Dairy Beef Research Articles

Prevalence of Asymptomatic Carriers of Shiga Toxin-Producing Escherichia Coli (STEC) in Dairy Cattle Farms in the Governorate of Blida (Algeria)

Abstract We investigated whether dairy beef cattle raised in Algeria are Shiga toxin-producing Escherichia coli (STEC) carriers. Stx1 and stx2 genes were analysed in DNA isolated from 200 faecal samples collected from adult dairy cows from 27 randomly selected farms in Blida, North Algeria, after amplification by PCR. Samples from 61 (30.5%) animals out of the 200 were positive and were located in 18 farms with a prevalence of 66.7%. Interestingly, no sample from any cow was positive for only the stx2 gene, while in contrast, samples from 51 cows were positive for the stx1 gene alone (83.6%) and those from 10 other cows were positive for both stx1 and stx2 genes (16.4%). It should be noted that the faecal samples infected with pathogens carrying the two genes originated from 4 out of the 18 farms that were found to be positive, with a rate of 22.2%.

Coxiella burnetii seroprevalence and associated risk factors in dairy and mixed cattle farms from Ecuador

Q fever is a zoonotic disease caused by Coxiella burnetii, a bacterial agent for which ruminants are the main reservoir. An extensive cross-sectional study to determine the seroprevalence of and associated risk factors for Q fever was performed in dairy and mixed (dairy–beef) cattle herds in Ecuador. A total of 2668 serum samples from 386 herds were analyzed using an ELISA. In addition, a questionnaire with 57 variables related to management, feeding, facilities, biosecurity and animal health was completed for every cattle farm. A Generalized Estimating Equations model was used to determine the factors associated with C. burnetii seropositivity.The true prevalence of C. burnetii seropositivity in dairy and mixed cattle from Ecuador reached 12.6% (CI95%: 11.3–13.9%). The herd prevalence was 46.9% (181/386) (CI95%: 41.9–51.9%), and the within herd prevalence ranged between 8% and 100% (mean: 25.0%; Q1: 12.5%, Q2: 25.0%, Q3: 37.5%). Four factors were included in the GEE model for C. burnetii seropositivity: age of the cattle (OR: 1.01; CI95%: 1.006–1.014), feeding of calves with milk replacers (OR: 1.94; CI95%: 1.1–3.3), bovine respiratory syncytial virus seropositivity (OR: 1.54; CI95%: 1.1–2.3), and disinfection of the umbilical cord (OR: 0.60; CI95%: 0.4–0.9).

Ethiopian beef carcass characteristics

This study was conducted to evaluate beef carcass characteristics of cattle slaughtered at local abattoirs in Ethiopia. About 10% of carcasses (3080) were collected from Adama, Hawassa, Mekelle and Kombolcha abattoirs between August 2013 and January 2014. The results of the study showed that 98.56% of cattle slaughtered were indigenous cattle while 1.44% was Holstein Frisian. The average carcass weight of indigenous cattle was 135.90 + 0.69 kg. Carcass weight was significantly (p<0.001) different between abattoirs, season, conformation grades, fat grades and categories of cattle. Conformation grade 1, 2 and 3 accounted for 30, 34.29 and 35.71% of carcasses evaluated, respectively. Fat grade1, 2 and 3 accounted for 67.5, 23.57 and 8.93% of carcasses evaluated, respectively. Intact bulls, castrated bulls, growing bulls and cows accounted for 26.07, 64.64, 3.95 and 5.36% cattle slaughtered, respectively. Higher carcass weight, higher proportion of superior conformation and fat grade were observed in the wet season compared to the dry season. Inferior conformation and fat grades were relatively higher for cows (80 and 84.42%) and castrated bulls (37.57 and 67.96%) compared to other categories of cattle. From the study it was concluded that the use of dairy beef was very low in Ethiopia. The proportion of carcass with little /no fat cover (fat grade 1) was very high. The relatively better carcasses weight, conformation and fat grades in the wet season compared to the dry season indicates the opportunities to improve carcass weight and quality through better feeding management.

