High Feeding Level Research Articles

Variations saisonnières de la cyclicité chez la génisse créole. Influence de la croissance, de l'âge et de l'émotivité

The ovarian and estrous activities in creole heifers have been studied in Guadeloupe in a tropical environment. We carried out two experiments. In the first one, all the heifers from the research station's herd were blood-sampled twice every 2 months at a 10-day interval to determine their ovarian activity. The observations were ranked in order of ascending live weight, and the percentage of heifers showing ovarian activity was calculated for consecutive 10-kg increments in live weight from 115 to 275 kg. The percentage showing ovarian activity (Y) was subjected to probit transformation and related to live weight (X); probit Y = 12.4 log10 X - 23.7. The equation for observations ranked in order of ascending age and the percentage of heifers showing ovarian activity calculated for age increments over 2 consecutive months was: probit Y = 7.06 log10 X - 3.9. Furthermore, the percentage of cyclic heifers in the herd varied from 40 p. 100 in September 1979 to 0 p. 100 in July 1980 and then to 30 p. 100 in September 1980. The percentage of cyclic heifers at a given period of observation was highly correlated with the mean daily increase in body weight (r = 0.86). In the second experiment, 12 heifers with a high feed level were blood-sampled weekly and checked for estrous daily with an androgenized female with a chin ball mating harness. The mean duration of a "normal cycle" (interval between two estruses: more than 15 but less than 31 days) was 21 days. There was no variation of ovarian activity with the month of the year, but the incidence of silent ovulation was high (23.7 p. 100). The seasonal variation of this percentage is shown. Female emotivity was also an important factor: emotional heifers had a higher percentage of silent ovulations than unemotional heifers (27 vs 17 p. 100) and a smaller mean daily gain (180 vs 280 g).

Effect of body condition at calving and level of feeding in early lactation on milk production of dairy cows

Two experiments were carried out to measure effects of body condition at calving and different levels of feeding after calving on milk and subsequent reproduction.In experiment 1, which was conducted in two consecutive years, 162 cows (77 in year 1 and 85 in year 2) were group feed so as to reach a target body condition (condition scores ranging from 3-6) four weeks before calving. During the last four weeks before calving, all cows were managed so as to maintain their individual condition scores. At calving, cows in similar condition of similar breed and with similar previous milk production were allocated to high and low levels of feeding at pasture for the first five weeks of lactation. Mean pasture intakes were 13.0 and 7.0kg dry matter (DM)/cow.d in year 1 and 15.0 and 8.5 kg DM/cow.d in year 2In experiment 2, 40 cows were offered pasture and hay from 20 weeks before calving to achieve a body condition score of either 4 or 6 by two weeks before calving. During the first five weeks of lactation, cows were individually fed in stalls on freshly cut pasture at one of three levels of intake, 7 or 10 kg DM/cow.d or .In both experiments cows were grazed as one group from week 6 to 20 of lactation.Improved body condition at calving resulted in an extra 4.0, 11.0 and 7.4 kg milk fat per unit condition score over 20 weeks of lactation, for year 1 and 2 of experiment 1, and experiment 2, respectively. Cows in poorer condition partitioned a higher proportion of feed energy to liveweight at the expense of milk production than did the cows in better condition. However, increasing the plane of nutrition in early lactation resulted in higher levels of milk production and reduced the need for cows to mobilize bodyreserves. Improved body condition at calving had a positive effect on milk fat percentage, particularly in early lactation, but did not affect milk protein percentage. Input-output relations calculated from the experimental data showed that the benefit sf to improve body condition before calving was less than that of additional feeding after calvin changes in the condition of the cows were taken into consideration (25.8 vs 1 4.6 kg DM to yi kilogram of milkfat). Improvements in condition and feeding in early lactation reduced the anoestrus interval after calving by 5.7 d for each additional condition score at calving and 1. d for each additional kgDM/cow.d fed over weeks 1-5 of lactation. The input-output relations resented will enable farmers to assess the likely consequenes of changes in their feeding management in the crucial peripartum period with a greater degree of confidence than in the past.

