Mature Equivalent Milk Research Articles

Comparison of Two Estrus-Synchronization Protocols and Timed Artificial Insemination in Dairy Cattle

The objective of this study was to evaluate the effect of the Ovsynch protocol with and without exogenous progesterone on pregnancy rate (PR) in cows in which estrous cycles were previously synchronized with 2 doses of PGF2α and that were not detected in estrus during the presynchronization period. The study was conducted in Chihuahua, Mexico (8,650 Holstein milking cows; 305-d mature equivalent milk yield=13,790kg). On d 47 postpartum, estrous cycles in cows were synchronized by using 2 doses of PGF2α 14 d apart. Any cow detected in estrus during this presynchronization period was inseminated. Cows not detected in estrus were selected at random and assigned to receive progesterone supplementation or to serve as controls. Controls (n=594) were subjected to the Ovsynch protocol and cows in the progesterone supplemented treatment (n=594) were subjected to the Ovsynch protocol plus an intravaginal insert containing 1.9g of progesterone inserted at the time of the first GnRH injection and removed 7 d later. Progesterone-supplemented cows had a greater PR (31.2%) compared with controls (22.7%). Plasma progesterone concentrations at artificial insemination (AI) were <1ng/mL and did not differ between treatments. At 14 d post-AI, however, more cows that received progesterone supplementation had concentrations of progesterone >1ng/mL compared with controls. It was concluded that after a presynchronization period, cows subjected to the Ovsynch program and supplemented with exogenous progesterone had a greater PR and greater concentrations of progesterone after AI than those subjected to the Ovsynch protocol and not supplemented with progesterone.

Use of Age and Milk Production Data to Improve the Ability of Enzyme-Linked Immunosorbent Assay Test Results to PredictMycobacterium Aviumssp.ParatuberculosisFecal Culture Status

Cows from 2 California dairies were tested for paratuberculosis at the end of lactation by using fecal culture and a commercially available serum enzyme-linked immunosorbent assay (ELISA) test kit. Individual cow characteristics and production variables were evaluated along with ELISA testing results as predictors of fecal culture status. In multivariable logistic regression analysis, age and a herd-standardized version of 305-day mature equivalent (305 ME) milk production were significant predictors of fecal culture status after adjusting for herd, quarter of the study year, and ELISA sample-to-positive (S/P) ratio. The area under a nonparametric receiver operating characteristic curve was significantly greater for a multivariable model that included age and the level of milk production when compared with a model without these covariates. In conclusion, consideration of cow-level covariates was useful as an aid in predicting Mycobacterium avium ssp. paratuberculosis (MAP) fecal culture status. For a given ELISA S/P ratio, older cows and those with lower 305 ME milk production relative to other cows in the herd were significantly more likely to be shedding MAP in their feces at the end of lactation.

We-P11:210 Evaluation of novel phosphatidic acid derivatives as antagonists of platelet activation induced by the plaque lipid lysophosphatidic acid

Our objectives were to evaluate the acute effects of a controlled internal drug release (CIDR) insert containing 1.38 g of progesterone (P4) on the release of LH, follicular growth, and circulating concentrations of P4 in cows treated with GnRH at the time of CIDR insertion. Nonpregnant, lactating dairy cows (n = 27) were blocked by parity, predicted 305-d mature-equivalent milk production, and body condition score and randomly assigned to 1 of 3 treatments: (1) CIDR insertion concurrent with an injection of 200 µg of GnRH (n = 10; 2GP4); (2) CIDR insertion concurrent with an injection of 100 µg of GnRH (n = 10; 1GP4); and (3) injection of 100 µg of GnRH (n = 7; CON). Prior to onset of treatments, cows were submitted to a presynchronization protocol that consisted of a CIDR insert containing 1.38 g of P4 from d −7 to −2, 25 mg of PGF2α on d −2 and −1, and 100 µg of GnRH on d 0. Experimental treatments were applied on d 6, the early luteal phase of the estrous cycle. Concentrations of P4 in plasma were determined on d −2 and 0 and at 0, 15, 30, 60, 120, 240, 345, 600, and 1,200 min relative to treatment on d 6. Concentrations of LH were determined in plasma samples obtained at 0, 15, 30, 60, 120, 240, and 345 min relative to treatment on d 6. Ultrasonography examinations of ovarian structures were performed on d −2, 0, 2, and at 0, 600, and 1,200 min relative to treatment on d 6. Mean concentrations of P4 in the CON group (1.91 ± 0.28 ng/mL) were lower than in 2GP4 (3.40 ± 0.26 ng/mL) and 1GP4 (3.31 ± 0.24 ng/mL) groups, but concentrations in 2GP4 and 1GP4 were similar. Mean concentration of LH in response to the GnRH injection on d 6 was greatest in 2GP4 cows (3.08 ± 0.21 ng/mL) and did not differ between 1GP4 (2.23 ± 0.21 ng/mL) and CON (2.14 ± 0.25 ng/mL) cows. The diameter of the dominant follicle on d 6 was similar among treatments (2GP4 = 15.34 ± 0.50; 1GP4 = 15.31 ± 0.50; CON = 14.77 ± 0.62 mm). In conclusion, CIDR insertion concurrent with a 100- or 200-µg dose of GnRH neither altered GnRH-induced LH release nor had an acute effect on dominant follicle growth.

