ALBERT

Description: SUMMARYData are presented for the amino acid contents of 64 litters of Suffolk × (Finnish Landrace × Dorset Horn) foetuses varying in gestational age from 90 to 145 days and in litter size from one to five. The concentrations of glycine, cystine, arginine, proline and hydroxyproline in foetal dry matter increased with age, those for threonine, serine, glutamic acid, valine and methionine remained fairly constant while those for aspartic acid, phenylalanine, histidine and lysine tended to decrease. The most pronounced of these age effects were for cystine and hydroxyproline which increased in concentrations by 60 and 100% respectively over the final 2 months of foetal life. The rates of accretion of the individual amino acids are discussed in relation to estimates of the amounts that may be supplied by microbial protein.

Description: SummaryIn Expt 1, 34 individually-penned Finn Dorset ewes of mean live weight 68 kg were synchronized in oestrus and mated to Suffolk rams. From mating until day 28 of pregnancy each received daily 15 MJ of metabolizable energy (ME) and 225 g crude protein (CP). From day 28 to slaughter on days 34, 41, 48 or 55 half of the ewes continued on this feeding regime and half had their daily intake reduced abruptly to 7·5 MJ of ME and 112 g CP. The mean number of ovulations per ewe was 4·03 (range 2–8) and the mean number of viable foetuses at time of slaughter 3·35 (range 2–6). The combined loss of ova (fertilization failure and early embryonic death) was 14·6% and detectable foetal deaths 2·2%. Level of feeding had no significant effect on these measures or on foetal growth. Foetal growth from 34 to 55 days was described by the equationIn w = 0·962–18·613 e-0·0272t–0·00091t(f–3),where w = foetal weight (kg), t = age (days) and f = litter size. Within-litter variability measured as the S.D. of In w (kg) was 0–081 for twins, 0·108 for triplets and 0·106 for quadruplets and higher multiples.In a second experiment Suffolk × Finn Dorset embryos were transplanted at the rate of two per uterine horn into 15 recipient Finn Dorset ewes. Embryo survival was 72% and foetal weights at 60 days varied from 67 to 146% of the mean value of 66 g. Withinlitter variation in foetal size was only about 70% of that expected for foetuses developing from the variable distribution in their initial positioning that occurs naturally. The correlation between foetal weight and placental weight at day 60 was 0·72 (P 〈 0001) indicating that the association between foetal weight and placental weight in prolific ewes is not confined to late pregnancy.The results of both experiments are consistent with the hypothesis that the greater within-litter variability in birth weight in large litters is controlled by events in early pregnancy.

Description: Inclusion in the diet of concentrations of vitamin E and selenium (Se) above requirement is associated with variable improvements in animal performance and immune function. At the cellular and molecular level, research in the last decade has produced a clearer understanding of the mechanisms underlying the multiple functions of vitamin E and Se and it is apparent that these functions extend beyond antioxidant protection. This paper reviews recent research relating to the functionality of vitamin E and Se in relation to the ewe and her lambs and attempts to relate this understanding to the whole animal level. Important aspects of this improved understanding are descriptions of three groups of seleno-proteins and the appreciation that there is a hierarchy in both the distribution of selenium between tissues and in the synthesis of different enzymes within tissues. In addition, there is diversity in the effects of vitamin E and Se derivatives on immune cell function. Given this heterogeneity in function it is not surprising that published responses for the production and health of ewes and lambs to supplementary vitamin E and selenium are variable and not always positive. Coupled with information on factors influencing variability in supply of vitamin E and Se from fresh and conserved forages and concentrate supplements, this review highlights the need for greater awareness of the importance of adequate supplementation of ewe and lamb diets with vitamin E and Se.