ARCHIVE FILE
This article was published in 1976
See the original document
Some Nutritional Factors Which Affect the Fertility of Dairy Cattle.
A.P. Hunter, B.V.Sc., Veterinary Officer, Department of Agriculture, Nowra.
This paper describes and records the results of an investigation of dairy herds in the Illawarra District of New South Wales, to define the infertility syndromes occurring in the area. The investigation concentrated on the nutritional causes of infertility causes which are the least well understood.
Materials and Methods.
The study was commenced by conducting a survey of the fertility of a sample of 40 dairy herds in the district. At the commencement of the survey, the herd breeding records on the 40 properties were examined over a 4 month period for evidence of infertility. The initial investigation attempted to determine the proportion of herd infertility that was caused by the known non-nutritional factors. A search was then made within the remaining herds for evidence of nutritional factors which were considered most likely to occur in the district. These were energy, phosphorus and copper.
The cows in 29 herds were examined for evidence of hypoglycaemia and hypophosphataemia and for any relationship these might have with fertility. Weekly visits were made to the properties and blood samples were collected from cows which had either been mated or had exhibited an oestrus prior to mating, during that week. Blood glucose and plasma inorganic phosphate concentrations were determined from the blood samples collected and the 90-day non-return rate was used as the measure of fertility.
Five herds were selected to participate in a copper treatment trial. The herds were selected because blood samples collected from cattle on these properties indicated a marginal copper deficiency was present. On entering the milking herd after calving, every alternate cow to calve received a single injection of 'Coprin' (400mg Copper Glycinate, Glaxo-Allenburys Pty. Ltd., North Melbourne). The random selection into treatment and control groups was determined by the order of calving.
Results
As it is impossible to cover all the results obtained, some of the more significant findings will be presented in this paper.
A. Glucose and Phosphorus
Blood samples were collected from 971 cows which had been mated and 254 cows which had exhibited an oestrus prior to mating, during the week of sampling.
(1) General Fertility.
The 90-day non-return rate of the 971 cows blood sampled within a week after mating was 66.1 per cent. The 399 Cows mated by natural service had a 68.6 per cent non-return rate and the 572 cows mated by artificial insemination had a 64.3 per cent non-return rate.
(2) Glucose.
The mean blood glucose concentration of the 1,225 blood samples collected was 44.85 mg/100ml. When blood sampled within a week after mating, the mean blood glucose concentration of the 642 cows which 'held' to service at 45.37 mg/100ml., was significantly higher than the 43.60 mg/100ml. mean concentration of the 329 Cows which did not 'hold' to service. Cows with blood glucose concentrations of 25 mg/100ml. or below, had a lowered non-return rate of 46.2 per cent. In general, the herds with higher mean blood glucose concentrations had higher non-return rates. When the non-return rates of cows sampled prior to mating and again after mating were determined, it was apparent that rising blood glucose concentrations at about the time of mating were associated with improved fertility.
(3) Phosphorus.
Owing to a laboratory error, plasma inorganic phosphate concentrations were not available for 68 blood samples. The mean plasma inorganic phosphate concentration for the 1,157 blood samples for which levels were available was 5.49mg/100ml. When blood sampled within a week after mating the mean plasma inorganic phosphate concentration of the 621 cows which 'held' to service at 5.59mg/100ml, was significantly higher than the 5.34mg/100ml mean concentration of the 322 cows which did not 'hold' to service. Cows with plasma inorganic phosphate concentrations of 4.5mg/100ml or below had a lowered non-return rate of 40.7 per cent and 23.8 per cent of the cows sampled had concentrations in that range. When the non-return rates of cows sampled prior to mating and again after mating were determined, it was apparent that rising plasma inorganic phosphate concentrations at about the time of mating were associated with improved fertility.
(4) Glucose and Phosphorus Interaction.
There appeared to be a compensatory effect between blood glucose and plasma inorganic phosphate concentrations in relation to fertility, for there was no depression of the non-return rate of cows which had low blood glucose concentrations if plasma inorganic phosphate concentrations were above 4.5mg/100ml.
B. Copper
The fertility of the cows in all 5 participating herds was improved by the administration of 'Coprin'. With 463 cows in the trial, a total gain of 19.3 per cent on the first service 90-day non-return rate by the treated group was obtained. Treated cows required an average of 1.48 services per 'conception' as compared with 1.88 services required for untreated cows.
C. Incidence of Herd Infertility
In these investigations a herd infertility problem was considered to exist when the first service 90-day non-return rate fell below 50 per cent over the observation period. Twelve of the 40 herds examined were found to have infertility problems. The infertility experienced was attributed to vibriosis infection in 4 herds, faulty artificial insemination technique in 2 herds, hypocuprosis in 3 herds, hypoglycaemia, and hypophosphataemia in 2 herds and the cause of the remaining herd problem was not determined. Thus, of the 30 per cent of the herds examined with infertility problems, 15 per cent were caused by non-nutritional factors, 12.5 per cent were caused by nutritional factors and 2.5 per cent were not determined.
Discussion.
Nutritional factors were probably responsible for lowered fertility in all herds in the survey. Although low concentrations of plasma inorganic phosphate and blood glucose at mating, were associated with low non-return rates, the greatest effect on fertility appeared to be caused by changing plasma inorganic phosphate and blood glucose concentrations about mating. It appears from the data obtained in the survey, that it might be possible to obtain an 85 per cent non-return to first service if all the cows in a herd have rising blood glucose and plasma inorganic phosphate concentrations at the time of mating, provided that there are no other causes of infertility present.