Diallel cross of three Moroccan breeds of sheep: I. Lamb growth and carcass traits.

A diallel cross involving three Moroccan breeds of sheep (D'man, Beni Guil, and Sardi) was conducted for two successive years at the Gharb Experiment Station in Morocco. Significant effects associated with breed of sire and breed of dam for live and carcass weights are consistent with differences in mature body size of the three breeds involved. Carcasses of lambs by Sardi sires or out of Sardi dams were the heaviest and those by D'man sires or out of D'man dams were the lightest. Lambs by D'man sires reached the prescribed stage of maturity for slaughter at a younger age than did lambs of Beni Guil sires, and lambs out of Beni Guil dams were younger at slaughter than lambs out of Sardi dams. Because of its genetic potential for high growth rate and carcass weight, the Sardi breed could be used in breeding programs to enhance meat production from sheep in Morocco. With the large and desirable maternal effects expressed by the Beni Guil breed on growth traits and carcass weight per 100 d of age, it could also be used in Morocco as a breed of dam.

Diallel cross of three Moroccan breeds of sheep: II. Reproductive performance and productivity of purebred ewes.

A diallel cross involving three Moroccan breeds of sheep (Sardi, Beni Guil, and D'man) was analyzed by least squares procedures. A total of 456 ewes were mated to 22 rams and this resulted in 528 lambs born from 412 ewes. D'man ewes had by far the highest general performance as measured by total weight of lamb weaned, even though the average live weight per lamb was the lowest for the three breeds; this resulted from the higher number of lambs weaned per ewe for the D'man. The least squares means for litter size at birth per ewe lambing were 2.04, 1.01, and 1.11 for D'man, Beni Guil, and Sardi ewes, respectively. The comparable figures for litter size at weaning were 1.55, .90, and .99, respectively, and the least squares means for total weight of lamb weaned were 20.7, 16.9, and 18.2 kg for D'man, Beni Guil, and Sardi ewes, respectively. The comparable figures for total weight of lamb weaned per 100 kg of ewe weight were 71.1, 44.3, and 41.1 kg/100 kg for D'man, Beni Guil, and Sardi ewes. Conversely, D'man rams had the poorest breeding performances of the rams of the three breeds, and Beni Guil rams had the lowest litter mortality. The breed of ram had only small and nonsignificant effects on all measures of fertility and ewe productivity. The least squares means for number born/ewe lambing were 1.36, 1.35, and 1.44, respectively, for D'man, Beni Guil, and Sardi rams; the comparable least squares means for number weaned per ewe lambing were 1.10, 1.18, and 1.16, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Crossbreeding effects in dairy cattle: the Illinois Experiment, 1949 to 1969.

A crossbreeding project involving the Holstein and Guernsey breeds was conducted at the Illinois Agricultural Experiment Station from 1949 to 1969. All surviving male calves, 989 of the 1061 born, were sold within 2 or 3 d following birth. All surviving female calves born in the first four generations, 723 of the 788 born, were given an opportunity to conceive and produce milk. Those female calves born in the fifth generation (152 of 166 born) were placed in the University herd or sold to commercial dairy farmers. On a basis of a total of 2015 calves born, crossbreds had a 15.6% greater survival rate to sale or 1 wk of age than purebreds. Of the 778 surviving females born in the first four generations, 18.4% more crossbreds than purebreds calved once, and 24.5% more crossbreds than purebreds calved twice. For weight at 18, 24, 30, 36, and 48 mo of age, crossbreds exceeded purebreds by 5.0, 7.0, 4.4, 3.6, and 5.3%, respectively. Crossbreds were 9.3 d older at calving than purebreds and had an average calving interval than was 9.4 d longer than that for purebreds. For yield of milk, fat, protein, and SNF, crossbreds exceeded purebreds by 8.0, 8.5, 7.5, and 3.0%, respectively. The measures of survival, growth, milk yield, and reproduction were approximately combined into an index of income produced per cow. On a basis of income per cow per lactation, crossbreds exceeded purebreds by 14.9%. On a basis of income produced per cow per year, crossbreds exceeded purebreds by 11.4%.

Health care requirements of dairy cattle. I. Response to milk yield selection.

To measure direct response to single trait selection for milk yield and correlated response in health problems, two homologous base populations were formed by pairing 66 Holstein females by sire. Base populations and descendants were managed identically except for selection by milk yield. One base and lineage were mated with sires with highest predicted difference milk (selection group); other base and lineage were mated with average sires in 1964 (control group). Milk yield, supplemental labor, and veterinary and semen expense were recorded specific to each cow. Over 9 yr, 130 selection and 163 control cows were observed. Selection cows yielded more milk but with increase in labor and expense for health care. Estimates of labor for the selection group were greater for mammary, locomotion, and digestion categories and for expense in mammary, respiration, first insemination, and later insemination categories. Labor and expense for reproduction did not differ for genetic groups. Differences between groups in annual estimated labor and expense totaled $27.00. Extra income over feed cost more than compensated for greater health care and semen cost; however, the magnitude of the latter indicates a need for them to be considered when economically evaluating breeding programs where major emphasis is on milk yield.

Body weight changes in lactating purebred and crossbred dairy cattle.

Body weights of 396 first and 205 second lactation cows in the first, second, third, and fourth generations of the dairy cattle crossbreeding project at the Illinois Agricultural Experiment Station were studied. Body weights were taken regularly on each animal during the first 9 mo of each lactation with the first weight being taken 3 to 4 days after parturition and subsequent weights at intervals of 30 days thereafter. Among least-squares means there was a decrease in body weight during the first 1 or 2 mo of lactation and a steady increase thereafter in all breed groups for both first and second lactations. There were differences between cows as well as between months for all breed groups in each generation for both lactations. Sums of squares for months were partitioned into linear, quadratic, and cubic components. A third degree polynomial was fitted for each breed group within each generation and separately for each lactation showing the changes in body weights.