Digestibility Of Undegraded Protein Research Articles

An examination of the effect of concentrate energy source and changes in eRDP:DUP ratio on milk production of dairy cows offered grass silages differing in digestibility and intake characteristics

Results from a previous study at this Institute indicated that concentrate energy source did not alter silage intake or animal performance of lactating dairy cows offered a range of grass silages of similar digestibility but differing in intake characteristics. Digestibility is probably the single most important variable affecting animal performance from grass silage. The present study was undertaken to examine the effects of concentrate energy source and effective rumen degradable protein (eRDP):digestible undegradable protein (DUP) ratio in the concentrate on the silage intake of, and animal performance from, lactating dairy cows offered a diverse range of grass silages differing in digestibility and intake characteristics.

The effects of concentrate energy source on energy utilisation by lactating dairy cows offered a range of grass silages

Replacement of high starch with high digestible fibre ingredients in the concentrate has resulted in inconsistent effects on silage intake and milk yield and composition of lactating dairy cattle. These differences in animal performance may reflect effects of concentrate energy source on energy utilisation. The present study was undertaken to examine the effect of concentrate energy source on energy utilisation in lactating dairy cows offered a diverse range of grass silages.Three silages were harvested from perennial ryegrass swards after 39 day regrowth intervals. Silages A and C were produced from primary regrowths and Silage B from a secondary regrowth. Silages A, B and C were ensiled after 24, 0 and 0 h wilting intervals, treated with an inoculant, untreated or an inoculant respectively. Concentrates containing starch concentrations of 50, 209 and 385 g/kg DM, were prepared using barley, wheat, maize gluten, sugar beet pulp and citrus pulp as energy sources. The concentrates were formulated to contain similar concentrations of crude protein, effective rumen degradable protein, digestible undegradable protein, metabolisable energy and fermentable metabolisable energy and were offered at 10 kg/head/d in four equal feeds accounting for 0.57 of DM intake. The diets (3 silages x 3 concentrates) were offered to 18 lactating dairy cows, in a completely randomised experiment, for a minimum period of 28 days prior to the main recording period. Prior to entering open circuit respiration chambers, described by Gordon et al. (1995), cows were housed in individual stalls during a 6 day diet digestibility and nitrogen utilisation study.

Effect of various treatments of urea-treated whole crop wheat on forage intake and milk production by dairy cows

Previous experiments in this series showed that a major cause of the disappointing milk yield response to the partial replacement of grass silage by urea-treated whole crop wheat (WCW) was the low digestibility of the WCW. The present experiment was designed to investigate the effectiveness of various treatments in improving milk production from such diets. Treatments examined included pre-treatment of the WCW to improve digestibility, replacing part of the concentrates by molasses or ground wheat to increase rumen ammonia utilisation, and increasing the digestible undegradable protein (DUP) content of the concentrates.

Effect of increasing digestible undegraded protein supply to dairy cows in late gestation on the yield and composition of milk during the subsequent lactation

AbstractEffects of feeding a protein supplement to dairy cows during the dry period on performance during the following lactation were investigated in two experiments. Holstein-Friesian cows were paired towards the end of lactation, and, after drying off, one of each pair received a typical dry cow management regime of ad libitum grass silage (experiment 1), or a mix of grass silage and distillers' grains or pressed beet pulp (experiment 2). The other cows were offered restricted access to the same basal diet, together with ad libitum access to barley straw and 0·5 kg/day high protein maize gluten meal. During the following lactation, animals from both groups were treated without reference to dry period treatment, and were offered equal access to the same lactation diet. Data were analysed by analysis of variance of experiment means and by parallel curve analysis using sample means. In experiment 1, milk yields were similar (27·2 v. 27·9 (s.e.d. 2·12) kg/day for control and supplemented animals respectively) but milk protein yields, and hence concentrations, were significantly higher (P < 0·001) from supplemented animals (28·9 v. 31·8 (s.e.d. 0·58) g/kg). In experiment 2, milk yields were significantly higher (P < 0·001) from supplemented animals (mean 33·3 v. 35·4 (s.e.d. 1·66) kg/day; however, milk protein yields were also significantly increased (P < 0·001) and the change in milk protein concentration was small. No difference in dry-matter intake was recorded in a subset of animals during early lactation in experiment 2. It is hypothesized that the maternal labile body protein pool was maintained or replenished during the dry period by the provision of the protein supplement, and that this had a significant effect on subsequent lactation performance.

