The interplay of feeding and genetics on heifer rearing and first lactation milk yield: a review.

Abstract

Weight gain of young dairy replacement heifers, even over several months, is highly variable, lowly heritable, and a poor indicator of either weight at calving or first lactation milk yield. Voluntary forage consumption is much less variable, more heritable, and a better predictor of weight at calving and milk yield. Weight at calving is highly heritable but not correlated genetically with milk yield. Heavier weight at first calving due to feeding and management does increase milk yield. When grain is fed according to milk yield, weight loss during the first month or two after calving and milk yield are under strong genetic control and tightly genetically correlated to each other and to energy intake. The feed to milk ratio is managementally determined. Better-grown heifers eat more forage and can tolerate more grain consumption without digestive or metabolic disorders. Good body condition at calving seems essential for high milk yield. Genetic ability to mobilize body condition to increase milk yield justifies more grain and results in greater total efficiency up to the point of causing digestive disorders. Good heifer rearing is essential to high milk yield and feed efficiency. Realizing genetic potential for high yield demands excellence of feeding and management during lactation.

Limits to sustained energy intake. XIV. Heritability of reproductive performance in mice

“…Females with a higher SusEI thus raised larger pups and this may benefit their offspring later in life, as many studies have shown that low birth mass is associated with higher risk of cardiovascular diseases, hypertension, diabetes and metabolic syndrome as adults (Whincup et al, 2008), although a relationship between body size and longevity was not found in MF1 mice (Speakman et al, 2004b). Dairy cows have been selected for high milk yields for many years and heritability of milk yield in dairy cows is estimated to lie between 0.04 and 0.67, but varies between different herds, depends on the generation of selection and is subject to sampling errors (Dechow and Norman, 2007;Lee, 1997;Schneider and Vanvleck, 1986;Vanvleck and Bradford, 1964;Veerkamp, 1998). In agreement with the present study, food intake and milk yield (or MEO) have been shown to be highly correlated (0.46-0.65 in dairy cows, 0.72 for MEO in the present study) and estimates for heritability of food intake during lactation and milk yield are generally similar (Veerkamp, 1998).…”

“…It is well known that milk yield in dairy cows is a heritable trait and dairy cows have been selected for high milk yields for many years. Heritability of milk yield in dairy cows has been estimated to be between 0.04 and 0.67 (Dechow and Norman, 2007;Lee, 1997;Schneider and Vanvleck, 1986;Vanvleck and Bradford, 1964;Veerkamp, 1998) and milk yield is generally found to be highly associated with food intake (Veerkamp, 1998). To test the hypothesis that SusEI is a heritable trait, we bred two generations of MF1 mice and monitored their food intake, milk energy output (MEO) and the mass of their litters throughout lactation.…”

Rearing strategy and optimizing first-calving targets in dairy heifers: a review

“…Milk yield and reproductive performances are genetically negatively correlated (Lee, 1997;Boichard et al, 1998;Pryce et al, 2004). Moreover, fertility of both dairy heifers and cows has declined over the last 10 years (Barbat et al, 2005).…”

Growth of Holstein calves from birth to 90 days: the influence of dietary zinc and BLAD status1

“…Although absolute weight gain is an important indicator, it must be accompanied by appropriate growth in skeletal and lean body mass. Given current controversies regarding age at first calving and subsequent lactation performance, there is a need to develop growth references representing contemporary standards of Holstein growth (Hoffman, 1997;Lee, 1997;Heinrichs, 1998). We have provided models of normal growth in female and male Holstein calves (Tables 6 and 7).…”