view - Department of Reproduction, Obstetrics and Herd Health

Milk production per lactation (kg)
Calving Interval (days)
CHAPTER 1
10,000
9,000
8,000
430
420
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
410
400
390
380
370
Year
Figure 1. The average milk production per lactation (kg; grey bars) and calving interval (days; black line)
in Flemish herds from 1991 to 2011 (CRV, 2011).
During the transition period, substrate availability for gluconeogenesis is limited
due to both a decreased DMI and the ongoing adaptation of the rumen (Grummer, 1993;
Grum et al., 1996; Goff and Horst, 1997). A simultaneous increasing demand for milk
lactose synthesis causes the cow to be unable to meet her maintenance, production and
reproduction requirements especially in terms of glucose. The latter profoundly stresses
the cows’ endocrine, metabolic and physiological status, and the cow has to pass a
period commonly referred to as the NEBAL (Drackley et al., 2005).
The NEBAL pushes the cows’ metabolism to switch to a depletion of body
reserves, releasing large amounts of non-esterified FA (NEFA) mainly from the
subcutaneously and abdominally stored fat depots (up to 3.2 kg/d; Drackley et al.,
2001). This body fat mobilization results in a steep increase in blood NEFA
concentrations around parturition. Elevated NEFA concentrations impair metabolic and
immune cell function in humans (Mora and Pessin, 2002), and are associated with
impaired metabolic health in transition cows (Herdt, 2000; Jorritsma et al., 2003; Bobe
et al., 2004). Leroy et al. (2004) showed a significant correlation between the
concentrations of biochemical indicators of NEBAL (β-hydroxy butyric acid (BHBA),
glucose, NEFA) in the serum and follicular fluid (FF) of high yielding dairy cows early
post partum. Afterwards, the same research group mimicked the follicular environment
in an in vitro maturation model and observed a marked deleterious effect on granulosa
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