Estrus-related odors in body fluids of dairy cows.

Six experiments were to test for estrus-associated odors in 1) swabs of the vulva and vestibule, 2) fluids from deep in the vagina, 3) naturally voided urine, 4) urine obtained from the bladder by catheter, 5) milk, and 6) blood plasma. Tests were with dogs trained to identify vaginal fluids from estrous cows. In the tests, dogs were walked along lines of seven sample bottles consisting of samples from two estrous cows, two luteal-phase cows, one vaginal swab from estrous cows used as a standard, and two blank sample bottles. Correct responses to fluids from estrous cows averaged 97, 86, 96, 97, 99, and 94% for the six fluids listed. Incorrect responses to fluids from luteal-phase cows were 2, 1, 1, 1, 1, and 8%. Responses to blank samples were usually zero. Results indicate that odors associated with estrus are spread throughout the cow's body fluid.

Estrus-related odors in milk detected by trained dogs.

Dogs trained to identify vaginal mucus samples and other fluids from estrous cows were used for further studies of estrus-related odors in milk. In the first experiment, milk was collected from 10 cows during estrus and luteal phase of the estrous cycle and tested in trials of 9 samples each; 1 or 2 of the samples were from estrous cows. Dogs responded to milk from estrous cows in 76% of the exposures to such samples with significant differences among cows and significant improvement by the dogs during the experiment. Responses to milk from luteal-phase cows, averaged 6%. In a second experiment, milk was frozen and thawed four times without decreasing the frequency of response to samples from estrous cows. In the third and fourth experiments, milk was collected from four cows on several days of the estrous cycle. After the dogs were trained to respond to milk from pre-estrous cows (1 or 2 days before estrus), they responded to 64% of these samples; after the dogs were retrained to not respond to milk from pre-estrous cows, they responded 21% of the time to milk obtained 1 to 3 days before estrus. In these two experiments, responses to milk from estrous cows averaged 83% and to milk from luteal-phase cows, 8%. Trained dogs can distinguish milk of pre-estrous cows from milk of either estrous or luteal-phase cows.

Hormonal patterns during heat stress following PGF(2)alpha-tham salt induced luteal regression in heifers.

Ten, normally cycling, Holstein heifers were assigned to one of two environmental treatment groups (21.3 C, 59% RH or 32.0 C, 67% RH). PGF(2)alpha was used to induce luteal regression and synchronize estrus in order to evaluate temperature effects on various hormonal and physiological responses during the proestrous through metestrous periods. Environmental temperature (32.0 C) evoked a 1.4 C increase in rectal temperature and a 3.6 C increase in skin temperatures. Length of estrus was shorter (P<.10) for heifers at 32.0 C (16 vs 21 hr.). Average plasma progestin concentration between treatments was not different (P>.10). Mean estradiol concentrations were significantly (P<.10) lower in heifers at 32.0 C. No differences (P>.10) were detected in mean concentrations of LH between heifers at 21.3 C and 32.0 C. Preovulatory peak LH concentrations were 32.2 and 33.2 ng/ml plasma, respectively. All animals had a preovulatory surge of LH, suggesting that hyperthermia did not alter factors which regulate hypothalamic control of LH release. Mean basal concentrations of prolactin and corticoids were not different between temperature treatments (P>.10). However, mean corticoid response following ACTH was of lower magnitude, earlier to peak, and of shorter duration in heat stressed heifers. Heat stress did not appear to affect the hormonal milieu in peripheral plasma associated with corpus luteum regression (decrease in progestin) and ovulation (LH surge). However, duration of estrus, concentrations of estradiol at proestrus and corticoid response to injection of ACTH were reduced.

Estrus-related odors in cows: time of occurrence.

One Catahoula Leopard Cowdog and three German Shepherd dogs, previously trained to detect odors characteristic of estrus in cows, were used in three experiments to determine when estrus-related odor first appears, how long it persists, and when it disappears in relation to time of estrus. Samples were swabs of reproductive tract fluids taken from vaginas of cycling cows on the day of estrus, at diestrus (8 to 10 days after estrus), and at daily intervals before and after estrus. Estrous odor emerges slowly during the 3 days before estrus, reaches a definite peak in intensity on the day of estrus, and disappears within 1 day thereafter.

Genetic polymorphisms of blood and milk and reproduction in Holstein cattle.

Associations of blood and milk protein polymorphisms with reproductive performance were examined in more than 32,000 services in 15,000 service periods of 6,000 cows and 700 service sires in Holsteins. Seven blood groups, one serum protein, and four milk proteins were analyzed for relation to reproductive traits including conception rate and days open. Associations between polymorphic systems and reproductive traits in 15 of 112 analyses were significant. The S blood system appeared most influential, having statistical significance in five of ten traits. These were conception rates in all services for female phenotypes, male phenotypes, and male by female phenotypes combined, conception rate in first services for female phenotypes, and probability of conception for female phenotypes. The FV system influenced conception rates in all services and in first services for male by female phenotypes combined. Four of the polymorphic systems had no effect on any of the reproductive traits. Maternal-fetal incompatibility was not evident from comparing parental combinations of aborted fetuses and normal calves. Conception rates declined with age of cow. For animals that ultimately conceived, conception rates did not decline consistently from first to later services within a service period.