Genetic parameters and trends in the Chilean multibreed dairy cattle population.

Estimates of additive and nonadditive multibreed co-variance components, genetic parameters, and predicted genetic values for first lactation 305-d mature equivalent (ME) milk yield, fat yield, and protein yield were computed using data from a sample of 3316 cows from the Chilean Holstein-other breeds multibreed population. Variances and covariances were estimated by 2-trait REML analyses using a Generalized Expectation-Maximization algorithm applied to multibreed populations. Multiple estimates of additive genetic, nonadditive genetic, and environmental variances from 2-trait analyses were averaged to yield a single variance estimate for each trait and effect. Heritabilities were moderate for all traits in Holstein, other, and Holstein x other crossbred groups. Interbreed interactibilities (ratio of nonadditive genetic to phenotypic variances) were all near zero. Multibreed additive, nonadditive, and total genetic trends were estimated using the complete dataset (56,277 cows). Upward trends between 1990 and 2000 existed for all traits, genetic effects, and breed groups, except for 305-d ME protein yield in 1/4 Holstein, indicating that Chilean dairy producers were successful in choosing progressively better semen and sires from imported and local sources over time.

The relationship between endogenous cortisol, blood micronutrients, and neutrophil function in postparturient Holstein cows.

Neutrophil function, blood micronutrients, and cortisol concentrations were measured in 43 clinically healthy postparturient Holstein cows. Estimated 305-day mature equivalent milk production and neutrophil function were related to results of the blood micronutrient concentrations and neutrophil function tests. Cattle had low to normal zinc concentrations; normal to high selenium, vitamin E, and cortisol concentrations; and normal copper concentrations. Blood selenium (P = .03) and zinc (P = .027) concentrations were both significant predictors of neutrophil adhesion, and selenium (P < .001) was a significant predictor of neutrophil cytochrome C reduction (superoxide production). Fourteen of 20 (70%) cattle with blood selenium concentrations > 300 ng/mL had neutrophil adhesion, and 15 of 20 (75%) had cytochrome C reduction above the mean value for this group. There was also a significant correlation (r = 0.331; P = .037) between cytochrome C reduction and estimated milk production. These findings suggest that neutrophils from postparturient dairy cows with higher blood concentrations of selenium have greater potential to kill microbes, and that cattle with greater superoxide production may have higher milk production.

Analysis of the Relationship Between Type Traits, Inbreeding, and Functional Survival in Jersey Cattle Using a Weibull Proportional Hazards Model