The effects of dietary nitrogen sources and levels on rumen fermentation, nutrient degradation and digestion and rumen microbial activity by wether sheep given a high level of molasses

AbstractA 4 × 4 Latin square design experiment with 3-week experimental periods was conducted with four wether sheep, each fitted with a permanent rumen cannula, to evaluate the effects of dietary protein sources and levels on fermentation and microbial activity in the rumen. Four complete diets were offered each containing (g/kg dry matter (DM)) molasses 248, grass silage 200 and barley straw 260. The control diet (C) also contained barley and soya-bean meal and the other three diets were supplemented with urea (CU), soya-bean meal (CS), and soya-bean meal and fish meal (CSF), respectively. This gave foods of similar concentrations of metabolizable energy (ME) and estimated fermentable ME (10·6 and 9·8 MJ/kg DM, respectively), but different levels (g/kg DM) of estimated effective rumen degraded dietary protein (ERDP) and digestible undegraded protein (DUP) (ERDP/DUP, 84/17, 109/17, 116/38 and 119/54 for diets C, CU, CS and CSF, respectively).No clinical symptoms of ill health in the animals due to the feeding of molasses were observed during the experiment. The average pH values of rumen liquors obtained at various sampling times post feeding for diets C, CU, CS and CSF were 6·40, 6·49, 6·62 and 6·47 (s.e.d. 0·06 P < 0·05) respectively and average ammonia-nitrogen concentrations were 63, 81, 90 and 113 mg/l (s.e.d. 14·9, P < 0·02) respectively. The average concentrations of total volatile fatty acids in the rumen liquor were similar across the four treatments. The molar proportions of propionate and butyrate were higher for the diet C than for the other three diets (P < 0·05), while acetate was lower (P < 0·05). Supplementing with true protein (P < 0·05), but not with urea (P > 0·05), increased the molar proportions of isobutyrate and isovalerate. Whole tract apparent digestibilities of DM and organic matter did not differ significantly across the four treatments, but neutral-detergent fibre apparent digestibility (0·677, 0·672, 0·716 and 0·728 (s.e.d. 0·017) g/kg DM for diets C, CU, CS and CSF respectively) and the proportions of hay DM that disappeared in the rumen during 24 h incubation (0·223, 0·238, 0·284 and 0·271 (s.e.d. 0·019) g/kg DM) were significantly lower for diets C and CU than CS and CSF (P < 0·05). Urinary excretion of purine derivative nitrogen was similar across the four treatments. The results obtained from the present study indicate that there were no significant differences in the microbial crude protein synthesis in the rumen when a diet containing molasses was supplemented with urea or true protein. However, the supplementation of this control diet with true protein, but not with urea, did stimulate the degradation of hay DM in the rumen and the digestion of dietary fibre in the whole tract.

The influence of dietary energy source and dietary protein level on milk protein concentration from dairy cows

AbstractTo investigate the effects of energy source and protein level of diets on milk protein content, 12 multiparous Holstein-Friesian cows were used in a 4 × 4 Latin square change-over experiment with 4-week periods. Four diets were offered, withad libitumsilage as proportionately 0·40 of the diet, and the remaining 0·60 as one of four concentrates, two based on barley and two on molassed sugar-beet pulp. Two protein levels were achieved by altering the amounts of digestible undegraded protein in the concentrates, with all diets formulated to supply equal quantities of rumen degradable protein. There was no effect of diet on dry-matter intakes. Both starch and high dietary protein levels significantly increased milk protein concentration (P< 0·05), but had no effects on milk fat and lactose concentrations. Mean milk yields were significantly higher (P< 0·05) with increased dietary protein. Dietary protein significantly affected the yields of milk protein (P< 0·01) and lactose (P< 0·05) but not that of fat. Urinary allantoin excretion was significantly greater with both high protein (P< 0·05) and starch-based diets (P< 0·05). No significant interaction effects were found. It is concluded that dietary effects were due largely to differences in supply of rumen degradable protein; increases in milk protein concentration were therefore brought about by increasing the protein supply to the animal.

