Milk Yield In Early Lactation Research Articles

Epidemiology of subclinical ketosis in early lactation dairy cattle

The purpose of this study was to describe the epidemiology of subclinical ketosis (SCK) in dairy cows in early lactation and determine the association of (1) days in milk (DIM) at onset of SCK, and (2) blood β-hydroxybutyrate (BHBA) concentration at onset of SCK with development of displaced abomasum (DA) and removal from herd in the first 30 DIM, conception to first service, days to conception within 150 DIM, and early lactation milk yield. Cows from 4 freestall dairy herds (2 in New York and 2 in Wisconsin) were each tested 6 times for SCK from 3 to 16 DIM using the Precision Xtra meter (Abbott Laboratories, Abbott Park, IL). Subclinical ketosis was defined as a BHBA concentration of 1.2 to 2.9mmol/L. Mixed-effects multivariable Poisson regression was used to assess DA, removal from herd, and conception to first service. Semiparametric proportional hazards models were used to evaluate days to conception, and repeated-measures ANOVA was used to evaluate milk yield in the first 30 DIM. A total of 741 of 1,717 (43.2%) eligible cows had a least one BHBA test of 1.2 to 2.9mmol/L. Peak incidence of SCK occurred at 5 DIM, when 22.3% of cows had their first SCK-positive test. Peak prevalence of SCK occurred at 5 DIM, when 28.9% of cows had a SCK-positive test. Median time from first positive SCK test until BHBA test <1.2mmol/L was 5d. Cows first testing SCK positive from 3 to 5 DIM were 6.1 times more likely [95% confidence interval (CI) = 2.3 to 16.0] to develop a DA than cows first testing SCK positive at 6 DIM or later. Cows first testing SCK positive from 3 to 7 DIM were 4.5 times more likely (95% CI = 1.7 to 11.7) to be removed from the herd, were 0.7 times as likely (95% CI = 0.6 to 0.8) to conceive to first service, and produced 2.2kg less milk per day for the first 30 DIM than cows first testing positive at 8 DIM or later. Each 0.1mmol/L increase in BHBA at first SCK-positive test increased the risk of developing a DA by a factor of 1.1 (95% CI = 1.0 to 1.2), increased the risk of removal from herd by a factor of 1.4 (95% CI = 1.1 to 1.8), and was associated with a decrease in milk production by 0.5kg/d for the first 30DIM. These results show that time of onset and BHBA concentration of first SCK-positive test are important indicators of individual cow performance.

Prediction of 305-day milk yield in Brown Swiss cattle using artificial neural networks

Artificial neural networks (ANNs) have been shown to be a powerful tool for system modelling in a wide range of applications. In this paper, we focus on the capability of ANNs to predict 305-d milk yield in early lactation of Brown Swiss cattle, based on a few test-day records, and some environmental factors such as age, number of lactation and season of calving. The ANNs that were developed were compared with multiple linear regressions (MLR). The various ANNs were modelled and the best performing number of hidden layers, neurons and training algorithms retained. The best ANN model had input, hidden and output layers of tansig transfer function. The layers had 4, 8, and 1 neurons, respectively. It was determined that the mean predicted values calculated by the ANNs were closer to the real mean values without showing any statistical difference. On the other hand, the predicted mean values calculated by MLR and the real mean values were significantly different from each other. The best prediction in ANN method was seen in 1st, 2nd, 3rd, and 4th test-day records when these were recorded to the system as X1&#8210;X8 in the ANN system. In this study, the prediction of 305-d milk yield by ANN gave better results that those of MLR, suggesting that ANN can be used as an alternative prediction tool.Keywords: Prediction, milk yield, ANN, back propagation, test day records

Mechanism of Deoxyguanosine Kinase Inhibition by Nucleotide Derivatives: A Molecular Dynamic Approach

