Effect of Type of Cow-Calf Contact on Health, Blood Parameters, and Performance of Dairy Cows and Calves.

Prolonged cow-calf contact (CCC) could potentially improve dairy calf welfare. However, it is currently unknown how different types of CCC affect animals' biological functions. We evaluated health and performance parameters of dairy calves and their dams, where calves: (i) had no contact with their dam (NC), in which the calf was removed from the dam directly after birth (n = 10); (ii) were allowed to have partial contact (PC) with their dam, in which the calf was housed in a calf pen adjacent to the cow area allowing physical contact on the initiative of the dam but no suckling (n = 18); (iii) were allowed to have full contact (FC) with their dam, including suckling, in which calves were housed together with their dams in a free-stall barn (n = 20). Throughout the first 7 weeks postpartum, data were collected on the health status, fecal microbiota, hematological profile, immune and hormonal parameters, and growth rates of calves, and on the health status, metabolic responses, and performance of dams. Overall, FC calves had more health issues (P = 0.02) and a tendency for higher antibiotic usage (P = 0.07) than NC calves. Additionally, FC calves showed elevated levels of erythrocytes, hematocrit, hemoglobin, and leukocytes on day 49 compared to NC calves (P < 0.001). Calf fecal microbiota changed over time, and we found preliminary evidence that fecal microbiota is affected by the type of CCC, as reflected by differences in relative abundances of taxa including Lactobacillus in FC calves compared to NC and PC calves except on days 7 and 66. The FC calves had a greater average daily gain in body weight than NC and PC calves (P = 0.002). Cow health was not affected by the type of CCC, although in the first 7 weeks of lactation FC cows had a lower machine-gained milk yield accompanied by a lower fat percentage than NC and PC cows (P < 0.001). These results indicate that full contact posed a challenge for calf health, presumably because the housing conditions of FC calves in this experimental context were suboptimal. Secondly, ad libitum suckling leads to higher weight gains and negatively affected milk fat content besides machine-gained yields. More research into strategies to improve cow-calf housing and management in CCC systems is warranted.

Methodological terminology and definitions for research and discussion of cow-calf contact systems.

Due to increasing public concern regarding separation of the dairy cow and calf within the first days after birth, alternative systems, where cows and calves stay in contact for an extended period, are receiving increasing interest from a broad array of researchers and other stakeholders. With more research in the area, there is a risk of inconsistencies emerging in the use of terminology. To create a better consensus in further discussions, the aim of this Research Reflection is to provide definitions and propose a common terminology for cow-calf contact in dairy production. We also suggest definitions for various systems allowing cow-calf contact and describe the distinct phases of cow-calf contact systems.

Effect of cow-calf contact on cow motivation to reunite with their calf.

Early cow-calf separation prevents much of cows' natural maternal behaviour. Early separation is thought to prevent the development of a cow-calf bond. To assess this bond, we measured motivation of dairy cows to reunite with their calf. To vary the degree of bonding, some cows were allowed continued contact with their calf and others were separated from their calf soon after birth, following standard practice on most farms. Among cows allowed continued contact, some were able to suckle their calf and others were prevented from suckling (by covering the cow's udder with an udder net). Cows were habituated to the weighted-gate apparatus before calving by daily training with the (un-weighted) gate. After calving, cow willingness to use the gate was assessed by determining if she would push open the gate to access to her own calf. Testing occurred once daily, with weight on the gate gradually increased. After passing through the gate, the dam's calf-directed behaviour was recorded. Suckled cows pushed a greater maximum weight (45.8 ± 7.8 kg) than separated cows (21.6 ± 6.7 kg) and non-suckled cows (24.3 ± 4.5 kg), with no differences between separated and non-suckled cows. Once reunited, latency to make nose contact and duration of licking did not differ between treatments. We conclude that motivation for calf contact is greater for cows that are suckled.

Reducing variation in a rabbit vaccine safety study with particular emphasis on housing conditions and handling.

This paper describes the results of a study of the effects of modified housing conditions, conditioning and habituation on humans using a rabbit model for monitoring whole-cell pertussis vaccine (pWCV)-induced adverse effects. The study has been performed with reference to previous vaccine safety studies of pWCV in rabbits in which results were difficult to interpret due to the large variation in experimental outcome, especially in the key parameter deep-body temperature (T(b)). Certain stressful laboratory conditions, as well as procedures involving humans, e.g. blood sampling, inoculation and cage-cleaning, were hypothesized to cause this large variation. The results of this study show that under modified housing conditions rabbits have normal circadian body temperatures. This allowed discrimination of pWCV-induced adverse effects in which handled rabbits tended to show a dose-related increase in temperature after inoculation with little variance, whereas non-handled rabbits did not. Effects of experimental and routine procedures on body temperature were significantly reduced under modified conditions and were within the normal T(b) range. Handled animals reacted less strongly and with less variance to experimental procedures, such as blood sampling, injection and cage-cleaning, than non-handled rabbits. Overall, handling had a positive effect on the behaviour of the animals. Data show that the housing modifications have provided a more robust model for monitoring pWCV adverse effects. Furthermore, conditioning and habituation of rabbits to humans reduce the variation in experimental outcome, which might allow for a reduction in the number of animals used. In addition, this also reduces distress and thus contributes to refining this animal model.

