Technical and Economic Effects of Culling and Reproduction Strategies in Dairy Cattle Herds Estimated by Stochastic Simulation

Abstract

The objective of this study was to create operational replacement guidelines under various conditions concerning reproductive performance, supply of replacement heifers and individual milk yield. Nine culling strategies were defined by three average insemination periods and by three discrimination policies between high- and low-yield cows. The effect of the nine culling strategies was analysed with combinations of heat detection rate and time of initiation of breeding after calving under two replacement heifer purchase policies: purchase (open herd) and no purchase (closed herd). The strategies were evaluated using a stochastic simulation model that simulated production and reproductive status in herds composed of dual-purpose cattle with additional young stock. The evaluation of the strategies was made in a situation without a milk quota under typical Danish conditions in 1993. Results showed that discriminating between high- and low-yield cows improved net revenue significantly in open herds but not in closed herds. Irrespective of the purchase policy, using longer insemination periods increased net revenue significantly in herds with poor reproductive performance; whereas net revenue in herds with good reproductive performance tended to increase by using shorter insemination periods. The culling rate is a poor figure when evaluating culling strategies and culling strategies should be assessed at herd level rather than per cow.     

Effect of the composition of the ration during the dry period on fertility and milk production of Holstein cows in Israel

In each for of kibbutzin herds located in Israel the dry cows were divided in two feeding groups. The experimental group, in totally 266 cows, obtained only oat, barley or wheat hay ad libitum, whereas the control group (n = 253) was fed additionally mix or silage up to four kg dry matter. The cows in the control group responded in the following lactation with a 1.3 kg higher average FCM per day (p = 0.02) and with a 1.7 kg higher maximum FCM (p = 0.01) in comparison to the experimental group. The differences between the experimental and control group in A. I.-parameters days open, conception rate on first insemination and percent problem cows were rather small. However, the frequency of retained placenta and ovary cysts was significantly (p less than 0.05) higher in the control group than in the experimental group. In one herd the influence of body condition between the end of lactation, dry period and 50-80 days p.p. as well as the change of body weight between the end of lactation and calving on milk production and fertility could be evaluated. A decrease of one body condition score unit between the dry period and 50-80 days p.p. was associated with an increase of FCM by 2.01 kg (p less than 0.01), a decrease of the conception rate by 21% (p less than 0.05) and an elongation of the days open by 23.6 days (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

全混合日粮饲喂产奶牛经济效益试验

研究全混合日粮与非全混合日粮饲喂产奶牛,选择200头荷斯坦奶牛随机分为试验组和对照组,试验组饲喂全混合日粮,对照组饲喂相同配方和数量的草料,经30 d饲喂对比试验,结果表明：试验组日平均产奶量为23.52 kg,对照组日平均产奶量为21.78 kg,试验组比对照组日平均产奶量增加1.74 kg,日平均产奶量提高7.99%,差异极显著（P〈0.01）。饲喂全混合日粮组比饲喂非全混合日粮组奶牛增收17 760元,经济效益明显。     

酵母蛋白饲喂泌乳奶牛试验报告

本试验通过在荷斯坦泌乳牛日粮中添加酵母蛋白部分替代豆粕,研究其对泌乳牛干物质采食量、产奶量、乳成分及身体健康情况的影响,选取400头胎次、产奶量相近的中国荷斯坦泌乳牛分为对照组和试验组各200头,试验组每头牛每天饲喂500g酵母蛋白,通过60d的试验,结果表明试验组和对照组奶牛平均日产奶量差异不显著（P〉0.05）,分别为32.54kg/d与32.34kg/d。在产奶量不变的基础上,试验组平均干物质采食量降低1.7kg（DM）/d,产奶效率提高,与对照组相比差异极显著（P〈0.01）。     