Milk production from subtropical non-dairy sheep. 1. Ewe performance

SummaryMilk yield of 270 Rahmani, Ossimi and Barki subtropical Egyptian ewes rearing single lambs during three successive lambings in 2 years was estimated over 12 weeks of the lactation using a lamb-suckling technique. The ewes received either normal or high level of feeding during late pregnancy and lactation.Ossimi and Rahmani ewes showed significantly (P < 0·01) higher total milk production than the Barki. Milk yield declined sharply for the Barki ewes after the 6th week of lactation. Breed variation failed to attain statistical significance in the first 4 weeks of lactation. The highly fed ewes produced significantly (P < 0·01) more milk at different stages of lactation than the normally fed ones. High level of feeding, however, is not recommended for subtropical non-dairy ewes as it is not economic. Spring-lambing ewes produced significantly more milk during the first 8 weeks of lactation, while the summer-lambing ewes were more persistent in their milk yield in the last 4 weeks of lactation.Neither age of ewe nor body weight significantly affected milk yield. Correlation coefficients between milk yield and body weight at lambing are small and range from 0·00 to 0·24.

Responses of ‘Kentucky-31’ Tall Fescue to Varying Forcipata loca DeLong & Caldwell Infestation Levels: Growth Chamber Study (Homoptera: Cicadellidae, Typhlocybinae) 1

The effects of various infestation levels of Forcipata loca Delong & Caldwell on the yield, tillers/plant, yield/tiller, leaf elongation rate, carbon dioxide exchange rate, specific leaf weight, leaf diffusive resistance, and water soluble carbohydrate concentration of ‘Kentucky-31’, tall fescue, Festuca arundinacea Schreb., were studied. The growth response of tall fescue to 9 and 27 leafhoppers/9.5 cm diam. plastic pot was increased tillering with corresponding decreases in yield and yield/tiller after each of 2 infestation periods. Leaf elongation rates were less at the low infestation level of 3 leafhoppers/pot. Photosynthesis and specific leaf weight were only affected at the high feeding level (27 leafhoppers/pot) and only after a second infestation period. There was no significant reduction in leaf diffusive resistance at either infestation level. Water soluble carbohydrate concentration in the leaves decreased with increasing infestation levels.

Climatic indicators of pasture growth and their relationship to milk production patterns in eastern new South Wales

The climatic elements of rainfall and temperature influence the duration and rate of growth of rain-fed pastures in eastern N.S.W., a region where non-irrigated pastures form the greatest part of feed intake for dairy herds and where year-round grazing is practised. The agro-ecosystem on these dairy farms thus involves a strong climatic component, which may affect milk production patterns through the medium of pastures. A Growth Index, proposed by Fitzpatrick and Nix (1970), was modified and used to indicate those weeks (of a 2-year period) during which climatic factors imposed limitations on pasture growth; comparisons were then made between Growth Index values and milk production by using correlation and spectral analysis. Two locations with differing temperature and rainfall regimes were selected for study. At the first location, low winter temperatures and dry spells in summer both restricted pasture growth, and the association between weekly milk production and the “limiting climatic factor” Index value was significant. At the second location, the effects of dry spells on pasture growth and hence milk production were reduced by the use of irrigation and high levels of supplementary feeding. Seasonal patterns of milk production and some shorter-term fluctuations in output were explained in terms of periods of pasture growth, as indicated by the “limiting factor” Growth Index.

Interactions of zinc and selenium on the binding of cadmium to rat tissue proteins.

The administration of cadmium to rats by either oral or injection routes causes zinc to accumulate in the low molecular weight (MW) protein metallothionein (MT) of liver and kidney, but not in a low MW protein in the testis. Preliminary evidence indicates that the low MW cadmium-binding protein in testes is not MT. Feeding high levels of zinc to rats results in its accumulation with tissue MT, and the zinc is very labile. In contrast, the zinc that accumulates in MT as the result of cadmium exposure is not very labile. In the reverse situation, zinc does not cause cadmium to accumulate in MT. The turnover of MT is shorter when saturated with zinc than when cadmium is the predominant metal bound to it. Even though selenium will counteract testicular damage due to cadmium, it causes cadmium to accumulate in this organ at higher levels than in animals exposed to cadmium without selenium. Injection of selenate, and selenide--but not selenomethionine or selenocystine--diverts the binding of injected cadmium from low MW proteins to high MW ones in the testes. Selenium injections had only minor influences on the binding of zinc to testicular proteins. In contrast, very little diversion occurred in the binding of either cadmium or zinc in tissues of rats fed high levels of selenium. The data suggest that it is the selenide form of selenium that causes the diversion of cadmium binding in tissues, thus providing protection of testes against cadmium exposure.