A study was conducted to investigate effect of prepartum supplementary feeding of free grazing Bunaji cows on the early lactation milk yield (MY) and interrelationships between the resulting milk constituents. Twenty cows, balanced for their weight and parity, were allocated to a completely randomized design, with five animals per treatment. The treatments were: A, range grazing (RG); B, RG + 100% corn bran (CB); C, RG + 60% CB + 40% palm kernel cake (PKC), and D, RG + 60% CB + 40% dried brewer's grains (DBG). W hereas milk yield was significantly (P 0.05) correlated to total solid (TS) and crude protein (CP) (r = -0.885; - 0.6989). Contrarily, insignificant (P > 0.05) but positive correlations existed between TS and CP (r = 0.8607), TS and lactose (r = 0.8554), CP and solids-not-fat (SNF) (r = 0.7677), lactose and CP (r = 0.6210) and MY and CP (= 0.560). There was a negative and highly significant (P < 0.01) correlation between MF and SNF (r = -0.9893) and MF and lactose (r = 0.9944). The relationships between TS and SNF and MF and gross energy were positive and highly significant (P < 0.01, r = 0.9962; 0.9459). However, MY and MF were significantly negatively related (P < 0.05, -0.9840). Prepartum supplementary feeding improved the milk yield of the grazing cows in the early lactation while both positive and negative relationships existed between milk constituents of the cows suggesting that the regression equations can be used to predict one milk constituent from the other.

Effects of nutrient supply, plasma metabolites, and nutritional status of sows during transition on performance in the next lactation1

The aim of the present study was to evaluate the effects of nutrient supply, plasma metabolites, and nutritional status of sows during the transition from gestation to lactation on performance of piglets during the colostral period and throughout lactation. Forty second-parity sows were fed 1 of 4 gestation diets containing a different quantity of dietary fiber (171 to 404 g/kg of DM) from mating until d 108 of gestation. From d 108 of gestation until weaning (d 28 of lactation), sows were fed 1 of 5 lactation diets with a different quantity of dietary fat [3 or 8% with different proportions of medium- (MCFA) and long-chain fatty acids (LCFA)]. Blood was obtained by jugular venipuncture on d 108 and 112 of gestation and on d 1 of lactation, and concentrations of plasma glucose, NEFA, lactate, acetate, propionate, butyrate, and fatty acids were analyzed. Piglet growth and mortality were noted throughout lactation. Piglet mortality during the colostral period (0 to 24 h) was affected by the lactation diets and was positively related to sow backfat (d 108) and plasma lactate (d 112) and negatively related to mean piglet birth weight (P < 0.05). Mean piglet live BW gain (LWG) was recorded in the periods 0 to 24 h, 7 to 10 d, 14 to 17 d, and 17 to 28 d relative to parturition as indirect measures of colostrum yield (0 to 24 h), milk yield in early lactation (d 7 to 10), and at peak lactation (d 14 to 17 and d 17 to 28). Effects of gestation and lactation diets on studied sow traits were tested on selected days during the transition period and the next lactation, and tested statistically on separate days. The LWG in the colostral period was positively correlated with mean piglet birth weight (P < 0.001), plasma concentrations of propionate and MCFA (P < 0.05), and plasma acetate and butyrate (P < 0.1) on d 1 of lactation. The LWG in early lactation was inversely correlated with plasma lactate on d 108 (P < 0.05), plasma glucose on d 112, and backfat thickness on d 108 (P < 0.10). The LWG at peak lactation was positively correlated with MCFA intake of the sow on d 113 to 115 and backfat thickness on d 108 during the transition, and negatively correlated with intake of LCFA and ME intake on d 108 to 112 (P < 0.05). In conclusion, feeding and body condition of sows during the transition from gestation to lactation is important for neonatal piglet survival, lactation performance of sows, and piglet growth during the next lactation.

Phenotypic and genetic variability of production traits and milk fatty acid contents across days in milk for Walloon Holstein first-parity cows

The objective of this study was to assess the phenotypic and genetic variability of production traits and milk fatty acid (FA) contents throughout lactation. Genetic parameters for milk, fat, and protein yields, fat and protein contents, and 19 groups and individual FA contents in milk were estimated for first-parity Holstein cows in the Walloon Region of Belgium using single-trait, test-day animal models and random regressions. Data included 130,285 records from 26,166 cows in 531 herds. Heritabilities indicated that de novo synthesized FA were under stronger genetic control than FA originating from the diet and from body fat mobilization. Estimates for saturated short- and medium-chain individual FA ranged from 0.35 for C4:0 to 0.44 for C8:0, whereas those for monounsaturated long-chain individual FA were lower (around 0.18). Moreover, de novo synthesized FA were more heritable in mid to late lactation. Approximate daily genetic correlations among traits were calculated as correlations between daily breeding values for days in milk between 5 and 305. Averaged daily genetic correlations between milk yield and FA contents did not vary strongly among FA (around −0.35) but they varied strongly across days in milk, especially in early lactation. Results indicate that cows selected for high milk yield in early lactation would have lower de novo synthesized FA contents in milk but a slightly higher content of C18:1 cis-9, indicating that such cows might mobilize body fat reserves. Genetic correlations among FA emphasized the combination of FA according to their origin: contents in milk of de novo FA were highly correlated with each other (from 0.64 to 0.99). Results also showed that genetic correlations between C18:1 cis-9 and other FA varied strongly during the first 100 d in milk and reinforced the statement that the release of long-chain FA inhibits FA synthesis in the mammary gland while the cow is in negative energy balance. Finally, results showed that the FA profile in milk changed during the lactation phenotypically and genetically, emphasizing the relationship between the physiological status of cow and milk composition.

