The contribution of mammary infections by coagulase-negative staphylococci to the herd bulk milk somatic cell count

Quarter foremilk samples were taken at 2–3 weekly intervals for several years in a experimental herd comprising about 45 cows. The samples were submitted to bacteriological analysis and somatic cell counting. The most prevalent quarter infections from 1982 to 1988 were by coagulase-negative staphylococci (15–20% of all the quarters sampled). Most of these (75.6%) persisted until drying-off Dry cow therapy eliminated 86.5% of these infections. Comparison of udder quarters within cows, involving 775 samples from pairs of non-infected quarters and quarters infected by coagulase-negative staphylococci, yielded geometric means of somatic cell counts of 210 000 and 420 000 cells/ml, respectively. The correlation (r=0.87) between the herd bulk milk somatic cell count (SCC) and its estimation from the quarter milk somatic cell count performed on the same day allowed us to evaluate the contribution of the different categories of quarters, according to their infection status, to the herd bulk milk SCC. Quarters infected by a major pathogen (8.5% of samples) gave rise to 46.6% of the total number of cells, while quarters infected by coagulase-negative staphylococci (17.8% of samples) gave rise to 18.1%. Although coagulase-negative staphylococci represented only a secondary source of somatic cells as compared to major pathogens, they were not a negligible source considering the threshold of 300 000 somatic cells advocated for herd milk of good quality.     

Calving patterns in seasonal dairy herds

Two field studies examined the calving patterns of cows in seasonal dairy herds in the Waikato (Field Study 1) and South Taranaki regions (Field Study 2). The first study examined patterns for cows commencing their second or subsequent lactation in herds which had used an inseminating service during the previous season. The second study included first lactation heifers only in 15 herds where animals had been naturally mated, and in 15 herds in which they had been synchronised and then artificially inseminated at the synchronised oestrus. The parameters describing calving patterns were based on the date for each herd's planned start of calving (PSC), which was 282 days from the date on which breeding commenced in the preceding season. The average interval from PSC to mean calving date for the 35 herds in Field Study 1 was 22 days, with individual herds ranging from 15 to 30 days. In herds with heifers which had been naturally mated (Field Study 2), it was 17.6 days compared to 11.0 days for previously synchronised animals. Calculating the intervals from PSC to median calving date and separately for the last two quartiles more effectively described a herd's calving pattern. The duration for the last quartile of the calving pattern was influenced by the extent and timing of induced calving. In Field Study 1, 88.6% of the 35 herd owners induced premature parturition in at least one cow. In these herds, 11.3% of cows were treated and calved prematurely. Only 61.7% of heifers which had previously been naturally mated calved by 3 weeks after PSC. Their calving dates were not evenly distributed over this 3-week period, with 9.8% in the first week and 25.6% in the third week. The calving pattern for heifers which had been previously synchronised showed several distinct peaks. Calvings to the synchronised mating were completed 15 days after PSC, by which time 64.7% of animals had calved. By 3 weeks after PSC, 72.9% of these heifers had calved. The results showed that there was considerable variation in calving patterns in seasonal dairy herds. This variation would have been due to differences in conception pattern, and the way induced calving had been applied. The calving pattern in heifers which had been naturally mated was less concentrated than had been expected. Synchronisation can significantly concentrate the calving pattern of these first lactation animals. The parameters used to describe calving patterns may be less applicable in herds in which a high proportion of animals is induced to calve prematurely, or where a whole herd is synchronised. Nonetheless, they do serve as an illustrative example of the variation in calving patterns among herds.     

Presence of Theileria annulata in Mauritania

A fatal case of bovine theileriosis by Theileria annulata is reported from Mauritania in a Friesian cow born in a dairy farm in Nouakchott. The farm was originally established with cattle imported from France. Specific diagnosis was based on piroplasm morphology and on high specific antibody titres in some of the animals. The only tick found in the herd was Hyalomma dromedarii. Four of 49 local zebus sampled at random in the south of the country had high specific antibody titres to T. annulata, while 14 had lower or doubtful titres. The infection therefore appears to be autochthonous.     

