Effect of diseases on the nutrient intake by suckling calves

An energy and protein intake test was applied to 341 female nursed calves under production conditions. Their daily intakes of skim milk enriched with milk substitute, fodder concentrates, and hay were recorded and their daily energy and protein intakes calculated. Their feed consumption was characterised by cumulative nutrient intake curves, depending on the time of foremilk feeding (K-I-period). Energy and protein intake figures were related to the findings obtained from daily health control, with the view to defining the effects of pneumonia or diarrhoea on feed intake. Both diseases were found to cause significant reduction in nutrient intake, depending on the given type of disease and severity, with their negative impact having been most markedly shown in the context of dry feed intake. The delay caused to the development of dry feed consumption by diseases of the respiratory and digestive tracts was many times longer than the time of the clinical course. The above observations provided some cues for conclusions regarding the approach to be taken by the veterinarian to diagnosis, therapy, and rehabilitation of affected calves. Certain concepts were derived from the findings as to how to feed calves to forestall developmental disorders.     

Effect of solid feed on energy and protein utilization in milk-fed veal calves

Little knowledge on the digestive and metabolic utilization of solid feed in veal calves is available. The objectives of the study were to determine the effects of 2 solid feeds offered at 2 feeding levels (FL90 and FL105) in addition to a milk replacer on heat production (HP) and protein and fat deposition in veal calves. Sixteen calves (148.0 +/- 3.7 kg) received milk replacer (75% of a reference DE allowance) and solid feeds that consisted of corn grain and pelleted hydrolyzed wheat gluten without (CO) or with (CS) chopped wheat straw. The solid feed supply provided 15 or 30% of the reference DE allowance to achieve FL90 or FL105, resulting in 4 treatments: CO90, CS90, CO105, and CS105. A fifth treatment consisted of using the milk replacer alone at FL90 (treatment M90) and was measured in 4 other calves. All calves were kept individually for 7 d in a respiration chamber to estimate energy and N balances and fasting HP. The digestibility coefficients of DM, OM, GE, and major nutrients were at least 94% for M90 and decreased when solid feed was added (P < 0.05). Methane production was negligible in M90 calves and increased when solid feed was given (ranging 8 to 23 L/d between CO90 and CS105, P < 0.01), indicative of ruminal fermentation. The provision of increasing amounts of solid feed decreased urinary energy in connection with a tendency (P = 0.09) for a reduction of urinary glucose excretion. The metabolizability of DE was greater with the milk replacer (95.6%) and decreased when straw was added (P < 0.01). Neither CO90 or CS90 affected HP and total energy retention (P > 0.05). Dietary treatment had no effect (P > 0.05) on activity HP (53 kJ/kg of BW(0.85) daily) but did affect thermic effect of feeding; efficiency of utilizing ME for maintenance and growth was greatest for the M90 calves (84.5%, P = 0.02). Fasting HP tended (P = 0.09) to increase at the greatest FL (308 vs. 298 kJ/kg of BW(0.85) daily). Maintenance ME requirement increased (P = 0.04) from 364 to 382 kJ/kg of BW(0.85) daily when feeding level increased (P = 0.04) but was not affected by ingestion of solid feed. The provision of solid feed to veal calves was associated with a reduced efficiency of N retention (P = 0.04), and energy retained as protein tended to decrease (P = 0.08), probably as a result of an imbalanced AA supply of the solid feeds. The data were used to calculate the energy contents of solid feed. The utilization of energy from solid feed differed from that of milk replacer.     

A simulation model of forage yield, quality and intake and growth of growing cattle grazing cornstalks

A simulation model was developed to predict corn crop residue yield and quality and intake and performance of growing cattle grazing cornstalks. The model is wholly deterministic and integrates the effects of weather, residue supply and animal components. Low temperatures increase animal energy requirements, whereas snow cover decreases residue available. Residual grain and leaf are calculated from grain yield. Residue quantity and quality are reduced daily by environmental losses and animal consumption. Daily performance is predicted based on the nutrients obtained from residue and supplemental feed. Under unlimited roughage supply, leaf, husk and grain are primary diet components. Grain consumption decreases as the supply diminishes and forage quality decreases with time. Intake is calculated based on digestibility and fecal output = .0365 W.75. Forage availability affects intake in a curvilinear fashion. Energy gain is predicted by NRC equations and protein gain from metabolizable protein supply. The model underestimated intake of calves measured with chromic oxide and in vitro DM disappearance. Simulated daily gain (y, kg) of calves grazing at several stocking rates was related to observed daily gain (x, kg) by the equation y = .012 + .853 x (R2 = .71, Sy.x = .077). The model overestimated response to protein supplementation. Severe cold weather was predicted to reduce gains or cause weight loss due to increased energy requirements for maintenance. The model can be used as an aid in both research planning and cattle management.     

