Six field experiments made between 1960 and 1968 determined the effect of previo cropping and manuring on the nitrogen requirement of sugar beet. Three were at Silsoe in Bedfordshire on soils developed over Lower Greensand and Gault Clay and three were at Broom's Barn (Suffolk) on Calcareous Drift soils over chalk. Each experiment lasted 2 years, a preparatory crop followed by sugar beet.

Spring barley and potatoes were treatment crops in all the experiments and winter wheat, a ryegrass ley and barley undersown with trefoil were included in the Suffolk experiments. Nil, 0·6 or 1·2 cwt N/acre was tested on the sugar beet in the first three experiments and 0, 0·5, 1·0 or 1·5 cwt N/acre in later ones.

All the experiments showed that previous cropping influenced the nitrogen requirement of the sugar beet. There was a linear relationship (r = – 0·86) between the amount of fertilizer nitrogen given minus that removed by the preparatory crop, and the quantity of nitrogen fertilizer needed by the sugar beet for maximum sugar yield. Sugar beet grown after barley or potatoes (each given 0·5 cwt N/acre) needed on average 1·0 cwt N/acre at both Broom's Barn and Silsoe for maximum sugar yield. Sugar beet after winter wheat or a ryegrass ley also needed 1·0 cwt N/acre at Broom's Barn. When the previous potato crop was given 1·5 cwt N/acre, 0·5 cwt/acre sufficed for maximum yield of sugar at both centres; also after ploughed-in trefoil, sugar beet needed only 0·5 cwt N/acre.

This paper reviews extensive work at Jealott's Hill and elsewhere in England and Wales on the agronomic effects of including various levels of urea in 2:1:1 NPK fertilizers combine-drilled with spring cereals.

Little evidence of phytotoxicity was found with fertilizers containing up to 12% urea and providing about 0·6 cwt N/acre. The inclusion of 20% urea reduced braird more frequently on soils of high pH than did lower proportions although grain yields were seldom affected adversely. Such soils are not uncommon, especially in the barleygrowing areas of Southern and Eastern England, where perhaps a quarter of the cereal acreage may be located on soils of pH 7·7 and above.

Analyses of cow urine showed that about 10% of housed cows excreted phosphate greatly in excess of ‘normal’. The phosphaturia only occurred when the cows were permanently housed. No high phosphate concentrations were found in. urines from grazing cows although a significant increase in phosphate concentrations occurred when these cows were temporarily transferred to housed conditions.

No significant differences were detected between the high and low phosphate excreting cows with respect of urinary concentrations of creatinine, calcium, or chloride, urine specific gravity or pH, or plasma concentrations of calcium, inorganic phosphate, magnesium, sodium, potassium, alkaline phosphatase, chloride or bicarbonate.

Complete phosphorus balance measurements on four cows during the last six weeks of pregnancy showed that an increase in urinary phosphate excretion occurred in both high- and low-phosphate excreting cows when a dietary 'steaming-up' schedule was employed, and that the phosphaturia was accompanied by an increase in absorption of dietary phosphorus.

The cause of the phosphaturia does not appear to be acidosis. Little change in urinary phosphorus excretion occurred after oral doses of ammonium chloride but some increase occurred after equivalent doses of sodium and potassium carbonates. It is concluded that a small proportion of cows have a tendency to excrete relatively large amounts of phosphorus in the urine but that this only occurs under housed conditions.

A study was made of the effects of supplementing low-protein teff (Eragrostis tef) hay with (a) protein (egg albumin), (b) urea and (c) urea plus C4 and C5 branched-chain volatile fatty acids (VFA) on the cellulolytic flora in the rumen of sheep conditioned to these diets and on the digestibility of cellulose and hemicellulose. Addition of urea, as opposed to no supplementation, increased voluntary hay intake and the percentage digestibility of cellulose and hemicellulose, while counts of cellulolytic bacteria were not greatly affected. The proportion of ruminococci amongst the cellulolytic bacteria increased somewhat and that of the butyrivibrios decreased. When branched-chain VFA were added to the hay together with urea the numbers of cellulolytic bacteria per g rumen ingesta and the proportion of ruminococci increased over those for urea alone. This was accompanied by a further increase in voluntary hay intake. Percentage digestibilities of cellulose and hemicellulose were similar to those for the urea/hay diet. Supplementation with protein resulted in lower digestibility of α-cellulose and hemicellulose when compared with the urea-supplemented diets. The cellulolytic bacteria formed a lower percentage of the ‘total culturable’ counts than was the case for the other diets.

Of 120 mature Merino ewes, balanced groups received the following treatments from days 8 to 15 after fertile mating: 1, submaintenance nutrition plus 10 mg/day progesterone; 2, submaintenance without progesterone; 3, maintenance nutrition plus progesterone as above; 4, maintenance nutrition without progesterone.

