Hypomagnesemia among cows in a confinement-housed dairy herd

Between January and March 2002, 55 cows in a 1,200-cow commercial dairy herd in south Florida died. Most of the cows that were found dead did not have any clinical signs of disease prior to death. Because of a history of a feed change, a bloom of blue-green algae in cow cooling ponds, and initial necropsy findings of moderate enteritis, the preliminary differential diagnosis included clostridial enteritis, blue-green algae toxicosis, and mycotoxicosis. Rumen acidosis, hypomagnesemia, and heavy metal toxicosis were included as secondary considerations. On the basis of physical examination and gross necropsy findings, results of clinicopathol ogic testing, and results of feed and water analyses, a diagnosis of hypomagnesemia was made. Control procedures that were implemented included changing the forage source and increasing the magnesium concentration in the diet.     

Prototheca zopfii mastitis in a herd of dairy cows

Mastitis caused by the colourless alga Prototheca zopfii was diagnosed in 17 of 120 cows in a dairy herd. Infection occurred in animals varying from 3-14 years old and was present in one to four quarters of each cow. Nine cases were associated with clinical mastitis characterised by the presence in milk of flakes or small clots. Somatic cell counts consistent with subclinical mastitis (>500 x 10(3) cells/ml) were recorded in five of the eight remaining cows. Histological examination of udder tissue showed the presence of granulomatous lesions associated with the presence of Prototheca. The problem was identified and controlled by repeated microbiological examination of milk samples from all lactating cows and immediate culling of infected animals. P. zopfii was also recovered from environmental water samples on this farm. It is suggested that infection may have occurred as a result of teat sores caused by trauma from a milking machine, and the tendency for cows to lay down on a race, the surface of which was sometimes flooded by drain water in which Prototheca were present.     

Prototheca zopfii mastitis in a herd of dairy cows

Mastitis caused by the colourless alga Prototheca zopfii was diagnosed in 17 of 120 cows in a dairy herd. Infection occurred in animals varying from 3–14 years old and was present in one to four quarters of each cow.

Nine cases were associated with clinical mastitis characterised by the presence in milk of flakes or small clots. Somatic cell counts consistent with subclinical mastitis (>500 × 10³ cells/ml) were recorded in five of the eight remaining cows.

Histological examination of udder tissue showed the presence of granulomatous lesions associated with the presence of Prototheca.

The problem was identified and controlled by repeated microbiological examination of milk samples from all lactating cows and immediate culling of infected animals.

P. zopfii was also recovered from environmental water samples on this farm. It is suggested that infection may have occurred as a result of teat sores caused by trauma from a milking machine, and the tendency for cows to lay down on a race, the surface of which was sometimes flooded by drain water in which Prototheca were present.     

Economic consequences of postponed first insemination of cows in a dairy cattle herd

The purpose was to analyse the economic consequences of postponed first insemination of cows in dairy herds with different reproduction management, and to analyse the sensitivity of the results to a further decrease in beef prices, using a model simulating production and health in a dairy cattle herd. Three different period-to-first-insemination scenarios were analysed. Period to first insemination was defined as days post partum for initiating insemination at observed heat. The three scenarios consisted of a short period to first insemination (70 days for primiparous and 35 days for older cows), a 70 days postponed first insemination of primiparous cows and a scenario with 70 days postponed first insemination for all cows. At a 70 days postponed first insemination for primiparous cows a decrease in annual herd profit of 1% were found. A 70 days postponed first insemination for all cows led to a decrease in annual herd profit by 3% at good reproductive efficiency and 4% at poor reproductive efficiency. The herd profit was calculated as the profit to cover labour costs and fixed costs. Postponed inseminations might reduce labour per cow-year. The reduction in labour per cow-year need to be 3.2 h at good reproductive efficiency and 4.3 h at poor reproductive efficiency to counterbalance the reduction in herd profit by postponing first insemination for all cows by 70 days. In a situation with a 50% decrease in beef prices in a herd constrained by a milk quota (optimising profit per kg milk) herd profit was increased by 0.8% at good reproductive efficiency and 0.3% at poor reproductive efficiency by postponing first insemination for all cows by 70 days.     

