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ABSTRACT: Thirty-one Holstein bull calves were purchased at birth from 3 dairy farms in Eastern Ontario. Each calf was assigned at random to oral treatment with either 5 mg of halofuginone lactate in 10.0 mL of aqueous carrier solution (Halocur, base comprised 10 mg of benzoic acid, 100 mg of lactic acid, and 0.3 mg of tartrazine) or 10 mL of placebo (Halocur base minus the active ingredient, halofuginone lactate) administered 15 to 30 min after morning milk feeding for the first 7 d of life. Intakes of milk, calf starter, and water, and fecal consistency score were recorded daily for 56 d. Calf weights were recorded weekly for 56 d. Fecal samples were taken from all calves at approximately 2, 7, 14, 21, and 28 d of age for isolation of Cryptosporidium parvum oocysts. Logistic and linear regression analyses were used to assess the effect of treatment on the incidence of diarrhea and C. parvum infection status. The odds of C. parvum shedding among calves in the halofuginone lactate-treated group was 70% lower than the odds of shedding among calves in the placebo group. In calves treated with halofuginone lactate, no oocyst shedding occurred until 2 wk of age, whereas 12.5% of calves in the placebo group began shedding oocysts during wk 1. From all ages of placebo-treated calves, 31 of 73 samples (42.5%) were positive for C. parvum, whereas only 15 of 67 samples (22.4%) from all ages of halofuginone lactate-treated calves tested positive. The largest number of C. parvum-positive samples occurred in the third week of life. There was a significant delay of 3.1 d in the incidence of diarrhea among calves treated with halofuginone lactate. Intake of milk and starter, body weight gains, and age at weaning were not significantly different between treatment groups.
Journal of Dairy Science 06/2005; 88(5):1801-6. · 2.56 Impact Factor
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ABSTRACT: The effect of melatonin treatment on intervals from calving to first postpartum estrus and ovulation was determined in Shorthorn cows which calved May 8 to June 14. Melatonin (500 mg in beef tallow) was injected subcutaneously (s.c.) into 20 cows on June 15 (4 to 38 d postpartum). Ovulation was determined from progesterone concentrations in jugular venous blood collected weekly from June to August. Mean intervals to first estrus and first ovulation were significantly longer in primiparous than in multiparous cows (85 +/- 4 vs 55 +/- 3 d and 83 +/- 4 vs 52 +/-3 d). Melatonin treatment caused a significant increase in the intervals to first postpartum estrus (68 +/- 4 vs 58 +/- 5d) and ovulation (68 +/- 4 vs 55 +/- 5 d). Mean plasma melatonin concentrations during the daytime were significantly higher in treated than in control cows one and two weeks after melatonin injection and were within the lower range of nighttime values reported previously for cows. Thus melatonin treatment raised daytime plasma concentrations of melatonin and delayed the onset of estrus and ovulation. These results support the possibility of a role of photoperiod through melatonin secretion in the onset of postpartum ovarian activity in cattle.
Theriogenology 12/1986; 26(5):621-9. · 1.96 Impact Factor
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ABSTRACT: Intervals from parturition to first estrus and to the first three ovulations were studied in 25 Holstein and 31 Jamaica Hope cows in Jamaica. Casual observations for signs of estrus were supplemented by twice nightly observation periods. Samples of blood plasma were obtained twice weekly from all cows and assayed for progesterone. The progesterone profile for each cow was used to determine when ovulations occurred. Intervals and standard deviations from parturition to first, second, and third ovulations were 19.8 +/- 8.8, 39.4 +/- 9.0, and 58.6 +/- 9.2 days for Holsteins, which were shorter than the same intervals for Jamaica Hope cows (28.7 +/- 15.6, 46.9 +/- 13.6, and 66.3 +/- 12.6 days). Intervals from parturition to first detected estrus were 46.0 +/- 21.4 days for Holsteins and 45.5 +/- 18.7 days for Jamaica Hopes. There were no significant differences between seasons of calving in intervals to ovulations or in intervals to first detected estrus. Percentages of cows detected in estrus at the first, second, and third ovulations were 19, 61.9, and 57.8% for Holsteins and 43.3, 55.2, and 73.1% for Jamaica Hopes. Holstein cows kept in a tropical environment are capable of returning to a cycling, rebreedable state and of showing detectable signs of estrus as soon after calving as can be expected reasonably.
Journal of Dairy Science 05/1981; 64(4):672-7. · 2.56 Impact Factor
