Prevalence of contagious mastitis pathogens in bulk tank milk in Prince Edward Island

The purpose of this study was to 1) estimate the herd prevalence of contagious mastitis pathogens in bulk milk from Prince Edward Island (PEI) dairy farms, 2) determine the association between bulk milk culture results and mean bulk milk somatic cell count (BMSCC), and 3) investigate the agreement of repeated bulk milk cultures. Three consecutive bulk milk samples were obtained at weekly intervals from all 258 PEI dairy herds and were cultured using routine laboratory methods. Cumulative prevalence of Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma spp. (M. bovis and M. alkalescens) was 74%, 1.6%, and 1.9%, respectively. Bulk milk somatic cell count of Staph. aureus-positive herds was higher than that of negative herds. Agreement for Staph. aureus isolation between 3 consecutive tests was moderate (kappa = 0.46). Mycoplasma bovis and M. alkalescens in bulk milk are being reported for the 1st time in PEI ever and in Canada since 1972.     

Estimation of milk production losses due to sub-clinical mastitis in dairy cattle in Costa Rica

Five dairy farms, situated on the slopes of the volcano Poás in the pre-mountain cloud forest ecological zone, Alajuela and Heredia Provinces, Costa Rica, provided data for estimation of the production losses due to sub-clinical mastitis. Within the same farm, cows with proven sub-clinical mastitis were matched with cows without signs of sub-clinical mastitis, according to breed, lactation number and days in lactation. A total of 529 cows were detected with sub-clinical mastitis, of which only 200 could be paired with control cows free of mastitis; each pair was used only once.

Crude milk production losses per cow with sub-clinical mastitis were estimated at 1.56 kg day⁻¹for daily milk yield. Milk production loss per affected quarter due to sub-clinical mastitis was estimated to be 17.6% on average. The decrease in milk production in heifers with sub-clinical mastitis did not differ significantly from the decrease in production in older cows. No significant difference in milk production loss was detected when the data were stratified on parity or the number of quarters affected.     

Effects of daily exercise on the health of tied dairy cows

The effect of daily exercise on tied dairy cows was ied in 65 initially first and second calvers of the Swedish Red and White dual-purpose breed in a 4 year experiment, starting in July 1985. Half of the group walked outdoors for 2–3 km day⁻¹ from May to October and 400–800 m day⁻¹ from November to April. The rest of the cows were constantly tied. Health in general was significantly and positively influenced by exercise, reducing the need for veterinary treatments. Analysis over time, within lactations, showed that the difference in the number of veterinary treatments occured entirely in Weeks 0–2 of lactation. During those weeks, non-exercised (NE) cows were more affected by calving-related diseases, mastitis and leg problems than the exercised (E) cows. The difference between groups increased with increasing lactation number. In addition, somatic cell count in the milk was higher for the NE cows in their first month of lactation. Among feeding-related diseases, the cases of bloat were notably more frequent among NE cows, whereas exercise did not influence the occurence of clinical or subclinical ketosis. Cases of non-infectious leg and hoof disorders were also notably more frequent in the NE group, which also showed a significantly more serious score for skin lesions on the hocks, measured on one occasion. Scores for sole ulcer were significantly higher for the E cows on one occasion of four, at which there were problems with the surface of the exercise area. The causes of exclusions strengthened the differences mentioned for treatments.     

The selenium status of dairy herds in Prince Edward Island

Bulk tank milk selenium (Se) concentration was compared with mean serum Se concentration in 15 herds and was found to be an accurate reflection of the herd Se status. The Se status of 109 Prince Edward Island (PEI) dairy herds was monitored for 1 year using bulk tank milk Se concentration. Fifty-nine percent of the herds surveyed were, at some point, found to be marginal or deficient in Se, putting them at risk of disease and suboptimal production. The periods of greatest risk of deficiency were fall and winter, at which time 5% and 4%, respectively, of herds sampled fell in the range considered truly deficient in Se. Herds in which Se supplementation was provided in the form of a commercial dairy concentrate were over 4 times more likely to be Se-adequate than herds not using this method, and adjusted average daily milk yield was 7.6% greater in herds determined to be Se-adequate when compared with Se-marginal herds. We conclude that many dairy producers in PEI are providing insufficient supplementary Se in the ration to meet the recommended Se intake for lactating cows.     

Clinical mastitis in dairy cattle in Ontario: frequency of occurrence and bacteriological isolates.

