia inclusion. Supplemental (GM) containing gliricidia, maize bran and NaCl were used in diet 1, GCM in diet 2 and supplemental (CM) containing CSC, maize bran and NaCl in diet 3. Degradabilities of experimental feeds were measured at 0, 6, 12, 24, 48, 72, 96, and 120 h by the nylon bag technique using two rumen fistulated steers (300±10 kg). Effective CP degradabilities of FEG in the three experiments varied ( P<0.05) with the supplements. In experiment 1, effective CP degradabilities of the supplements varied ( P<0.05) from 668.3 g kg −1 CP in CC to 722.1 g kg −1 CP in SPV and 743.7 g kg −1 CP in GCM. Effective rumen degradable protein (ERDP), digestible udegradable protein (DUP) and MP varied ( P<0.05) among the supplements. In experiment 2, effective CP degradabilities of the supplements did not vary but ERDP varied ( P<0.05) from 83.7 g kg −1 CP in SPV to 116.6 g kg −1 CP in GCM and 123.8 g kg −1 CP in CC and MP followed similar trends. In experiment 3, effective CP degradabilities of the supplements decreased ( P<0.05) with increasing gliricidia inclusion. ERDP increased ( P<0.05) with lower gliricidia while DUP varied ( P<0.05) from 18.2 g kg −1 CP in CM to 23.6 g kg −1 CP in GCM and 36.6 g kg −1 CP in GM. These data have shown that the majority of locally available feeds evaluated in this study are not similar in CP degradation characteristics and MP but compounded GCM is more suitable in providing degradable and undegradable protein for beef bulls in Uganda.

Effect of the different ratios of effective rumen degradable protein to fermentable metabolizable energy on early lactating Holstein cow performances

The efficiency of dietary N by dairy cows is generally low, and in part, may be related to an impaired utilization of N in the rumen. A major determinant of microbial protein synthesis is the availability of energy-yielding substrates (Castillo et al., 2001). It seems likely that low ratios of effective rumen degradable protein (ERDP) to fermentable metabolisable energy (FME) will restrict microbial protein synthesis and dry matter intake and, consequently, lead to reduced milk yield (Cabrita et al., 2003). Nitrogen excretion in faeces and urine accounts for a high proportion of N intake, which may be more than 70% of the daily N consumption. Environmental pollution from N as ammonia and nitrates is regarded as a major potential problem world wide. Nutritional manipulations might be a way of significantly increasing N utilization and decreasing N pollution by dairy cows, and where as protein sources are expensive so, the cost of diet decrease (Castillo et al., 2001). The objective of this study was to examine the product and component of milk of dairy cows offered diets with different ratios of ERDP/FME.

Effect of undegradable protein supply on testicular size, spermiogram parameters and sexual behavior of mature Assaf rams

Eighteen mature Assaf rams were used to study the effect of undegradable protein (UDP) supply on testicular size, sperm production and quality, testosterone secretion and reproductive behavior. Animals were allocated to three groups of six animals each and fed during 10 weeks with different diets which were designed to supply approximately 0.5 MJ of metabolisable energy (ME)/kg LBW 0.75 and 9 g of effective rumen degradable protein (ERDP)/MJ of fermentable ME to all animals and to induce differences in rumen UDP intake (0.97, 1.72 and 3.08 g of UDP/kg LBW 0.75 for LP, MP and HP diets, respectively). Neither plasma testosterone concentration nor reproductive behavior parameters (number of services, number of mounts without ejaculation and reaction time to first mount) were affected ( P>0.05) by protein intake. Nevertheless, there were significant ( P<0.05) differences between diets in both testicular size and sperm production. Scrotal circumference was lower in LP compared to MP and HP groups, no significant differences being observed between these latter two groups at any time. In relation to sperm production, the lowest and the highest values were always observed in LP and HP groups, respectively. MP group showed intermediate values, significantly different from those of LP and HP groups on Week 5 and only from those of LP group on Week 9. The present results provide a better understanding of the effect of protein nutrition and suggest that UDP should be supplied to Assaf rams during the mating season to improve their reproductive performance.

Nitrogen supplementation of corn silages. 1. Effects on feed intake and milk production of dairy cows.

