Modification of soil nutrients and micro‐climate by tree crowns in a semi‐arid rangeland of south‐western Zimbabwe

Abstract

Tree crowns in semi‐arid areas have often been found to create micro‐habitats of improved soil physical and nutrient status and reduced evapotranspiration. These encourage the growth of mesic, palatable and high yielding perennial grasses in otherwise arid environments. A two‐year study, in areas with a long history of light grazing, at Matopos Research Station sought to establish whether the soil nutrient status and micro‐climate under tree crowns are different from those in open areas, and whether the differences are affected by soil type and tree species. The study trees were Terminalia sericea and Acacia karroo. There were consistent patterns in soil nutrient status between understorey and open areas, although these patterns were largely not significant. There was also a consistent pattern in soil volumetric water content of open areas > T. sericea > A. karroo understorey areas. Tree crowns reduced solar radiation reaching understorey areas by an average of 88% and rainfall by an average of 15%. The findings on soil nutrient status are consistent with results from disturbed systems, and challenge the dogma, at least for soil nutrient status, that conservative stocking rates are beneficial.     

Comparative analysis of pre‐laying behaviour in battery cages and in three alternative systems

1. Pre‐laying behaviour was compared in battery cages (C) and in three alternative husbandry systems: perchery (P), deep‐litter (DL) and covered strawyard (S).

2. Twenty ISA Brown hens were observed in each system for 60 min before oviposition and 5 min afterwards.

3. There were significant between‐system differences in a number of behavioural elements associated with the nest. Most varied along the sequence: C, P, DL, S, but the differences between the three alternative systems were generally less than between them and C.

4. The main factor governing the expression of pre‐laying behaviour appeared to be the availability, the number and the arrangement of littered nests.

5. Behaviour elements preceding nest entry and which were associated with area per bird again varied along the sequence C, P, DL and S with the major discontinuity between P and DL.

6. In P and C the searching phase was extended, in C at the expense of sitting. In P much time was spent inspecting the nests and many nest entries were made.

7. The Gakel call appeared to be related to finding a suitable nest site. In P the number of calls and the mean duration per nest inspection declined in a parallel fashion towards oviposition. In C, where no suitable nest could be found, Gakel calling remained high during the whole observation period.

8. These behavioural differences suggested that pre‐laying behaviour was poorly expressed in C and most fully in S, but that expression was in general relatively complete in all three alternative systems.

9. The ability of hens to express pre‐laying behaviour fully and coherently may be relevant to their welfare.     

Time course of oxidative phosphorylation in liver mitochondria of chickens fed on high‐protein diet

1. Progressive alterations in oxidative phosphorylation of liver mitochondria were followed for 14 d in growing chickens fed on either semi‐purified low (7%) or high (61%) protein‐energy diet. Hepatic mitochondrial oxidative phosphorylation rates were assessed polarographically with pyruvate + malate as substrates.

2. The ADP:O values were reduced significantly 4 d after the feeding of a high‐protein‐energy diet, when compared with those in chickens fed on a low‐protein‐energy diet, whereas the state 3 oxidation rates in chickens fed on a high‐protein‐energy diet from day 6 to 14 were significantly lower than those in low‐protein‐fed chickens.

3. No changes in sensitivity of mitochondrial ATPase activity to oligomycin, expressed as % of total ATPase activity, were observed among chickens fed for 21 d on diets with various protein concentrations though the FoF₁‐ATPase activity, expressed per mg protein, tended to decrease in chickens fed on high‐protein‐energy diet.

4. These results suggest that the reduced ADP:O values for liver mitochondria in the high‐protein‐fed chickens may not be involved in the degrees of integrity of the FoF₁‐ATPase.     

Factors affecting the diet selection of choice‐fed broilers

1. In one experiment two strains of choice‐fed broilers were given wheat, either whole or ground, and a balancer diet, either pelleted or as a mash, for 4 weeks. They were compared with broilers given a complete single feed.

2. In a second experiment, the effect of a pelleted or mash balancer, relative feeding trough space for whole wheat and balancer (1:1 or 2:1 with total feeding space constant) and group size (20, 40 or 80 broilers maintained at a constant stocking density) on the diet selection of choice‐fed broilers was examined.

3. Food form had a large effect on diet selection although there was no effect on total food intakes or weight gains. If a mash balancer was provided, the broilers selected a greater proportion of wheat when it was ground rather than whole, but if the balancer was pelleted a greater proportion of wheat tended to be selected when whole wheat was provided.

4. No significant differences in diet selection were observed as a result of differences in the strain of broiler, the relative amounts of feeder space for wheat and balancer or group size.     

