Predicting nutrient responses in poultry: future challenges

Predicting the response of poultry to nutrients has progressed to a stage where it is now not only possible to predict voluntary feed intake accurately, but broiler feeds and feeding programmes may now be optimised using the more advanced simulation models. Development of such prediction models has stimulated useful and purposeful research targeted at filling the gaps in our knowledge of critical aspects of the theory incorporated into these models. The aim of this paper was to review some of these past developments, discuss the controversy that exists in designing and interpreting response experiments, and highlight some of the most recent challenges related to the prediction of responses to nutrients by poultry. These latter include differences, brought about by selection for diverse goals, that have become apparent between modern broiler strains in their responses in feed intake and mortality, which are not independent of level of feeding or strain of broiler, as was previously believed. Uniformity, an important quality criterion in broiler processing, is also not independent of level of feeding, and the effect may now be predicted using stochastic models. It is not yet clear whether breast meat yield, the carcass component of broilers yielding the highest returns, is a function of the strain of broiler or simply that of the protein weight of the bird when processed. An important aspect of response prediction is dealing with constraints to performance: whereas it is relatively straightforward to simulate the potential performance of a broiler, such performance is often constrained by the physical, social and infectious environment, among others, providing a challenge to modellers attempting to predict actual performance. Some of these constraints to potential performance have not yet been adequately described, but are now receiving attention, suggesting that nutrient responses in poultry have the potential to be more accurately predicted in the future.     

Effect of lactulose on growth performance and intestinal morphology of pre-ruminant calves using a milk replacer containing Enterococcus faecium

The synthetic disaccharide lactulose is known to improve the intestinal microflora by stimulating the growth of selected probiotic bacteria in the gut. In our experiment the effects of lactulose in combination with the probiotic bacteria Enterococcus faecium on growth performance and morphology of the bovine intestine were examined. Calves aged 39 ± 2 days were randomised to three feeding groups (no. = 14 each group): control (L0), fed milk replacer (MR) containing E. faecium; a lactulose group (L1) containing additional 1% lactulose and a second lactulose group (L3) containing 3% lactulose dry matter. The calves were weighed weekly. After 19 weeks the calves were slaughtered and tissues were collected for histological studies. The average daily live weight gain tended to be higher (P < 0.1) for L3 (1350 g/day) than L0 (1288 g/day). Compared with L0, a reduction (P < 0.001) of ileal villus height due to lactulose treatment of approximately 14% in group L1 and 20% in L3 was determined. A significant decrease in the depth of the crypts about 12% in L1 and 8% in L3 was detected in the caecum. The surface area of lymph follicles from Peyer's patches was decreased by lactulose treatment. Results show that lactulose has an effect on the morphology of intestine. A significant effect on growth performance can not be confirmed. However, results permit the conclusion that lactulose feeding has the tendency to increase growth performance.     

Infradian rhythm in hematology,cell mediated immunity and serum micronutrient concentration around peripartum periods in high yielding crossbred cows before and after micronutrient supplementation

Alteration in hematology and cell-mediated immunity around peripartum periods before and after micronutrient supplementation was studied in this investigation. Twelve (12) high-yielding cross-bred cows in advanced pregnancy were selected for the experiment and divided into two equal groups viz. supplemented (n = 6) and unsupplemented (n = 6). Supplemented animals were provided with a micronutrient mixture (@ 25 g per cow) as per the recommendation of NRC over the normal feeding. Unsupplemented group of cows were kept as control with standard farm feeding management. Blood samples (15 ml/cow) were collected from all the animals during days 30th, 15th, and 7th before calving, on the day of calving, and during days 7th, 15th, and 30th after calving and analyzed for hematology viz. hemoglobin (Hb), total erythrocyte counts (TEC), total leukocyte counts, and differential leukocyte counts. In vitro phagocytic index (PI) of neutrophils and lymphocyte proliferation response (LPR) were also evaluated. Copper (Cu), zinc (Zn), manganese, and selenium (Se) concentrations in serum were estimated by atomic absorption spectrophotometer. The Hb concentration was found to be significantly (p < 0.01) higher in supplemented group compared to the unsupplemented group of cows. There were no significant differences in Hb concentration during different days of peripartum in both the group of cows. There was a significantly (p < 0.001) higher TEC in supplemented group compared to unsupplemented group of cows, though it did not vary significantly between different days of peripartum in both the group of cows. There was a significantly (p < 0.001) higher PI in supplemented group compared to the unsupplemented group of cows. In both the groups, the PI of blood neutrophils was significantly (p < 0.001) lower during calving. The LPR did not differ significantly between the groups, but it differed significantly (p < 0.01) between different days of peripartum and was lowest on the day of calving in both the groups. The Cu, Zn, and SE concentration was found to be significantly (p < 0.01) higher in supplemented group compared to the unsupplemented group of cows, but remained unaltered throughout the peripartum period. The study indicated that there was a marked immune depression around peripartum (15 days precalving to 15 days postcalving) in terms of in vitro phagocytic activity of blood neutrophils and in vitro LPR. Supplementation of micronutrients improves the hematological status as well as immune status, so it was recommended to supplement these micronutrients for better productivity and disease resistance in high-yielding cross-bred cows around peripartum.     