Short communication: Metritis affects milk production and cull rate of Holstein multiparous and primiparous dairy cows differently

Metritis, a common transition disease in dairy cows, reduces milk production during the duration of the disease. To our knowledge, no work has investigated the short-term effects of metritis on feed intake and the long-term consequences on milk yield and risk of culling. The objectives were to determine the effect of metritis on 305-d lactation curves, dry matter intake (DMI), reproduction, and the probability of being culled. Identifying differences in response to metritis between primiparous and multiparous cows was of interest. Milk records were collected twice daily from Holstein cows diagnosed with puerperal metritis (11 primiparous and 16 multiparous) or classified as healthy (14 primiparous and 43 multiparous) during the first 3 wk after calving. Metritic cows were treated at the discretion of the herd veterinarian. Lactation curves of healthy and metritic cows were compared using a mixed model with a Wilmink function. Differences in DMI, days open, and the number of services per conception were assessed using mixed models. The probabilities that cows with and without metritis were not bred, were bred but never confirmed pregnant, or were culled were compared using Fisher's exact tests. Primiparous and multiparous animals were assessed separately. Multiparous cows with metritis produced less milk (35.1±1.5 vs. 39.2±1.0 kg/d), ate less during the 3 wk after calving (12.2±1.2 vs.14.0±0.8 kg/d), and were more likely to be culled (50.0%) than healthy cows (20.9%). The decision to cull was likely influenced by the lower milk yield in early lactation as a result of metritis; the decision to cull was made early, as 7 of the 8 culled metritic cows were not bred. No differences were found in any measurement between primiparous cows with and without metritis. These results indicate that metritis in early lactation has long-term effects on multiparous cows but not primiparous cows.

Milk yield persistency and its relationship with health problems in Holstein dairy cows supplemented with different levels of ruminally protected methionine and choline

Abstract. Forty Holstein dairy cows in their first and second lactation were used in a lactation study from 4-week prepartum through 14-week postpartum to investigate the potential effect of feeding different levels of ruminally protected methionine and choline on milk yield persistency of Holstein dairy cows. Cows were randomly assigned to receive one of the following treatments: 18 g/d of rumen-protected methionine (RPM), 60 g/d of rumenprotected choline (RPC), 18 g/d of RPM + 60 g/d of RPC, or neither supplement (control). The use of polynomial equations revealed that the polynomial coefficients of regression were closer (P&lt;0.05) to zero for RPM+RPC-fed cows than for other cows. Therefore, RPM+RPC-fed cows had a more persistent (P&lt;0.05) early-lactation milk yield than did other cows. Cows fed RPM+RPC had the lowest health problems compared with other groups. The treatments significantly affected actual milk yield (P&lt;0.05), 4 % fat-corrected milk (FCM) (P&lt;0.01) and energy-corrected milk (ECM) (P&lt;0.01) across lactation weeks. The treatments significantly affected average dry matter intake (DMI) for the first 14 week postpartum (P&lt;0.05). Also, treatments significantly affected lactose percentage of milk across lactation weeks (P&lt;0.01). In general, it was expected that RPM+RPC-fed cows with greater persistency of lactation would be healthier because the incidence of metabolic and reproductive disorders and negative energy balance that originate from the physiological stress of high milk yield would be lower.

