The grain yield, head structure and components of yield of a Nigerian long-season sorghum (Farafara) and an American hybrid short-season type (NK 300) were compared at three populations. The effect of thinning at initiation and at heading was also examined.

At each population, the grain yield per plant of NK 300 was larger than that of Farafara, mainly due to differences in the number of grains per head. This factor was also the main one responsible for a decline in yield per plant with increase in population. At all populations, Farafara plants showed an appreciable increase in stem weight after heading.

The results from the thinning treatments suggest that the main difference between the two varieties is in the number of spikelets present at head emergence: the number and/or potential size of developing grains in Farafara appeared to be largely determined by the time of initiation and was probably too small to accept all the currently produced assimilate.

In a factorial experiment, two protein concentrations and three patterns of feeding were administered to eighteen Large White × Wessex sows (three per treatment) in their second pregnancy. Treatments were repeated in their third pregnancy, when balance trials were conducted. The high protein diet (HP) (19·5% crude protein) contained 15% white-fish meal. The low protein diet (LP) (10·5% crude protein) contained protein of vegetable origin only. The pattern treatments involved intakes of 1·8 kg (L) 2·7 kg (C) and 3·6 kg (H) per day, the three pregnancy feeding patterns being HL, C and LH. Parturition results and lactation performance in the third reproductive cycle were similar to those recorded in the previous reproductive cycle (Pike & Boaz, 1969) reported earlier. Nitrogen retention in the third pregnancy was significantly higher in the HP sows(1606 g N)thaninthe LP sows(1082 g N) (P < 0·001). Intra-uterine nitrogen deposition in pregnancy was not affected by any of the treatments. Extra-uterine nitrogen deposition was significantly greater in the HP than the LP sows (P < 0·001). Dietary protein differences influenced extra-uterine rather than intra-uterine deposition of nitrogen in the pregnant sow, greater extra-uterine nitrogen deposition appearing to enhance subsequent lactation in this and the previous (Pike & Boaz, 1969) experiment. Protein utilization was more efficient in late than early pregnancy, suggesting that the feeding of higher levels of protein in late pregnancy should lead to greater efficiency over the whole pregnancy, provided energy intake is sufficient to promote optimum protein utilization.

An investigation on the different environmental and genetic causes of variation in the birth weight of Black Bengal goats was conducted at the Central Livestock Research-cum-Breeding Station, Haringhata, India. The data consisted of 1375 birth weight records of kids from 284 does and 20 bucks during the period from 1955 to 1961. The goats were maintained under standard farm management throughout the period.

Year had significant effect on birth weight, while the effect of season was insignificant. The interaction was, however, significant. Male kids were significantly heavier at birth than the females. Age of dam and litter size also caused significant variation in birth weight of kids.

From paternal half-sib analysis the heritability of birth weight was estimated to be 0·01. Full sib and maternal half sib analyses estimated the maternal environment common to litter mates to account for 60 % of the variance, out of which 25 % were due to permanent differences between dams. The remaining 39 % were attributed to individual environment, including most of the non-additive genetic variance. The heritability of maternal environment was estimated to be 0·2.

The partial correlation coefficient between birth weight of kids and post-kidding body weight of their dam, independent of litter size and age of dam, was 0·175. Thus, body size of dam, as indicated by post kidding body weight, did not reveal much information about maternal environment.

Three experiments on the effects of sugars on milk production and live weight of cows are described. Two experiments each with twelve cows were of latin square design with 5-week periods. The third was a continuous treatment experiment of 11 weeks duration with twenty cows. All the animals were in mid-lactation. Performance on the basal diet of hay and concentrates was compared to that when the basal diet was supplemented with 10·7 Meal digestible energy daily in the form of sucrose or glucose monohydrate or concentrates.

Additional concentrates regularly increased milk yield, live-weight gain, solids-not-fat content of the milk, and yields of solids-not-fat and milk fat. Fat content of the milk was not affected.

Sucrose had a small beneficial effect on milk yield; the effect of glucose monohydrate on yield was small and indecisive. Sucrose depressed milk fat percentage; the effect of glucose on milk fat percentage varied between experiments. Both sugars increased solids-not-fat content of the milk, solids-not-fat yield, and rate of live-weight gain.

Over the longer treatment period in the third experiment milk fat content tended to recover partially for both sugar-supplemented rations. The effects on yield of milk and of milk fat did not alter. The effects on live-weight gain were established more decisively and the final order of the size of the beneficial effect of the supplements was: concentrates, glucose monohydrate, sucrose.

