This edition of Cattle Review considers papers on the consequences of twinning, a potential novel treatment for retained foetal membranes (RFM) and the effect of colostral antibodies on tests for bovine virus diarrhoea virus (BVDV) in young calves.
This study by Andreu-Vázquez et al., (2012) (Theriogenology 78, 2061–2070) was designed to determine the effects of twinning on the subsequent reproductive performance and productive lifespan of high milk-producing dairy cows. The data analyzed were taken from complete reproductive records for 4861 Holstein Friesian cows comprising a commercial herd, including data for 12,587 calving events from April 2001 to March 2012. The twinning rate was 5.6%, and 9.6% of the cows delivered twins at least once during their life. Conception rates before Days 90, 120, and 300 postpartum were 20.8%, 36.9%, and 74.5%, and 34.2%, 51.8%, and 85.0% for cows delivering twins and singletons, respectively. Regression analysis revealed that twinning reduced the chances of conception before Day 90 by a factor of 0.76. Also, the median calving to conception interval was significantly longer for cows calving twins (134 ± 4.5 days) than for cows delivering singletons (108±0.8 days; P<0.001). Moreover, in cows in which conception was successful, the risk of abortion was higher for cows that calved twins than for those calving singletons (13.7% vs. 10.3%, respectively; P=0.01). Culling rates before Days 90, 120, and 300 postpartum were 15.6%, 16.1%, and 28.6%, and 7.6%, 8.7%, and 15.9% for cows calving twins and singletons, respectively. Regression analysis of the factors affecting the culling rate before Day 300 postpartum revealed a 1.41 times greater hazard ratio of culling for cows calving twins than cows calving singletons. Further, mean productive lifespan was almost 300 days shorter for primiparous twinners (N=48; 602+493 days) than for non-twinners (N=2592; 899±581 days; P<0.01), and 200 days shorter for secundiparous twinners (N=126; 914±429 days) than for non-twinners undergoing at least two lactations (N=1936; 1101±522 days; P<0.01). Survival curves for productive lifespan differed between primiparous twinners and non-twinners (P<0.001), and between secundiparous twinners and non-twinners having at least two lactations (P=0.017). Differences in culling patterns for twinners and non-twinners were not restricted to the subsequent lactation but continued as long as 800 days after first calving, strongly suggesting long-term negative effects of twinning. As an economic implication, the authors suggest that twin embryo reduction at the moment of pregnancy diagnosis could be a profitable strategy to cut twinning rates and abolish their detrimental effects on subsequent reproductive performance and productive lifespan.
RETAINED FOETAL MEMBRANES
Although many thousands of cows are treated every week for RFM, much published evidence to date suggests they have subsequently impaired reproduction and that there is little to be gained in treating these cows unless they are developing a secondary metritis. However, a recently published paper by Djuricic et al., (2012) (Animal Reproduction Science 134, 119– 124) is interesting. The aim of their research was to determine the influence of intrauterine application of two different ozone preparations on reproductive performance in Simmental cows with RFM. The study was performed on 143 Simmental cows aged 2–8 years and divided in three groups. Group A (n=46) consisted of cows treated with foam spray ozone applied into the body of the uterus for 5s using a sterile catheter. Group B (n=50) consisted of cows treated using six ozone releasing pearls placed into the uterus. Cows were observed and treated during early puerperium, 24–36 h after parturition. The third group (n=47) consisted of cows without RFM (control group). To assess the reproductive performance of cows, the interval from calving to first insemination (days not pregnant to first service, DOFS), interval from calving to pregnancy (days not pregnant to pregnancy, DOP), relative pregnancy rate (%), first service conception rate (FSCR, %) and all service conception rate (ASCR, %) were measured. The estimate of hazard ratio for the Groups A and B relative to control group with DOFS were 0.423 (P=0.0006) and 0.434 (P=0.0005), and with DOP were 0.701 (P=0.003) and 0.411 (P=0.0003), respectively, implying that cows in the control group were not pregnant longer until first insemination and pregnancy. Variables that had an influence on DOFS were postpartum fever (PPF) (HR=0.458; P=0.003) and milk yield (HR=0.999; P<0.0001) and an influence on DOP were PPF (HR=0.314; P=0.001) and milk yield (HR=0.999; P<0.0001). Cows with RFM treated with either of the treatments under test were reported to have similar or enhanced reproductive performance results compared to the control group of cows. This is a novel study that it would be interesting to see repeated.
With the BVDV control programme in Scotland progressing well and other areas of GB and Ireland implementing, or looking closely at regional or national programmes, the following paper is of great interest since it goes some way towards quantifying something we have known to be a risk for many years. Infection with BVDV causes substantial economic losses. Rapid detection of persistently infected (PI) calves is of the utmost importance for the efficacy of BVDV control programmes. Blood and ear skin biopsy samples are conveniently used for early mass screening of newborns. However, little is known about the impact of colostral antibodies on the outcome of relevant analyses. In this study, Fux and Wolf (2012) (Veterinary Microbiology 161, 13–19) tested a series of samples obtained from five colostrum-fed PI calves from birth until they reached the status of seronegativity for NS3-specific antibodies. They comparatively quantified virus loads in blood samples and dried skin biopsies as detected with BVDV-NS3-, -Ernscapture ELISA and RT-qPCR. Monitoring of NS3-positive leukocytes was done with flow cytometry. Within seven days after colostrum intake, BVDV infected leukocytes disappeared for a three- to eight-week period. Immediately after colostrum ingestion, detectable Erns antigen levels dropped 10 – 100-fold in biopsy samples and in sera detection of Erns failed for one to two weeks. Virus demonstration in biopsy samples with a NS3-antigen-ELISA failed until days 90–158 after birth. Specific antibodies against BVDV also impaired the detection of viral RNA in leukocytes and blood. Mean RNA levels of the five calves were reduced in sera 2,500-fold and in leukocytes 400-fold, the lowest values were at week three of life. In contrast, levels of measurable viral RNA in biopsy samples remained constant during the observation period. The consequences of colostral antibodies resulting in false negative results should be considered when testing young calves for BVDV.