Preweaning period is a critical window for rumen microbial regulation of average daily gain in Holstein heifer calves

Background Rumen bacterial groups can affect growth performance,such as average daily gain(ADG),feed intake,and efficiency.The study aimed to investigate the inter-relationship of rumen bacterial composition,rumen fermentation indicators,serum indicators,and growth performance of Holstein heifer calves with different ADG.Twelve calves were chosen from a trail with 60 calves and divided into higher ADG(HADG,high pre-and post-weaning ADG,n=6)and lower ADG(LADG,low pre-and post-weaning ADG,n=6)groups to investigate differences in bacterial composition and functions and host phenotype.Results During the preweaning period,the relative abundances of propionate producers,including g_norank_f_Butyricicoccaceae,g_Pyramidobacter,and g_norank_f_norank_o_Clostridia_vadin BB60_group,were higher in HADG calves(LDA>2,P<0.05).Enrichment of these bacteria resulted in increased levels of propionate,a gluconeogenic precursor,in preweaning HADG calves(adjusted P<0.05),which consequently raised serum glucose concentrations(adjusted P<0.05).In contrast,the relative abundances of rumen bacteria in post-weaning HADG calves did not exert this effect.Moreover,no significant differences were observed in rumen fermentation parameters and serum indices between the two groups.Conclusions The findings of this study revealed that the preweaning period is the window of opportunity for rumen bacteria to regulate the ADG of calves.

Bacteria colonization and gene expression related to immune function in colon mucosa is associated with growth in neonatal calves regardless of live yeast supplementation

Background As Holstein calves are susceptible to gastrointestinal disorders during the first week of life,understanding how intestinal immune function develops in neonatal calves is important to promote better intestinal health.Feeding probiotics in early life may contribute to host intestinal health by facilitating beneficial bacteria colonization and developing intestinal immune function.The objective of this study was to characterize the impact of early life yeast supplementation and growth on colon mucosa-attached bacteria and host immune function.Results Twenty Holstein bull calves received no supplementation(CON)or Saccharomyces cerevisiae boulardii(SCB)from birth to 5 d of life.Colon tissue biopsies were taken within 2 h of life(D0)before the first colostrum feeding and 3 h after the morning feeding at d 5 of age(D5)to analyze mucosa-attached bacteria and colon transcriptome.Metagenome sequencing showed that there was no difference inαandβdiversity of mucosa-attached bacteria between day and treatment,but bacteria related to diarrhea were more abundant in the colon mucosa on D0 compared to D5.In addition,q PCR indicated that the absolute abundance of Escherichia coli(E.coli)decreased in the colon mucosa on D5 compared to D0;however,that of Bifidobacterium,Lactobacillus,and Faecalibacterium prausnitzii,which could competitively exclude E.coli,increased in the colon mucosa on D5 compared to D0.RNA-sequencing showed that there were no differentially expressed genes between CON and SCB,but suggested that pathways related to viral infection such as“Interferon Signaling”were activated in the colon mucosa of D5 compared to D0.Conclusions Growth affected mucosa-attached bacteria and host immune function in the colon mucosa during the first 5 d of life in dairy calves independently of SCB supplementation.During early life,opportunistic pathogens may decrease due to intestinal environmental changes by beneficial bacteria and/or host immune function.Predicted activation of immune function-related pathways may be the result of host immune function development or suggest other antigens in the intestine during early life.Further studies focusing on the other antigens and host immune function in the colon mucosa are required to better understand intestinal immune function development.

