1. In each of 6 digestibility trials, comprising a total of 21 measurement periods of 3-4 days, two steers were fed on herbage cut from the top of the sward, two on the remaining bottom growth and two on a mixture of equal parts of these fractions. Within each period the fractions were similar in digestibility although the top growth had a higher content of nitrogen.

2. The trials were divided into three groups, according to time of year, for the purpose of calculating regressions of digestibility on faecal nitrogen concentration. Regressions calculated in the usual manner on a between-period basis (i.e. within animals) had constant terms which differed significantly among animals but not from one fraction of the herbage to another.

The effects of feeding Leucaena leucocephala on semen quality and fertility were examined using four dihydroxy pyridone (DHP)-adapted (21.0, 26.5, 27.0 and 31.0 kg) and four DHP-unadapted (28.0, 31.0, 40.0 and 44.0 kg) South African indigenous Nguni bucks (mature male goats). The DHP-adapted bucks were assigned to air-dried Leucaena leucocephala forage (LL; Leucaena group) while the unadapted ones were maintained on a cereal-based concentrate diet (C; concentrate group) containing 122 g crude protein (CP)/kg over an 84-day period. Buck semen samples were collected on days 0 and 77 of the study. On the last day of the study (day 84), bucks in the Leucaena group were divided into two equal subgroups; a subgroup was assigned to Leucaena leucocephala-grass pasture (LGP) with ten does (mature female goats) while the second subgroup was assigned to natural pasture (NP) with nine does. Similarly, the two concentrate subgroups were separately assigned to mate nine and ten does on LGP and NP plots, respectively. The proportions of normal semen on both groups were not significantly different. However, semen quality on LL treatment increased significantly (P = 0.004) between days 0 and 77 and probably explains the significant (P<0.01) difference between the fertility rates of bucks on both treatments. There was no evidence that feeding LL was detrimental to semen quality and fertility of bucks and to conception among females mated by the bucks fed the forage; perhaps due to the fact that the bucks had adapted to DHP as a result of the DHP-degrading rumen bacteria (Synergistes jonesii) that were transferred to them by the does. Synergistes jonesii is known to be capable of detoxifying mimosine and its toxic metabolites to innocuous compounds.

Soybean varieties genetically free from Kunitz trypsin inhibitor (KTI) and lipoxygenase-2 (Lox2) are desirable to increase human consumption, as the former is an antinutritional factor that affects protein digestibility while the latter is a principal contributor to off-flavour. In the present investigation, soybean genotypes free from both these undesirable components were developed by introgression of null allele of Lox2 from NRC109 (lox2lox2) into two KTI-free soybean genotypes derived from genotypes JS97-52 and NRC7. Foreground selection of plants in F1, F2, BC1F1, BC1F2, BC2F1 and BC2F2 generations developed from two cross combinations i.e. NRC7-derived KTI-free genotype (N7KTIF)×NRC109 (parental combination 1) and JS97-52 derived KTI free genotype (JKTIF)×NRC109 (parental combination 2) was performed using null allele specific markers and tightly linked simple sequence repeat (SSR) markers for both KTI and Lox2 genes for the identification of homozygous recessive (titilox2lox2) plants. Background selection was performed using 239 and 241 polymorphic SSR markers across the genome. This resulted in the development of 9 and 13 soybean lines stacked for null alleles of both KTI and Lox2 (titilox2lox2) exhibiting recurrent parent genome content more than 97 and 96%, respectively. Days-to-flowering, days-to-maturity, 100-seed weight and yield per plant of the stacked lines developed from both the parental combinations were at par with the respective recurrent parents.

The fungicides benomyl and captafol separately were tank mixed with each of the insecticides decis (decamethrin), permethrin, and cypermethrin (synthetic pyrethroids) and nuvacron (monocrotophos). The mixtures were tested as foliar sprays at three spraying regimes to protect cow-pea plants against pod and foliar diseases and insect pod borers.

Two sprays, 1·5 kg a. i. /ha of benomyl mixed with 0·75 kg a. i. /tia of monocrotophos at 35 and 49 days after planting, gave the best control of brown blotch, web blight, Cercospora leaf spot and the pod borer, Maruca testulalis. This regime also gave the highest grain yield for two consecutive years. The mixtures were not phytotoxic. Interactions between the test fungicides, insecticides and spraying regimes in relation to disease and pest control and yields are discussed.

The estimation of phosphate in soil extracts presents certain difficulties owing to the small amount usually present. Practically all the methods make use of the phospho-molybdate precipitate. Hehner's method based on the weighing of this precipitate was adopted by Dyer, and has been recently investigated by. Auld.

