An investigation of the fertility of a random sample of waikato dairy herds

Abstract

Extract

Inability to get cows to calve at the required time is a serious problem in the dairy and beef industries. It is particularly important to dairy factory supply herds in New Zealand, where COWS must calve during late winter to make the best use of the spring and early summer growth of pasture. The New Zealand Dairy Board has given, the overall incidence of dairy herd infertility and has described the main type which occurs. The Board's data are summarized here :

a.	60 to 66 per cent. (average 62 per cent.) of cows in 41 herds from 1940 to 1951, and 61 to 64 per cent. (average 63 per cent.) of COWS in 184 herds from 1945 to 1951, held to first service. (New Zealand Dairy Board, Report No. 28, 1952.)
b.	5.6 to 11.2 per cent. (average 7.9 per cent.) of cows in 41 herds from 1940 to 1951, and 5.7 to 8.1 per cent. (average 7.0 per cent.) of cows in 184 herds from 1945 to 1951, were empty at the end of each breeding season. (Report No. 28, 1952.)
c.	The fertility level of individual herds varied from year to year. Within a period of seven years, nine of a random sample of twelve herds had at least one season in which the first service N.R. (non-return) rate was less than 50 per cent. and ten of the twelve herds had at least one year in which the first service N.R. rate was 70 per cent. or higher. (Report No. 28, 1952.)
d.	Each year approximately 15 to 20 per cent. of herds experienced a breeding problem. (Report No. 28, 1952.)
e.	The problems were mainly of temporary, sterility—i.e.; a low proportion of cows holding to first service with a high proportion of cows empty at the end of the breeding season. Eighty percent of these empty cows held when mated in the next breeding season. (Report No. 23, 1997.)
f.	Approximately half of the empty cows are culled at the end of their current lactation. (Report No. 23. 1947.)
g.	3.63 per cent. of 246,989 cows were culled in the 1955–6 season for sterility and/or abortion. This was 20.4 per cent. of the total herd wastage in the sample and was by far the biggest cause of disease culling.
h.	There was no evidence that high-producing cows were less fertile than low-producing cows. (Report No. 32, 1956.)