RESUMEN Este estudio fue realizado para hallar la influencia estacional sobre la incidencia de la... more RESUMEN Este estudio fue realizado para hallar la influencia estacional sobre la incidencia de la mastitis a lo largo del año, en vacas indígenas, vacas cruzadas y búfalas Murrah. Se analizaron los registros de lactación correspondientes a un periodo de 12 años, la incidencia de mastitis fue comparada con los climogramas de la zona de Karnal, Haryana, India. El clima cálido y húmedo afectó negativamente a la incidencia de mastitis en todas las razas bovinas y los búfalos. La incidencia fue afectada significativamente por la estación (p<0,01) en todas las razas, aunque el efecto fue menor en las búfalas Murrah. El registro de mastitis fue más elevado en las razas Sahiwal y Tharparkar (p<0,01) que en los cruces Karan-Suiza y Karan-Fries. El incremento del índice de temperatura y humedad dio lugar a una mayor incidencia de mastitis en las vacas (p<0,01), aunque las búfalas Murrah resultaron menos afectadas.
Objectives were to detennine 1) in vitro effects of bST on function of polymorphonuclear leukocyt... more Objectives were to detennine 1) in vitro effects of bST on function of polymorphonuclear leukocytes and lymphocytes and 2} in vivo effects of bST on leukocyte function of heifers fed to maintain medium or high growth rates. When administered in vitro, bST did not affect function of polymorphonuclear leukocytes. [Methyl-3H]thymidine incorporation by resting lymphocytes was stimulated by 1000 ng/ml bST. When given in vitro, bST did not further enhance [methyl-3H]thymidine uptake by mitogen-stimulated lymphocytes cultured at 38SC but reduced the depression of mitogen-stimulated proliferation caused by incubating cells at 42"C. When bST was administered in vivo, phagocytosis and killing of Escherichia coli by polymorphonuclear leukocytes from bSTtreated heifers were not different from cells of control heifers. As measured by [methyl-3H]thymidine uptake after stimulation with phytohemagglutinin, lymphocytes from bST-treated heifers responded similarly to those of control heifers when incubated at 38.5"C, but the depression in [methyl-3H]thymidine uptake due to culture at 42-C was less for lymphocytes obtained from bST-treated
The fate of the newly formed embryo is an uncertain one. It is estimated that about 50% of human ... more The fate of the newly formed embryo is an uncertain one. It is estimated that about 50% of human embryos are lost before implantation. 1 In dairy cattle, pregnancy rate (the proportion of cows that are inseminated that are diagnosed pregnant) has been decreasing over the last 30 years. Pregnancy rates of 50-60% in the 1970s have declined to values of 35-45% today. 2,3 The mechanisms mediating embryo survival and death are incompletely understood. Recently, studies in cattle have led to the emergence of the idea that infectious disease outside the reproductive tract can lead to reduced pregnancy rate. Such observations are suggestive that inflammatory or immune responses associated with infectious disease can cause anovulation,
A 42-mo field trial was initiated in 65 New York Dairy Herd Improvement herds to evaluate the eff... more A 42-mo field trial was initiated in 65 New York Dairy Herd Improvement herds to evaluate the effects of length of dry period on disorders at calving and subsequent milk production. Common disorders and udder edema at parturition were not associated with the length of the preceding dry period. Cows were assigned to treatment group dry periods of 20, 30, 40, 50, and 60 days by modulus 5 of their index numbers. Cows which averaged 10 to 40 days dry produced from 450 to 680 kg less milk in the following lactation than cows with average dry periods of 40 days or longer. Although there was some gain in milk production during the previous lactation from the longer lactationshorter dry periods, it was less than half the loss in the following lactation. The depressing effect of the short dry periods did not carry over to the second lactation. Cows with dry periods of 40 ___ 10 days produced as much as .cows with 50 days dry or more.
... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,'... more ... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,' WG MERRILL, ~ SJ ROBERTS,* and GH SCHMIDT ~ Department of Animal Science 3 and College of Veterinary Medicine 4, Cornell University, ithaca, New York 14850 Abstract A ...
... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,'... more ... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,' WG MERRILL, ~ SJ ROBERTS,* and GH SCHMIDT ~ Department of Animal Science 3 and College of Veterinary Medicine 4, Cornell University, ithaca, New York 14850 Abstract A ...
