Interaction of molecular nitrogen with free-electron-laser radiation.

We compute molecular continuum orbitals in the single center expansion scheme. We then employ these orbitals to obtain molecular Auger rates and single-photon ionization cross sections to study the interaction of N2 with Free-Electron-Laser (FEL) pulses. The nuclei are kept fixed. We formulate rate equations for the energetically allowed molecular and atomic transitions and we account for dissociation through additional terms in the rate equations. Solving these equations for different parameters of the FEL pulse, allows us to identify the most efficient parameters of the FEL pulse for obtaining the highest contribution of double core hole states (DCH) in the final atomic ion fragments. Finally we identify the contribution of DCH states in the electron spectra and show that the DCH state contribution is more easily identified in the photo-ionization rather than the Auger transitions.

Responses to supplementation in white Fulani cattle under agro-pastoral management in northern Nigeria. II. Fodder.

The effect of dry-season supplementation of White Fulani cattle in northern Nigeria with legume standing hay (fodderbanks) was investigated. Over 430 cattle were recorded in 8 herds over 2.5 years. Fodder bank supplementation may have reduced weight losses in calves and breeding females during the dry-season. Emergency sales of immature animals were lower on fodder banks (6.5% vs 14.3%, P < 0.01). There was no evidence that fodder banks reduced cattle mortalities during the dry season. Fodder banks may have had a deleterious effect by encouraging dry-season conceptions. Resulting dry season calvings led to calving percentages of 36.9% on fodder and 60.3% on no fodder (P < 0.05). Calf mortality was also higher on fodder banks; animals not reaching their second year were 13% on fodder bank vs 3.9% on no fodder (P < 0.01). It was concluded that dry season nutrition interaction with the agro-pastoralist livestock system needs further investigation.

Responses to supplementation in white Fulani cattle under agro-pastoral management in northern Nigeria. 1. Phosphorus.

Using on-farm supplementation trials with a P rich block (Phos) and a salt block (Salt), deficiency of P in White Fulani cattle in Nigeria was investigated. There was some evidence, significant in some locations but nonsignificant overall, that P supplemented dams produced heavier calves and supported greater calf growth. Dam mean weight gains, 9 to 1 months pre-partum were 6.9 kg/month on Phos (s.d. = 5.0, n = 50) and 3.8 kg/month on Salt (s.d. = 4.7 n = 54) (P > 0.05). Overall least squares means of calf weights at 12 months were 105.2 kg (n = 29, s.e. 9.3) on Phos and 91.5 kg (n = 37, s.e. 6.3) on Salt (P > 0.05). In animals below 2 years of age, mortalities were 6.8% on Phos and 13.6% on Salt (n = 179, Chi-square P < 0.01). No response to supplementation was observed in older and non-pregnant cattle.

Reducing age at first calving in N'Dama heifers using groundnut cake as a supplement to grazed natural pasture in The Gambia.

N'Dama heifers, initially weighing 129 kg at approximately 30 months of age, were supplemented with 250, 500 or 1000 g/head/day groundnut cake for 3 or 6 months during the dry or dry and wet seasons. Highly significant improvements in rates of liveweight gain and reproductive performance were obtained. Supplementation during the dry season only, approximately trebled the proportion of animals calving within 2 years of the beginning of the trial (6 vs 20%, P < 0.05), while this increase was around eight-fold in the animals that continued to receive supplement during the wet season (6 vs 50%, P < 0.05). Conceptions occurred at an overall mean liveweight of 185 kg, and a "target" liveweight of 200 kg for the first conception of N'Dama heifers is proposed as the basis for husbandry recommendations concerning these animals. It is concluded that such intervention can reduce the usually observed age at first calving of village based N'Dama heifers by 12 months, in a fashion that is both practicable and financially advantageous.

Prevalence of coccidial infections in the West African Dwarf goat in the subhumid zone of Nigeria.

An investigation was made of the seasonal incidence of coccidial infection in West African Dwarf (WAD) goats in 2 villages and an on-station situation in the subhumid zone of Nigeria. Faecal samples were obtained from about 70 goats in each village and 160 on-station at 4 times of the year, early and late dry and wet seasons. Six species of Eimeria were found to occur; E. arloingi, E. apsheronica, E. pallida, E. alijevi, E. jolchievi and E. ninakohlyakimovae which accounted for 18, 16, 22, 9, 24, and 11% of infections respectively. Overall rates of infection were very high, averaging approximately 87%, and peaked during the late wet season, when the proportion of heavy infections also increased significantly. At this time the proportion of heavy infections classified as heavy was significantly higher in the village goats than the on-station goats, and was also significantly higher in kids than in adults. Clinical disease only occurred in kids. The potential benefits of controlling such infections in terms of productivity responses appear worthy of further investigation in these farming systems.

Effect of liveweight and body condition on work output from draft oxen.