At the end of the third experiment rumen, contents from all cows were sampled by stomach tube. The concentrates supplement had no effect on the proportions of volatile fatty acids. Both sugars depressed the proportion of acetic acid and increased the proportions of propionic, butyric and valeric acids. In all cases except that of butyric acid, where the reverse occurred, the effect of sucrose was greater than that of glucose monohydrate.

Groups of lactating dairy cows were fed on grass which had received various amounts of nitrogen and potash fertilizers. In the early part of the season not only was the herbage concentration of calcium and phosphorus lower in grass which had received potash fertilizer but in addition the ‘availability’ of the calcium to cows was depressed. Grass which had received large amounts of nitrogen fertilizer had a comparatively low dry-matter content in the autumn. Cows fed such grass were in negative balance for calcium at this time. As expected high dietary potassium gave rise to high excretion of potassium in the urine which in turn was correlated with high excretion of magnesium. These various factors are likely to affect the incidence of metabolic disease.

Thirty-six Border Leicester x Scottish Blackface ewes were separated from their lambs after approximately 12 weeks lactation and brought indoors. They were allocated at random to nine dietary treatments comprising three dietary ratios of chopped roughage to concentrate, each offered at three levels of feeding. During the course of the experiment digestibility and nitrogen balance trials were carried out using three ewes from each dietary treatment.

The daily nitrogen intakes required for nitrogen equilibrium were calculated from the regressions of nitrogen intake on nitrogen retained for each of the three ratios. The intakes increased from 0·47 g/kg W0·75 on the diet containing the lowest proportion of roughage to 0·59 g/kg W0·75 on the diet containing the highest proportion of roughage. The corresponding digestible organic matter intakes did not differ significantly from the pooled value of 18·8 g/kg W0·75.

The daily digestible organic matter intakes required for the maintenance of live weight on the three ratios did not differ significantly from the pooled estimate of 26·9 g/kg W0·75 which is in close agreement with other published results. The nitrogen intakes required for the maintenance of live weight increased from 0·70 on the diet containing the lowest proportion of roughage to 0·84 g/kg W0·75/day on the diet containing the highest proportion of roughage.

The coefficients for live-weight change in the regression equations relating digestible organic matter to live weight and live-weight change for each ratio did not differ significantly from the pooled estimate of 2·0 g DOMI/g live-weight change.

The significance of the results are discussed in relation, to the nutritional status of the ewe and other research findings.

The relationships between the cellulose-lignin complex, voluntary consumption and dry-matter digestibility were examined using forages of two varieties of Italian ryegrass and two legumes, lucerne and sainfoin. These forages had previously been shown to exhibit different intake-digestibility relationships. The cellulose, acid detergent lignin and acid detergent fibre contents of these forages as well as their digestibility coefficients were determined. Lignins were extracted from the fibre fractions and their ultraviolet difference spectra determined.

Changes in maturity of a forage during a single growth phase, produced changes in dry-matter digestibility which were closely associated with changes in the digestibility of the cellulose and inversely related to the lignin content of the forage. Differences in digestibility between varieties of forage were less closely associated with lignin content. As the grasses matured a lignin fraction forming a difference peak at 350 mμ became evident and this was associated with decreased cellulose digestibility.

Differences in voluntary food consumption resulting from changes in maturity of a single forage variety, in one growth phase, were also closely correlated with both dry matter and cellulose digestibility and inversely with lignin content. Differences between varieties and growth phases of the ryegrasses and between grasses and legumes were related less to the nature of the cellulose-lignin complex and more closely to the percentage of the total digesta deriving from cellulose.

Sainfoin was characterized by the formation post-ruminally of an artifact that analysed quantitatively as lignin and qualitatively resembled a non-conjugated phenolic lignin fraction. The production of this artifact apparently disturbed fibre digestibility estimates and may have affected dry-matter digestibility estimates. Degradation of lignin apparently occurred both in the rumen and in the hind gut.