Feed intake and milk production responses to N supplementation of corn silage-based diets were measured in three 3 x 3 Latin square experiments. In each experiment, 9 Holstein cows received total mixed rations (TMR), based on corn silage. In Exp. 1, midlactation cows were used to study effects of diets with different ratios of effective rumen-degradable protein (ERDP; g) to fermentable metabolizable energy (FME; MJ), providing a large deficiency (RL), a slight deficiency (RM), and a slight excess (RH) in relation to the target level of 11 g of ERDP/MJ of FME, respectively, for lactating cows. Diets were formulated to be isoenergetic, and to satisfy the metabolizable protein requirements. In Exp. 2, early-lactation cows were used to evaluate effects of different proportions of quickly and slowly rumen-degradable protein (RDP), achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in the rumen. Midlactation cows received a diet containing, on a dry matter (DM) basis, 45% corn silage, 5% ryegrass hay, 35% energy-rich concentrate, and 15% protein-rich concentrate (crude protein: 38% of DM; urea: 2% of DM). The protein-rich concentrate was fed either once (D1) or twice (D2) per day before the meal, or included in the TMR (DU). Treatment RL led to lower DM intake and milk yield, but higher milk production efficiency; there were no significant differences between treatments RM and RH. There were no significant treatment effects on DM intake, milk yield, or milk composition in Exp. 2. Manipulating rumen synchrony by altering the timing of feeding affected milk yields, with D1 cows producing significantly less than D2 and DU cows, which were similar. The amount of ERDP in the diet should be matched to the amount of fermentable energy available to maximize intake, milk yields, and the conversion of feed N into milk protein. However, this study showed only small benefits to altering the diurnal pattern of supply of RDP and FME, and only with extreme feeding strategies that would not be used in practice. Urine volume increased in response to increased or unbalanced protein supply. Analysis of the allantoin:creatinine ratio in spot samples of urine was not useful in identifying predicted differences in microbial protein yield from the rumen.

Nitrogen Supplementation of Corn Silages. 2. Assessing Rumen Function Using Fatty Acid Profiles of Bovine Milk

The effects of N supplementation strategies on milk fatty acid profiles of dairy cows and their use as a noninvasive technique to diagnose rumen function, and to guide protein feeding decisions on-farm were evaluated in three experiments. Each experiment was designed according to three 3 x 3 Latin squares with 9 Holstein cows receiving total mixed rations based on corn silage. Experiment 1 was designed to study effects of diets with different ratios of effective rumen-degradable protein (ERDP; g) to fermentable metabolizable energy (FME; j) providing, respectively, a large deficiency, a slight deficiency, and a slight excess in relation to the target level of 11 g of ERDP/MJ FME for lactating cows. Experiment 2 evaluated effects of different proportions of quickly and slowly rumen-degradable protein achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea for U0, U5, and U10, respectively). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in rumen by offering the protein-rich concentrate once or twice per day before the meal (corn silage, ryegrass hay, and energy-rich concentrate), or included in the total mixed ration. Milk fatty acid profiles were significantly affected by dietary N and carbohydrate supply. Principal component factor analysis provided a reasonable description of the data, clearly discriminating between fatty acids that are synthesized by different metabolic pathways. Several sources/pathways were distinguished: de novo synthesis in the mammary gland (short- and medium-chain fatty acids), delta9-desaturase activity (monoenoic fatty acids), direct absorption from the blood stream (long-chain fatty acids), and de novo synthesis by the rumen microbial populations (odd-chain fatty acids). Discriminant canonical analysis showed that milk odd-chain fatty acids had a higher ability to discriminate between diets than even-chain fatty acids. The anteiso C15:0 increased in line with increasing sugar supply, and C17:0 appears to be a marker of protein deficiency. Additionally, iso C17:0 and anteiso C17:0 were associated with the NDF and CP contents of diets. The results suggests that milk odd-chain fatty acids have the potential to be used as a noninvasive technique to assess rumen function in terms of microbial populations, substrates and interactions.

Diet selection of sheep: sodium bicarbonate, but not the offering of hay, modifies the effect of urea on diet selection