Effect of organic mineral supplementation in reducing oxidative stress in Holstein calves during short‑term heat stress and recovery conditions

Background This study investigated the effects of inorganic and organic minerals on physiological responses,oxidative stress reduction,and rumen microbiota in Holstein bull calves(123.81±9.76 kg;5 months old)during short-term heat stress(HS)and recovery periods.Eight Holstein calves were randomly assigned to four treatment groups:no mineral supplementation(Con),inorganic minerals(IM),organic minerals(OM),and high-concentration organic minerals(HOM)and two thermal environments(HS and recovery)using 4×2 factorial arrangement in a crossover design of four periods of 35 d.Calves were maintained in a temperature-controlled barn.The experimental period consisted of 14 d of HS,14 d of recovery condititon,and a 7-d washing period.Results Body temperature and respiration rate were higher in HS than in the recovery conditions(P<0.05).Selenium concentration in serum was high in the HOM-supplemented calves in both HS(90.38μg/dL)and recovery periods(102.00μg/dL)(P<0.05).During the HS period,the serum cortisol was 20.26 ng/mL in the HOM group,which was 5.60 ng/mL lower than in the control group(P<0.05).The total antioxidant status was the highest in the OM group(2.71 mmol Trolox equivalent/L),followed by the HOM group during HS,whereas it was highest in the HOM group(2.58 mmol Trolox equivalent/L)during the recovery period(P<0.05).Plasma malondialdehyde and HSP70 levels were decreased by HOM supplementation during the HS and recovery periods,whereas SOD and GPX levels were not significantly affected(P>0.05).The principal coordinate analysis represented that the overall rumen microbiota was not influenced by mineral supplementation;however,temperature-induced microbial structure shifts were indicated(PERMANOVA:P<0.05).At the phylum level,Firmicutes and Actinobacteria decreased,whereas Fibrobacteres,Spirochaetes,and Tenericutes increased(P<0.05),under HS conditions.The genus Treponema increased under HS conditions,while Christensenella was higher in recovery conditions(P<0.05).Conclusion HOM supplementation during HS reduced cortisol concentrations and increased total antioxidant status in Holstein bull calves,suggesting that high organic mineral supplementation may alleviate the adverse effects of HS.

A meta-analysis on the effects of probiotics on the performance of pre-weaning dairy calves

Background:Probiotics have been used in livestock production for many years,but information on their benefits during the early life of calves is inconsistent.This study aimed to assess the effects of probiotics on the performance of pre-weaning dairy calves and identify the factors influencing their effect sizes.Results:Forty-nine studies were selected for meta-analysis based on the inclusion and exclusion criteria.The study qualities were evaluated using a predefined risk assessment tool following GRADE guidelines.Meta-analysis results showed that probiotics increased the growth performance(body weight by 1.988 kg and average daily gain by40.689 g/d),decreased digestibility and feed efficiency(feed conversion rate by 0.073),altered rumen parameter(decreased acetate by 2.815 mmol/L and increased butyrate by 0.788 mmol/L),altered blood parameter(decreased AST by 4.188 U/L,increased BHBA by 0.029 mmol/L and IgG by 0.698 g/L),increased faecal parameter(faecal bacteria counts by 0.680 log10CFU/g),based on the strict criteria(P_(SMD)<0.05,I^(2)<50%).Additionally,probiotics increased digestibility and feed efficiency(starter dry matter intake by 0.034 kg/d and total dry matter intake by 0.020 kg/d),altered blood parameter(increased IgA by 0.313 g/L,IgM by 0.262 g/L and total antioxidant capacity by 0.441 U/mL,decreased MDA by 0.404 nmol/mL),decreased faecal parameter(faecal score by 0.052),based on the loose criteria(P_(SMD)<0.05,I^(2)>50%).Regression and sub-group analyses showed that probiotic strains,supplementation dosage,and methods significantly affected the performance of calves.The probiotics supplied with more than 9.5 log10CFU/d significantly increased IgA and IgM contents(P_(SMD)<0.05).Additionally,the compound probiotics significantly increased TDMI,IgA,and IgM(P_(SMD)≤0.001).Furthermore,probiotics supplemented in liquid(whole milk or milk replacer)significantly increased TDMI and decreased faecal score(P_(SMD)<0.05),while in whole milk,they significantly increased body weight,IgA,and IgM(P_(SMD)<0.001).Conclusions:Probiotics could improve the growth performance,feed intake and efficiency,rumen fermentation,immune and antioxidant capacity,and health of pre-weaning calves.However,the effect sizes were related to the dosage,composition,and supplementation methods of probiotics.