The effect of biotechnological treatment of milk-replacer feeding mixtures on hematologic and biochemical parameters and its utilization in calves

A trial was performed with cellulase administration (3 cx per g of ingested feed dry matter) to early weaned calves fed minimum amounts of milk replacer (21 kg per milk nutrition period) and sweet (C, D) and sour (A, B) diets. The groups B and D were supplemented with an enzyme till the age of 90 days. The calves were given free choice of COT concentrate mixture, hay and water. Liveweight gains, feed and nutrient intake and health condition of calves were the characteristics investigated in this trial. Hematocrit value, hemoglobin, glucose and urea contents were determined in blood, in blood plasma buffer capacity was investigated. Although the differences in calf performance are not statistically significant, the best growth of calves in the vegetable nutrition period was observed in calves in group D. Nutrient conversion was also higher in calves of group D in the vegetable nutrition period. In conversion of nutrient consumption per 1 kg liveweight gain the difference in the intake of digestible crude protein and starch units between the group of calves fed sweet milk without enzyme addition in the milk nutrient period (A--digestible crude protein 0.40 +/- 0.005; starch units 1.74 +/- 0.008) and group D (sour diet + 3 cx cellulase--digestible crude protein 0.34 +/- 0.007; starch units 1.52 +/- 0.044) was statistically significant (P less than 0.025 and P less than 0.05) in favour of group D. An analysis of the results of hematological and biochemical investigations during the trial demonstrates that the sour diet is better in view of changes in glucose concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic factors controlling feed efficiency in dairy cows

The direct control of feed efficiency is feasible only in test stations and experimental farms. Here coefficients of heritability were found below those for milk yield. Between milk yield and feed efficiency there exist strong genetic correlations, while the correlations between feed intake and feed efficiency are smaller. In spite of these favourable correlations, breeding for higher milk yield entails a serious energy deficit during the first part of lactation. The feed intake reaches its maximum not earlier than 10 to 12 weeks post partum, but peak daily milk yield has already been reached by two to four weeks post partum. Due to energy deficiency the feed efficiency during the first part of lactation seems to be very high, but in fact the feed intake at this time does not cover the energy demand of the high yielding dairy cow.In future more research on genetic factors controlling the feed intake during the first 10 weeks of lactation is required. As potential single factors the capacity of the digestive tract, the production of saliva, the ruminal fermentation, the rate of passage and the overall physiological status of the animal should be investigated. To estimate the real feed efficiency one should observe not only the direct production in milk, milk fat, protein and lactose but also the metabolism of depot fat, growth, nutrition of the foetus, maintenance requirements and a genetically affected resistance against metabolic disorders. Higher feed intake at beginning of lactation can reduce the feed costs, increase the protein content in milk and improve the conception rate in dairy cows. For breeding purposes we need indirect parameters for feed intake under field conditions, e.g. changes in body measurements, urea content in milk, oleic acid proportion in milk fat or content of ketone bodies.     

The influence of various feedstuffs containing fat and protein on the digestibility of crude nutrients in young calves

Digestibility trials were carried out with calves, aged 3, 5, 7, 9, and 11 weeks, which were fed with feedstuffs of various energy and protein levels (various amounts of dried skim milk supplement with 146, 219, 323 g per day of the milk replacer Laktin) plus concentrate and hay. The purpose of the experiment was to find out what effect the amount of milk replacer varying daily had on the digestibility of the nutrients. The experiments confirm that the amount of milk replacer has a great influence on the digestibility of the crude fat. The amount of digestible crude fat consumed with the feed considerably influcenced the digestibility of the energy, it had little influence on the digestibility of the other nutrients, however. With increasing age the calves received more plant protein sources with a lower biologic value. Thus the digestibility of the protein in the complete ration was diminished as well. This shows that the digestibility was influenced by the protein quality, not, however, by the amount of crude protein. The digestibility of the dry matter andthe organic matter as well as of the N-free extractives in the feed ration diminished according to the changed composition with the increasing age of the animals; in constrast to this the digestibility of the crude fibres increased gradually.     