Modern Intensive Dairy Beef Production Systems in Russia

The objective of this study was to determine the biological and economic efficiency of growing-finishing young dairy bulls slaughtered at different live weights under current consumer´s requirements and market conditions. Experiment was conducted with bull calves of Black and White breed with high level (>85%) Holstein blood (n=60). All animals were indoor housed and fed on diets consisting of forage (55 percent on dry matter basis) and concentrate (45 percent) with flat daily live weight gains 900-1000g. The overall findings for the dairy calf to beef system can be summarized as follows. Under current conditions optimum slaughter weights of young bulls are 500-550 kg at the ages of 17-18 months. Biological efficiency as measured by carcass weight production per animal, carcass and meat qualities, increased with increasing of slaughter weights from 400 to 550kg. The same pattern has occurred for net return, but profitability was unchanged. Production systems with light slaughter live weights require more number of cattle by 14-41 percent to produce the same carcass weights. On the other hand feed conversion of the bulls slaughtered at light live weights was higher. Meat potential of Black and white breed with high proportion of Holstein blood is good enough to produce quality lean carcasses.

Effect of replacement rate, crossbreeding and sexed semen on the efficiency of beef production from dairy herds in Finland

In Finland, during the past 10 years, the number of dairy cows has declined considerably leading to decreased domestic beef production which is partly compensated by increased suckler beef production. However, production of meat originating from dairy herds has been shown to be economically more profitable and to produce less greenhouse gas emissions per unit of product than beef production from suckler cow systems. Therefore, when safeguarding beef self-sufficiency, the intensification of beef production from dairy herds is a more promising option to consider. In this study, the possibility of different options for increasing dairy beef production was assessed by using a deterministic simulation. Increasing the use of crossbreeding in dairy herds, especially when combined with the use of Y-sorted semen, appeared to be the most efficient strategy for increasing dairy beef production. The decrease in the replacement rate increased beef production through the potential for enhancing crossbreeding.

Fatty acid profiles, meat quality, and sensory attributes of organic versus conventional dairy beef steers

Meat from Holstein and crossbred organic and conventional dairy steers were evaluated and compared for fatty acid profiles, meat quality, sensory attributes, and consumer acceptance. Bull calves (n=49) were randomly assigned to 1 of 3 replicated groups: conventional (CONV), organic (ORG, pasture + concentrate), or grass-fed organic (GRS) and were born at the University of Minnesota West Central Research and Outreach Center (Morris, MN) between March and May 2011. The CONV steers (n=16) were fed a diet that contained 80% concentrate and 20% forage, and ORG steers (n=16) were fed a diet of organic corn, organic corn silage, and organic protein supplement. Furthermore, ORG steers consumed at least 30% of diet dry matter of high-quality organic pasture during the grazing season. The GRS steers (n=17) consumed 100% forage from pasture during the grazing season and high-quality hay or hay silage during the nongrazing season. The ORG steers had fat that was greater in oleic acid (C18:1) than the GRS and CONV steers (47.1, 36.1, and 39.9%, respectively). The GRS steers (21.9%) were lower for monounsaturated fat than the ORG (42.1%) and CONV (40.4%) steers. Furthermore, the GRS steers tended to have greater n-3 fat and had lower n-6 fat than the ORG and CONV steers. Consequently, the GRS (1.4%) steers had a lower n-6-to-n-3 fat ratio than the ORG (12.9%) and CONV (10.0%) steers. The GRS (2.6kg) steers had steaks that were not different for Warner-Bratzler shear force than ORG (2.3kg) steaks; however, the GRS steaks tended to have greater shear force than the CONV (2.0kg) steaks. The 3 steer group had steaks that were not different for color brightness (L*; 0 = black and 100 = white) and yellowness/blueness (b*; positive values = yellow and negative values = blue) values; however, the GRS (10.5) steaks had lower redness/greenness (a*; positive values = red and negative values = green) values than CONV (14.5) steaks. For sensory attributes (0- to 120-point scale), no differences were observed for ORG (71.3) and CONV (69.2) steers for overall consumer liking of the beef; however, the GRS (56.3) steers had the lowest overall liking among beef consumers. The ORG (73.3) steers had greater flavor liking than the GRS (56.8) and CONV (69.2) steers. Conversely, the GRS (6.3) steers had the highest scores for off-flavor (0- to 20-point scale) compared with the ORG (3.9) and CONV (4.1) steers. The results of the current study suggest that a potential market may exist for organic grass-fed dairy steers in the United States, but quality and consistency of the beef needs to be improved.