Effects of different levels of ergot in concentrate on the health and performance of male calves

A number of studies dealing with the effects of ergot and ergot alkaloids on the health and performance of poultry and pigs were reported in the past, but only a few studies and field reports are available for ruminants. Therefore, a dose-response study was carried out with calves since young animals are considered to be especially sensitive to ergot. A total of 35 male Holstein calves were randomly assigned to three feeding groups after one month of feeding milk replacer. The mean initial live weight of the calves was 49.4±5.7 kg. One control group was fed an ergot-free concentrate (n=12), one group an ergot proportion of 1000 mg/kg in the concentrate (n=ll), and another group was fed a concentrate containing 5000 mg/kg ergot (n=12). Hay, grass silage and water were available forad libitum consumption, whereas the daily concentrate portion was restricted to 2 kg. Live weight, health parameters and feed intake were monitored over the experimental period of 84 days. In addition, blood samples were taken from theVena jugularis at the beginning and at the end of the experiment and analysed for ergot alkaloids and liver parameters. Total dry matter intake, live weight gain and feed-to-gain ratio were not significantly influenced by increasing ergot proportions when the whole experimental period was considered, although there was a trend for an ergot-related decrease in concentrate intake during the first 6 weeks of the experiment. After this period of time, it seemed that calves got used to the presence of ergot in the concentrate and were able to adjust their intake to the level of the control group. Moreover, health and liver parameters, such as total bilirubin, aspartate aminotransferase, glutamate dehydrogenase, gamma-glutamyl transpeptidase and creatine kinase in the serum were not significantly influenced by dietary treatments. Concentrations of the individual ergot alkaloids in serum were lower than the detection limits of the applied HPLC-method. In conclusion, it can be assumed that an ergot contamination of the concentrate up to 5000 mg/kg resulted in a transient depression of concentrate intake by the calves. However, no significant effects on health and performance could be detected when the entire test period of 84 days was considered. Presented at the 28^th Mykotoxin-Workshop, Bydgoszcz, Poland, May 29–31, 2006     

利用穗粒结构对水稻产量的拟合及预测

文章首先讨论了模型的拟合效果和预测效果的区别,给出了相应的估算方法,同时也讨论了抽样观测值大小对预测精度的影响,并结合实例说明如何从一组模型中选择一预测效果最好的模型．对1992年中国水稻研究所富阳实验基地和绍兴县测产样本点的数据,得到预测效果较好的模型为：产量预测值=理论产量 线性纠正估计,其中线性纠正的形式对两组数据略有不同．     

Field studies on the population dynamics of Biomphalaria glabrata, intermediate host of Schistosoma mansoni on the West Indian Island of St. Lucia

Growth curves, calculated for field populations of B. glabrata, were not materially affected by habitat, altitude or season. A mean growth curve was therefore used to estimate the age-frequency distribution of snails in successive field samples. These data permitted the construction of ecological life tables and the estimation of r, the intrinsic rate of natural increase (or decrease) of the different populations. The calculated values of r were inserted in a simple model of unlimited population growth but the resultant curves poorly represented the observed data. A model for unlimited growth was more satisfactory for pond and marsh populations but, apparently, immigration made it less satisfactory for stream and banana drain populations. Nevertheless, r may still be of value in predicting repopulation rates in certain habitats after a mollusciciding which does not kill the entire snail population.     

Effects of rumen-escape starch and coarseness of ingredients in pelleted concentrates on performance and rumen wall characteristics of rosé veal calves