Growth and body composition of dairy calves fed milk replacers containing different amounts of protein at two feeding rates

Previous research has demonstrated that increasing the CP concentration from 16 to 26% in milk replacers fed to male preruminant dairy calves at 1.5% of BW (DM basis) daily resulted in increased ADG, G:F, and deposition of lean tissue. However, the effects of dietary CP would be expected to vary depending on ME intake. Here, male Holstein calves < 1 wk old were used to determine the effects of feeding rate and CP concentration of isocaloric, whey protein-based milk replacers on growth and body composition. After a 2-wk standardization period, calves were assigned randomly to an initial baseline group or to treatments in a 2 x 4 factorial arrangement of feeding rate (1.25 or 1.75% of BW daily, DM basis) and milk replacer CP concentration (14, 18, 22, or 26% of DM). No starter was offered, but calves had free access to water. After a 5-wk feeding period, calves were slaughtered and body composition was determined. Increasing the feeding rate increased (P < 0.05) ADG, G:F, empty-body gains of chemical components and energy, the percentage of fat in empty BW gain and in the final empty body, and concentrations of IGF-I and insulin in plasma. Increasing the feeding rate decreased (P < 0.01) percentages of water and protein in the empty body and decreased urea N in plasma. Increasing dietary CP concentration linearly increased (P < 0.05) ADG, body length, heart girth, and gains of water and protein but linearly decreased (P < 0.05) fat gain. As dietary CP increased, fat content in empty body gain decreased, and water and protein increased. Increasing CP concentration increased (quadratic, P < 0.02) G:F, with greatest efficiencies for calves fed 22% CP. Gross energetic efficiency (retained energy:intake energy) was greater (P < 0.05) for calves fed at 1.75% of BW daily. Efficiency of dietary protein use for protein gain was greater for calves fed at 1.75% of BW daily but was not affected by dietary CP. The ratio of protein gain to apparently digestible protein intake above maintenance decreased as dietary CP increased. Interactions (P < 0.05) of feeding rate and CP concentration for gains of water and protein indicated that when dietary CP was 26% the ME supply limited protein use by calves fed at 1.25% of BW daily. Body composition of preruminant calves can be markedly altered by manipulating the protein to energy ratio in milk replacers. These dietary effects on body composition and growth are not predicted by current NRC standards.     

Milk feeding and utilization of nutrients in clinically healthy calves and in calves with diarrhea

Digestibility of nutrients was determined in healthy calves and in those with diarrhoea at the age of two and three weeks. The total collection of feces and indigestible marker methods (with Cr2O3) were used. High equality of results and statistically non-significant differences between the method of a total collection of feces and indigestible marker one in the suckling calves (Tab. II) confirm the suitability of using these two methods to determine digestibility. Based on the composition and commercially recommended feeding guide of milk replacer, it is clear that it has lower digestible energy, Zn and Fe intake. Slightly higher digestible crude protein and Mg intake, optimum Ca and P intake, all these values were calculated for 1 kg of live weight (Tab. I). Nutrient contents is responsible for nutrient ratio which is unbalanced and for low contents of digestible energy (76.5 KJ per g of digestible crude protein) instead of recommended values of 100-110 KJ per of digestible crude protein in milk replacer in suckling calves. In six clinically healthy calves fed with milk replacer Laktavit twice a day, an apparent digestibility of organic matter was found to be 95.7 +/- 1.8%, crude protein 93.5 +/- 1.8%, fat 94.5 +/- 1.4%, carbohydrates 97.2 +/- 1.5%, Ca absorption was 86.5 +/- 2.8%, P 95.3 +/- 2.9%. There was a depressed absorption for Mg 43.4 +/- 6.8%, Fe 24.2 +/- 4.3% and Zn 36.8 +/- 3.5% (Tab. III).(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic reactions of calves to the feeding with Laktosan or unpasteurized whole milk]