Genetic analysis of reproductive disorders and their relationship to fertility and milk yield in Austrian Fleckvieh dual-purpose cows

The objective of this study was to estimate genetic parameters for various reproductive disorders based on veterinary diagnoses for Austrian Fleckvieh (Simmental) dual-purpose cattle. The health traits analyzed included retained placenta, puerperal diseases, metritis, silent heat and anestrus, and cystic ovaries. Three composite traits were also evaluated: early reproductive disorders, late reproductive disorders, and all reproductive disorders. Heritabilities were estimated with logit threshold sire, linear sire, and linear animal models. The threshold model estimates for heritability ranged from 0.01 to 0.14, whereas the linear model estimates were lower, ranging from 0.005 to 0.04. Rank correlations among random effects of sires from linear and threshold sire models were high (>0.99), whereas correlations between any sire model (linear, threshold) and the linear animal model were lower (0.88–0.92). Genetic correlations among reproductive disorders, fertility traits, and milk yield were estimated with bivariate linear animal models. Fertility traits included interval from calving to first insemination, nonreturn rate at 56 d, and interval between first and last insemination. Milk yield was calculated as the mean from test-day 1 and test-day 2 after calving. Estimated genetic correlations were 1 among metritis, retained placenta, and puerperal diseases and 0.85 between silent heat–anestrus and cystic ovaries. Low to moderate correlations (−0.01 to 0.68) were obtained among the other disorders. Genetic correlations between reproductive disorders and fertility traits were favorable, whereas antagonistic relationships were observed between milk yield in early lactation and reproductive disorders. Pearson correlations between estimated breeding values for reproductive disorders and other routinely evaluated traits were computed, which revealed noticeable favorable relationships to longevity, calving ease maternal, and stillbirth maternal. The results showed that data from the Austrian health monitoring project can be used for genetic selection against reproductive disorders in Fleckvieh cattle.

Effect of three forages and two forage allowances offered to pregnant dry dairy cows in winter on periparturient performance and milk yield in early lactation

AbstractSixty multiparous, Holstein–Friesian pregnant dry dairy cows were allocated to three forage treatments (n = 20; fodder beet, kale or grass silage) at two feeding allowances (n = 30; high and low) for 70 (s.e. of mean, 16) d before parturition. Cows offered the high feeding allowance were offered 9 kg of dry matter (DM) of kale or fodder beet grazed in situ plus 5 kg DM of baled grass silage daily or clamp grass silage ad libitum offered indoors. Cows offered the low feeding allowance were offered 6 kg DM of kale or fodder beet grazed in situ plus 3·5 kg DM baled grass silage daily, or 9·5 kg DM of clamp grass silage daily offered indoors. After calving, all cows received a daily allowance of 14 kg DM perennial ryegrass herbage at pasture plus 4 kg concentrate cow−1 for the first 35 d of lactation. Cows offered grass silage had a greater increase in body condition score pre‐partum compared to those offered kale or fodder beet. Cows offered fodder beet pre‐partum had a greater milk solid and solids‐corrected milk yield in the first 35 d of lactation than those offered kale and grass silage pre‐partum. Offering fodder beet and kale pre‐partum increased plasma non‐esterified fatty acid concentrations pre‐partum relative to offering grass silage. Offering kale pre‐partum resulted in higher insulin‐like growth factor‐1 concentration post‐partum but lower plasma copper concentration pre‐partum and at calving than kale or grass silage. Offering the higher forage allowance pre‐partum resulted in a higher plasma calcium concentration at calving and higher plasma non‐esterified fatty acid concentration post‐partum.

Effects of the administration of ketoprofen at parturition on the milk yield and fertility of Holstein-Friesian cattle

A total of 220 cows and heifers were treated with 3 mg/kg ketoprofen immediately after calving and 24 hours later, and 227 were left untreated as controls. The treated animals...

