The effect of different rates of potassium (K) fertilizer on the yield and quality of sugar beet was studied in a series of 26 trials on soils of different type and K index between 1992 and 1997. There were few yield responses even though the majority of trials were on soils of low K index, and large quantities of fertilizer were applied (0–600 kg K/ha). Potassium offtakes (kg/ha) in the harvested beet increased asymptotically, not linearly, with yield and were much larger for a given yield on high K index soils than on low index soils. Commercially acceptable concentrations of beet K for processing are in the range 700 to 1000 mg K/100 g sugar. Concentrations in excess of this decrease the amount of sugar crystallized from the extracted juice. They were not greatly affected by large applications of fertilizer K but were strongly influenced by long-established differences in soil exchangeable K (Kex) due to soil type, previous cropping or manuring history.

The asymptotic nature of the K offtake[ratio ]yield relationship was confirmed by factory tarehouse measurements relating to the national sugar beet crop delivered during the 1993–97 UK processing campaigns. Potassium offtakes generally increased linearly with yield up to 60–70 adjusted t of clean beet/ha, but increased little beyond that. The amount of K removed by a 60–70 t/ha crop of beet varied from 70 kg K/ha on low K index sandy loams to 120 kg K/ha on clay soils of K index 3 and above. Further increases in yield decreased the amount of K in fresh beet from 1·7 to 1·4 kg K/t on low K index soils, and from 3·6 to 2·5 kg K/t on high K index soils.

An analysis of data from individual fields of commercially grown sugar beet showed that much of the site and season variation in the K content of beet was due to differences in K uptake driven by Kex, and to differential effects of nitrogen (N) supply on K uptake and sugar yield. Regressions on Kex and total crop N (kg/ha) accounted for c. 30 and 50% of the variance in beet K content, respectively, and the two together for over 60%. Total N uptake by the crops ranged from 100 to 550 kg N/ha. The total K content of the crop and the amounts of K in the beet (kg/ha) both increased linearly with crop N over the whole of this range, whereas sugar yield increased asymptotically with total uptakes of N up to 250–300 kg N/ha. Consequently, low yielding crops grown on soils in which N and K were freely available produced beet of poor K quality. However, the asymptotic relationship between beet K (kg/ha) and yield implies that, in many situations, the processing quality of the beet could be improved by increasing yield through better agronomy.

A spaced plant experiment and a sward experiment were conducted at INIA La Estanzuela, Uruguay in 1996 with six red clover (Trifolium pratense L.) populations, to study the efficacy of selecting genotypes for sward performance in a spaced plant nursery. This was examined through: (a) the ranking of the best linear unbiased predictors (BLUP) of populations and (b) the ratio of the correlated genetic advance in swards by selecting under spaced plant conditions to the direct genetic advance of selecting under sward conditions. From the eight characters analysed, only the rankings of BLUPs for leaf size and flowering were significantly the same between populations. The other six characters performed differently according to the level of competition imposed. Post-grazing leafiness and the difference between pre- and post-grazing leafiness (the two most important characters to measure preferential grazing) achieved greater genetic advance when selection was done as spaced plants: while for pre- and post-grazing height genetic advance was greatest by selecting under sward conditions. For other characters, the best conditions to select depended on the selection intensity achievable.

In the soyabean [Glycine max (L.) Merr.]–B. japonicum symbiosis, genistein has been identified as one of the major compounds in soyabean seed and root extracts responsible for inducing the expression of the B. japonicum nod genes. High combined nitrogen in the growth medium inhibits nodulation and nitrogen assimilation. Two experiments were conducted to test the possibility of overcoming this inhibition by adding genistein to the rooting medium and by incubation of B. japonicum cells with genistein. One soyabean cultivar was used in the first experiment, and two in the second experiment. The experiments were conducted in a glasshouse using a completely randomized design with three rooting medium nitrate concentrations (0, 5 and 10 mM) and four genistein treatments. The genistein treatments were 0 (control), incubation of B. japonicum cells with 5 μM genistein, and regular watering with 5 μM or 20 μM genistein. A two way interaction existed in the first experiment, and two and three way interactions existed in the second experiment. Root growth was inhibited by repeated watering with 20 μM genistein. Weight per nodule was greater at 5 mM than at 0 mM nitrate. At 10 mM nitrate watering with genistein resulted in significant increases in nodule dry weight per plant. Shoot nitrogen contents were significantly increased at 5 mM nitrate by genistein incubation and watering with 20 μM genistein. Watering with 5 μM genistein significantly increased nodule nitrogen concentrations at both 5 and 10 mM nitrate. The two soyabean cultivars responded differently to the genistein and nitrate treatments in terms of nodule number, nodule weight, leaf nitrogen concentration and nodule nitrogen content. Genistein could, at least partially, overcome the inhibition of soyabean nodulation and nitrogen assimilation by nitrate.

