Effects of various steroid milieus or physiological states on sexual behavior of Holstein cows.

Two experiments were conducted to determine how steroid milieus and pregnancy affect sexual behavior. Experiment 1 was arranged as a Latin square with five ovariectomized cows and five steroid milieus: no steroid (N); progesterone (P4); estradiol benzoate (EB); P4 + EB; and P4 followed by EB (P4:EB). Progesterone was administered via pessary (2 g of P4) for 5 d and EB was injected (1 mg i.m.) on the day before a test day. On a test day, cows were exposed for four 30-min periods, twice each with a tied or a loose estrual test cow (prepared using P4:EB). Sexual behaviors recorded were attempted mounts, successful mounts, front mounts, stands, head butts, chin rests, and vulvar sniffs. Cows exhibited more (P less than .05) sexual behavior during periods with the loose estrual test cow than with the tied estrual test cow. Cows receiving P4 alone ranked lowest among treatments for each behavior, whereas cows receiving EB or P4:EB ranked highest or second-highest. Progesterone prevented stands in cows given P4 + EB, but these cows displayed mounting behaviors similar to those of cows given EB and P4:EB. Cows given P4 + EB were similar to those given N for most behaviors. In Exp. 2, 118 intact, lactating cows were observed in groups of four or five for mounting of estrual test cows during 24, 30-min observation periods on 8 d over 2 yr. The design was an incomplete block with physiological state, parity, estradiol, progesterone, and a calculated estrogen:progesterone ratio included in the model. Each block included one or two cows at 23 +/- .8 d after insemination, divided retrospectively into one pregnant and two non-pregnant groups (low [less than 1 ng/mL] vs high progesterone), and other cows at 89 +/- 1.0, 152 +/- 1.2, and 234 +/- 1.7 d of gestation (six physiological groups). Most cows were observed once, but 27 cows were included twice during 2 yr. Only 60% of the 118 cows made attempted or successful mounts even though estrual test cows were always receptive. Physiological state was not associated with amount of mounting because very active (greater than or equal to five attempts) and inactive cows were represented in all physiological groups. The estrogen:progesterone ratio on test day accounted for small, but significant, variation in mounting behavior. For cows observed on two different days, correlations between successive observations were .46 for attempted mounts, .78 for successful mounts, and .71 for total mounts.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of sequential or group exposure to unrestrained estrual females on expression of sexual behavior in sexually experienced beef bulls

We tested the hypothesis that expression of sexual behavior in bulls is affected by the manner in which they are exposed to unrestrained, sexually receptive females. Twelve Angus bulls were used in a crossover design involving two treatments, each tested four times for a total of eight tests for each bull. Sexual interactions were quantified for each of four, 30-min periods under the following treatments: 1) exposure to each of four estrual females in sequence (SEQ); or 2) exposure to four estrual females as a group (GRP). Bulls were blocked into three testing groups, the order of which was stratified across eight test days. The order in which bulls were tested on a particular day had no effect on bulls' expression of mount interactions, or flehmen responses, suggesting that each group of bulls had similar sexual motivation at the beginning of each test. However, the bull testing order x treatment x time interaction influenced mounting interval (P = 0.08), copulation frequency (P <0.05), and copulation success ratio (P <0.05). When bulls were in GRP and tested first on test days, more (P <0.05) copulations were distributed to the first three females encountered compared with either the fourth female (P <0.05) or to each of the other females in SEQ (P <0.05). During later tests, other bulls in GRP were not able to copulate as frequently (P <0.05) with each female, displayed lower (P <0.05) copulation success ratios, and were allowed copulations by fewer (P <0.05) females during each 30-min test. When bulls were in SEQ, they displayed similar numbers of copulations regardless of the order in which they were tested, and had stable mounting intervals; however, copulation success ratio decreased (P <0.05) more rapidly during subsequent tests. Flehmen responses were initially displayed more frequently (P <0.05) when bulls were in GRP, but this effect diminished during subsequent 30-min tests. In conclusion, exposure of bulls to GRP induced greater sexual responsiveness than SEQ; however, this effect was due to enhanced sexual activity during the early stages of sexual encounters and with females that were not recently mated. Interestingly, bulls seem to repeatedly copulate with each individual female until, apparently, female sexual receptivity became attenuated. Thereafter, recently mated females allowed fewer episodes of repeated copulations, but they did not completely cease copulating with novel bulls.     

