Executive Summary

This review has found that the Australian Jersey has several attributes compared with other breeds used in the Australian dairy industry that may contribute to the profitability and sustainability of Australian dairy farm businesses. These attributes include higher fertility, higher production efficiency, greater heat tolerance and longevity. The main findings are summarised in Table 1.

Table 1. Main findings of this review.

Aspect Main findings

1 Milk yield, composition and market suitability • Holsteins produce more milksolids per cow per year than Jerseys • The composition of milk differs between breeds, but many other factors also influence it • Fat and protein concentrations in milk of Jerseys are higher than those of Holsteins by about 1.1-1.4 g/100ml and 0.5-0.56 g/100ml respectively • The concentrations of fatty acids in milk fat differ between breeds but are small relative to those between different stages of lactation • Jersey milk fat contains a higher proportion of short and medium-chain fatty acids and a lower proportion of C16:1, C18:1, and conjugated linoleic acid • There is insufficient evidence to determine whether Jerseys are more or less susceptible to milk fat depression than Holsteins under the same feeding management and environmental conditions • The amino acid (AA) profile of Jersey milk does not differ significantly from other breeds • Jersey milk has higher concentrations of calcium, phosphorus and zinc than Holstein milk, and a lower concentration of potassium

2 Production efficiency • Jerseys produce 6-11% more energy-corrected milk (ECM) than Holsteins per kilogram of dry matter intake, and 26-31% more ECM per 100 kg bodyweight than Holsteins. Jerseys are 8% more energetically efficient • Jersey cows’ higher production efficiency is due to reduction and dilution of their daily maintenance energy requirement • Jerseys appear to be performing well in mixed breed herds. However,

Jerseys in straight Jersey herds produce more milk solids per year than

Jerseys in mixed-breed herds

3 Feed intake, eating behaviour and nutrient digestibility • Jerseys have about 14-21% higher feed intake capacity than Holsteins per 100 kg bodyweight and 5% per unit metabolic bodyweight. This may be due to their larger gastrointestinal tract per kg body weight, higher rate of particle breakdown within the rumen and higher fractional outflow rate of digesta from the rumen • Jerseys spend more time grazing and ruminating per unit of ingested feed and distribute meals more evenly throughout each 24-hour period than

Holsteins, providing a more regular supply of feed to the rumen • Several studies have found that Jerseys have higher NDF digestibility than

Holsteins, despite their higher gut passage rate • A recent study indicates that Jersey cows are more efficient at utilising dietary nitrogen than Holsteins

4 Fertility • Jerseys have higher fertility than Holsteins. This is likely to be due to genetic selection and energy metabolism, particularly in the transition period and early lactation, in which Jerseys remain in negative energy balance (NEB) for a shorter period of time relative to Holsteins and the magnitude of Jerseys’

NEB is less than that of Helsteins • The mean daughter fertility breeding value for sires of Jersey cows has been flat or declining for four decades, whereas that of sires of Holstein cows is now increasing. If these trajectories continue, the fertility advantage of

Jerseys over Holsteins may be reduced

5 Health • Many Jersey breed associations claim that Jerseys suffer fewer health problems than Holsteins, including stillbirths, calving difficulties, metritis, mastitis, lameness. These claims are supported by several overseas surveys • However, Jersey cows are more predisposed to milk fever than Holsteins. (Milk fever risk is ≥ 2 times higher) • Australian herd data suggest that udder health of Jerseys is slightly better than that of Holsteins. Unfortunately, Australian herd data on specific health problems are not of sufficient quality to enable reliable analysis 6 Heat tolerance • Jerseys are more heat tolerant than Holsteins, due to several factors related to their hair coat, skin structure, subcutaneous fat layer, and body surface area to volume ratio • Under heat stress, the rumen microbiome of Jersey cows is altered, thereby enhancing heat stress resistance, whereas in Holstein cows it is not • However, heat stressed Jersey cows may be potentially more susceptible to infections than Holsteins due to altered immune pathways

7 Longevity • Cow longevity (survival) in a herd has an important influence on the herd’s production efficiency, profitability and environmental footprint • Jerseys tend to live longer, producing for longer, and survive to later lactations more frequently than Holsteins in straight and mixed-breed herds • Increased longevity in a herd means the herd’s mean milk production is higher and fewer non-productive replacement heifers are required

8 Lifetime production efficiency • Many factors related to the milking herd and the replacement herd contribute to lifetime production efficiency of a whole herd • Jerseys have demonstrated advantages in grazing systems, longevity, productive life, calving ease, fertility, heat tolerance and hybrid vigour contribution. However, Holsteins offer different benefits in each production system. • A modelling approach may be more appropriate and useful when comparing lifetime efficiency of Jerseys and Holsteins within a given production system

9 Environmental footprint • Several studies have suggested that the emission intensity of milk production is about 8-12% lower with a Jersey herd compared to a Holstein herd when the life cycle analysis (LCA) approach was used to calculate GHG emissions • However, there may be little difference between the breeds in emission intensity of milk production, as Jerseys emit more methane per kg DM intake compared to Holsteins

10 Suitability for different production / housing systems

• Jerseys are used successfully around the world in a diverse range of production systems (grazing and confinement) • Jerseys may perform at their best in grazing systems where their larger digestive tract per unit BW allows them a greater feed intake capacity. • Jerseys are better suited to walking longer distances associated with grazing systems than Holsteins, and to hot climatic conditions. • Jerseys’ higher fertility and easier heat detection is also an advantage, particularly in grazing systems • The behaviours and performance of Jerseys in different housed production systems requires further research 11 Genetic trends  The mean daughter fertility ABV for sires of Jersey cows has been flat or slowly declining for four decades, whereas that of sires of Holstein cows is now increasing  Cows’ sire ABVs are highly variable for Jerseys and Holsteins, especially for cow's sire daughter fertility, Balanced Performance Index and Protein ABV