Sources of Variation and Prospects for Improvement of Productive Efficiency in the Dairy Cow: A Review

Abstract

In this review, "productive efficiency" in dairy cows is defined as the yield of milk obtained in ratio to the nutritional costs associated with maintenance, milk synthesis and loss of body condition during lactation. Improvements in efficiency could occur as a result of changes in digestion and nutrient absorption, maintenance requirement, utilization of metabolizable energy for production or nutrient partitioning. Digestibility can be greatly enhanced by appropriate dietary manipulation. Likewise, it may be possible to reduce maintenance requirements and improve the efficiency with which metabolizable energy is used for milk synthesis by manipulation of the pattern of nutrients presented to tissues. However, these factors apparently do not respond to selection for increased milk yield, and little variation is observed among cows. In contrast, individual cows differ substantially in feed intake and in the partitioning of nutrients among body tissues. Techniques associated with genetic engineering and the early prediction of genetic merit have the potential to improve productive efficiency by manipulation of these processes. However, changes in nutrient partitioning and feed intake during lactation are coordinated by a complex network of controls that accommodate the nutrient requirements of each tissue while maintaining homeostatic balance. Future improvements in productive efficiency will therefore depend on our ability to understand the manner in which these controls operate.

A comparison of energy balance and metabolic profiles of the New Zealand and North American strains of Holstein Friesian dairy cow

“…The strains had a similar degree of BCS change over the first 20 weeks of lactation in the present study; the results thus demonstrate that the NA and NZ strains have a similar level of milk production per unit of energy intake or BW, net of differences in body fat mobilization. This is consistent with the review of Bauman et al (1985), who stated that there is little genetic variation in the partial efficiencies of metabolizable energy utilization for maintenance or milk production. There is however a considerable degree of genetic variation in gross efficiency, principally due to a dilution of maintenance requirements for higher yielding cows (Veerkamp and Emmans, 1995).…”

The environmental impact of recombinant bovine somatotropin (rbST) use in dairy production

“…Over the last century, advances in the genetics, nutrition and management of U.S. dairy cows have resulted in a Ͼ4-fold increase in milk production per cow and a 3-fold improvement in productive efficiency (9,10). This gain in efficiency, referred to as ''dilution of maintenance,'' has been achieved by the cow's greater use of dietary nutrients for milk synthesis and is the basis for historical improvements in productive efficiency (7,9).…”

“…This gain in efficiency, referred to as ''dilution of maintenance,'' has been achieved by the cow's greater use of dietary nutrients for milk synthesis and is the basis for historical improvements in productive efficiency (7,9).…”

Utilisation des produits terminaux de la digestion par la mamelle chez la vache laitière

“…Un accroissement de la productivité des animaux laitiers peut être obtenu par une amélioration de l'efficacité de l'utilisation des nutriments pour la synthèse du lait consécutive à une modification de leur captation par la mamelle (Baldwin et a/., 1980 ;Bauman et al, 1985). En (Mepham, 1982 (Rulquin, 1981(Rulquin, , 1982(Rulquin, , 1983 (Christensen, 1977).…”