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For many years it has been accepted that appropriate nutrition management about four weeks before calving involved the feeding of sufficient concentrates to ensure that cows do not lose condition pre-calving. This was supported by blood analyses that indicated a positive association between elevated fatty acid concentrations or greater body condition score (BCS) loss immediately before calving and the incidence of post-calving metabolic and infectious diseases. More recently though, studies designed to result in small, controlled release of fatty acids pre-calving did not show metabolic profiles consistent with those reported in the blood analyses studies. In fact, post-calving energy balance and indicators of metabolic health and immune function were, in general, improved when energy intake was less than requirements and blood fatty acid concentrations were elevated before calving. However, lower milk production resulted in cows that were severely restricted to about 50% of energy requirements during the month pre-calving. This indicates that a threshold level of energy restriction shortly before calving exists, below which production and, possibly, cow health may be adversely affected post-calving. It was therefore hypothesized by author J.R. Roche and co-workers that, considering that energy intakes between 75 and 100% of requirements have been advantageous to indicators of health, such a threshold must be between 50 and 75% of requirements. They have studied these concepts in pasture-based systems, where cows in such systems are generally thinner at the end of lactation than cows fed total mixed rations and, as a result, over-feeding of energy during the late dry period is standard practice to achieve optimum calving BCS. An alternative approach to the standard practice would be to manage the cows to gain BCS through late lactation, such that cows ended lactation close to optimum calving BCS and maintenance of BCS through to calving. The study was published in the Journal of Dairy Science, Volume 100 of 2017, page 1720 to 1738, the title being: Strategies to gain body condition score in pasture-based dairy cows during late lactation and the far-off non-lactating period and their interaction with close-up dry matter intake.
The authors sought to quantify the effect of moderate or excessive energy intakes during the late dry period in cows that had been managed to gain or maintain BCS through late lactation and whether this strategy interacted with close-up level of feeding. The effects on milk production and circulating indicators of energy balance and metabolic health in the subsequent early lactation were evaluated.
A herd of 150 cows was randomly assigned to one of two feeding levels in late lactation to achieve a low and high BCS at the time of dry-off (approximately 4.25 and 5.0 on a 10-point scale). Following dry-off, both herds were managed to achieve a BCS of 5.0 one month before calving; this involved controlled feeding (i.e., maintenance) and over-feeding of energy during the late dry period. Within each late dry period feeding-level treatment, cows were given 65, 90 or 120% of their pre-calving energy requirements for three weeks pre-calving in a 2 × 3 factorial arrangement (25 cows per treatment). Body weight and BCS were measured weekly before and after calving and milk production was measured weekly until week seven post-calving. Blood samples were collected weekly for four weeks pre-calving and five week post-calving, and on day 0, 1, 2, 3 and 4 relative to calving, and analyzed for indicators of energy balance (e.g., blood fatty acids, β-hydroxybutyrate), calcium status and inflammatory state.
No interaction was observed between the late dry period and close-up feeding levels. Over-feeding of energy to low BCS cows during the late dry period reduced blood fatty acid and β- hydroxybutyrate concentrations in early lactation, and increased the blood albumin to globulin ratio compared with cows that were dried off close to recommended calving BCS and control-fed during the late dry period. Cows consuming 65% of their energy requirements during the close-up period had lower fatty acids and β-hydroxybutyrate in early lactation, but produced less milk, particularly during the first 21 days of lactation and had a lower blood cholesterol concentration and albumin to globulin ratio, when compared with the cows offered 90 or 120% of their energy requirements. Collectively, these measurements indicate that a severe restriction (less than 70% of energy requirements) during the late dry period increases the risk of disease in early lactation and reduces milk production.
In summary, late dry period overfeeding of energy to cows that needed to gain BCS did not influence immediate post-calving metabolic health in grazing dairy cows, but restricting cows below 70% of energy requirements during the late dry period resulted in a blood profile indicative of greater inflammation.