The acid-base and other metabolic reactions to nutrition with Laktosan produced by two feed plants and with unpasteurized whole milk after transport to a dairy plant were studied in calves up to the ninth week of age. Laktosan feeding reduces the metabolic component of the acid-base balance; the use of a lower-quality Laktosan mixture, containing drum-dried milk, gives a picture of metabolic acidosis lasting about 11 days. The changes are cuased by an increased intensity of dissimilation, by the release of metabolic H+, and, in part, by the loss of bases during diarrhoea. With the use of low-quality Laktosan, the utilization of the nutrients of the feed ration is much lower than the utilization of the nutrients of unpasteurized milk or high-quality Laktosan. The use of high-quality Laktosan causes much lower acid-base changes, far from reaching pathological values. At the same time, the utilization of nutrients is higher than with the use of unpasteurized milk. This milk which cannot be considered microbially or chemically undamaged offers no advantages from the health-condition and economic point of view. The facts, revealed by the study, emphasize the high health and economic importance of the production of calf feed mixtures. At the same time the results show that enither milk nor Laktosan feeding provides enough magnesium for the calves to grow. Other metabolic aspects of different calf nutrition are discussed.     

Differences in monocarboxylic acid transporter type 1 expression in rumen epithelium of newborn calves due to age and milk or milk replacer feeding

The aim of the present study was to investigate whether besides age and solid feed intake, monocarboxylic acid transporter type 1 (MCT1) expression in the rumen epithelium of calves is affected by liquid feed type [whole milk (WM) or milk replacer (MR)]. Thirty bull calves at the mean age of 5 days were randomly allocated to five experimental groups (six calves/group). Six calves were slaughtered immediately after allocation to the trial (5 days of life), eighteen calves were fed MR and slaughtered at week intervals (on 12, 19, 26 days of life respectively), and six calves were fed WM and slaughtered at the 26 days of life. MCT1 protein abundance and the MCT1 mRNA level were investigated in the dorsal and ventral sack of the rumen. Solid feed intake and short‐chain fatty acids (SCFA) concentration in the rumen fluid increased linearly with calves' age. The amount of the MCT1 protein and mRNA in the dorsal sac of rumen as well as the amount of MCT1 protein in the cranial ventral sac of rumen also increased linearly with calves' age. Calves fed WM had greater solid feed intake in the last week of the study as compared to calves fed MR, but SCFA concentration in the rumen fluid was not different. MCT1 mRNA expression in the cranial dorsal sac of rumen and protein MCT1 expression in both dorsal and ventral cranial sack of the rumen were higher in calves fed WM as compared to calves fed MR. This study confirmed age‐dependent changes of MCT1 expression in the rumen epithelium of newborn calves and showed that its expression might be affected by liquid feed type.     

Oral and intramuscular intervention with dextriferron in growing male calves. 4. Development of food intake during the suckling period

The influence of oral and intramuscular ferridextrane intervention on the calves' absolute and relative consumption of skim milk, rearing feed for calves and lucerne hay in the 1st, 4th and 8th week of their stay in the weaning range of the rearing farm was investigated. The effect of iron substitution was dependent on the duration of keeping and of the experiment and, under conditions of the drinking regime given, manifested itself both in the development of the absolute and in the development of the relative skim milk intake, but not in that of dry feed consumption. The causes and consequences of the time dependence of the influence of iron intervention on feed consumption are discussed. In the 8th week of keeping the nutrient intake of the orally substituted group was between 8.0 and 9.0% higher than that of the control animals. With the drinking regime used, which led to a relatively quick development of dry feed consumption, differences between the test groups with regard to the consumption of concentrated feed and hay as well as the relative energy and protein quota from the fluid feed in relation to the complete energy and protein intake of the 8th week of keeping could not be proved. Based on these criteria, iron intervention was without influence on the stage of development of the ruminal digestion of the rearing calves reached at the end of the 56-day experiment. With a drinking regime which results in a relatively slow development of dry feed consumption, such an effect is certainly probable.     

影响奶牛繁殖性能的营养因素及其调控

本文对影响奶牛繁殖性能的营养因素及其饲养调控技术方面的研究进展进行了综合评述。结论认为奶牛营养状况与繁殖性能密切相关,随着遗传性能和饲养管理技术的改进,奶牛泌乳量得以迅速提高的同时,对营养需要量的要求也随之提高。营养需要量的提高常常导致奶牛特殊生理阶段发生能量负平衡,致使奶牛繁殖能力下降;高蛋白日粮有利于提高产奶量,却往往降低了繁殖性能;日粮中矿物质和维生素含量偏高或偏低以及比例不当都会影响奶牛的繁殖性能;奶牛营养的全过程,包括采食量及采食的营养成分水平都与奶牛的繁殖性能密切相关。     