Clinical acidosis in a Gippsland dairy herd

OBJECTIVE: To report on spontaneous clinical and subclinical acidosis in a large dairy herd, to evaluate the diets and feeding strategies involved, and to report on measures of rumen function in the cows affected. DESIGN: A Gippsland dairy herd was sampled as part of a wider randomised cross-sectional study that examined the prevalence, risk factors for, and effects of, acidosis on rumen function of dairy cattle. Three herds on the farm were involved in the study: the transition herd (cows 3 weeks prior to calving), the very fresh lactating herd (1 < days in milk < 10, herd 1) and the fresh lactating herd (10 < days in milk < 120, herd 2) including a small lame herd fed separately. The transition cows were fed 2 kg dry matter triticale per cow per day and hay with an estimated total dry matter intake of 4.8 kg per cow per day. The lactating cow diet included 6.75 kg dry matter triticale per cow per day with total concentrate fed being 8.1 kg dry matter per cow per day in the milking parlour. Silage, lucerne cubes, hay and pasture (herd 2 only) was also fed to the lactating cows with the estimated total dry matter intake for cows in herds 1 and 2 being 13.7 kg and 20.8 kg per cow per day respectively. Three primiparous and five multiparous cows in early lactation (< 100 days in milk) were randomly selected from each of two lactating herds: herds 1 and 2. Rumen fluid was sampled from each cow by both rumenocentesis and stomach tube. The rumenocentesis samples were tested for pH at the time of sampling. Stomach tube samples were frozen and subsequently tested for volatile fatty acid, ammonia, and D- and L-lactate concentration. RESULTS: In the very fresh herd, there was a high prevalence of severe lameness and scouring, coupled with a mean rumen pH 5.67, low mean total volatile fatty acid concentration 71.0 mM and high mean concentrations of L- and D-lactate, (7.71 mM and 7.31 mM), respectively. Cows in the fresh herd had moderate signs of scouring and lameness. A lame herd comprising approximately 50 cows separated from the fresh herd was also present on the farm. The mean rumen pH of the fresh herd was 5.74 and mean rumen concentrations of volatile fatty acids, ammonia, L- and D-lactate were within ranges considered normal. CONCLUSIONS: The transition diet failed to supply sufficient energy and protein for maintenance of cows of this live weight in late gestation. The diet fed to the very fresh herd was low in effective fibre and contained an excessive content of non-structural carbohydrate in the form of processed, rapidly fermentable grain. The sudden change from the transition diet to the diet fed to the very fresh herd probably also precipitated the outbreak of acidosis. This case report provides unique detail, including information on diets and rumen parameters, of an outbreak of acidosis in a pasture-fed herd.     

Use of partial budgeting to determine the economic outcome of Staphylococcus aureus intramammary infection reduction strategies in three Ohio dairy herds

Efforts to reduce the prevalence of Staphylococcus aureus intramammary infection were monitored in 3 Ohio dairy herds. Bacteriologic culturing of milk from all lactating cows in each herd was completed multiple times to identify infected cows and monitor reduction. Partial budgeting techniques were used to determine the economic outcome of the reduction program. Of particular emphasis was the economic impact of culling to maintain or achieve milk quality premium payments on the basis of bulk tank somatic cell counts. The prevalence of S aureusinfected cows was reduced in each herd. Culturing of milk from all lactating cows appeared to be an effective method to identify infected cows. Although numbers were limited, it also appeared that culturing of composite quarter samples was effective as a herd screening test to identify S aureus-infected cows. Bacteriologic culturing had a negative financial impact in all 3 herds. Using partial budgeting to assess the economic impact of the programs, it was determined that 2 herds experienced negative financial impacts as a result of an excess culling rate when compared with a 12-month baseline period prior to the initiation of the project. All herds had increased milk production per cow during the study as measured by the mature-equivalent method. However, when actual production was considered, increased milk production in each herd was not as great as that of other Ohio herds enrolled on Dairy Herd Improvement Association testing programs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of different dry period lengths on production and economy in the dairy herd estimated by stochastic simulation

A range of preplanned dry period lengths in a dairy herd was evaluated, at different culling strategies and feeding regimes, by means of a dynamic stochastic model simulating the production at herd level. Dry period lengths were studied in the range of 4 to 10 weeks. The culling strategies exhibited two different rates of voluntary culling for reproductive failure and milk production, and the feeding regimes consisted of grass silage ad lib. and either 8 or 12 kg of concentrates/day in the first 24 weeks of lactation. The economic result was studied under a herd size and a milk quota constraint, respectively. A dry period of seven weeks appeared to be preferable under most circumstances. The net revenue per unit of milk sold was less sensitive to dry period length than the net revenue per cow per year. No major interactions between dry period length and culling strategy or feeding regime were found. The conclusions were fairly insensitive to price changes, and to variation in the assumed effect on lactational performance of dry period lengths from 6 to 8 weeks.     