The consumption of three different tropical pastures by the conventional clipping method and by the nitrogen–chromic oxide technique were assessed and compared over a 2-year period. The clipping method was found to give consistently higher estimates of consumption of herbage dry matter by grazing steers than the chromic oxide method by approximately 16, 14 and 25% respectively for treatments E (Gynodon + Centrosema), F (Mixture E + Stylosanthes) and G (Digitaria + two legumes), when data for the 2 years were pooled for each treatment.

The mean live-weight gain over the 2-year period was 0·19 kg per head per day. This figure is essentially in agreement with that obtained for the same group of animals in the previous 2 years. As would be expected the lowest gain was recorded during the dry season when there was little or nothing to graze. It was similarly observed that during a severe attack of trypanosomiasis the animals sustained some losses even though there was abundant pasture to graze.

Shearing causes a rapid increase in plasma cortisol concentrations (Kilgour & de Langen 1970; Purchas 1973; Fulkerson & Jamieson 1982), indicating that acute physiological responses are associated with the procedure. Environmental stress before mating can result in a delay in the onset of oestrus (Doney et al. 1973) and a reduction in ovulation rates (Doney et al. 1976). Dobson (1988) demonstrated that shearing caused a reduction in the luteinizing hormone (LH) response to exogenous gonadotrophin releasing hormone (GnRH) in anoestrous ewes. Such a response to shearing could influence the incidence of oestrus and ovulation.

Association mapping based on linkage disequilibrium is an effective approach for dissecting the inheritance of complex multi-gene traits. In the present study, association mapping was performed for yield traits based on 172 popular Upland cotton (Gossypium hirsutum L.) cultivars in China and 331 polymorphic simple sequence repeat (SSR) markers. The gene diversity index of 331 markers ranged from 0·0387 to 0·7799 with an average of 0·4002, and the polymorphism information content ranged from 0·0379 to 0·7473 with an average of 0·3375. A total of 93 significantly associated markers for seven yield traits were identified across more than one environment, among which 11 were for seed cotton yield, 12 for lint yield, 11 for boll number per plant, 13 for boll weight, 21 for lint percentage, 14 for lint index and 11 for seed index. The corresponding ranges in phenotypic variation explained by markers across four environments for these seven traits were 1·75–10·49, 1·75–9·34, 2·84–11·80, 2·59–9·89, 2·38–13·97, 2·73–14·82 and 2·50–11·88%, respectively. Some of the yield-associated markers detected were found to be linked to or associated with the same traits identified in previous studies. Furthermore, elite alleles for yield traits were also mined. The present study can provide useful information for further understanding the genetic basis of yield traits, and facilitate high-yield breeding by molecular design in Upland cotton.

Certain relationships between linear live animal and carcass measurements and the quantitative composition of the half-carcass have been established.

Of the live linear body measurements taken, the length of the fore-cannon bone and length of the hind leg appear to have close relationship with carcass measurements. Live fore-cannon bone is a good index of the total weight of bone in the halfcarcass and therefore has application in the selection of meat sheep.

Of the carcass measurements studied, length of fore-cannon bone and length of tibia + tarsus (T) appear to be satisfactory predictors of the total weight of bone.

The fibre length and diameter distributions of the wool of two Merino flocks were evaluated at the neck, mid-side and breech positions, to determine the incidence of fibres which were off-type by reason of excessive length, diameter or possession of a medulla.

The ranges of fibre lengths for 10·5–11·0 months' growth were 1·0–17·5 cm. in flock 1 and 1·0–16·5 cm in flock 2. There was no evidence of a bi-modal length distribution in either flock.

Fibre diameters at 15–16 months were observed in the range 6–69 μ in flock 1 and 5–52 μ in flock 2. Medullated fibres ranged from 7 to 50 μ in flock 1 and 5–64 μt in flock 2. The incidence of medullation increased in an antero-posterior direction from 0·17 to 0·28% in flock 1 and 0·11 to 0·28% in flock 2.

Tests for homogeneity of variance were applied to the estimates of fleece characters in this study as well as estimates of other workers. From these comparisons it is suggested that sheep in the present study are representative of the Merino breed in staple length, fibre diameter and to a lesser extent crimp frequency. The considerable between-animal variation in the observed incidence of medullation should aid in selection against that character with a consequent improvement in wool quality.

The effects of paraquat (l, 1'-dimethyl-4, 4'-dipyridylium dichloride or Gramoxone) and diquat (l,1'-ethylene-2, 2'-dipyridylium dichloride or Reglone) on inhibition of flowering and the effect of such an inhibition on improvement of cane yield and juice quality in late maturing sugarcane varieties Co. 853 (early-season flowering) and Co. 419 (mid-late season flowering) planted in February were studied under field conditions at Coimbatore (latitude 11° N). In Co. 419, the spray of paraquat @ 0·35 kg a.i./ha and diquat @ 0·45 kg a.i./ha (diluted in 3000 1 of water) in two equal doses at 3–4 day intervals during the 1st and 2nd week of August suppressed the flowering almost completely, while in Co. 853 flowering could not be checked successfully by chemical spray. Flowering in Co. 853 could be checked only when the spindle leaves were cut continuously from 15 July to 12 August at 4–5 day intervals. In Co. 419, cutting leaf spindles at any day between 1 August and 12 August prevented flowering totally.