The objective of this study was to describe the frequency of occurrence of clinical mastitis in dairy herds in Ontario. The study group consisted of 65 dairy farms involved in a 2-year observational study, which included recording all clinical mastitis cases and milk sampling of quarters with clinical mastitis. Lactational incidence risks of 9.8% for abnormal milk only, 8.2% for abnormal milk with a hard or swollen udder, and 4.4% for abnormal milk plus systemic signs of illness related to mastitis were calculated for 2840 cows and heifers. Overall, 19.8% of cows experienced one or more cases of clinical mastitis during location. Teat injuries occurred in 2.1% of lactations. Standard bacteriology was performed on pretreatment milk samples from 834 cows with clinical mastitis. The bacteria isolated were Staphylococcus aureus (6.7%), Streptococcus agalactiae (0.7%), other Streptococcus spp. (14.1%), coliforms (17.2%), gram-positive bacilli (5.5%), Corynebacterium bovis (1.7%), and other Staphylococcus spp. (28.7%). There was no growth in 17.7% of samples, and 8.3% of samples were contaminated. Clinical mastitis is a common disease in dairy cows in Ontario; approximately 1 in 5 cow lactations have at lease one episode of clinical mastitis. There is, however, considerable variation in the incidence of clinical mastitis among farms. The majority of 1st cases of clinical mastitis occur early in lactation, and the risk of clinical mastitis increases with increasing parity. Environmental, contagious, and minor pathogens were all associated with cases of clinical mastitis.     

Bovine virus diarrhoea virus: detection of Danish dairy herds with persistently infected animals by means of a screening test of ten young stock

In each of 42 Danish dairy herds, ten young stock aged 8–18 months were tested for antibodies against bovine virus diarrhoea virus (BVDV). At the same time a bulk milk sample from each herd was examined for antibodies against BVDV.

The herds could be divided into two distinct groups: (1) Group A (24 herds) had three or less antibody carriers among the ten young stock sampled from each herd and were considered ‘slightly infected’; (2) Group B (18 herds) had eight or more antibody carriers in the ‘spot’ sample and were therefore considered ‘heavily infected’. Persistently infected animals were not found in two Group A herds studied by a subsequent total herd blood test but were detected in five Group B herds in which all animals in the herds were subsequently tested.

Bulk milk titers were generally higher in Group B than in Group A herds. However, there was considerable variation, and in most cases it was not possible to distinguish the two herd categories from one another by means of bulk milk titers.     

Incorporation of observations with different residual error variances into existing complex test-day models

Automated milking systems (AMS) have become popular on dairy farms. Due to a different test-day recording scheme the variation of test-day observations differ from AMS differ from those of conventional milking system (CMS). An approach is presented for upgrading the genetic evaluation model for production traits milk, protein and fat yield by including residual covariance matrices for AMS and CMS test-day observations. Residual variances were found to be 16–37% smaller for milk and protein yields and 42–47% larger for fat yield when recorded under AMS herds compared to CMS herds. Daily heritability was higher for milk and protein yield and lower for fat yield when traits were recorded under AMS compared to recording under CMS. No difference was found between AMS and CMS in 305-day heritability for milk and protein yield except for second lactation milk yield. 305-day heritability for fat was lower for all lactations under AMS.     

A comparison of production and management between Wisconsin organic and conventional dairy herds

An observational study was conducted in Wisconsin to compare production and management on organic and conventional dairy farms. Thirty organic dairy herds, where antimicrobials are rarely used for calves and never used for cows, were compared with 30 neighboring conventional dairy farms on which antimicrobials were routinely used for animals of all ages. A seven-page questionnaire regarding milk production, milking practices, housing, incidence of the major dairy diseases and medical treatments was used to assess management and production during 2000-2001. Body condition scores (BCS) of lactating cows and environmental and animal sanitation scores (EASS) were also collected on each of two occasions. The organic herds had significantly fewer cattle than did the conventional herds (P=0.017). The average daily milk production per cow in organic dairy herds (20.2 kg/day) was lower than that of conventional herds (23.7 kg/day). The incidence of clinical mastitis (CM) on organic farms (28 cases per 100 cow-years at risk) was not statistically different from that of on conventional farms (32 cases per 100 cow-years at risk). No significant difference in bulk tank somatic cell count (BTSCC) was observed between organic farms (262,000 cells/ml) and conventional farms (285,000 cells/ml). The average annual cull rate was 18.0 cases per 100 cow-years for the conventional farms and 17.2 for the organic farms (P=0.426). Our paired t-test results indicated significantly higher parasite burden on organic dairy farms; however, no significant difference between the two farm types when controlling for season (March and September), grazing intensity (no grazing, little grazing, grazing with access to housing and grazing only) and herd average milk production per cow. There was little evidence of other fundamental differences between the two farm types in other management and production parameters.     

