ALBERT

Description: SummaryIsogenic fertile and sterile forage maize (cv. LG 11) grown in separate fields were harvested at regular intervals during growth between mid-July and early October 1979. Leaf, stem and ear components and whole plant (before and after ensiling) were examined for changes in the concentration of dry matter (D.M.), soluble sugars, starch, hemicellulose, cellulose, neutral detergent fibre (NDF) and acid detergent fibre (ADF). In vitro digestibility values for D.M., organic matter (OM) and OM in the D.M. were also determined in fresh and ensiled whole crops.Prior to ensiling the concentration of non-structural carbohydrates in the two crops was markedly different. Fresh fertile plants contained (as g/kg D.M.) 369 and 101 of starch and soluble sugars respectively. Corresponding values for sterile plants were 54 and 343 respectively. Sucrose was the most abundant soluble sugar present and contributed 64 and 74% of the totals in fertile and sterile plants respectively, prior to ensiling. Increases in plant D.M. during growth were significantly affected by the deposition of starch and are described by the following equation:y = 13·6 + 0·49 (±0·073) x(r = 0·93)where y = whole-crop D.M. concentration and x = starch concentration in D.M. The concentrations of hemicellulose and cellulose of both types of fresh plants were similar but those of ADF and NDF were lower in sterile plants. Xylose was the major constituent neutral sugar in the hemicellulose fraction and formed 68 and 76% of the total hemicellulose in the fertile and sterile plants, respectively. In vitro digestibility values of sterile plants tended to be higher than their fertile counterparts.After ensiling, the concentration of soluble sugar in the sterile and fertile crops decreased from 343 to 8 g/kg D.M. and 101 to 5 g/kg D.M. respectively. The in vitro DOMD values of the sterile and fertile crops decreased by 16 and 11 percentage units respectively; both final values were recorded as 61.In vivo digestibility values determined in 18-month-old wether sheep fed at maintenance, for NDF, ADF, cellulose, hemicellulose, nitrogen, OM, D.M. and OM in D.M. were 60·2, 58·0, 65·8, 64·1, 32·9, 66·6, 65·4 and 63·7 respectively for fertile plant silage. These were all markedly lower than the corresponding values for the sterile plant silage which were 68·3, 70·3, 74·8, 73·3, 60·3, 71·3, 69·6 and 67·7 respectively. Within the hemicellulose fraction the digestibility values for xylose in both sterile and fertile plant silage were considerably lower than the values recorded for either arabinose or galactose. In vitro digestibility values for D.M., OM and OM in the D.M. were similar to in vivo values for fertile plant silage but were lower than in vivo values for sterile plant silage.Dairy herd replacement heifers (aged 3–6 months) had higher D.M. intakes when given fertile plant silage ad libitum than with sterile plant silage. However, the liveweight gains of the heifers on sterile and fertile plant silage differed little.

Description: Growth and efficiencies of nitrogen and energy utilization for growth by 72 young British Friesian steers (initial live weight (LW) 110 kg) offered a well preserved, formic acid-treated, perennial ryegrass silage with and without supplements of fish meal were examined. Silage was offered either alone or mixed with 50, 100 or 150 g fish meal/kg silage dry matter (DM) and each diet was offered either ad libitum or intakes were restricted to 16, 19 or 22 g dietary DM/kg LW/day. Treatments were imposed over a period of 132 days. Body component weight gains were determined by comparative slaughter.Increasing the level of either feeding or fish meal increased rates of empty body weight gain linearly (P

Description: Mixed rumen bacteria entering the duodenum of a ruminant are a major source of some of the nutrients required by the animal. A number of values for the chemical composition of mixed rumen bacteria have been reported and a few observations made on interrelationships between different components at different times after feeding (Hoogenraad & Hird, 1970; Jouany & Thivend, 1972; Bird, 1973; Smith & McAllan, 1973; Czerkawski, 1975; McAllan & Smith, 1974, 1976). There is also some published information on in vivo variations in the storage carbohydrate in mixed rumen bacteria with different diets (Jouany & Thivend, 1972; McAllan & Smith, 1976) but no information on interrelationships between such variations and changes in other components in the bacteria.The present paper reports a study of such interrelationships in bacterial samples, containing wide ranges of storage polysaccharide (α-dextran) and crude protein concentrations, obtained from steers given a wide variety of diets.