A series of twenty-one nitrogen fertilizer rates ranging from 0 to 800 lb nitrogen/acre (897 kg/ha)/annum was applied on a pure S. 23 perennial ryegrass sward and on an S. 23 ryegrass sward containing S. 100 white clover. Total yields of herbage dry matter and crude protein from both swards at all the nitrogen rates were determined each year by cutting the herbage five times at approximately the same stage of growth on each occasion. Four-parameter growth curves relating herbage yield to nitrogen rate were fitted to the data, and are presented for the first 3 years of the experiment. On the pure-grass sward the response of dry-matter yield to nitrogen rate was almost linear between the 0 and 300 lb nitrogen/acre (336 kg/ha) rates, then it decreased steadily, becoming non-significant about the 500 lb/acre (560 kg/ha) rate. In contrast the response of crude-protein yield was virtually linear from the 0 to the 600–700 lb nitrogen/acre (673–785 kg/ha) rates. The inclusion of white clover in the sward increased the yields of dry matter and crude protein at the low nitrogen rates, but decreased the responses, with the result that the yields and responses of the grass + clover sward were not significantly different from those of the pure-grass sward at nitrogen rates above about 300 lb/ acre (336 kg/ha). In terms of profitability at present fertilizer prices the optimum nitrogen rate for dry-matter production on both swards was estimated to be 400–450 lb/ acre (448–504 kg/ha), whereas that for crude-protein production was greater than 600 lb/acre (673 kg/ha). The value of clover in a sward receiving nitrogen fertilizer is discussed.

Statistical analyses were carried out on the data obtained, under strictly controlled conditions in metabolism stalls, from 219 adult non-pregnant dry cows fed on seventyone different rations. The authors have calculated and studied the correlations between total water intake, faecal and urinary water losses, absorbed and available water, and the seventy-five other factors which were analysed in each of the seventy-one rations. Total water intake closely correlated with the dry-matter intake and also with the dry-matter content of the diet; forages with high moisture content enhance the total water intake which is also significantly correlated to the intake of nitrogen, fat and some mineral elements.

Total water intake closely correlated with the dry-matter intake and also with the dry-matter content of the diet; forages with high moisture content enhance the total water intake which is also significantly correlated to the intake of nitrogen, fat and some mineral elements.

Faecal water losses are strongly correlated with the dry-matter intake and on the faecal dry matter. Moisture content of the diet has no significant effect but increasing pentosans and crude-fibre intake enhance the losses.

Urinary water excretion is closely related to the amount of absorbed water and to the dry-matter content of the diet; a highly significant correlation also exists between urinary water and urinary nitrogen and potassium. The amount of water excreted in the urine may affect the utilization of digestible nitrogen and potassium.

Available water is increased logarithmically when total water intake rises arithmetically. Feeds with high moisture content thus enhance the amount of available water.

A breeding programme initiated at Oak Park, Carlow, in September 1965, in which perennial ryegrass plants, instead of being widely spaced as traditionally used in grassbreeding, were planted 9 x 9 in apart, is described. At this density, plants were individually distinguishable throughout three growing seasons yet gave a complete ground cover of herbage on which was imposed two contrasting systems of defoliation. Data on ear emergence, dry-matter yields, persistence and some quality components agreed with data obtained from swards by other workers.

Animals reared in constant ambient temperatures had significantly more skeletal muscle myoglobin than those reared in alternating temperature environments when the humidity was moderate or high. These differences did not exist when humidity levels were low. Comparisons ofthe effect of humidity level in constant ambient temperatures revealed high myoglobin in pigs subjected to moderate as compared to low humidity at 27°C, but humidity effects were nonexistent when the ambient temperature was 21 or 32° C. It is postulated that animals reared in alternating temperatures experienced intermittent and persistent development of tissue hypoxia and, asa consequence, had reduced aerobic metabolic pathways in muscle as compared to animals rearedinconstant ambient temperatures.

The effect of nitrogen fertilizer on the yield of sugar beet was tested in 170 experiments done between 1957 and 1966; results of 88 experiments, some testing five and six amounts of N, have not previously been published.

On most sites, nitrogen increased sugar yields sharply and almost linearly up to an optimum beyond which yield changed little or decreased only slightly up to 1·8 cwt N/acre, the largest amount tested. In the two series of experiments giving most information, the mean increase from sub-optimal amounts of N was 2·5 cwt sugar/0·1 cwt N/acre.

Usually 0·4–0·8 cwt N/acre was enough for maximum yield; more was needed on a few sites and on about a fifth of them nitrogen fertilizer was not needed. In 7 of the 10 years, the average optimum was 0·6–0·8 cwt N/acre; less was needed in the other years, the driest three years of the decade.