Chemical and protein quality parameters of heat processed sunflower oilcake for dairy cattle

The effect of heat processing on chemical and protein quality parameters of sunflower oilcake (SFOC) was evaluated. SFOC was processed in a drum roaster at six temperature settings and five time intervals. Chemical analysis included: N-solubility (N-sol.), percent pepsin insoluble nitrogen (% PIN), percent acid detergent insoluble nitrogen (% ADIN). These methods were used as screening tests to select six processed and one control sample for in situ evaluation. The in situ polyester bag and mobile bag techniques were used to determine the effective rumen protein degradability and undegradable protein (UDP) digestibility, respectively. Heat processing significantly influenced UDP digestibility. The relationship between total tract crude protein (CP) disappearance and % ADIN ( R 2 = 0.88), and between digestibility of UDP and % ADIN ( R 2 = 0.88) was linear ( P < 0.05), indicating the potential of % ADIN to indicate heat damage. Optimum heat processing was assumed to occur at 12 to 15% of total N as ADIN. Heat processing, decreased the concentrations ( P < 0.05) of the amino acids (AA) Arg, His, Lys and Ser in the unincubated samples. The AA Arg, His, Lys, Met, Ala, Ser and Tyr were ( P < 0.05) less resistant to microbial degradation compared with the control, whereas Lys, Asp, Gly and Ser were less absorbable ( P < 0.05). The largest amount of AA from UDP theoretically available in the small intestine (SI) occurred at 150°C/30 min, which agreed with the optimum level of ADIN. Results demonstrated the usefulness of ADIN as an indicator of heat damage for SFOC.

Protein supplementation of silage for ewes in late pregnancy

Ewes fed good quality grass silage need low levels (0.4-0.6 kg/d) of concentrate supplement to satisfy energy requirements in late pregnancy. However, the UK Metabolisable Protein (MP) system predicts that using a low level of a typical 180 g/kg crude protein (CP) compound will result in an undersupply of MP and therefore a higher digestible undegradable protein (DUP) content of compounds is required. Although the benefits of supplying additional DUP to lactating ewes are well established there is little or no experimental evidence to support the practice of supplementing silage based diets with supplementary DUP. The objective of the experiment was to evaluate the response to supplementary DUP in silage based diets.One hundred and twenty five scanned Scotch Mule ewes were synchronised, mated to Texel rams and allocated to 5 treatments balanced for liveweight, condition score, litter size, and parity. Five supplements were formulated to supply varying amounts of DUP and eRDP.

Protein supplementation of silage for ewes in late pregnancy

Ewes fed good quality grass silage need low levels (0.4-0.6 kg/d) of concentrate supplement to satisfy energy requirements in late pregnancy. However, the UK Metabolisable Protein (MP) system predicts that using a low level of a typical 180 g/kg crude protein (CP) compound will result in an undersupply of MP and therefore a higher digestible undegradable protein (DUP) content of compounds is required. Although the benefits of supplying additional DUP to lactating ewes are well established there is little or no experimental evidence to support the practice of supplementing silage based diets with supplementary DUP. The objective of the experiment was to evaluate the response to supplementary DUP in silage based diets.One hundred and twenty five scanned Scotch Mule ewes were synchronised, mated to Texel rams and allocated to 5 treatments balanced for liveweight, condition score, litter size, and parity. Five supplements were formulated to supply varying amounts of DUP and eRDP.