MRI在Legg-Calve-Perthes disease中的应用

目的探讨LCP病的MRI表现和诊断价值。方法回顾性分析14例LCP病(15髋)临床和MRI资料,研究LCP病不同分期MRI影像学表现。结果缺血坏死期,2髋;血运重建期,6髋;修复期,7髋。MRI显示髋关节滑膜炎(15髋),关节积液(15髋),关节面滑膜侵蚀(5髋),骨髓水肿(7髋),髋臼和股骨头软骨增厚(6髋),扁平髋(2髋),股骨干骺端和股骨头骨骺间骨桥(3髋)。结论 MRI是评价LCP病有效工具,可应用于诊断股骨头坏死,为疾病准确分期、各种并发症的发现及患者预后,提供重要信息;指导制定非手术和手术治疗方案具有重要意义。此外MRI还可以鉴别其它儿童髋关节疾病。

Effect of Different Protein Levels on Nutrient Digestion Metabolism and Serum Biochemical Parameters in Calves

The current study has been performed to examine the effects of different dietary protein levels on the growth, nutrient digestion and absorption, as well as biochemical parameters in calves. Nine healthy newborn calves were selected, randomly divided into 3 groups and fed 3 milk replacers with different protein levels （18, 22, and 26%）, respectively. Five period-digestion-metabolism trials were taken between 12-20, 22-30, 32-40, 42-50, and 52-60 days after birth. All 3 groups showed a similar growth curve during 11 to 61 experimental days, however, the growth rate of the 22% crude protein （CP） group was 8.89% higher than that of the 18% CP group and 19.48% higher than that of the 26% CP group, respectively. The apparent digestibility of dry material （DM） declined gradually with age, whereas, the apparent digestibility of N, extract ether （EE） rose slightly. Compared to the 22% CP and 26% CP group, calves fed with 18% CP apparently had a lower digestibility than DM, EE, and nitrogen （N）. The average apparent digestibilities of N were 69.39, 75.36, and 74.55%, respectively. Both the apparent digestibility and retention of calcium （Ca） and phosphorus （P） were steady throughout the experiment, but the average apparent digestibility of P in the 26% CP group was only 63.83%, which was markedly lower than that of the 18% CP group （70.40%） and 22% CP group （69.73%）. In addition, the serum concentrations of total protein （TP）, albumin （ALB）, and globulin （GLOB） of the 22% CP group were higher than those in the 18% CP and 26% CP groups. The urea N （BUN） content in the 18% CP group, on the other hand, was significantly lower than that of the other two groups. The highest glucose （GLU） concentration was found in the 22% CP group （5.38 mmol L^-1）, at the end of the trials. The protein levels in the milk replacer affected the digestion metabolism of nutrition and the serum biochemical parameters of calves at different physiological phases. Calves fed with 22% CP milk replacer had a better growth performance than the other groups.

Effects of different feeding methods and space allowance on the growth performance, individual and social behaviors of Holstein calves

The importance of nutrient provisions and weaning methods for calves has been well established over the past few years,while as increasing interest has focused on contribution of animal behavior and their overall performance in production regimes.The present study investigated the effects of feeding methods and space allowance on growth performance,individual and social behaviors in Holstein calves.Twenty-four Chinese Holstein male and female calves were allocated to either an individual or group of 6 and fed either with a bucket or a teat.Milk replacer,calf starter,and Chinese wildrye were offered during the experiment.A fecal index used in the present study was defined as the total fecal scores/total number of calves in each treatment.The results showed that there was no significant difference among the 4 treatments in terms of feed intake,body weight,average daily gain,and fecal index.For the feeding behaviors,the ingesting milk time and ingesting milk rate were significantly affected by space allowance,while the feeding methods showed a significant influence on the bunting behavior of the calves.There was no significant difference among the 4 treatments in terms of licking fixtures,self-grooming,and lying down behaviors,irrespective of the feeding method or space allowance.However,sucking an empty bucket or the teat was significantly affected by the feeding method.Several selected group behaviors were examined in the present study,and similar values for sniffing the other calves,social grooming,and cross-sucking behaviors were observed.Overall,the present study demonstrated that different feeding methods and space allowances had a significant effect on the feeding behavior of calves,while the feed intake,growth performance,health condition,individual and group social behaviors were not significantly influenced.Furthermore,under intensified production systems,Holstein calves raised in a group may obtain a similar production performance,thus reducing management input and profitability compared with those kept individually.However,there may be competition during the feeding period.