In most, though not all, years, site-to-site differences in response between 0·9 and 1·8 cwt N/acre were no greater than could be expected from experimental error alone; much of the apparent difference in response between seasons were also attributable to this source.

After taking account of experimental error, there were substantial between-site differences in response to amounts of N up to 0·9 cwt/acre, but attempts to explain them in terms of weather, soil and husbandry factors had little success. There was slight evidence of diminished responses to N where sugar beet followed crops other than cereals, and of responses somewhat greater than average on Chalky Boulder Clay soils of the Hanslope and Stretham Series; no other relationships were large or consistent enough to be useful for prediction.

As between-site differences in response are largely unpredictable, and because a grower risks much greater crop losses by applying too little N than by applying too much, the recommended dressing is 1·0 cwt N/acre, substantially more than is needed, on the average, to obtain maximum yield. More N should be given on soils of the Hanslope and Stretham Series and on light sands poor in organic matter; less need be applied where crop residues are likely to supply much nitrogen.

Moisture content of the coats of cattle, expressed as the percentage of the dry weight of hair, has been measured in a wide variety of environmental conditions in summer, springand winter. Strips of coat were clipped from 25 Jersey, 15 Zebu x Jersey crossbred and 9 Hereford heifers in a shed, in a climate room under warm, hot dry and hot humid conditions and outdoors both in sun and shade. Moisture content, weight of coat per unit area, depth of coat, skin and rectal temperatures, sweating and respiratory rates, air temperatures and vapour pressures were measured.

The mean moisture content of the coats varied in the different environments from 5·8 to 27·5 % and mean sweating rates from 28 to 438 g m-2 h-1. Moisturein summer coats out of doors in the sun averaged 11·2% and was about the same as that outof doors in the shade. In the shed, coat moisture was also low (average 11·8%) and amounted to less than half of the moisture content of clipped hair in equilibrium with a near saturated atmosphere. Herefords that had been fed a low plane ration from winter to summer, retained their long winter coats and these, in summer, had only half the moisture content of the short coats of normally fed Herefords. In the hot room, the moisture content of summer coats was usually higher than out of doors and varied around 18%.

The inner part of the coat had more moisture than the outer part and estimates of moisture gradients were made. Calculation of the contribution of sweating to total moisture in indoor environments showed that, at rapid rates of sweating, it was about 8% and was higher in winter andspring coats than in summer coats (Fig. 3). It was estimated that sun and wind reduced the moisture content of summer coats by about 3% in outdoor summer environments. The effect of sun and wind on moisture content of winter coats in the same environment was estimated at nearly 9%.

The results suggest that the site of evaporation was at the skin except in very hot humid indoor environments when some free moisture may have been present in the hair.

The in vitro cellulose digestibility of thirteen cuts of perennial ryegrass, cocksfoot and two varieties of Rhodes grass was determined under different conditions. Cellulose digestibility was increased by increasing the length of the incubation period (1,2 and 6 days), the fineness of grinding of the samples and by addition of a supplement. The effects of fineness of grinding and of supplement were greatest after incubation for 1 day and least after 6 days. Between-run variation in cellulose digestibility was reduced by the supplement and by increasing the length of the incubation period.

In a comparison of different methods of predicting in vivo organic matter digestibility the lowest residual standard deviation ( ± 2·29) was with in vitro organic matter digestibility (1 mm screen and incubated with supplement for 2 days). Other residual errors were: in vitro cellulose digestibility ± 2·40, pepsin-soluble organic matter ± 4·93, total available carbohydrate ± 6·39, cellulose ± 6·40 and nitrogen ± 6·46.

Two changeover experiments, each on eight buffalo heifers, were conducted in two different years to determine the effect of wilting lucerne herbage (Exps. 1 and 2) and berseem herbage (Exp. 2 only) on voluntary dry-matter intake. The dry-matter content of the herbages increased by field wilting from 27 to 50 and from 26 to 44% for lucerne in Exps. 1 and 2 respectively, and from 21 to 31% for berseem. The drymatter intake, nutrient digestibility coefficients, nutritive value index and retention time of undigested residues were determined for each fresh and wilted herbage.