A Weibull proportional hazards model was used to analyze the effects of 13 linear type traits, final score, and inbreeding on the functional survival of 268,008 US Jersey cows in 2416 herds with first calving from 1981 to 2000. Functional survival was defined as the number of days from first calving until involuntary culling or censoring. The statistical model included the time-dependent effects of herd-year-season of calving, parity by stage of lactation interaction, and within-herd-year quintile for mature equivalent milk yield, as well as the time-independent effects of inbreeding, age at first calving, and linear type traits or final score (analyzed one at a time). Each type trait was divided into 10 classes, and the relative risk of involuntary culling was calculated for animals in each class after accounting for the aforementioned management factors. Type traits with the greatest contribution to the likelihood function were udder depth, fore udder attachment, front teat placement, and udder support. Cows with low scores for these traits had a risk of culling that was 1.3 to 1.8 times that of cows with intermediate scores. Cows with high scores for udder depth and udder support had a risk of culling only 0.7 to 0.85 as great as that of cows with intermediate scores. Intermediate scores were desirable for rear leg set, dairy form, and strength, but stature, rump angle, and rump width had negligible effects on survival. Cows with low final scores had a risk of culling that was 1.35 times that of cows with intermediate scores, whereas cows with high final scores had a risk of culling that was 0.8 times that of cows with intermediate scores. Animals with inbreeding coefficients greater than 10% had a slightly higher risk of culling than animals with inbreeding coefficients less than 5%.

Genotype by Environment Interaction for Yield and Somatic Cell Score with Alternative Environmental Definitions

Differential genetic expression in high and low opportunity Sicilian Holstein-Friesian and Brown Swiss herd environments was investigated using endogenous and exogenous variables in a set of three definitions. Results of genetic by environmental interaction were compared using alternative environmental definitions: within herd-year standard deviation for mature equivalent milk yield (HYSD), detectable incidence of normal vs. abnormal (peakless) lactation and herds clustered by causal relationships from high and low frequency use of nutrition, milking, health and animal handling practices. Data for genetic analysis consisted of first-lactation standardized yields of milk, fat and protein, and weighted somatic cell score for 8897 daughters of 825 Holstein-Friesian sires and 1143 daughters of 220 Brown Swiss sires. Components of covariance, heritabilities, and genetic correlations were estimated using bivariate and multivariate sire models for average and contrasting environments for each definition. Sire variances for yields were consistently smaller in the low opportunity environments of both breeds. Except for differential incidence of abnormal lactation in Friesian herds, correlated yield response in less privileged environments was 0.41 to 0.81 as much as in high opportunity environments, a substantial loss. Genetic correlations between HYSD environments for yield traits of Friesian were 0.48 to 0.66 but exceeded 0.80 for other definitions. Less correlated response in somatic cell score was also predicted for environments with low use of yield-enhancing practices (0.66 for Friesian and 0.61 for Brown Swiss), which may have resulted from less health care and poorer milking management. Therefore, unfavorable management interactions likely foster unequal gains from selection in contrasting environments defined exogenously or by incidence of peakless lactation. Conversely, greater genetic as well as phenotypic response is expected from additional inputs of nutrition, health care and milking management.

Effect of feeding methionine supplements with different rumen escape values on performance of high producing dairy cows in early lactation

A study was undertaken to compare a liquid form of methionine hydroxy analog (MHA; Novus Intl., Atlanta, GA, USA) and d, l-methionine, two methionine supplements with different rumen degradation escape values, on early lactational and reproductive performance by high producing dairy cows. Forty pregnant Holstein cows housed in a free-stall barn, were blocked by parity, date of calving, and previous 305-day mature equivalent milk production, and at calving were assigned randomly to one of two total mixed rations (TMR) containing MHA, or d, l-methionine, and group-fed for ad libitum intake. Cows spent 33±15.0 days in the fresh group, after which they were moved to the high producing group where they stayed up to 8-week postpartum. The TMR were formulated to meet approximately 100% of required methionine, lysine, and other essential amino acids. An adequate amount of d, l-methionine was fed in order to provide a similar amount of methionine postruminally as provided by MHA, assuming a rumen degradation escape value of 40% for MHA and 22% for d, l-methionine. The TMR had forage to concentrate ratio of 40 to 60% for fresh group cows and 42 to 58% for high group cows. There were no differences between treatments in milk yield, content of milk fat, CP and true protein, linear somatic cell count, change in body condition score, and days to first service. In conclusion, d, l-methionine performed as well as MHA in promoting milk yield and contents of milk fat and protein when fed at levels aimed at supplying similar amounts of methionine postruminally as would be supplied by MHA fed at the recommended level.