Review： Utilization of yeast of Saccharomyces cerevisiae origin in artificially raised calves

Yeast of Saccharomyces cerevisiae（SCY） origin has over long time been incorporated into domestic animal diets. In calves, several products have offered improved performance and health. Although several types of research have been completed, the mode of action of SCY is not clear in calves. Under this review, we have highlighted the works available in the literature on the use of SCY in calves performance, health, immunity, and the gut environment. Both active live yeast and yeast culture have positive effects on growth, rumen, small intestines, immunity and general health of the calf. Specifically, SCY can improve DMI, growth, feed efficiency and reduce diarrhea in calves. Furthermore, subtle improvements are seen in rumen fermentation（increased butyrate production） and rumen papillae growth. These positive results are, however, more pronounced in calves that are under stress or exposed to significant levels of disease-causing agents. There is a need for further research in areas such as gut morphology, gut microbiology and immunity using latest molecular methods to fully understand how SCY helps the growth and development of calves.

Effects of dietary forage to concentrate ratio and wildrye length on nutrient intake, digestibility, plasma metabolites, ruminal fermentation and fecal microflora of male Chinese Holstein calves

Twenty-eight male, weaned Chinese Holstein calves（（156.8±33.4） kg） were used to investigate the effects of dietary forage to concentrate ratio（F：C） and forage length on nutrient digestibility, plasma metabolites, ruminal fermentation, and fecal microflora. Animals were randomly allocated to four treatments in a 2×2 factorial arrangement： whole-length forage（WL） with low F：C（50：50）; WL with high F：C（65：35）; short-length forage（SL） with high F：C（65：35）; and SL with low F：C（50：50）. Chinese wildrye was used as the only forage source in this trial. The grass in the SL treatments was chopped using a chaff cutter to achieve small particle size（-50% particles 〉19 mm）. Dry matter intake（DMI） and organic matter（OM） intake was increased by increasing both F：C（P〈0.01） and forage length（FL）（P〈0.05）, while acid detergent fiber（ADF） and neutral detergent fiber（NDF） intakes were only increased by increasing the F：C（P〈0.01）. The digestibility of NDF was increased as the FL increased（P〈0.01）, and it was also affected by interaction between F：C and FL（P〈0.05）. Cholesterol（CHO）（P〈0.01）, leptin（LP）（P〈0.05）, and growth hormone（GH）（P〈0.01） concentrations in plasma were increased as dietary F：C increased. A significant increase in plasma triglyceride（TG）（P〈0.01）, insulin（INS）（P〈0.05）, and GH（P〈0.01） levels was observed with decreasing dietary FL. Ruminal p H values of calves fed with low F：C diets were significantly lower than those in high F：C treatment（P〈0.05）. Increasing the F：C enhanced ruminal acetic acid（P〈0.05） and acetic acid/propionic acid（P〈0.01）. Fecal Lactobacillus content was significantly higher, while Escherichia coli and Salmonella contents were significantly lower in WL and high F：C groups（P〈0.05）. Lower fecal scores（higher diarrhea rate） were observed in calves fed with SL hay compared to WL hay（P〈0.05）. Denatured gradient gel electrophoresis（DGGE） bands and richness index（S） were significantly affected by the interaction between F：C and FL（P〈0.05）, under high F：C, band numbers and richness index from WL group were higher than that from SL group（P〈0.05）, whereas there were no differences between WL andSL groups under low F：C（P〉0.05）. Microflora similarity was 50–73% among the different treatments. It is concluded that the WL with high F：C（65：35） diet is suitable for weaned calves.