The effect of ERDP:FME ratio and DUP supply from concentrates on the performance of lactating ewes offered grazed grass

Fresh grass is a highly variable product, which is generally characterised as having a high crude protein content, with a high rate and extent of degradation in the rumen. For lactating ruminants, this may result in an effective rumen degradable protein: fermentable metabolisable energy (ERDP:FME) ratio in excess of the optimum requirement for microbial growth, leading to inefficient nitrogen utilisation and high levels of urinary nitrogen excretion. One method of improving the efficiency of nitrogen utilisation is the use of supplements. An appropriate supplement should optimise ERDP and FME supply to the rumen and provide sufficient metabolisable protein (MP) to balance animal requirements. The objective of the experiment was to investigate the response of lactating ewes offered grazed grass to variations in ERDP:FME ratio and digestible undegradable protein (DUP) supply from concentrate supplements.

The effect of ERDP:FME ratio and DUP supply from concentrates on the performance of lactating ewes offered grazed grass

Fresh grass is a highly variable product, which is generally characterised as having a high crude protein content, with a high rate and extent of degradation in the rumen. For lactating ruminants, this may result in an effective rumen degradable protein: fermentable metabolisable energy (ERDP:FME) ratio in excess of the optimum requirement for microbial growth, leading to inefficient nitrogen utilisation and high levels of urinary nitrogen excretion. One method of improving the efficiency of nitrogen utilisation is the use of supplements. An appropriate supplement should optimise ERDP and FME supply to the rumen and provide sufficient metabolisable protein (MP) to balance animal requirements. The objective of the experiment was to investigate the response of lactating ewes offered grazed grass to variations in ERDP:FME ratio and digestible undegradable protein (DUP) supply from concentrate supplements.

Strategies of feeding supplemental soybean meal to primiparous dairy cows

Primiparous dairy cows were utilized in two experiments to evaluate the productive benefits of modifying the strategy of within-day feeding of soybean meal (SBM) as a supplement to a basal mixed ration fed twice daily. The design of the two experiments was the same, although one was completed with early-lactation cows and the other with late-lactation cows. The evaluation of protein status of all treatments, after the experiments were complete, indicated that cows were limited by supplies of digestible undegraded intake protein (DUIP) on all treatments of both experiments. However, benefits of feeding 800 g d−1 of supplemental SBM versus none were primarily restricted to enhanced production of milk protein, and it is suggested that this was primarily the result of the contribution of DUIP from SBM to intestinal protein supply. Feeding SBM in two versus four daily meals either 1 or 1 and 5 h, respectively, after offer of the mixed ration had no influence on animal performance at either stage of lactation. However, feeding SBM in two daily meals 1 h prior to the mixed ration versus in two daily meals 1 h after offer of the mixed ration enhanced milk, milk energy, and milk lactose output in late lactation, but not in early lactation. These apparently inconsistent production responses between stages of lactation are consistent with a hypothesis that microbial growth is progressively restricted as supplies of degraded intake protein (DIP), relative to requirements, decline. Under these conditions, which applied to the late-lactation cows, feeding DIP at times of the day when rumen-soluble N levels would be lowest (i.e., pre-feeding) would be beneficial for stimulating microbial growth prior to ingestion of the mixed ration. Key words: Management, strategy, sequence, dairy cattle

Naloxone evokes a nutritionally dependent LH response in post partum beef cows but not in mid-luteal phase maiden heifers

