Analysis of water intake and dry matter intake using different lactation curve models

The objective was to evaluate 6 different lactation curve models for daily water and dry matter intake. Data originated from the Futterkamp dairy research farm of the Chamber of Agriculture of Schleswig-Holstein in Germany. A data set of about 23,000 observations from 193 Holstein cows was used. Average daily water and dry matter intake were 82.3 and 19.8 kg, respectively. The basic linear mixed model included the fixed effects of parity and test-day within feeding group. Additionally, 6 different functions were tested for the fixed effect of lactation curve and the individual (random) effect of cow-lactation curve. Furthermore, the autocorrelation between repeated measures was modeled with the spatial (power) covariance structure. Model fit was evaluated by the likelihood ratio test, Akaike's and Bayesian information criteria, and the analysis of mean residual at different days in milk. The Ali and Schaeffer function was best suited for modeling the fixed lactation curve for both traits. A Legendre polynomial of order 4 delivered the best model fit for the random effect of cow-lactation. Applying the error covariance structure led to a significantly better model fit and indicated that repeated measures were autocorrelated. Generally, the best information criteria values were yielded by the most complex model using the Ali and Schaeffer function and Legendre polynomial of order 4 to model the average lactation and cow-specific lactation curves, respectively, with inclusion of the spatial (power) error covariance structure. This model is recommended for the analysis of water and dry matter intake including missing observations to obtain estimation of correct statistical inference and valid variance components.     

Toxoplasma infection and milk consumption: Meta-analysis of assumptions and evidences

Toxoplasmosis is the most widespread infection worldwide. It occurs within congenital contamination, organ transplant or immune system depression. Primary infection is mainly foodborne with the ingestion of raw or undercooked meat, unwashed fruit-vegetables, unhygienic water or contaminated milk. Gaps in current knowledge about the risk assessment of Toxoplasma gondii by milk consumption are noted. Contradictory data are observed within risk assessment of milk consumption and toxoplasmosis occurrence. While some papers reported positive correlations between drinking milk and infection transmission to human, other studies stated nonsignificant influence of milk or milk products consumption. New debate about the detection of the parasite in the milk matrix from different hosts raised interrogations. To figure out the real contribution and the potential correlations of milkborne way in toxoplasmic infection, meta-analysis approach was investigated. Overall analysis showed heterogeneous responses and led to state that statistically dairy matrix (other than milk), Bovidae products, agricultural population and countries in Africa, Europe and Southeast Asia are not linked to milkborne toxoplasmosis. The most involved factors are Capridae products, immune-depressed population and North America, Middle East, and Latin territories. The current work advanced those parameters that could affect the public health and should be envisioned in further epidemiological analysis.     

The effect of milk-feeding method and hay provision on the development of feeding behavior and non-nutritive oral behavior of dairy calves

We investigated the interactive effects of common feeding management factors on the development of feeding and non-nutritive oral behaviors in preweaned calves through the weaning transition. Calves were randomly assigned to 1 of 3 treatments that differed by milk-feeding method (teat or bucket) and ad libitum access to chopped timothy hay: control, milk provided by bucket and no access to hay (CON; n = 10); milk provided by bucket and access to hay (H; n = 10); milk provided via a teat and access to hay (TH; n = 10). Calves had ad libitum access to concentrate and water, and were fed 6 L/d of pasteurized waste milk, divided into 2 meals. All calves were weaned by removing the second milk meal for 9 ± 2 d, beginning at 36 d of age. Daily concentrate and hay intake were recorded, and calves were weighed weekly to measure growth. We recorded the behavior of all calves using 2 s time-lapse video during time periods that encompassed milk meals, from 6000 h to 1000 h and 1600 h to 2000 h, on 2 consecutive focal days in wk 2 and 4. We continuously monitored lying time and activity using electronic data loggers. During the preweaning period, hay selection by H and TH calves was subject to a treatment × week interaction, with TH calves increasing hay intake to a greater extent over time. Similarly, we observed a tendency for a treatment × week interaction for hay dry matter intake. Before weaning, concentrate intake was subject to a treatment × week interaction, increasing to a greater extent over time for H and TH calves, but was greater overall for CON calves. As predicted, milk-feeding method and hay provision influenced the proportion of time devoted to feeding and non-nutritive behaviors. The CON calves spent the greatest amount of time performing non-nutritive sucking directed at the pen, TH calves the least, and H calves intermediate amounts. Considering the time TH calves sucked on their teat when milk was not present in addition to the time they spent sucking on pen fixtures, the total amount of time spent performing sucking behavior was similar between treatments. Although intake was similar across the weaning transition, CON calves had greater average daily gain than H calves, and TH calves were intermediate. Providing access to hay and milk via a teat during the milk-feeding stage decreased non-nutritive oral behaviors and influenced feeding behavior.     