A review of research on genetic variation in physiological characteristics related to performance in dairy cattle.

Genetic influence on physiological characteristics ranges from single gene effects on amino acid substitutions in alternative forms of proteins to quantitative genetic effects on the amounts of enzymes and hormones. The number of loci involved in the control of quantitative variation in physiologically important substances is not known. A number of marker genes that affect blood antigens, serum and milk proteins, and enzymes have been identified in dairy cattle. However, relatively little is known about genetic effects on quantitative physiological traits in dairy cattle. Much more is known about the genetic control of hormones in laboratory animals. About 25% of the variation in milk production of dairy cows results from genetic differences. We need more studies of genetic influences on the various physiological and biochemical processes involved in the secretion of milk to reveal the mechanisms by which genetics influences the quantity and quality of milk produced by individual cows.

Variation in physical activity as an indication of estrus in dairy cows.

Pedometers were used to measure daily physical activity of cows to determine if variation related to estrus was great enough to be useful in estrus detection. Forty cows in free stalls and 28 cows in comfort stalls were studied during the breeding period after calving. Pedometers were enclosed in specially designed cases and attached to a cow's lower rear leg with a plastic ankle strap. Readings were taken twice daily when the cows were milked in a milking parlor. Data from free stalls were available for 5163 intervals between milkings, 87 of which were periods of estrus. Activity definitely increased at the time of estrus; cows were about four times as active during estrus as they were when not in estrus. Data from comfort stalls were available for 2433 intervals between milkings, 39 of which were periods of estrus. Cows in comfort stalls were about 2.75 times as active during estrus as when not in estrus. There was relatively little variation within cow in activity from day to day among cows not in estrus. Activity monitoring appears to have potential as an aid in estrus detection.

Responses of young calves to low doses of lead.

Twenty calves, week-old male Holsteins, 42.8 kg body weight, were assigned to four treatments by oral dose 0, 1.5, 3.0, and 6.0 mg lead carbonate/kg body weight given three times weekly until calf fetal hemoglobin had been converted to 100% adult hemoglobin for 2 consecutive wk. Analyses were for the first 7 wk when data were complete. Variables included lead in blood, body weight changes, erythrocyte delta-aminolevulinic acid dehydrase activity, packed cell volume, hemoglobin, conversion of fetal to adult hemoglobin, and erythrocyte 2,3-diphosphoglyceric acid. Early changes due to lead treatment were inhibition of delta-aminolevulinic acid dehydrase at all doses and increased loss of hemoglobin at 3.0 and 6.0 mg doses. Growth rate was not impaired seriously by lead treatment. The 2,3-diphosphoglyceric acid in erythrocytes reached peak value at 3 to 4 wk of age and then decreased with age, but 2,3-diphosphoglyceric acid of the treated calves was not changed by the low lead dosing. Low lead dosing will induce early metabolic changes in the young calf prior to inhibition of growth.

Quantitative changes associated with calving in the levels of bovine immunoglobulins in selected body fluids. I. Changes in the levels of IgA, IgGl and total protein.

Levels of bovine IgA, IgG1 and total protein (TP) were determined in serum, saliva, tears and individual quarter lacteal secretions of six Holstein-Friesian cows sampled from six weeks before to four weeks after parturition. Hierarchal analyses of variance indicated significant variations among weeks, cows and quarters of the udder. A precipitous but non proportional drop in the levels of IgA and IgA1 in lacteal secretions occurred at calving. There was a concomitant increase in IgG1, and decrease in IgA, in serum. Correlation studies supported the concept of selective transport of IgG1 from serum to lacteal secretions in regulated amounts independent of serum IgG1 levels. Changes in the IgG1/TP ratio of serum and lacteal secretions supported the idea of a decrease in the selective transport mechanism. Correlation studies and estimations of secretory IgA (SIgA) in serum suggest that serum IgA is derived from IgA synthesized in secretory tissues. Highly significant correlations between IgA and IgG1 levels in all secretions postpartum suggest that local IgA synthesis and either IgG1 transport or local IgG1 synthesis are initiated by the same stimuli. Although some of the variation in the level reported for IgA and IgG1 in secretions resulted from protein dilution, much of the variation represents physiological differences between individual animals and tissues in the same animal. An IgG2/IgG1 ratio approaching that of serum occurred in a mastitic quarter of one cow. IgA was the principal immunoglobulin in saliva and tears, comprised a greater proportion of the immunoglobulin in milk whey than in prepartum lacteal secretions and was a minor immunoglobulin in bovine serum.