This study was conducted to determine the effect of feeding high milk volumes on the growth rate, health and cross-sucking behaviour in group-fed Jersey calves. Three-day-old heifers (n = 120) in a seasonal calving dairy herd were randomly assigned to one of 6 treatment groups. Three groups received high milk volumes (HMV), consisting of ad libitum milk or milk replacer feeding twice a day, while 3 groups received restricted milk volumes (RMV), consisting of 2 twice daily, during the pre-weaning period. After a pre-weaning period during which feeding was reduced to once daily, all calves were weaned at 42 days and monitored until 60 days of age.Adjusting for birth mass, birth date,damparity and sire, average daily mass gain (ADG), both pre-weaning (days 0–42) and overall (days 0–60), was higher inHMVthan inRMVcalves (P<0.001).After weaning, growth rates showed no differences and at 60 days of age the HMV calves maintained a 6.74 kg advantage in mean body mass (P < 0.001). The mean intake of dry starter feed was higher in RMV than in HMVcalves. Overall feed conversion rate ofHMVcalves was 9.6%better thanRMVcalves. However, the variable cost per kg mass gain was 12 % higher for HMV calves. In the RMV groups 75 % of calves showed cross-sucking behaviour pre-weaning and 18 % post-weaning, whereas in HMV calves the proportions were 2 % and 7 %, respectively. There was no significant effect of milk volume on the incidence of diarrhoea.We conclude that the feeding of high volumes of milk to Jersey calves has a positive effect on growth rate, without compromising health or reducing solid feed intake after weaning. However, the higher cost of such a feeding system may limit its implementation

<p>The objectives of this study were to compare the efficacy of 6 different dry-cow intramammary antimicrobial products for the treatment and prevention of mastitis during the dry period in a well-managed high producing Friesland dairy herd, and the influence of treatment on the somatic cell count (SCC) of cows during early lactation. One of 6 dry-cow intramammary antimicrobial products was randomly allocated to 162 cows due for drying off over a period of 14 months. All cows were sampled twice prior to drying off, and twice after calving for the determination of SCC and presence of microorganisms. The quarter prevalence of pathogens at drying off and post-calving, the overall quarter cure rate and the rate of new intramammary infections occurring during the dry period were determined. The overall quarter prevalence of intramammary infections (IMIs) at drying off was 29.78 % and after calving 22.22 %.</p><p>There was a statistically significant difference (P &lt; 0.05) between the prevalence of major and minor pathogens at drying off (7.87 % and 21.91 %) and at calving (4.47 % and 17.75 %). The most prevalent pathogens isolated at drying off (21.14 %) and at calving (16.98 %) were coagulase-negative staphylococci (CNS). The quarter cure rate during the dry period was 83.94 %. The cure rate for the major pathogens (98%) was significantly better (P &lt; 0.05) than that for minor pathogens (78.9 %).</p><p>The overall quarter cure rate varied from 72.3 % to 93.9 % for the various products. The rate of new quarter infections during the dry period was 17.44 % with a significant difference (P&lt;0.05), between the prevalence of new quarter infections with major (4.32 %) and minor pathogens (13.12 %). CNS was the most prevalent pathogen causing new quarter infections (12.34 %) and the rate o f new quarter infections varied from 13.4 % to 24.1 % for the various products.</p><p>It is concluded that there is a difference in efficacy between antimicrobial intramammary dry-cow products in their ability to cure and prevent new IMIs during the dry period. Dry-cow products are mainly formulated for efficacy against Gram-positive cocci, while providing no or little protection against Gram-negative bacteria. Therapeutic levels may persist for only 14 to 28 days into the dry period and fail to protect the udder during the last trimester. Dry-cow therapy should, however, always form part of a holistic approach to the dry period which also considers cow factors, dry-cow management, microorganisms and the environment of the dry cow.</p>

The prevalence of bovine viral diarrhoea (BVD) serologically positive animals in 18 dairy herds with clinical and pathological lesions suggestive of BVD infection, the post-vaccinal seroconversion rates in negative animals vaccinated twice with an inactivated BVD vaccine, and the control measures taken, are described. The pathological and histopathological findings in 6 necropsies performed on animals that died in 5 separate herds closely resembled published descriptions. Positive immunohistochemistry results in 3 cases confirmed the diagnosis in those animals. In 1 herd the prevalence of prevaccinal BVDantibodies was only 36.8 %, while the prevalence varied from 79.85 to 100 % in the remainder. Control measures taken included immunoprophylaxis with an inactivated vaccine, culling animals that were serologically negative after vaccination that were regarded as probably persistently infected (PI) and the implementation of additional biosecurity measures. The prevalence of serologically negative PI animals in 10 herds varied from 0.38 to 4.04 %, with 8 herds less than 1 %and 2 herds at 2.79 %and 4.04 %, respectively. Methods based on vaccinating the herd, followed by serological testing and culling cattle that did not develop an antibody titre, are not reliable. The identification of PI animals should be confirmed by isolation of the virus or identification of the antigen.

This study investigated the association between pre-breeding blood urea nitrogen (BUN) concentration and reproductive performance of beef heifers within different management systems in South Africa. Bonsmara heifers (n = 369) from five herds with different estimated levels of nitrogen intake during the month prior to the commencement of the breeding season were sampled in November and December 2010 to determine BUN concentrations. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at study enrolment. Trans-rectal ultrasound and/or-palpation was performed four to eight weeks after a three-month breeding season to estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until the estimated conception date. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the association of pre-breeding BUN concentration with subsequent pregnancy and DTP respectively. After stratifying for herd and adjusting for age, 2 heifers with relatively higher pre-breeding BUN concentration took longer to become pregnant when compared to those with relatively lower BUN concentration (P = 0.011). In the herd with the highest estimated nitrogen intake (n = 143), heifers with relatively higher BUN were less likely to become pregnant (P = 0.013) and if they did, it was only later during the breeding season (P = 0.017), after adjusting for body mass. These associations were not present in the herd (n = 106) with the lowest estimated nitrogen intake (P > 0.500). It is concluded that Bonsmara heifers with relatively higher pre-breeding BUN concentration, might be at a disadvantage because of this negative impact on reproductive performance, particularly when the production system includes high levels of nitrogen intake.