The Relationship between Endogenous Cortisol, Blood Micronutrients, and Neutrophil Function in Postparturient Holstein Cows

Neutrophil function, blood micronutrients, and cortisol concentrations were measured in 43 clinically healthy postparturient Holstein cows. Estimated 305-day mature equivalent milk production and neutrophil function were related to results of the blood micro-nutrient concentrations and neutrophil function tests. Cattle had low to normal zinc concentrations; normal to high selenium, vitamin E, and cortisol concentrations; and normal copper concentrations. Blood selenium (P= .03) and zinc (P= .027) concentrations were both significant predictors of neutrophil adhesion, and selenium (P < .001) was a significant predictor of neutrophil cytochrome C reduction (superoxide production). Fourteen of 20 (70%) cattle with blood selenium concentrations >300 ng/mL had neutrophil adhesion, and 15 of 20 (75%) had cytochrome C reduction above the mean value for this group. There was also a significant correlation (r= 0.331; P= .037) between cytochrome C reduction and estimated milk production. These findings suggest that neutrophils from postparturient dairy cows with higher blood concentrations of selenium have greater potential to kill microbes, and that cattle with greater superoxide production may have higher milk production.

Heritability and Correlations Among Body Condition Score Loss, Body Condition Score, Production and Reproductive Performance

The objectives of this study were to estimate the heritability of body condition score loss (BCSL) in early lactation and estimate genetic and phenotypic correlations among BCSL, body condition score (BCS), production, and reproductive performance. Body condition scores at calving and postpartum, mature equivalents for milk, fat and protein yield, days to first service, and services per conception were obtained from Dairy Records Management Systems in Raleigh, NC. Body condition score loss was defined as BCS at calving minus postpartum BCS. Heritabilities and correlations were estimated with a series of bivariate animal models with average-information REML. Herd-year-season effects and age at calving were included in all models. The length of the prior calving interval was included for all second lactation traits, and all nonproduction traits were analyzed with and without mature equivalent milk as a covariable. Initial correlations between BCS and BCSL were obtained using BCSL and BCS observations from the same cows. Additional genetic correlation estimates were generated through relationships between a group of cows with BCSL observations and a separate group of cows with BCS observations. Heritability estimates for BCSL ranged from 0.01 to 0.07. Genetic correlation estimates between BCSL and BCS at calving ranged from -0.15 to -0.26 in first lactation and from −0.11 to −0.48 in second lactation. Genetic correlation estimates between BCSL and postpartum BCS ranged from −0.70 to −0.99 in first lactation and from −0.56 to −0.91 in second lactation. Phenotypic correlation estimates between BCSL and BCS at calving were near 0.54, whereas phenotypic correlation estimates between BCSL and postpartum BCS were near −0.65. Genetic correlations between BCSL and yield traits ranged from 0.17 to 0.50. Genetic correlations between BCSL and days to first service ranged from 0.29 to 0.68. Selection for yield appears to increase BCSL by lowering postpartum BCS. More loss in BCS was associated with an increase in days to first service.

Relationship Between DHI Production Values and Myers-Briggs Type Indicator As a Measure of Management Ability

Associations between owners’ Myers-Briggs Type Indicator (MBTI) preferences (E = extraversion vs. I = introversion; S = sensing vs. N = intuition; T = thinking vs F = feeling; J = judging vs. P = perceiving) and 21 Dairy Herd Improvement (DHI) production variables were determined on 60 farms. Of 60 dairy farmers participating, 51 were from Holstein farms (85%) and nine from farms with other breeds, primarily Jersey. Cows were milked either twice (n = 44 herds, 73%) or three times (n = 16) per day. Farmers were evenly split between the “E” and “I” dimension, whereas 93% of the farmers were “S,” 75% “T,” and 62% “J.”. Individuals with a preference for the “I” dimension were associated with higher peak and mature equivalent milk yield than those individuals with a preference for the “E” dimension. The “T” and “J” dimensions had a significantly higher percentage of the herd with records usable by USDA and a lower percentage of animals pregnant by the goal set by the dairy producer than the “F” and “P” dimensions. Herds managed by individuals with a combination preference of “E” and “P” produced 7 to 10kg of 3.5% FCM/cow per day less or 1820 to 2752 kg/cow RHA ECM less than other combinations of the “E-I” and “J-P” dimensions. Those herds also had longer days dry and a lower percentage of records usable by USDA, suggesting that the “E-P” preference is less favorably associated to those measures of herd performance. The MBTI had limited association with many DHI production variables, but relationships to measures of labor and business management should be examined.