Comparison of methods to evaluate the energy supply in dairy herds

Different methods to evaluate the nutritional and metabolic status in dairy herds are available. The aim of this study was to evaluate three different methods to assess the energy status of the herd: 1) the calculation of the energy balance of the herd with a new method based on the Swiss standard calculations, 2) the "efficiency of the feeding management" based on milk yield and milk protein content (%) obtained from DHI data, and 3) the percentage of cows per herd with an average milk yield (16-25 kg/day), but a low milk protein (< 3.2 %). The study included data from 47 farms enrolled in the herd reproduction survey program of the University of Berne, with a total of 653 cows included in one winter period. A correlation could only be seen between methods two and three. It is concluded that it is insufficient only to calculate the ration as an estimation of the energy status of the herd. A rough calculation of the ration is necessary to have an idea on the energy density. But the calculated ration seems to be considerably different from the amount of energy and nutrients of the diet finally absorbed by the cow. As the ingested ration is relevant for milk production and animal health, the relationship between milk yield and milk protein content as well as the percentage of cows with milk protein < 3.2% are considered to provide good information about the efficiency of the feeding management in dairy herds.     

Effects of sodium monensin on reproductive performance of dairy cattle. I. Effects on conception rates, calving-to-conception intervals, calving-to-heat and milk production in dairy cows

SUMMARY A total of 1061 lactating dairy cows in six different herds were randomly allocated to treatment and control groups. One herd was lot-fed on total mixed rations; three herds were fed on pasture with significant amounts of supplementary concentrates, and two herds were primarily pasture fed. Treated cows received a slow-release, intraruminal capsule containing 32 g sodium monensin within 7 days of calving. Conception rates at first service, days to first oestrus and calving-to-conception interval did not differ significantly between untreated and monensin-treated cows in the 5 herds, 3 herds and 4 herds, respectively, in which these outcomes were examined. Treatment of lactating cows immediately after calving may not be the optimal method to achieve fertility responses with capsules containing sodium monensin. Monensin treatment significantly increased milk yield in one of the six herds. Milk fat or milk protein production was not significantly affected by treatment.     

Effects of seropositivity for bovine leukemia virus, bovine viral diarrhoea virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum on culling in dairy cattle in four Canadian provinces

The purpose of this research was to determine the effects of seropositivity for exposure to bovine leukemia virus (BLV), bovine viral diarrhoea virus (BVDV), Mycobacterium avium subspecies paratuberculosis (MAP) and Neospora caninum (NC) on overall and reason-specific culling in Canadian dairy cattle. Serum samples from, approximately, 30 randomly selected cows from 134 herds were tested for antibodies against BLV, MAP and NC using commercially available ELISA test kits, while 5 unvaccinated cattle over 6 months of age were tested for antibodies to bovine viral diarrhoea virus (BVDV). For analyzing the time (in days) to culling of cows after the blood testing, a two-step approach was utilized, non-parametric (Kaplan-Meier survival graphs) visualization and then semi-parametric survival modelling (Cox proportional hazards model), while controlling for confounding variables and adjusting for within herd clustering. For all reasons of culling, MAP-seropositive cows had a 1.38 (1.05-1.81, 95% C.I.) times increased hazard of culling compared to MAP-seronegative cows. Seropositivity for the other pathogens was not associated with an increased risk of overall culling. Among cows that were culled because of either decreased reproductive efficiency or decreased milk production or mastitis, MAP-seropositive cows were associated with 1.55 (1.12-2.15, 95% C.I.) times increased hazard compared to MAP-seronegative cows. Among cows that were culled because of reproductive inefficiency, NC-seropositive cows had a 1.43 (1.15-1.79, 95% C.I.) times greater hazard than NC-seronegative cows. Among cows that were culled because of decreased milk production, cows in BVDV-seropositive herds had a 1.86 (1.28-2.70, 95% C.I.) times increased hazard compared to cows in BVDV-seronegative herds. BLV-seropositive cows did not have an increased risk of reason-specific culling as compared to BLV-seronegative cows. No significant interaction on culling among seropositivity for the pathogens was detected, but only a limited number of cows tested seropositive for multiple pathogens. Results from our research will help in better understanding the economic impacts of these pathogens and justification for their control.     