Impact of hyperketonemia in early lactation dairy cows on health and production

Data from 1,010 lactating lactating, predominately component-fed Holstein cattle from 25 predominately tie-stall dairy farms in southwest Ontario were used to identify objective thresholds for defining hyperketonemia in lactating dairy cattle based on negative impacts on cow health, milk production, or both. Serum samples obtained during wk 1 and 2 postpartum and analyzed for β-hydroxybutyrate (BHBA) concentrations that were used in analysis. Data were time-ordered so that the serum samples were obtained at least 1 d before the disease or milk recording events. Serum BHBA cutpoints were constructed at 200μmol/L intervals between 600 and 2,000μmol/L. Critical cutpoints for the health analysis were determined based on the threshold having the greatest sum of sensitivity and specificity for predicting the disease occurrence. For the production outcomes, models for first test day milk yield, milk fat, and milk protein percentage were constructed including covariates of parity, precalving body condition score, season of calving, test day linear score, and the random effect of herd. Each cutpoint was tested in these models to determine the threshold with the greatest impact and least risk of a type 1 error. Serum BHBA concentrations at or above 1,200μmol/L in the first week following calving were associated with increased risks of subsequent displaced abomasum [odds ratio (OR)=2.60] and metritis (OR=3.35), whereas the critical threshold of BHBA in wk 2 postpartum on the risk of abomasal displacement was ≥1,800μmol/L (OR=6.22). The best threshold for predicting subsequent risk of clinical ketosis from serum obtained during wk 1 and wk 2 postpartum was 1,400μmol/L of BHBA (OR=4.25 and 5.98, respectively). There was no association between clinical mastitis and elevated serum BHBA in wk 1 or 2 postpartum, and there was no association between wk 2 BHBA and risk of metritis. Greater serum BHBA measured during the first and second week postcalving were associated with less milk yield, greater milk fat percentage, and less milk protein percentage on the first Dairy Herd Improvement test day of lactation. Impacts on first Dairy Herd Improvement test milk yield began at BHBA ≥1,200μmol/L for wk 1 samples and ≥1,400μmol/L for wk 2 samples. The greatest impact on yield occurred at 1,400μmol/L (−1.88kg/d) and 2,000μmol/L (−3.3kg/d) for sera from the first and second week postcalving, respectively. Hyperketonemia can be defined at 1,400μmol/L of BHBA and in the first 2 wk postpartum increases disease risk and results in substantial loss of milk yield in early lactation.

Genetic Association of Clinical Mastitis with Test-Day Somatic Cell Score and Milk Yield During First Lactation of Finnish Ayrshire Cows

In this study the genetic association during lactation of 2 clinical mastitis (CM) traits: CM1 (7 d before to 30 d after calving) and CM2 (31 to 300 d after calving) with test-day somatic cell score (SCS) and milk yield (MY) was assessed using multitrait random regression sire models. The data analyzed were from 27,557 first-lactation Finnish Ayrshire cows. Random regressions on second- and third-order Legendre polynomials were used to model the daily genetic and permanent environmental variances of test-day SCS and MY, respectively, while only the intercept term was fitted for CM. Results showed that genetic correlations between CM and the test-day traits varied during lactation. Genetic correlations between CM1 and CM2 and test-day SCS during lactation varied from 0.41 to 0.77 and from 0.34 to 0.71, respectively. Genetic correlations of test-day MY with CM1 and CM2 ranged from 0.13 to 0.51 and from 0.49 to 0.66, respectively. Correlations between CM1 and SCS were strongest during early lactation, whereas correlations between CM2 and SCS were strongest in late lactation. Genetic correlations lower than unity indicate that CM and SCS measure different aspects of the trait mastitis. Milk yield in early lactation was more strongly correlated with both CM1 and CM2 than milk yield in later lactation. This suggests that selection for higher lactation MY through selection on increased milk yield in early lactation will have a more deleterious effect on genetic resistance to mastitis than selection for higher yield in late lactation. The approach used in this study for the estimation of the genetic associations between test-day and CM traits could be used to combine information from traits with different data structures, such as test-day SCS and CM traits in a multitrait random regression model for the genetic evaluation of udder health.

Effect of Increased Milking Frequency in Early Lactation With or Without Recombinant Bovine Somatotropin

