Graduate Thesis Or Dissertation
 

Influence of maternal instinct stimulated by calf contact on the hormonal induction of lactation in the bovine

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  • An experiment was conducted to determine the effect a newborn calf would have on initial success rate, lactation performance, infertility and progesterone levels during mammogenesis and lactogenesis in dairy cows undergoing hormonal inducement to lactate. Fourteen Holstein, Brown Swiss and Jersey infertile, non-lactating cows, loaned by Pacific Northwest dairymen, were examined to exclude anatomical or pathological causes of infertility. These cows were randomly assigned in equal numbers to two groups. The treatments imposed were as follows: a) The control group received 0.1 mg/kg body weight of 17-beta-estradiol and 0.25 mg/kg body weight of progesterone per day for seven days. The hormones were mixed together in absolute ethanol at concentrations of 20 mg/ml estradiol and 50 mg/ml progesterone. One-half of the dose was administered subcutaneously at 0800 hr and onehalf at 2000 hr each day. b) The experimental group received the same hormone treatment; in addition, a newborn male Holstein calf was placed with each cow at the start of the hormone treatment and remained until the cow began milking. Blood was collected from all cows ever other day beginning the day prior to initiation of treatment, until day 20 or when milking began. Serum was analyzed for progesterone content by a dextran charcoal radioimmunoassay. Milk production was monitored for the initial 90 days of induced lactation and for 305 days on six of the total cows. The initial success rate for both groups was 100% based on the criterion of producing in excess of 10 kg milk/day during the first 30 days of milking. The mean day to first secretion was 10.1 days for the control group and 8.9 days for the experimental group. The success rate suggests that immediate calf contact was not an important influence whereas the overall technique used appears to have been a positive influence on increasing the success rate. The technique used included semi-isolation of each cow from the start of the injection series to time of milking and inducement in the calving area of the facility. Serum progesterone levels averaged 1.5 ± 0.3 ng/ml for both groups on the day preceding the injection series. Progesterone concentration increased to an average maximum level of 3 ng/ml during the injection period for both groups and returned to near normal (1-2 ng/ml) when injections stopped on day 7. Based on a split-plot analysis, the treatment had no significant effect on progesterone levels during the 20 day period measured. The daily hormone level, but not the interaction of days with the treatment, showed significant changes among days. Similarly, a correlation of .38 existed between maximum progesterone level and day of first milk secretion. A negative correlation of -.33 was found between maximum progesterone levels and the day of the estrous cycle treatment began. The correlation was .40 between the day of maximum progesterone level and the day of first secretion. The control group cows produced an extended 305 day mean of 4292 957 kg of milk compared to 4731 ± 711 kg of milk for the experimental group. Total milk production (extended from 90 days) when compared to the previous lactation, was 52% for the control group and 63% for the experimental group. Average milk production, when again compared to the last lactation but based on six complete lactations (305 days), was approximately 80% for both groups. There had been no improvement noted in any of the infertility cases studied during the four month treatment period. Each cow that was not disposed of following the experiment was further observed for improvement of her infertility problem. Of the six remaining cows, none were diagnosed as having conceived; the induced lactation had not altered any of the infertility conditions.
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