SummaryThe effect of errors that occur in the diagnosis of intramammary infectious mastitis on th... more SummaryThe effect of errors that occur in the diagnosis of intramammary infectious mastitis on the precision of experiments measuring the efficacy of mastitis therapy has been investigated. Diagnostic errors within the range found by experienced workers can create large biases in the apparent cure rate of therapy particularly at cure rates of less than 0·5. Using confirmed methods of diagnosis rather than single samples and reducing the probabilities of false positive and false negative diagnoses to 0·01 and 0·05 respectively, the biases in the apparent cure rates are reduced to acceptable levels. A method is given for calculating the rates of occurrence of false positive and false negative diagnoses from the results of trials using confirmed diagnoses. These errors cannot be calculated from therapy trial data when diagnosis is based on single milk samples.Because the bias in the measurements of the cure rate is greatest at the lowest levels of elimination, estimates of spontaneous ...
Mastitis is the most costly disease in dairy herds when adequate control procedures are not used.... more Mastitis is the most costly disease in dairy herds when adequate control procedures are not used. A single quarter infected for one lactation may reduce milk production of that cow 10 to 12% in that lactation (25). Additional costs of discarded milk, antibiotics, and culling increase the cost in an average herd to the dollar equivalent of approximately 700 kg
Lactating dairy cows (487) from five commercial herds were in a study of benefits from lactation ... more Lactating dairy cows (487) from five commercial herds were in a study of benefits from lactation therapy of subclinical mastitis. Bacterial isolations and composite milk samples for somatic cell counts were taken from each cow each month for 15 mo. Cows (254) in the experimental ...
Journal of the American Veterinary Medical Association, Jan 15, 1977
The primary sources of mastitis pathogens are infected quarters, chapped, sore, or eroded teat en... more The primary sources of mastitis pathogens are infected quarters, chapped, sore, or eroded teat ends, and the environment. The major means of transfer of the most predominant mastitis pathogens is the milking routine. Methods are available to reduce the number of organisms normally transferred during each of the procedures. However, with the exception of teat cup pasteurization, the application of hygienic procedures in herds where teat dipping is practiced did not result in additional beneficial effects. Effectiveness of 4% chlorine, 0.5 and 1% iodine, and 0.5% chlorhexidine teat dips has been demonstrated in field trials and should be the preferred products in a mastitis control program. Most gram-negative organisms get on teats by direct contact with the bedding. In herds with clinical coliform mastitis, changing the bedding material has been associated with fewer clinical mastitis cases.
Changes in the calcium and phosphorus requirements of the dairy cow at parturition with particula... more Changes in the calcium and phosphorus requirements of the dairy cow at parturition with particular reference to the amounts supplied to the foetus in utero.
Somatic cells were counted and bacteria identified for milk samples from 719 lactating dairy cows... more Somatic cells were counted and bacteria identified for milk samples from 719 lactating dairy cows in 12 commercial herds. These pooled data were used to look at the accuracy of alternative thresholds of somatic cell counts as indicators of intramammary infection. Sensitivity, specificity, and predictability positive and negative at alternative cell count thresholds were calculated. There was an increase of incidence of infection associated with increased cell count. Raising the cell count threshold increased predictability positive and specificity and decreased sensitivity and predictability negative. Also, the effect of prevalence of infection on predictabilities was examined for the pooled data on sensitivity and specificity at a cell count threshold of 400,000 cells/ml. As prevalence of infection increased, predictability of a positive test result also increased, but predictability negative decreased. Differences in accuracy of somatic cell count as a predictor of infection at varying prevalences of infection suggest that test results should be interpreted for individual herds.
