H.H. Head

Production and characteristics of manure from lactating dairy cows in Florida

Total quantities of urine and feces excreted daily were collected from 12 lactating Holstein dairy cows averaging 567 kg (1250 lb) on fixed feed intake averaging 20 kg (44 lb) of dry matter per day, or 16 kg (36 lb) of dry matter per day per 454 kg (1000 lb) of body weight. Amounts of total and volatile solids, acid detergent lignin, phosphorus in feces, and phosphorus in urine were determined. Cows excreted an average of 44.6 kg (98.1 lb) of raw waste, 6.08 kg (13.1 lb) of total solids in feces, and 0.16 kg (0.3 lb) of fixed solids in feces daily, expressed per 454 kg (1000 lb) of body weight. Total solids of feces represented 36.4% of the daily diet dry matter intake. These values are greater than table values developed by previous researchers and used to design dairy farm facilities. Feces to urine ratio (w/w) ranged from 1.4:1 to 1.9:1. Fecal grab samples (n = 383) from cows on commercial dairies, for which estimated daily intake of feed was available, had greater acid detergent lignin content (16.9 vs. 13.8%) and about 60% more than cows on the total collection trial (4.2 vs. 2.6%), perhaps due to some ingestion of sand on pasture. For all fecal samples fixed solids percentages were much less than table values developed by previous researchers. Differences may be due, in part, to improved genetic potential of cows, because of increased feed intake, climate, or intensive management practices. Our research also confirmed that the quantity of phosphorus (P) excreted in feces was variable, but depended on intake of dietary P.

Short communication: Effect of estrogen supplemented at dry-off on temporal changes in concentrations of lactose in blood plasma of Holstein cows

The objective was to determine the effect of supplemental estrogen (estradiol cypionate, ECP) at dry-off on temporal changes in concentrations of lactose in blood plasma of Holstein cows as an indicator of rate of mammary involution. Thirty-two Holstein cows (8/group) were assigned randomly to 4 treatment groups: 30-d dry, 30-d dry + ECP, 60-d dry, and 60-d dry + ECP. A single injection (7.5 mL) of cottonseed oil (30- and 60-d dry) or ECP (15 mg) in oil (30- and 60-d dry + ECP) was administered intramuscularly at dry-off. Blood samples were collected from the coccygeal vein of all cows 24 h before dry-off and at dry-off, and then 8 samples were collected throughout the subsequent 48 h to monitor concentrations of lactose in blood plasma. No significant effects of ECP on the overall mean concentrations of lactose were detected. Concentrations of lactose increased and were greatest in blood collected 20 h (520.4 +/- 54.1, 268.1 +/- 48.2, 345.0 +/- 52.3, 418.4 +/- 49.8 microM, for the 4 treatment groups respective to the order listed above) after supplemental ECP and final milk removal. At 40 h, concentrations approached those observed 24 h before dry-off (140.5 +/- 52.1, 57.6 +/- 47.1, 90.1 +/- 51.4, 61.2 +/- 48.4 microM, respectively). Concentrations of lactose at 20 h were positively correlated with milk yield of cows at dry-off. Similar temporal profiles of lactose in blood plasma of cows supplemented or not with ECP indicated that ECP at dry-off did not markedly alter the course of tight junction leakage that typically occurs in mammary epithelial tissue during progressive early involution when milk removal is discontinued.