The responses of Leucadendron ‘Safari sunset’, on its own roots and grafted on ‘Orot’ rootstock, to a range of fertilization regimes were studied. The experiment was conducted during the summer of 1994, at Bet Dagan, Israel, and included three levels of compound NPK, two levels of P, and two NH4[ratio ]NO3 ratios.

Ungrafted plants fed without P yielded fewest marketable branches and had the lowest fresh and dry weights. Increasing the P concentration in the irrigation water to 10 mg/dm3 improved the yield, whereas increasing the NPK level reduced the number of marketable branches and the fresh and dry weight yields. Lowering the NH4[ratio ]NO3 ratio in the irrigation water significantly reduced the yield.

The grafted plants were significantly better than the ungrafted plants under all the treatments examined. The superiority of the grafted plants was more evident under conditions of P deficiency and non-optimal pH.

Thirty steers were used in two pen experiments (Expts 1 and 2), and 27 of these in a third (Expt 3), to quantify their responses of hay intake, rumen ammonia nitrogen (RAN) concentrations, and liveweight to inputs of rumen soluble nitrogen (urea) and rumen undegradable protein (formaldehyde-treated casein; F-casein) when added to a basal diet of low quality hays. The hays were made from unimproved native pastures typical of those grazed by cattle in the subtropics of Australia and contained 7·8 g N/kg dry matter (DM) with coefficient of organic matter digestibility of 0·503 in Expts 1 and 2, and 5·2 g N/kg DM with a digestibility range from 0·385 to 0·448 in Expt 3. The steers (15 months old) were either Brahman (B), Hereford (H) or the F1 Brahman×Hereford (BH) cross. Steers were offered supplementary minerals with the hays in each experiment. In Expt 1 (35 days) urea was sprayed on part of the hay, allowing for daily urea intakes (g/steer) of either 0, 5, 11, 16 or 26. In Expt 2 (42 days), F-casein was offered daily (g/steer) at either 0, 75, 150, 225 or 300 and in Expt 3 (56 days) discrete offerings were made of soluble casein (225 g/day), of urea (18 g/day)+F-casein (225 g/day) or of nil.

There were significant linear effects of urea intake upon hay intake and liveweight change of steers. However, B steers had smaller increases in intake and liveweight change than did H steers, and B steers did not have a linear increase in RAN concentrations with increasing urea intake as did H and BH steers. In Expt 2 there were significant linear effects of F-casein supplements on hay intake and liveweight change of steers and a significant improvement in their feed conversion ratio (i.e. DM intake: liveweight change). The B steers did not differ from H and BH steers in liveweight change but had significantly lower hay intakes and non-significantly smaller increases in RAN with increasing F-casein intake. In Expt 3, hay intake of the steers increased with soluble casein (by 16·8%) and with urea+F-casein (24·5%). Only steers given urea+F-casein had a high RAN concentration (94 mg/l) and a high liveweight gain. The B steers had a liveweight loss and a lower hay intake than H or BH steers in Expt 3 but a higher RAN concentration.

These studies have indicated the importance of the form and quantity of additional N required by cattle of differing breed types to optimize their feed intake and liveweight gain when offered low-N, low-digestible hays.

Two studies were conducted at Massey University in 1998. Expt 1 investigated the combined use of n-alkanes and 13C techniques for the estimation of individual proportions and total intakes of herbage (H) and maize silage (MS) by dairy cows. Expt 2 measured the variation in the amount of MS consumed by individual cows fed as a group. In Expt 1, six dry Holstein–Friesian cows were kept indoors and fed a diet containing one of the following H[ratio ]MS ratios (dry matter basis)[ratio ]100[ratio ]0, 80[ratio ]20, 60[ratio ]40, 40[ratio ]60, 20[ratio ]80 or 10[ratio ]90 for 25 days. Cows were dosed with a slow-release capsule containing 8 g of dotriacontane (C32) and 8 g of hexatriacontane (C36). Intake estimates were based on individual faecal samples collected twice daily during two 5-day periods. In Expt 2 (grazing trial), 12 early-lactation cows were selected from a commercial herd of 48 autumn-calving cows and blocked into pairs according to milk yield, lactation length and lactation number in a complete block randomized design. Within each pair, cows were randomly assigned to two treatments: supplemented, S (4 kg MS DM per cow after the morning milking in feed troughs) or not supplemented, NS. Another eight cows were randomly selected from the rest of the herd to increase the number of individual estimations of H and MS intakes. Cows grazed perennial ryegrass-white clover pasture during the rest of the day. In Expt 1, H[ratio ]MS ratios were not accurately predicted by the odd-chained n-alkanes, but there was a strong linear relationship between the concentration of 13C in faeces and actual H: MS ratios in the diet. The 13C method was therefore combined with the n-alkanes, resulting in accurate estimations of H and MS intakes. In Expt 2, a large variation was observed among individual cows in their daily intakes of MS (range 0·94 to 5·09 kg DM per cow, coefficient of variation = 36%), but this variation in MS intake was not associated with milk yield (P > 0·05). The results indicate that the n-alkane and 13C techniques can be successfully combined to estimate the intake of MS and H of grazing cows supplemented as a group. Under the conditions of the present study, individual cows differ considerably in the amount of maize silage consumed per day, although the reasons for this are not clear.