Competitive behaviour of dairy cows at a concentrate self-feeder

Abstract

We investigated whether feeding cows are disturbed by butting of other cows during the time they are in a concentrate self-feeder, and whether this leads to concentrate leftovers. Forty dairy cows were observed while visiting two self-feeders. If a cow was butted visiting the self-feeder, it was considered as ‘disturbed visit’. When retreating from the feeder within five seconds after being butted, the visit was also considered ‘interrupted’. Half of the visits were disturbed, and 42% of visits were also interrupted. Visits were disturbed particularly when cows’ own feed was dispensed, and in 63% of disturbed visits concentrates were left over. The non-lactating cows, denied concentrates, won leftover concentrates after butting the previous visitor more often than lactating cows. Cows’ weight correlated negatively with visiting and receiving butting. Initiated butting correlated positively with winning leftover concentrates. There is a need for further development of automatic feeders to secure individual concentrate feeding.     

Paratuberculosis vaccine in a large dairy herd.

On a 500-cow dairy farm a total of 866 young calves less than one month old were vaccinated with a heat-killed oil-adjuvated bacterin against Mycobacterium paratuberculosis over a period of five years. The vaccinated calves were tested by faecal microscopy, bacteriology and serology on the day of vaccination, at the age of 3, 6, 9 and 12 months, at breeding age, and on the day of calving. A total of 721 bull calves and 379 female calves served as unvaccinated controls in two groups. The results were evaluated by trend analyses. Vaccination greatly reduced the faecal shedding of mycobacteria as demonstrated by the annual faecal microscopic examinations. During the last 6 months of the experiment only 9 of 612 samples were found positive by microscopy and by bacterial culture. The number of seropositive animals and the antibody titres demonstrated by the complement fixation test (CFT) and agar gel immunodiffusion (AGID) increased during the first three years. Later on, both the number of seropositive animals and CFT titres decreased.     

Onion toxicosis in a herd of beef cows.

A herd consumed approximately 20 kg onions/cow/day for 6 weeks. Five cows died and two aborted. Onion toxicosis results in methemoglobinemia and hemolytic anemia. These changes can cause secondary organ damage and death, if enough onions are consumed.     

Measuring dairy herd fertility.

The use of the calving index as a measure of herd fertility ignores the proportion of the herd that is culled, generally for failing to conceive. It is more important to consider the total cost of long calving intervals, high culling rate and even low pregnancy rates in an integrated index that reflects inefficient management, than to have to cope with balancing a number of separate physical indicators. In a study of 91 herds containing 14,524 cows a full range of physical indices was examined. The average herd calving interval was 380.3 days, with a culling rate of 23.1 per cent. Of the cows calving, 76.9 per cent recalved, a figure which when adjusted for the calving interval (CIA calving rate) became 73.8 per cent. In quartiles split on the basis of CIA calving rate, the top quartile achieved 82 per cent with a calving index of 375.2, and a culling rate of 16.7 per cent. These standards were achieved by serving 91.9 per cent of the cows after calving, at an interval to first service of 67.2 days. The submission rate for artificial insemination in the first 24 days after the earliest service date was 57.5 per cent and the overall pregnancy rate was 51.2 per cent. As a result 92.1 per cent of the cows served, and 85.3 per cent of those which calved, conceived again, with an average of 1.9 services per conception. Assessing fertility on a financial basis, with costs attributed to calving interval, culling rate and pregnancy rate to give a fertility index, the average herd was losing pounds 62/cow/year, compared with target levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Monensin toxicosis in a dairy herd

An acute onset of illness was reported in a lactating dairy herd in Canada in which monensin had been incorporated in error in its ration at almost 10 times the prescribed level. All of the lactating cows became lethargic, were inappetant, developed diarrhea, and had decreased milk production from 28 kg/cow/day, the day before exposure, to 23 kg/cow/day, 3 d later. Within 9 d, all animals recovered from the incident and milk production returned to previous levels.     