Growth, carcass characteristics, and profitability of organic versus conventional dairy beef steers

Bull calves (n=49), born at the University of Minnesota West Central Research and Outreach Center (Morris) between March and May 2011, were used to compare growth measurements and profitability of conventional and organic dairy steers. Calves were assigned to 1 of 3 replicated groups at birth: conventional (CONV; n=16), organic (pasture and concentrate; ORG; n=16), or organic grass only (GRS; n=17), and analysis of variables was on a pen basis. Breed groups of calves were Holstein (HO; n=9); Holsteins (n=11) maintained at 1964 breed average level; crossbreds (n=19) including combinations of HO, Montbéliarde, and Swedish Red; and crossbreds (n=10) including combinations of HO, Jersey, Swedish Red, and Normande. The CONV steers were fed a diet of 80% concentrate and 20% forage. The ORG steers were fed a diet of organic corn, organic corn silage, and at least 30% of their diet consisted of organic pasture during the grazing season. The GRS steers grazed pasture during the grazing season and were fed high-quality hay or hay silage during the nongrazing season. Intakes of a total mixed ration were recorded daily with herd management software. A profit function was defined to include revenues and expenses for beef value, feed intake, pasture intake, health cost, and yardage. The GRS (358.6kg) steers had lesser total gains from birth to slaughter than ORG (429.6kg) and CONV (534.5kg) steers. Furthermore, the GRS (0.61kg/d) steers had lesser average daily gain from birth compared with ORG (0.81kg/d) and CONV (1.1kg/d) steers. The GRS and ORG steers had smaller rib eye area (49.5 and 65.8cm2, respectively) compared with CONV (75.4cm2) steers. For profitability, GRS steers had 43% greater profit than CONV steers due to organic beef price premiums and lower feed costs. On the other hand, ORG steers had substantially less profit than CONV steers. The higher cost of production for the ORG steers is due to the extreme high value of organic corn. The results of the current study illustrate the economic potential of alternative strategies for growing and marketing male offspring of organic dairy cattle in the Midwest.

Dairy cow handling facilities and the perception of Beef Quality Assurance on Colorado dairies

A survey was conducted on Colorado dairies to assess attitudes and practices regarding Dairy Beef Quality Assurance (DBQA). The objectives were to (1) assess the need for a new handling facility that would allow all injections to be administered via DBQA standards; (2) establish if Colorado dairy producers are concerned with DBQA; and (3) assess differences in responses between dairy owners and herdsmen. Of the 95 dairies contacted, 20 (21%) agreed to participate, with a median herd size of 1,178. When asked to rank the following 7 traits—efficiency, animal safety, human safety, ease of animal handling, ease of operation, inject per Beef Quality Assurance (BQA) procedures, and cost—in order of priority when designing a new handling facility, human and animal safety were ranked highest in priority (first or second) by the majority of participants, with ease of animal handling and efficiency ranked next. Interestingly, the administration of injections per BQA standards was ranked sixth or seventh by most participants. Respondents estimated the average annual income from the sale of cull cows to be 4.6% of all dairy income, with 50% receiving at least one carcass discount or condemnation in the past 12 mo. Although almost all of the participating dairy farmers stated that the preferred injection site for medications was the neck region, a significant number admitted to using alternate injection sites. In contrast, no difference was found between responses regarding the preferred and actual location for intravenous injections. Although most participating producers are aware of BQA injection guidelines, they perceive efficiency as more important, which could result in injections being administered in locations not promoted by BQA. Dairy owners and herdsmen disagreed in whether or not workers had been injured in the animal handling area in the last 12 mo. Handling facilities that allow for an efficient and safe way to administer drugs according to BQA guidelines and educational opportunities that highlight the effect of improved DBQA on profitability could prove useful. Dairy producers play a key role in ensuring that dairy beef is safe and high quality, and just as they are committed to producing safe and nutritious milk for their customers, they should be committed to producing the best quality beef.