A trial was carried out to assess the effect of liveweight and body condition on working capacity of zebu oxen. Over a working period of 9 days, animals which started work with a mean liveweight of 360 kg and body condition score of M+ produced the highest daily work output (3.43 MJ). At an initial liveweight of 360 kg, body condition had relatively little effect on work output, and animals of condition score M- produced a daily work output of 3.19 MJ. In contrast, at a mean liveweight of 310 kg at the start of work, mean daily work output of animals of condition score M+ was significantly lower than that of animals in poorer condition (M-), at 0.81 compared with 2.50 MJ work output per day. It was concluded that body weight as indicated by body size is probably a more useful indicator of likely capacity for work than body condition under the short-season working conditions typical for oxen in the semi-arid zone of central Mali.

Effects of trypanosome inferction and postpartum liveweight change on resumption of reproduction activity in N'Dama cows.

Data on reproduction, liveweight and trypanosome infection of N'Dama cattle raised under traditional husbandry systems in The Gambia were analyzed to quantify the relative effects of postpartum liveweight change and infection with pathogenic trypanosomes on 2 parameters of reproductive efficiency: the ability to calve within 21 months after the initial parturition and the length of the calving interval. Information for the study was obtained from a database on an epidemiological survey begun in 1985 in The Gambia. Calving records (n=294) from 3 locations were classified on the basis of body weight change and prevalence of trypanosome infection between 1 and 4 months postpartum. Least-squares analyses adjusted for effects of location, season of calving, viability of calf, and parity showed that the proportion of cows that calved within 21 months was 50% for cows which maintained or lost less than 5% of the initial postpartum weight and 31% for cows which lost a higher percentage of weight. Corresponding mean calving intervals were 567 and 666 days, respectively (P<0.05). With regard to trypanosome infection, 49% of uninfected cows and 32% of infected cows (P<0.05) calved again within 21 months, with calving intervals of 581 and 651 days, respectively (P<0.05). The interaction between liveweight change and trypanosome infection status was not significant. Furthermore, the findings suggest that while postpartum body weight loss impairs reproductive performance, trypanosome infection does likewise, and these effects may act independently of each other.

Effect of change in body weight and condition during the dry season on capacity for work of draft oxen.

Work oxen supplemented at different levels during a feeding period of 3 months, were divided into 3 groups of average weight change -25, +35 and +70 kg and worked under loadings of either 7.5 or 12.5 kgf/100 kg of liveweight for 2 weeks, in order to assess the impact of dry season supplementation on capacity for work. At approximately equal levels of stress in work, manifest in maximum heart rate one minute after ceasing work (MHR), oxen with higher dry-season weight gain produced higher levels of work output, in proportion to their increased body weight. Rate of work and mean daily work output increased from the first to the second week of work, in spite of average daily weight losses of 2.63 kg throughout the period. Decline in rate of working through each day was continuous and essentially linear with relation to distance worked. The time taken to cover 1 km increased at an average of 0.16 and 0.68 min/km for light and heavy loadings respectively. Although MHR appeared to provide a retrospective measure of the level of stress attained in work, it was of limited use as a predictor of reasonable work demand. Maximum heart rate was related to work output (MJ) and animal liveweight (kg), as follows: MHR = 17.7 (+/- 3.94) WO - 0.15 (+/- 0.080) LWT + 118.5 (r2 = 0.70 P < 0.01).

Interaction between physiological status in N'Dama cows and trypanosome infections and its effect on health and productivity of cattle in Gambia.

Data collected for three years on incidence of trypanosome infections, degree of anaemia as assessed by packed red cell volume (PCV) and live weights of four groups of cows of varying physiological status were analysed. The animals were not harbouring trypanosomes during a period of two to three months before exposure to periods of increasing density of tsetse flies (Glossina morsitans submorsitans) while grazing in savannah woodlands. The groups of cows were formed on the following basis: pregnant and lactating (lactating-pregnant) (Group 1, n = 143); pregnant and not lactating (dry-pregnant) (Group 2, n = 69); non-pregnant and lactating (lactating-open) (Group 3, n = 160); non-pregnant and not lactating (dry-open) (Group 4, n = 49). Monthly trypanosome prevalence was highest (17.5%) in the cows with the highest physiological stress (Group 1), followed by Group 3 (11.1%) and Group 2 (10.0%) with the lowest prevalence found in the least stressed cows, Group 4 (1.6%). Average PCV values for dry-pregnant cows (Group 2; 27.0%) and dry-open cows (Group 4; 26.2%), whether infected or not, were higher than those lactating (Group 1; 25.3% and Group 3; 23.6%). A body weight gain of 4.3 kg between the month of October and the following June was recorded for dry-pregnant cows (Group 2) whereas a weight loss of 16 kg occurred in the lactating-pregnant and lactating-open cows (Groups 1 and 3), with more severe losses recorded in infected than uninfected cows. Dry-open cows (Group 4) maintained their weight during the observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of partial suckling of crossbred dairy cows on milk offtake and calf growth in the Ethiopian highlands.