Milk cortisol and prolactin concentrations were measured in 12 lactating Holstein cows for 3 days... more Milk cortisol and prolactin concentrations were measured in 12 lactating Holstein cows for 3 days (Experiment 1). On day 3, cows were divided randomly into groups: IV1, IV4, IM, and control. Group IV1 received one intravenous injection of 49 IU adrenocorticotropin, group IV4 the same dosage four times at 2-h intervals, group IM 240 IU adrenocorticotropin intramuscularly, and control cows were injected with saline. Cortisol concentrations in blood plasma were increased in all groups following adrenocorticotropin injection, while milk cortisol concentrations increased fourfold in groups IV4 and IM and remained unchanged in group IV1. In Experiment 2, infusion of 18% saline into the mammary gland of three cows increased the somatic cell count in the infused quarter but had no effect on prolactin and cortisol of milk or plasma. In Experiment 3, six cows each were assigned to treatment groups of saline controls, IV2-0 (40 IU adrenocorticotropin intravenously at 0 and 2 h post-milking) or IV2-8 (40 IU adrenocorticotropin intravenously at 8 and 10 h post-milking). Half udders of each cow were milked before treatment and 4 h later. Increases of cortisol in plasma increased cortisol concentrations of milk 4 h after each treatment (IV2-0 and IV2-8). However, by 12 h after treatment in IV2-0 cortisol concentrations of milk had returned to normal. Increases in adrenal cortisol secretion are followed rapidly (within 4 h) by increased cortisol concentrations in milk. However, these decline rapidly in the absence of sustained increments in blood cortisol. Increased cortisol concentrations in milk most likely represent sustained elevation in plasma cortisol.
Cortisol concentrations in milk and blood plasma were measured in 12 lactating Holstein cows foll... more Cortisol concentrations in milk and blood plasma were measured in 12 lactating Holstein cows following administration of 40 IU adrenocorticotropin intravenously (groups 1 and 2) or 4 ml saline (control). Blood and milk samples were collected at 15 or 30-min intervals for 4 h from control and group 1 cows and at hourly intervals for 4 h from group 2. Cortisol concentrations in plasma and milk were increased 15 min after treatment and peaked by 1 h in group 1 but remained unchanged in controls. Group 2 cows were sampled less frequently but showed a pattern for plasma and milk cortisol concentrations similar to group 1. The profile of increased cortisol concentrations and of their decline 1 to 2 h later was similar for plasma and milk. These results suggest that cortisol concentrations in milk reliably indicate cortisol concentrations in blood and may be valuable in monitoring stress in dairy cows, depending upon duration of stress and its timing relative to milk removal.
Six commercial dairy herds were used to test the relative efficacy of three concentrations of iod... more Six commercial dairy herds were used to test the relative efficacy of three concentrations of iodine as a teat dip over 12 too. Concentrations were .1, .25, and 1% iodine with free iodine contents of 3.5, 4.0, and 1.0 ppm. Two concentrations were compared in each herd. The greatest number of new infections (71) occurred in approximately 120 cows whose teats were dipped with the 1% iodine dip, and the fewest (52) occurred in a similar number of cow quarters dipped in .1% iodine; however, differences were not significant. Clinical mastitis was highest in the 1% group. If all clinical mastitis were the result of infection, even if bacteria were not isolated from the pretreatment sample or from samples collected at the start of the study and those quarters were added to the totals, then reduction of new infection with the .1% product would be significant.
Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial t... more Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial to evaluate effects of daily subcutaneous injections of 0 (A), 5.15 (B), 10.3 (C), and 20.6 mg (D) of recombinantly derived bovine somatotropin monomer. Responses were milk yield and composition, component yields, net energy intake, body weight, and somatic cell counts. Treatments began in fall, 28 to 35 d postpartum, and continued for 266 d. Base ration was corn silage and concentrate. Least squares means of milk and constituent yields and gross efficiency of milk production differed among treatments, but percentage fat and protein, energy intake, body weights, and somatic cell counts did not. Least squares means of 3.5% FCM were 21.3 (A), 25.0 (B), 26.2 (C), and 28.5 kg/d (D); fat and protein yields showed similar response to treatment. Milk yields adjusted for pretreatment yields were 21.1 (A), 25.5 (B), 26.5 (C), and 29.3 kg/d (D). Orthogonal contrasts showed lower milk and constituent yields and net energy intake for control (A) than for hormone-injected cows (B, C, D), but no differences were detected between treatments B, C, and D. Gross efficiency of production (3.5% FCM/feed net energy intake) was greater for hormone-injected cows.