The impact of uncertainties on predicted greenhouse gas emissions of dairy cow production systems

Abstract Dairy farms produce significant greenhouse gas (GHG) emissions and are therefore a focal point for GHG-mitigation practices. To develop viable mitigation options, we need robust (insensitive to changes in model parameters and assumptions) predictions of GHG emissions. To this end, we developed a stochastic model to estimate the robustness of predictions based on input parameters (GHG emission factors and production traits) and their uncertainties. In our study we explored how sensitive predictions of GHG emissions are to three factors: (1) system boundaries of the emission model (2) the uncertainty of input parameters due to quality of data or methodological choices (epistemic uncertainty) and (3) inherent variability in input parameters (variability uncertainty). To assess the effect of system boundaries, we compared two different boundaries: the “dairy farm gate” boundary (all GHG emissions are allocated to milk) and “system expansion” (the model gives a GHG credit to beef derived from culled cows and bull, heifer and calf fattening of surplus dairy calves outside the farm). Results using the farm-gate boundary provide guidance to dairy farmers to reduce GHG emissions of milk production. The results using system expansion are important for defining GHG abatement policies for milk and beef production. We found that the choice of system boundary had the strongest impact on the level and variation of predicted GHG emissions. Model predictions were least robust for lower-yielding dairy cow production systems and when we used system expansion. We also explored which GHG-abatement strategies have the most leverage by assessing the influence of each input parameter on model predictions. Predicted GHG emissions were least sensitive to variability-related uncertainty in production traits (i.e. replacement rate, calving interval). Lower-yielding production systems had the highest variation, indicating the highest potential for GHG mitigation of all production systems studied. Variation in predicted GHG emissions increased substantially when both epistemic and variability uncertainty in emission factors and variability uncertainty in production traits were included in the model. If the system boundary was set at the farm gate, the emission factor of N 2 O from nitrogen input into the soil had the highest impact on variation in predicted GHG emissions. This variation stems from uncertainties in predicting N 2 O emissions (epistemic uncertainty) but also from inherent variability of N 2 O emissions over time and space. The uncertainty of predicted GHG emissions can be reduced by increasing the precision in predicting N 2 O emissions. However, this additional information does not reduce GHG emissions itself. Knowing site specific variability of N 2 O emissions can help reduce GHG emissions by specific management (e.g. reduce soil compaction, adopted manure management, choice of suitable crops). In case of system expansion, uncertainty in GHG emission credit for dairy beef contributed the most to increasing the variation in predicted GHG emissions. The stochastic-model approach gave important insights into the robustness of model outcomes, which is crucial in the search for cost-effective GHG-abatement options. Despite the high degree of uncertainty when using system expansion, its results help identifying global GHG mitigation options of combined milk and beef production.

Bioeconomic modelling of compensatory growth for grass-based dairy calf-to-beef production systems

SUMMARYFeed makes up c. 0·7 of total variable costs on Irish beef farms. A period of reduced growth (caused by nutritional restriction) followed by a period of accelerated growth (compensatory growth) can be used to take advantage of lower cost feedstuffs (grazed grass) during the grazing season. The Grange Dairy Beef Systems Model (GDBSM) was modified to capture more accurately the implications of compensatory growth and, thus, the energy demand of beef cattle was partitioned into energy required for maintenance and energy required for growth. For the current study, three production systems were evaluated where the male progeny of dairy cows were finished as steers at 24 (S24), 28 (S28) and 30 (S30) months of age. Three different live weight gains (RESLWG; 0·4, 0·6 and 0·8 kg/day), reflecting different levels of nutritional restriction, were simulated during the first winter feeding period (November–February) for S24 and during the second winter feeding period for S28 and S30. This allowed the effect of different live weight gains during a nutritional restriction period on farm profitability to be determined. Results indicated that for S24 the most profitable RESLWG was 0·6 kg/day. However, for S28 and S30 the most profitable systems were RESLWG of 0·4 kg/day. Financial performance of all systems was very sensitive to variation in beef carcass and calf prices but less sensitive to concentrate and fertilizer price variation. Furthermore, sensitivity analysis showed that the level of maintenance energy reduction and the duration of this reduction had a modest impact on results. The GDBSM is demonstrated as a quantitative framework for simulating compensatory growth and determining its effects on the profitability of dairy calf-to-beef production systems.