Immunohistochemical Expression of Nitric Oxide Synthase Enzymes (iNOS,eNOS, nNOS) in the Estrual and Luteal Phases of the Sexual Cycle in the Cow Oviduct

This study was aimed to determine staining intensity, cellular localization and distribution of the nitric oxide synthase (NOS) enzymes during the sexual cycle in the cow oviduct. Oviduct samples belonging to 20 cows, 10 of which were in the estrual phase and 10 in the luteal phase of the sexual cycle, were examined by an immunohistochemical procedure to determine the presence of the NOS enzymes. In the epithelial cells of the isthmus, endothelial NOS (eNOS) expression showed a strong positive reaction during the estrual phase and a weak positive reaction during the luteal phase in the endothelium and smooth muscle of the blood vessels found in the serosa and lamina propria. eNOS expression was not observed in the epithelium of either the ampulla or the fimbria in the two particular phases of the sexual cycle. The eNOS reactions observed in the blood vessel wall in these regions were stronger during the estrual phase. eNOS activity was not observed in the tunica muscularis in any of the regions of the oviduct. During the estrual phase, it was observed that inducible NOS expression showed a stronger positive reaction in the epithelium and muscle layer of the isthmus and ampulla and in the epithelium of the fimbria, compared to the luteal phase. Neuronal NOS immunoreactivity was observed in the epithelial cells of all oviduct regions and in the muscle layer of the isthmus and ampulla and did not display any significant difference between the estrual and luteal phases.     

Effect of treatment with an internal teat sealant at drying-off in cows wintered on forage crops in New Zealand on clinical mastitis and somatic cell counts

AIMS: To determine the impact of treatment with internal teat sealant (ITS) compared to no treatment at drying-off on the incidence of clinical mastitis (CM) during the dry period and 84 days after calving, and the prevalence of cows with somatic cell counts (SCC) ≥200,000?cells/mL at the first lactation herd test, for cows wintered on forage crops.

METHODS: In four dairy herds in the South Island of New Zealand, cows with no history of CM or individual SCC >100,000?cells/mL during the 2015–16 season were randomly assigned to treatment with ITS in each quarter (ITS group) at drying-off or no treatment (Control group). Cows were otherwise treated similarly, wintered on forage crops and transferred to pasture for calving and lactation. Cows were monitored over the dry period and for 84 days after calving, and any case of CM recorded. Individual SCC were recorded at the first herd test after calving.

RESULTS: Between drying-off and 84 days after calving 36/470 (7.7%) cows in the ITS groups and 73/442 (16.5%) cows in the Control group were diagnosed with CM (RR=0.46; 95% CI=0.26–0.73). The final multivariable logistic regression model included an interaction between treatment group and length of dry period. For a Friesian/Jersey cow, aged 4–8 years, with a dry period of 30–80 days, dried off without ITS, the probability of CM in the study period was 0.12 (95% CI=0.09–0.16), and for such a cow treated with ITS the probability was 0.07 (95% CI=0.05–0.10). For an equivalent cow, with a dry period of 81–140 days, which was untreated, the probability was 0.21 (95% CI=0.14–0.29), and for such a cow treated with ITS it was 0.05 (95% CI=0.02–0.11). At the first herd test after calving 77/383 (20.1%) cows in the Control group and 57/425 (13.4%) cows in the ITS group had SCC ≥200,000?cells/mL (RR=1.51; 95% CI=1.10–2.06).

CONCLUSIONS AND CLINICAL RELEVANCE: For these farms, treatment of cows with no history of elevated SCC or CM with ITS at drying-off halved the incidence of CM between drying-off and 84 days after calving, and reduced by 33% the proportion of cows with SCC≥200,000 at the first herd test after calving, compared with untreated cows. Treatment with ITS reduced the risk of CM proportionally more for cows with a dry period of 81–140 days than for cows with a shorter dry period.     