A survey on Dictyocaulus viviparus antibodies in bulk milk of dairy herds in Northern Germany

Parasitic bronchitis caused by the bovine lungworm, Dictyocaulus viviparus, occurs worldwide in temperate areas. The parasite is found predominantly in calves and heifers, but dairy cattle can suffer from lungworms when they become infected for the first time or if they have lost immunity due to lack of exposure to lungworm larvae during the grazing season. The present study was performed to determine the D. viviparus bulk milk antibody prevalence in dairy herds in the East Frisian region of northwestern Germany, Lower Saxony, by analysing bulk milk samples collected in January (860 samples), September (866 samples) and November (860 samples) 2008, thereby representing 906 dairy farms. These samples were tested for antibodies against D. viviparus by a milk ELISA. This test detects patent infections only since it is based on recombinant major sperm protein as antigen. While in January 12.8% of dairy farms were positive for D. viviparus antibodies, the bulk milk samples collected in September and November revealed 6.9% and 6.6% positive dairy herds. From the 906 dairy farms included in the study, 191 (21.1%) tested positive at least once for antibodies against lungworm. From 810 dairy farms from which bulk milk samples were obtained during all three samplings, 146 (18.0%) farms were positive at one sampling date, 27 (3.3%) at two, and 4 (0.5%) on all three sampling dates. The majority of the farms represented in the study belonged to four districts of East Frisia, which showed no significant difference in the proportion of positive dairy farms.     

Impact of feeding pattern and feed purchase on area- and cow-related dairy performance of organic farms

Livestock production and ruminants in particular are an integral part of the organic mixed farming concept. In this paper, the feeding patterns of 26 organic dairy farms in two different regions in Germany are analysed, with particular emphasis on the amount and proportion of concentrates and purchased feed related to the dairy performance expressed per cow and hectare. Calculated on an energy basis (MJ NEL), the annual average milk yield of 6737 kg cow^− 1 is derived from roughage (74%), concentrates and cobs (23%), and commercial processing by-products (e.g., spent grains) (3%). Per cow and year, 937 kg dry matter (DM) (range: 0–2724 kg) of concentrates are fed with an intensity of 135 g kg^− 1 milk (range: 0–378 g kg^− 1). Approximately 65% of the concentrates and commercial processing by-products are purchased. The area-related milk yield is almost 7000 kg ha^− 1. For fodder production, 0.96 ha per cow is needed, of which 0.85 ha is farm land. The equivalent production area for purchased fodder is 0.11 ha. In the analysed region in northwestern Germany, most correlations between milk yield and analysed feeding parameters are close and significant. This is in contrast to the region in the south, where the variability of amount and proportion of the different feed types is predominantly independent of the milk yield. Intensification of dairy production to increase milk performance using a higher proportion of concentrates and purchased feed at some of the analysed farms needs to be carefully assessed according to the organic farming profile.     

Use of an enzyme-linked immunosorbent assay in bulk milk to estimate the prevalence of Neospora caninum on dairy farms in Prince Edward Island, Canada

This study evaluated the use of bulk milk as a diagnostic tool for estimation of herd-level Neospora caninum exposure in Atlantic Canada; it was used to estimate the prevalence of dairy farms with a within-herd N. caninum-seroprevalence > or = 15% in Prince Edward Island (PEI). The variation over time of N. caninum antibodies in bulk milk is also reported. Skimmed bulk milk and individual serum samples were analyzed for N. caninum antibodies by using an enzyme-linked immunosorbent assay (ELISA). Bulk milk samples were collected in May 2004 (n = 235), May 2005 (n = 189), and June 2005 (n = 235). The prevalence of dairy farms with a within-herd seroprevalence > or = 15% on PEI was 6.4% in May 2004. In May and June 2005, respectively, 10.1% and 10.2% of farms had a > or = 15% within-herd seroprevalence. In 11 farms that were considered positive based on bulk milk samples, blood samples were collected from all adult cows in September 2005, in conjunction with a 4th bulk milk sample on the same day. The correlation coefficient between serology and bulk milk ELISA was 0.87. The results of this study demonstrate that the prevalence of N. caninum in dairy farms can be estimated by using a bulk milk ELISA.     