Non-parametric approaches to the impact of Holstein heifer growth from birth to insemination on their dairy performance at lactation one

SUMMARYParametric approaches have been used widely to model animal growth and study the impact of growth profile on performance. Individual variation is often not considered in such approaches. However, non-parametric modelling allows this. Such an approach, based on spline functions, was used to study the importance of growth profiles from age 0 to 15 months (i.e. insemination) on milk yield and composition in primiparous cows. A dataset of 447 heifers was used for analysis of growth performance; 296 of them were also used to study impact on lactation. All of them originated from a French experimental herd and were born between 1986 and 2006. Clustering methods were also tested. Comparison of spline methods showed that a cubic spline interpolation method, with no smoothing parameter, was best suited to studying heifer growth. Similarly, partitioning around medoids proved the most accurate clustering method for classifying heifer growth into groups. The results of these analyses agreed with those previously published, supporting the utility of these methods. A final study on the impact of breakdowns in the growth curves was performed. A breakdown was considered only when the derivative of the interpolation function was negative or zero. Of the 447 heifers initially used, 125 (Gr0), 175 (Gr1) and 147 (Gr2) had no, one, or two or more breakpoints during the 0–15 months of age period. Milk yield on a 305 d basis was significantly reduced with an increased number of breakpoints (6548v.6828 and 6905 kg for Gr2, Gr1 and Gr0 animals, respectively). Fat content was also higher in Gr2 than in Gr0 groups, but overall, no difference in total fat or protein-corrected milk production was noted. The intersection between groups for growth and groups for breakdowns confirmed that animals with two or more breakdowns belonged more frequently to the group with the lowest growth performance. These results offer the possibility of analysing large databases, originating from an automatic collecting system (e.g. milking robots) or from different herds, breeds, genetics, etc. These approaches could also be used for studies on body score index, girth development, lactation profiles, etc. and in other species, such as dairy goats or beef cattle. They could find use in the development of new models of prediction, e.g. the probability of heat appearance on an animal basis, which could be included among useful management tools.

Impact of a Dairy Beef Quality Assurance Extension Program on Producer Cull Cow Management Practices and Meat Quality Knowledge

Impact of a Dairy Beef Quality Assurance Extension Program on Producer Cull Cow Management Practices and Meat Quality Knowledge

Simulation modelling of temperate grassland based dairy calf to beef production systems

Profitable beef farming requires continuous appraisal and adaptation of production systems in response to advances in technology and evolving market and agricultural policy conditions. In this context bioeconomic models can be a useful aid to researchers seeking to understand how production systems react to these changing circumstances. A mathematical model, the Grange Dairy Beef Systems Model (GDBSM), is presented and used to simulate grassland based dairy calf to beef systems. The whole farm model consists of four interdependent components comprising farm system, animal nutrition, feed supply and financial sub models. Model applications are presented through the analysis of production scenarios concerning three cattle breed types and two finishing ages with the sensitivity of these scenarios to beef, fertiliser and concentrate price also outlined. The model results highlight the small and sometimes negative net margins (ranging from −€3000 to €13,000 on a per farm basis) of dairy calf to beef systems even with technically efficient management. The financial performance of all systems examined was sensitive to variation in beef price but relatively insensitive to variation in concentrate and fertiliser prices; on average the net margin per farm changed by €9900, €1800 and €500, respectively, as the beef, concentrate and fertiliser price increased and decreased by 10%. The model presented can be used to increase understanding of the complex relationships within dairy calf to beef production systems.

Antimicrobial susceptibility of Salmonella isolates recovered from calves with diarrhoea in Australia