AbstractThe hypotheses tested were that the expected preference of sheep for a food with adequate rumen degradable protein (RDP) supplemented with urea would be reduced both by the addition of a buffer (sodium bicarbonate (SB)) and by offering ad libitum access to hay. A control food (C), calculated to be adequate in its ratio of effective RDP to fermentable metabolizable energy (fME), was formulated. Other foods were made by adding 12·5 (U1) or 25 (U2) g urea per kg fresh matter (FM) to C and 20 g SB per kg FM to C, U1and U2. The acid buffering capacity (ABC) of each food was measured in vitro. The experiment consisted of two successive periods, each of 4 weeks. Ninety-eight female, Texel ✕ Greyface sheep were randomly allocated to 14 groups each with seven animals. Groups 1 to 6 were offered one of: C, U2, C + SB, U2+ SB, C with hay or U2with hay throughout the experiment. Groups 7 to 10 were offered the choices of C v. U1or C v. U2, either with or without hay in a change-over design; animals that received hay during period 1 (groups 8 and 10) did not do so during period 2 and vice versa (groups 7 and 9). Groups 11 to 14 (no. = 7) were offered the choices of C v. U1or C v. U2, either with or without SB supplemented to both foods, in a change-over design. Adding either urea, or SB, or both to C had no effects on intake or live-weight gain when offered alone. Both supplements significantly (P 0·001) increased the ABC of food C. Throughout the experiment hay consumption was very low (overall mean: 23 (s.e. 2·5) g hay per sheep day). Offering hay caused no change in the preference for the urea-supplemented foods. Sheep offered the choices C v. U1or C v. U2, with neither hay nor SB, selected 0.466 (s.e. 0·036) and 0.588 (s.e. 0·025) kg/kg total food intake (TFI) of U1and U2respectively. The proportions of the urea-supplemented foods were significantly reduced (P 0.01) by SB supplementation: to 0.348 (s.e.0·045) and 0·406 (s.e.0·059) kg/kg TFI of U1and U2respectively. The effect of SB addition on the diet selection of sheep could be due to its buffering properties. When SB is added to both foods the need for urea to be used as a buffer is reduced with a consequent decrease in the proportion selected as the urea-supplemented food. Effects of diet on buffering may override other diet selection objectives, such as the avoidance of an excess intake of RDP.

Ruminal peptide and soluble protein N concentrations in Iranian Baloochi lambs fed diets containing lucerne hay or silage

It is generally agreed that peptides accumulate in the rumen fluid after feeding. It has been also suggested that the production of peptides in the rumen was not altered by the protein supplements when diets provided similar effective rumen degradable protein (Mesgaran &amp; Moosavi, 1999). The objective of the present experiment was to investigate the effect of diets containing lucerne hay or silage treated by urea and formaldehyde on the ruminal peptide and soluble protein N concentrations in Iranian Baloochi lambs.

The effects of concentrate energy source on feed intake and rumen fermentation parameters of dairy cows offered a range of grass silages

The effects of concentrate energy source on feed intake and rumen fermentation parameters of lactating dairy cattle, offered one of three grass silages differing in fermentation and intake characteristics, were evaluated in a partially balanced changeover design experiment involving four rumen fistulated dairy cows. Three silages were harvested using different management practices prior to and at ensiling. Silages A and C and silage B were harvested from primary or secondary regrowths either untreated or treated with a bacterial inoculant. For silages A, B and C, dry matter (DM) concentrations were 334, 197 and 183 g/kg (S.E. 3.1), pH values 4.00, 4.79 and 4.80 (S.E. 0.042) and ammonia nitrogen (N) concentrations were 123, 319 and 295 g/kg total N (S.E. 20.0), respectively. Two concentrates were formulated to contain similar crude protein, effective rumen degradable protein, digestible undegradable protein and metabolisable energy concentrations but using different carbohydrate sources to achieve a wide range of starch concentrations. For the low and high starch concentrates starch concentrations were 17 and 304 g/kg DM and acid detergent fibre concentrations were 170 and 80 g/kg DM, respectively. The silages were offered ad libitum, supplemented with 10 kg fresh concentrate daily. For silages A, B and C, DM intakes were 10.9, 7.2 and 8.6 kg/day and concentrate energy sources did not alter ( P>0.05) intake. Increasing the level of starch in the concentrate decreased the molar concentration of acetate ( P<0.05) and tended to increase the molar concentration of propionate ( P<0.1). Silage type altered the molar concentration of acetate ( P<0.01) and the acetate:propionate ratio ( P<0.05). There were no silage type × concentrate interactions ( P>0.05) on silage intake or rumen fermentation parameters. It is concluded that when concentrate and silage form equal proportions of the diet, the composition of the silage has an over-riding influence on rumen fermentation parameters. Furthermore, the changes in milk fat concentration, observed in a concurrent production study, due to changes in silage and concentrate types can be accounted for by changes in the ratio of lipogenic to glucogenic precursors in the rumen fluid.