The production of NH+4-N following in vitro incubation of cattle urine was monitored for 24 h in the presence of ampicillin sodium salt (0, 32, 64, 128 mg/l), hydroquinone (0, 16·7, 33·4, 66·8 mg/l), wheat straw (0, 3·3, 6·6, 13·2 g/l) or spruce sawdust (0, 3·3, 6·6, 13·2 g/l) with (20 IU) or without urease. Each concentration of ampicillin, hydroquinone, wheat straw or spruce sawdust was tested in triplicate.

The equipment consisted of Woulff flasks containing 300 ml of a buffered solution (0·02 M; pH 7·50) with 1 ml of cattle urine. The cattle urine was characterized by measuring the main nitrogen contents, which were 6·52 mg total-N/ml, 5·96 mg urea-N/ml and 0·026 mg ammonium-N/ml. The initial pH of urine was 7·84. Ammonium and nitrate concentrations, and pH were monitored at zero- time and after 3, 6 and 24 h of incubation with the cattle urine.

The addition of urease to the flasks containing urine induced a significant increase in the production of ammonium-N, from 1·83 to 6·32 mg NH+4-N/flask after 24 h of incubation.

In the presence of urease, an inhibitory effect was recorded in NH+4-N production with ampicillin and spruce sawdust. In contrast, hydroquinone inhibited urease activity and wheat straw adsorbed the NH+4-N produced, both causing a dose-dependent relationship.

In the absence of urease, ampicillin, hydroquinone, wheat straw or spruce sawdust caused a dose- related decrease in NH+4-N production. However, the highest amounts of wheat straw (6·6 and 13·2 g/flask) exhibited a temporary increase in NH+4-N production during the first 6 h. This is probably due to a generation of extra NH+4-N as compared to the control flasks without straw. However, at 24 h, the situation paralleled the other materials.

Although pH increased approximately from 7·50 to 7·65 during the hydrolysis of urea in the presence of urease, no gaseous ammonia was volatilized into a 0·1 M HCl flask. Moreover, no increase in nitrate concentration was found during the incubation.

The present results suggest that ampicillin, hydroquinone and spruce sawdust could be used in order to reduce NH+4-N production from cattle urine. The NH+4-N already produced could probably be absorbed on wheat straw.

An experiment was carried out to determine the effects of parasitic status and level of feeding motivation on the diet selected by sheep grazing perennial ryegrass/white clover swards. Twenty-four female Scottish Blackface weaned lambs were divided into four treatment groups each of six animals. Pre-grazing treatments were imposed to create two levels of feeding motivation, low (fed ad libitum) and high (0·60 of ad libitum diet) and two parasitic states, parasitized (daily dose of 2500 L3Ostertagia circumcincta) and non-parasitized. Each treatment group was placed in one of four 0·35 ha field plots and allowed to graze a mixed grass/clover sward. Mean clover height was manipulated pre-grazing by cutting so that it was less than the mean grass height. This maximized the probability that clover in the diet of sheep was due to selection. No fertilizer was added to the sward in order to ensure that the nitrogen content of the clover was higher than that of the grass. Each treatment group was rotated around the four plots on a daily basis for 2 weeks. Sheep with a high feeding motivation strongly and significantly selected clover and had a higher proportion of clover in their diet compared with sheep with low feeding motivation. Parasitic status had no significant effect on the diet selection of sheep; but the level of parasitic burden within parasitized sheep was positively correlated with the proportion of clover in the diet. Parasitized sheep spent less time grazing each day and had lower daily herbage intakes compared with non-parasitized sheep. This was a result of a reduction in the duration of feeding bouts and not a reduced number of bouts per day. Sheep with the higher feeding motivation had a greater number of feeding bouts per day and this resulted in those animals having a greater daily herbage intake. Level of feeding motivation had greater effects on the diet selection of sheep than parasitic status. Sheep with a high feeding motivation are able to select strongly for clover in their diet when there is low overall clover availability and are capable of dramatically affecting the species composition of a sward. This has implications to the maintenance of a desired grass/clover ratio in grazed swards.