Effect of pre-calving zeolite, magnesium and phosphorus supplementation on periparturient serum mineral concentrations

The objective of this study was to test whether supplementing dry cow rations with phosphorus (P) and magnesium (Mg) would interfere with the beneficial effect of zeolite supplementation on the periparturient blood calcium (Ca) concentration in dairy cattle. Three groups (A-C) of 10 Danish Jersey cows were each given the following daily supplements from 2 weeks before the expected date of calving until actual calving: group A: zeolite, monoammonium phosphate, standard dry cow mineral and vitamin mix, containing 61g magnesium phosphate; group B: zeolite, standard mineral and vitamin mix without the magnesium phosphate and group C: standard mineral and vitamin mix, monoammonium phosphate. All cows in group B had an apparently less variable serum calcium concentration around calving with no cases of milk fever and no subclinical hypocalcaemia or hypomagnesaemia recorded. In contrast, a parturient drop in blood Ca was seen in group A as well as group C. In group A, one cow was hypocalcaemic at calving, and developed milk fever. In group C, 12 blood samples, representing six cows, were hypocalcaemic, and three of these cows were treated for milk fever. All groups remained normomagnesaemic and there were no significant differences in blood Mg across groups. In conclusion, the combined P and Mg supplementation in addition to zeolite supplementation did not increase the serum Mg level (forage Mg 16.9g/day; 0.21% of DM). Combined P and Mg supplementation reduced the zeolite-induced hypophosphataemia but also reduced the stabilising effect of zeolite on parturient serum Ca.     

Development of a Staphylococcus aureus vaccine against mastitis in dairy cows. I. Challenge trials

A vaccine composed of three field isolates of Staphylococcus aureus (S. aureus) derived from cases of mastitis in cows was developed. The vaccine was administered to nine uninfected cows while 10 other cows were used as controls. All cows were challenged with a highly virulent S. aureus strain administered into two quarters of each cow. Quarters were tested for clinical signs, secretion of S. aureus, and somatic cell count (SCC). No systemic effects were observed in any of the cows, vaccinated or control. Vaccinated cows had 70% protection from infection compared with fewer than 10% in the controls. Moreover, all quarters challenged in the vaccinated cows, regardless of whether they were successfully infected or not with S. aureus, exhibited very mild inflammatory reactions, identified by their low SCCs (<100,000).     

Effects of long-term feeding of a diet supplemented with clinoptilolite to dairy cows on the incidence of ketosis, milk yield and liver function

Fifty-two clinically healthy Holstein cows were randomly assigned to one of three groups according to their age and parity. The first group (A) consisted of 17 cows that were fed a concentrate ration supplemented with 1.25 per cent clinoptilolite, the second group (B) consisted of 17 cows fed a ration supplemented with 2.5 per cent clinoptilolite, and the third group (C) consisted of 18 cows, which were fed the basal ration containing no clinoptilolite. The rations were fed from four weeks before the cows' expected parturition dates until the beginning of the next dry period. Blood samples were collected from each animal at the start of the experiment, on the day of calving and then monthly, and analysed for serum glucose, ketone bodies, liver enzymes, blood urea nitrogen (BUN) and total proteins. The milk yield of each cow was recorded monthly. The cows in group B had significantly fewer cases of clinical ketosis during the first month after calving and a higher total milk yield. Feeding the cows with clinoptilolite for a long period had no apparent adverse effects on their liver function, and did not significantly affect the concentrations of glucose, ketone bodies, BUN and total proteins in their serum.     