Wilting increased the dry-matter intake of lucerne from 2·3 to 2·8 and from 2·1 to 3·5 kg per 100 kg body weight in Exps. 1 and 2 respectively. Berseem dry-matter intake was increased from 2·2 to 3·1 kg per 100 kg body weight. Digestibility coefficients of all nutrients of both herbages increased by 6–20%. Retention times were unaffected by wilting. The nutritive value indices for lucerne and berseem in Exp. 2 increased by 160 and 60% respectively. In Exp. 2, the average loss of herbage dry matter due to wilting was 3·8%. The higher consumption of the wilted herbages is ascribed to their lower water content. The practical implications of these results are discussed.

Yield (or other variate) values from crops recurring on the same plots in long-term experiments are subject to correlations known as serial plot correlations. Neglect of these plot correlations can result in loss of efficiency in the estimation of treatment effects and bias in the estimation of error.

Serial plot correlations are calculated from 12 experiments on arable crops in England and Wales, for yields 4, 6 or 8 years apart. They are usually positive, with average value 0·2. In one set of experiments the losses in efficiency caused by plot correlations of this magnitude are shown to be small, but some of the biases in the estimates of error are large. Biases in the variances of treatment means can be wholly or partly eliminated by separating two components of error, plot error and plot x year error.

The intravenous (i.v.) infusion of solutions of ammonium salts into sheep produced a toxic condition in which the clinical signs, pathological findings and concentrations of ammonia in the venous blood were comparable with those found in urea poisoning, provided that the urea and ammonia toxicoses were induced over similar time intervals. Our results indicate that urea toxicosis in ruminants is due to the toxic effects of ammonia. Although the clinical signs resulting from the i.v. infusion of ammonium chloride, acetate and hydroxide showed some relationship to the basicity of the compounds, alkalosis did not appear to be a necessary prerequisite for ammonia toxicosis.

The tolerances of sheep to orally administered urea and i.v. infused ammonium salt solutionswere shown to be positively related to dietary nitrogen intake. These results and the observations reported by Payne & Morris (1969) that the concentrations of urea-cycle enzymes per unit of liver tissue were markedly affected by dietary nitrogen intake suggest that supplementation of ruminants grazing low-protein pastures with urea, occurs at a time when their tolerances to an over-dose of urea are minimal.

The i.v. administration of arginine and of y-amino butyric acid plus glucose did not appear to be of practical value in preventing urea poisoning.

Higher pH values had been established under grass than under clover pastures during a prior pasture phase. The differential effect of pasture species on the pH of the subsequently cultivated soil was reduced in time, but continued to be significant after 4 years.

There was greater cation exchange capacity and lower percentage base saturation after clovers than after grasses. The cation exchange capacity of the inorganic fraction of the soil was not affected by the type of pasture and did not change with time. The difference in cation exchange capacity for the cultivated soil was, therefore, due to the difference in the cation exchange capacity of organic matter residual from the clover and grass pastures.

‘Nitro-chalk” was applied to established swards of ryegrass S. 24 and cocksfoot S. 37 at the rate of 24 and 96 lb N/acre (27 and 107 kg N/ha) before growth commenced and after each cutting. The cuts were taken each time the grass reached a length of 10–11 in (8–9 in of cut herbage). The main effect was that the higher rate of fertilization allowed the grass to be harvested more frequently and this grass had lower pectin, cellulose and hemicellulose contents and a higher level of digestibility. A secondary effect was that the proportion of hemicellulose to cellulose was less in the more heavily fertilized grasses. The cocksfoot grasses at both levels of fertilizer were cut more frequently than the corresponding ryegrasses and were only slightly less digestible. There was some decline in the digestibility of the grasses from May to September which was associated with lengthening growth intervals and generally higher percentages of the structural constituents.

Yield and growth analysis has been carried out on vining peas (variety Dark Skinned Perfection) sown at 43, 97 and 172 seeds/m2 at a rectangularity of 1:1. No difference wasobtained in the yield of green peas (at tenderometer reading 110) over this fourfolddifferencein sowing density.

At a high seed rate (172/m2) a high peak leaf area (8·3) was attained 1 week afterthe start of flowering but declined rapidly. The peak number of flowers and pods reached 1002/m2 at this density, but there was a greater wastage (34 %) by abscission than inthe lower seed rates which resulted in a similar number of pods/unit area being present at the time of vining for all densities.

In contrast, peas sown at low density (43/m2) resulted in a lower peak leaf area (4·3) but this occurred during the stage of pod fill; net-assimilation rate was somewhat higher also. Thus the yield of green peas may depend less on the ability of the plant stand to provide reproductive nodes than on its ability to produce photosynthate during the post-flowering period.