Acacia saligna, a leguminous tree, has a high crude protein content, remains green all year and can be grown in deserts using only runoff water. However, dry matter intake (DMI) by sheep and goats of A. saligna is low, presumably due to its high tannin content. It has been suggested that DMI could be increased by such methods as wilting of the forage and by neutralizing the negative effects of tannins by tannin-complexing agents. The purpose of this study was to determine DMI of supplementary A. saligna (phyllodes and small stems) by grazing sheep (∼ 50 kg) and goats (∼ 37 kg) when the animals were (1) offered wilted or fresh material (Expt 1); and (2) administered with polyethylene glycol (PEG), a tannin-binding agent (Expt 2). In this second experiment, there were three 14-day periods in which one group each of sheep and goats was on a regime of: No PEG–PEG–No PEG, whereas another group was on a regime of: No PEG–No PEG–PEG. In Expt 1, the DMI of A. saligna was statistically higher in goats than in sheep, but there was no difference in intake between fresh and wilted material. Average DMI of A. saligna, both fresh and wilted, was 124·1 g/day or 8·41 g/kg0·75 per day for goats and 94·1 g/day or 5·05 g/kg0·75 per day for sheep. Goats and sheep consuming fresh A. saligna gained more body mass than their respective controls; the difference was significantly greater in goats but not in sheep. In Expt 2, DMI of fresh A. saligna in the first period (before PEG) was 104·1 g/day or 7·16 g/kg0·75 per day for goats and 84·8 g/day or 4·51 g/kg0·75 per day for sheep. Administration of PEG during the second period resulted in an increase in DMI of 62% in goats and 83% in sheep. These animals maintained a high A. saligna intake in the third period when PEG was withdrawn. Goats and sheep that did not receive PEG in the second period had similar A. saligna intake as in the first period, but increased intake by 62% and 47%, respectively, with PEG in the third period. Overall, the two goat groups and two sheep groups consuming A. saligna lost less body mass than their respective controls; the difference was significantly less in sheep but not in goats. It was concluded that wilting A. saligna did not increase DMI. Administration of PEG increased A. saligna intake and the intake remained high after PEG was withdrawn. Offering A. saligna as a supplement had a positive effect on body mass change.

Data on 1468 pregnancies and 2356 newborn goat kids of six genetic groups under intensive management were utilized to determine some genetic and non-genetic factors affecting gestation length, and to assess the relationship between gestation length and survival of kids to 25 days of age. The study revealed significant (P < 0·01) effect of breed of dam, litter weight, breeding season and parity on gestation length. Number of kids born and sex of kids were not a significant source of variation affecting this trait. Granadina goats had the shortest gestation (149·0±0·31 days), whereas Toggenburg (151·7±0·28 days) and Alpine (151·4±0·46 days) had the longest. Litter weight and gestation period were related curvilinearly in summer and linearly in autumn. Gestation of goats bred in summer was 1 day longer (P < 0·01) than those mated in the autumn. There was a progressive reduction of gestation length as parity increased (151·3±0·24, 150·6±0·17 and 149·9±0·39 days for 1, 2·6 and > 7 kiddings, respectively). The mean survival rate of kids gestated < 148 days and 148–;152 days were 78±2 and 87±1, respectively, and these were significantly lower (P < 0·05) than the survival rate of kids gestated 152–156 days and > 156 days (94±1 and 95±2). In conclusion, prolonged gestation (152–160 days) in goats was beneficial because it resulted in heavier litters at birth and higher viability of neonatal kids.

Analyses were made on birth weight of 2706 kids (six genetic groups) under confinement conditions in the arid zone of northern Mexico, to study the effect of air temperature (mean annual temperature = 21·1 °C) during gestation on this trait. The relationship of environmental temperature at kidding and survival of kids was also studied. Birth weight was significantly negatively related to mean dry bulb air temperature during gestation (reduction of 40±3 g for 1 °C increase in mean air temperature during gestation; r = −0·22; P < 0·01), although temperature only explained 5% of the variance of kid birth weight. Mean minimum temperatures (< 4 °C) 5 days after birth significantly reduced kid survival (83% v. 89–93% for kids born when temperatures were above 4 °C; P < 0·01). Air temperatures between 30 and 41 °C during the perinatal period did not affect (P > 0·05) survival rate. These results suggest that newborn kids seem to be relatively resistant to high air temperature, but are fairly susceptible to cold stress. Also, birth weight of kids from goats exposed to high air temperature during pregnancy was marginally reduced, although this was of limited economic significance.