Phosphorus deficiency in a dairy herd

Phosphorus deficiency was diagnosed in a 90 cow seasonal supply dairy herd which showed low milk production, ill-thrift, infertility and osteophagia. Serum inorganic phosphorus and pasture phosphorus levels were low, pasture Ca:P ratios high and soil phosphorus levels very low; the soil phosphate retention value was 96%. The deficiency, which had probably existed for several years, was considered to be due to inadequate annual phosphate fertiliser applications on a high phosphate retaining soil. Phosphorus deficiency may have been exacerbated by the application of lime without phosphate several months before the onset of severe clinical disease. The finding of low sodium levels in pasture samples suggested that sodium deficiency may have co-existed and contributed to the clinical picture. Treatment, comprising bone flour dusting of pasture, water trough supplementation and phosphorus-containing injections, appeared to induce ovarian activity in anoestrous cows and suppress osteophagia, though controlled treatment trials were not performed. No improvement was noted in milk production or cow condition. Increased annual super-phosphate and reduced potassium applications were recommended, together with the monitoring of pasture and soil macro elements and serum phosphorus levels. A decision on whether to supplement with sodium would be based on the results of pasture monitoring, since a direct animal test is not currently available. It is suggested that phosphorus deficiency may not be uncommon in dairy herds in some North Island districts; based on the present case, the decline in New Zealand superphosphate quality in the 1970's and recently published data which has shown a high proportion of pasture phosphorus deficient sites in some North Island areas.     

Terbufos poisoning in a dairy herd

This report describes the accidental poisoning of over 200 head of Holstein cattle by the organophosphate, terbufos. The ingestion of an acutely toxic dose (approximately 7.5 mg/kg) of terbufos by 84 heifers resulted in severe respiratory distress as the primary clinical sign and death within 12 hours. There was no response to treatment with atropine sulfate. One hundred and twenty milking cows received a portion of the contaminated feed diluted approximately ten times. These cattle had typical signs of organophosphate poisoning and responded to atropine sulfate. Severely affected cows received pralidoxime chloride and activated carbon 48 h after terbufos ingestion but did not respond to the drugs. Diagnosis of organophosphate poisoning was confirmed by tissue and feed analysis for terbufos and measurement of whole blood cholinesterase activity.     

Mycoplasmal mastitis in a dairy herd

In October 1985, mycoplasmas were isolated from bulk tank milk samples in a large Florida dairy (greater than 1,400 lactating cows). At that time, measures to isolate and control the spread of infection were instituted. In an initial screening test, Mycoplasma bovis was isolated from 21 of 153 milking string samples (milk from all quarters of 10 cows/string). Composite quarter milk samples from all quarters of every individual lactating cow in the herd were obtained for culture in November 1985 and December 1985. In October, 88 of 1,535 (5.7%) cows were identified as Mycoplasma-positive. An additional 31 Mycoplasma-infected cows were identified in December. The dairy elected to maintain the infected cows in a separate Mycoplasma-positive subherd, which would be milked at the end of each milking session. Seven additional Mycoplasma-positive cows were identified at initiation of lactation. All newly identified infected cows were transferred to the Mycoplasma-positive subherd. After segregation of Mycoplasma-positive cows, bulk tank milk samples obtained routinely from the main herd remained culture negative throughout the study. From February 1986 to October 1986, quarter milk samples were obtained monthly from cows in the Mycoplasma-positive subherd. Any cow that developed clinical mastitis or substantial decrease in milk production was, at the discretion of the herdsman, culled. Of the 126 cows in the subherd, 22 (17.5%) were culled for mastitis, 35 (27.8%) were culled for low production, and 9 (7.1%) were culled for other reasons. Of the remaining 60 cows, 16 (12.7% of the 126 cows) were Mycoplasma-positive on the basis of results from one or more samples obtained after February 1986.(ABSTRACT TRUNCATED AT 250 WORDS)