The effect of body-weight changes during pregnancy and lactation on the performance of three breeds of sheep

SUMMARYThree husbandry systems were used to promote differential live-weight gains in 603 Cyprus Fat-tailed, Chios and Awassi ewes. Ewes on the high level of feeding had heavier litters than those on the medium and low levels. Litter size was not affected by level of feeding during pregnancy. Milk production was highest (P < 0·01) for ewes on the high level. The milk production of Chios and Awassi ewes was similar on the high and low feeding levels, but Awassi ewes outyielded both other breeds on the medium level. Chios ewes had larger and heavier litters (P < 0·01) than both other breeds. The correlations between live weights during lactation and milk yield were low and negative indicating a tendency for body loss at high yields.

Effect of Energy Intake during Pregnancy and Lactation on Body Composition in Rats

A paired feeding experiment involving high (H) and low (L) feeding levels during pregnancy and lactation was conducted using bred and open female rats to determine the effects on body composition. Pregnant rats contained a higher percentage of water in the fat-free body (FFB) than that of non-pregnant rats indicating tissue hydration. Composition of the FFB and fat-free dry matter (FFDM) was not altered by feeding level during pregnancy. During lactation, the feeding levels were either continued H-H and L-L or were changed to H-L or L-H within the lactating or open (non-lactating) pairs. Composition of the FFB and of the FFDM was altered by feeding level during lactation. A high energy intake result in a greater proportional loss of ash than of protein during lactation. In contrast, neither the composition of FFB nor FFDM was altered in the non-lactating rats on similar energy intake regimes. The lactating females had a higher percentage of water in FFB than the non-lactating rats. Although there was variation in water content of FFB and in the composition of FFDM, the correlation between percentage of body water and body fat after the adjustment of effects of pregnancy, lactation, energy and their interaction, was high (r = -0.98).

The relative efficiency of food utilization of British Friesian entire male and castrate male cattle at two levels of feeding

ABSTRACTA combined nutritional balance and comparative slaughter experiment using 20 animals compared entire male and castrate male cattle when pair-fed at high and medium levels of feeding and slaughtered at a constant 400 kg live weight. The carcasses were dissected into lean meat, separable fat, and bone, and the edible portion of the carcass was further analysed for crude protein, fat and water.There were no significant differences between entire and castrate animals in their ability to digest energy, nitrogen or modified acid detergent fibre. The mean metabolizable energy values (MJ/kg dry matter) of the diets were 10·6 for castrates and 10·9 for entire animals. Live-weight and carcass gains (kg/day) for each treatment were respectively: entire high feeding level, 1·10, 0·69; entire medium feeding level, 0·91, 0·57; castrate high feeding level, 0·92, 0·57; castrate medium feeding level, 0·79, 0·48. Castrate carcasses contained significantly (P < 005) less lean meat and more separable fat. The edible portion of these carcasses also contained significantly (P < 0·05) more total fat but less protein and water than entire carcasses. Daily carcass protein gain was significantly higher for entire animals (P < 0·001) but daily energy gain was not significantly different. The most efficient conversion of dietary metabolizable energy and crude protein to either live weight or carcass meat production was obtained by the use of entire animals and the high level of feeding.