RESUMEN Este estudio fue realizado para hallar la influencia estacional sobre la incidencia de la... more RESUMEN Este estudio fue realizado para hallar la influencia estacional sobre la incidencia de la mastitis a lo largo del año, en vacas indígenas, vacas cruzadas y búfalas Murrah. Se analizaron los registros de lactación correspondientes a un periodo de 12 años, la incidencia de mastitis fue comparada con los climogramas de la zona de Karnal, Haryana, India. El clima cálido y húmedo afectó negativamente a la incidencia de mastitis en todas las razas bovinas y los búfalos. La incidencia fue afectada significativamente por la estación (p<0,01) en todas las razas, aunque el efecto fue menor en las búfalas Murrah. El registro de mastitis fue más elevado en las razas Sahiwal y Tharparkar (p<0,01) que en los cruces Karan-Suiza y Karan-Fries. El incremento del índice de temperatura y humedad dio lugar a una mayor incidencia de mastitis en las vacas (p<0,01), aunque las búfalas Murrah resultaron menos afectadas.
Objectives were to detennine 1) in vitro effects of bST on function of polymorphonuclear leukocyt... more Objectives were to detennine 1) in vitro effects of bST on function of polymorphonuclear leukocytes and lymphocytes and 2} in vivo effects of bST on leukocyte function of heifers fed to maintain medium or high growth rates. When administered in vitro, bST did not affect function of polymorphonuclear leukocytes. [Methyl-3H]thymidine incorporation by resting lymphocytes was stimulated by 1000 ng/ml bST. When given in vitro, bST did not further enhance [methyl-3H]thymidine uptake by mitogen-stimulated lymphocytes cultured at 38SC but reduced the depression of mitogen-stimulated proliferation caused by incubating cells at 42"C. When bST was administered in vivo, phagocytosis and killing of Escherichia coli by polymorphonuclear leukocytes from bSTtreated heifers were not different from cells of control heifers. As measured by [methyl-3H]thymidine uptake after stimulation with phytohemagglutinin, lymphocytes from bST-treated heifers responded similarly to those of control heifers when incubated at 38.5"C, but the depression in [methyl-3H]thymidine uptake due to culture at 42-C was less for lymphocytes obtained from bST-treated
The fate of the newly formed embryo is an uncertain one. It is estimated that about 50% of human ... more The fate of the newly formed embryo is an uncertain one. It is estimated that about 50% of human embryos are lost before implantation. 1 In dairy cattle, pregnancy rate (the proportion of cows that are inseminated that are diagnosed pregnant) has been decreasing over the last 30 years. Pregnancy rates of 50-60% in the 1970s have declined to values of 35-45% today. 2,3 The mechanisms mediating embryo survival and death are incompletely understood. Recently, studies in cattle have led to the emergence of the idea that infectious disease outside the reproductive tract can lead to reduced pregnancy rate. Such observations are suggestive that inflammatory or immune responses associated with infectious disease can cause anovulation,
A 42-mo field trial was initiated in 65 New York Dairy Herd Improvement herds to evaluate the eff... more A 42-mo field trial was initiated in 65 New York Dairy Herd Improvement herds to evaluate the effects of length of dry period on disorders at calving and subsequent milk production. Common disorders and udder edema at parturition were not associated with the length of the preceding dry period. Cows were assigned to treatment group dry periods of 20, 30, 40, 50, and 60 days by modulus 5 of their index numbers. Cows which averaged 10 to 40 days dry produced from 450 to 680 kg less milk in the following lactation than cows with average dry periods of 40 days or longer. Although there was some gain in milk production during the previous lactation from the longer lactationshorter dry periods, it was less than half the loss in the following lactation. The depressing effect of the short dry periods did not carry over to the second lactation. Cows with dry periods of 40 ___ 10 days produced as much as .cows with 50 days dry or more.
... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,'... more ... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,' WG MERRILL, ~ SJ ROBERTS,* and GH SCHMIDT ~ Department of Animal Science 3 and College of Veterinary Medicine 4, Cornell University, ithaca, New York 14850 Abstract A ...
... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,'... more ... on Milk Production 1 RP NATZKE, 3 RW EVERETT, '~ RS GUTHRIE, 4 JF KEOWN, 3 AM MEEK,' WG MERRILL, ~ SJ ROBERTS,* and GH SCHMIDT ~ Department of Animal Science 3 and College of Veterinary Medicine 4, Cornell University, ithaca, New York 14850 Abstract A ...
