There is considerable confusion in some lactation studies as to the meaning of the term milk yield. Furthermore, the various fractions of milk yield are ill defined. This note proposes a standardization of terminology on this subject. The problem is general and applies to all mammals. We will discuss it, however, in terms of the dairy sheep, the animal with which we are most familiar.

Experiments are described in which the relative importance of head storage capacity and carbohydrate supply was examined in five sorghum varieties of different heights. The varieties were: Namatera (270 cm), Dobbs (180 cm), MUS 78 (100 cm), MUS 23 (85 cm) and MUS 70 (85 cm). Techniques used were (i) cutting off part of the head or part of the leaf at anthesis, (ii) shading during different periods of development, and (iii) thinning the plants at different physiological stages. Varietal differences ranged from a situation where the head was little more than half-filled by the available carbohydrate (MUS 78), through intermediate stages (Dobbs and Namatera), to a situation where the head capacity limited the amount of carbohydrate which could be stored (MUS 23 and MUS 70). Some differences could be attributed to pre-anthesis competition between head and stem, but in the dwarfs a more important factor appeared to be pre-anthesis competition between head and leaf. It is suggested that for maximum efficiency of grain-yield production, maximum carbohydrate should be utilized for pre-anthesis head and leaf growth and that partitioning between these plant parts should be such that the supply of carbohydrate for grain filling is in balance with head storage capacity.

Contour diagrams, computed from analyses of soil around bands of aqueous ammonia injected under grass, show the distribution of both NH4-N and nitrifying bacteria.

When applied at 155 kg NH3-N/ha, either as 4·7 or 9·3 g N/m of injection slit, using knives spaced either 30 or 60 cm apart, aqueous NH3 was recovered and nitrified more slowly in the bands 60 cm apart. Cumulative yields of grass after 32 weeks were the same (715 ±30 g/m2) from plots injected at either spacing but growth was more even throughout the season from slits 60 cm apart.

I.C.I. 79,939, a potent analogue of prostaglandin F2a, was used to induce and synchronize parturition in seven gilts and three sows. A total dose of up to 750 μg injected intra-muscularly during a treatment period of about 24 h on days 109–111 of gestation induced parturition approximately 26 h after the start of treatment. The length of gestation, which was 114 ± 0·2 days in 147 normal untreated pigs, was significantly reduced to 111 ± 0·2 days (P < 0·01) in ten pigs in the same herd treated with I.C.I. 79,939. In this trial, no side-effects were detected, the average birth and 3-week weights of piglets were within the normal range, and sows usually returned to normal oestrus within a week after weaning.

Observations made on freezing tissue show that the appearance of extracellular freezing can occur in tissues which have been initially frozen intracellularly. Since the evidence for the assumption that intracellular freezing is of rare occurrence in the field is based on the microscopical observation of ‘naturally’ frozen tissue it can no longer be assumed that this process is unconnected with the survival of plants overwintering in the field.

The progestagen concentration of milk was measured in cows, at various times of the reproductive cycle by a competitive protein binding procedure and by radioimmunoassay. The apparent progesterone concentration was found to be significantly greater in milk (P <0–05) than in plasma, probably due to the presence of an unidentified metabolite(s). A simple, rapid radioimmunoassay was developed to measure directly the progestagen concentration in milk. A mean concentration of about 1 ng/ml at oestrus (or mating) increased, 20–24 days later, to 3–4 ng/ml in cows subsequently found to be non-pregnant and to about 7 ng/ml in pregnant animals. The possible application of this analytical procedure as the basis of a method of pregnancy diagnosis is discussed.

Two dormant varieties of rice were harvested three times at intervals of 7 days after grain development and the seeds were subjected to different sunning and controlled humidity storage treatments. Germination percentages and moisture contents of the grains were recorded at intervals of seven days after harvest.

It was noted that the dormancy of the dormant rice seeds was broken early when the seeds were subjected to continuous sunning from sunrise to sunset, followed by the treatment where the seeds were preserved under 0 % humidity conditions at room temperature. There was no break of dormancy of rice seeds when the seeds were preserved under 94 % humidity conditions.

It was further noted that when the age of the seeds at the time of a germination test remained the same, the earlier the harvest, the earlier was the break of dormancy; and when the lapse of time after harvest remained the same at the time of a germination test, the later the harvest, the better was the germination.

It is suggested that dryness of the seeds helps in the early break of dormancy and wetness retards or completely stops the dormancy-breaking reactions. On drying, the kernels of rice seeds shrink in volume more than the glume covers resulting in an air-space between the glumes and the kernels. This air-space helps air-diffusion in and out of the seeds, resulting in quicker oxidation-reaction processes or possibly embryo respiration, and consequently the dormancy is broken early. Increase in temperature accelerates such reactions. It is further suggested that the dormancy of rice seeds depends on the interactions between the ‘embryo-sensitivity to inhibitors’ and the ‘state of oxidation-reaction processes’ inside the seeds.

