Study of the effects of different levels of winter feeding of North and South Country Cheviot ewe hoggs on their growth, development and subsequent performance

Abstract

1. During the winter of 1956-57, 40 South Country Cheviot and 38 North Country Cheviot ewe hoggs were fed in three groups in each breed on H.P., M.P. and L.P. diets from 27 - 49 weeks. During the winter of 1957 -58, 25 S.C.C. and 28 N.C.C. ewe hoggs were fed in two groups in each breed on H.P. and M.P. diets from 22 - 49 weeks, with 12 S.C.C. and 14 N.C.C. ewe hoggs remaining on the hill as controls. During the winter of 1958 -59, 14 S.C.C. and 15 N.C.C. ewe hoggs were wintered in grass fields and away on a low ground grass farm from 25 - 49 weeks, while 13 S.C.C. and 15 N.C.C. ewe hoggs remained on the hill as controls.2. In the 1956 born age group, hoggs fed on a L.P. diet lost 7 lb. (10%) over the winter, M.P. fed hoggs were maintained in weight, making them 7 - 9 lb. (11 - 13 %) heavier than the L.P. hoggs and H.P. fed hoggs gained 13 - 15 lb., making them 21 - 22 lb. (34 - 35 %) heavier than the L.P. hoggs. In the 1957 born age group, Hill hoggs lost 6 - 10 lb. (10 - 15%) over the winter, M.P. fed hoggs gained 2 - 4 lb., making them 10 - 14 lb. (18 - 24%) heavier than the Hill hoggs and H.P. fed hoggs gained 20 - 23 lb., making them 26 - 34 lb. (47 - 57%) heavier than the Hill hoggs. In the 1958 born age group, Hill hoggs gained 3 - 5 lb. over the winter and Away hoggs gained 9 - 10 lb., making them 6 - 7 lb. (9 - 12%) heavier than the former.3. The live weight changes of these different groups on the hill are examined over the summer after treatment from 12 - 18 months and from 18 months onwards. The differences between H.P. and L.P. /Hill groups were halved by 18 months but were still significant at 2 years. The M.P. groups gave different results in the two breeds, possible explanations for this are discussed. The differences between moderate away wintering and above average hill wintering disappeared by 2 years. After this time differential productivity influenced live weight changes more than treatment.4. Changes in size and conformation as affected by treatment are examined over the winter, from 12 - 18 months and from 18 months onwards, by seven live measurements, heart girth, body length, pelvis length, pelvis width, fore - cannon length, leg length and tibia length. Treatment effects were greater on the body measurements than on the leg measurements and the earlier start to treatment in 1957 created greater differences than the later start in 1956. Significance tended to disappear from the differences in leg measurements by 18 months but remained in certain of the body measurements to 27 and 39 months, particularly the pelvis measurements. Implications of changes in size on future survival and production are discussed.5. Sample animals from each breed prior to treatment and from each treatment group at 12 and 18 months were slaughtered and partially dissected. The relative changes with age as affected by treatment are examined in various body parts, organs and their accompanying tissues of the total carcass and in the joints and individual tissues of the hindquarters. Treatment effects were smaller but more permanent on bone growth, particularly in thickness, than on muscle and fat. The latter tissue showed the greatest response to treatment and the resultant greater "condition" at 18 months of animals wintered on improved diets is discussed with regard to its possible advantage during the first productive year. Dissected bone measurements give complementary information to the live measurements on skeletal size. Greater width growth of the pelvic bone in animals wintered on improved diets is discussed with regard to a re- duction in difficult births, while greater development of the reproductive organs is similarly discussed with regard to a reduction in barrenness and an increase in twin births in the first productive year.6. The relative growth and development of heavy and light hoggs prior to 193 treatment in each treatment group is examined from the changes occurring in live weight and the live measurements over the treatment period, from 12 - 18 months and from 18 months onwards. Treatment effects were greater on the light than on the heavy hoggs but failed to permanently overcome the differences between the weight classes, the latter showing greater potential during the later stages of growth and development than the former. Treatment differences persisted in the light hoggs, significantly so in weight and size to 2 years and still sizable at 3 years but disappeared in the heavy hoggs between 18 months and 2 years. The implications of growth and development at 6 months are discussed with regard to future performance and suggestions are made as to the importance of the first 6 months of life which may warrant greater attention than the winter period.7. Seasonal effects during the first 6 months of life and between 12 and 18 months are discussed in relation to their interaction with wintering treatment and are shown to have a considerable influence on growth and development and on subsequent performance.8. The earlier maturity resulting from improved wintering treatments is demonstrated by earlier eruption of the permanent incisor teeth, particularly the first pair. Possible implications of this on long term productive life are discussed.9. Mortality rate was higher in those groups which received a higher standard of wintering and were the heaviest and largest in later life. Possible explanations for this are discussed.10. Wool production in the first year was very greatly affected by treatment but in subsequent years it was more closely related to the condition of the animals at mating time and to their lamb production in the previous season than it was to treatment.11. Barrenness was generally reduced and twin births increased in the first productive year from those animals which received improved winter diets. Lamb survival was closely related to the condition of the gimmers at 18 months and very greatly affected by season during the first productive year. The percentage of lambs weaned in the first year was therefore greater from the improved wintering treatments but seasonal effects could either exaggerate or diminish these treatment differences. Subsequent lamb crops were less affected by season than gimmer lamb crops and continued to show reduced but more positive treatment differences in the second and third productive years, with L.P. /Hill wintered animals weaning on average 20% fewer lambs than from the other treatments, which were very similar. Treatment effects were generally greater on the number of lambs produced, by reducing barrenness, increasing twin births and reducing twin lamb losses, than on weights of lambs or milking ability of the ewes. A lowering of the overall standard of the lambs is suggested from improved wintering treatments, through greater production and increased chance of survival, as shown by the smaller percentage of ewe lambs retained for replacement from these groups compared with the L.P. /Hill groups.12. General implications of improved wintering treatments on growth and development and the effect of the greater size and earlier maturity so achieved on survival and production throughout the hill productive life are discussed and suggestions are made as to the most economic and efficient rearing systems.