Effects of altering the grain content of sorghum silage on its nutritive value

The effects of increasing grain content of sorghum silage at the soft dough or the mature stages on nutrient digestibility, rate of passage and ruminal characteristics were investigated. A hetero-yellow grain sorghum (WAC 710DR) was harvested at the soft dough and the mature stage. Conventional sorghum silage was harvested by harvesting only the material more than 12 cm above the ground, high-energy silage by cutting it at a 40-cm height and headchop by harvesting at a 65-cm height. Regular silage was supplemented with either 17% or 34% grain to provide amounts of grain equal to that in the high-energy silage and headchop; high-energy silage was supplemented with 25% grain to equal the grain content of headchop. Diets were supplemented to 11.0% CP with soybean meal. Grain content was greater for headchop than for regular silage (72% vs 53%) but DM yield was lower (2,900 vs 4,600 kg/ha). Silages harvested at the more mature stage had lower digestibility of DM (62 vs 68%), CP (60 vs 64%), NDF (46 vs 50%), ADF (48 vs 52%) and starch (89 vs 97%). Increasing the height of cut did not increase DM digestibility of the silage. Compared with conventional silage, headchop had depressed NDF (43 vs 51%) and ADF (46 vs 55%) digestibility. Supplementation of silages with grain did not increase digestibility. The failure to increase DM digestibility was not due to depressed fiber or starch digestion, but rather to an increased fecal excretion of cell contents. The digestibility of grain sorghum silage was not improved by increasing the height of cut or adding supplemental grain.     

Correlation between thyroid hormone level and blood pH in cows and in their offspring

Thyroid hormone levels in the plasma and blood pH were compared in 38 newborn calves and their dams immediately at parturition, then 24 and 72 h thereafter. Both thyroid hormone levels and pH exhibit much higher variation in calves than in cows. Applying a linear model at different sampling times, a weak (r = -0.112 to -0.397) but significant (P less than 0.05) negative correlation was found between thyroid hormone levels and blood pH in calves 24 and 72 h postpartum. At birth, when no correlation was found with linear approach, a polynomial regression model showed curvilinear relationship between thyroid hormone levels and blood pH in calves. Since these correlations could not be substantiated by comparing data of different sampling times, one can conclude that the possible relationship of thyroid hormone levels and blood pH is a complex one. Revealing the underlying mechanism of the above observations requires further study.     

Monoclonal antibodies to Chlamydia psittaci guinea pig inclusion conjunctivitis (GPIC) strain

Monoclonal antibodies to a strain of Chlamydia psittaci isolated from guinea pig inclusion conjunctivitis (GPIC) were developed. Only five of the 15 hybridomas isolated produced antibodies specific for the GPIC strain, while seven others produced antibodies which cross reacted with other strains and another species. Strain-specific and species-specific monoclonal antibodies were isotyped as IgG2a and IgG3, respectively. It appears that the GPIC strain has at least two epitopes, one of which is specific for the strain and the other common to the species. These monoclonal reagents may be used to immunotype GPIC agents, better than available methods and may be of potential use in the development of vaccines against chlamydial infections.     

Medical dissolution and prevention of canine and feline uroliths: diagnostic and therapeutic caveats

Medical protocols designed to promote the dissolution of canine and feline struvite uroliths, the dissolution of canine ammonium urate and cystine uroliths and the prevention of all major types of canine and feline uroliths have been developed. However, because the causes of different types of uroliths vary, the medical protocols for their dissolution and prevention also vary. When the diagnosis of the underlying causes of uroliths becomes the rule rather than the exception, therapeutic failures should become the exception rather than the rule.     

Changes in hormonal profiles during the estrous cycle in old lactating beef cows

Patterns of concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), progesterone (P4) and estradiol-17 beta (E2) during an estrous cycle were compared between 15 lactating beef cows 5 to 7 years of age (young) and 15 cows greater than or equal to 12 years of age (old). Length of estrous cycle did not differ between young and old cows (P = .06). No differences due to age were found for LH. Patterns of concentrations of P4 during the first 15 days of the cycle, of FSH during days 6 through 12 and of E2 during the follicular phase differed with age (P less than .05). An earlier (P less than .025) midcycle elevation of FSH was associated with an earlier rise and greater concentration of E2 (P less than .05) during the follicular phase in old than in young cows. Differences in FSH and P4, although subtle, were consistent with an earlier or more advanced follicular development in old cows, leading to greater secretion of E2 from the preovulatory follicle.