Consequences of the inscription of local breeds in protected designation of origin cow cheese specifications for the genetic management of the herds

In the mountainous areas of Europe with a humid climate, dairy cattle production is a major agricultural activity, and the milk is often processed into cheese according to protected designation of origin (PDO) specifications. We analyzed the extent to which PDO specifications and/or a mountain environment influence the spatial distribution of estimated breeding values (EBVs) of cows and the herd-year effects (HYEs) for milk yield (kg/lactation) and protein and fat contents (g/kg), as well as lactation ranks and calving months. The study focused on the northern French Alps. A total of 37 023 lactations, recorded in 2006, in 1153 herds were analyzed. The cows belonged to the Montbéliarde (21 516 lactations), Abondance (10 346 lactations) and Tarentaise (5161 lactations) breeds. The two factors of variation considered were the status of the commune where the farm was located in relation to PDO (three categories: area with no PDO, area with a PDO with no milk yield limit, area with a PDO with a milk yield limit) and 'mountain' environment (four categories based on the European regulation: plain, piedmont, mountain and high mountain). In the Abondance breed, the average lactation rank increased with an increase in production constraints due to the PDO or to a mountain environment. In the Abondance and Tarentaise breeds, grouping of calving in winter was most marked in the 'PDO with a milk yield limit' and 'high-mountain' categories. In the Tarentaise breed, no significant effect on any trait and any variable was found in the 'PDO' or 'mountain' categories. In the other two breeds, the average EBV for milk yield decreased with an increase in the constraints due to PDO, with differences of 226 and 93 kg between extreme values in the Abondance and Montbéliarde breeds, respectively. The average HYE for milk yield was higher in the Abondance breed in the 'PDO with no milk yield limit' category than in the other categories (+740 and +1110 kg, respectively); HYE was not affected by the 'PDO' factor in the Montbéliarde breed or by the 'mountain' factor in either breed. Concerning the protein and fat contents, the effect of the 'PDO' and 'mountain' factors depended on the trait, the variable and the breed. The proportion of individual decisions (the farmer makes the decision) v. collective decisions (breed management) concerning herd dynamics in the face of existing constraints is discussed.

Modeling milk production and labor efficiency in modernized Wisconsin dairy herds

The 1999 Wisconsin Dairy Modernization Project was conducted to examine variation in milk production and labor efficiency among herds that had recently expanded. Data were obtained from a sample of Wisconsin herds that expanded between 1994 and 1998. Using rolling herd average milk production in 1998 as the dependent variable in the milk production model, milking frequency, bovine somatotropin use, sprinkler use, average linear somatic cell score, average age at first calving, average days dry, and rolling herd average milk production in 1994 predicted 69% of the variation in milk production. Milking three times daily, using bovine somatotropin, using sprinklers to cool cows, and decreasing linear somatic cell score, age at first calving, and days dry were associated with increased milk production. Each of these variables supports previous research from designed experiments with on-farm results. Variation in milk production is determined primarily by differences in management ability and management practices employed by the dairy producer. Using cows per full-time equivalent as the dependent variable in the labor efficiency model, acres per cow, number of people involved in the milking operation, milking system type, herd size, and interactions between milking system types and herd size predicted approximately 43% of the variation in labor efficiency. As expected, labor efficiency increased with larger herd sizes, fewer acres per cow, and fewer people involved in the milking process. Parallel milking parlors were associated with the highest cows per full-time equivalent followed by herringbone parlors, flat barns, and stall barns.

Associations between winter herd management factors and milk protein yield in Ontario dairy herds

A questionnaire was used to investigate associations between farm management practices in winter and milk protein yield. The questionnaire was completed by 500 dairy producers in Ontario, Canada in March 1994. A high positive correlation (0.96) existed between herd mean for protein yield per day per cow and herd mean for milk yield per day per cow. Therefore, most management practices that were associated with the farm mean for protein yield per day per cow were also associated with the farm mean for milk yield per day per cow. After adjustment for farm mean milk and fat yields, farms that housed dry cows as a separate group had higher mean protein yields than did herds that housed dry cows with the milking herd or the bred heifers. A positive association existed between herd mean for days of lactation and protein yield. Because of the correlation between milk and protein yields, these associations were of small magnitude. Thus, the potential benefit of progressive practices in herd management are primarily related to increased yields of milk and milk components in general rather than specifically to an increase in protein yield.

Additive and nonadditive genetic variance in female fertility of Holsteins

Additive and nonadditive genetic variances were estimated for cow fertility of Holsteins. Measures of fertility were first lactation days open and service period as recorded and with upper bounds of 150 and 91 d, respectively. Six million inseminations from the Raleigh, North Carolina Processing Center were used to form fertility records of 379,009 cows. Data were analyzed with a model accounting for all additive, dominance, and additive by additive covariances traced through sires and maternal grandsires. Variance components were estimated by the tilde-hat approximation to REML. Heritability in the narrow sense was 2% for days open and .8% for service period. Dominance and additive by additive variance as a percentage of phenotypic variation strongly depended on imposition of upper bounds. Heritabilities in the broad sense ranged from 2.2 to 6.6% and were at least twice as large as heritabilities in the narrow sense. Effect of 25% inbreeding was only around an additional 3 d open. Specific combining abilities among bulls were estimated as sums of dominance and additive by additive interactions removing effect of inbreeding depression. Differences between maximum and minimum estimates were in the order of twice the estimated standard deviation, ranging from 1.5 to 6.7 d. Effects of inbreeding and specific combining ability could be jointly considered in mating programs following sire selection.