Between-herd prevalence of Mycoplasma bovis in bulk milk in Flanders, Belgium

Mycoplasma bovis (M. bovis) is a highly infectious pathogen of cattle causing pneumonia, polyarthritis, otitis, and less frequently, subcutaneous abscesses, abortions and meningitis. Ineffective drugs treatments, culling of infected cows and loss of milk production can lead to significant economic loss on dairy farms. The early detection of cows excreting M. bovis bacteria to prevent mastitis outbreaks is warranted. Reports suggest that the risk of M. bovis mastitis is higher in larger dairy herds. The objective of this study is to estimate the herd-level prevalence of M. bovis in Flanders, Belgium by culturing bulk tank milk samples taken from dairy farms. Three bulk tank milk samples per dairy herd were taken over four weeks, with collection intervals of two weeks. Culturing was done after pre-incubation using modified Hayflicks media to increase the chances of recovery of bacteria. For the identification of M. bovis, tDNA intergenic spacer PCR was used. In three herds (1.5%) of the 200 herds sampled, M. bovis was isolated from one of the three consecutive bulk tank milk samples. We conclude that in Flanders in 2009 at least 1.5% of the dairy herds had one or more cows excreting M. bovis in the milk. The frequent monitoring of bulk tank milk to detect the presence of M. bovis, especially in expanding herds on farms that often purchase replacement animals, should be encouraged in order to detect the presence of M. bovis and to monitor the success of control procedures following an outbreak of mycoplasmal mastitis in the herd.     

Bovine tuberculosis and milk production in infected dairy herds in Ireland

This study describes the relationship between bovine tuberculosis (TB) and milk yield in TB-infected dairy herds in Ireland. The study had two objectives: to determine whether cows detected as TB reactors (and thus subject to immediate slaughter) were likely to be the higher milk-producing cows, and to determine whether subclinical TB infection was associated with reduced milk production at or around the time of disclosure (detection). All Irish dairy herds restricted from trading between the 1^st June 2004 and the 31^st May 2005 as a result of two or more TB reactors by the Single Intradermal Comparative Tuberculin Test (SICTT) were considered for study. The data consisted of 419 herds. Data were collected on all TB reactors and a random sample of 5 non-reactor cows in these herds: a data set of 4340 cows (2342 TB reactors and 1998 non-reactors). Previous milk data for the cows were taken into consideration and thus all lactations on a cow were analysed together with the years of lactations. There was an inherent hierarchical structure in the data, with lactations nested within cows and cows within herds and thus a linear mixed model with two random effects was used to describe the data. The results of this study showed that for all lactations and years under investigation, milk yield was significantly lower for TB reactor cows, with differences ranging from 120 kg (2003, lactation 3) to 573 kg (2001, lactation 1), when compared to the non-reactor cows.     

奶牛酮病对奶牛生产性能的影响

为了研究奶牛酮病对奶牛生产性能的影响,选取规模奶牛场和散养户共450头奶牛进行跟踪调查,结果表明,规模奶牛场发病率为14.69%,而散养户发病率高达36.92%,其中规模奶牛场的瘫痪型、神经型及消化型酮病分别比散养户低7.16%(P0.05)、6.1%(P0.05)和8.96%(P0.05);秋季发病率比冬季、夏季和春季分别高3.34%(P0.05)、10.89%(P0.05)、13.78%(P0.05);受胎率健康组比酮病组高出50%,差异极显著(P0.01);4胎以上发病率高达47.22%,分别比1胎~4胎高出42.16%(P0.01)、32.13%(P0.01)、29.86%(P0.01)、10.75%(P0.05);泌乳量在31kg以上的奶牛其发病率高达47.76%,分别比泌乳量在21kg~30kg、11kg~20kg、10kg以下的发病率高12.31%(P0.05)、19.86%(P0.01)、25.36%(P0.01),患病前,奶牛的平均日产奶量为17.32kg,而发病后泌乳量降低至7.89kg,差异极显著(P0.01);患病后,其乳成分也发生较大变化,其乳蛋白率、乳脂率、乳糖率及乳干物质分别比患病前降低了1.07%、0.56%、0.73%及3.47%,差异显著(P0.05)。奶牛酮病发病具有一定规律性,可导致奶牛情期延迟、受胎率下降、淘汰率增大、泌乳性能下降及乳质变差。     