Magnesium deficiencies have occurred on most crops grown on sandy soil of the Cottenham Series at Woburn (Bolton & Penny, 1968). This paper gives the results of an experiment on this soil comparing the relative effects of dolomite (MgCO3. CaCO3), Epsom salt (MgSO4. 7H2O) with and without limestone (CaCO8), and calcined magnesite (MgO) on the yields and composition of sugar beet, potatoes and spring wheat grown in successive years. Effects on soil composition are also given.

Three soil types – Pugwash sandy clay loam, Woodburn gravelly loam and Kirkhill silt loam – were compared by response to fertility treatments over two cycles of a 4-year rotation of 1 -year oats (AvenasativaL.) and 3 years of a grass-legume mixture for hay production. A rotation was started each year on a new section of the experimental site during the first rotation so that all crops were being grown in any one year. Treatments were: N; 0, 56, 112 kg/ha for the first rotation, 0, 168 and 336 kg/ha for the second rotation; P2O5; 0, 84, 168 kg/ha, first rotation, 0, 252 and 504 kg/ha, second rotation; K2O; 0, 67, 134 kg/ha, first rotation, 0, 252 and 504 kg/ha, second rotation. Manure was applied at 0 and 22 t/ha. There was a significant difference in yield for the three soil types for first-, second- and third-year hay crops. Manure increased yield of all hay crops on all three soils, and oat yields on Woodburn and Kirkhill soils. There were varying responses to rates of application of individual nutrients on different soil types. Percentage of species in the hay stands varied between soil types and between years. The differences found between soil types support the basic reason for classifying and mapping soils.

Honeybees were able to distinguish between the flowers of two different oultivars of kale grown to produce hybrid seed and most foraged only on one or other of them.

Energy balances have been determined, using the comparative slaughter procedure, over 3-week periods on groups of laying hens kept at ambient temperatures of 7·2, 15·6, 23·9, 29·4 and 35 °C.

Energy intake declined as the environment became warmer (kcal ME/kg¾/day = 203· 1·13°C); heat production, as measured by the difference between energy intake and energy retention, also declined with increasing ambient temperature (kcal/kg¾/day = 151 – 1·11°C). There was a linear relationship between heat production and ambient temperature with no thermoneutral zone or critical temperature.

The energy available for egg production remained almost constant at 50 kcal/kg¾/day equivalent to a rate of egg production of 82% at each ambient temperature.

The effects of two, symmetrically opposing, light treatments on the semen of Suffolk rams were investigated over two years. The light rhythm had an amplitude of 12 h and a cycle of 24 weeks. Data on semen volume, spermatozoa concentration, total spermatozoa per ejaculate, fructose concentration, seminal fluid fructose concentration and total fructose were collected during 38 semen collection periods. During the last 20 periods libido was assessed on the interval to mounting.

The effects of treatments were assessed by fitting Fourier curves with 24-week cycles to the observed fluctuation of the differences between treatments and with 52-week cycles to the means of treatments. From periodic regression analysis of the treatment differences it is concluded that the Suffolk rams were susceptible to the artificial light rhythms and that both groups adapted to the imposed rhythms. Some effects of the pretreatment photic environment appeared to persist during the first year of the treatment period. There appeared to be a lag between the fluctuations of the semen attributes resulting in a series of sequential changes.

Previous studies on the Scottish Blackface breed have shown that ovulation rate and lambing performance are closely related to body condition at mating. Ovulation rates greater than two were achieved from ewes in good body condition (grade 3·0 on a scoring system described by Russel, Doney & Gunn, 1969) and this performance was not affected by condition either rising or falling to the pre-determined grade at mating (Gunn, Doney & Russel, 1969). Ewes in lower body condition at mating (described by grades 1·5, 2·0 and 2·5) were found to have correspondingly lower mean ovulation rates (Gunn et al. 1969; R. G. Gunn and J. M. Doney, unpublished). In these, and other experiments giving similar results, the experimentally controlled changes in nutrition and hence body condition were imposed for only a few weeks prior to mating, i.e. during late October and November. However, in traditional hill grazing systems, ewe recovery may be expected earlier and may be followed by a considerably longer period of live-weight and condition maintenance. In situations where some degree of grazing control can be used to modify the nutrient intake cycle, it is important to know if food consumption and subsequent reproductive performance can be influenced by the long-term pattern of recovery.