‘Jersey – The Most Profitable and Sustainable Cow?’ – Literature Review for Jersey Australia
Energy balance Energy balance during the transition period and early lactation is the major driver of reproductive success in dairy cows. When a freshly-calved cow has inadequate intake of metabolic fuels and is in negative energy balance (NEB), various hormonal signals from the pancreas, liver and fatty tissues such as insulin, IGF-1, leptin etc. are inhibited, leading to reduced secretion of gonadotropin in the brain, which leads to: no FSH and LH pulses & pre-ovulatory LH surge, reduced ovarian secretion of hormones (oestrogen, progesterone), inhibiting hormonedependent reproductive behaviours, follicular development and ovulation. So NEB in early lactation, as exhibited by body condition loss post-calving, therefore manifests itself in more days to resumption of normal cycling activity, lower first service conception rate, and lower in-calf rates [Butler, 2003; LeRoy et al., 2008]. The duration and the magnitude of negative energy balance in early lactation appear to both be important. As shown by Santos et al. (2010), the relationships between energy secreted in milk (i.e. milk yield) and energy balance, and between energy required for maintenance (body size) and energy balance, are very weak, whereas the relationship between energy intake (i.e. feed intake) and energy balance is fairly strong. Few studies have been done that have compared energy balance in dairy cows of different breeds. Rastani et al. (2001) reported that in a confinement system Jerseys remained in NEB for a shorter period of time post-calving relative to Holsteins (8 weeks vs. 11 weeks) and that the magnitude of Jerseys’ NEB was less than that of Holsteins. Jerseys had a greater EB for the first 7 weeks of lactation relative to Holsteins (Figure 10).
Figure 10. Estimated tissue energy balance of Jersey cows (○) and Holstein cows (●) from week 1 to week 17 of lactation. Tissue energy balances calculated according to NRC (1989). Asterisks indicate that the tissue energy balance differed (P < 0.05) between the two breeds at that time point [Rastani et al., 2001]. This is consistent with Brown et al. (2012), who found that plasma NEFA levels in second lactation cows were lower in Jerseys than in Holsteins. Washburn et al. (2002) conducted a multiple-year study in which groups of Jersey and Holstein cows were run in a pasture-based production system and a confinement system using a total mixed ration (TMR). They found that in each system, Jerseys had higher body condition scores (BCSs) than Holsteins cows throughout lactation, and that cows of both breeds in pasture-based system had lower BCSs than cows in the confinement system. They also found that the difference between the BCSs of Jerseys in the pasture-based system and the confinement system was less than that of Holsteins, indicating that Jerseys ate more than Holsteins relative to their body weight and milk production in the pasture+
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Prepared by Dr Steve Little, Capacity Ag Consulting, 1 November 2021
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