OBJECTIVE To identify the common serotypes and antimicrobial resistance patterns of Salmonella spp. associated with diarrhoea in Australian dairy calves under the age of 6 weeks. DESIGN Cross-sectional study. METHODS Faecal samples were collected from outbreaks of diarrhoea in dairy and dairy beef calves less than 6 weeks old. Samples were screened for Salmonella using standard enrichment culture techniques. The antimicrobial susceptibility to 12 commonly used veterinary and human antimicrobials was assessed using the Kirby-Bauer disk diffusion method and the susceptibility profiles of dairy and dairy beef properties were compared using Fisher's exact test. RESULTS Salmonella ser. Dublin, S. ser. Typhimurium and S. ser. Bovismorbificans were the three most common salmonella serotypes isolated. The majority of properties had one serotype. Most of the Salmonella isolates were not resistant to any of the antimicrobials tested. No resistance was seen to amikacin and nalidixic acid, and only one isolate was resistant to ceftiofur or amoxicillin-clavulanic acid. The most common antimicrobial resistance was to streptomycin, ampicillin or combination sulfonamides. Multi-drug resistance was detected in S. ser. Anatum, S. ser. Bovismorbificans, S. ser. Muenster, S. ser. Newport and S. ser. Typhimurium. Isolates from dairy beef properties were more likely to be resistant to ampicillin, kanamycin, neomycin, sulfamethoxazole/trimethoprim and tetracycline (P < 0.05) and were more likely to exhibit multi-drug resistance. CONCLUSION The prevalence of antimicrobial resistance in Salmonella isolates from dairy calves in Australia is low compared with that reported overseas. From a human health perspective, resistance to antimicrobials used in the treatment of human salmonellosis was infrequent.

Prevalence of major enteric pathogens in Australian dairy calves with diarrhoea

Objective Determine the prevalence of the major enteric pathogens in dairy and dairy beef calves with diarrhoea in Australia. Design Cross‐sectional study. Methods Faecal samples from 84 Australian dairy and dairy beef properties (597 samples) were screened for rotavirus and coronavirus using real‐time reverse transcription polymerase chain reaction, for Salmonella spp. using selective enrichment faecal culture, and for enterotoxigenic Escherichia coli (K99) and Cryptosporidium parvum using a commercial enzyme‐linked immunosorbent assay. A logistic regression with random effects model was used to compare prevalence of pathogens in dairy and dairy beef operations. Results Enteric pathogens were isolated from 97.6% of outbreaks and 95.0% of samples. Rotavirus was the most common pathogen identified (477/597, 79.9%) followed by C. parvum (349/597, 58.5%), Salmonella spp. (142/597, 23.8%), coronavirus (129/597, 21.6%) and E. coli K99 (104/597, 17.4%). Multiple pathogens were identified on 96.4% of farms and from 71.0% of samples. Samples from dairy beef properties were more likely to have multiple pathogens than dairy properties (P < 0.05), whereas rotavirus and Salmonella spp. were more likely to be identified in samples collected from dairy beef than dairy properties (P < 0.05). Conclusion Most outbreaks of calf diarrhoea in dairy and dairy beef operations involve multiple pathogens. Rotavirus and C. parvum were the most frequently identified pathogens across production systems. Salmonella spp. and rotavirus were more frequently identified in dairy beef operations.

A Retrospective study of Brucellosis Seroprevalence in Commercial and Smallholder Cattle Farms of Zimbabwe.

A retrospective study covering 10 years (1995 – 2004) was conducted to investigate brucellosis seroprevalence and patterns in commercial and smallholder mixed dairy-beef cattle in Zimbabwe using surveillance data from the Central Veterinary Laboratory at Harare. Positive cases were analysed according to farming sector, administrative province, monthly andannual trends. The overall individual and herd- level brucellosis seroprevalence were estimated at 2.9% (2417/183990) and 17.8% (505/2833) respectively. Brucellosis seroprevalence varied significantly among the eight provinces of the country (p

Relationships between urine pH and electrolyte status in cows fed forages

Data of 20 balance measurements from Holstein dairy cows and urine samples from 24 Japanese Black beef cows were collected to evaluate the relationships between urine pH and electrolyte status in cows fed forages. The ratio of forages in the diet was 70-100% in dairy cows and beef cows were fed Italian ryegrass silage and wheat bran. Mean urine pH in dairy cows was 8.10, ranging from 7.27 to 8.71, and that in beef cows was 7.73, ranging from 7.42 to 8.12. There were positive correlations between urine pH and urinary K contents (P = 0.0012) or K intake (P = 0.019) in dairy cows, although plasma Na, Cl and K had no effect on urine pH. There was a weak negative correlation (P = 0.039) between urine pH and urinary Na content in dairy cows. However, there were no significant correlations between urine pH and urinary Na, Cl and K contents in beef cows. These results indicate that the concentrated urinary K due to the increased K intake may directly enhance urine pH in dairy cows fed mainly forages.