Multiparous Holstein cows (n=300) were assigned to 1 of 2 milking frequency treatments at parturition. Cows were either milked 6 times (6×) or 3 times (3×) daily to determine effects on early lactation milk yields and subsequent lactation persistency with or without use of recombinant bST (rbST). Treatments included a control group milked 3× and 3 groups milked 6× for either the first 7, 14, or 21 days in milk (DIM). Those 4 groups of cows all received rbST starting at 63 DIM. The fifth treatment group was also milked 6× for the first 21 DIM but those cows received no rbST during the entire lactation. All cows returned to 3× milking after their respective treatment periods ended. Cows milked 3× tended to produce more milk (43.2 vs. 41.5 and 41.0±1.1kg/d) during the first 9 wk of lactation compared with cows milked 6× for 7 or 21 DIM, respectively. Group milk yields after wk 9 averaged 38.3±0.7kg/d and did not differ among various groups assigned to an increased milking frequency in early lactation. Percentages of milk fat (3.8±0.12%) and protein (2.9±0.06%) did not differ among treatments during the first 9 wk after calving. Early lactation milk yield (41.9±1.2kg/d) did not differ between the 2 groups of cows milked 6× for 21 DIM. However, cows subsequently administered rbST (at 63 DIM) produced more milk (38.8 vs. 34.2±0.9kg/d) from wk 10 to 44. The number of cows sent to the hospital during the 305-d trial for mastitis (97), digestive disorders (14), respiratory issues (9), lameness (22), or retained placenta (16), were not affected by treatments (χ2=0.49). Under the conditions of this commercial dairy herd in Arizona, increasing milking frequency to 6 times daily for 7 to 21 d at the start of lactation conditions did not increase milk yield nor improve lactation persistency.

Effect of Pregnancy and Extended Lactation on Milk Production in Dairy Goats Milked Once Daily

Thirty multiparous Murciano-Granadina dairy goats milked once daily were used to study the lactational effects of an extended 24-mo kidding interval (K24; n=14) compared with the traditional 12-mo kidding interval (K12; n=16). Goats were divided into 2 groups at wk 29 of lactation balanced with respect to parity, milk yield, and somatic cell count. Over a period of 92 wk, K12 goats were mated twice, at wk 29 during the first lactation and at wk 79 during the second lactation, whereas K24 goats were mated once, at wk 79 of extended first lactation. The K12 goats were dried off from wk 14 to 21 of pregnancy (wk 43 to 50 of lactation). Milk yield was recorded from wk 2 to 92, and milk composition was studied from wk 29 to 92. Milk fatty acids were analyzed in milk samples taken at wk 39 (wk 10 of pregnancy) and 55 (wk 5 of subsequent lactation), when milk in udder compartments (cisternal and alveolar) was also evaluated. Average milk yield during the first 29 wk was 2.23±0.13L/d. Pregnancy reduced milk yield in K12 goats from wk 39 to 42 of lactation compared with K24 goats. During the dry period for K12 goats, milk yield of K24 goats averaged 1.53±0.10L/d. From wk 51 to 79, K12 goats produced 32% more milk than did K24 goats, but their milk contained lower fat and protein than that of K24 goats. No changes were detected for milk lactose and somatic cell count from wk 51 to 79. From wk 80 to 92, differences in milk yield and milk composition between groups were not significant. Milk of pregnant K12 goats contained higher C16:1 and conjugated C18:2 fatty acids, and had a higher desaturase index than milk of open K24 goats at wk 39. In the following lactation (wk 55), milk of K12 goats contained higher C18:2 and C18:3, and lower C16:0 fatty acids, resulting in a lower atherogenicity index compared with K24 goats. Cisternal milk at wk 39 was lower for K12 than K24 goats, whereas alveolar milk did not differ. In K12 goats, values of cisternal milk tripled, but alveolar milk only doubled at wk 55 (wk 5 of subsequent lactation) compared with wk 39, indicating the importance of the cistern in accommodating high milk yield in early lactation. Values of cisternal and alveolar milk did not differ between wk 39 and 55 for K24 goats. Fat content was higher for alveolar milk than cisternal milk for K12 goats at wk 55 and for K24 goats at wk 39 and 55. No differences in milk protein or lactose were detected between cisternal and alveolar milk. In conclusion, pregnancy reduced milk yield from wk 10 after conceiving onwards. Extended lactation did not significantly decrease milk yield (−8.2%), but increased milk components that may contribute to cheese yield, and may be a useful strategy for reducing metabolic stress in early lactation and for simplifying herd management in dairy goats.