The objective was to study the effect of rumen-escape starch and coarseness of ingredients in pelleted concentrates on performance, carcass quality and rumen wall characteristics in rosé veal calf production. Two alternative concentrates (Coarse and Slow) were compared with a traditional (Control) concentrate. Control was based on finely ground ingredients, whereas in Coarse, the same ingredients were coarsely ground resulting in a mean particle size before pelleting of 1.5 in Coarse and 0.6 mm in Control. Slow compared with Control and Coarse contained finely ground sorghum and corn instead of barley and wheat which increased the amount of rumen-escape starch to 59 compared with 22 g/kg in Control and Coarse. All concentrates had the same total starch (362 g/kg), NDF (168 g/kg), CP (154 g/kg) and DE (15.5 MJ/kg DM) content and a pellet diameter of 3.5 to 4 mm. Use of an ‘indicator of starch digestibility’ method gave a value of 98.6% for Control and Coarse and 91.1% for Slow (P < 0.001). A total of 57 Holstein bull calves (n = 19 per treatment) were offered one of the three concentrates ad libitum from weaning 2 1/2 months of age) to slaughter (<10 months of age). Concentrate intake was recorded individually. Barley straw was available ad libitum but intake was not recorded. Average daily gain (1.43 kg/day), concentrate conversion efficiency (3.7 kg DM concentrate/kg gain), LW at slaughter (386 kg), carcass weight (194 kg) and EUROP conformation (3.9) were not affected by type of concentrate (P > 0.05). Papillae length and shape evaluated in atrium ruminis and the cranial part of the ventral rumen sac at slaughter were not affected by type of concentrate (P > 0.05). Rumen wall characteristics showed degrees of plaque formation (i.e., papillary aggregation), hyperaemia and necrotic areas in all treatment groups, but with no general difference between type of concentrate (P > 0.05). Incidence of liver abscesses (LAs, 16%) was not affected by type of concentrate (P > 0.05). There were no differences in performance or rumen wall characteristics between liver-abscessed and non-abscessed calves. The results show a high level of production performance with the three types of pelleted concentrates and indicates that neither the more coarse ingredients nor the additional rumen-escape starch tested, when fed ad libitum, could improve rumen wall characteristics or reduce LAs of rosé veal calves.     

Effects of lactoferrin feeding on growth,feed intake and health of calves

Abstract

Lactoferrin (LF) exhibits a broad spectrum of anti-microbial properties and may have regulatory functions in the immune system. In the present study, 40 calves (20 males, 20 females) were used to examine the effects of supplemental bovine LF added to colostrum and milk replacer (at 0.16%) on health, weight development and feed intake during a 70-day experimental period. The calves were allocated to a treatment group (n = 20) and a control group (n = 20); the groups were balanced in terms of sex, live weight and date of birth. Body weight and feed intake were measured at regular intervals. Blood and colostrum samples were collected to determine the content of IgG. In addition, colostrum and milk replacer samples were analysed for their LF concentrations. Significantly higher IgG values were observed in the LF treated than in the control group during the entire feeding experiment from week 2 to week 6. Calves receiving LF had less days of disease with less serious cases of diarrhoea than the control group. Body weight and feed intake were not significantly different between the treatments; in male calves LF-treated animals tended towards higher weight gains. This study indicates that LF is advantageous for health and may therefore be a beneficial supplement in the diets for neonatal calves.     

小麦异交群体连续歧化选择的RAPD分析

利用太谷核不育基因构建的遗传变异丰富的基础群体DNS2,进行了连续5轮歧化选择。本论文从不同的世代中,选择了10个子群体进行RAPD分析。采用7个引物扩增出116个位点,从基因频率和表型带两个角度的分析都表明,群体具有丰富的遗传变异。整个群体总的多态位点百分率达88.79,总杂合度为0.3143。子群体内（间）遗传距离的结果显示：子群体内的遗传差异小于子群体间的遗传差异;各选择子群体与未选群体间都有较大的遗传距离;随着选择轮次的增加,株高选择子群体间的遗传距离逐渐增大;对同一性状进行选择的子群体间世代内（间）平均遗传距离小于对不同性状进行选择的子群体内（间）的遗传距离。RAPD分子聚类结果显示出对同一性状进行选择的子群体聚在一起,反映了对株高选高的选择效果比较明显。Abstract:A base population was established through multi-parent random crossing by using Taigu dominant male-sterile wheat,and then five cycles of 2-way selection for four quantitative characters were conducted.The dynamic changes of genetic structures in the open-pollinated wheat population were examined by RAPD technique.Seven primers in RAPD analysis amplified 116 sites.The results of gene frequencies and phenotypic bands showed abundant genetic variations existed in the population.The percentage of polymorphic loci was 8879,and the average heterozygosity was 0.3143 in the whole population.The genetic distance of RAPD showed as follows :① The genetic distance within a subpopulation was lower than that between every two subpopulations.② Each subpopulation had considerable divergence compared with unselected population.③ The genetic distances between the subpopulations which were selected for plant height gradually increased accompanied with the selection.④The genetic distance between subpopulations which were selected for the same character was lower than that were selected for different characters both in the same generation and among different generations.The cluster results of RAPD genetic distance demonstrated that the subpopulations selected for the same character going to one cluster.It also showed that the selective effect of increasing plant height was obvious.