SummaryThe effect of errors that occur in the diagnosis of intramammary infectious mastitis on th... more SummaryThe effect of errors that occur in the diagnosis of intramammary infectious mastitis on the precision of experiments measuring the efficacy of mastitis therapy has been investigated. Diagnostic errors within the range found by experienced workers can create large biases in the apparent cure rate of therapy particularly at cure rates of less than 0·5. Using confirmed methods of diagnosis rather than single samples and reducing the probabilities of false positive and false negative diagnoses to 0·01 and 0·05 respectively, the biases in the apparent cure rates are reduced to acceptable levels. A method is given for calculating the rates of occurrence of false positive and false negative diagnoses from the results of trials using confirmed diagnoses. These errors cannot be calculated from therapy trial data when diagnosis is based on single milk samples.Because the bias in the measurements of the cure rate is greatest at the lowest levels of elimination, estimates of spontaneous ...
Mastitis is the most costly disease in dairy herds when adequate control procedures are not used.... more Mastitis is the most costly disease in dairy herds when adequate control procedures are not used. A single quarter infected for one lactation may reduce milk production of that cow 10 to 12% in that lactation (25). Additional costs of discarded milk, antibiotics, and culling increase the cost in an average herd to the dollar equivalent of approximately 700 kg
Lactating dairy cows (487) from five commercial herds were in a study of benefits from lactation ... more Lactating dairy cows (487) from five commercial herds were in a study of benefits from lactation therapy of subclinical mastitis. Bacterial isolations and composite milk samples for somatic cell counts were taken from each cow each month for 15 mo. Cows (254) in the experimental ...
Journal of the American Veterinary Medical Association, Jan 15, 1977
The primary sources of mastitis pathogens are infected quarters, chapped, sore, or eroded teat en... more The primary sources of mastitis pathogens are infected quarters, chapped, sore, or eroded teat ends, and the environment. The major means of transfer of the most predominant mastitis pathogens is the milking routine. Methods are available to reduce the number of organisms normally transferred during each of the procedures. However, with the exception of teat cup pasteurization, the application of hygienic procedures in herds where teat dipping is practiced did not result in additional beneficial effects. Effectiveness of 4% chlorine, 0.5 and 1% iodine, and 0.5% chlorhexidine teat dips has been demonstrated in field trials and should be the preferred products in a mastitis control program. Most gram-negative organisms get on teats by direct contact with the bedding. In herds with clinical coliform mastitis, changing the bedding material has been associated with fewer clinical mastitis cases.
Changes in the calcium and phosphorus requirements of the dairy cow at parturition with particula... more Changes in the calcium and phosphorus requirements of the dairy cow at parturition with particular reference to the amounts supplied to the foetus in utero.
Somatic cells were counted and bacteria identified for milk samples from 719 lactating dairy cows... more Somatic cells were counted and bacteria identified for milk samples from 719 lactating dairy cows in 12 commercial herds. These pooled data were used to look at the accuracy of alternative thresholds of somatic cell counts as indicators of intramammary infection. Sensitivity, specificity, and predictability positive and negative at alternative cell count thresholds were calculated. There was an increase of incidence of infection associated with increased cell count. Raising the cell count threshold increased predictability positive and specificity and decreased sensitivity and predictability negative. Also, the effect of prevalence of infection on predictabilities was examined for the pooled data on sensitivity and specificity at a cell count threshold of 400,000 cells/ml. As prevalence of infection increased, predictability of a positive test result also increased, but predictability negative decreased. Differences in accuracy of somatic cell count as a predictor of infection at varying prevalences of infection suggest that test results should be interpreted for individual herds.