Nursing enhances the negative effect of estrogen on LH release in the cow

Twenty-three crossbred beef cows between 4 and 5 yr of age were assigned at random to one of six treatments: (1) ovariectomized 4 d postpartum (OVX) with early weaning of calves 21 d postpartum (OVX-EW; n = 4), (2) OVX-EW and 17 beta-estradiol implants (OVX-E2-EW; n = 4), (3) OVX and normal nursing by calves throughout the experiment (OVX-NN; n = 3), (4) OVX-NN and 17 beta-estradiol implants (OVX-E2-NN; n = 4), (5) intact cows and early weaning of calves 21 d postpartum (EW), (6) intact cows and normal nursed (NN). Blood was collected at 15-min intervals over a 4-h period once weekly during the 12-wk postpartum period in the OVX cows. Early weaned intact cows exhibited estrus 23 d sooner (P less than .05) than normally nursed cows. A hormone level for each cow at each week was determined from the mean of the 17 samples collected over the 4 h period each week. There were no significant changes due to E2 treatment, for concentrations of LH, FSH or number of pulses during wk 1 through 3. However, during wk 4 through 12 the linear and quadratic contrasts of wk X estrogen X nursing were significant for serum LH, indicating there was no difference between the treatments for EW and NN without E2 but there was a large difference in the presence of E2. During nursing E2 suppressed serum LH below that of nonestrogen-treated cows while after weaning E2 stimulated LH release above that of nonestrogen-treated cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of novel females and stage of the estrous cycle on sexual behavior in mature beef bulls

The objective of this experiment was to determine the effects of unrestrained females on sexual behavior of bulls. Twelve Angus bulls were used in three Latin square replicates where sexual interactions between one bull and one female were quantified for each of four 60-min tests (T1, T2, T3, and T4, respectively). All bulls received the following treatments: 1) exposure to four estrual females in sequence (A-B-C-D); 2) exposure to two estrual females in alternating sequence (E-F-E-F); 3) exposure repeatedly to one estrual female (G-G-G-G); and 4) exposure repeatedly to one diestrous female (CON). During T1, mount interactions, mounts with intromission and mounting intervals were similar when bulls were in A-B-C-D, E-F-E-F, or G-G-G-G. Fewer mount interactions, no mounts with intromission, and increased mounting intervals (P < 0.05) occurred in CON. During T2, there were more mount interactions, more mounts with intromission, and decreased mounting intervals (P < 0.05) when bulls were in A-B-C-D or E-F-E-F compared with when they were in G-G-G-G or CON. More mount interactions (P < 0.05) occurred in G-G-G-G compared with CON, but mounts with intromission and mounting intervals did not differ. During T3, more mount interactions (P < 0.05) occurred in G-G-G-G than in CON; otherwise, sexual behaviors were similar among treatments. Mounting intervals during T3 were similar among A-B-C-D, E-F-E-F, and G-G-G-G, but were all decreased (P < 0.05) compared with CON. During T4, more mount interactions, more mounts with intromission, and decreased mounting intervals (P < 0.05) occurred when bulls were in A-B-C-D compared with other treatments. Mount interactions were similar when bulls were in E-F-E-F, G-G-G-G, or CON; however, more (P < 0.05) mounts with intromission occurred when bulls were in E-F-E-F compared with G-G-G-G or CON. Mounting intervals during T4 were decreased (P < 0.05) in E-F-E-F compared with the CON treatment, whereas in G-G-G-G, they were intermediate. Mounts without intromission were not affected by female novelty or receptivity, but novel females induced more flehmen responses. In conclusion, novel, females, overall, enhanced sexual activity of bulls; however, bull sexual responses diminished after 2 h, even when a novel female was presented. Estrual females that were repeatedly paired with bulls displayed diminished sexual receptivity, but if mated females were rested for 60 min, they allowed further copulation from familiar bulls that were not sexually sated.     