Description: SummaryThe (early maturing) maize hybrid, Anjou 210, was sown on 1 May (1975) and 50000 (LD) and 150000 (HD) plants/ha established. Leaf, stem, ear and husk components of the shoots, and whole shoots were separately examined for changes in dry weight, soluble sugars, starch, hemicellulose and cellulose at regular intervals from 104 to 154 days after planting together with whole shoots after ensiling.Throughout the sampling period whole shoot and ear dry weights increased steadily whereas those of leaf and stem decreased in plants from both treatments.Total soluble sugar contents for plants grown at LD were at a maximum 104 days after planting compared with 125 days after planting for the HD crop. Immediately prior to ensiling whole shoot soluble sugar content was 74 and 93 g/kg D.M. for LD and HD treatments respectively.Small amounts of starch (g/kg D.M.) were found in stems (10–25), husks (40–80) and leaves (17–35) of plants grown at both densities. The starch content of the ear increased from 57 to 390 g/kg D.M. and 168 to 376 g/kg D.M. in plants grown at LD and HD respectively.For plants from both treatments hemicellulose contents of husks, leaves and whole shoots increased with age whereas those of stems decreased. Cellulose contents did not vary greatly over the growing season.On ensiling plants from both densities, total soluble sugars had virtually disappeared after only 3 days. Apparent losses (approximately 0·3 g/g), over a longer period of time, were observed in hemicellulose sugars and starch. Apparent increases were observed in cellulose contents of approximately 0·15 g/g.

Description: SummaryYoung steers with rumen and simple duodenal cannulas were given diets of approximately equal amounts of flaked maize and hay (A) or of flaked maize and straw supplemented with decorticated groundnut meal (DCGM) (B), fishmeal (C), heated soya-bean meal (D) or raw soya-bean meal (E) or of dried grass (F). A cow with rumen and re-entrant duodenal cannulas was given diets of hay and dairy cubes.Some steers received doses of 32P-labelled inorganic phosphate twice daily with their concentrate feed. This led to small diurnal variations in inorganic P–32P specific activity but at similar daily sampling times the 32P specific activity in rumen bacterial nucleic acids reached a steady state after dosing for about 4 days. Contributions of microbial-N to non-ammonia-N (NA-N) entering the duodenum were then estimated by comparing nucleic acid 32P/NA-N ratios in related samples of rumen bacteria and duodenal contents. Similar estimates were made in these and other animals using α-, ε-diaminopimelic acid (DAP) and ribonucleic acid (RNA) as bacterial markers.Estimates for steers given diets A, B, C and F based upon ‘32P-labelled RNA nucleotides’ were, on average, 85% of those based upon total RNA. The differences were attributed mainly to the latter being elevated by the presence of small amounts of dietary RNA. When RNA-based estimates of the proportion of microbial-N in NA-N in duodenal contents for these and other steers which were nearly free of protozoa were multiplied by 0·85 (‘adjusted RNA’) the values were, on average, similar to those based upon DAP. Similar estimates for the cow based upon ‘adjusted RNA’ measurements were, however, about twice those based upon DAP, probably because the cow contained a high protozoal population and the DAP based, method did not account for protozoal N.For some steers total flows at the duodenum of organic matter (OM), microbial-N (mean based upon ‘adjusted RNA’ and DAP) and residual food N were estimated by reference to chromic oxide. Average values for g microbial-N synthesized/kg OM truly digested in the rumen for the different diets ranged from 15 to 22 (mean 20). Mean degradabilities of food N (residual food N at duodenum/N intake) were 0·57, 0·71, 0·71, 0·70 and 0·84 for diets A, B, C, D and E respectively. No differences between diets were significant at P 〈 0·05.

