Lamb Weaning Research Articles

A note on correction factors for lamb birth and weaning weights from sheep recording under field conditions

SUMMARYA small scale ewe-recording scheme, involving a minimum of weighing, is described. Results for two years and two breeds have been analysed to produce correction factors in each year for birth type, sex and age of dam in respect of birth weights and weights at 84 days of age derived with and without reference to birth weight. The results suggest that breed differences in correction factors may exist and that differences between years in correction factors may be of minor importance. In standardizing weaning weights to a constant age the influence of birth weight appeared to be relatively unimportant.

A note on the management of grazing, non-lactating ewes

Weaning lambs at 8 to 10 weeks of age is widely practised in the U.S.A. The practice results in the ewes being dry for relatively long periods and affords an opportunity to reduce feed costs during that time. Jordan and Hanke (1964) maintained non-lactating ewes in drylot on 2 to 2·5 lb of legume hay per ewe daily, and Jordan and Marten (1965) doubled the number of ewe grazing days (carrying capacity) by restricting the time the ewes were permitted to graze per week to about 50% of normal. In neither study was subsequent wool or lamb production reduced.

Factors affecting production records of lambs from a flock of East African Blackheaded sheep

1. The effects of age of ewe, and year, sex and type of birth of lambs on lamb weights between birth and weaning were measured and appropriate correction factors estimated in a flock of East African Blackheaded sheep maintained over an 11-year period in Western Uganda. These correction factors were then used to examine the effects of a long dry season at different stages of lamb growth.2. On birth weights the effects of sex ranged from 0-25 lb. to 0-40 lb.; twinning 1-0 lb.; gimmer's lamb 0-5 lb. On 2-month weights the corresponding adjustments were 0-2 lb.-l-4 lb.; 5-1 lb.; 1-7 lb. On weaning weights 0-3 lb.-2-9 lb.; 6-0 lb.; 2-6 lb.3. A long dry season during late pregnancy did not appear to affect lamb birth-weights and a dry season between 2 months and 5 months of age did not affect lamb weaning weights. However a dry season during the main suckling period from birth to 2 months of age significantly lowered lamb weights at 2 months of age.

人工乳によるめん羊の早期離乳と季節外繁殖について

早期離乳しためん羊につき,人工乳および育成用飼料による子めん羊の育成試験と,母めん羊の非繁殖期に,ホルモン剤を利用した季節外繁殖について試験を実施した.1. 早期離乳試験:早期離乳した子めん羊に人工乳および育成用飼料の給与量と期間について,多少異なつた方法で育成したそれぞれの区間には発育,健康状態とも差はなく,また,自然哺乳した子めん羊と比較した場合も差は認められなかつた.この結果から,子牛用人工乳は子めん羊育成用飼料として効率の高いこと,および給与については簡易な方法で行なつても良好な成績をうることがわかつた.2. 生後81日令以降の育成試験:人工乳および育成用飼料により育成したものと生後80日令まで自然哺乳したものを,90日間育成用飼料により育成した結果,1日当りの平均増体は早期離乳区の平均が192g,自然哺乳区は157gで早期離乳区がまさり,5%水準において有意差が認められた.3. 季節外繁殖試験:分娩後20日と25日離乳区および自然哺乳中の母羊について,ホルモン注射による季節外繁殖を実施した(分娩後34～100日).ホルモン注射による発情の誘起率およびその持続時間と受胎率についてしらべた結果,20日離乳区が最も良好であり,次いで25日離乳区,自然哺乳区の順となり,特に自然哺乳区は発情が微弱で持続時間も短かく,いずれも不受胎であつた.なお本試験で分娩した母羊9頭につき産後の発情を調査したところ,いずれも35～40日以内にふたたび発情し年内に妊娠した.以上の結果から,季節外繁殖する場合には早期離乳によつて,産後の回復と同時に母羊の体力を短期間に正常に戻すことが必要と考える.

The influence of various factors on survival rate to weaning of Merino lambs. I. Sex, strain, location, and age of ewe for single-born lambs

The influence of sex, strain, location, and age of ewe on survival rate to weaning of single-born Merino lambs has been examined in two sets of data: the strain trial, involving five strains run without selection at each of three locations (Cunnamulla, Qld.; Armidale, on the northern tablelands of New South Wales; Deniliquin, in the Riverina area of New South Wales), with six age groups of ewes; and the same five strains later included in selection groups at Armidale with seven age groups of ewes. The strain trial at Armidale ran mainly on native, and the selection groups mainly on improved pastures. Female lambs had a higher survival rate than either castrated or entire males, the differences in lambs weaned per lamb born being 0.03 and 0.04 respectively. No strain differences could be regarded as statistically significant, and neither could the strain x location interaction in the strain trial. Mean survival rates for the strains ranged from 0.673 to 0.786 on the Armidale native and from 0.802 to 0.850 on the Armidale improved pasture, from 0.746 to 0.859 at Cunnamulla, and from 0.838 to 0.894 at Deniliquin. The strains did not rank consistently in the same order. Location had a marked effect on survival rate, the means being 0.744 for the native and 0.824 for the improved pasture at Armidale, 0.810 at Cunnamulla, and 0.868 at Deniliquin. Age of ewe had a marked influence in the poorest environment (Armidale native pasture), survival rate rising with age and later falling sharply. The effect was less marked in the intermediate environments (Armidale improved pasture and Cunnamulla) and negligible at Deniliquin. The patterns at Cunnamulla and Deniliquin are confirmed by data from other experiments on these stations. Survival rate is one component of number of lambs weaned. The other component, number of lambs born, has a higher mean value at Deniliquin than Cunnamulla, but shows a strong association with age of ewe in both environments. Number of lambs born responds rapidly to selection, but no information is yet available concerning the likely response in survival rate. If improvement in environment can raise the survival rate, particularly in the youngest and oldest ewes, then selection for number of lambs born, combined with improved environment, should lead to a marked rise in the number of lambs weaned.