Effects of anionic salts supplementation on blood pH and mineral status, energy metabolism, reproduction and production in transition dairy cows

The objectives of this study were to determine the effects of a pre-partum diet with lower than recommended (DCAD = −82 mEq/kg of dietary DM) amounts of anionic salts on metabolism, health, reproductive performance and milk production in dairy cows. Sixty Holstein multiparous cows were enrolled 21 days prior to expected calving date. The animals were randomly assigned to receive one of two rations: 30 cows received anionic ration [−82 mEq (NA + K − Cl − S)/kg of DM] for 21 d to parturition and the other group (n = 30) were fed a usual dry period ration (+192 mEq/kg of DM). Serum samples obtained at days −21, +3 and +21 relative to calving were analyzed for β-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), glucose, calcium (Ca), inorganic phosphorus, magnesium, chloride, sodium, potassium, cholesterol, urea, creatinine, total protein, albumin, and aspartate aminotransferase (AST). Urine pH declined from 8.4 at 21 d before calving (pre-treatment) to 6.2 at day 7 pre-partum in the treatment group. Repeated-measure mixed model analysis indicated that the concentrations of Ca were significantly increased and creatinine, and AST were significantly decreased by lowering DCAD. The concentrations of BHBA, NEFA and glucose were not affected by treatment. The incidence of milk fever and culling were 5 and 11 times higher in the control group in comparison with the treatment group, respectively. The intervals from calving to first breeding and to pregnancy were not influenced by treatment. There was no group effect on average daily milk yield or fat percentage.     

Associations between use of electric cow-trainers and clinical diseases, reproductive performance and culling in Swedish dairy cattle

The aims of this follow-up study were: (a) to evaluate the role of ECT technology as a risk factor for several diseases; and (b) to determine if the effects of these diseases on cows' reproductive performance and as risk factors for culling are influenced by exposure to ECTs. Diseases considered were retained placenta, metritis, ketosis, cystic ovaries, silent heat, milk fever, clinical mastitis, and foot and leg problems. We used historical and contemporary controls (with control herds selected to match the experimental herds for size and location). Data consisted of 10264 Swedish Red and White (SRB) and 5461 Swedish Friesian (SLB) lactation records in 150 herds of which 33 used cow-trainers. Logistic regression was used to estimate the effects of parity and exposure to electric cow-trainers on the risks of diseases and the effects of diseases and exposure to electric cow-trainers on risk of culling. The least-squares procedure was used to estimate the effects of diseases on reproductive performance.

The dominant effects associated with use of electric cow-trainers were an increased risk for silent heat, clinical mastitis, ketosis and culling relative to cows in herds not using cow-trainers. Diseases had negative effects on reproductive performance and the effects were larger for cows in herds using cow-trainers. In herds using electric cow-trainers, the largest increase in the interval from first service to conception (58 days) was caused by the occurrences of silent heat, cystic ovaries and the combination of two or more diseases. Retained placenta, metritis, cystic ovaries, clinical mastitis and a combination of two or more diseases increased the risk of culling about two times relative to healthy primiparous cows with the increase being greater for cows in herds using cow-trainers. Silent heat did not increase risk of culling in control groups, but was the largest risk factor for culling in the exposed group. We concluded that exposure to electric cow-trainers increased the incidence risk of silent heat, clinical mastitis, and ketosis and changed silent heat from a neutral disease with respect to culling to a major risk factor. Finally, exposure to cow-trainers increased the general negative effect of diseases on the cows' reproductive performance and risk for culling.     