Quantitative digestion of fresh herbage by sheep

SummaryThe utilization by sheep of dietary N provided in high protein, high water content fresh herbages (Ruanui perennial ryegrass, Tama Westerwolds ryegrass, Pitau white clover, and Fakir giant sainfoin at two stages of maturity) was studied at two levels of intake (maintenance and 1·5 maintenance). Feed was provided by constant feeder.Apparent digestibility of N was similar for all herbages (ca. 85%) except sainfoin which, particularly at a late stage of maturity, was lower (70–80%). A small loss of nitrogen across the stomachs occurred with clover (1–3 g/day) and Tama ryegrass at the higher feeding level (2 g/day), but no loss was observed with the other diets. The apparent digestibility of N and of non-ammonia N (NAN) in the intestines was lower for sainfoin, and estimated true digestibility was also lower. Amino acid N contributed less to the NAN reaching the duodenum on the sainfoin diets than on the grass and clover diets.N retention was negative at the lower level of feeding for ryegrass and clover diets. It was greatest for the sainfoin diets at similar N intakes, so that efficiency of retention of apparently digested N was also greatest for sainfoin.The size of the urea pool, the plasma urea concentration and the urea irreversible loss, using [14C]urea, did not differ significantly between diets at similar N intake. Urea irreversible loss exceeded urinary urea excretion by 35—50% on all but the late-maturity sainfoin diet, where urea irreversible loss was more than double the urinary urea output. These data indicate dietary differences in the extent of degradation of urea on recycling to the gastro-intestinal tract. Urea clearance across the kidney was also lowest for sainfoin.Data are compared in a simple model which illustrates the importance of variable clearance of urea across the kidney and the gut wall and the need for knowledge of factors which control this.

Gizzard Erosion and Ulceration in Broiler Chicks

Six kinds of fish meal were examined by broiler chick assay to determine whether they included toxic substance (s) for chicks to induce gizzard erasion (GE) or not. In this experiment, GE was found in chiks fed diets contaning a high concentration of some products of fish meal. The higher dietary level of fish meal, the severer the erosion of chicks. Fish meal which did not cause GE for itself and which had been heated at 130°C for 5hrs, caused GE. Toxic substance(s) which caused GE had not been extracted from fish meal with either methanol-ether or water. Methanol-ether or water extracts from fish meal which was capable of causing GE after heat treatment caused no GE before or after heat treatment. The residue of methanol-ether extraction caused GE after heat treatmennt. The residue of methanol-ether extraction caused GE after heat treatment, but that of waterextraction did not. Both mixture of the water extract with white fish meal and of mackerel fish soluble with white fish meal showed severe GE after heat treatment.In conclusion, GE in broiler chicks was caused by feeding high level of some products of fish meal. The toxic substance causing GE was water-insoluble. It might have been produced from a water-soluble fraction of the fish meal by heating in the presence of fish meal which was non-toxic.

Fertility in Cheviot ewes. 3. The effect of level of nutrition before and after mating on ovulation rate and early embryo mortality in South Country Cheviot ewes in moderate condition at mating

ABSTRACTOne hundred and twenty South Country Cheviot hill ewes were differentially group-fed indoors over a 2-month period to achieve either moderately-good or poor body condition. Over 5 weeks prior to mating, ewes in moderately-good condition were brought down in condition by restricted feeding and ewes in poor body condition were raised in condition by a high level of feeding. The ewes were thus in moderate condition at mating. During the first 4 weeks after mating, half the ewes from each original condition group were fed at a high level and the other half were fed at a low level. Ewes were killed either on return to service or at 30 ± 10 days forcounts of corpora lutea and viable embryos.Ovulation rate was not significantly related to the level of pre-mating food intake at the condition level studied, although the trend was positive. Embryo mortality, as ova loss, was reduced by a high level of post-mating food intake but was increased by a high level of pre-mating intake. This latter result, however, may be influenced by the experimental confounding of high pre-mating food intake and very low initial body condition. The greatest loss was incurred by ewes, originally in poor condition, which were fed at a high pre-mating level and a low post-mating level. Potential lambing rate at slaughter was not affected by the level of food intake either before or after mating although the trend was for a low level of post-mating intake to be associated with an increase in the proportion of barren ewes.

Fertility in Cheviot ewes. 2. The effect of level of pre-mating nutrition on ovulation rate and early embryo mortality in North and South Country Cheviot ewes in moderately-good condition at mating

ABSTRACTIn two experiments over 2 years, 57 North Country Cheviot and 82 South Country Cheviot hill ewes were differentially group-fed indoors over a 2-month period to achieve either good or moderate body con- dition. Over 5 weeks prior to mating, ewes in good condition were brought down in condition by restricted feeding and ewes in mod- erate condition were raised in condition by a high level of feeding. The ewes were thus in moderately-good condition at mating. After mating, ewes were maintained in this condition until killed either on return to service or at 29 ± 8 days for counts of corpora lutea and viable embryos.Ovulation rate in each breed was positively related to the level of pre-mating food intake at the condition level studied. Embryo mortality, as ova loss, was not influenced overall by the level of pre-mating food intake but loss of multiple-shed ova was greater than that of single-shed ova in ewes which had been on restricted feeding before mating. Although a greater proportion of ewes in the North Country Cheviot breed were not pregnant at slaughter, this could not be identified as a breed difference since the breeds were studied in different years.

