During the postpartum period, dairy cows enter a period of tissue catabolism called negative energy balance (NEB). Simply put, the amount of energy consumed is less than what’s required; this imbalance causes a cascade of metabolic failures that can be minimized by using a holistic approach.
Researchers focus on feed intake postpartum by managing the diet prepartum. A recent study hypothesized that feeding high forage levels (87 percent vs. 77 percent forage) at three weeks before calving would reduce the incidence of metabolic disorders postpartum.
Why? Because forage NDF provides rumen fill. Cows fed 77 percent forage consumed more feed, and consequently more net energy, than those fed 87 percent forage.
Postpartum, dry matter intake (DMI) was similar for both groups. Worth noting is that the decline in DMI on the day before calving was greater for the cows fed the 77 percent forage diet.
Many believe that the kinetics of this intake change is instrumental when predicting metabolic health after calving. Cows fed the diet with 87 percent forage diet showed less subclinical ketosis (seven vs. 22 cows) and tended to get pregnant sooner than those fed 77 percent forage.
Cows fed the 77 percent forage diet produced more milk until 59 days in milk, but because of the higher incidence of subclinical ketosis, milk production over the 150 days tended to be lower compared to cows fed 87 percent forage.
In other words, cows fed the diet with 87 percent forage developed fewer metabolic disorders and consequently better reproduction and production.
Many producers already feed a diet high in forage (i.e., straw) to prepartum cows. What’s important to know is that the benefit is a nutrient – not ingredient – effect. Forage NDF establishes rumen fill, which in turn stabilizes the kinetics of intake pre-calving and post-calving. The result is fewer metabolic failures due to improved NEB.
Negative energy balance is correlated with immunosuppression, and the mechanisms involved are described in detail in the literature.
Briefly, low levels of circulating glucose and calcium, combined with high levels of non-esterified fatty acids (NEFA) and β- hydroxybutyric acid (BHBA), lead to decreased neutrophil activity (phagocytosis and killing capacity) and the possibility of increased metabolic and uterine disease.
Researchers studied the effect of feeding calcium salts of linoleic acid (palm or safflower oil) 21 days prepartum to 30 days postpartum (transition period) on uterine health, reproduction and production. The authors of the study also tested the effect of supplemental palm oil (EPA) or fish oil (DHA) after 30 days postpartum (breeding period).
The n-6/n-3 ratios for palm, safflower and fish oils were 31, 48.9 and 0.7 g per 100 g of fatty acid, respectively. Concentration of plasma NEFA, glucose and BHBA were not different among treatments. The proportion of cows pregnant 60 days after insemination was higher for cows supplemented with fish oil compared to those supplemented with palm oil.
Cows fed safflower oil produced, on average, more milk the first five months of lactation (41.9 vs. 41.2 kg per day) than cows fed palm oil. Based on these results, the authors recommend a diet rich in omega-6 fatty acids during the transition period and one supplemented with EPA and DHA during the breeding period.
Supplementing “crude” fat during the transition period is not new, and much of the older literature shows variable results with regard to NEB and production. But today’s research is focusing on the effect of specific fatty acids.
The last-mentioned study demonstrates the importance of quantifying the fatty acid source and load in diets for transition cows. Specific quantities and/or ratios of omega-6 and omega-3 fatty acids are required to elicit the positive effect on production and reproduction. PD
Gustavo Cruz and Chris Canale are with Cargill Animal Nutrition.
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