Genetic Parameters of Claw and Foot Disorders Estimated with Logistic Models

The primary aim of this study was to estimate heritabilities for different types of claw and foot disorders and the genetic relationship of disorders with milk yield and selected conformation traits by applying logistic models in Holstein dairy cattle. The study included data from 5634 Holstein cows kept on large-scale dairy farms in Eastern Germany. Dichotomous response variables were the presence or absence of the disorder in 2003. Cows that were present in herds for <6 wk in 2003 were excluded from the analysis. Incidences, disregarding repeated measurements, for digital dermatitis (DD), sole ulceration (SU), wall disorder (WD), and interdigital hyperplasia (IH) in rear legs were 13.2, 16.1, 9.6, and 6.3%, respectively. The herd effect was highly significant for all disorders. Incidences increased with increasing parities for SU and WD, but were highest among heifers for DD. High milk yield at the first 2 test d after calving was associated with a greater risk for claw and foot disorders in the same lactation. Estimates of heritability were 0.073 for DD, 0.086 for SU, 0.104 for WD, and 0.115 for IH. Genetically, health problems appear to occur in clusters (i.e., a cow showing one disease has an increased genetic risk of showing another claw disease). This phenomenon was also observed between claw and foot disorders and the somatic cell score. Genetic correlations between milk yield in early lactation and disorders were 0.240 for DD, 0.057 for SU, 0.270 for WD, and 0.336 for IH, indicating a physiological antagonism. Correlations between breeding values for claw and foot disorders of bulls and official breeding values for functional type traits were mostly favorable. Routine recording of claw data will offer a new chance to improve claw health within the population as was elaborated by different scenarios applying selection index procedures.

Genetic Parameters for Body Condition Score, Body Weight, Milk Yield, and Fertility Estimated Using Random Regression Models

Genetic (co)variances between body condition score (BCS), body weight (BW), milk yield, and fertility were estimated using a random regression animal model extended to multivariate analysis. The data analyzed included 81,313 BCS observations, 91,937 BW observations, and 100,458 milk test-day yields from 8725 multiparous Holstein-Friesian cows. A cubic random regression was sufficient to model the changing genetic variances for BCS, BW, and milk across different days in milk. The genetic correlations between BCS and fertility changed little over the lactation; genetic correlations between BCS and interval to first service and between BCS and pregnancy rate to first service varied from −0.47 to −0.31, and from 0.15 to 0.38, respectively. This suggests that maximum genetic gain in fertility from indirect selection on BCS should be based on measurements taken in midlactation when the genetic variance for BCS is largest. Selection for increased BW resulted in shorter intervals to first service, but more services and poorer pregnancy rates; genetic correlations between BW and pregnancy rate to first service varied from −0.52 to −0.45. Genetic selection for higher lactation milk yield alone through selection on increased milk yield in early lactation is likely to have a more deleterious effect on genetic merit for fertility than selection on higher milk yield in late lactation.

Genetic parameters and evaluations from single- and multiple-trait analysis of dairy cow fertility and milk production

Genetic parameters and breeding values for dairy cow fertility were estimated from 62 443 lactation records. Two-trait analysis of fertility and milk yield was investigated as a method to estimate fertility breeding values when culling or selection based on milk yield in early lactation determines presence or absence of fertility observations in later lactations. Fertility traits were calving interval, intervals from calving to first service, calving to conception and first to last service, conception success to first service and number of services per conception. Milk production traits were 305-day milk, fat and protein yield. For fertility traits, range of estimates of heritability ( h 2) was 0.012 to 0.028 and of permanent environmental variance ( c 2) was 0.016 to 0.032. Genetic correlations ( r g) among fertility traits were generally high (>0.70). Genetic correlations of fertility with milk production traits were unfavourable (range −0.11 to 0.46). Single and two-trait analyses of fertility were compared using the same data set. The estimates of h 2 and c 2 were similar for two types of analyses. However, there were differences between estimated breeding values and rankings for the same trait from single versus multi-trait analyses. The range for rank correlation was 0.69–0.83 for all animals in the pedigree and 0.89–0.96 for sires with more than 25 daughters. As single-trait method is biased due to selection on milk yield, a multi-trait evaluation of fertility with milk yield is recommended.