AbstractData from two experiments are reported which test the hypothesis that nutrient and/or dry-matter intake and body condition may interact to modify hypothalamic opioidergic activity and thus influence the pulsatile release of LH during the early post-partum period and during the oestrous cycle. Experiment 1 involved 16 multiparous, twin-suckling beef cows, and was a 2 × 2 × 2 factorial design in which the factors were level of post-partum energy intake (80 v. 130 M) metabolizable energy (ME) per day), the digestible undegradable protein (DUP) content of the post-partum diet (14 v. 31 g/kg dry matter), and treatment with either 200 mg or 400 mg naloxone hydrochloride. Blood samples were collected at 15-min intervals for 4h at weeks 4 and 7 post partum. Naloxone was administered intravenously after the eighth sample. Experiment 2 involved 16 cyclic maiden heifers and was also arranged in a factorial manner, with two levels of body condition at the start of the experimental period (2·50 and 3·16 units) and two levels of energy intake thereafter (40 and 80 MJ ME per day). Seven blood samples were collected at 15-min intervals on 4 days consecutively during the mid-luteal phase of the oestrous cycle. On the first 2 of these 4 days naloxone was administered, whilst on the last 2 days a gonadotropin-releasing hormone agonist (buserelin; GnRH) was administered, both after the fourth sample. Plasma from both experiments was assayed for LH and prolactin (Prl).In experiment 1, cows on 130 MJ ME per day returned to oestrus and ovulated earlier than cows on 80 MJ ME per day (44·5 v. 55·0 days; s.e.d. = 3·93; P &lt; 0·05). At week 4 post partum the proportional increase in plasma LH following naloxone challenge was greater for cows on 130 MJ ME per day than cows on 80 MJ ME per day (1·38 v. 1·12; P &lt; 0·05), but the converse was true at week 7 (1·15 v. 1·68; P &lt; 0·05). Cows on the high DUP diet required a higher dose of naloxone to elicit an LH response. Few heifers in experiment 2 exhibited an LH response to naloxone. In contrast, there were significant dietary treatment effects on the LH response to GnRH (P &lt; 0·01). Relatively thin heifers on 40 MJ ME per day exhibited the lowest proportional increases in plasma LH to GnRH challenge, whereas heifers on 80 MJ ME per day and given the higher dose of GnRH produced the greatest plasma LH responses. Mean Prl concentrations before and after feeding in experiment 2 were respectively 13·2 and 10·2 ng/l (P &lt; 0·01).Suckled cows given a high energy diet during the early post-partum period can overcome the opioid mediated block on LH release and resume oestrous cycles earlier than cows given a low energy diet. LH would appear to be inhibited by a non-opioid mechanism in mid-luteal phase heifers. Total pituitary reserves ofLH may be influenced by the animals nutritional status.

The effect of metabolisable protein supply at constant energy intake on the liveweight gain of bovines

The metabolisable protein (MP) system (AFRC, 1992), adopted as the official method of describing the protein requirements of ruminants in the UK, introduces the concepts of effective rumen degradable protein (ERDP), digestible undegradable protein (DUP) and fermentable metabolisable energy (FME). For effective protein rationing, the aim is to match the supply of FME and ERDP, and to supply further protein requirements as DUP. This should lead to a better balance of energy and protein to meet the requirements of the animal. Diets are likely to have lower total protein contents than those presently available, leading to reductions in diet costs and nitrogen (N) excretion. The MP system was constructed primarily on a theoretical basis and this experiment was an initial step in validating it for beef cattle.

The effect of metabolisable protein supply at constant energy intake on the liveweight gain of bovines

The metabolisable protein (MP) system (AFRC, 1992), adopted as the official method of describing the protein requirements of ruminants in the UK, introduces the concepts of effective rumen degradable protein (ERDP), digestible undegradable protein (DUP) and fermentable metabolisable energy (FME). For effective protein rationing, the aim is to match the supply of FME and ERDP, and to supply further protein requirements as DUP. This should lead to a better balance of energy and protein to meet the requirements of the animal. Diets are likely to have lower total protein contents than those presently available, leading to reductions in diet costs and nitrogen (N) excretion. The MP system was constructed primarily on a theoretical basis and this experiment was an initial step in validating it for beef cattle.

