A. de Vega

Effect of ammonia treatment and carbohydrate supplementation on the intake and digestibility of barley straw diets by sheep

Abstract The changes in straw voluntary intake and apparent digestibility caused by the ammoniation of straw and energy supplementation in diets fed to adult, non-productive sheep were studied in two experiments. In Experiment 1, untreated (US) or ammonia treated (TS) barley straw were given as the only feed to four ewes in a cross-over design. Ammoniation increased straw dry matter (DM) intake from 30.2 to 50.6 g kg −1 LW 0.75 , organic matter digestibility (OMD) from 0.438 to 0.519 and digestible organic matter intake (DOMI) from 12.5 to 24.7 g kg −1 LW 0.75 , allowing energy maintenance requirements to be met. In Experiment 2, three groups of four ewes received US, with another three groups of four receiving TS, both supplemented with meadow grass hay (H), rolled barley (B) or sugar-beet pulp (P) in a 2 × 3 factorial design. Each supplement was given in amounts of 150, 300, 450 and 600 g day −1 , in a Latin-square design. The type of supplement did not significantly affect straw intake at any level of inclusion. The level of supplementation scarcely affected US intake, whereas DM intake of TS diminished linearly. Substitution rates were 0.49 ± 0.088, 0.61 ± 0.085 and 0.55 ± 0.131 for TS-H, TS-B and TS-P diets, respectively ( P > 0.05). Apparent digestibility of straw was not significantly affected by supplementation. Increases in total DOMI when the level of supplementation was augmented were lower in TS than in US diets, and with H than with B or P as supplements. To reach the DOMI obtained with TS as the only feed, US has to be supplemented with 420, 272 or 269 g DM of H, B or P, respectively.

Validation of use of purine bases as a microbial marker by 15 N labelling in growing lambs given high-concentrate diets: effects of grain processing, animal age and digesta sampling site

The origin of post-ruminal purine bases ( PB) was studied in 24 growing lambs that were given a pelleted concentrate plus barley straw (C) or whole barley grain plus protein supplement ( WB). Six lambs from each treatment were slaughtered at 10 and 30 days post weaning after 15 N labelling of microbial nitrogen (N) and PB. Microbial contribution to digesta nonammonia N (NAN) and PB was lower ( P < 0·01) when estimated from duodenal rather than abomasal samples (0·36 v. 0·52 (s.e.d. 0·021) for NAN and 0·47 v. 0·77 (s.e.d. 0·029) for PB) as a result of endogenous contamination. In comparison with 15 N, total PB/N led to higher estimates ( P < 0·01) of microbial contribution to abomasal NAN in WB treatment (0·62 v. 0·46 s.e.d. 0·049). The difference was removed after correcting for microbial PB, while this effect was not observed with < the C diet, resulting in a marker by diet interaction ( P < 0·05). Abomasal PB flow increased ( P < 0·1) from 10 to 30 days after weaning mainly due to the higher proportion of microbial PB (0·70 v. 0·81 (s.e.d. 0·047)). Rumen apparent PB degradation did not differ between diets in older lambs, but it was proportionally 0·39 lower for WB treatment ( P < 0·05) in younger lambs. When the microbial PB flow was estimated indirectly from labelled microbial N and the PB/N ratio of bacterial extracts the estimates were in agreement with those derived from PB- 15 N in the WB treatment but resulted in unrealistic values in lambs on diet C. Results suggest that significant proportions of dietary PB can escape rumen degradation which may lead to overestimation of microbial contribution to abomasal NAN when the PB/N ratio is used as marker. The extent of the overestimation is affected by the lamb age and grain processing.

In vitro studies of the metabolism of [14C]- n-alkanes using ruminal fluid of sheep as substrate.

Whether the rumen microbes are able to synthesize and/or degrade long-chain alkanes in anaerobic conditions remains a question to be answered before these hydrocarbons can be confidently used as duodenal flow or rumen transit markers. In this context, an experiment in vitro was carried out to establish whether within a rumen liquor fermentation system, n-alkanes can be derived from de-waxed structures of the plant or from non-alkane wax components (long-chain fatty alcohols, long-chain fatty acids and esters), or may be metabolized by bacteria to other components or to shorter-chain hydrocarbons. Ryegrass was labelled with 14C in growth chambers under controlled conditions in order to use it as a substrate. The labelled material obtained was separated in three fractions: labelled alkanes, labelled de-waxed plant and labelled wax components without the alkanes. These fractions were used for three different incubations in vitro, which objectives were as follows: 1. To check whether rumen bacteria can synthesize alkanes from carbon structures other than waxes (e.g. sugars). 2. To verify whether rumen bacteria can metabolize the n-alkanes to other compounds. 3. To check whether rumen bacteria can synthesize n-alkanes from other carbon compounds from waxes. The results showed that there was neither bacterial synthesis nor metabolism of the n-alkanes in in vitro conditions.

Determination of ytterbium by AES-ICP. Application to samples of biological origin

SummaryYtterbium is used as a marker in studies of digestion physiology in ruminants; its determination has been accomplished by Inductively Coupled Plasma — Atomic Emission Spectroscopy (ICP-AES). An analytical study has been carried out, which includes the evaluation of various emission lines (atomic, ionic). The line at 328.937 nm is proposed for determining Yb, with a limit of detection of 1.68 ×10−3μg ml−1. The analytical procedure has been applied to the determination of this element in samples of animal fodder, rumen contents and feces.