The ewes were in light condition, they lost some weight before mating, they had an ovulation rate of 108·3% and they barely maintained their mating weight during the first 3 months of pregnancy. The percentages of ova shed not represented by lambs at term were 60·6, 58·1, 48·5 and 62·5 for groups 1–4 respectively. There were no significant treatment differences or interactions.

The high overall loss of ova could have been due in part to depressed fertilization rate: however, the general environmental conditions and low body weight of the ewes seems likely to have made an important contribution to the high basal loss. There was a significant regression of prenatal mortality on body weight at mating, but no detectable relationship between prenatal mortality and condition score.

Sixteen oestrous cycles of over 21 days were distributed through all groups, indicating that considerable mortality occurred after day 13.

Mature Merino ewes (108) which had been hand-mated to fertile rams received the following treatments: 1, submaintenance nutrition days 7–14 (34 ewes); 2, submaintenance nutrition days 20–27 (40 ewes); 3, control (34 ewes).

The ewes were in fat condition, and gained weight before mating and throughout pregnancy except when on the submaintenance treatment. Their overall ovulation rate was 180·6%. The percentages of ova not represented by lambs at term were 30·6, 37·5 and 41·0 for groups 1–3 respectively, the differences being non-significant.

Loss of ova in multiple ovulators was not significantly different from that in single ovulators and there was no relationship between body weight and prenatal loss. Nine post-mating oestrous cycles longer than 21 days were distributed through all groups in a pattern which bore no apparent relationship to nutritionally-induced embryo mortality. A higher proportion of ewes remained barren when re-mated after long than after normal-length oestrous cycles.

Three groups of mature Merino ewes, balanced for body weight and number of ovulations, and totalling 122 animals, received the following treatments subsequent to mating to fertile rams: 1. approximately half maintenance requirements from day 7 to 37; 2. approximately half maintenance requirements from day 7 to 37, plus 10 mg progesterone daily from day 20 to 37; 3. control.

The ewes, which were in fat condition, had a mean ovulation rate of 121·3 %; except during the submaintenance period, they gained weight throughout pregnancy.

The percentages of ova not represented by lambs at term were 34·7, 46·0 and 42·6 in groups 1 to 3 respectively, the differences being non-significant. Detailed examination of the cycle length data of ewes returning to service suggests that some embryos may have been killed by the submaintenance treatment. Progesterone treatment was not beneficial, nor did its sudden withdrawal on day 37 appear to be detrimental to foetal survival. In a sample of ewes slaughtered on day 37, adrenal gland weights were significantly lower in the two treated groups.

Significantly higher losses of ova occurred among twin than among single ovulators and there was some evidence that this was non-random. There was no significant relationship between prenatal mortality and body weight at mating.

Collation and re-analysis of the results obtained in separate experiments investigating prenatal mortality in Merino ewes over a period of 4 years have made it possible to draw the following general conclusions:

Data from the control groups indicated that in 3 out of 4 years basal prenatal loss averaged approximately 25%, which agrees with a number of other estimates in the literature. Higher losses of ova in 1965 than in the other 3 years could not be partitioned accurately between fertilization failure and prenatal mortality.

Submaintenance nutrition apparently caused embryo mortality in 1964, and possibly in 1967, when underfeeding from day 7 to 37 was followed by an unusual number of long cycles; however, there was no evidence of increased mortality in 1965 and 1966.

Losses of ova shed as twins were significantly greater than amongst those shed as singles in 1964 and 1967. The higher loss of twin ova was clearly associated with the treated groups in 1964.

In each of the 4 years the left ovary produced more ova than the right, and when the 4 years' data were combined, survival of ova shed by the left ovary was significantly better than of those shed by the right. The type of twin ovulation, i.e. whether the two ova came from one ovary or two, had no consistent effect on prenatal mortality.

In 3 years there was no significant regression of prenatal mortality on body weight at mating. However, in 1965, when body weights were relatively low, there was a significantly negative regression. It is possible that there is a critical body weight below which poorer prenatal survival can be expected.

Ewes which suffered embryonic loss followed by a delayed return to service subsequently conceived less readily than those having a cycle of normal length following fertilization failure or early embryonic death. It is postulated that in some cases this may be because ovulation occurs while resorption is still incomplete. For some ewes having long cycles after embryonic death, anoestrus or removal of the fertile rams precluded subsequent conception in that season. This was an added reason for the season's lambing performance of ‘long cycle’ ewes being much worse than that of ewes re-mated after normal length cycles.

Kendall (1948) suggested that the ability of cattle to thrive in tropical regions could be better indicated by the diurnal variation in body temperature rather than actual body temperature. However, Bligh & Lampkin (1965) found little difference in the nychthemeral variation in deep-body temperature of East African Zebus and Herefords grazing under conditions where the atmospheric shade temperature varied from 71 to 40 °F.