The consequences of risk-based surveillance: Developing output-based standards for surveillance to demonstrate freedom from disease

Risk factors associated with high or low long-term incidence of displaced abomasum (DA) or clinical ketosis were studied in 60 Swedish dairy herds, using multivariable logistic regression modelling. Forty high-incidence herds were included as cases and 20 low-incidence herds as controls. Incidence rates were calculated based on veterinary records of clinical diagnoses. During the 3-year period preceding the herd classification, herds with a high incidence had a disease incidence of DA or clinical ketosis above the 3rd quartile in a national database for disease recordings. Control herds had no cows with DA or clinical ketosis. All herds were visited during the housing period and herdsmen were interviewed about management routines, housing, feeding, milk yield, and herd health. Target groups were heifers in late gestation, dry cows, and cows in early lactation. Univariable logistic regression was used to screen for factors associated with being a high-incidence herd. A multivariable logistic regression model was built using stepwise regression. A higher maximum daily milk yield in multiparous cows and a large herd size (p = 0.054 and p = 0.066, respectively) tended to be associated with being a high-incidence herd. Not cleaning the heifer feeding platform daily increased the odds of having a high-incidence herd twelvefold (p < 0.01). Keeping cows in only one group in the dry period increased the odds of having a high incidence herd eightfold (p = 0.03). Herd size was confounded with housing system. Housing system was therefore added to the final logistic regression model. In conclusion, a large herd size, a high maximum daily milk yield, keeping dry cows in one group, and not cleaning the feeding platform daily appear to be important risk factors for a high incidence of DA or clinical ketosis in Swedish dairy herds. These results confirm the importance of housing, management and feeding in the prevention of metabolic disorders in dairy cows around parturition and in early lactation.     

饲料中添加康贝对荷斯坦乳牛产奶量及乳成分的影响

奶牛日粮添加13克高活性康贝，试验组的产奶量比对照组提高1．78千克（P＜0．05）；添加20克，增幅达2．74千克（P＜0．01），乳脂量比对照组高9．88％（P＜0．05），牛奶中体细胞数低于13克组和对照组（P＜0．05）。大群饲喂20克康贝的生产试验也获得了 相似的结果。     

苹果发酵物对奶牛产奶性能和疾病的影响

将有益微生物接种到以苹果渣为主的培养基中进行有氧和无氧培养,制成颗粒状苹果培养物。对高产奶牛进行饲喂试验表明,用苹果发酵物代替等量的甜菜或苹果发酵物和甜菜粕同时使用,奶牛分别增产鲜奶1.89和1.90千克/头·日,同时乳脂、乳蛋白质、乳固体物都有上升趋势,奶牛发病率明显下降。苹果发酵物是一种新型反刍动物饲料。     

Mycoplasmal mastitis in dairy herds.

Mycoplasmal bovine mastitis is potentially a highly contagious disease that can cause severe economic problems in affected herds. The purchase of replacement heifers and cows are frequently the origin of mycoplasmal mastitis outbreaks in previously Mycoplasma-free herds. Purchased cows and heifers should be quarantined and tested for mycoplasmal mastitis before admission to the regular herd. Detection of Mycoplasma-infected cows by culture of milk is straightforward, although there are problems of sensitivity for its detection in milk samples that are inherent to the nature of the disease and laboratory procedures. After detection of infected cows, the best way to protect the herd is to culture all cows in the herd, cows with clinical mastitis, and all heifers and cows after calving and before entering the milking herd. Control of mycoplasmal mastitis requires test and culling from the herd of Mycoplasma-positive cows if possible. When a large number of cows are infected, strict segregation with adequate management is an option; however, animals in this group should never re-enter the Mycoplama-free herd. The functioning of the milking equipment and milking procedures should be evaluated carefully and any flaws corrected. There is no treatment for mycoplasmal mastitis, and vaccination has not proven to be efficacious to prevent, decrease the incidence, or ameliorate the clinical signs of mycoplasmal mastitis. Waste milk should not be fed to calves without pasteurization. M bovis may cause several other pathologies in animals of different ages on a farm, including pneumonia, arthritis, and ear infections. The survival of mycoplasmas in different farm microenvironments needs to be further investigated for its impact on the epidemiology of the disease.     

