A recent medical phenomenon extending the natural pregnancy cycle within Primiparous and multiparous dairy cows Souza et al., 2008, who’ve been administrated timed artificial insemination. The double- ovsynch protocol; permit artificial insemination to be implemented at the actuate optimum time without manipulation of ovaries and uterus Giordano et al., 2013. Modifying the reproductive stamina of dairy cows McDougall et al., 2007 from 60 to 88 days. Furthermore, this investigation would also prove to demonstrate, if extending the natural pregnancy cycle from 60 to 88 could minimise or increase milk production. Potentially causing farmers to miss out on profitability Arbel et al., 2001.
Typically, surveillance was the common method for monitoring the oestrus cycle. This task often was a time-consuming procedure. Implications for instance; milk yield, imbalanced feed rations, stress for instance heat stress, and welfare supervisions are critical expertise that influence heat expression Huzzey et al., 2015. On the other hand, farmers/ veterinarians applied equipment in the form of tail painting; gives a visual indication of when a cow has stood to be mounted and consequently rubbed, showing that she is in heat López-Gatius et al., 2006.
Approximately, estrous activity is between 6 to 24 hours, whereas the period a cow stands to be mounted lasts consequently 8 hours Ferguson and Galligan, 1999. A total of 186 dairy cows were used for this research project. Bello et al., 2013.
The cows were separated into two groups both receiving the insemination procedure. one group would undergo a VMP “voluntary waiting period of 60 days; number of participants = 87 whereas the other group had VMP of 88 days number of participants = 99, formed of both Primiparous and multiparous dairy cows. Produced by the two groups was a daily intake of milk production. Results recorded VWP60; 1,352 litters of milk being produced compared to VWP88; 1,359 litres of milk were produced. From these results it is clearly highlighted due to delay on natural oestrus cycle there was an increase in milk production from the lactating cows, although not a massive increase; 0.07%. Nevertheless, still enough of a profit for farmers wanting to subdue their dairy cows towards the double- ovsynch protocol Österman and Bertilsson, 2003.
Pregnancy within cattle especially during the lactation process affects the profitability of dairy herds by defining calving interval, milk production and efficiency (De Vries, 2006; Inchaisri et al., 2011; Giordano et al., 2012).Two major determinants are insemination and conception risk due to the end of “VMP” the duration of VMP can also influence the exact approximation of pregnancy because distinguishes when cows meet the requirements for insemination.
By delaying the duration of the VMP it benefits the reproductive performance of cows through numerous mechanisms. A good illustration is it may provide more time to recover from uterine health (Gilbert et al., 2005; Gautam et al., 2009; Sheldon et al., 2009) Other positives that can be demonstrated from this are, improved immune status, contemplating more time to resolve the inflammatory process, established immediately after calving or in both situations (LeBlanc et al., 2011; LeBlanc, 2014).
Furthermore, an increased VMP could vouchsafe cows increased time to reinstall reproductive hormone secretion patterns, equally increasing metabolic status promoting resumption of ovarian cyclicity (Butler, 2003; Kawashima et al., 2012; Cheong et al., 2016) Earlier ovulation postpartum and supplementary estrous cycles before first service had been found to be connected to linked reduced days to first service and greater pregnancies Thatcher and Wilcox, 1973; Butler and Smith, 1989; Darwash et al., 1997).
This Prevents the negative energy balance; when the energy intake exceeds the energy expenditure, there is a positive energy balance which results in weight gain vice versa negative energy balance results in weight loss Butler and Smith, 1989. because of energy balance it causes early lactation, fundamentally improving the reproductive performance of bovines prolonging additional time for cows to recuperate body tissue reserves. (Souza et al., 2007, 2008; Carvalho et al., 2014).
Advantages Disadvantage
Application suitable in all cows’ breeds Possibility of AI in cows with reproductive problems disorders.
Reduction for heat detection and gynaecological examination. Highest efficiency limited to start of protocol between 5th and 9th days of cycle.
Shortening intercalving and voluntary waiting periods. Increased embryonic mortality rate.
Synchronisation of work in herd Price of hormones.
Possible therapeutic cure effects Different responses to hormonal treatment.
Fertility comparable to other methods Poor fertility in heifers.
In conclusion, lengthening the time frame of VMP from 60 to 88 in dairy cows, was particularly beneficial to primiparous cows. With the extended VMP their physiological status demonstrated to be more conductive to pregnancy. Furthermore, primiparous cows had improved uterine health, increased BCS, and reduced systemic inflammation. Equally, decreasing anovulation before insemination. Although prolonging VMP caused delayed pregnancy particularly lactation, this omnipresent extension towards lactation time frame signified a greater production of total milk yield.
References
https://www.sciencedirect.com/science/article/pii/S0022030217309323#fig5
https://www.ncbi.nlm.nih.gov/pubmed/22394964
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5894419/
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