Evaluation of blood metabolites in dairy cows grazing under two pasture allowances and supplemented with corn silage under restricted grazing conditions

Abstract

-This study was conducted to evaluate the influence of management tools -daily pasture allowance and corn silage supplementation -during periods of forage shortage on the metabolism of dairy cows grazing low-mass pasture in temperate regions. Forty lactating Holstein cows were used during an experimental period of seventy days (April 15 to June 23, 2012). Blood metabolites and milk production were determined in fall-calving dairy cows grazing under two daily pasture allowances (PA) (moderate, 17 kg vs. high, 25 kg dry matter (DM)) and supplemented with corn silage (CS) (low, 4.5 kg vs. high, 9.0 kg DM). All cows received 3 kg DM of concentrate. Plasma concentrations of β-hydroxybutyrate (BHBA), nonesterified fatty acids (NEFA), and urea were determined using an automated spectrophotometer, and milk production was electronically measured at each milking time during the trial. The experimental design was completely randomized using a 2 × 2 factorial arrangement of treatments. The increase in daily PA decreased plasma concentrations of BHBA (0.91±0. , but did not change milk production. The positive effect of increasing PA was associated with a high herbage intake, while the lack of response to increasing CS supplementation was attributed to a high substitution of pasture intake (0.9 kg DM pasture/kg DM CS). Low corn silage supplementation is recommended.

Short-Term Effect of Daily Herbage Allowance Restriction on Pasture Condition and the Performance of Grazing Dairy Cows during Autumn

“…Moreover, it can be assumed that the increase in herbage DM intake when cows grazed on the high DHA condition could increase the energy intake and decrease the extent of the negative energy balance commonly found in the first months of lactation, and, thus, improve milk production [66]. This assumption could be supported by the results reported by Morales et al [63] who indicated that increasing DHA from 17 to 25 kg DM per cow decreases B-hydroxybutyrate in plasma from 1.12 to 0.91 mmol L −1 .…”

“…The higher milk protein observed in our study at the high DHA was not related to the quality of the feed provided (because forage and MSS quality did not differ in CP nor ME concentrations) or to the total DM intake. The increase in milk protein content when more herbage was offered could be explained by the decrease in the plasma concentration of B-hydroxybutyrate reported by Morales et al [63], which represents a positive effect on the energy metabolism. The milk protein concentration increased by 0.01 g/kg per kg of increase in DHA, which is similar to the results reported by Delaby et al [69].…”

“…As part of two parallel studies conducted on the same herd and paddock with a focus on nutritional aspects [61] and energy metabolic response [62,63], the intake of MSS and concentrate was measured. Cows, in total, consumed 12.1 kg DM forage per day (pasture plus MSS) and 3 kg of concentrate, with no difference among groups.…”

Changes in herbage mass and time of herbage allocation modify nutritional and metabolic status of dairy cows

“…However, β-HB concentrations were not sufficient to be considered indicative of subclinical ketosis (> 1.2 or 1.4 mmol L -1 ) (Duffield et al, 2009;Cucunubo et al, 2013). The above described suggests that the herbage harvested by the PM treatments together with the supplementation offered, was sufficient to satisfy their nutritional requirements of maintenance and production, while the diet consumed by the AM treatments was slightly unbalanced but not enough to generate an effect on milk production (Morales et al, 2016). Emerging the question, if this imbalance can affect the health of the cows or they are able to adapt to these conditions.…”

“…However, these tools are not a sufficiently sensitive measure and only can be associated with general health status (Roche et al, 2013), being necessary to accompany these tools with monitoring through blood profiles. In addition, it is necessary to generate more information on how monitor the health of cows and also how it interacts with the grazing management, especially in early lactation (Morales et al, 2016).…”