饲料中添加康贝对荷斯坦乳牛产奶量及乳成分的影响

在高产奶牛日粮中添加13克高活性康贝试验组的产奶量比对照组提高1．78千克（P＜0．05），当添加量达到20克时，增加达2．74千克（P＜0．05），乳胆量也显著比对照组高9．88％（P＜0．05），而且牛奶中的体细胞数也显著低于13克组和对照组（P＜0．05）。大群饲喂20克康贝的生产试验也获得了相似的结果。     

奶牛对蛋氨酸锌的表观吸收率

本试验用粪分析法对蛋氨酸锌饲喂奶牛的表现吸收率进行了测试。试验分３组，每组同质奶牛４头，３组分别在饲料中按日粮加入６ｍｇ／ｋｇ、２０ｍｇ／ｋｇ、６０ｍｇ／ｋｇ锌含量的蛋氨酸锌。试验结果，３组奶牛的表观吸收率依次为８５．０２％、７３．２９％、６４．６６％。结果表明奶中锌不能和蛋氨酸锌的添加量成比例地增长，饲料中锌的食入量较低，奶中锌的表观吸收率较高。饲料中蛋氨酸锌的添加量以２０ｍｇ／ｋｇ左右为宜。这项研究结果为奶牛饲喂蛋氨酸锌制取高锌奶提供了依据。     

Comparison of economically optimized culling recommendations and actual culling decisions of Finnish Ayrshire cows

Our purpose was to compare culling recommendations obtained from an economic-optimization model with actual culling of Finnish Ayrshire cows. The dynamic-programming (DP) model we used optimizes replacement and breeding decisions to maximize the net revenues from cows currently in a herd and their potential replacements over a 5-year decision horizon. Cows were described in the model by five state variables: parity, stage of lactation, month of calving, milk-production level, and days open (pregnancy status). We performed survival analysis to study the effects of those five factors on culling and to compare the actual culling of cows in December 1993 and June 1994 with the optimized replacement recommendations for the same months and for cows in the same herds.The risk of culling increased as a cow grew older, both in the actual herds and in the DP recommendations for December. In the optimized replacements for June, however, the age of a cow did not play a significant role. A cow that had been in milk > 270 days had a lower risk of culling than cows in earlier stages of lactation. When 305-day milk production increased by 100 kg, the risk of culling decreased by 4% in the actual herds and by 6 and 12% in the DP recommendations for June and December, respectively. When the days open lengthened by a month, the risk of culling was 2.0- and 1.6-times higher in the actual herds and 1.7- and 2.0-times higher in the DP recommendations for June and December, respectively. Month of calving had a different effect in the optimized recommendations compared with the real-life situation: cows calving from January to August had a lower risk of culling than cows calving in the fall in the actual herds, but the optimization model recommended heavier culling for cows calving between January and August.The DP did not account for diseases and did not allow replacements during the first 2 months of lactation and some of the observed differences could be due to this. However, the results suggested that Finnish farmers might not be taking full advantage of the seasonality in milk pricing and production to maximize the profits of their herds--even though their culling decisions are rational and in quite close agreement with the optimized recommendations.     

繁奶康对奶牛泌乳早期泌乳性能及血液指标的影响

选择20头荷斯坦高产牛,采用配对分组设计分为对照组和试验组,每组各10头。对照组使用原日粮,试验组产前21d每天在日粮中添加繁奶康125g,于分娩当天添加量增至300g直到试验结束,以探讨日粮添加繁奶康对奶牛泌乳早期产奶性能(产奶量及乳品质)的影响。结果表明,补充繁奶康,产奶量、乳脂校正乳产量试验组明显高于对照组(P0.05);奶牛采食量、乳脂率、乳蛋白率、乳糖率及乳干物质含量两组间差异不显著(P0.05)。血液指标谷草转氨酶、谷丙转氨酶活性两组间无显著差异(P0.05),高产奶牛补充繁奶康对泌乳早期产奶性能有较好的改善作用。