The effect of pre- and post-partum energy and protein supply on the blood metabolites and reproductive performance of single- and twin-suckling beef cows

AbstractChanges in certain blood metabolites, serum progesterone concentration and pregnancy rate, were monitored for single- and twin-suckling cows in two experiments. In experiment 1, cows were managed to achieve condition scores at calving of 2·1 (low) and 3·1 (moderate). Subsequently, these animals were placed on a fixed level of energy intake (80 MJ metabolizable energy (ME) per day) for 16 weeks. Post-partum diets contained differing amounts of digestible undegradable protein (DUP), but similar amounts of effective rumen degradable protein (ERDP). In experiment 2, all cows were fed to achieve a condition score at calving of around 2·75. These animals were subsequently placed on two levels of energy intake (80 MJ and 130 MJ ME per day) for 16 weeks. The diets providing these levels of energy intake also contained differing amounts of DUP. Pregnancies were established by embryo transfer following induced oestrus.Cows in moderate body condition at calving subsequently had higher (P &lt; 0·05) serum non-esterified fatty acid (NEFA) concentrations. Cows on 130 MJ ME per day had lower serum NEFA concentrations than cows on 80 MJ ME per day. Cows given higher DUP diets had higher (P &lt;0 ·05) serum NEFA concentrations when in negative energy balance and lower serum NEFA concentrations when close to energy equilibrium than cows given lower DUP diets. Twin-suckling cows had higher (P &lt; 0·05) serum NEFA concentrations than single-suckling cows, but only during the first 3 weeks post partum. Plasma glucose concentrations were below 3 mmol/lfor twin-suckling cows until week 7 post partum when they became similar to the values for single-suckling cows. Serum D-3-hydroxybutyrate concentrations mirrored those of plasma glucose. Serum urea-nitrogen concentrations were high for twin-suckling cows on 80 MJ ME per day and single-suckling cows on 130 MJ ME per day.Neither body condition at calving nor post-partum energy intake significantly influenced the time taken for cows to overcome anovulation nor did they significantly influence the proportion of cows which eventually resumed normal oestrous cyclicity. DUP concentration in the post-partum diet had no overall effect on the various measures of fertility assessed but thin cows at calving subsequently placed on the high DUP diet took longer to ovulate (55 days; P &lt; 0·05) and had the lowest pregnancy rate (0·30). The post-partum anovulatory period was longer (P &lt; 0·01) by 27 days in experiment 1 and 12 days in experiment 2 for hvin-suckling cows compared with singlesuckling cows. A lower proportion (P &lt; 0·001) of twin-suckling cows regained oestrous cyclicity and became pregnant in experiment 1. Fertility traits were improved when twin-suckling cows were in moderate body condition at calving and/or offered 130 MJ ME per day during the post-partum period.

The effect of pre- and post-partum energy and protein supply on the performance of single- and twin-suckling beef cows and their calves

AbstractChanges in live weight, body condition, milk production and composition were monitored for single- and twinsuckling cows in two experiments. In experiment 1, all cows were managed for 3 months before calving to achieve condition scores at calving 2·1 (low) and 3·1 (moderate). Subsequently, these animals were placed on a fixed level of energy intake (80 MJ metabolizable energy (ME) per day) for 16 weeks. Post-partum diets contained differing amounts of digestible undegradable protein (DUP), but similar amounts of effective rumen degradable protein (ERDP). In experiment 2, single- and twin-suckling cows were fed to achieve a condition score at calving of around 2·75. These animals were subsequently placed on two levels of energy intake (80 MJ and 130 MJ ME per day) during the first 16 weeks of lactation. The diets providing these energy intakes also contained differing amounts of DUP. Neither the level of DUP in the diet nor the level of feeding significantly altered the digestibility of the dry matter or organic matter in the dry matter of the experimental diets.Body condition at calving had little effect on daily milk yield (9·5 kg) and composition (33·5 g/kg fat; 30-0 g/kg protein) in experiment 1. Cows with higher body condition scores at calving lost 13·5 kg more live weight and 0·26 units more body condition (P &lt; 0·05) during the 1st month post partum but remained in better condition throughout the trial period than cows with lower body condition scores. Cows on 130 MJ ME per day produced higher (P &lt; 0·001) daily yields of milk, milk fat and protein (+2·0 kg; +151 g; +85 g) and lost 57 kg less live weight and 0·52 units less body condition (P &lt; 0·001) than cows on 80 MJ ME per day. Elevated dietary levels of DUP promoted (P &lt; 0·05) daily milk yields (by 1·25 kg) and reduced live-weight and body condition-score loss during the 1st month post partum in both experiments. Twin-suckling cows produced the highest average daily yields of milk throughout the 16-week trial period in both experiments but yields were not significantly higher after early lactation in experiment 1. Cow body condition score at calving and the level of DUP in the post-partum diet of cows had no effect on the post-partum performance of calves. Twin calves had slower growth rates (P &lt; 0·001) than single calves (0·65 and 1·07 kg/day respectively) in experiment 1. However, twin calves sucking cows on 130 MJ ME per day in experiment 2 grew similarly to single sucking calves from week 8 of lactation (0·8 kg/day).