Milk production from diets of silage and dried forage. 3. Effect of formalin-treated ryegrass silage of high digestibility givenad libitumwith and without urea

ABSTRACT1. Young adult and adult lactating British Friesian female cattle (heifers and cows) were individually fedad libitumon perennial ryegrass silage (F) made with an additive of formic acid (3·41 of 85% acid/t fresh grass) or on a silage (FF) made from the same crop with an additive of 9·01/t of a mixture of equal volumes of formic acid and formalin (35% w/w solution of formaldehyde). Silage F was supplemented with a concentrate containing 50% dried grass and 50% barley at a low (L) or high (H) level of feeding; silage FF was supplemented with the same concentrate at the lower level only, either with urea at 2·0% of the silage DM (FFLU) or without urea (FFL).2. Silage F had a lower pH (P< 0·001) and contained more lactic, acetic and total fermentation acids (P><0·001). The DOMDin vivoof the diet was lower (by up to 3 units) for treatment FFL than for the other treatments (P<0·05 in weeks 17 and 18).3. Over weeks 4 to 18 of lactation the mean dry-matter intakes (DMI) of silage on treatments FL and FFL were similar, but silage DMI was 12 to 13% greater on treatment FFLU than on FL or FFL (P<0·05). Digestible OM intake was greater with FFLU than with FFL (P<0·01) and with FL (P<0·05).4. Milk yields did not differ significantly between treatments and metabolic blood profiles were normal.

Growth rings in dinosaur teeth

ANNUAL growth rings are often found in the skeletal tissues of Recent and fossil ectothermic vertebrates1,2. These rings are usually attributed to the inability of ectotherms to maintain high levels of activity, feeding and growth during adverse times, such as dry seasons in tropical areas and cold seasons at higher, more temperate latitudes1. In endothermic vertebrates, however, the efficient production of endogenous heat results in a relatively constant body temperature, and high activity and feeding levels are more easily sustained. Consequently, the growth of skeletal tissues in these animals is less sensitive to seasonal variations than in ectotherms, and annulations are rare except in species living under severe seasonal regimes3,4. Many workers have proposed that dinosaurs were endothermic, as are all living mammals and birds, rather than ectothermic, as are all living reptiles3,5–10. In accordance with this hypothesis, pronounced seasonal growth rings have not been observed in the calcified tissues of dinosaurs5,6. However, here I report the discovery of such rings in the teeth of diverse Late Cretaceous dinosaurs.

Studies of weaned lambs before, during and after a period of weight loss. I. Energy and nitrogen utilization

Lambs were given a balanced diet immediately after weaning at 6 weeks and grown from 15 to 25 kg on a high level of feeding. They were then underfed for 21 weeks, which caused weight to return to 17 kg, and finally allowed to regain weight on ad libitum feeding. Brief periods of 'maintenance' feeding were interposed in each phase. Nitrogen and energy balances were obtained for successive weeks by measuring food intake and all losses. There was general agreement between these results summed for each phase of the experiment and data obtained from a parallel slaughter trial. Metabolizable energy was a constant 56% of gross energy or 11.3 MJ/kg dry matter. Estimated energy requirement for maintenance was depressed by 28% after a few weeks of undernutrition, but efficiency of utilizing additional energy was also lowered, cancelling the potential benefit for compensation. There was no difference in efficiency between normal and compensatory growth. Protein contributed 25–40% (varying inversely with body weight) of energy balance during both normal growth and regain but only 10% during prolonged weight loss. There was some evidence of improved nitrogen economy in the first month of compensation.

Studies on the Ameliorating Effect of Ascorbic Acid on Mineral Toxicities in the Chick

The effect of dietary ascorbic acid on the toxicity of high levels of cobalt, selenium, vanadium, cadmium, copper, and mercury was determined in chicks. The vitamin reduced the growth retardation caused by cobalt, selenium, vanadium, and cadmium administration but had no such effect on copper and mercury toxicity at the levels used. The effect of ascorbic acid on growth could not be mimicked by ferrous iron administration. Ascorbic acid did not alleviate the increased susceptibility of chicks to Salmonella gallinarum caused by feeding high levels of these elements.