Effects of dietary tallow level on performance of Alpine does in early lactation

Sixty Alpine does (initial BW 47±1.3 kg) were used to determine effects of dietary inclusion of different levels of partially hydrogenated tallow on performance in early lactation (weeks 3–11). Treatments entailed a 30% concentrate, negative control (NC) diet and five diets higher in concentrate (42–46%) with 0, 1.5, 3.0, 4.5 or 6.0% DM of partially hydrogenated tallow (0T, 1.5T, 3.0T, 4.5T and 6.0T, respectively). DM intake was 1.54 kg per day for the NC and 1.86, 1.80, 1.99, 2.17 and 1.96 kg per day for the five tallow treatments, respectively, BW was similar among treatments and increased as the trial progressed (47.4, 48.4, 49.8, 50.4, 50.8 and 51.3 kg at weeks 3, 5, 7, 9, 11 and 13, respectively). Milk yield was lower ( P<0.05) for NC (2.61 kg per day) compared with the mean of the other diets and changed quadratically ( P<0.05) as tallow level increased (2.85, 3.08, 3.14, 3.21 and 2.69 kg per day for the five tallow treatments, respectively). Milk fat concentration was lower ( P<0.05) for NC (2.94%) than for the mean of other diets and increased linearly ( P<0.05) with increasing tallow level (3.00, 3.17, 3.34, 3.48 and 3.58%) whereas, milk protein concentration was not affected by level of tallow (2.72, 2.80, 2.93, 2.85, 2.90 and 2.90% for NC, and the five tallow treatments, respectively). The estimated NE l:4% fat-corrected milk yield ratio was 0.93 Mcal/kg for NC and 1.30, 1.11, 1.21, 1.37 and 1.44 Mcal/kg for the five tallow treatments, respectively. The results indicated that in Alpine does, milk yield in early lactation increased as dietary tallow level was increased to 3 and 4.5% but decreased when the level was increased to 6%, although milk fat concentration increased linearly and the protein level was unchanged. These results suggest beneficial usage by lactating Alpine does of low to moderate levels of partially hydrogenated tallow in diets moderate in concentrate level, although ingredient availability and costs will influence ultimate dietary ingredient decisions.

Effects of Dietary Levels of Forage and Ruminally Undegraded Protein on Early Lactation Milk Yield by Alpine Does and Doelings

Goetsch, A.L., Puchala, R., Lachica, M., Sahlu, T. and Dawson, L.J. 2000. Effects of dietary levels of forage and ruminally undegraded protein on early lactation milk yield by Alpine does and doelings. J. Appl. Anim. Res., 18: 49–60. Thirty-one Alpine does and 31 doelings (52±1.62 and 34±0.86 kg initial body weight, respectively) were used to determine effects of dietary levels of forage and ruminally undegraded protein (RUP) and change in forage level on early lactation performance. Goats began a 2-week covariate period at 3–9 days after parturition, then were assigned to treatments: 80 = 80% forage diet; 80R = 80 with added RUP; 40 = 40% forage diet; 40R = 40 with RUP added; 40–80 = 80 in weeks 1–3, transition to 40 in weeks 4–5 and 40 in weeks 6–16; and 80R-40R-80R in weeks 1–3, transition to 40R in weeks 4–5 and 40R in weeks 6–16. Diets were 18–19% crude protein (dry matter basis);for 80R and 40R, equal crude protein was supplied by blood, fish and feather meals, substituting for approximately two-thirds of soybean meal protein. Milk yield was greater (P<0.05) for 40 and 40R than for 80 and 80R, and was influenced (P<0.05) by RUP in weeks 1–3 and 4–5 (weeks 1–3: 2.51, 2.74, 2.72, 3.33, 2.44 and 2.54 kg/day; weeks 4–5: 2.52, 2.73, 3.13, 3.59, 2.56 and 2.62 kg/day; weeks 6–16: 2.18, 2.33, 2.85, 3.11, 2.54 and 3.01 kg/day for 80, 80R, 40, 40R, 80–40 and 80R-40R, respectively). Milk protein concentration was greater (P<0.05) for 40 and 40R than for 80 and 80R (e.g., week 5: 2.81, 2.72, 2.91, 2.86, 2.76 and 2.94% for 80, 80R, 40, 40R, 80–40 and 80R-40R, respectively). In conclusion, milk yield- in a 16-week early lactation period was greater with 40 vs 80% forage, although RUP impacted milk yield only early in the experiment. Changing dietary forage level in early lactation of dairy goats did not influence subsequent production.

The application of event-time regression techniques to the study of dairy cow interval-to-conception

This paper explains the use of event-time techniques, also known as survival analysis, to assess a relationship involving dairy cows: the effect of early lactation milk yield on the interval from calving to subsequent conception. Possible confounding factors, such as disease history, parity, calving season, and herd production level, were controlled by their inclusion in the model equations. Both Cox proportional hazards regression models and Weibull regression models were employed, with similar results, indicating that a Weibull distribution may be a good approximation of the distribution of conception times in dairy cattle.