In exploiting to the full the possible advantages of a synchronized oestrus in ewes, the mating management of the ram requires special attention. Previous recommendations (Gordon, 1963) on ram management stated that progestagen-PMSG synchronized ewes should be run with rams at a ram to ewe ratio of 1:10 in the days following treatment. Preliminary work from this laboratory has shown that delaying the introduction of rams until 48 h following sponge withdrawal could improve conception rates significantly (Joyce, 1972). The purpose of the present experiment was to investigate further the effect of time of ram introduction on ewe fertility following oestrous synchronization.

Results from two trials, in which the effects of genotype, plant density and harvest date on the accumulation of dry matter and the chemical composition and nutritive value of plant components, are presented. Inra 200, LG11, Maris Saffron, Caldera 535, Anjou 210 and White Horse Tooth were established at 5·0, 9·8 and 13·5 plants/m2 in factorially designed experiments.

In vitro digestible organic matter in the dry matter, water-soluble carbohydrates, starch, total nitrogen, acid-detergent fibre, cellulose, lignin, phosphorus, magnesium, potassium, calcium, sodium, zinc, manganese and copper were analysed for the whole crop and plant components.

With the exception of White Horse Tooth, stem yields declined after reaching a peak 2–3 weeks after mid-silk. This was attributed to movement of water-soluble carbohydrates from the stem to the ear, with greater movement being associated with a larger ear component. As a result the in vitro digestible organic matter in the dry matter value of the stem component was greater for crops containing a small proportion of ear. The higher stem digestibility value compensated for the small ear component, with the result that the varying proportions of plant components did not markedly affect whole-crop digestibility prior to ensiling.

The greater deposition of starch in crops with a large ear component caused a significantly more rapid rise in whole-crop D.M. content than in crops with a small ear component.

Acid-detergent fibre and lignin values for the whole crop were much lower than those recorded in the U.S.A. Genotype and plant density had no effect on mineral content but phosphorus and potassium concentrations declined dramatically after frost.

As a nitrogen fertilizer for vegetable production in Britain ammonia has been used mainly for bruasels sprouts (Page, Tatham & Wood, 1974; Page, 1975a; Page, Wood & Case, 1976), and leeks (Page & Williams, 1977). These crops with long growing seasons allow considerable latitude in time of application of the ammonia. Summer and autumn maturing cauliflowers have not only a short growing season, but also have a physiological control of curd formation which appears to be insensitive to nitrogen supply (Salter, 1969; Salter & Fradgley, 1969). They are also usually transplanted into the field, and the root system is therefore restricted for at least part of the growing season. It is therefore desirable to know if the roots would reach the injected nitrogen in time, as, until the ammonia becomes nitrified, nitrogen movement in the soil is small (Page, 19756). Thus, time of application of the ammonia was considered likely to be important.

Forage maize was harvested on three occasions from three genotypes (Inra 200, LG11 and Anjou 210), grown at three plant densities (5·0, 9·8 and 13·5 plants/m2). Three replicate silos were filled with 8 kg fresh crop per treatment, sealed, and stored for 100 days.

Crops from all treatments fermented to give predominantly lactic acid, low values for pH (average 3·9, range 3·7–4·1), with no butyric acid. Apparent loss of watersoluble carbohydrates during storage appeared to be directly related to their content at harvest.

Genotype and plant density had relatively little effect on the composition of the silage, or on digestibility in vitro. Later harvest was reflected in increased contents of dry matter and starch, and in restricted fermentation. The content of digestible organic matter in the D.M. was decreased by later harvest.

The practical value of obtaining estimates of general combining ability (GCA) from data accumulated in a breeding programme has been discussed by Gilbert (1967). In this study use has been made of data collected during the course of screening potato breeding material, derived from Solanum vernei Bitt. et Wittm., for resistance to the white potato cyst nematode, Qlobodera pallida (Stone) Mulvey & Stone, to assess the relative contributions of GCA and specific combining ability (SCA) by the procedure described by England (1974) which is based on Gilbert's (1967) method.