Effects of Feeding Programs Based on One or Two Milk Replacer Daily Meals on Growth, Solid Feed Intake and Rumen Fermentation and Development of Dairy Calves

Sixteen Holstein calves were used to study the effects of two feeding programs (FP) on growth, intake, rumen development and ruminal metabolism from birth to weaning. Two feeding programs based on milk replacer (MR) were tested: a once a day (OAD) MR (200 g/L) distribution vs. a standard twice a day (TAD) MR (125 g/L) distribution. All calves received water, wheat straw and a starter concentrate ad libitum. Four calves per group were slaughtered at weaning and rumen epithelium from the ventral sac was sampled for papillae (RP) density. Results showed that the FP had no effect on body weight of calves and total feed intake. From day 42 to day 56, ruminal pH was lower (P = 0.036) and ruminal oxydo-reducing potential was higher (P = 0.001) in OAD than TAD calves. Ruminal total volatile fatty acid (VFA) concentrations did not significantly differ between FP. From day 21 to day 63, butyrate ruminal concentration was significantly higher in OAD than TAD calves (5.17 vs 3.95 mmol/L). This probably explained the higher development of RP in calves fed once daily. Finally, the tested feeding system based on a once daily MR distribution affects the concentrate feeding pattern of calves.

Gut health,stress,and immunity in neonatal dairy calves:the host side of host-pathogen interactions

The cumulative evidence that perinatal events have long-lasting ripple effects through the life of livestock animals should impact future nutritional and management recommendations at the farm level. The implications of fetal programming due to malnutrition, including neonatal survival and lower birth weights, have been characterized,particularly during early and mid-gestation, when placental and early fetal stages are being developed. The accelerated fetal growth during late pregnancy has been known for some time, while the impact of maternal stressors during this time on fetal development and by extent its postnatal repercussions on health and performance are still being defined.Maternal stressors during late pregnancy cannot only influence colostrogenesis but also compromise adequate intestinal development in the fetus, thus, that further limits the newborn's ability to absorb nutrients, bioactive compounds, and immunity(i.e., immunoglobulins, cytokines, and immune cells) from colostrum. These negative effects set the newborn calf to a challenging start in life by compromising passive immunity and intestinal maturation needed to establish a mature postnatal mucosal immune system while needing to digest and absorb nutrients in milk or milk replacer. Besides the dense-nutrient content and immunity in colostrum, it contains bioactive compounds such as growth factors, hormones, and cholesterol as well as molecular signals or instructions [e.g., microRNAs(miRNAs) and long non-coding RNAs(lncRNAs)] transferred from mother to offspring with the aim to influence postnatal gut maturation. The recent change in paradigm regarding prenatal materno-fetal microbiota inoculation and likely the presence of microbiota in the developing fetus intestine needs to be addressed in future research in ruminants. There still much to know on what prenatal or postnatal factors may predispose neonates to become susceptible to enteropathogens(e.g., enterotoxigenic Escherichia coli), causing diarrhea. From the host-side of this host-pathogen interaction, molecular data such as fecal RNA could, over time, help fill those gaps in knowledge. In addition, merging this novel fecal RNA approach with more established microbiome techniques can provide a more holistic picture of an enteropathogenesis and potentially uncover control points that can be addressed through management or nutrition at the farm level to minimize preweaning morbidity and mortality.

Effects of Supplemental Feeding of Probiotics during Lactation on Rumen Microflora of Calves after Weaning

For the experiment, 8 newborn male Holstein calves were selected that had the same feeding environment, and were of similar ages. They were randomly divided into 2 groups, with 4 in each group. The treatments consisted of feeding active probiotics (Group P) and a normal fed control group (Group C). The growth performance and blood indices were measured;rumen fluid samples were collected after weaning, and 16SrDNA sequencing and LC-MS metabolome detection were performed. Compared with the control group, relative abundances of Deltaproteobacteria, Desulfovibrionales, Bacteroidales_ BS11_gut_group, Desulfovibrionaceae, Bacteroidales_S24-7_group, Acetobacteraceae, Ruminococcaceae_NK4A214_group, Asaia, [Ruminococcus] gauvreauii_group, Desulfovibrio, Kingella, Selenomonas, Lachnoclostridium in group P were significantly different (P < 0.05). In group P, the metabolite of 2-methylbenzoic acid and myo-inositol were significantly increased (P < 0.05). These results showed that compared with normally fed calves, the growth performance and blood indices of probiotic-fed calves were changed, but the differences were not significant. Probiotic-fed calves showed significant differences in rumen fluid and a small number of metabolites, which were mainly involved in the pathway of carbohydrate metabolism. It proves that the supplemental active probiotics had an effect on the rumen microflora.