The sprayed non-flowered crop of Co. 419 gave 13·84–15·69 t/ha more cane yield in February and 16·14–18·07 t/ha in April, whereas sugar yield increased by 1·16 t/ha in February and 3·56 t/ha in April compared with the control flowered crop. There was practically no difference in paraquat and diquat sprays. Suppression of flowering by defoliation in Co. 853 also increased the cane and sugar yield in and after February.

A series of trials were conducted during 1979–82 under semi-arid conditions in a Mediterranean-type environment to study the edge effects in mechanized durum wheat and barley variety trials when uncropped pathways are left between plots. Varietal differences in edge effects on grain yield were in most trials not significant. Thus, edge effects do not distort significantly the relative ranking of varieties.

Edge effects were significant for all traits studied and higher in grain and straw yields. These effects were also higher in drier seasons. The overestimation of grain yield from whole plots was 13–18% in relatively high rainfall seasons and 29% in a dry season. In two seasons the scores on the two outer rows were higher than on the two central rows by 89 and 117 % for grain yield, by 72 and 73% for straw yield, by 44 and 48% for numbers of tillers, by 6% for 1000-grain weight and by 14 and 40% for number of grains per tiller. The edge effect was not confined to the outer rows, but it extended to the inner rows of the plot; the magnitude of this effect varied with season and trait.

Rows adjacent to the pathway and unprotected from wind had a lower value for all traits than the opposite rows of the pathway, which were protected by the inner rows.

From monogerm sugar-beet seed as harvested non-viable fruits have to be eliminated, multigerm ones rejected and the size made sufficiently uniform for use in precision drills. Seed which had been gently rubbed to remove some of the cortex was graded for diameter, thickness and by aspiration, either singly or in combination. Effects of grading were determined by laboratory germination tests, radiography and field sowings in which seedling emergence and crop growth and yield were recorded.

Grading by thickness was effective in removing multigerm fruits. Grading by aspiration and diameter rejected non-viable seed and reduced the variation in size. By combining all three grading methods, samples of seed of 80% germination and 90% monogermity were produced, provided the seed lot as threshed gave at least 50% germination. True seed weight increased with fruit diameter but only the first aspiration was effective in removing light true seeds. Radiography showed that both aspiration and, to a less extent, grading by diameter were effective in removing most empty fruits but neither eliminated those with shrivelled seed. The field experiments confirmed that increase in fruit diameter or aspiration gave more seedlings. Even at uniform, high plant density, sugar yields were less from the smallest (less than 3 mm diameter) than from the other grades of seed. The initial aspiration also improved sugar yield but further aspiration decreased yield.

The effect of the amount of milk consumed upon the herbage intake and performance of calves at pasture, following a standard rearing period, was investigated using 50 Hereford × Friesian calves purchased at 10–12 days ofage. All calves were offered 6 kg reconstituted milk substitute for a 58 day period indoors and for a subsequent 31 days at pasture. Ten calves were then allocated to each of five milk treatments (0, 2, 4, 6, 10 kg/day) and grazed for a further 63 days. The calves were offered a daily herbage allowance of 60 g dry matter/kg live weight.

Daily weight gain was increased by 59 g for each additional kilogramme of reconstituted milk consumed, and herbage intake per unit live weight decreased by 1–24 g/g milk organic matter consumed, equivalent to a reduction in metabolizable energy intake of 9 kJ. Clear effects of both age and diet upon the consumption of herbage were demonstrated. An explanation of the mechanisms governing intake of herbage in milk–fed calves is offered.

The frequency of natural crossing in 1972 was estimated, in two subsets of a composite cross grown in F6 in Nairn and in Fife, as 2·61±0·25% and 4·59±0·35% respectively. The estimated inbreeding coefficients of the parental generations were less than would be expected if all types of pollination were equally fertile and gave equally fertile offspring.

The follicle ratio S/P and the fibre ratio Sf/Pf have been determined for various post-natal ages of English Romney lambs in six lamb crops.

A maximum site-sampling error has been determined for use in assessing the degree of significance of differences in values of the ratio S/P determined from successive skin samples from individual lambs. Variations encountered in these Romney lambs in the level of their follicle and fibre ratios, in their rates of change and in the degree of their association with live-weight changes show that rigid conclusions based on data from one lamb crop only are not justified. An intensive study of birth and 8-day old samples has shown that follicles may regress in the early post-natal life of the lamb.