复合酸度调控剂对犊牛生长性能、血气指标的影响

探讨代乳粉中添加复合酸度调控剂对0～3月龄犊牛生长性能、血气指标的影响。试验分为对照组和试验组,分别饲喂乳液pH值为6.2和5.0的代乳粉。每个处理6头犊牛,分别在试验开始后的0、14、28、42、56d测定每头犊牛的体重、体尺,每日记录每头犊牛代乳粉和开食料供料量和剩料量,观察每头犊牛的粪便形态和评分,并分别在0、14、42d采血测定血气指标。试验数据显示:与对照组相比,试验组犊牛各阶段的平均日增重有所提高,其中0～14、14～28、28～42、42～56d分别提高了5.6%、45.9%(P<0.05)、11.9%、5.8%;试验全期两组间平均日采食量、饲料转化率差异皆不显著(P>0.05);全期腹泻率试验组比对照组降低了13.9%,但差异不显著(P>0.05);28d体长指数试验组低于对照组(P<0.05)。试验开始(0d)和饲喂42d时各组间犊牛血气指标皆无差异(P>0.05);饲喂14d时试验组血液的pH值(P<0.05)、氧饱和度(P<0.05)、氧气分压、实际剩余碱储、标准碳酸氢盐浓度皆高于对照组,而二氧化碳分压显著低于对照组(P<0.05)。结果表明,在代乳粉中添加复合酸度调控剂后28d前对犊牛产生了一定作用,可提高14～28d阶段犊牛日增重,降低28d体长指数,并有降低腹泻率的趋势;犊牛血液的pH值、SO2升高而PCO2降低。     

Optimizing the growth and immune system of dairy calves by subdividing the pre-weaning period and providing different milk volumes for each stage

In systematically considering the advantages and disadvantages of complementarity in high or low milk feeding, novel milk feeding schemes involving altering the volume of supplied milk in different stages of the pre-weaning period but maintaining the total milk feeding volume were tested. Twenty-seven newborn male Holstein calves were selected and randomly assigned to 3 treatments. Calves in the control (CON) group were fed 7 L of milk daily from 4 to 66 d of age. Calves in the low-high (LH) group were fed 6 L of milk daily at the beginning, and then the daily feeding volume was later increased to 7 to 8 L of milk, which served as the early-period low-volume feeding group. The calves in the high-low (HL) group were fed 7 to 8 L daily at the beginning, and then the daily feeding volume was decreased to 6 L of milk, which served as the early-period high-volume feeding group. Then all calves were fed 3 L of milk daily from 67 to 70 d of age, weaned at 70 d of age, and then fed starter feed to 100 d of age. All calves had access to the starter feed from 15 to 100 d of age. The diarrheal condition of calves was recorded daily and the growth performance including the starter feed intake and body weight of calves was recorded at 70 and 100 d of age. Then, five 100-d-old calves from each treatment were sampled for measurement of plasma indices, ruminal morphology, and volatile fatty acids. When compared with the CON and LH groups, calves in the HL group exhibited a significantly increased body weight and lower diarrhoeal rate. When compared with the CON group, calves in the HL group exhibited a significantly increased average daily feed intake, ruminal epithelium papillae length, total volatile fatty acids, and percentages of propionate and butyrate. Moreover, the significantly increased plasma immunoglobulin G (IgG) content and a trend of decreased tumor necrosis factor-α (TNF-α) content (P = 0.083) were also identified in the HL group when compared with the CON group. Overall, the early-period high-volume feeding for calves produced greater body weight gain and a lower incidence of diarrhea.     

Utilization of alimentary ribonucleic acid in calf N-metabolism

In order to get hints concerning the utilisation of nucleic acids in the N-metabolism of ruminants, a N-balance experiment with not yet ruminating calves was carried out. An admixture of 0, 1.875 and 3.75% yeast ribonucleic acid (groups I-III) was given to a milk substitute feed with low purine and pyrimidine contents. The RNA admixture amounted to 10 resp. 20% of the diet protein-N. The daily feed per animal amounted to 1710 g. Apart from the N-balance the digestibility of RNA and some N-fractions in urine were registered. The excretion of nitrogen, RNA or desoxy ribonucleic acid in the feces of the calves was hardly changed by the RNA intake. Thus an extensive digestibility of RNA can be stated. The renale nitrogen excretion increased in group II by an amount which nearly corresponded to the RNA intake, and in group III it even increased overproportionally. As the N-balance showed, there was a low utilisation of the RNA-N of 12% (non-significant), whereas in group III the N-increase was negatively influenced. The N-excretion in urine connected with the RNA-intake could mainly be traced back to increased urea and allantoine values. The conclusions from these results were that nucleic acids of 10 to 20% of the feed protein are only of a low resp. no nutritive nitrogen value.     

