Research Roundup is designed for farmers who want to keep on the cutting edge of new research, with the understanding that ‘new’ information includes ‘ideas that are yet unproven’. The newer the science is, the more uncertain we are about the results – so take what you read with a pinch of salt. With this in mind, we can still report on what researchers are thinking, giving us some idea of where we might be heading into the future.
- Computer algorithms and targeted insemination
- Automated heat detection vs fixed-time AI systems
- Genetic diversity amongst Holstein bulls
- Progesterone supplementation to improve conception rates.
Date: April 1, 2015
Source: Department of Dairy Science, University of Wisconsin (USA)
An increasingly popular strategy on dairy farms is targeted insemination – where farmers use different insemination strategies on subgroups of cows. For example, high-value semen (such as high genetic merit or sex-sorted varieties) could be used exclusively on highly fertile cows and cheap or short gestation semen would be used on cows with poorer fertility. This would reduce costs associated with artificial insemination… but requires good record-keeping on the part of the farmer.
Since it can be very difficult to analyse data manually, the researchers in this study used a special computer algorithm (called lift chart analysis) to automatically sort cows based on their likely level of fertility. This type of analysis is most commonly used to pick out different subgroups of people for targeted marketing – so that men between the ages of 50 – 60 who visit sport websites get ads for golfing equipment, for example, while women between the ages of 30 – 40 that shop online are more likely to be targeted for clothing or makeup.
So would what works on people work on cows? The researchers concluded that this type of analysis was surprisingly appropriate to be used in dairy herds, and that the benefits of using this analysis ranged from USD$0.44 to USD$5.21 per cow in the farms tested – depending on the specific farm system and target strategy.
While the study is interesting, on a more practical level it gives the opportunity to highlight that a similar capability has recently been built into Australian herd software programs such as Dairy Data, Mistro and Easy Dairy. The sexed semen selector feature in these tools can be used to choose the most fertile cows in a herd to be joined to sexed semen.
Date: February 7, 2015
Source: Department of Population Medicine, University of Guelph (Canada)
With larger herd sizes and oestrus becoming increasingly difficult to detect in high-performing dairy cows, farmers have been turning to alternative solutions for improving submission and pregnancy rates. The first option, fixed-time AI, reduces the need for heat detection by using hormones to synchronise the oestrus cycle. The second option, automated heat detection, relies on technology such as pedometers to alert farmers to potential candidates for AI.
So, which solution is superior? To answer this question, researchers surveyed hundreds of farmers about their experience with the systems and analysed the results. They found no significant differences in 21-day pregnancy rate, conception rate, and 21-day submission rate between the two alternatives, coming to the conclusion that both are equally viable options for improving herd performance.
Additionally, they found that farmers who installed a new automatic system improved their previous herd annual pregnancy risk from 15 to 17%, and increased the insemination risk from 42 to 50%. There was no change in conception risk (as expected). This would indicate that automatic systems are potentially good solutions for farms where heat detection is a problem.
Genetic diversity amongst North American Holstein bulls – a cause for concern?
Source: Department of Animal Science, Pennsylvania State University (USA) and College of Pastoral Agriculture Science and Technology, Lanzhou University (China)
Researchers have previously shown that at least three genes on the Y-chromosome are associated with fertility traits in Holstein bulls, indicating that the chromosome may have important influences on bull fertility. It is sex-linked, meaning that it passes from father to son without input from the mother.
Considering its potential importance, the intensive selection of the male line in dairy genetics and the small number of elite sires used, researchers studied the genetic diversity of the Y chromosome in North American Holsteins. To investigate its effective population size, they examined the paternal pedigree information of 62,897 Holstein bulls in Northern America and 220,872 bulls through Interbull. In doing so, they found that two bulls, Pawnee Farm Arlinda Chief and Round Oak Rag Apple Elevation contributed 48.78% and 51.06% to the Holstein bull population in the 2010s respectively. This means that, theoretically, almost every bull in use in the North American Holstein bull population is descended from one of these founders, suggesting that each bull possesses one of only two possible Y-chromosomes. This represents an extreme lack of genetic diversity (note: this does not take into account potential Y-chromosome genetic mutations).
Researchers speculate that this could have negative effects on bull fertility (not cow fertility) and suggest that further study needs to be pursued.
Can progesterone supplementation improve conception rates with Ovsynch-56?
Source: Department of Animal Sciences, University of Florida (USA)
Researchers have previously found that dairy cows without a corpus luteum (CL) at the start of a fixed time AI program were 40% less likely to become pregnant than their herd mates. The purpose of the CL is to produce progesterone, a hormone that supports pregnancy as well as proper growth of the ovulatory follicle.
With this in mind, researchers hypothesized that artificially raising progesterone levels using CIDRs could potentially mimic the CL and correct the decreased pregnancy rate. In this study, they used ultrasound to put cows in three groups at the start of AI – those with a CL, those without a CL that would not be treated, and those without a CL that would receive two CIDRs from days -10 to -3. Having two CIDRs inserted simultaneously may seem unusual, but the researchers found that one device was insufficient to achieve the blood progesterone concentrations they were aiming for in high-producing cows. Blood sampling was used to track these concentrations throughout the experiment.
Happily for them, the researchers found that the untreated group had a 31.3% pregnancy per AI rate, compared to 42.2% for the treated group and 38.4% for the group with CL, indicating that progesterone supplementation ‘re-established’ fertility in cows lacking a CL. I would emphasize that this is only one study and that an economic analysis has not been performed, which is important especially considering the expense involved in using dual CIDR treatments. A study would have to be done under Australian conditions before it could be recommended at a commercial level. However, it is certainly an interesting result.
The researchers also hypothesized that the treatment would reduce pregnancy losses between day 32 and 60 of gestation – however, this did not prove to be the case.
Read the abstract here.