Milk Replacer Acidification for Free-Access Feeding: Effects on the Performance and Health of Veal Calves

Objectives of this study were to investigate the effects of milk replacer (MR) acidification for free- access feeding on pre- and post-weaning performance, morbidity and mortality of calves. Calves were randomly assigned to free-access feeding of acidified (ACID, n = 31) or non-acidified (NON, n = 31) MR, and weaned at 42 days. ACIDMR was prepared to pH 4.0 - 4.5 using formic acid. Intakes were measured daily and weights weekly. Samples of ACID and NON MR were analyzed for coliform and aerobic bacterial growth. After weaning, calves transitioned to a grain-fed veal diet, weighed every 2 weeks. At slaughter (approximately 6 months of age), lungs were evaluated for gross pathological changes and dressed carcass weights were obtained. Generalized linear mixed models were constructed to examine the effects of MR acidification. Differences by treatment group for pre- and post-weaning morbidity and mortality were tested using Pearson’s χ2 and Fisher’s exact tests. ACID calves consumed less MR than NON (10.6 vs. 11.7 L/d, P = 0.02). Acidification tended to promote earlier onset of starter ration consumption (32.0 vs. 39.5 d, hazard ratio = 1.5, P = 0.07), but did not affect average daily starter ration or water intakes across the pre-weaning period. ACID and NON calves did not differ for BW at weaning, pre- or post-weaning ADG or dressed carcass weight. ACID MR had less coliform (P < 0.001) and aerobic bacterial growth (P < 0.001) than NON MR, but odds of disease treatment and mortality did not differ. ACID calves tended to have lower odds of pulmonary lesions during post-mortem inspection than NON calves (OR = 0.3, P = 0.07). These results indicate that under free-access feeding conditions, acidification limited bacterial growth and MR intake, but there were no long-term impacts of acidification on calf performance or health. In conclusion, acidification to pH 4.0 - 4.5 will significantly reduce bacterial growth in milk fed to calves.

Interactions of copper,cadmium and molybdenum in buffalo calves:the levels of trace element in blood,urine and tissues

Ten male buffalo calves were randomly allotted into five groups of two each. Four groups were fed with cadmium, molybdenum, cadmium-molybdenum, and copper-cadmium-molybdenum respectively for 130 days to determine the elements' metabolic interactions in calves. These results indicated that cadmium and molybdenum could increase the accumulation of molybdenum and cadmium in liver and kidneys in buffalo calves, but copper could not. reduce to normal the levels of molybdenum and cadmium in liver and kidneys caused by cadmium-molybdenum. In addition, we found the copper concentrations in liver and kindeys was significantly greater in treatment calves than in controls.

Enterohaemolysin production and verotoxin genes in Escherichia coli strains isolated from neonatal calves in India

Objective:To screened all haemolytic strains of Escherichia coli(E.coli) for the presence of verotoxin genes and speculate the association between enterohaemolysin production and presence of verotoxin genes.Methods: A total 176 of E.coli strains of 64 serogroups isolated from neonatal calves were selected and screened for alpha -haemolysin and enterohaemolysin production on sheep blood agar and 5%washed sheep blood agar.Two types of haemolytic strains were further characterized by PCR for presence of Verotoxin gene(VT1 and VT2) and confirmed by verocell cytotoxicity assay.Results:Among 27 enterohaemolytic positive strains,19(70. 37%) strains were found positive for presence of verotoxins(VTs) gene and verocell cytotoxicity assay. Whereas 34 alpha-haemolysin strains were found negative for VTs.Eight strains of E.coli were found VTs negative but Ehx positive.Conclusion:The close association between enterohaemolysin production and presence of verotoxin genes makes it useful epidemiological marker for rapid screening of Verotoxic E.coli but this phenotypic marker for screening of verotoxigenic Escherichia coli(VTEC) alone may raise a question in animal.