The effect of unrestricted milk feeding on the growth and health of Jersey calves

This study was conducted to determine the effect of feeding high milk volumes on the growth rate, health and cross-sucking behaviour in group-fed Jersey calves. Three-day-old heifers (n = 120) in a seasonal calving dairy herd were randomly assigned to one of 6 treatment groups. Three groups received high milk volumes (HMV), consisting of ad libitum milk or milk replacer feeding twice a day, while 3 groups received restricted milk volumes (RMV), consisting of 2 l twice daily, during the pre-weaning period. After a pre-weaning period during which feeding was reduced to once daily, all calves were weaned at 42 days and monitored until 60 days of age. Adjusting for birth mass, birth date, dam parity and sire, average daily mass gain (ADG), both pre-weaning (days 0-42) and overall (days 0-60), was higher in HMV than in RMV calves (P < 0.001). After weaning, growth rates showed no differences and at 60 days of age the HMV calves maintained a 6.74 kg advantage in mean body mass (P < 0.001). The mean intake of dry starter feed was higher in RMV than in HMV calves. Overall feed conversion rate of HMV calves was 9.6 % better than RMV calves. However, the variable cost per kg mass gain was 12 % higher for HMV calves. In the RMV groups 75 % of calves showed cross-sucking behaviour pre-weaning and 18 % post-weaning, whereas in HMV calves the proportions were 2 % and 7 %, respectively. There was no significant effect of milk volume on the incidence of diarrhoea. We conclude that the feeding of high volumes of milk to Jersey calves has a positive effect on growth rate, without compromising health or reducing solid feed intake after weaning. However, the higher cost of such a feeding system may limit its implementation.     

Effects of milk intake on forage intake and performance of suckling range calves

A study to examine the relationships between milk intake, forage intake, and performance of Hereford-Angus suckling range calves was conducted during July, August, and September of 1984 and 1985. Twenty calves were used each year. The study was conducted at the Red Bluff Research Ranch located 56 km west of Bozeman, Montana. Average daily gain, milk intake (MI), forage digestibility, and fecal output (FO) were measured at 28-d intervals, beginning when the average calf age was 66 +/- 4 d. Milk intake was estimated using weigh-suckle-weigh techniques. Total fecal collections were used to measure FO. Forage digestibility and rates of passage were determined using nylon bag in situ techniques and external markers in ruminally cannulated calves of the same age. Fecal output by calves increased as body weight and age increased. Milk intake was higher (P less than .05) in 1985 than in 1984, but FO was higher (P less than .01) in 1984 than in 1985. Fecal output by calves was negatively correlated to MI in July (r = -.62; P less than .05) and August (r = -.56; P less than .05). No significant correlations were detected between MI and ADG (P greater than .10). Forage intake estimates were derived from FO, rate of passage, and in situ digestibility values. During July, calves consumed .3 kg more forage for each kilogram of reduction in fluid MI (P less than .05). In both August and September, calves consumed .6 kg more forage for each kilogram of reduction in fluid MI (P less than .10). Calves maintained similar digestible energy (DE) intake both years, although the source of DE varied.     