The effects of implementing a restricted suckling regime with crossbred dairy cows have been examined in the Ethiopian highlands. Calves were allowed to suckle their dams for two minutes before each milking until weaning and this system was compared with the common practice of rearing by bucket feeding. Restricted suckling significantly increased calf growth rate to weaning, from 0.31 to 0.53 kg/d (P less than 0.01). No differences in calf growth post-weaning occurred, so that the 20 kg difference in liveweight that had been achieved by the restricted suckled calves by the time of weaning persisted until the calves were nine months old, when observations ceased. Total milk offtake was not significantly affected by treatment, although that obtained from the partially-suckled animals over their whole lactation exceeded that from the other treatment by 15%. Partial suckling delayed return to oestrus post partum but this was offset to some degree by fewer services per conception, hence calving interval was not significantly increased. Voluntary feed consumption was similarly unaffected and it is concluded that restricted suckling offers tangible advantages for adoption by smallholders using crossbred cows in dairy production systems.

Comparison of sesame cake and cottonseed as supplementary sources of protein to weaned N'Dama bull calves in The Gambia.

The potential for increased productivity of N'Dama cattle in response to small supplementary inputs of proteinaceous by-products has been shown to be substantial under village husbandry conditions in The Gambia. Young N'Dama bulls were used to compare sesame cake with cottonseed as sources of supplementary protein during the wet and early dry seasons of 1987. They were fed 0, 40, 80 or 160 g crude protein/day in these forms for four months. Supplementation significantly increased growth rate from 169 g/d in controls to means of 272 and 271 g/d for those given sesame cake and cottonseed respectively; there were no significant differences among the supplemented groups. During the four months of the dry season immediately after supplementation ceased all previously supplemented groups grew significantly more rapidly than the controls (at least P less than 0.05), indicating a substantial carry over effect of the supplements. Over this period the mean gain of the groups previously given sesame cake exceeded that of those that had received cottonseed (217 cf. 158 g/d; P less than 0.01). The economic benefits of these responses were substantial.

Observations on the phosphorus requirement of cattle for growth.

Weaner cattle were fed ad libitum a diet of Stylosanthes humilis (Townsville stylo) containing 1.80 per cent nitrogen and 0.12 per cent phosphorus in the dry matter, with or without a supplement of phosphorus at the rate of 5 g/day. The feed was consumed in amounts sufficient to support gains in weight of over 0.5 kg/day during the experiment, and the supplement had no influence on voluntary feed intake, live weight gain or phosphorus concentration in samples of rib bone obtained by biopsy at the end of the experiment. It is suggested that the recomendations of the Agricultural Research Council and the National Research Council for the intake of phosphorus by young growing cattle overestimate requirements by approximately 35 per cent.

Phosphorus content of bovine rib: influence of earlier biopsy of the same rib.

Serial sampling of bovine rib is undertaken experimentally to monitor changes in the degree of skeletal mineralisation. The validity of this approach depends on the assumption that the previous sampling of a bone does not influence the composition of a sample obtained subsequently. To test this, the effect of a prior biopsy sampling on phosphorus content of the remaining bone was determined at various times after the initial sampling. A preliminary biopsy sample was taken with a 1.5 cm diameter trephine from the left 12th rib of 40 cattle; experimental samples were taken from the same rib of 10 of the cattle at three, six, nine and 12 months later, for comparison with similar samples taken concurrently from the right 12th rib. The phosphorus content of the second left rib was significantly lower than that of the right (control) rib at the three-month interval, particularly where the sampling site was ventral, rather than dorsal, to the site from which the initial biopsy was obtained. No effects of previous biopsy sampling were observed after six, nine or 12 months.

Variation in the phosphorus content of bone samples obtained from the last three ribs of cattle.

Variation in the phosphorus content and specific gravity of bone samples taken from the 11th, 12th and 13th ribs of cattle was examined in relation to the selection of a site for the acquisition of such samples by biopsy, in experiments where changes in skeletal phosphorus storage required to be monitored. The degree of mineralisation of the 11th rib was significantly higher than that of the 12th, which in turn was greater than that of the 13th. It was concluded that valid comparisons may be made between bone samples obtained during an experimental regime, provided they are taken from the same numbered rib; it is recommended that the 13th rib be avoided in such studies.

Fate of cyst(e)ine synthesized by microbial activity in the ruminant caecum.

Cyst(e)ine synthesized by microorganisms in the caecum of sheep was labelled following the infusion of Na2 35SO4 into the terminal ileum. [35S]Cyst(e)ine activity was detected in the faeces, but not in plasma or wool. Appreciable absorption of 35S, presumably in the form of sulphide, into the circulation occurred, and its presence in saliva was demonstrated. It was concluded that nutritionally negligible quantities of cyst(e)ine are likely to be absorbed from the ovine large intestine.

The true absorption of cyst(e)ine from the ovine small intestine.

Na234SO4 was infused into the rumen of a sheep fed a dried grass diet. 2. The digesta at the pylorus which contained 35S-labelled cyst(e)ine synthesized by the rumen microflora was collected and mixed with chromium EDTA. This material was infused into the duodenum of 35S free sheep. 3. Ileal digesta was subsequently collected and analysed for cyst(e)ine 35S and Cr. 4. The proportion of the labelled cyst(e)ine truly absorbed from the small intestine was 0-72 +/- 0-004.