Description: SUMMARYEstimates have been made of the amount of energy fermented and the amounts of microbial protein and total fatty acids synthesized in the rumen of sheep given various rations of hay and concentrates. The sheep had re-entrant cannulas in the proximal duodenum. The amount of protein synthesized was calculated from the flow of RNA-N at the duodenum. The change in the amount of total fatty acids between the food and the proximal duodenum was also measured.In Expt 1, six sheep were given a low-protein basal diet and the same diet supplemented with a vegetable protein concentrate with or without tannin treatment. Some 72% of the digestible energy was apparently digested in the rumen and an estimated 150–170 g microbial protein were synthesized per kg organic matter apparently digested in the rumen. Differences due to the dietary treatments in the amount of energy digested and the amount of microbial protein synthesized were small and non-significant.In Expt 2, the effect of a supplement of 20 g/day of cod-liver oil (CLO) on digestion of a mixed diet of hay and concentrates was examined in five sheep. Despite a marked fall in the ratio of acetic acid to propionic acid in the rumen volatile fatty acids when CLO was added, there were no clear differences in the amount of energy fermented in the rumen, which averaged 64% of the digestible energy, or in the efficiency of microbial protein synthesis, which averaged 200 g/kg organic matter apparently digested in the rumen. On the basal diet an increase of 6·7 g total fatty acid/day occurred in the stomach. This was presumably synthesized in the rumen. However when CLO was added to the diet, a decrease of 4·1 g total fatty acid/day was measured.

Description: Previous studies have demonstrated that protein sources which are primarily degraded in the rumen such as rapeseed meal or soyabean meal may be as effective as a less rumen degradable protein source such as fishmeal in supporting higher levels of animal performance in young steers fed on grass silage. However, the response to type of protein supplement is likely to be influenced by the composition of the basal diet. This study has examined the effect of supplementing silages prepared from early (EH) and late (LH) harvested grass with two protein sources of differing rumen degradability, rapeseed meal (RSM) and fishmeal (FM) or a mixture of the two (M), thus creating eight experimental diets of LH, LHRSM, LHFM, LHM, EH, EHRSM, EHFM and EHM. Silage was offered ad libitum and supplements were included at 100 g fresh weight/kg silage DM intake. The RSM and M diets were made isonitrogenous with FM diets by the addition of urea. Animals remained on diets for 18 weeks and liveweights were monitored for a further 13 weeks while the animals were at pasture. Dry matter (DM) intakes and liveweight gains were higher with EH than with LH silage (P 〈 0·001). Response to type of protein supplement was dependent on silage quality. On LH silage, higher intakes were noted on FM and M (82·4 and 82·8 g DM/unit metabolic liveweight/day, respectively) relative to silage only (75·8 g DM/unit metabolic liveweight/day) and this contributed towards higher liveweight gains (P 〈 0·01). Liveweight gains tended to be higher on LH silage supplemented with FM compared to RSM (0·76 v. 0·67 kg/day, respectively, P = 0·08). In comparison, on EH silage, relative to EH unsupplemented, the intake was highest on M (89·2 v. 96·6 g DM/unit metabolic liveweight/day), but liveweight gains were not significantly different between supplements. On turnout to pasture, those animals fed on silage alone exhibited compensatory growth (P 〈 0·025) with the result that those fed on LH silage only grew faster and achieved the same liveweight after 13 weeks at grass as those supplemented with RSM or M. There was a tendency for those fed on FM to maintain an advantage in liveweight after the period at pasture. On EH silage, at the end of the grazing period no significant differences in liveweight existed between the different supplements and on average were 23 kg heavier than EH silage unsupplemented. In conclusion, silage type (stage of harvest and quality) and protein supplementation influenced animal performance. On late harvest and poorer digestibility silage, there was some indication that feeding fishmeal was better than rapeseed but this was less evident on early harvest and higher digestibility silage. However, considering the price differential between these two supplements and small difference in animal performance it is concluded that rapeseed meal is as effective as fishmeal when used as a protein supplement for growing cattle fed on grass silage.