Ability of dairy cows to ensure pregnancy according to breed and genetic merit for production traits under contrasted pasture-based systems

The present study aimed to assess and measure the effects of breed, genetic merit for production traits, and feeding systems (FS) on the ability of dairy cows to ensure pregnancy through its components (fertilization, embryonic losses, recalving). An experiment was conducted over 9 yr on Normande and Holstein cows assigned to contrasted FS. Diets were based on maize silage in winter and grazing plus concentrate in spring in the high FS group, and on grass silage in winter and grazing with no concentrate during spring in the low FS group. Within breeds, cows were classified into 2 groups with similar estimated breeding values (EBV) for milk solids: cows with high EBV for milk yield were included in a milk group and those with high EBV for fat and protein contents were included in a content group. Holstein cows produced more milk throughout lactation than Normande cows (the differential was greater in the high FS group, +2,294 kg, compared with +1,280 kg in the low FS group) and lost more body condition to nadir (the differential was greater in the high FS group, ?1.00 point, compared with ?0.80 point in the low FS group). Within breeds, milk solids production was similar between genetic groups. Cows in the high FS group produced more milk (+2,495 kg for Holstein and +1,481 kg for Normande cows) and had a higher body condition score at nadir (+0.40 point for Holstein and +0.60 point for Normande) than cows in the low FS group. Holstein cows had a lower recalving rate than Normande cows (?19 percentage units). We found no effect of genetic group and FS on fertility of Normande cows. However, according to FS, Holstein cows in the content group exhibited different fertility failure patterns. In the low FS group, Holstein cows in the content group had more nonfertilizations or early embryo mortality (+26 percentage units at first and second services) than Holstein cows in the milk group. In the high FS group, Holstein cows in the content group had a higher proportion of late embryo mortality than in the milk group (+10 percentage units at first and second services). We observed no effect of FS on recalving rate; however, indicators of energy balance (protein content or body condition score) were positively associated with successful conception and pregnancy. This suggested a link between genetic merit for fat and protein content and lower ability of dairy cows to ensure pregnancy because of more nonfertilizations and early or late embryo mortality.     

Short communication: Repeatability of measures of rectal temperature in dairy cows

Although taking body temperature by rectal thermometer is the method most commonly used to identify sick cows in the postpartum period, no data on the repeatability of this measure are available. The overall objective of this study was to evaluate variability of rectal temperatures in dairy cows considering different factors (intra- and interinvestigator repeatability, different thermometers, penetration depth into the rectum, and defecation). High coefficients of correlation (r = 0.98) and small differences between values of rectal temperatures (observer A = 39.3 ± 1.0°C and observer B = 39.4 ± 1.0°C) provide evidence that rectal temperature was a repeatable measure in dairy cows. Testing was carried out using 4 different digital thermometers: GLA M750 (GLA Agricultural Electronics, San Luis Obispo, CA), MTI8101 (SES Scala Electronics, Stahnsdorf, Germany), MT1831 (Microlife AG, Widnau, Switzerland) and Domotherm TH1 (Uebe Medical GmbH, Wertheim, Germany). Thermometers were inserted into the rectum to a certain depth (GLA M750 and MTI8101 = 11.5 cm; MT1831 = 8.4 cm; Domotherm TH1 = 7.7 cm) and a measure was finished when a visual or acoustic signal was emitted by the thermometer. The measures could be influenced by the procedure itself (up to 0.5°C), type of thermometer (up to 0.3°C), and the penetration depth (11.5 cm or 6.0 cm in one of the experiments) into the rectum (up to 0.4°C difference between a penetration depth of 11.5 cm and 6.0 cm in one of the experiments). Differences in rectal temperature before and after defecation were minor (<0.1°C). These results indicate that some care is required in generalizing rectal measures of body temperature.     

Mammary pathogens and their relationship to somatic cell count and milk yield losses in dairy ewes