Maize (Anjou 210), a density-sensitive genotype, was established at 5 and 15 plants/m2 and produced crops containing 50 and 26% grain respectively. Prior to ensiling, the high and low grain crops contained 6·9 and 20·4% water-soluble carbohydrates in the dry matter respectively and were reduced to 0·4 and 1·6% of the dry matter in the silage. The high grain silage contained a lower concentration of acid-detergent fibre, cellulose, lignin, cell-wall constituents and organic acids than the low grain silage. These differences were not reflected in the in vitro digestible organic matter in the dry matter values which were similar in both silages.

Two groups of autumn-calving Freisian cows were offered either the high or low grain silage ad libitum as the sole forage plus an 18% crude protein concentrate during a 14-week experimental period. The cows which received the high grain silage produced significantly more milk of a significantly lower milk fat content than the cows which received the low grain silage.

The increased milk production coupled with the smaller loss of water-soluble carbohydrates during ensiling show that a high grain content in forage maize is a desirable attribute. It is suggested that density tolerance should be one of the selection criteria used by plant breeders to allow crops to be established at high plant densities from which near maximum dry-matter yields could be obtained, while still containing a high proportion of grain.

A method is proposed for estimating the percentage of dietary protein that is degraded by microbial action in the rumen when protein supplement is added to a specified ration. The potential degradability, p, is measured by incubating the supplement in artificial-fibre bags in the rumen and is related to incubation time, t, by the equation p = a+b(1 – e-ct). The rate constant k, measuring the passage of the supplement from the rumen to the abomasum, is obtained in a separate experiment in which the supplement is combined with a chromium marker which renders it completely indigestible. The effective percentage degradation, p, of the supplement, allowing for rate of passage, is shown to be p = a+[bc/(c+k)] (1-e-(e+k)t) by time, t, after feeding. As t increases, this tends to the asymptotic value a+bc/(c+k), which therefore provides an estimate of the degradability of the protein supplement under the specified feeding conditions.

The method is illustrated by results obtained with soya-bean meal fed as a supplement to a dried-grass diet for sheep. The incubation measurements showed that 89% of the soya-bean protein disappeared within 24 h and indicated that it was all ultimately degradable with this diet.

When the dried grass was given at a restricted level of feeding the allowance for time of retention in the rumen reduced the estimate of final degradability to 71% (69% within 24 h). With ad libitum feeding there was a faster rate of passage and the final degradability was estimated to be 66% (65% within 24 h).

The incidence of oestrus in pregnant ewes has been reported previously by Williams et al. (1956) and Bichard et al. (1974). However, their investigations were not designed specifically to study such a phenomenon and the number of animals employed was small. None of the factors affecting oestrus occurrence was investigated. Under experimental conditions, vasectomized or aproned rams are sometimes used after the removal of fertile rams to detect embryonic failure in pregnant ewes. It is of interest to check on the validity of this method. This study was carried out to obtain an estimate of the incidence of oestrus in early pregnancy using relatively large numbers of fat-tailed Barki and imported Hungarian Merino ewes and to investigate the effect of year, breed of ewe and age of ewe on its occurrence.

The numbers of viable anaerobic proteolytic bacteria were determined from the caecal fluid of three ponies fed diets based on maize, oats or barley. In anaerobic conditions selected to promote the growth of those bacteria capable of utilizing protein, between 2 × 105 and 8 × 105 of viable anaerobic proteolytic bacteria/ml of caeoal fluid were observed. Time of sampling post feeding did not appear to affect the numbers observed. These numbers would appear adequate to make an important contribution to protein digestion.

Although sheep combat thermal stress mainly by panting, a sizeable amount (40%) of total evaporative heat loss, is from sources other than panting (Hales & Brown, 1974). The frequency of sporadic discharge of sweat glands increases with increase in ambient temperature and is accompanied by a decline in respiration rate (Bligh, 1961). The wool coat can reduce evaporative cooling but sweating may have cooling value in sheep breeds with open fleeces (Rai, Singh & More, 1978). In sheep, the number and size of the sweat glands (Waites & Voglmayr, 1962) and the quantum of sweat production in a particular time period (Ghoshal et al. 1977) varies in different body regions. In view of the possible significance of surface evaporative cooling, thermal sweating in different body regions of sheep was investigated.