Abstract #T16

Section: Animal Health
Session: Animal Health: Lactating cows
Format: Poster
Day/Time: Tuesday 7:30 AM–9:30 AM
Location: Gatlin Ballroom

# T16
Serum calcium concentration during the peripartum period in a Jersey herd grazing tropical pastures and supplemented with a low calcium grain mixture.
Jorge M. l. Sánchez^*1, Alejandro Saborío-Montero¹, ¹Centro de Investigaciones en Nutrición Animal y Escuela de Zootecnia, Universidad de Costa Rica, San José, Costa Rica.

The aim of this study was to analyze the serum Ca concentration in a Jersey herd during the peripartum period in a tropical production system, to compare Ca status in young (≤2nd parity) and adult (≥3rd parity) cows. The study was conducted on a dairy farm located in Cartago, Costa Rica, during a 6-mo period (January–June, 2014) and comprised 161 cows (62 young cows; 99 adult cows). During the close-up period cows grazed lush kikuyu grass (Kikuyuocloa clandestina) (14.8% DM, 23.4% CP, 0.35% Ca, 0.31% Mg and 3.5% K) and were supplemented with 4 kg/cow/d of a low Ca grain mixture (88% DM, 14% CP, 0.2% Ca, 0.42% Mg and 1.38% K) and 1 kg of hay (82.3% DM, 5.1% CP, 0.4% Ca, 0.35% Mg and 1.8% K)/d. After calving, cows were fed 1 kg of grain mixture (87.5% DM, 18.6% CP, 0.90% Ca, 0.42% Mg and 1.38% K)/2.5 to 3.0 kg of milk. A total of 752 blood samples were taken from 4d before calving until 5d postpartum and were analyzed for total calcium. Data were analized as a repeated measures with the fixed effect of parity class and cow nested within parity was the subject of the repeated measure of time. Statistical analysis showed significant effect for category, not so for day and day x category interaction. Means across the 2 categories were compared by Student’s t-test (Table 1). Serum Ca concentrations in young cows were usually greater than concentrations in adult cows. Starting at 1 d before calving through 1 d post calving, serum Ca in adult cows was depressed reaching its nadir at 1 d in milk. Results show that adult cows were subclinically hypocalcemic (serum Ca <8.0 mg/dl) from d 2 before calving until 5 d in milk, requiring feeding practices designed to improve Ca metabolism in the periparturient adult cows. Table 1. Serum Ca concentration (mg/dl) from 4 d before to 5 d after calving for young (1 and 2 parities) and adult (3 or more parities) Jersey cows grazing lush tropical pastures

Category	Day relative to calving
−4	−3	−2	−1	0	1	2	3	4	5
Young	8.41^a	8.18^a	8.19^a	8.37^a	7.57^a	7.85^a	7.90^a	8.15^a	7.97^a	8.09^a
Adult	8.66^a	8.09^a	7.74^a	7.49^b	6.98^b	6.72^b	7.42^a	7.67^a	7.68^a	7.86^a
P-value	0.781	0.901	0.280	0.046	0.027	0.009	0.127	0.092	0.445	0.438

^abMeans in the same column with different superscripts are different (P < 0.05).

Key Words: grazing cow, hypocalcemia, milk fever