Diet selection of sheep: effects of adding urea to foods with different protein contents

AbstractTwo experiments were conducted in which growing sheep were given choices between foods differing in their contents of urea. The crude protein (CP) contents of both of the foods of the pair were also varied. The hypothesis tested was that the diets selected would be those that met the effective rumen degradable protein (eRDP) requirements of the animals and would avoid excess consumption of eRDP. Three basal foods, differing in CP were formulated. D was designed to be deficient in CP with 80 g CP and 58 g eRDP per kg DM; H was calculated to be adequate with 159 g CP and 114 g eRDP per kg DM; P had excess with 210 g CP and 148 g eRDP per kg DM. Other foods were made by adding 12·5 or 25 g urea per kg fresh matter to each of the three basal foods to make a further six foods. In both experiments Texel✕Greyface female sheep were used. In experiment 1, 34 sheep weighing 37·2 (s.d. 1·85) kg were randomly allocated to one of six groups and each group was offered a choice between a pair of foods. Groups 1 to 3 were offered pairs in the D series (Dv. D + 12·5 g urea per kg (no. = 6), Dv. D + 25 g urea per kg (no. = 6) and D + 12·5 g urea per kg v. D + 25 g urea per kg (no. = 5)). Groups 4 to 6 were offered the same pairs of foods but with H instead of D. In experiment 2, 96 sheep weighing 29·8 (s.d. 3·37) kg were randomly allocated to one of 12 groups. Groups 1 to 6 (no. = 6) were allocated a single food (D, D + 25 g, H, H + 25 g, P or P + 25 g urea per kg) throughout the experiment. Groups 7 to 12 were given a choice (no. = 10) between two foods. One food of the pair was the basal D, H or P. The other food was the same basal food supplemented with either 12·5 or 25 g urea per kg. On the single foods adding urea to D resulted in an increase in food intake and live-weight gain suggesting that D was deficient in eRDP. Adding urea to either H or P had no beneficial effects on intake or live-weight gain. This suggests that both contained sufficient eRDP in relation to energy. Across all choice treatments in both experiments there was a highly significant preference (P&lt; 0·01) for the food with the higher urea content. In experiment 1 0·62 (s.e. 0·04) of the diet selected was the food with the higher urea content. In experiment 2 the figure was 0·64 (s.e.0·03). The general preference for the food with the higher urea content was unaffected by the CP contents of the foods used. The results do not support the hypothesis that sheep will avoid excess eRDP when given a choice and suggest that eRDP may not be a relevant dimension in diet selection in the conditions of these experiments.

Ruminal peptide-N concentrations in Iranian Balochi lambs fed diets containing lucerne hay or silage

Peptides are intermediates in the conversion of ingested protein to ammonia in the rumen and their accumulation depends upon the nature of diet (Mesgaran &amp; Parker, 1995). Transient accumulation of peptides occurs after feeding and then their concentrations declines. In addition, it suggests that the production of peptides in the rumen was not altered by the protein supplements when diets provided similar effective rumen degradable protein (ERDP)(Mesgaran &amp; Moosavi, 1999). The objective of the present experiment was to investigate the effect of diets, with similar ERDP, containing lucerne hay or silage on the ruminal peptide-N concentrations.

Effects of the ratio of effective rumen degradable protein to fermentable metabolizable energy on voluntary intake and milk yields of dairy cows

Diets with low ratios of effective rumen degradable protein (ERDP) to fermentable metabolizable energy (FME) are often offered to dairy cows in Portugal, because they are based on maize silage and protein sources are very expensive. It seems likely that this will restrict microbial protein synthesis and voluntary intake and, consequently, lead to reduced milk yields. The objective of this study was to examine the production response of dairy cows offered diets differing in ERDP/FME ratio.

On the diet selection of sheep: sodium bicarbonate modifies the effect of urea on diet selection

It was hypothesised that both inadequate and abundant levels of effective rumen degradable protein (eRDP) would be avoided by ruminants given a choice of foods (Tolkamp et al, 1998). However, we have found that sheep do not appear to avoid the excess consumption of eRDP expected when they were offered a choice of foods that differed in eRDP content through the addition of urea to one of the foods (James et al., 2001). A possible reason could be due to the fact that the foods offered had low fibre contents. The sheep may have selected for the urea supplemented food in an attempt to buffer the rumen. The buffering ability of the urea could help to minimise the disruption of the rumen such as a fall in pH caused by the low fibre foods. The objective of this experiment was to test the hypothesis that the preference for the urea supplemented food would be reduced by the addition of sodium bicarbonate (buffer).