The Research Column

In recent years, the Montbéliarde (MO), Viking Red (VR), and Holstein (HO) breeds have been marketed for three-breed rotational crossbreeding. The MO and VR breeds have placed more selection emphasis on fertility, health, and longevity for decades than has the HO breed, while maintaining substantial selection emphasis on increased milk solids. Research on lactation-curve characteristics of crossbred dairy cows is however limited. Also, the persistency of production for MO-sired and VR-sired crossbred cows compared with their HO herdmates has not been studied.

The importance of obtaining greenhouse gas (GHG) and corresponding resource use data on dairy farms cannot be emphasised enough, as baseline data is required to evaluate where to put emphasis in mitigation or change. The publication from South-Western Sweden cited provides such an opportunity. The authors collected data and use Life Cycle Assessment (LCA) methodology in analysis. The purpose of the study was to gain knowledge of the environmental impact of contemporary milk production and how farms differ in resource use and emissions.

Of the newer developments are the availability of high-dimensional omics, such as the metagenome, metabolome and transcriptome, which provide the opportunity to incorporate such data, in addition to genomic data, to improve the prediction of feed efficiency. The inclusion of microbial data in genomic models enables unravelling the contribution of a particular host genome and its microbiome to the phenotype of interest.

For a food to be considered a good source of calcium (Ca), it must have a high Ca concentration and the Ca must be highly bioavailable. Dairy products have traditionally been considered excellent sources of Ca due to both a high Ca density and bioavailability. For example, a glass of 240 mL milk is estimated to contain 300 mg Ca, providing about 96 mg absorbable Ca and a bioavailability of 30 %, which is considered to be high.

Enteric methane production needs to be reduced in livestock, also in dairy cows. Methanogenesis by methanogens in the rumen is responsible as their fermentation results in hydrogen accumulation which is usually picked up into the CH₄ molecule as one of the end products. The compound 3-nitrooxypropanol (3-NOP), marketed as Bovaer, has been shown to inhibit the enzyme methyl-coenzyme M reductase, which is responsible for the last step in methanogenesis, and which in studies have shown a substantial reduction in methane yield.

Grassland soils are arguably the most important store of terrestrial carbon, accounting for approximately 22% of terrestrial C stocks. Over the years, management of these grasslands, including the conversion of native vegetation to planted pastures, has resulted in considerable C loss. This highlights that the lost C should be recaptured and future losses avoided, which depends on how these planted pastures are managed. The recapture of lost C has been proposed as a mechanism to mitigate GHG emissions since it should increase soil carbon stocks.

Since mastitis resistance and milk SCC have a close relationship with udder and teat conformation features, selecting cows with ideal udder and teat shape may be a proposition. Also, the use of technologies such as sonography to detect udder health should be pursued. Ultrasound is commonly used in human medicine to check the mammary glands, for example to differentiate between cystic and solid lesions using 5-13 MHz scanners. Ultrasound is a non-invasive and non-destructive diagnostic tool which could provide real time images of the healthy and mastitic organ.

Heat stress occurs when animals are unable to effectively dissipate heat from metabolism associated with digestion, maintenance and production, plus any heat gained from the environment, the latter being more prominent if the temperature-humidity index (THI) exceeds the comfort zone. In high producing (Holstein) dairy cows, the condition is exaggerated because of the high metabolic load associated with the elevated metabolic demands of lactation.

New-born calves are susceptible to disease due to an under-developed immune system, which at this stage is only supported by an inadequate intestinal microbiota. If healthy, the microbiota nevertheless protects against harmful gut micro-organisms, activates the immune system and assists in initial calf nutrition. Colostrum at this stage is crucial to allow large-molecule immunoglobulins to pass through the short-lived comparatively large pores in the intestinal wall.

Soybean meal is globally probably the most favoured protein supplement in dairy cow diets, but increased demand has elevated its price, which necessitates evaluating other options. One such option is canola meal, with limited research suggesting that canola meal is used as efficient or more efficiently for milk production than soybean meal. Some research showed that the inclusion of canola meal increased DMI, milk yield and milk protein compared to soybean meal and other protein sources.