Torsion of the abomasum in ruminants: Diagrammatic representation of rotary movements based on post‐mortem findings

Summary

A theoretical analysis of the types of displacement of the abomasum in the abdomen is presented based on a stud of forty‐seven post‐mortem examinations of calves, cows, lambs and sheep showing right‐sided abomasal displacement and production of knots. These displacements are quantified following the introduction of a dual‐axial system. One system (XYZ) related to displacements of the abomasum on a pendulum model, the point of suspension being situated on the visceral surface of the liver and the arms consisting of parts of the digestive tract adjacent to the abomasum. The other system (x ₁ y ₁z₁ ) comprises axes centered on the abomasum, about which this organ was able to rotate without changing its position in the abdomen.

In order to make quantification of the displacements and deformations possible, the term twine is introduced. Twining results from interlacing of sections of the digestive tract, which are not normally adjacent. This limits the concept of torsion to helices appearing in the pyloro‐duodenal region and the omaso‐abomasal junction. To identify the various forms of abomasal displacement, a new terminology is introduced and basic elements suggested to make quantifications possible.     

Age difference in pharmacokinetics of an amoxycillin trihydrate‐15% formulation administered intramuscularly to ruminants

Summary

Intramuscular administration of an amoxycillin trihydrate‐15% formulation to three groups of animals revealed in preruminant calves (age 3–4 weeks) significant higher plasma peak drug concentrations and shorter biological half‐lives than in 5‐month‐old ruminant calves and dairy cows. Differences in pharmacokinetics were related to age‐difference in drug absorption capability at the injection site regarding the formulation.     

Is metoclopramide an alternative to tramadol in management of post-operative pain? An experimental study

In this study, metoclopramide was compared with other pharmacological agents for preventing post-operative pain. Sixty Sprague-Dawley male rats, weighing 310-345 g were included in the study; 1 cm surgical incision, including skin, facia, and muscle was made to the plantar surface of rear foot of all anaesthetized rats. Rats were randomized into four groups. In group 1 (group S) 2 cm3 saline, in group 2 (group M) 2 cm3 metoclopramide (5 mg/kg) in group 3 (group T) 2 cm3 tramadol (45 mg/kg), in group 4 (group M+T) half doses of group M and group T was given intraperitoneally. Post-operative pain was assessed after 2 h, first and second days of incision. Post-operative pain scores were found to be significantly lower in group M, group T and group M+T when compared with the control group. But there was no significant difference between these groups. We concluded that metoclopramide, with low cost, fewer side-effects and being significantly effective for preventing post-operative pain, can be an alternative to tramadol.     

Effects of tryptophan supplementation to a maize‐based diet on lipid metabolism in laying hens

1. Experiments were conducted with laying hens to determine the effects of supplementing 0, 1.0, 2.0 and 3.0 or 4.0 g trp/kg diet to a maize and soyabean meal‐based laying ration (basal tryptophan = 1.66 g/kg) on tissue lipid concentrations.

2. Plasma cholesterol, triglycerides and nonesterified fatty acids were increased by supplementing the diet with 1.0 g trp/kg diet and decreased with 3.0 or 4.0 g trp/kg diet. A significant quadratic effect of supplemental tryptophan was observed on plasma lipids in most cases. The observed effects diminished with time. No consistent changes were observed in plasma glucose concentrations.

3. Total liver lipids were reduced by supplemental tryptophan at all concentrations.     

Evaluation of a layer diet formulated from non‐conventional feedingstuffs

1. A layer diet, the formulation of which was based on several non‐conventional feedingstuffs, was evaluated at the research station and under small farm conditions in Sri Lanka. The new feedingstuffs included finger millet, rice polishings, rubber seed meal, cassava leaf meal, ipil ipil leaf meal and dried poultry manure. A commercial mash, that is normally used on the farm, served as the control.

2. The performance and egg quality characteristics were similar between the test and control diets, the only exception being the egg yolk colour which was improved (P< 0.05) by feeding the test diet. Food cost per dozen eggs was lowered by feeding the test diet.

3. It is possible to formulate layer diets using non‐conventional feedingstuffs, achieve acceptable production and lower the food costs under small farm conditions in tropical developing countries.     

The nitrogen‐sparing effect of methionine in chicks receiving a protein‐free diet supplemented with arginine: Effect of various methionine substituents

1. The nitrogen‐sparing effect of methionine in chicks fed on a protein‐free diet containing arginine was examined in three 10‐d trials. Chicks received either a protein‐free diet, this diet supplemented with arginine and methionine or diets containing arginine in which the methionine was replaced by various methionine‐related compounds.