Effects of a rubber-slatted flooring system on cleanliness and foot health in tied dairy cows

Effects on animal cleanliness and foot health of a new rubber-slat system for tied dairy cows, with the ability to drain faeces and urine, were studied in a 2-year controlled quasi-randomised trial in a Swedish university herd. Swedish Red and White cows were kept tied in 42 traditional long-stalls with rubber mats. In total, 82 cows were observed. In 21 stalls, the rearmost 0.74m of the solid stall floor was replaced with nine rubber-coated 53mm wide slats, divided by 29mm slots. The cleanliness was assessed subjectively weekly (year 1) or bi-weekly (year 2) by observations of the hind part of the body. Claw measurements and foot health in hind feet were assessed in connection with hoof trimmings at the beginning, middle and end of the housing period. The foot-health recordings were blinded to flooring. For the analysis of both cleanliness (1781 records, 73 cows) and foot health (240 records, 79 cows), logistic regression was applied, using marginal models and cow observations as repeated measures within each year. The risk of getting dirty on the rubber-slatted floor was significantly lower (odds ratio 0.12 for hind feet when short stall dividers were used, 0.39 for hind legs and 0.38 for thighs and udder), comparing with the solid stall floor. The prevalence of foot diseases in hind feet at trimming was significantly lower on the rubber slats (odds ratio 0.23 for dermatitis, 0.09 for heel horn erosion, and 0.34 for sole ulcer or sole or white line haemorrhage).     

酶菌复合制剂对奶牛生产性能和体细胞数的影响

本试验旨在研究酶菌复合制剂对奶牛生产性能和体细胞数的影响。选取年龄、胎次、泌乳天数及生理性状相近的荷斯坦奶牛240头,随机为成4组,每组6个重复,每个重复10头牛。对照组饲喂基础日粮,试验Ⅰ、Ⅱ和Ⅲ组分别在基础日粮中添加0.5、1.0和1.5 kg/t的酶菌复合制剂,预试期10 d,正试期40 d,分别于试验第10、20、30、40天采集牛粪便,利用粪便分析筛对牛粪便组成进行分析。分别在试验第1、20、40天采集乳样,采用乳汁分析仪测定各组乳样中乳脂率、乳蛋白率、非脂固形物和奶中体细胞数（SCC）,试验期间记录每头牛平均日产奶量（ADMY）及平均日采食量（ADFI）。试验结果表明,添加酶菌复合制剂能够显著增加奶牛平均日产奶量（P<0.05）,提高牛乳中乳蛋白和乳脂肪含量（P<0.05）,降低体细胞数（P<0.05）,改善粪便结构。综合试验结果,酶菌复合制剂应用于奶牛养殖的最优添加量为1.0 kg/t,可以提高奶牛产奶量,降低牛体细胞数。     

Application of the direct leukocyte-migration agarose test in cattle from a Mycobacterium paratuberculosis-infected herd

Using johnin as the specific antigen, the direct leukocyte-migration agarose test was applied to 10 cows from a Mycobacterium paratuberculosis-infected herd. Nine of the cows did not have signs of paratuberculosis; 1 cow was clinically affected. The cows were slaughtered and, on the basis of histopathologic and cultural examinations of the intestines, were classified as infected or noninfected. Six of the healthy cows from which the bacterium was not isolated and the clinically affected cow reacted with migration indices lower than those of 3 healthy animals that were found to harbor the bacterium. It is suggested that the long incubation period of paratuberculosis could to some extent be due to immunologic tolerance.     

不同降温处理工艺对北京地区奶牛夏季生产性能和生理指标的影响

试验旨在探讨不同降温处理工艺对北京地区泌乳牛夏季生产性能和生理指标的影响。采用单因子试验设计,将30头泌乳牛随机分为A、B、C三组,每组10头,采取不同降温工艺处理,A为对照组,B为风机降温组,C为智能喷淋降温组。试验期为14d,期间提供相同日粮,自由饮水,对夏季牛舍环境指标、奶牛生理指标、行为参数和产奶性能进行持续测定。结果表明:在半开放牛舍中,相比于风扇降温模式,智能喷淋降温模式能有效降低处理过程中温湿指数(P<0.05)、奶牛体表温度(P<0.05)、呼吸频率(P<0.05);增加高温环境下奶牛躺卧时间(P<0.05),缩短站立时间(P<0.05);有效缓解高温导致的日采食量下降和产奶损失,提升夏季牛奶乳脂率(P<0.05);降低牛乳中血清蛋白含量(P<0.05)和体细胞数(P<0.05)。说明在北京地区半开放式养殖模式下,智能喷淋降温能更有效缓解夏季热应激,调节奶牛生理状况和行为活动,提升奶牛夏季生产性能。     

Effects of gonadotrophin releasing hormone on reproductive performance of dairy cows with retained placenta.

