Parturient and metabolic disturbances in the cow and their influence upon milk production
Authors: Mäkelä Aarne 
Published: July 2018

The present investigation deals with the occurrence of parturient disturbances and certain metabolic diseases in Ayrshire cows at the Viik Farm and the effect of these disorders on milk production, especially during the ascending phase of lactation. The experimental material consists of the daily milk weighings and the health data on lactating cows which have been kept on record since the year 1947. The number of cows in the herd has been about 70, and approximately 900 calvings have occurred between 1947 and the end of the control year 1961—62. In evaluating the influence of parturient and metabolic disturbances on milk production, endeavours were made to estimate how much the disturbance changed the shape of the lactation curve at the ascending phase and decreased the peak production. In connection with some of the disturbances, the effect on the total milk production during the 12-month lactation period was also estimated. The metabolic disorders (parturient paresis, grass tetany and ketosis) were generally treated by a veterinarian. In cases of afterbirth retention and difficult calving, the herd foreman performed the necessary measures. The results found in this investigation were as follows: Retention of afterbirth occurred in 10.8 % of the calvings. It was relatively more frequent in older cows than in heifer cows. In general this disorder did not affect lactation or caused only a slight decline in milk yield at the beginning of lactation. Difficult calving occurred in 3.1 % of the calvings. It was relatively much more frequent in heifer cows than in older animals. There was generally no influence on lactation as a result of difficult calving or only a slight decline in milk production at the beginning of lactation. Twinning occurred in 1.6 % of the calvings with a normal gestation period. When the calves were alive at birth, there was no adverse effect on milk production. The birth of a dead calf occurred in 2.0 % of the calvings with a normal gestation period. Its effect on milk production varied in the individual cases. Sometimes there was no effect at all on milk yield, whereas other times there was a decrease in milk production at the beginning of lactation or a reduction in the production peak. In some cases a loss of as much as 500—600 kg (10—16 %) during the 12- month lactation period was observed. Abortion occurred in 1.5 % of the calvings when the duration of gestation was from 178 to 267 days. The effect of abortion on lactation depended essentially on the number of times the cow had calved and on the length of gestation. When the cow calved for at least the fourth time and the gestation period was 234—265 days, abortion had only a mild influence on milk production. When the cow aborted at its second calving and the gestation period was 184—246 days, its 12-month production was 1000—3000 kg less than expected. In those cases when the cow aborted at its first calving and the gestation period was 178—236 days, its udder was generally so undeveloped that it produced no milk. Parturient paresis occurred in 5.3 % of the calvings. It occurred commonly in high-producing animals and was more frequent in older cows than in younger ones; in addition, it was relatively more frequent during the winter than the pasture feeding period. The disease began most usually on the day of calving or on the following day. Subcutaneous injection of vitamin D proved to be an effective prophylactic measure against this disturbance. When parturient paresis occurred on the day of calving or the following day, it generally had a severe effect on milk production at the very beginning of the ascending phase of lactation (Fig. 1). Its effect on the peak, however, was slight or nonexistent. The reduction in the 12- month milk production caused by this disease was most often 50—100 kg. When the disease occurred at a later stage of lactation, its influence lasted only about 3—5 days and reduced the milk production by 10—40 kg. Grass tetany occurred in 4.3 % of the calvings. It occurred generally in high-producing animals and was more frequent in older cows than in younger ones; furthermore it usually occurred at the beginning of the pasture period, most often in cows which had recently calved. Effective preventative measures against grass tetany proved to be a long transitional period between winter feeding and pasturing as well as the use of magnesium-containing mineral salts on the pasture. In about 1/5 of the cases of this disease, the animal died or had to be slaughtered. Even in those cases when the cow recovered, the disease grealty reduced the daily milk yield and its adverse effect lasted for a long time (Figs. 2 and 3). When grass tetany occured during the first month after calving, the 12-month milk production was decreased by several hundred kilograms, even as much as over 1000 kg. On the other hand, when the disease occurred 2—8 months after calving, the loss in milk production was generally only a hundred kilograms or somewhat more. Ketosis occurred in 3.4 % of the calvings, being prevalent generally in high-producing cows. It did not occur in heifer cows, but among the other cows it was equally frequent in the younger animals as in the older ones. The disease usually began during the first month after calving. It greatly reduced the daily milk yield and at the same time its effect lasted for a long time (Figs. 4 and 5). The average decrease in production for the 12-month lactation period was estimated at 300 kg (6 %), ranging from 0 to 600 kg (0—12 %). The frequent occurrence of parturient paresis and grass tetany in certain families and generally several times in the same cow indicates that hereditary factors have a significance on the occurrence of these diseases. In the case of ketosis, however, no such hereditary influence was observed. Since both of the former diseases often occurred in the same cow, they were considered as a single disorder in examining their repeatability in the cows. Statistical examination showed that the repeatability of parturient paresis and grass tetany among the cows in the present investigation was rather significant.