THE USE OF SHEEP FITTED WITH OBSOPHAGEAL FISTULAE IN GRAZING STUDIES

Studies were carried out on the effects of diurnal variation, fasting before sampling, and acclimatization to a sward on the chemical composition and in vitro OM digestibility of samples of extrusa collected from sheep fitted with oesophageal fistulae. The N content of extrusa samples increased markedly during the morning, and tended to decline again in the evening. The diurnal changes in digestibility were similar, but the variation was much smaller. There was no significant correlation between either N content or OM digestibility and grazing speed measured in bites per minute. There were no significant changes in either the N content or OM digestibility of successive samples of extrusa collected after over-night fasting, or after the sheep were introduced to a sward to which they were not accustomed, though the concentration of ash in the extrusa was significantly lower when the sheep were hungry than when they were not. The OM digestibility of the diet selected was approximately two units lower on the first two days after introduction to a new sward than the mean value of samples collected over the next 12 days.     

THE DISTRIBUTION OF LEAF AREA AND LIGHT INTENSITY WITHIN WHEAT CROPS DIFFERING IN ROW DIRECTION, ROW SPACING AND RATE OF SOWING; A CONTRIBUTION TO THE STUDY OF UNDERSOWING PASTURE WITH CEREALS

The distribution of leaf area and light intensity within wheat crops differing in row direction, row spacing and rate of sowing is described. Regardless of the manner of planting, 75% of the total leaf area was found within a band 31/2 in. wide, centred on the centre of the row. Light penetration within crops spaced at 14 in. was greater than within those spaced at 7 in. Light penetration within rows running N.–S. was more uniform and higher, particularly around noon, than within rows running E.-W. Within N.-S. rows the position midway between rows received the highest amount of light, but light decreased on either side until it was least beneath the rows. Within E.-W. rows at 14 in. spacing, maximum light was recorded at 101/2 in. on the southern side of a row, decreasing progressively as the row was approached.     

The effect of CCC on the initiation of potato tubers

Summary CCC, when applied to the roots of potato plants sufficiently early, brought forward the time of tuber initiation and growth. An increase in net assimilation rate at the time of rapid tuber growth was found for both CCC treated and control plants.     

THE UTILIZATION OF GRASS FED INDOORS TO YOUNG BEEF CATTLE, WITH OR WITHOUT SUPPLEMENTARY BARLEY

An experiment was carried out in which grass was cut and fed indoors, with or without supplementary barley. Seven animals were allocated to each of the following treatments: (1) grass ad lib . without supplementary barley; (2) grass ad lib . with supplementary barley at the rate of 0.5 lb/100 lb bodyweight; (3) grass ad lib . with supplementary barley at the rate of 1 lb/100 lb bodyweight. Supplementary barley increased total dry-matter intake and improved daily liveweight gain and food conversion rate. The mean daily liveweight gains for the 17-week experimental period were 1.60, 1.91 and 2.20 lb and the corresponding feed dry-matter conversion ratios were 6.18, 5.67 and 5.55 for Treatments 1, 2 and 3, respectively.
The dry-matter digestibility of the diets was slightly higher when the grass was supplemented with barley than when grass alone was given. Although barley depressed the digestibility of protein, the absolute and the proportionate retention of nitrogen was increased. This was particularly marked on Treatment 3, presumably because of the higher net energy value of the diet containing the greater amount of barley. The N-retention data corresponded to the rates of liveweight gain obtained.     

Genetic male sterility in wheat

The occurrence of genetic male sterility and development of highly sterile lines have been reported. The male sterility was not accompanied by any visible chromosomal aberration. It behaved as recessive and was governed by multiple factors. It was hypothesised that three major genes with additive effect were operating to produce highly sterile forms while less sterile forms would be dependent on one or two genes. The expression of male sterility was also influenced by modifying factors and environments.     

Non-random segregation of gene I for Fusarium resistance in the tomato

Significant deviations from the ratios expected, according to the single dominant gene hypothesis for resistance to Fusarium wilt, were found in crosses involving several susceptible and resistant tomato lines. The susceptible class was the deficient one in F₂ and F₃ populations, as well as in backcrosses in which the heterozygotic resistant F₁ served as the male parent. The reciprocal backcross, with the F₁ as the female and the homozygous susceptible as the male, gave segregations better approximating or consistent with the single gene hypothesis. Reciprocal F₁ and F₂ generations did not give any evidence of cytoplasmic effects.The results were interpreted assuming preferential fertilization of ovules by pollen grains carrying the dominant I allele for resistance.The practical implications of the phenomenon of preferential fertilization in breeding for Fusarium resistance are discussed.     

The breeding systems and some interspecific relations of a number of African Trifolium spp.

The breeding systems of 12 species and varieties of Trifolium from Africa were investigated. One annual and the three perennial species were allogamous and self-incompatible, the other annuals were autogamous.The effect of temperature on pollen germination and growth was variable. In some species high temperatures (30°C) adversely affected pollen germination and low temperatures (20°C) in others. A high humidity (93–98% R.H.) was essential for good pollen germination and growth.Approach grafts indicated that these species were closely related, however, this method of grafting may not be as reliable as the cleft graft for assessing species relations. From hybridization attempts between seven species, it appears that some interspecific hybrids may be possible within this group.     

THE EFFECT OF THE BIPYRIDYL HERBICIDES ON HILL COMMUNITIES AND THEIR ROLE IN THE IMPROVEMENT OF HILL GRAZING

The improvement of hill land is important to the national economy of the United Kingdom. An increase in the amount of enclosed productive land results in a greater stock-carrying capacity of a hill farm. Improvement is not always possible by conventional implements, and herbicides are being used to kill the old sward. The bipyridyl herbicides offer a means of destroying or modifying the indigenous vegetation. The application of low doses of paraquat or diquat to an association containing Molinia caerulea, Nardus sfricta and Festuca avina resulted in a change in equilibrium in favour of the fescues. The application of 2 lb paraquat per acre practically eliminates all grass species in a sward and it is then possible to establish desirable pasture species after lightly cultivating the dead surface litter.     

THE DIGESTIBILITY AND PALATAB1LITY OF HIGH-MOISTURE LEGUME SILAGES WITH DIFFERENT CHEMICAL ADDITIVES

The effects of wilting and of various chemical additives on the digestibility and palatability of wet legume silages are reported. These silages showed most of the characteristics associated with the ensiling of wet herbage with a low content of soluble carbohydrate. Digestibility of all silages by wether lambs was low and exhibited little difference that might be attributed to the treatments. The untreated silage or the one sprayed with valeric/isovaleric acid, just before feeding, were more palatable to dairy heifers. Silage consumption was sharply reduced when urea was added during ensiling.