Evaluation of forage-based weaning systems in spring-born cross-bred beef calves

Preconditioned calves have greater marketvalue per unit weight than normal-weaned calves. Development of a low cost forage-based preconditioning system allows producers to add value to their calf-crop. This study evaluated calf performance in three forage-based weaning systems;early-weaned calves were backgrounded in legume/grass forage plots and supplemented with commercial preconditioning feed (Treatment 1) or an on-farm corn-mix (Treatment 2). Control (Treatment 3) calves suckled for an additional 45 days. Supplements provided2.17 kgTDN/calf/ day. Weights were collected on days -30, 0 and 45 with respect to early weaning, from135 inyear 1 and 150 calves in each of the two subsequent years. Effects of treatment, age of dam, sex of calf and their interactions on calf weight gain were analyzed by analysis of covariance using GLM procedures of SAS. Marginal effects of treatment and feed cost were used to evaluate economic feasibility. Sensitivity analyses were evaluated for anticipated market fluctuations in feed costs and calf premiums. Data are reported as least squares means. Calf weight gains differed (P < 0.001) among treatments and averaged 1.16, 1.03 and1.04 kg/calf/day for commercial supplement, corn-mix and controls, respectively. Calves from 2-year-old cows gained less (P < 0.001) weight compared to those from cows 3 - 4 and ≥5 years of age (44.8, 48.9 and51.5 kg, respectively). Steers calves gained more (P < 0.001) weight compared to heifer calves (51.2 vs.45.7 kg, respectively). Net returns for corn mix were greater than those for commercial feed ($1.48 vs. $1.35/kg weight gain, respectively). Sensitivity analyses indicated that selection of preconditioning treatment to a large degree was less sensitive to significant changes in market conditions due to the large gap in marginal costs between the two treatments. In conclusion, forage-based weaning systems can be utilized to precondition calves providing an economical means for calf weight gain and profit potential as long as feed costs are held within reasonable limits.

Genotyping of Rotavirus in Neonatal Calves with Acute Gastroenteritis in Iraq

Globally, Rotavirus is the common major etiologic agents of diarrhea in infant, young children and neonatal calves. It is very important to early diagnose the disease for effective treatment. The objective of this study was to determine the prevalence, molecular characteristics, and the effect of rotavirus strains for severe gastroenteritis in neonatal calves in five Iraqi governorates (Al-Qadissiya, Babel, Kerbala, Missan, Wassit). A total of 125-stool specimens were examined, it have been collected from calves form the period between November 2015 to March 2016. The ages were ranging from 6 to 60 weeks. The specimens were examined using Chromatographic Immunoassay, enzyme-linked immunosorbent assay (ELISA) and Polymerase-chain reaction (PCR). Our results gave us 67 (53.6%) positive by chromatographic immunoassay, 45 (36%) positive by ELISA and 32 (25.6%) positive by PCR. Genotyping were analyzed by multiplex PCR. Genotype combination G1P[8] was (30%) followed by G1P[4] (20%), G3P[4] (20%), G2P[4] (10%), G2P[8] (10%) and G9P[4] (10%). Such information will not only aid in seeking advocacy for introducing rotavirus vaccine in national immunization program in Iraq, but will also help in the evaluation of the efficacy of these vaccines in relation to the rotavirus genotyping circulation.

Effect of Natural Feed Supplement on Methane Mitigation Potential and Performance in Holstein Bull Calves