不同固液比例饲喂模式对断奶前后犊牛营养物质代谢及瘤胃发酵的影响

本试验旨在研究断奶前后犊牛在不同固液比例饲喂模式下营养物质代谢及其瘤胃发酵的异同,从而探索基于不同饲喂模式下的犊牛断奶方式。试验选用7日龄荷斯坦公犊牛36头,随机分成3组,每组12头,各组采用相同原料组成、相同营养成分的代乳粉和颗粒料。在总干物质饲喂量保持一致的情况下,改变固液饲料饲喂比例,形成3种饲喂模式组:高液体饲料比例(HL)组,28~56日龄内,颗粒料∶代乳粉保持在1∶2,56日龄断奶;对照(LS)组28~56日龄内,颗粒料∶代乳粉从1∶2逐步降低到1∶1,56日龄断奶;高固体饲料比例(HS)组,28~42日龄内,颗粒料∶代乳粉从1∶2逐步降低至1∶0,并于42日龄断奶。试验期77 d。分别于犊牛28、42、56和84日龄采集瘤胃液,35和63日龄进行断奶前后消化代谢试验。结果表明:断奶前,与HS组相比,HL、LS组犊牛总能代谢率相对较高,但差异不显著(P0.05);断奶后,HS组消化能代谢率、氮利用率及氮的生物学价值较HL组显著提高(P0.05)。与HL组相比,HS组84日龄瘤胃液微生物蛋白含量显著提高(P0.05)。3组间瘤胃液氨态氮浓度无显著差异(P0.05)。84日龄时,HS组犊牛瘤胃液总挥发性脂肪酸浓度和丁酸比例显著高于HL组(P0.05),各组间丙酸、戊酸比例无显著差异(P0.05)。综上可得,适量增加固体饲料饲喂比例有助于改善断奶前后犊牛瘤胃发酵环境,促进瘤胃微生物蛋白的合成,提高断奶后犊牛饲粮能量代谢率、氮的生物学价值及氮利用率;采用高固体饲料饲喂模式,犊牛在42日龄固体饲料采食量达到1.0 kg/d时实施断奶具有一定优势。     

Effect of protein : energy ratio in milk replacers on growth performance of goat kids

Two separate experiments were carried out to establish the effects of the protein:energy ratio in milk replacers on growth performance, plasma lipid concentrations and fatty acid composition in adipose tissue of male goat kids. In the first experiment there were 211 3-day- old goat kids and in the second experiment there were 121 kids aged 3-7 days. The animals were fed ad libitum for a period of 4 weeks on milk replacers containing either 11.5 or 9.5 g crude protein/MJ metabolizable energy. In essence, protein was exchanged with fat on a weight basis. Milk concentrations were increased from 160 to 190 g/l in experiment 1, from 150 to 180 g/l in experiment 2. There were significant increases in body weight and feed intake when the milk replacer with high protein : energy ratio was fed. Group mean average daily weight gain was 168 and 203 g for the groups with low and high dietary protein:energy ratio in experiment 1; for experiment 2 the values were 139 and 160 g. Average dry matter intake was 18 and 14% higher for the diet with high protein:energy ratio in experiments 1 and 2, respectively. There was no change in either feed conversion (feed:gain ratio) or energy conversion (weight gain:energy intake ratio). There were no consistent diet effects on plasma lipid concentrations. Dietary fatty acid composition was reflected by that of adipose tissue. The milk replacer with high protein:energy ratio produced a small increase in the contents of myristic and palmitic acid in adipose tissue.     

Levels of milk urea, plasma constituents and rumen liquid ammonia in relation to the feeding of dairy cows during early lactation

The study was undertaken to establish the relationships between milk and plasma urea levels and protein supply, using traditional and new measures of feed protein value. Samples of milk and plasma were taken before morning feeding twice weekly for the first 3 months post partum from 21 multiparous cows and 7 heifers. Samples of rumen fluid were collected every second week. The cows were distributed into 4 different feeding groups. Feeding regimens were factorial with respect to protein content of the concentrates (i.e. Low protein (Lp): 12.5% digestible crude protein (DCP) vs. High protein (Hp): 17.5% DCP) and concentrate allowances (i.e. Low energy (Le): substandard vs. High energy (He): standard). Silage was offered ad libitum. The within-animal coefficients of correlation between milk and plasma urea levels, and between milk urea levels and the levels of ammonia in the rumen fluid wer r = 0.88 (p less than 0.001) and r = 0.75 (p less than 0.001), respectively. Analysis of variance showed the following sources of urea variation to be significant: Protein balance in the rumen (PBV), intake of DCP, intake of amino acids absorbed in the intestine (AAT), intake of fattening feed units, and the individual animal factor. A similar tendency was found for the variation of ammonia in rumen fluid. The coefficients of determination (R2 model) were not increased by introducing protein balance (BADCP), the amount of PBV and AAT in the dry matter ingested, or the protein/energy ratio as alternative parameters of protein intake in the models. The levels of protein or energy intake did not significantly influence the levels of plasma albumin. The correlations between urea levels and other plasma indicators of metabolic status and liver function were generally low.