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The excretion of prostaglandin F2α in milk of cows
THERIOGENOLOGY
ABSTRACTS B 0 ST I N E Igboeli, G.: Oairying in Zambia: II. Reproductive efficiency in relation to season and parity in dairy cows. E. Afr. Agric. Forestry 3., 4:189-194, 1973. School of Agricultural Sciences, University of Zambia, Lusaka. The dairy industry in Zambia depends largely on exotic breeds, mostly Friesians. Comparisonsof their performance in a new environment are necessary to justify the continued importation of this and other exotic breeds. Since reproductive causes were the most important single reason for loss or disposal, a survey was conducted indicative for reproductive efficiency in 6 state- or privately owned dairy farms. A total of 2,151 calves were classified as born alive or as stillborn. The peak distribution of calving was in July/August, resulting from matings during the rainy season (November-March), when abundant pasture, mild temperature and high bull fertility prevail. Lowest numbers of calvings were seen in November/December. Stillbirths account for approximately 8.6 $ of all calvings, with the highest rate in October (ca. 15 $) and the lowest in January (ca. 2 $), when prevailing environmental conditions are either hostile or more favorable. Aoe at first calving was 30.7 + 0.4 months; lactation performance (uncorrected milk yield oer cow and lactation) was 3.500 ko. Interval between'calving and first breeding.postpartum was 04.7 + 3.1 days; 5.8 breedings were necessary per conception, and calvTng intervals averaged 424.6 + 3.1 days, varying between months but not between parity, although the distribution curves for calving intervals show a peak between 340 and 400 days postpartum. W. JMchle Manns, 3. G.: The excretion of prostaglandin F&in milk of cows. Prostaglandins, 9(3):463-474, 1975. Dept. Physiology and Enyironmental Studies, University of Nottingham, School of Agriculture, Sutton Bonington, Loughborough, Leicestershire, England. Since PGF- used for induction of luteal regression and synchronization of ovulation might be excreted in milk, an attempt was made to determine simultaneously milk residues and plasma levels by a radioimmunoassay. Milk of untreated cows contained 0.2 to 0.4 ng/ml PGF2a, with a daily excretion rate of 2.9 mcg in low producing, and 7.8 mcg on Day -12 to -4, and 10.8 mcg on Day -3 to -1 of the cycle in high lactating cows (estrus = Day 0). Two of 6 cows had a distinct PGF,, milk peak near estrus after milk progesterone levels had declined, and daily changes in the milk levels of PGF=and proaesterone were not consistently related. After injection of 30 mg PGFzein 4 low producing cows, a plasma peak ;as seen 15 minutes, and the milk peak 1 hr later. Only 0.003 % of the daily excretion rate of 2.9 mcg was due to the amount injected. W.
JUNE 1975
VOL. 3 NO. 6
Jffchle
259
ABSTRACTS B 0 ST I N E Igboeli, G.: Oairying in Zambia: II. Reproductive efficiency in relation to season and parity in dairy cows. E. Afr. Agric. Forestry 3., 4:189-194, 1973. School of Agricultural Sciences, University of Zambia, Lusaka. The dairy industry in Zambia depends largely on exotic breeds, mostly Friesians. Comparisonsof their performance in a new environment are necessary to justify the continued importation of this and other exotic breeds. Since reproductive causes were the most important single reason for loss or disposal, a survey was conducted indicative for reproductive efficiency in 6 state- or privately owned dairy farms. A total of 2,151 calves were classified as born alive or as stillborn. The peak distribution of calving was in July/August, resulting from matings during the rainy season (November-March), when abundant pasture, mild temperature and high bull fertility prevail. Lowest numbers of calvings were seen in November/December. Stillbirths account for approximately 8.6 $ of all calvings, with the highest rate in October (ca. 15 $) and the lowest in January (ca. 2 $), when prevailing environmental conditions are either hostile or more favorable. Aoe at first calving was 30.7 + 0.4 months; lactation performance (uncorrected milk yield oer cow and lactation) was 3.500 ko. Interval between'calving and first breeding.postpartum was 04.7 + 3.1 days; 5.8 breedings were necessary per conception, and calvTng intervals averaged 424.6 + 3.1 days, varying between months but not between parity, although the distribution curves for calving intervals show a peak between 340 and 400 days postpartum. W. JMchle Manns, 3. G.: The excretion of prostaglandin F&in milk of cows. Prostaglandins, 9(3):463-474, 1975. Dept. Physiology and Enyironmental Studies, University of Nottingham, School of Agriculture, Sutton Bonington, Loughborough, Leicestershire, England. Since PGF- used for induction of luteal regression and synchronization of ovulation might be excreted in milk, an attempt was made to determine simultaneously milk residues and plasma levels by a radioimmunoassay. Milk of untreated cows contained 0.2 to 0.4 ng/ml PGF2a, with a daily excretion rate of 2.9 mcg in low producing, and 7.8 mcg on Day -12 to -4, and 10.8 mcg on Day -3 to -1 of the cycle in high lactating cows (estrus = Day 0). Two of 6 cows had a distinct PGF,, milk peak near estrus after milk progesterone levels had declined, and daily changes in the milk levels of PGF=and proaesterone were not consistently related. After injection of 30 mg PGFzein 4 low producing cows, a plasma peak ;as seen 15 minutes, and the milk peak 1 hr later. Only 0.003 % of the daily excretion rate of 2.9 mcg was due to the amount injected. W.
JUNE 1975
VOL. 3 NO. 6
Jffchle
259