ALBERT

Description: SUMMARYSeventy-nine Finnish Landrace x Dorset Horn ewes in lamb to Suffolk rams were used in a comparative slaughter experiment to assess the effects of numbers of foetuses on the growth of the products of conception. The mean number of foetuses was 2·7, with a range from 1 to 5. The ewes were individually penned and given a standard diet with metabolizable energy concentration 7·7 MJ/kg and N concentration 21 g/kg, rationed at 2 kg/day during the first month and 1·25 kg/day during the second and third. Allowances beyond that time were on two scales and depended on the number of foetuses being carried as diagnosed by radiography. The ewes were slaughtered between 50 and 145 days of gestation. The gravid uterus was dissected into foetal, placental, foetal fluid and empty uterus components. Equations were fitted to the weights of each component to describe the effects of stage of gestation, litter size and ewe weight. For the mean weight per foetus (Y, kg) the preferred equation isIn (Y)= 2·419–17·574e-0.01976t–00079ft+0–0046w,where tis the time in days from conception, / is the number of foetuses and wis the weight (kg) of the ewe at mating. This is a version of the Gompertz equation, with additional terms to express the effects of / and w.The weights of the placenta and of the empty uterus were similarly fitted by versions of the Gompertz equation but the mean weight of fluids per foetus (Z, kg) or, rather, its natural logarithm was best described by a third degree polynomial, which isIn(Z) = –11·518 + 0–326t;–0·00316t2+0·0000102t3.None of the weights was significantly affected by the level of feeding in late pregnancy.Estimates of mean weights from the equations and of daily rates of gain in weight from the first differentials of the equations are tabulated against stage of gestation and litter size, and the forms of the weight, growth rate and specific growth-rate curves are illustrated graphically.The equation for foetal weight estimates that at the end of pregnancy the mean weight per foetus is reduced by a factor of 0–89 for each additional foetus being carried. The mathematical model implies that the differences originate in early pregnancy, when the factor is very close to unity, and that the mean weights gradually diverge. In the absence of direct evidence this would appear to be the simplest hypothesis, rather than the assumption in most of the earlier literature that the effect is entirely confined to the last 4 or 5 weeks of gestation.Just before parturition the total daily weight gain of quadruplet foetuses was about 250 g and was associated with a similar gain in weight of foetal fluids, the ratio of fluid weight to foetal weight appearing to increase with litter size. The ewes were clearly under considerable physical stress. It is suggested that this aspect must be closely considered when greater prolificacy is sought.

Description: SummaryMeasurements of 21 bone lengths and breadths were made on radiographs of 215 foetuses of known gestational ages ranging from 50 to 145 days obtained from 80 Finnish Landrace x Dorset Horn ewes. Number of foetuses per ewe varied from 1 to 5, but the main statistical analyses were based on the 22 sets of twins, 34 of triplets and 11 of quadruplets. Equations were fitted to relate each of the linear measurements to foetal weight alone, to foetal age alone, to foetal age together with number of foetuses, and to foetal age together with foetal weight. It was found that there were significant differences between the twins, triplets, and quadruplets in the lengths their bones attained at any specified weight or at any specified age but not when both weight and age were fixed. The relationships to weight and age jointly were significantly closer than to either of them alone even after allowing for number of foetuses. The mathematical model that fitted best was a modified Gompertz equation of the formwhere ywas the measured length, w was the number of days prior to expected parturition, w was foetal weight, wu was an estimate of the expected foetal weight at time u, and P, Q, R and Dwere fitted constants.

Description: SUMMARYSeventy-eight Finnish Landrace × Dorset Horn ewes in lamb to Suffolk rams were slaughtered serially between 50 and 145 days of gestation. The mean litter size was 2·7. The daily feeding regime aimed to provide each ewe with 15 MJ of metabolizable energy (ME) in the first month of gestation and 9·4 MJ in the second and third. Thereafter the ewes were provided with a basal intake of either 9·6 MJ (low plane, LP) or 13·4 MJ (high plane, HP) plus 1·3 MJ for each foetus.For ewes with 2, 3 and 4 foetuses the mean percentage changes in maternal body weight over pregnancy were respectively — 5, — 10 and — 14 (LP) or + 3, — 2 and — 6 (HP). Changes in weights of blood, liver and the empty gastro-intestinal tract through gestation varied with the plane of nutrition but not with number of foetuses. In contrast, udder weight at parturition was dependent on number of foetuses but not on plane of nutrition.Increased hydration of the maternal tissues in late pregnancy tended to mask concurrent losses of body fat. For example, over the last 2 months, HP ewes carrying quadruplets lost on average 1·0 kg in body weight but 5·5 kg of (chemically determined) fat. The latter was lost at a rate which increased up to an average of 170 g/day over the last 2 weeks of pregnancy. Net changes in body protein were estimated to be relatively small, but there was some redistribution, including loss from muscle and gain by the udder. There was no evidence of any demineralization of the maternal skeleton.The practical significance of the changes in body composition is discussed, in particular that of the increasing rates of loss of body fat with increasing litter size. It is suggested that the dangers implicit in these rates of fat loss must be taken into consideration when deciding on dietary regimes and the timing of breeding cycles for highly prolific ewes, or indeed when embarking on a programme of increased prolificacy.

Description: SUMMARYNine individually penned Finnish Landrace x Dorset Horn ewes with a mean litter size of 2·33 were offered a diet containing 63% digestible organic matter (DOM) and 13% crude protein in the dry matter at a daily intake of 0·82 kg DOM (1·3 x maternal maintenance) from 95 to 110 days of gestation. On day 111 DOMI was abruptly reduced to either 0·67 kg (T1, 0·54 kg (T2) or 0·36 kg (T3)/day and kept at these levels until a few days pre-partum.Daily N balance before food restriction was 4·9 ± 0·51 g/day. During the periods 3·9 (S1), 11·17 (S2) and 19·25 (S3) days after food restriction daily N balance was 2·8, 2·8 and 3·6 g for θwes on T1, 1·0,1·0 and 0·8 g for those on T2 and –4·1, -4·0and -4·0 g for those on T3. Total lamb birth weight was 8·0, 7·2 and 6·5 kg for treatments T1, T2 and T3 respectively. Using regression analysis it was calculated that plasma glucose concentration in late pregnancy for ewes with a total lamb birth weight of 8 kg fell below the pre-restriction value of 52 mg/100 ml when daily DOMI was reduced to 747 g. At this intake the plasma FFA concentration was 585/i-equiv./I compared with 288 before food restriction. Corresponding values for daily N balance were 5·1 and 4·9 g. A reduction in daily energy intake below 0·75 kg DOM resulted in a rapid decrease in plasma glucose and N balance, the latter being proportional to the increase in the concentration of plasma FFA. The mean daily loss of N from the maternal body was estimated to be 0·4, 1·6 and 6·1 g for treatments T1 to T3 respectively during the period of food restriction.