The effects of gonadotrophin releasing hormone (GnRH) on the reproductive performance of dairy cows with retained placenta were studied. Three hundred and seventy-eight cows diagnosed as having retained placenta received intramuscular injections of either 2 mL sterile water or 200 micrograms of GnRH in 2 mL sterile water between day 8 and day 14 postpartum. Rectal palpation was performed at the time of treatment and ten to 20 days after treatment in order to determine the rate of uterine involution. Thereafter, monthly rectal examinations were carried out until insemination. Pregnancy diagnosis was made by rectal palpation at 40 days or more after breeding. Using the entire experimental population, there were no significant differences between GnRH-treated and control cows for the rate of uterine involution, the occurrence of reproductive problems, the interval from parturition to first observed estrus, the interval from parturition to first insemination, the interval from parturition to conception, the number of services per conception, the total number of services per cow regardless of conception and the incidence of culling for infertility. When the data for herds in which breeding began earlier in the postpartum period (herds having a mean less than or equal to 80 days from parturition to first service for retained placenta cows) were considered, the GnRH treatment resulted in a significantly shorter (p less than or equal to 0.01) calving to conception interval as compared to control cows. Also, there was a significant reduction (p less than or equal to 0.05) in the total number of services per cow regardless of conception and a significant reduction in the interval from parturition to first service.(ABSTRACT TRUNCATED AT 250 WORDS)     

Herd-level Coxiella burnetii seroprevalence was not associated with herd-level breeding performance in Czech dairy herds

Q fever was studied on a large agricultural farm in northern Moravia, Czech Republic. Antibodies to Coxiella burnetii were ascertained by a complement fixation test. Titre of 8 or higher was considered as positive. The seroprevalences in cows (each cow was examined only once immediately after drying-off during a one-year period) from 14 different herds was between 4 to 19%. No significant correlation between seroprevalence levels and fertility characteristics in the cow herds was found. Of a total of 17 samples of milk from 17 randomly-selected cows with antibody titres of 8 to 32, one strain of Coxiella burnetii was isolated. In heifers (n = 339) and beef bulls (n = 210) no antibodies to C. burnetii were found. In cattle from the farm investigated, latent Q fever did not represent any health problem.     

Efficacy of intramuscular treatment of beef cows with oxytetracycline to reduce mastitis and to increase calf growth

Spring-calving multiparous Angus x Hereford cows were used to determine the efficacy of intramuscular treatment with oxytetracycline to reduce the incidence of mastitis-causing bacteria, decrease milk somatic cell counts (SCC), and increase calf growth. During 2 yr, milk samples were collected from each quarter from a total of 319 cows at 8 to 14 d after calving and at weaning, to determine the presence of bacteria and SCC. A California mastitis test (CMT) was performed on milk from each quarter of each cow at the initial sample collection. Cows with a CMT score of 1, 2, or 3 in at least one quarter, were randomly assigned to receive either an intramuscular injection of oxytetracycline (n = 63) or the control vehicle (n = 60), and cows with a CMT score of 0 or trace in all four quarters were not treated (n = 196). Calf weights were determined at birth, early lactation, and weaning. The number of somatic cells in milk and the percentage of quarters that were infected increased as CMT score increased (P < 0.01). The presence of mastitis-causing bacteria at calving increased (P < 0.05) the incidence of infection at weaning. The presence of mastitis-causing bacteria at weaning was associated with increased SCC for quarters and average SCC for cows (P < 0.01). Average SCC per cow at weaning increased (P < 0.05) as the number of infected quarters per cow increased. Treatment did not alter (P > 0.10) the percentage of cows or quarters infected with mastitis-causing bacteria or SCC of cows or quarters at weaning. Average SCC per cow was negatively correlated (P < 0.05) with calf weights at early lactation, but not with weaning weights of calves. Treatment did not influence (P > 0.10) calf weights at early lactation or at weaning. Cows with one or more dry quarters after calving had calves that weighed less at early lactation and weaning than cows with four functional quarters (P < 0.01). Intramuscular oxytetracycline treatment of beef cows that had CMT scores of 1 or greater after calving did not reduce intramammary infection rates or increase calf weights at weaning.     