A total of 9592 samples of half udder milk were collected monthly throughout lactation for bacteriological and somatic cell count (SCC) study from 1322 Churra ewe lactations from seven separate flocks enrolled in the recording scheme of the National Association of Spanish Churra Breeders in the Castile-Le6n region of Spain. Statistical analyses were carried out from a mixed model with random factor half udder or ewe for repeated measures. Test of significance of fixed effects of this mixed model showed significant effects of organisms, flock, parity, lactation stage, and birth type on SCC. Special reference must be made to novobiocin-sensitive coagulase-negative staphylococci, which represented more than 50% of the isolates and which elicited SCC geometric means of around 106/ml. In addition, the analysis of 4352 monthly test-day records for milk yield, SCC, and bacteriology showed that the ewes that were uninfected and infected by minor pathogens had the lowest SCC and the highest milk yields, whereas those infected by major pathogens had high SCC and milk yield losses between 8.8 and 10.1% according to the uni- or bilateral character of the infection. Finally, ewes infected by novobiocin-sensitive coagulase-negative staphylococci elicited SCC values similar to those of infections by major pathogens and milk yield losses ranging between those caused by minor and major pathogens. As a result, emphasis should be put on prevention of subclinical mastitis, particularly mastitis caused by novobiocin-sensitive coagulase-negative staphylococci in dairy sheep herds to improve microbiological and hygienic milk quality and to minimize losses in milk yield.     

Effect of casein infusion in the rumen,duodenum or both sites on factors affecting forage intake and performance of dairy cows fed red clover-grass silage

Four lactating dairy cows were used in a balanced 4 x 4 Latin square design to examine the effects of casein infusion in the rumen, duodenum, or both on the intake of red clover-grass silage, chewing behavior, diet digestion, microbial protein synthesis, rumen fermentation, digestion, and passage kinetics, milk production, and milk composition. Duodenal infusion increased eating time, silage intake, rumen neutral detergent fiber pool, yields of milk, protein, and lactose, and concentration of milk protein, and tended to decrease that of milk fat. Ruminal infusion tended to decrease eating time, and increased significantly microbial protein synthesis, rumen ammonia-N concentration, molar proportions of isovalerate and valerate, digestion rate of digestible neutral detergent fiber, passage rate of indigestible neutral detergent fiber, and milk urea content, and decreased rumen neutral detergent fiber pool. Silage intake, and yields of milk, protein, and lactose were highest when casein was simultaneously infused in both sites.     

An autoregressive repeatability animal model for test-day records in multiple lactations

Test-day (TD) models are becoming a standard for genetic evaluation of production traits in dairy cattle. Various approaches to model covariances between TD records include random regression, autoregressive repeatability, orthogonal polynomials, and models based on character processing. The applicability of these models is mainly associated with the number of parameters to estimate, incorporation of multiple lactations, and the accuracy of correlations generated by the cow's repeated expression of milking performance (TD yields) within and across lactations. We define and evaluate a multiple-lactation, autoregressive-repeatability model that disentangles environmental effects due to cow within and between lactations. Simulated records either included or ignored a long-term environmental effect between lactations. Our autoregressive TD animal model correctly detected presence and the absence of this effect and accurately recovered the assumed variance components and correlations underlying the data (10 parameters for three lactations). Estimates of variance components and autocorrelation coefficients were obtained using DFREML-simplex methodology. Given the value of this approach to reduce the size of residual variance components, autoregressive animal models are a preferable alternative to classical methods based on cumulative lactation yield to improve milk production in dairy cattle.     

The effect of a ruminal nitrogen (N) deficiency in dairy cows: evaluation of the cornell net carbohydrate and protein system ruminal N deficiency adjustment

Twenty-four multiparous and fifteen first lactation Holstein cows averaging 263 days in milk and weighing 614 kg were fed diets adequate or deficient in ruminal nitrogen (N), based on predictions of the Cornell Net Carbohydrate and Protein System (CNCPS). After adjustment to a low crude protein (CP) total mixed rations (TMR; 12.6% CP), the cows were allocated to 13 blocks based on lactation number, milk production, body condition score, and body weight. Within each block, cows were randomly assigned to one of the 3 treatment (TRT) diets (9.4, 11.1 and 14.1% CP for TRT 1, 2, and 3, respectively). All diets contained the same proportion of high moisture corn, chopped grass hay, and minerals, with urea substituted for corn silage as needed to reach the three CP levels. The TRT diets were then fed to the cows for 4 wk. Milk production was significantly affected by TRT: 15.5, 18.8, and 21.7 kg/d for TRT diets 1, 2, and 3, respectively. DMI was increased significantly as the percentage of CP increased from 9.4 to 14.1% CP: 17.6, 20.0, and 21.2 kg/d for TRT diets 1,2, and 3, respectively. CNCPS predictions for production (with and without the N adjustment for ruminal N deficiency) of metabolizable protein (MP) allowable milk were compared with observed milk production. Using the average individual weekly cow data from all 3 TRT, we found that the CNCPS accounted for 72 and 68% of the variation in MP allowable milk without and with the N deficiency adjustment, respectively. The overall mean bias without the N adjustment was 3.3 kg of milk (over prediction model bias of 14.6%, P < 0.001), and the N adjustment reduced the model over-prediction bias to 0.01 kg of milk (P = 0.96).