Total Lamb Research Articles

EFFECTS OF NITROGEN FERTILIZER APPLICATION RATES TO GRASS PASTURES ON LAMB GAINS AND HERBAGE YIELDS

A comparison of lamb gains, calculated total digestible nutrient (T.D.N.) production, and dry-matter (D.M.) yields of grass pasture fertilized at 0, 56, or 112 kg of nitrogen per hectare was carried out from 1961 through 1963. Total lamb gains and T.D.N. production were increased linearly with level of nitrogen fertilization. On D.M. yields both the linear and quadratic effects of nitrogen levels were significant. Year differences in T.D.N. and D.M. production were significant as measured by the quadratic regression. On total animal gain both the linear and quadratic effects of years were highly significant. These results were associated with a relatively short grazing season in 1963.

Fertility, Prolificacy and Lamb Livability of some Pure Breeds and their Crosses

Differences in fertility, prolificacy and livability were studied with Hampshire, Shropshire, Southdown and Merino breeds of sheep and their crosses and with the Columbia-Southdale strain of sheep. The study includes 8 years, 1952-59 with a total of 3620 lambs born, and 2646 lambs weaned from 2962 ewes bred. Traits studied were: fertility, measured by percent ewes lambing of ewes bred; prolificacy, measured by percent lambs born of ewes lambing; lamb livability, measured by percent lambs born alive of lambs born and percent lambs weaned of lambs born alive; and the overall measure of reproductive ability by percent lambs weaned of ewes bred. Significant differences were found between years, age of dam, type of birth and breeds and crosses for all traits studied except between years for the percent of lambs born alive of total lambs born. Age of dam showed an important effect on proficacy with an increase from 126 to 153 lambs born of 100 ewes lambing from 2-year-old ewes to those 9 years and older. Fertility and lamb livability tended to be lower for the young and old ewes than for those of the middle ages. The peak for percent lambs weaned of ewes bred was reached at 4 years of age. A higher percent of single lambs were born alive and a higher percent of single lambs born alive were weaned than of twins. In purebred matings Hampshires, Merinos and Columbia-Southdale, excelled over Shropshires and Southdowns in percent of lambs weaned of ewes bred. Hampshires and Columbia-Southdales ranked highest in prolificacy, and Merinos ranked highest in fertility and lamb livability among the breeds studied. Fertility, prolificacy, lamb livability and over-all reproductive ability were generally higher for crossbred than for purebred matings. Furthermore, there was an upward trend with an increase in the number of breeds involved in the cross. Two-breed crosses tended to rank in somewhat the same order as the dam breed and were not significantly greater than the purebred matings for any of the traits studied. Consistent effects of breeds or breed combinations were not readily apparent in reproductive traits of 3- and 4-breed crosses. Average increases in percent lambs weaned of ewes bred were 2.1, 14.9, and 27.1 for 2-, 3- and 4 breed crosses, respectively, over the comparable averages of the purebred parents.

Vital and operational statistics for a Peppin Merino parent stud flock

Statistics are presented from a Peppin Merino parent stud on seasonal variation in flock fertility, differences in fertility between rams of various ages, lamb mortality, age composition of the ram pool, and the differential we of rams of various ages. Variation of the percentage of lambs born to ewes served was largely due to seasonal differences in the proportion of ewes (2.5 per cent to 26.5 per cent) with twins. The majority (about 7 per cent) of lamb deaths up to 24 hours after birth was due to natural causes. Total lamb mortality up to 21 days of age was 13 per cent of the number of lambs born. Male lamb mortality up to 24 hours, including lambs born dead, was higher than female mortality (17 per cent u. 6 per cent). Age composition of the ram pool and ram wastage indicated a replacement rate of about 25 per cent. Average age of rams was 4.4 years at the time of birth of their offspring. Ram fertility, assessed as the percentage of ewes lambing to ewes mated, was 55 per cent for two year old, 70 per cent for five year old, and 59 per cent for nine year old rams. From a total of 27 to 37 rams in we each year, 10 favoured rams sired 52 per cent to 70 per cent of lambs alive at 24 hours. These favoured rams were also above average age (5.1 years v. 4.4 years). Thus, favoured sires contribute more heavily to the future flock genotype than other sires; firstly because they have more offspring, and secondly, became pedigree records provide the basis for additional favouritism towards their offspring, especially in the choice of stud ram replacements. This operational pattern has the two-fold disadvantage of increasing the generation intervals relevant to flock replacements and of inefficient exploitation of genetic gains already, made. If, as we believe, this operational pattern is currently typical of the foremost studs of the Merino industry, if is a matter of some concern with respect to the implementation of genetic improvement programmes and the progress expected from them.Where present procedures follow such a pattern thy should be largely reversed so as to use a higher proportion of young rams and to mate them to a much larger proportion of the ewe flock.

Sheep farming in New Zealand

New Zealand is primarily an agricultural country. Sixty per cent of all its production, including nearly 100% of its exports, comes from farms and is produced by only 17% of the total labour force. Within the agricultural industry sheep farming is dominant. Wool provides between one-third and one-half of the total exports and lamb and mutton about one-sixth. Over 90% of the wool and lamb produced and about 50% of the mutton is exported.The prominent place that wool occupies in New Zealand’s farming strikes any visitor from Britain. The wool cheque naturally exceeds the income from other sources on the sheep stations of the Southern Alps where Merino sheep are grazed, but on lower hill farms selling cast-for-age or surplus two-tooth ewes to fat-lamb breeding farms and store lambs to hogget fatteners the wool cheque is still usually more than half the income.