全株玉米青贮、谷草和羊草组合全混合日粮饲喂干奶前期奶牛对其围产期生产性能和血液生化及免疫指标的影响

在研究不同比例全株玉米青贮、谷草和羊草组合日粮饲喂干奶前期奶牛对其围产期生产性能和血液生化及免疫指标的影响。选择健康、体况一致的干奶前期荷斯坦奶牛45头,根据体重、胎次及预产期接近(P>0.05)的原则将奶牛随机分为试验A、B和C组,每组15头。分别以精料、全株玉米青贮、谷草和羊草16∶24∶30∶30(A组)、16∶24∶45∶15(B组)和16∶24∶60∶0(C组)比例配合日粮饲喂。产前2周将3组试验牛转入围产牛群,3个试验组开始饲喂场内同一围产前期和新产牛日粮。试验期88 d。结果表明:1)与C组相比,B组在产后1、2和3周的干物质采食量分别提高10.46%(P<0.05)、7.79%(P<0.05)和5.65%(P<0.05)。除产后1周外,产后2、3周B组的奶牛体况评分分别比C组高6.60%(P<0.05)和9.06%(P<0.05)。2)各试验组的犊牛初生重差异不显著(P>0.05)。试验A、B组初乳免疫球蛋白G(IgG)含量分别比C组提高10.82%(P<0.01)和18.07%(P<0.01)。3)与C组相比,B组产后21 d产奶量提高9.00%(P<0.05),乳非脂固形物率提高2.83%(P<0.05),乳蛋白率提高10.59%(P<0.05),乳糖率提高5.64%(P<0.05)。各试验组间乳脂率和尿素氮无显著差异(P>0.05)。4)分娩当天和产后21 d,B组的血清甘油三酯含量显著低于A和C组(P<0.05),B组的血糖含量显著高于A和C组(P<0.05), B组的血清尿素氮和胰岛素显著低于C组(P<0.05),B组的胰岛素样生长因子I(IGF-I)和总蛋白显著高于C组(P<0.05);在产前7 d和分娩当天,B组的血清免疫球蛋白A(IgA)、免疫球蛋白B(IgM)和IgG显著高于C组(P<0.05);在产后21 d,B组的血清IgM和IgG含量显著高于C组(P<0.05);产前7 d和分娩当天,B组瘦素显著高于C组,而B组的血清非酯化脂肪酸(NEFA)含量显著低于C组(P<0.05);在产前7 d、分娩当天和产后21 d,B组的胆固醇均显著低于C组(P<0.05),B组的血清白蛋白含量显著高于C组,B组谷草转氨酶(AST)和谷丙转氨酶(ALT)也显著低于C组(P<0.05)。各试验组间β-羟丁酸无显著差异(P>0.05)。综合分析,干奶前期饲粮组成和养分水平可影响围产期奶牛的机体代谢和生产性能。在本试验条件下,干奶前期奶牛日粮中精料、全株玉米青贮、谷草和羊草的适宜比例为16∶24∶45∶15。     

Epidemiologic aspects of bovine anaplasmosis in semiarid range conditions of south central Idaho

The prevalance of Anaplasma marginale-infected cows, as determined by use of the modified rapid card agglutination (MRCA) test, was measured during a 4-year period (1980-1983). The prevalence of A marginale-infected cows, defined as positive reactors on the MRCA test, remained constant (31%-37%). The apparent incidence of A marginale transmission to susceptible cows was approximately 7% from 1980 to 1981, 8% from 1981 to 1982, and no transmission from 1982 to 1983. The occasional MRCA-positive cow became negative on the MRCA test, and 1 cow was determined to be free of A marginale infection by subinoculation of 100 ml of the cow's blood into a susceptible, splenectomized calf. Dermacentor andersoni, a known vector of A marginale, was often found on the cattle and in their environment. However, A marginale was not transmitted to susceptible, splenectomized calves, using collected ticks. Of 56 calves born to MRCA-positive cows, 82% were MRCA-positive within the first 3 months of life. These calves converted to MRCA-negative status and were determined to be free of A marginale infection by subinoculation of their blood into susceptible, splenectomized calves, indicating the passive transfer of colostral antibodies.     