Effect of Protein Level in Prepartum Diets on Metabolism and Performance of Dairy Cows

Multigravid Holstein cows (n = 75) were used in a randomized block design to evaluate the effect of prepartum diets formulated to supply surplus energy and incremental concentrations of protein on the nutritional status of dairy cows at parturition. Cows were blocked according to expected calving date and assigned to one of five diets: 9.7, 11.7, 13.7, 14.7, and 16.2% crude protein (CP). Dietary treatments were initiated 28 d before expected calving date and fed until parturition. A common diet was fed postpartum. Dry matter intake and milk yield were recorded daily through 90 d postpartum. Increasing the protein concentration from 9.7 to 14.7% of dry matter during the last 28 d of gestation improved responses of cows during lactation. Increasing dietary protein up to 14.7% also increased milk yield response to recombinant bovine somatotropin (rbST) during the ninth week of lactation and yields of 305-d 2× mature equivalent milk, milk protein, and milk fat. Plasma aspartate aminotransferase tended to be highest in cows fed 13.7 and 14.7% CP prepartum, but decreased linearly postpartum in response to dietary protein levels. There were no treatment differences for plasma insulin-like growth factor-1 (IGF-1) at d 60 postpartum (before rbST provision), but IGF-1 on d 90 (after rbST provision) was higher in plasma of cows fed 14.7% CP than the other diets except 13.7% CP. Close-up diets containing 13.7% CP and surplus energy produced the most beneficial outcomes during the subsequent lactation.

Genetic and phenotypic relationships among milk production and composition traits in primiparous Holstein cows in two different herd environments

Genotype by environment interactions for mature equivalent milk yield (MEM), mature equivalent protein yield (MEP), mature equivalent fat yield (MEF), protein percentage (P%), fat percentage (F%), and lactation mean somatic cell score (LMSCS) were studied using 248 230 first parity records of Holstein cows calving from 1987 to 1994, daughters of 588 sires in 3042 herds. Herds were classified into low and high yield environment classes. Genetic parameters were estimated with bivariate linear mixed models using the multiple trait derivative free software ( mtdfreml). For low yield environment herds, heritabilities for MEM, MEP, MEF, P%, F% and LMSCS were 0.22, 0.20, 0.23, 0.51, 0.58 and 0.11, while for high yield environment herds they were 0.30, 0.27, 0.27, 0.56, 0.56 and 0.09. All genetic correlations, except between MEM and P% and F%, were different in low and high yield environment herd classes. These results indicate that differences in management between the two herd environment classes modify the genetic expression of the traits studied and their genetic association. This suggests that, when these traits are considered in a selection index, appropriate weights for these traits depend on the herd environment class. These results also indicate that different correlated responses for MEP, MEF and LMSCS are expected in high relative to low yield environment herds when selection is based on MEM only.

The Effect of Left Displacement of Abomasum Corrected by Toggle-Pin Suture on Lactation, Reproduction, and Health of Holstein Dairy Cows

Our objectives were to evaluate the effect of left displacement of abomasum (LDA) after correction by toggle-pin suture (TPS) on lactation performance, reproduction and health in Holstein dairy cows in a commercial dairy farm. Cows diagnosed with LDA and corrected by the TPS procedure (188 cows) during the first 70 d postpartum were matched with control herdmates (186 controls) according to lactation number, calving date, and previous lactation 305-d mature equivalent milk yield. Cows were grouped according to parity and days in milk and fed the same total mixed ration throughout a 321-d lactation. Data collected included yields of milk and 3.5% fat-corrected milk (FCM), concentration and yields of milk fat, somatic cell count, incidence of mastitis, abortion, death and culling, in addition to reproductive measures. Cows affected with LDA corrected by the TPS procedure produced less milk and tended to produce less 3.5% FCM than control cows, but the decrease in production occurred only during the first 4 mo of lactation. Left displacement of abomasum did not affect the interval from calving to conception and conception rates, but it extended the period from calving to first postpartum artificial insemination. Incidences of abortions and mastitis were not influenced by LDA. Cows affected with LDA remained in the study for a shorter period than their control herdmates, and higher proportions of cows with LDA were sold or died. Death and culling were more pronounced immediately after the diagnosis of LDA and the TPS procedure.