Net transfer of nutrients to the duodenum and disappearance of n-alkanes in the reticulo-rumen and the hindgut of sheep fed grass/legume combinations

An experiment was carried out to examine the effect of increasing the proportion of Wimmera ryegrass hay in a lucerne hay-based diet on net transfer of nutrients to the intestine, and on the disappearance of n-alkanes in the reticulo-rumen and the hindgut of sheep. Following a latin square design, four adult ewes were fed 1:0, 0·33:0·67, 0·67:0·33 and 0:1 proportions of legume and grass. Increasing the proportion of ryegrass in the diet linearly decreased the intake of DM (P= 0·017), organic matter (P= 0·021) and N (P= 0·001). However, neutral-detergent fibre intake was not affected (P= 0·148), nor was its digestibility coefficient (P>0·10). Diet had no effect on duodenal flows of nutrients (P>0·10), although the proportion of N intake (NI) recovered at the duodenum as non-NH₃ N (NAN) increased linearly with Lolium rigidum in the diet (P= 0·002). Full recovery of NI as NAN was achieved at NH₃ concentrations in the rumen below 110 g/l. Microbial N contribution to NAN varied in a quadratic manner (P< 0·05) with the proportion of grass in the diet, although efficiency of microbial synthesis was not affected (P>0·10). Duodenal recovery of consumed n-alkanes was not affected by diet and was complete for those present in higher concentrations in the forages. Isolated rumen bacteria contained significant amounts of n-alkanes, contributing to the duodenal flow of these hydrocarbons in variable proportions depending on the diet consumed.

Effects of including olive cake in the diet on performance and rumen function of beef cattle

Beef meat in many Mediterranean countries is produced by feeding the animals with high proportions of concentrates and barley straw. In these conditions, feeding costs are high and compromise the profitability of feedlots. Mediterranean countries are also major producers of olive oil, and the processing of this product generates a large quantity of co-products with a high environmental impact. No data appear available in the literature about the effects of including olive by-products in the diet of beef cattle on animal performance. A pen-feeding study was carried out during two growing phases: from 100 to 250 kg (12 weeks), and from 250 to 450 kg (18 weeks). During the first phase 120 steers (mostly Friesian, with an average age of 129 ± 1.1 days) were distributed in six groups of 20 animals each. Two groups were assigned to one of each of the following treatments: a control compound feed based on barley, control with 10% dry matter (DM) substituted by second-extraction pitted and dehydrated olive cake, and control with 20% DM substituted by olive cake. Compound feeds of this first phase were formulated to contain 16–17% crude protein, and were offered ad libitum to the animals. Barley straw was offered as a roughage source. Animals were weighed every 3 weeks, and a digestibility trial was carried out in the middle of the period with four animals per treatment. During the second phase, compound feeds were formulated to contain 14.5–15% crude protein. Rumen fermentation was studied using six steers and the feeds employed in the second growing phase, following a crossover design with two periods. Concentrates were offered once daily allowing at least 10% refusals. Barley straw was also offered as a source of roughage. For each period of the crossover, 15 days were allowed for adaptation to the experimental diets. Samples of rumen liquid were taken at 0 (just before), 4 and 8 h after feeding. The pH, and concentrations of ammonia and volatile fatty acids were determined. Inclusion of up to 20% second-extraction pitted and dehydrated olive cake (DM basis) in the diet did not affect performance of beef steers for the whole growth period. Inclusion of those ingredients in the diet of these animals might be advisable depending on their market price.

Use of barley crops, and combinations of lucerne and Wimmera grass, as pasture for grazing sheep in the semiarid zones of Spain

Taking into account the relationship between rainfall and temperature, 64% of the Spanish territory can be classified as arid (25%) or semiarid (39%). In these areas, vegetal surface includes permanent pastures and drought grasslands (34.0%), fallows (13.4%), winter cereals for grain production (21.2%), forage crops (mainly lucerne, and winter cereals harvested as green forage; 2.6%) and woodland hills. Ruminants in these zones account for 15.4 million head, of which nearly 80% are sheep. In the present paper, the possibilities of integrating sheep in cropping systems are discussed, and an alternative based on the use of permanent sowed prairies (lucerne), self-sowing annuals (Wimmera ryegrass) and winter cereals (barley) will be analysed.

Effect of cereal processing (grinding to 3·5 mm or dry-rolling) in maize- or barley-based high-concentrate diets on rumen environment of beef cattle during the late fattening period

The type and processing of cereals for beef cattle are key factors to maximize performance without increasing the risk of ruminal acidosis. The current work studied the effect of grinding (G) or dry-rolling (R) the cereals in a concentrate based on maize (M) or barley (B) on the rumen environment of eight 6-month-old Holstein calves, which received either M or B for 70 days, offered as G and R in two consecutive periods. Daily feed intake pattern, rumen fermentation traits, total rumen bacteria and relative proportions of Streptococcus bovis and Selenomonas ruminantium were characterized twice in each period at 0, 4 and 8 h after feeding. Dry-rolling promoted a 0·25 reduction of concentrate intake during the first 4 h after feeding. Neither cereal type nor its processing form promoted differences in ruminal fermentation at 0 and 4 h; however, 8 h after feeding R cereals resulted in higher rumen pH (6·17 v. 5·71) and lower concentration of lactic acid (88·1 v. 156 mg/l) and volatile fatty acids (only in diet B, 118 v. 164 m m /l) compared with G. Little effect of dietary factors in the target rumen microorganisms were observed. The more balanced fermentation observed with R cereals may be explained by the lower concentrate intake promoted during the first 4 h, coupled with a more difficult access of bacterial enzymes to their starch, thus reducing its fermentation rate. Therefore, feeding dry-rolled cereals may be useful to reduce the risk of acidosis by regulating the intake pattern of the concentrate and/or its fermentation rate.