Canine hip dysplasia in German Shepherd Dog-Greyhound crossbreeds.

Nineteen German Shepherd Dog-Greyhound crossbreeds in 7 litters were evaluated by pathoanatomic and/or radiographic examination of their pelves when 12 to 24 months old (mean, 19 months). The prevalence of hip dysplasia in the crossbreeds was 42% (8/19). The prevalence of hip dysplasia in purebred German Shepherd Dog half-siblings in 16 litters produced by parents of the crossbreeds when mated to other German Shepherd Dogs was 35% (16/46). When numerical values were assigned to the pathoanatootmic and radiographic evaluations of the pelves, it was found that the severity of dysplastic changes in the crossbreeds were not significantly different from those changes in their purebred German Shepherd Dog half-siblings. It was concluded that selection for normal hips through mating German Shepherd Dogs with Greyhounds would be no more effective in lowering the prevalence of hip dysplasia than would selection within the German Shepherd Dog breed, which would be more desirable with regard to maintaining the standard of the breed.

Three times a day milking: effects on milk production, reproductive efficiency, and udder health.

Dairy Herd Improvement records from 14 Holstein herds in San Joaquin County, CA were studied. Seven herds were milked three times a day, the other 7 twice a day. Three times daily milking significantly increased yield of 305-d fat-corrected milk. Percentage increases in production were 19.4, 13.5, 11.7, and 13.4% for cows in parity one, two, three, and four or later, respectively. Percentage of milk fat was slightly lower for cows milked three times a day compared with those milked twice a day. Cows milked three times a day had fewer days to first breeding than their twice daily counterparts. First lactation cows milked three times daily had more days to last breeding, more breedings, and consequently, more days open than cows milked twice a day. For second lactation cows milked three times a day, there was no difference in days to last breeding or days open, but they required more breedings than cows milked twice a day. Third and fourth lactation cows milked three times daily had fewer days to last breeding, no difference in number of breedings, and therefore, fewer days open than those milked twice daily. Udder health was evaluated by California Mastitis Test scores. Cows milked three times a day up to their third lactation had higher scores than those milked twice a day. Fourth and later lactation cows had a lower score than cows milked twice a day.

Genetic analysis of California mastitis test records. II. Score for resistance to elevated tests.

A lactation score for rating individual cows for their apparent resistance to elevation of California Mastitis test is described. The score uses the first nine monthly California Mastitis Tests weighted by the number and position of elevated coded tests. California mastitis test readings of negative and trace were coded "normal" and 1, 2, or 3 "elevated". A cumulative lactation score of 21 was assigned to lactations without elevation in coded test, and a score of zero was assigned to lactations with all nine tests elevated. The number and position of the elevated coded tests influenced the 305-day milk yield, and the position of elevated coded tests influenced lactation persistency. Differences were significant among sire progeny groups for the cumulative lactation score. Heritabilities for the cumulative lactation score were .48 +/- .07, .36 +/- .08, .46 +/- .15, and .23 +/- .12 for first, second, third, and fourth or later lactation groups. Selection for a high cumulative lactation score should reduce the occurrence of elevated coded test scores. The genetic correlation between 305-day milk yield and cumulative score was -.31 +/- .13 for first lactation records.

Genetic analysis of California mastitis test records. I. Coded tests.

A sample of 15,965 Holstein lactation records having California Mastitis Test scores for at least the first 9 mo of standard Dairy Herd Improvement production testing were studied for the effects of sire, parity, and year and month of calving. California Mastitis Test readings of "negative" or "trace" were coded normal while readings of "1", "2", or "3" were coded elevated. The frequency of elevated tests increased as parity increased. Effect of year of calving and a trend toward higher percentages of elevated coded test scores was significant. There was no distinct trend in elevated coded test score with month of calving. Sire effect on the incidence of elevation in the coded score was important. Heritability of first and second lactation monthly coded California Mastitis Test scores from a paternal half-sister analysis within herd, year, and season, for sires with at least 25 daughters ranged from .11 +/- .04 to .48 +/- .07. Genetic correlations between the third test and following tests of first and second lactations ranged from .25 +/-.15 to .58 +/- .18.