Maternal performance of Hereford, Brangus, and reciprocal crossbred cows under semidesert conditions.

Maternal performance of 134 Hereford (H), Brangus (B), and reciprocal crossbred (H x B and B x H) cows from 2 to 7 yr of age was evaluated under semidesert conditions in this study. Calves produced by 2- and 3-yr-old cows were sired by Brangus and Hereford bulls. Calves produced by 4- to 7-yr-old cows were sired by Charolais bulls. Breed of sire and breed of dam of cow affected kilograms of weaning weight, 205-d weight, weaning weight as a percentage of cow weight, and 205-d weight as a percentage of cow weight produced annually. Brangus (either as sire or dam of cow) was superior to Hereford in all cases. Observed maternal heterosis on 2- to 3-yr-old cows was 23.0, 20.1, 30.0, 29.1, 23.9, and 23.0% for calf birth date, weaning percentage, weaning weight per year, 205-d weight per year, weaning weight as a percentage of cow weight per year, and 205-d weight as a percentage of cow weight per year, respectively (P less than .01). Observed maternal heterosis from mature cows was 19.8, 12.8, 21.0, 18.7, 17.4, and 15.4% for calf birth date, weaning percentage, weaning weight per year, 205-d weight per year, weaning weight as a percentage of cow weight per year, and 205-d weight as a percentage of cow weight per year, respectively (P less than .01). Results indicate large heterotic effects on annual cow productivity and an adaptive advantage for cows with Brangus sires and(or) dams under semidesert conditions.     

Congenital Neospora caninum infection in dairy cattle and associated calfhood mortality.

A prospective cohort study was undertaken on two central California dairies, A and B, to estimate prevalence of congenital infection with Neospora caninum, to characterize temporal variation in prevalence, to determine if occurrence of congenital infection was associated with specific dam and calf attributes, and to estimate the effect of congenital infection on calfhood mortality. Of the 405 calves enrolled over a period of 2 1/2 y on dairy A and dairy B, 30.6% (85/278) and 53.5% (68/127), respectively, were seropositive precolostrally to N. caninum, as determined by an ELISA test. Adult cow seroprevalence at calving was 36.0% (82/228) for dairy A, and 57.9% (33/57) for dairy B. No evidence was found for a significant increasing or decreasing trend in adult and precolostral seroprevalence through the study period (P > or = 0.26). For both herds combined, 81% of seropositive cows (93/115) and 5% of seronegative cows (8/170) had congenitally infected calves. Seroprevalence did not increase with cow age on either dairy (P > or = 0.47). The probability of a calf being congenitally infected was not associated with dam age, dam lactation number, dam history of abortion, calf gender, or length of gestation (P > or = 0.11). High dam ELISA values at calving were significantly associated (P < or = 0.001) with an increased probability of congenital infection in her calf. Results of survival analyses of female calves available for follow-up indicated a consistently greater survivorship to 90 d in congenitally infected calves than in noninfected calves on both dairies, which was significant for dairy A (P = 0.07, n = 186) but not for dairy B (P = 0.69, n = 72), thus indicating that congenital infection does not necessarily have a detrimental effect on calf health. The findings of a similar magnitude in congenital infection rate and adult cow prevalence, the lack of increasing seroprevalence with cow age, the lack of an effect of dam age on precolostral seropositivity, and the constant seroprevalences during the study period, suggest that, in the two dairies studied, congenital transmission constituted a substantial amount of infection and was likely the major mode of transmission of N. caninum.