Abstract Lactation curves for several dairy traits in sheep were studied. Data were collected from seven pure breeds, three synthetic breeds and twelve single breed crosses in a 5-year milking trial. Wood's lactation model (y n = an b e -cn ) was used to describe the lactation curves. Actual and fitted lactation curves had the same shape within each trait except for proportion of lactose. Correlations between actual and fitted lactation curves ranged from 0·92 to 0·99 for all traits except lactose (0·24). There was no apparent explanation for the low correlation for lactose content. It was concluded that the algebraic formula can be used to obtain estimates of parameters for sheep lactation curves. However, some caution should be exercised in extending results to proportion of lactose in the milk. Crossbred groups had higher total milk production than pure and synthetic breeds. Lactation curves for crossbred ewes, grouped by breed of sire, had a similar pattern. Finnsheep and Rambouillet-sired crossbred ewes produced proportionately 0·23 more milk than ewes sired by Dorset and Lincoln rams. Breed differences in total milk production were observed among the pure breeds. The Suffolk breed was superior in milk production. All breeds, except the Romanov, followed a similar pattern for lactation curves. The Romanov breed produced milk at a relatively low but consistent level throughout the lactation trial.
Heritability for litter size (total number born alive), postweaning growth rate, and live probe backfat thickness were estimated in a new breed of swine called Managra. The Managra is of recent origin and was developed from a crossbred foundation in which seven breeds were combined. All data used in analyses were from gilt litters. Estimates of heritability were obtained by paternal half-sib correlation and parent–offspring regression. Heritability of litter size was found to be.20 ±.15, growth rate.25 ±.04, and backfat.11 ±.04 from parent–offspring regression analyses. Estimates found by paternal half-sib correlation for the three traits were.59 ±.29,.30 ±.11, and.09 ±.19 respectively.Estimates of the genetic correlation between growth rate and backfat were obtained from the data and indicated that a moderately high negative correlation existed (about −.24).Comparisons of these parameter estimates were made with those reported from long established breeds.
Birth and weaning weights were studied for purebred Finnsheep, Suffolk, Targhee and Minnesota 100; F1 Finnsheep crosses; F2: and standard breed and Finnsheep backcrosses. Finnsheep lambs were the smallest of all lambs at birth, but ranked second among purebreds in 70-day weaning weight (Suffolks, 21.0 kg vs Finnsheep, 17.6 kg). Ewe body weight, grease fleece production and total adjusted weight of weaned lamb were compared among purebreds and crossbreds. The Finnsheep was the smallest pure breed, yielded the lightest fleeces, but produced the heaviest total weight of weaned lamb. The F1 ewes were all heavier and produced more wool than the midparent mean of their respective breeds. They also produced markedly more weaned lamb than did the parental standard breeds. Body weight, wool and lamb production were all lower in the F2 than in the F1 groups. Ewe index was calculated as the total adjusted (male, 70-day equivalent) weight of weaned lamb plus three times the grease fleece weight. The ranking of purebreds was Finnsheep, Targhee, Suffolk and Minnesota 100. Average ewe index values for F1 ewes were greater than those for respective parental and standard breeds. F2 and standard breed backcross ewes had lower index values than did F1 or Finnsheep backcross ewes. Ewe index per unit of ewe body weight was also evaluated. Finnsheep ranked highest, followed by the 3/4 Finnsheep. The Targhee was the best of the standard breeds for this index.
The fatty acid composition of subcutaneous fat from Finnsheep crossbred lambs and three domestic breeds, Suffolk, Targhee and Minnesota 100, were compared. Crossbred carcasses included F1 and backcrosses to each parental domestic breed and the Finnsheep breed. Fat samples were obtained from 164 male lambs during a 2-year period. Fatty acids studied were myristic, pentadecanoic, palmitic, palmitoleic, heptadecanoic, stearic, oleic and linoleic. The ratios of (1) palmitic/palmitoleic and (2) oleic/ stearic were also studied. Year differences for relative percentages of the fatty acids were observed. Significant breed group differences were found for amounts of pentadecanoic, heptadecanoic, stearic and The fatty acid composition of subcutaneous fat from Finnsheep crossbred lambs and three domestic breeds, Suffolk, Targhee and Minnesota 100, were compared. Crossbred carcasses included F1 and backcrosses to each parental domestic breed and the Finnsheep breed. Fat samples were obtained from 164 male lambs during a 2-year period. Fatty acids studied were myristic, pentadecanoic, palmitic, palmitoleic, heptadecanoic, stearic, oleic and linoleic. The ratios of (1) palmitic/palmitoleic and (2) oleic/ stearic were also studied. Year differences for relative percentages of the fatty acids were observed. Significant breed group differences were found for amounts of pentadecanoic, heptadecanoic, stearic and ratios 1 and 2. On the average, F1 Finnsheep crosbred lambs had a higher percentage of myristic and heptadecanoic and a lower percentage of stearic and oleic fatty acids than the average of the three domestic breed lamb carcasses. It was suggested that palatability of F1 Finnsheep crossbred lambs carcasses as compared to the three domestic purebreds may be enhanced because of a greater amount of unsaturated to saturated fats, thus reducing the "tallowy" effect sometimes observed in lamb fat.
Heritability of litter size was studied in three inbred lines of swine. An intra-group regression of the record of the daughter on the record of her dam was made to estimate heritability. A total of 1970 daughter-dam comparisons were made. Only data of the number born alive in the first litter were used. A heritability estimate for litter size for the Minnesota No. 1 was 0.05±0.13, for the Minnesota No. 2 it was −.04±0.10 and for the Minnesota No. 3 it was 0.17±0.14. An overall heritability estimate for all animals studied was found to be 0.03±0.07. None of the heritability estimates obtained were found to be significantly different from zero or significantly different from each other (P>.05). The values found in this study fall within the range of those reported elsewhere, but are considerably less than a major portion of those reported. From this study it was concluded that heritability for litter size is low and the response to mass selection for increased performance within a line or breed will be negligible.
Relationships between linear ear measurements, ear type, and performance of swine were examined by regression and correlation. Three breeds, Lacombe, Managra, Yorkshire, and crossbreds between Lacombes and Yorkshires provided data for the study. Ear measurements were taken from 1061 pigs at weaning and 889 of them again at market weight.Contrary to some beliefs no evidence was found that long flop ears are detrimental to postweaning growth rate, age at market weight, or backfat thickness. Results of this study indicate that in general longer and wider ears at weaning were favorably associated with postweaning growth rate.Sex differences in ear type score and linear measurements were found in some breeding groups although no consistent sex difference among all breeding groups was observed.Backfat thickness appeared to be independently associated with ear type, ear length and width both at weaning and market weight. Ear size increased only 1.5 to 2 times from weaning age to market weight whereas body weight over the same period increased nearly 6 to 8 times.