Prevalence of Coxiella burnetii antibodies in Danish dairy herds

During recent years in Denmark higher rates of antibodies to Coxiella burnetii have been detected in animals and humans than previously reported. A study based on bulk tank milk samples from 100 randomly selected dairy herds was performed to estimate the prevalence and geographical distribution of antibody positive dairy herds. Using the CHEKIT Q-Fever Antibody ELISA Test Kit (IDEXX), the study demonstrated a prevalence of 59% antibody positive herds, 11% antibody intermediate herds and 30% antibody negative herds based on the instructions provided by the manufacturer. The geographical distribution does not indicate a relationship between the regional density of dairy farms and the prevalence of antibody positive dairy farms. The result supports the hypothesis of an increase in the prevalence of positive dairy herds compared to previous years.     

Descriptive epidemiology of culling in dairy cows from 34 herds in New York State

Data on parity, disease, farmers' stated primary reasons for culling and stage of lactation at diagnosis and at culling were used to describe patterns of culling in Holstein lactations from 34 New York herds. Of 7763 lactations, 18.7% ended in culling [death (95 cows), sales for dairy purposes (104 cows), or slaughter]. The culling rates for specific reasons were: dairy purposes 1.3%, low production 3.8%, reproduction 4.8%, udder problems 4.0%, feet and legs 1.2%, old age 0.3%, accidents 0.3% and miscellaneous reasons 2.9%. Culling increased with parity (at least through Lactation 6) and primarily was due to production, reproduction and udder problems. Culling for these 3 reasons peaked immediately after calving, again between 151 and 240 days post-partum (poor milk production) and at >240 days post-partum (poor reproductive performance). First-lactation cows sold for dairy use tended to be sold in early lactation. Death in older cows usually occurred early in lactation and was due to udder problems or to miscellaneous causes.

Compared to lactations without the disease, lactations with a diagnosis of downer cow, clinical mastitis or treat problems were 3.5, 2.0 and 2.7 times more likely to end in culling, respectively. Among cows diagnosed with a disease and culled, many were culled the same day or within 30 days of the diagnosis. Such “immediate” culling upon diagnosis was especially typical of cows with milk fever, downer cow syndrome, left displaced abomasum, teat problems, and foot and leg problems (and for some cases of clinical mastitis), implying that these disorders led to “forced” culling, which was particularly costly to the farmers.     

荷斯坦青年牛初次配种妊娠月龄对头胎和二胎产奶量和繁殖性能的影响

旨在研究母牛初次配种妊娠月龄（age at first pregnancy,AFP）对其泌乳性能和主要繁殖性能的影响。本研究以我国北方地区2个规模化奶牛场13 927头荷斯坦母牛（A牧场8 091头,B牧场5 836头）的生产数据为基础,统计了母牛AFP、头胎和二胎的产奶量、产后首次发情时间、首次配种时间和首次受孕时间,然后将母牛根据AFP的早晚（12~19月龄）分为8组,对各试验组母牛的头胎和二胎产奶量和主要繁殖性能的数据进行比较分析。结果表明：1）2个规模化奶牛场荷斯坦青年牛AFP以13和14月龄为主（总占比70.1%）;2）AFP可显著影响荷斯坦青年牛头胎和二胎的305 d产奶量（P<0.05）,其中AFP为14月龄时A牧场头胎和二胎305 d产奶量均最高,分别为15 102和15 534 kg;3）AFP可显著影响荷斯坦青年牛头胎和二胎产后首次发情时间和受孕时间（P<0.05）,AFP为14月龄时头胎产后首次发情和受孕情况最优;4）对于产后首配时间,除A牧场头胎AFP为16月龄时产后首次配种时间显著高于AFP为17月龄时（P<0.05）外,其余各组间均无显著性差异（P ≥ 0.05）,并且各组间配种时间相差≤ 5 d;5）通过对A牧场在场牛（2 703头）与淘汰牛（660头）的AFP记录数据分析发现,在场牛的AFP为14.52月龄,显著高于淘汰牛的AFP（P<0.05）。因此,在北方地区现有的生产管理水平下,14月龄可能是荷斯坦青年牛最适宜的初次配种妊娠月龄,这对我国规模化奶牛场选择荷斯坦青年牛适宜的初次配种月龄具有一定参考价值。     