Introduction of solid feeds in the ration of calves has been shown to increase rumen size and stimulate rumen fermentation. With the initiation of bacterial fermentation in the rumen, the intermediary metabolism moves from a glucose-based to a volatile fatty acid-based metabolism, which releases methane. MootralTM has been identified as a promising plant-derived feed supplement to reduce methane emission in dairy and beef cattle. Therefore, the present study aimed at quantifying and mitigating the methane emissions in calves until the slaughtering age of 28 weeks. The study consisted of 20 Holstein bull calves at a commercial farm, assigned randomly into 2 groups (control n = 10;treatment n = 10), for 2 weeks of adaptation and 8 weeks of sample collection. The calves were fed an increasing amount of milk replacer and ad libitum wheat straw. Mootral was fed once a day to the treatment calves. Methane was measured using GreenFeed units where concentrate feed was offered as bait. The calves were weighed at the start and every four weeks during the experiment. The calves in the treatment group had lower methane emissions (54 g/d) compared to the control group (70 g/d), a reduction of 22.8%. In contrast, carbon dioxide emission and dry matter intake did not differ significantly between the study groups. Moreover, no negative impact on the average daily weight gain and carcass weight was observed in Mootral fed calves. Although the methane emission (g/kg body weight) was lower in treatment than in the control group, the absolute difference between the groups narrowed with increasing age of the calves. The results suggest a need to increase the dose in line with the increased body weight and intake of the calves. In conclusion, Mootral effectively reduced methane in calves. Further trials to determine the optimal dose for calves are warranted, and as well studies to investigate if interventions (such as Mootral) applied at an earlier life cycle stage would have an impact on methane emissions at later stages of cattle’s life, would be of scientific interest.

Effect of Guazuma Leaves （Guazuma ulmifolia） Inclusion as Protein Source on Growing Calves

The present work was undertaken in a cattle ranch of the north of Puebla state, Mexico. The aim was to incorporate Guazuma leaves （Guazuma ulmifolia） in the diet of growing calves and evaluate its effect on weight gain. Twenty-four Cebu × Swiss calves （approximately live weight 250 kg） were used during all the experimental period （64 d）. They were assigned to a completely randomized design under two treatments （n = 12 for each treatment）： control （T1） consisted of commercial feed based on 15% crude protein （CP） ＋ cut Taiwan grass and the treatment （T2） consisted of a formulated diet containing 14.7% CP including Guazuma. The composition of the formulated diet consisted of： Guazuma （60%）, rolled corn （12%）, ground sorghum （9%）, oats in grain （7%）, wheat bran （9%） and vitamins and minerals. The feed was offered twice a day at a rate of 3% of live weight for 64 d. The mean daily gain for T1 and T2 was 1.15 g/animal and 1.52 g/animal, respectively （p 〈 0.05）. Results indicate that Guazuma-based supplements resulted in greater productive yield in growing calves.

Pharmacokinetics and Efficacy of Tilmicosin in the Treatment of <i>Pasteurella haemolytica</i>Bronchopneumonia in Calves

Tilmicosin was administered intravenously and subcutaneously at a dose rate of 10 mg/kg bwt to determine its concentration in blood and bronchial secretion as well as its kinetic behavior in healthy and Pasteurella haemolytica type A1-infected calves. Sever acute bronchopneumonia was induced in 10 calves by inoculating them intra-tracheally with P. haemolytica type A1. The calves were treated with tilmicosin;5 of these received the drug intravenously and the other 5 were injected subcutaneously. After a slow intravenous injection, the serum concentration-time curve indicated a two compartment open model with a mean elimination half-lives (t1/2bs) of 22.09 and 22.14 hours before and after infection, respectively. The mean residence time (MRT) corrected for a bolus injection was 2.25 and 2.20 hours and the mean MRTinf was 25.27 and 25.46 hours in healthy and P. haemolytica-infected calves, respectively. After subcutaneous injection, the drug was eliminated more slowly (before and after infection) from serum and bronchial secretions, with t1/2bs of (24.60 and 25.85 hours) and (33.74 and 31.78 hours), respectively. The apparent volume of distribution (Vd(area)) of tilmicosin was more than 1 litre·kg-1. The peak serum and bronchial secretions of tilmicosin concentration were (1.33 and 1.36 mg·ml-1) and (1.40 and 1.70 mg·ml-1) attained at (7.21 and 7.15 hours) and 7.11 and 7.10 hours) after subcutaneous injection, respectively. Tilmicosin was good secreted into bronchial secretions having AUCbronchial secretion/ AUCserum ratio of approximately 1:1.24 and 1:1.22 in healthy and P. haemolytica-