2. Body‐weight changes, nitrogen retentions and uric acid‐nitrogen excretion indicated that the methyl moiety was unlikely to contribute to nitrogen sparing activity and that cysteine, or possibly glutathione, played an important role. The possible mechanism of the nitrogen‐sparing effect is discussed.     

The effect of delaying the onset of laying in pullets with a low‐calcium diet on subsequent egg production

1. A low‐calcium diet (0.5 g calcium/kg) was used to prevent the onset of laying in young pullets.

2. It was fed at 16 weeks of age to five separate groups (groups 2 to 6) each of 50 to 60 birds.

3. Group 2 was fed on a normal layers’ diet at 23 weeks of age, group 3 at 27 weeks, group 4 at 31 weeks, group 5 at 35 weeks and group 6 at 55 weeks while the control group (group 1) of similar size to groups 2 to 6 was subjected to a normal commercial treatment for laying stock.

4. In all the experimental groups the onset of sexual maturity occurred normally, but only one or two eggs were laid before laying ceased under the influence of the treatment.

5. Laying re‐started when the hens were fed on a normal diet and production rapidly rose to a high level.

6. Groups 1, 2 and 3 differed little in the total number of eggs produced up to 72 weeks of age.

7. In all experimental groups there were fewer very small, small and medium eggs than in the control group.

8. It is suggested that the use of a low‐calcium diet before the onset of lay may have advantages which could be exploited on a commercial scale.     

Variation among individual white‐leghorn hens in the concentration of minerals in the albumen and yolk content of their eggs

1. The mineral composition of the albumen and yolk was determined in several eggs from each of a number of individual hens from the same White‐Leghorn strain. X‐ray fluorescent spectrometry was used to undertake two independent series of analyses. A total of 8 minerals (calcium, chlorine, iron, magnesium, phosphorus, potassium, sodium, sulphur) were included in the analyses of the yolk and the same minerals, but excluding iron (which is present in only small amounts), in the albumen.

2. There was considerable variation between individuals in the mineral concentration in their eggs (coefficients of variation ranged between 3.8% for sodium to 19.9% for calcium in the albumen, and between 4.3% for phosphorus to 11.8% for iron in the yolk).

3. At the same time, the moderately high repeatability of mineral concentration (t = 0.4?0.6) in successive eggs from the the same hen for several of the minerals analysed is indicative of some positive control by the hen of the mineral composition of her eggs.

4. There was a highly significant correlation (P≤ 0.001) between the mean concentration of potassium in the albumen and the hatchability of the eggs, supporting the claim that a deficiency of potassium in the egg could be the basis of some failures in hatchability.

5. The study also revealed variation among individual birds in the concentration of iron in the yolk which was negatively correlated (P≤0.01) with hatchability. No clear basis could be suggested for this variation among individual birds.     

Dietary chloride requirement of broiler chicks fed on a wheat‐soyabean diet

1. A diet based on soyabean meal and wheat contained insufficient chloride to support normal growth in chicks.

2. Ammonium chloride and sodium chloride were equally good sources of supplementary chloride for the chick.

3. When seven diets providing increasing proportions of chloride from 608 to 1808 mg/kg, were fed to chicks, maximal growth at 21 d was obtained at about 1200 mg chloride/kg diet.     

Influence of diet on the intestinal microflora and meat flavour of intensively‐reared broiler chickens

1. An attempt has been made to modify the composition of the gut flora of broiler chickens by dietary means in order to determine any concurrent changes in meat flavour.

2. Birds given a diet containing an increasing proportion of whole wheat supplemented with fresh green vegetable matter (special diet) were compared with conventionally‐fed controls. At 12 weeks of age those receiving the special diet had 10 to 100‐fold higher counts of Escherichia colt and faecal streptococci in the duodenum and lower small intestine and showed differences in the intestinal incidence of species and biotypes of lactobacilli.

3. Evaluation of cooked breast‐meat samples by a trained sensory panel showed a significant difference in flavour (P < 0.01) between conventional and special‐diet birds which varied from perceptually very slight to slight. The main terms used in distinguishing special‐diet birds from conventional controls included ‘richer’, ‘meatier’ and ‘sweeter’.

4. Storage of plucked, uneviscerated birds at 4 °C for 8 d maintained the flavour difference between the dietary groups but the effect of storage on flavour was greater in both groups of birds than the influence of diet alone. The likely influence on flavour of autolytic changes occurring in the muscle during storage of the birds is discussed.     

Performance of lines selected for fast‐and slow‐hatching times and crosses among them 1

1. Males of a control line and two lines selected for fast‐ and slow‐hatching were mated to females of the same three pure lines and three crosses between them. Hatchability, egg weight and hatching time were measured.