Health of cows,calves and young stock on 26 organic dairy herds in Sweden

The health and housing of the stock on 26 organic dairy herds in four counties in eastern Sweden were studied for one year. The herds ranged in size from 12 to 64 cows, and their milk production from 3772 to 10,334 kg per cow per year. A large-animal practitioner visited the farms three times during the year, and a random sample of a third of the cows in each herd were examined. The calves and young stock and their housing were also studied. The calves were in good condition in all but four herds; their serum immunoglobulins varied from almost none to high levels. The young stock were in good condition and in good housing in 20 herds. No cows with clinical signs of metabolic disorders were found. Body condition scores were adequate or good except in two herds. Acetone was analysed in milk samples from individual cows three to six weeks postpartum, and only sporadic cases with high levels were found. The incidence of diseases treated by a veterinarian was lower in the organic herds than the average for the conventional herds in the local dairy association. The findings at the farm visits supported these data, and it is evident that a good standard of health and welfare can be achieved in organic dairy herds.     

Management practices to control gastrointestinal parasites in dairy and beef goats in Minas Gerais; Brazil

Parasitic infection is recognized worldwide as a limiting factor in the production of goats, and various control methods are used to reduce economic losses, often without considering the epidemiology of the parasites. This has led to the development of highly tolerant parasite populations and the presence of chemical residues in the beef and milk. The objective of this study was to determine the level of knowledge of goat farmers about parasitic diseases and to correlate this with the epidemiology of endoparasites and parasite control practices in goat farms in the state of Minas Gerais, Brazil. The analysis was based on a questionnaire applied by trained veterinarians. The sample was homogeneous throughout the state, covering 18.4% (157/853) of municipalities. Eighty-four dairy goat farms in 81 municipalities and 200 properties with beef goats in 76 municipalities were evaluated. The herd size per goat farm ranged from 4 to 57 (average 24) for beef herds and from 2 to 308 (average 63) for dairy farms. The majority of the beef herd production was extensive and semi-extensive (98.5%), while the dairy herds were maintained under intensive farming (98.8%). The mixed production of goats and sheep was reported by 36.5% of beef goat farmers and by 20.2% of dairy goat farmers. Among the beef goats farms on which the technological level was determined, 2.0% were categorized as having high technological level, 34.5% as medium, and 63.5% as low. Of the 84 dairy farms, 30% operated at a high, 47% at a medium, and 23% at a low technological level. The adoption of practices to reduce parasitism, such as the quarantine of animals, treatment of newly arrived animals, regular cleaning of the floor, and technical assistance, was significantly higher on dairy farms than on beef farms. Although 85.7% of dairy farmers and 83% of beef farmers medicate their animals, the treatments were performed without technical criteria, and deworming intervals ranged from 30 to 120 days or more. The average interval between treatments was significantly longer in dairy goat herds (4.8 months) than in the beef herds (3.6 months). The most commonly used drugs were macrocyclic lactones (37.7% in dairy and 39.5% in beef herds) and benzimidazoles (48.9% in dairy and 31.5% in beef herds). Goat production in Minas Gerais is still in its infancy, and even though using a control program associated with other health practices, producers still rely heavily on chemicals to get satisfactory results.     

Phosphorus Intake and Excretion on South Carolina Dairy Farms

The objective of this study was to survey dairy farmers to determine P levels in feed and manure. Feed and manure samples were collected from 19 Holstein, six Jersey, and two Guernsey farms in South Carolina. Samples from the Jersey and Guernsey herds were pooled. Samples were dried and analyzed for N and P. Amounts of all feeds were recorded; then, nutrient intake was determined. Dairy Herd Improvement records were used to determine the milk yield and fat content and, subsequently, the P requirement. Nineteen of 27 herds (70%) were fed more P than required according to nutrient requirements established by the NRC. The average P intake was 94.9 g (0.48% of diet DM) compared with the average requirement of 78.3 g (0.41% of diet DM). There were correlations between dietary and fecal P (R² = 0.46) and between CP and P intake (R² = 0.62). There was not a significant correlation between excess P intake and milk yield. In summary, many dairy producers overfeed P. Feeding dietary P at recommended levels will optimize milk yield and reduce P excretion on dairy farms.