The early weaning of lambs

1. The literature on the early weaning of lambs has been reviewed.2. Four experiments were carried out at the Grassland Research Institute, Hurley, during 1959, 1960 and 1961 on the early weaning of Suffolk x Half-Bred lambs. The technique used involved weaning one of a pair of twin lambs at ages varying from 15 to 28 days.3. In 1959 oneof each of apair of six twin lambs was weaned on to grass alone at 15–20 days. No losses occurred, but the weaned lambs grew very slowly. The unweaned twin lambs remaining with the ewes (i.e. reared as singles) grew at rates comparable to those of single lambs.

Liveweight-productivity relationships in sheep

The relationships between liveweight at mating, lamb drop, lamb growth rate, and f1eece weight in Corriedale ewes have been studied by the analysis of data derived from 36 different mobs of ewes extending over several years and comprising 3,910 sheep. Lamb drop or twinning is significantly and positively correlated with liveweight, values being +0.63 between mobs and +0.15 within mobs. Regression of percentage twins on liveweight gives values equivalent to increases of 8.2 per cent between mobs and 4.6 per cent within mobs for a 10 per cent increase in liveweight from 100 lb to 110 lb. Lamb weaning weight is correlated with ewe liveweight to the extent of +0.08 (within mobs) and increases by only 1.8 per cent per 10 percent increase in liveweight. The correlation of f1eece weight with liveweight is +0.24, and f1eece weight increases by 4.3 per cent (within mobs) for each 10 per cent increase in liveweight. The increases in lamb and wool production with increasing liveweight are of approximately t...

EFFECT OF AGE AT WEANING OF SHROPSHIRE LAMBS ON WEIGHT GAINS AND CARCASS SCORE

Differences in the rate of gain from birth to 140 and 170 days of age for lambs weaned on grass-white clover pasture, at average ages of 10, 15 and 20 weeks, were not significant (P < 0.05) as measured by the linear and quadratic regressions. The average weights at weaning were 39, 54 and 66 pounds respectively. The rates of gain of the lambs were affected by type of birth, sex and year of rearing.The age at weaning, type of birth and year of rearing had insignificant effects on the commercial grades of the carcasses from wether lambs.None of the interaction effects for any of the response criteria studied reached statistical significance.The results indicate that certain advantages from early weaning of lambs on pasture with ample immature forage were realized without adversely affecting the performance of carcass grades.

An experimental study of the early weaning of lambs

Two early weaning experiments are reported. When grazing young, high protein pastures, lambs weaned at 7, 10, 13 and 18 weeks of age grew equally well and there were no significant differences between their carcass weights, grades, and dressing percentages.However, when grazing pastures in the preflowering and flowering stages of growth, lambs weaned at 8 weeks of age did not grow as well as unweaned controls. Their carcass weights, grades, and dressing percentages were also inferior. It is suggested that these differences were primarily due to an inadequate protein intake.No difference in wool production was found either between the ewes of early weaned and control lambs, or between the lambs themselves.

Adjustment of Milk Lamb Weaning Weights to a Standard Age

Adjustment of Milk Lamb Weaning Weights to a Standard Age

Observations on survival and growth to weaning of lambs from ewes with defective udders.

Although work has been published showing relationships between milk production of the ewe and growth of the lamb, little has been done to investigate the effects of physical impairment or deficiency in mammary function in the ewe on the survival and growth of the lamb. This point has been studied by examining data for survival, birth weight, daily gain in weight to weaning age, and weaning weight from 621 Merino lambs born in the F. D. McMaster Field Station, C.S.I.R.O., flock from 1946 to 1949. When the performance of lambs from ewes having impaired or imperfect udder function was compared with that of lambs whose dams had normal function it was found that the lambs from ewes having defective function had a lower survival rate, a lower daily gain in weight to weaning age, and lower weight at weaning. The differences were statistically significant. Examination of the dry ewe flock in 1946 revealed that approximately 6 per cent. of all ewes aged from 1 to 7 years had damaged or imperfect udders. There was an association between age and incidence of defective udders, the incidence being highest among the oldest ewes. Culling of affected ewes from the flock was found to have very little effect in increasing the overall percentage of lambs raised to weaning age, or increasing their weaning weight. It is doubtful if culling for this fault would be beneficial in the average commercial Merino flock.