Milk cortisol and prolactin concentrations were measured in 12 lactating Holstein cows for 3 days... more Milk cortisol and prolactin concentrations were measured in 12 lactating Holstein cows for 3 days (Experiment 1). On day 3, cows were divided randomly into groups: IV1, IV4, IM, and control. Group IV1 received one intravenous injection of 49 IU adrenocorticotropin, group IV4 the same dosage four times at 2-h intervals, group IM 240 IU adrenocorticotropin intramuscularly, and control cows were injected with saline. Cortisol concentrations in blood plasma were increased in all groups following adrenocorticotropin injection, while milk cortisol concentrations increased fourfold in groups IV4 and IM and remained unchanged in group IV1. In Experiment 2, infusion of 18% saline into the mammary gland of three cows increased the somatic cell count in the infused quarter but had no effect on prolactin and cortisol of milk or plasma. In Experiment 3, six cows each were assigned to treatment groups of saline controls, IV2-0 (40 IU adrenocorticotropin intravenously at 0 and 2 h post-milking) or IV2-8 (40 IU adrenocorticotropin intravenously at 8 and 10 h post-milking). Half udders of each cow were milked before treatment and 4 h later. Increases of cortisol in plasma increased cortisol concentrations of milk 4 h after each treatment (IV2-0 and IV2-8). However, by 12 h after treatment in IV2-0 cortisol concentrations of milk had returned to normal. Increases in adrenal cortisol secretion are followed rapidly (within 4 h) by increased cortisol concentrations in milk. However, these decline rapidly in the absence of sustained increments in blood cortisol. Increased cortisol concentrations in milk most likely represent sustained elevation in plasma cortisol.
Cortisol concentrations in milk and blood plasma were measured in 12 lactating Holstein cows foll... more Cortisol concentrations in milk and blood plasma were measured in 12 lactating Holstein cows following administration of 40 IU adrenocorticotropin intravenously (groups 1 and 2) or 4 ml saline (control). Blood and milk samples were collected at 15 or 30-min intervals for 4 h from control and group 1 cows and at hourly intervals for 4 h from group 2. Cortisol concentrations in plasma and milk were increased 15 min after treatment and peaked by 1 h in group 1 but remained unchanged in controls. Group 2 cows were sampled less frequently but showed a pattern for plasma and milk cortisol concentrations similar to group 1. The profile of increased cortisol concentrations and of their decline 1 to 2 h later was similar for plasma and milk. These results suggest that cortisol concentrations in milk reliably indicate cortisol concentrations in blood and may be valuable in monitoring stress in dairy cows, depending upon duration of stress and its timing relative to milk removal.
Six commercial dairy herds were used to test the relative efficacy of three concentrations of iod... more Six commercial dairy herds were used to test the relative efficacy of three concentrations of iodine as a teat dip over 12 too. Concentrations were .1, .25, and 1% iodine with free iodine contents of 3.5, 4.0, and 1.0 ppm. Two concentrations were compared in each herd. The greatest number of new infections (71) occurred in approximately 120 cows whose teats were dipped with the 1% iodine dip, and the fewest (52) occurred in a similar number of cow quarters dipped in .1% iodine; however, differences were not significant. Clinical mastitis was highest in the 1% group. If all clinical mastitis were the result of infection, even if bacteria were not isolated from the pretreatment sample or from samples collected at the start of the study and those quarters were added to the totals, then reduction of new infection with the .1% product would be significant.
Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial t... more Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial to evaluate effects of daily subcutaneous injections of 0 (A), 5.15 (B), 10.3 (C), and 20.6 mg (D) of recombinantly derived bovine somatotropin monomer. Responses were milk yield and composition, component yields, net energy intake, body weight, and somatic cell counts. Treatments began in fall, 28 to 35 d postpartum, and continued for 266 d. Base ration was corn silage and concentrate. Least squares means of milk and constituent yields and gross efficiency of milk production differed among treatments, but percentage fat and protein, energy intake, body weights, and somatic cell counts did not. Least squares means of 3.5% FCM were 21.3 (A), 25.0 (B), 26.2 (C), and 28.5 kg/d (D); fat and protein yields showed similar response to treatment. Milk yields adjusted for pretreatment yields were 21.1 (A), 25.5 (B), 26.5 (C), and 29.3 kg/d (D). Orthogonal contrasts showed lower milk and constituent yields and net energy intake for control (A) than for hormone-injected cows (B, C, D), but no differences were detected between treatments B, C, and D. Gross efficiency of production (3.5% FCM/feed net energy intake) was greater for hormone-injected cows.
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Papers by Roger Natzke