No abstract

SUMMARYEight research and teaching centres have co-operated in an experiment involving 132 sows. Six treatments were used, combining three levels of feeding in pregnancy with two in lactation. Pregnancy treatments were High 3−2 kg meal/day, Medium 2·4 kg/day and Low 1·6 kg/day; in lactation either a high level, 4·1 kg plus 0·2 kg/pig (h) or a medium level, 2·3 kg plus 0·2 kg/pig (m) were given. The sows were maintained on the same nutritional regime for three parities although inevitably some sows were lost before the completion of the trial. Sow live-weight gains in pregnancy were directly related to feed intake; in lactation, losses in sow live weight were dependent on gains made in the previous pregnancy and on the level fed while suckling. After the first parity, in which animals fed the low level in pregnancy tended to produce larger litters (though the difference was not significant), there were no differences in numbers born attributable to treatments.Increases in the feed intake of sows in pregnancy resulted in consistent and significant increases in the weight of the pigs at birth. This increase in birth weight also resulted in an increase in weight at weaning in the second and third parities. Level of feeding in lactation, which had a highly significant effect on sow live weight, had much less influence on weaning weights of pigs. There were no consistent pregnancy × lactation interactions, the effects of treatments in the two phases being additive.An assessment is made of the relative efficiency of the six treatments and the value of the experiment is discussed in relation to other studies concerned with sow nutrition.

Synopsis Owing to soil moisture differences, grain yields were increased by 85% and straw yields by 187% in heavily fertilized wheat. Maintenance of the available soil moisture percentage above 30 was necessary for maximum grain yields. The protein content of the whole grain was decreased by small applications of nitrogen and was increased by large applications. Protein content was lowest in the wettest treatment and highest in the driest treatment.

The corn (Zea mays L.) yield data obtained with four levels of nitrogen at 76 locations were combined to give a general equation with yield expressed as a function of applied N variables, productivity factors, and interaction variables. Three regression procedures — stepwise, backward elimination, and an approach based on agronomic considerations — were employed in producing a general yield equation. The pooled blocks within sites error and combined experimental error, calculated from the analyses of the individual experiments, were used for testing the significance of the site variable and plot variable regression coefficients, respectively. High correlations existing between pairs of the independent variables prevented a meaningful interpretation of the coefficients in the estimated regression models. The total variation in yield accounted for by the three regressions was similar, although the terms dropped from the full model in producing the agronomic model resulted in a significant reduction in the regression sum of squares. However, when the estimated models were used to predict yields for sites not included in the estimation procedure, the agronomic model predicted better than the other models.

The effects of selection for low backfat thickness on tissue deposition in different body sites has been investigated in pigs. Eight castrated male and eight female pigs from each of the selection and control lines maintained at the University of Newcastle upon Tyne were used. One castrated male and one female from each line was killed at 15, 30, 45, 60, 75, 90, 105 and 120 kg live weight following ad libitum food consumption and fully dissected.There were only small effects of line on carcass composition, selected pigs having 120 g/kg more bone than controls at the mean side weight (P < 0-001) and 40 g/kg more lean (NS). At the same mean weight of subcutaneous fat, selected pigs had thinner backfat than controls (approximately 3 mm) over m. longissimus at the last rib and over the shoulder but not at the mid-rump or mid-back positions. There appears to have been a slight shift in the sites of fat deposition from above m. longissimus in the loin towards the mid-line and rump as a result of selection, even though mid-rump, C and K measurements were all included in the selection index. However, there was no difference between the lines in the weight distribution of subcutaneous fat between six regions and so these shifts must have been very localized. There was no difference between lines in the relationship between P 2 fat thickness and proportion of lean in the side.The effects of selection on the sites of deposition within tissues other than subcutaneous fat were small. In particular there was no evidence that selection has caused relocation of body fat from subcutaneous to the other sites.