The effect of intramuscular injection of dinoprost or gonadotropin-releasing hormone in dairy cows on beef quality1

Intramuscular injections of drugs and vaccines cause tissue damage and subsequent effects on tenderness and consumer acceptability of beef. In the 2007 National Market Cow and Bull Beef Quality Audit, 100% of plants reported fabricating subprimal cuts such as rib eyes and tenderloins from cow and bull carcasses. Dairy beef quality should therefore be a consideration when injections are given to dairy animals. The discussion about injection site reactions and tenderness has focused on vaccines and antimicrobial drugs with little concern for the effects of reproductive hormones. The objective of this study was to quantify antemortem the effects of semimembranosis/semitendinosis muscle injection of dinoprost and GnRH in lactating dairy cows by estimating the weight of tissue damaged and comparing that with a drug known to cause extensive tissue damage, flunixin meglumine. Tissue damage was estimated from previously reported equations for grams of muscle tissue damage based on area under the curve of serum concentrations of the muscle enzyme creatine kinase over time. Dinoprost and flunixin injection both caused a significantly increased estimate of muscle tissue damaged compared with needle only (P = 0.0351 and 0.0355, respectively). Dinoprost and flunixin caused a marginally significant increased muscle tissue damage compared with GnRH (P = 0.1394 and 0.1475, respectively). No statistically significant difference was found between the estimated weight of muscle tissue damaged by flunixin compared with dinoprost (P = 1.0000), or by saline compared with GnRH (P = 0.7736) or needle only (P = 0.4902). The assumption that reproductive hormones are less damaging than vaccines and antimicrobial drugs should be examined more closely, including postmortem evaluation of injection site lesions and effects on tenderness.

Long-term trends in production and composition of ryegrass-white clover pasture intensively grazed by dairy-beef cattle

A measure of pasture persistence is stability of yield and proportion of desirable species over a long period. Long-term data on animal production and pasture yield and composition of old permanent pasture in the Manawatu were examined for trends indicative of persistence. The data were collected from two sets of replicated 1.6-ha farmlets intensively grazed by dairybeef bulls stocked at 7.4 yearlings wintered/ha for 16 of 18 years from 1969-1986, and 11 years from 1978 and 1988, respectively. Annual total LWG, total yield of DM and the yields of ryegrass, white clover and other species showed year-to-year variation. There was no long-term decline in production indicating that for this environment and management system ryegrass and white clover were inherently persistent under intensive grazing at high stocking rates. These results are discussed in the context of anecdotal reports of poor persistence of modern cultivars, with particular emphasis on the effects that high stocking rates, intensive utilisation and defoliation management may have on persistence. Keywords: cattle, grazing, pasture, persistence, ryegrass, white clover

Effect of selected factors on mineral parameters in plasma of cows

Abstract. Objective of this paper was to evaluate the effects of herd, exploitation, management system, and season on blood macro and micro-minerals in cows kept in a mountainous region. The cows were kept in four herds, two exploitation manners, and two systems. Concentrations of calcium (Ca), phosphorus (P) were significantly differed in the factors of herd and exploitation only, levels of copper (Cu) and zinc (Zn) showed differences in all factors. Beef animals had higher level of P than dairy exploitation (1.59 mg.L−1 vs. 1.42 mg.L−1; P&lt;0.01) and lower level of Ca (2.10 mg.L−1 vs. 2.33 mg.L−1; P&lt;0.001). Higher concentrations of Cu and Zn were recorded in dairy exploitation (0.91 mg.L−1, 1.17 mg.L−1) versus beef exploitation (0.67 mg.L−1, 0.86 mg.L−1) (P&lt;0.001). We found higher concentrations in Cu (0.84 mg.L−1 vs. 0.62 mg.L−1 , P&lt;0.001) and Zn (1.06 mg.L−1 vs. 0.96 mg.L−1, P&lt;0.05) in non-ecological system. There were higher values of Cu and Zn in fall than spring (0.90 mg.L−1 and 1.10 mg.L−1 vs. 0.67 mg.L−1 and 0.93 mg.L−1) (P&lt;0.001).