Effect of lameness on milk yield in dairy cows.

To examine the relationship between lameness and milk yield in dairy cows. Cohort study. 531 dairy cows. Cows affected with lameness were classified into 1 of 3 groups on the basis of type of diseases or lesions observed, including interdigital phlegmon (foot rot), papillomatous digital dermatitis (foot warts), or claw lesions. Cows not affected with lameness were classified as healthy. From Dairy Herd Improvement Association records, 305-day mature equivalent milk yield data were collected at the end of lactation or when the cow left the herd. Milk yield was compared between cows affected with lameness and healthy cows. 167 (31%) cows were affected with lameness during lactation. Lame cows had claw lesions (60%), papillomatous digital dermatitis (31%), or interdigital phlegmon (9%). Milk yield in lame cows with interdigital phlegmon (mean, 17,122 lb) was significantly less, compared with healthy cows (19,007 lb). In this herd, interdigital phlegmon was associated with a 10% decrease in milk production. Lame cows with claw lesions or papillomatous digital dermatitis produced less milk than healthy cows, but the difference was not significant.

Persistent fecal Salmonella shedding in five dairy herds.

To monitor patterns of Salmonella fecal shedding in naturally infected dairy herds, determine the association between fecal shedding and individual animal production measures, and evaluate potential risk factors for shedding of Salmonella organisms among cattle in dairy herds. Longitudinal study. 5 Ohio dairy herds. For 3 herds, fecal samples were collected from all mature cows and unweaned calves 7 times during an 18-month period. For the remaining 2 herds, fecal samples were collected from 50 lactating cows 6 times during a 12-month period. Individual animal production records for 3 herds were used to examine associations between individual fecal Salmonella shedding status and 305-day mature-equivalent milk production, somatic cell count, milk fat content, and milk protein content. Multivariable logistic regression was used to test for associations between fecal shedding status and breed, lactation status, lactation number, and duration of lactation. None of the adult animals had clinical signs of salmonellosis, but prevalence of fecal Salmonella shedding at individual collection times ranged from 0 to 99% for cows and from 0 to 67% for unweaned calves. Mature cows were more likely to be shedding Salmonella organisms than were unweaned calves. Within herds, lactation status and duration of lactation for individual animals were associated with Salmonella shedding status. Salmonella fecal shedding status was not associated with individual cow production measures. Results suggest that subclinical fecal Salmonella shedding can persist in dairy herds for up to 18 months with no measurable effects on health or production of individual cows.

The Effect of Subclinical Mycobacterium paratuberculosis Infection on Milk Production in Michigan Dairy Cows

The objective of this study was to determine the effect of subclinical Mycobacterium paratuberculosis infection on mature equivalent milk, protein, and fat production in a sample of Michigan dairy herds with a history of cows positive for M. paratuberculosis diagnosed by fecal culture. A prospective two-group cohort study was conducted. Participating herds were tested, and productivity and reproduction records were monitored for 18 mo. All cows aged 24 mo and greater were tested for M. paratuberculosis infection using the ELISA and radiometric fecal culture (RFC) techniques. Using both tests in parallel, the overall sample apparent prevalence for M. paratuberculosis infection was 41.8%. Adjusting for diagnostic sensitivity and specificity resulted in a calculated sample true prevalence of 59.9%. Subclinical paratuberculosis test-positive status had no statistically significant effect on mature equivalent milk, fat, or protein production. The results of this study concur with the findings of other studies, reporting that the magnitude and direction of the association between subclinical paratuberculosis infection and milk production depends upon the parity of the animal, stage of disease, and the stage in lactation being monitored. Assessment of the impact of subclinical paratuberculosis on milk production must consider the average parity of the sample population. In herds that have an average parity of 2 or less, subclinical paratuberculosis infection may have little impact on milk production.