Exposure to tetrabromobisphenol A (TBBPA) in Wistar rats: neurobehavioral effects in offspring from a one-generation reproduction study.

Within the framework of an EU project on risk assessment of brominated flame retardants, TBBPA was studied for neurobehavioral effects in rats. To permit benchmark dose analysis, eight dose levels were chosen ranging from 0 to 3000mg/kg body weight. Exposure of parental rats started 10 and 2 weeks before mating in males and females, respectively, and was continued throughout mating, gestation and lactation. After weaning, exposure was continued in the offspring throughout life. Previous studies had indicated TBBPA-induced effects on thyroid hormones. Because of the known implication of thyroid hormones in neurodevelopment, the present experiments tested if TBBPA exposure affects thyroid-dependent neurobehavioral functions in offspring, such as auditory responses and conditioned fear. Sweet preference was included because of sex-specific effects in littermates. No statistically significant effects were found on context or cue conditioned fear or sweet preference. Auditory responses were examined with brainstem auditory evoked potentials (BAEPs) at approximately 50-110 days of age. BAEP thresholds and wave IV latency were increased in exposed female rats in the low frequency range. In male rats, thresholds were unaffected, but absolute latency of wave IV and interpeak latencies II-IV showed exposure-related increases at low frequencies. The outcome pattern suggests a predominant cochlear effect of TBBPA in females while in males neural effects are more apparent. According to benchmark analysis, the critical effect doses (CED) for prolongations of wave IV latency at 0.5kHz were in the range of 35-70mg/kg body weight with lower bounds (BMDL) of approximately 8mg/kg in males and females. The BMDL values for elevation of hearing thresholds in females were in the range of 1-40mg/kg body weight, depending on frequency. The benchmark doses for effects on the BAEP were similar to values for decreases in circulating thyroid hormones. The comparison of the exposure level at which the most sensitive effect was found with current human exposure levels yielded a margin of exposure of about 5, according to a recent risk assessment. Further investigations are needed to examine exposure pathways, fate in the body and effects of TBBPA.

Endocrine effects of tetrabromobisphenol-A (TBBPA) in Wistar rats as tested in a one-generation reproduction study and a subacute toxicity study.

Endocrine effects of the brominated flame retardant tetrabromobisphenol-A (TBBPA) were studied in a one-generation reproduction assay in Wistar rats via repeated dietary exposure, applying eight dose groups at 0-3-10-30-100-300-1,000-3,000 mg/kg body weight/day (mkd). This design enables dose-response analysis and calculation of benchmark doses (BMDL). This reproduction study was preceded by a 28-day repeat dose subacute toxicity study, at 0-30-100-300 mkd. Major effects in the reproduction study included decreased circulating thyroxine (T4) with BMDLs of 31 (m) and 16 (f) mkd, and increased weight of testis and male pituitary (BMDLs of 0.5 and 0.6 mkd). The hypothyroxinemia correlated to a cluster of developmental parameters including delayed sexual development in females, decreased pup mortality, and effects on brainstem auditory evoked potentials [Lilienthal, H., Verwer, C.M., Van der Ven, L.T.M., Piersma, A.H., Vos, J.G., 2008. Neurobehavioral effects of tetrabromobisphenol A (TBBPA) in rats after pre- and postnatal exposure. Toxicology]. A second cluster of parameters in F1 animals was correlated to increased testis weight, and included female gonad weight, endometrium height, CYP19/aromatase activity in the ovary, and plasma testosterone levels in males. These two correlation clusters suggest a dual action of TBBPA. The only effects in the subacute study were decreased circulating T4 and increased T3 levels in males (BMDLs 48 and 124mkd), and non-significant trends for these parameters in females, suggesting that the other effects in the reproduction study were induced during development. Combined with data of human exposure to environmental TBBPA, the margin of exposure for highly exposed populations can be calculated at 2.6, and current use of TBBPA may therefore be a matter of concern for human health.

Effects of housing condition on experimental outcome in a reproduction toxicity study.

In most toxicity studies single housing is still preferred, as social stress is believed to have an effect on experimental outcome through interaction with the toxic compound or by increasing variation. There are also arguments that single housing will have a similar effect. In this study the qualitative and quantitative effects of single- and social housing of rats has been investigated on immune- and endocrine responses, histopathology and body- and organ weights in a one-generation endocrine disrupter study (OECD 415) in rats exposed to tetrabromobisphenol A (TBBPA). The results of this study show that differences in parameters between the housing conditions were rarely noted. Striking results of the study are that in several parameters significant differences were noted in the un-dosed control group in single versus group housed animals, meaning that TBBPA can mask or enhance housing effects, or vice versa. In one case single housing altered the effect of the toxic compound. Depending on the endpoints of the study, the type of housing condition must be taken into consideration as findings like these could have great implications for the interpretation and validity of results from toxicological assays and the number of animals needed to detect significant effects of toxic compounds.