2. No significant differences were found between genetic groups in hatchability.

3. Groups containing the fast‐hatching line genotypes were significantly smaller in egg weight than those not containing this line.

4. Significant differences in hatching time existed between male lines and between female lines within pure and cross‐line parent types while no differences were observed between the female parent types and no interactions of male by female lines occurred.

5. It was concluded that inbreeding in the pure lines (10%) did not affect any of the variables measured.

6. The results on hatching time support the conclusion that little genetic variance other than additive variance is involved for this trait.     

The effectiveness of in‐plant chlorination in poultry processing

1. Sampling carcasses after plucking or after the post‐evisceration spray‐wash showed that 10 or 20 ppm available chlorine in the processing‐plant water supply caused little reduction in carcass contamination.

2. When 20 ppm chlorine was used in the water supply to parts of the processing‐plant other than the mechanical immersion chilling system, counts of faecal and spoilage bacteria from carcasses were reduced approximately 10‐fold after passage through the chilling system; bacterial numbers were correspondingly decreased in the chiller water due to a carry‐over of chlorine from the final spray‐washer.

3. Artificial contamination of carcasses with a readily identifiable strain of Escherichia coli confirmed the occurrence of cross‐contamination during plucking and evisceration; in‐plant chlorination reduced neither the proportion of carcasses contaminated nor the numbers of organisms transferred at these stages.

4. In most cases the chlorine‐resistance of poultry spoilage pseudo‐monads was greater than that of E. coli; hence in‐plant chlorination is to be recommended for processing‐plant water supplies which carry such spoilage organisms.     

The Potch System: An approach to the management of semi‐arid grasslands in southern Africa

A host of grassland management systems have been published and recommended. Whereas earlier approaches to grassland management emphasized the systematic resting aspect, the systems published since 1966 have tended to stress the degree of utilization of the grassland sward. In an attempt to accommodate the periodic dry periods that are so typical of the semi‐arid grasslands of western Transvaal, the Potch system of management was evolved. It aims at the development of a fodder reserve, firstly by delaying the commencement of summer grazing, and secondly, by allowing prolonged periods of absence in the grazing rotation. High utilization grazing within the concept of controlled selective grazing is prescribed. This approach was tested and demonstrated over a period of five years in an experiment comprising 240 beef breeding cows. It appeared that generally, summer grazing only commenced after the third week of November, and that the mean period of occupation amounted to 20 days, with a period of absence of 87 days. A conception rate of 85% of all the cows and heifers mated, was achieved. A stocking rate of 0.53 LSU ha^?1 could be maintained in an area where the general grazing capacity is 0.33 LSU ha^?1.     

The incidence of breast‐blister down‐grading in broiler chickens

1. A survey was conducted into down‐grading due to breast blisters at a large processing plant.

2. The relationships between incidence of down‐grading and age, body weight, sex, size of rearing site and its distance from the processing plant, and various weather conditions during the rearing period of each flock were examined using regression analysis.

3. Age and body weight and rearing site size were the only factors significantly correlated with amount of blistering.     

Effects on chick performance and nutrient digestibility of an endo‐xylanase added to a wheat‐ and rye‐based diet in relation to fat source

1. A study with growing chicks investigated the effects of an inclusion of an endo‐xylanase preparation (LYXASAN®) to a wheat‐ and rye‐based diet on performance and nutrient digestibility in relation to the fat source.

2. The basal diet contained 500 g wheat and 100 g rye/kg of diet. The basal diet was supplemented with either 65 g soya oil/kg or 60 g blended animal fat and 5 g soya oil/kg.

3. Endo‐xylanase added to the soya oil diet did not affect weight gain, but there was a numerical improvement in food conversion efficiency which was not statistically significant. When the endo‐xylanase preparation was added to the blended animal fat diet, both weight gain and food utilisation were improved by 9.5% and 6.0%, respectively (P< 0.05).

4. Digestibilities of organic matter, crude fat, crude fibre and NFE were not significantly affected by adding endo‐xylanase to the soya oil diet. However, when endo‐xylanase was included in the blended animal fat diet, digestibility of organic matter, crude fat, crude fibre and NFE were improved (P<0–05). The improvement in fat digestibility was the most pronounced, amounting to 9–4%. Nitrogen retention and metabolisable energy content were improved significantly by the addition of an endo‐xylanase to the animal fat diet (P< 0.05), by 6.6% and 6.5% respectively.

5. From the results of this study, it can be concluded that the effects on chick performance and nutrient digestibility of a dietary endo‐xylanase in a wheat‐ and rye‐based diet are influenced to a considerable degree by the type of fat in the diet.