Relationships of Sire Predicted Transmitting Ability for Somatic Cell Score with Measures of Daughter Performance

The relationship between sire predicted transmitting ability (PTA) for somatic cell score (SCS) and occurrence of mastitis in daughters was characterized with 304 Holsteins first freshening since 1991 in the Virginia Tech dairy herd. No direct sire selection for PTA SCS was practiced in the herd. Linear regressions of first lactation average SCS (1.3), number of cases of mastitis (0.80), days clinical (7.0), and number of treatments for mastitis (2.0) on PTA SCS were significant. Linear regression coefficients for second and third lactations were generally positive, but like quadratic and cubic coefficients in this study, were not significant. Relationship of sire PTA SCS and measures of lifetime (84 mo opportunity) performance were determined for 2,494,195 Holsteins born between 1979 and 1987. Linear coefficients from regression on PTA SCS for number of lactations (−0.31), days of productive life (−87.0), total days in milk (−72.2), lifetime milk (−1609.1), fat (−80.7), and protein (−48.2) production, relative net income adjusted for opportunity cost for fluid markets (+13.47), first lactation average SCS (+1.00), and first lactation mature equivalent milk (+429.9) were different from zero. Partial regressions holding PTA milk or PTA protein constant were substantially larger than linear coefficients. When PTA productive life was held constant, the relationship between PTA SCS and measures of herd life and lifetime yield became positive, and relative net income adjusted for opportunity cost variables became moderately positive. One of the major expenses associated with higher susceptibility (higher PTA SCS) may be shorter herd life.

Heritabilities and Correlations Among Body Condition Scores, Production Traits, and Reproductive Performance

The objectives of this study were to estimate the heritability of body condition scores (BCS) from producer and consultant-recorded data and to describe the genetic and phenotypic relationships among BCS, production traits, and reproductive performance. Body condition scores were available at calving, postpartum, first service, pregnancy check, before dry off, and at dry off from the Dairy Records Management Systems in Raleigh, NC, through the PCDART program. Heritabilities, genetic correlations, and phenotypic correlations were estimated assuming an animal model using average information REML. Herd-year-season effects and age at calving were included in all models. Prior calving interval was included in models for second and third lactations. Analyses that included reproductive traits were conducted with and without mature equivalent milk as a covariable. Heritability estimates for BCS ranged from 0.09 at dry-off to 0.15 at postpartum in first lactation. Heritability estimates ranged from 0.07 before dry-off to 0.20 at pregnancy check in second lactation and from 0.08 before dry-off to 0.19 at first service in third lactation. Genetic correlations between adjacent BCS within first lactation were greater than 0.96 with the exception of calving and postpartum (0.74). In second lactation, adjacent genetic correlations were 1.0 with the exception of calving and postpartum (0.84). Genetic correlations across lactations were greater than 0.77. Phenotypic correlations between scoring periods were highest for adjacent scoring periods and when BCS was lowest. Phenotypic correlations were lower than genetic correlations, i.e., less than 0.70. Higher BCS during the lactation were negatively related to production, both genetically and phenotypically, but the relationship was moderate. Higher BCS were favorably related genetically to reproductive performance during the lactation.

Effect of Prepartum Dietary Protein Level on Performance of Primigravid and Multiparous Holstein Dairy Cows

This study compared the effects of two levels of crude protein (CP) fed during late gestation on the performance, blood metabolites, and ovarian activity of Holstein cows. One-hundred and six cows (42 primigravid and 64 multiparous) 32 d before calving were divided into two groups and fed diets containing moderate (12.7% CP, 36% rumen undegradable protein, (RUP) or high (14.7% CP, 40% RUP) protein. Higher prepartum CP diet increased milk production during the first 120 d in milk (DIM), but most of that effect was detected for the primigravid cows. Primigravid cows fed the prepartum diet higher in protein produced 2.0 kg/d more milk and 3.1 kg/d more 3.5% fat-corrected milk (FCM) during early lactation. Yields of milk fat and protein in early lactation were also increased by the high prepartum CP diet fed to primigravid cows. During the complete lactation, the response to prepartum dietary protein differed between primigravid and multiparous cows. Yields of milk, 3.5% FCM, and milk fat and protein were not affected by the prepartum diet for primigravid cows, but decreased for multiparous cows fed the high protein diet. However, primigravid cows fed the high prepartum protein diet had a higher 305-d mature equivalent milk yield. Colostrum composition, blood metabolites, ovarian activity, and disease incidence were not influenced by prepartum protein. Data from this study suggest that the current prepartum protein recommendation seems to be adequate for multiparous cows, but late-gestation primigravid cows might benefit from diets with a CP content above 12.7%.