To determine the effect of feeding n ‘protected’ soyabean meal on milk production in high yielding dairy cows

In the UK the majority of dairy cow diets are based on grass silage and tend to over supply effective rumen degradable protein (ERDP ) as defined by the Metabolisable Protein (MP) system. As a result the nutritionist is often required to make up a shortfall in digestible undegraded protein (DUP) supply, particularly in diets for high yielding cows. Sources of additional dietary DUP fall into two categories: - vegetable or animal in origin. The DUP content of fishmeal is significantly higher than any of the naturally occurring vegetable proteins and the industry has been searching for some time for ways of improving the DUP content of vegetable proteins.In a novel treatment process soyabean meal is incubated at low temperature overnight in a solution of lignosulphonate. The treated meal undergoes a maillard reaction which reduces the extent of degradability in the rumen but does not affect digestibility in the small intestine.

The effects of effective rumen degraded dietary protein and digestible undegraded protein on rumen fermentation and microbial protein synthesis in wether sheep given high levels of molasses

The feeding of molasses influences the rumen fermentation by changing the balance of microbes in the rumen and their metabolism. One of the consequences is a decrease in efficiency of utilisation of dietary protein when high molasses levels are fed. The dietary protein requirements of ruminants may therefore be higher for diets containing high molasses levels. A previous experiment with dairy cows has shown positive responses in feed intake and milk production to increases in both effective rumen degraded dietary protein (ERDP) and digestible undegraded protein (DUP) in diets containing 310 g/kg DM of molaferm 20 (a mixture of 800 g cane molasses with 200 g condensed molasses solubles per kg, supplied by United Molasses) (Yan and Roberts, 1993). The current experiment was undertaken to evaluate the effects of dietary ERDP and DUP levels on rumen fermentation, hay DM degradability and microbial growth in the rumen of wether sheep.

In situ degradability of organic matter, crude protein and cell wall of various tree forages

AbstractLeaves of Leucaena leucocephala, Sesbania sesban and Calliandra callothyrsus were harvested in Rwanda from young shoots at 8 weeks after the first cutting. They were dried, ground and incubated at the same time in polyester bags in three non-lactating Holstein-Friesian cows each fitted with a ruminal cannula. The bags were removed at 0, 2, 4, 8, 24, 48, 72 and 144 h after the start of incubations. The different parameters characterizing extent and rate of ruminal degradation of organic matter (OM), neutral-detergent fibre (NDF), and crude protein (CP) were calculated. In vitro digestibility of residual protein after 24 h and 48 h incubation was also determined. Sesbania sesban had lowest cell wall contents and gave highest ruminal degradability for OM, NDF and CP. Leucaena leucocephala was degraded to a lesser extent, but its undegraded protein had a somewhat higher in vitro digestibility. In contrast, protein of Calliandra callothyrsus was poorly degraded and digested. The proportion and composition of cell wall could not explain these differences in digestion characteristics and other measurements, such as tannins, were incriminated. Increased ruminal incubation time augmented the extent of ruminal degradation and reduced in vitro digestibility of undegraded protein but did not affect the undigestible protein fraction.