Association of changes among body condition score during the transition period with NEFA and BHBA concentrations, milk production, fertility, and health of Holstein cows
Introduction
The transition period, defined as the period from 3 wk before to 3 wk after calving, represents a challenge for dairy cows as milk production and dry matter intake (DMI) increase dramatically [1], [2]. Metabolic and hormonal changes occurring during the transition period in dairy cows entail numerous changes, with direct effects on health, productivity, and reproductive performance. During the transition period, dairy cows go through a period of negative energy balance (NEB), characterized by increased mobilization of energy reserves, specially fat and protein, to meet the demands of high milk production. High-producing dairy cows, on average, go through a period of NEB during the first weeks of lactation, when the energy demands for milk production exceed the energy intake obtained from the diet. Thus, during early lactation, fat reserves in some cows are mobilized into the bloodstream in the form of non-esterified fatty acids (NEFA) and contribute to overall energy requirements [3]. In the liver, some NEFA are oxidized or reesterified into triglycerides that are either exported as very low density lipoproteins or stored [4]. Measurement of NEFA and beta-hydroxybutyrate (BHBA) can be performed as indices of NEB or ketosis in transition animals [3] and excessive elevation of NEFA or BHBA can indicate metabolic problems [5]. Circulating NEFA concentrations and DMI usually have an inverse relationship [6]. Excess fat mobilization and NEB can attenuate function of the immune system [7], and are associated with negative effects on animal health and production [8], [9]. Maintaining health and productivity during the transition period is one of the greatest challenges dairy herds face.
Evaluation of body condition score (BCS) is a useful management tool to assess body fat stores of Holstein dairy cows [10], [11], [12]. Body condition score has received considerable attention as a tool to aid in the management of nutritional programs in dairy herds [11], [13]. Roche et al. (2009) [13] noted that the BCS of cows at calving, the nadir BCS, and the post-partum BCS loss are associated with differences in milk production, reproduction, and health. Overconditioned cows with a BCS greater than 4.0 at calving had higher circulating concentrations of NEFA in early lactation until 7 wk postpartum compared with cows with moderate or low BCS [14]. Ketonemia, in turn, caused insulin resistance in dairy cows [15], consistent with studies linking high BCS to reduced peripheral insulin sensitivity in the lipomobilization state [16], [17], [18].
Multiple studies have reported a negative relationship of NEFA with reproduction. One experiment found that increased NEFA concentrations during the transition period were associated with decreased pregnancy rate at 70 d after the voluntary waiting period [3], whereas another found that high circulating NEFA was associated with a reduced 21-d pregnancy rate in herd level evaluations of 60 freestall herds [19]. In addition, a third study with 156 lactating dairy cows [20] reported that the probability of pregnancy at first timed AI (TAI) was decreased as serum NEFA concentrations on Day 3 postpartum increased. There are also other studies that have described a negative relationship between postpartum NEFA or loss of BCS and fertility [21], [22], [23].
Thus, our objectives were to evaluate the association between changes in BCS during the transition period, beginning at 21 d before expected calving, near the time of calving, and at 21 d after calving, and compare to the changes in circulating NEFA, circulating BHBA, milk production, pregnancy at first postpartum AI, and diseases. Our hypotheses were: (1) cows gaining BCS during entire evaluated period would have greater milk yield and lower NEFA and BHBA concentrations, with decreased incidence of diseases during lactation; (2) cows with greater circulating NEFA and BHBA in the transition period would have delayed first postpartum ovulation and decreased fertility at first postpartum TAI; and (3) cows losing more BCS during the transition period would have lower fertility.
Section snippets
Animals and management
This study was approved by the Bioethics Committee of School of Veterinary Medicine and Animal Science – University of São Paulo, in accordance with the ethical principles of animal experimentation.
The experiment was conducted on a commercial farm in São Paulo State, Brazil, from June 2011 to March 2012. Multiparous lactating dairy cows (n = 232) were housed in freestall barns bedded with mattresses and equipped with self-locking head gates at the feed line, in a cross ventilation system. Cows
Results
The percentages of cows that gained, maintained, or lost BCS from −21 to 21 DIM were 28%, 22%, and 50%, respectively. At Day −21, the cows in the L group had the greatest BCS (2.97), following by M (2.70), and the G group (2.57) had the lowest BCS (P < 0.01; Table 1). The L group had greater percentage of cows with BCS > 3 on Day −21 (P < 0.01; Fig. 1) than the other groups. However, all cows had similar BCS on Days −7 (2.71) and Day 7 (2.71). At Day 21 postpartum, BCS was greater for cows that
Discussion
Various measures of energy balance, including loss of BCS, have been found to have effects on fertility in lactation dairy cows in many previous investigations. A novel contribution of this study is that it shows the effect of BCS in the prepartum period, and changes in BCS during the transition period on fat mobilization, fertility, milk yield, and health of lactating dairy cows. Some studies have reported that there is an inverse relationship between the shape of the lactation curve and the
Conclusions
Body condition score at the beginning of the close-up period had effects on subsequent BCS loss both prior to and after calving. Furthermore, cows that gained BCS during the transition period, from 21 d prior to calving until 21 d after calving, had lower circulating NEFA and BHBA concentration after calving and subsequently had fewer health problems after calving, earlier return to cyclicity, and greater fertility. These results are consistent with greater loss of BCS during the transition
Conflict of interest
None of the authors of the above manuscript has declared any conflict of interest.
Acknowledgments
The authors thank the owners and staff of Colorado Farm (Araras, SP, Brazil). The authors thank the financial support of São Paulo Research Foundation (FAPESP) for the project and also CNPQ of Brazil for the fellowship to Rafael Villela Barletta and other co-authors.
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