The nutritive value of silages. Energy metabolism in sheep receiving diets of grass silage or grass silage and barley.

1. Two calorimetric experiments were conducted to study the utilization of energy in sheep given diets of grass silage or grass silage and barley. Three silages were investigated. One was made from first-harvest grass in the spring (S) and the others from regrowth cut either early or late in the autumn (E and L respectively). All were of perennial ryegress (Lolium perenne) and preserved with formic acid. Each silage was given at two levels of feeding, the lower providing approximately a maintenance energy intake. The S and L silages were also given supplemented with barley. 2. The digestibilities of organic matter, cellulose and energy in the silages were high. Measured at maintenance, digestible energy (DE) contents (MJ/kg dry matter (DM))were 11.83, 14.67 and 12.90 for S, E and L respectively. The DE contents of the S and E silages were depressed at the higher level of feeding but the effect was offset by changes in the energy losses as methane and urine. Metabolizable energy (ME) contents (MJ/kg DM) for the three silages, S, E and L were respectively 9.88, 12.54 and 10.73 at the low level of feeding and 9.91, 11.99 and 11.08 at the high level of feeding. The mean ME content of barley calculated by difference was 13.76 MJ/kg DM. 3. The mean efficiencies of utilization of ME for maintenance (km) for the S, E and L silages were 0.69, 0.71 and 0.68 respectively. Corresponding values for fattening (kf) were 0.21, 0.57 and 0.59. Excepting the kf for the S silage which was low, observed efficiencies were in broad agreement with those predicted by the equations of the Agricultural Research Council (1965). Similar agreement was obtained with all diets consisting of silage and barley.

Effects of variations in energy and protein intake on digestibility, nitrogen balance and carcass composition in British Friesian castrate male cattle

AbstractTwenty-seven castrate male cattle were used in two nutritional balance and slaughter experiments to measure the effects of increasing levels of dietary protein (9 to 15% in the dry matter) at two levels of feeding (approximately 16 and 22 MJ metabolizable energy (ME)/100 kg live weight (LW) per day) on digestibility, nitrogen (N) balance and carcass growth and composition over the LW range 130 to 390 kg.The higher level of feeding increased LW gain and carcass gain (CG) but higher protein intake increased LW gain and CG only at the higher feeding level as a result of its favourable effect on digestibility. N balance tended to overestimate carcass N retention at higher levels of protein intake.The higher level of feeding increased the separable fat and total fat in the carcass. Increased protein intake had no effect on the lean meat content but increased the percentage protein in the edible portion of the carcass. LW gain, CG and carcass energy deposition were related to ME intake only but N balance and carcass protein gain were related to both ME and digestible crude protein intake.

15N INCORPORATION AND GLUTAMINE SYNTHETASE INHIBITION STUDIES OF NITROGEN ASSIMILATION IN LEAVES OF THE NITROPHILE, DATURA STRAMONIUM L.

SUMMARYThe N assimilation pathways in leaves of Datura stramonium L. have been investigated at low and high levels of xylem stream nitrate feeding by an 15N infiltration technique in the presence and absence of the glutamine synthetase inhibitor, methionine sulphoximine (MSO).In the absence of MSO, glutamate showed the highest 15N enrichment of any free amino compound at both feeding levels. At the high N feeding level, glutamine showed the highest accumulation of 15N at all stages of the time course, with secondary accumulation in glutamate. At the low N feeding level the reverse was true. These findings indicate the operation of both the glutamine synthetase‐GOGAT and glutamate dehydrogenase pathways in Datura leaves.In the presence of MSO intracellular pools of all the amino compounds, with the exception of glutamine and threonine, became rapidly drained. There was an almost complete restriction of the supply of newly reduced 15N to amino acid assimilation and it accumulated as ammonia. The large glutamine pool remaining contained no 15N enrichment, and was probably an extrachloroplastic storage pool not immediately available for amino acid synthesis. These experimental results indicate the almost exclusive role of the glutamine synthetase‐GOGAT pathway in the assimilation of newly reduced nitrate into amino acid metabolism in Datura leaves.