Not all follicle anlagen are initiated before birth and the ‘ceiling value’ of the adult ratio Sf/Pf is not necessarily determined or set pre-natally except in the sense of there being a genetic maximum which may or may not be attained. Low restricted follicle and fibre ratios at birth may increase rapidly postnatally and high ratios at birth may increase little, if at all, post-natally. The follicle and fibre ratio may increase even between the ages of 6 and 12 months.

The aim of the present investigation was to determine the effect of adding urea to a diet based on ground maize and dried sugar-beet pulp (2/1) on the composition of duodenal content and diet digestibility in calves.

Two bull calves (140 kg) were provided with duodenal fistulae and pair fed the ration alone or with 1·2% urea in a cross-over design. Lucerne hay was also given. The difference in intake of nitrogen between the two diets was 18·4 g/day.

The results obtained showed negligible differences between the diets in the amounts of dry matter, organic matter and energy disappearing both before and after the duodenum. Digestibility of nitrogen was greater with the urea-containing diet.

Although some of the added urea (25%) was apparently lost from the forestomach, the duodenal digesta contained 13·7 g N/day more with the diet containing urea. Of this a minimum of 6·5 g was in the form of amino acid-N and only 0·4 g as ammonia-N. All the amino acids determined were present in increased amounts but lysine and isoleucine showed smaller relative increases than the other amino acids.

From these results and calculations based on measurements of 2,6-diaminopimelic acid it is suggested that the extra protein in the duodenal content derives from both more efficient bacterial protein synthesis in relation to energy expended and decreased degradation of plant protein in the rumen.

The factorial approach to the determination of the dietary requirements of macroelements is a two-stage process; in the first the net requirements are estimated and in the second, the fractional absorption of the dietary mineral is used to convert net to dietary requirements (Agricultural Research Council, 1965). At the first stage the maintenance component is allotted a fixed value, so that estimated dietary requirements are directly proportional to absorbability of the element.

Nitrogen balance and flow of nitrogen along the gastrointestinal tract were determined in growing wether sheep fed a dried grass pellet diet with or without intraruminal propionic acid infusion. Plasma free amino acid and glucose concentrations tended to be higher in peripheral blood of animals receiving propionate (P < 0·10). Overall total nitrogen and amino acid digestibilities and apparent digestibilities of each fraction along the digestive tract were not affected by infusion of propionic acid. The contribution of microbial amino acids to total amino acid flow in the duodenum measured using purine bases as the microbial marker averaged 0·49 and was not affected by propionic acid infusion. It is suggested that changes in circulating amino acid levels arise from reduced utilization of luminal amino acids by gastrointestinal tissues due to the increased availability of alternative energy-yielding substrates.

The neutron probe (NP) is used widely to measure changes in soil water storage in research and more recently to aid irrigation scheduling. Its accuracy is rarely questioned and most of the relationships between soil water changes and productivity are based on its use. A field experiment was conducted at Cambridge University Farm in 1999 to address whether the NP could accurately measure changes in soil water content (SWC) under irrigation or substantial rain (>10 mm). The experiment was a replicated split-plot design with four irrigation treatments allocated to the main plots, and surface profile (ridge, flat) and crop (potato cv. Saturna, bare soil) treatments allocated to the subplots. The mean results from four NP access tubes per plot installed to measure soil moisture deficit (SMD) across the row-width were analysed. The NP was inconsistent in measuring known irrigation or rainfall input. In relatively dry soil (SMD>40 mm), the NP generally measured 93 to 110% of 18 mm of irrigation within 4 h of irrigation. The NP recorded much less water applied as irrigation in wetter soil, and often only 40 to 70% of the applied irrigation (18 or 36 mm) was measured. There were occasions when the NP did not measure all the water input even when the SMDs before irrigation were greater than the water subsequently applied. Some of the ‘missing’ water might be attributed to drainage, however, results from an additional experiment using an open-topped tank of soil showed that the NP was unable to detect all the water added to the soil, particularly where the water was largely confined close to the soil surface. Replicated measurements of the change in SMD in the field experiment were precise for a given event and treatment (mean S.E. = 1·3 mm) but were not accurate when compared against the input measured in rain gauges. It was concluded, that the NP could not be used reliably to measure changes in soil water storage after irrigation or substantial rain. For periods when there were minimal inputs of water, there was a closer correlation between changes in SMD measured by the NP and those predicted by a modified Penman–Monteith equation than after substantial inputs of water. However, for predicted changes in SMD of c. 20 mm, there was a range of c. ±5 mm in the changes in SMD measured by the neutron probe.

The value of the NP for monitoring SMDs where there is irrigation, or substantial rain, must be seriously doubted. Consequently, its limitations for scheduling irrigation, testing models or quantifying the effects of treatments on crop water use in potatoes must be appreciated, especially where the areal sampling limitations of single access tubes positioned only in the ridge centre have not been addressed.