Editor:
Dr. Tom Overton
Assistant Professor of Dairy Management/Nutrition
Department of Animal Science
Cornell University
272 Morrison Hall
Phone:  (607) 255-2878
FAX:  (607) 255-1335
Email:  tro2@cornell.edu

Administration of bST to cows during the transition period

Several investigators have sought to determine whether administration of bST during the prepartum period facilitates the metabolic coordination that must occur as a cow transitions to lactation. The premise underlying this approach is that somatotropin decreases glucose oxidation by peripheral tissues (i.e., muscle) and increases glucose synthesis in liver, thus providing a net increase in the supply of glucose to the animal. Putnam et al. (1999; J. Dairy Sci. 82:982) determined that administration of bST (Posilac) at 28 and 14 days prior to calving increased concentrations of glucose in plasma, and decreased concentrations of NEFA and b -hydroxybutyrate before calving. Concentrations of fat in liver after calving were not affected by treatment; however, cows treated with bST before calving produced 7.3 lbs per day more milk during the first 42 days of lactation. Kinetic measurements of glucose metabolism in these cows indicated that glucose was conserved by administration of bST, thus facilitating the maintenance of adequate glucose supply within cows during late pregnancy (Putnam et al., 1999; J. Dairy Sci. 82:1274). A followup experiment (Michelone et al., 1999; J. Dairy Sci. 82(Suppl. 1):112) failed to repeat the milk yield response of the first experiment (Putnam and Varga, 1999; J. Dairy Sci. 82:982); however, cows in the followup experiment were of a much lower body condition score prepartum (3.25 versus 3.68). Bachman et al. (1992; J. Dairy Sci. 75:1883) reported that administration of bST during the dry period did not affect subsequent milk yield during early lactation. Simmons et al. (1994; J. Dairy Sci. 77:1835) reported that milk yield during early lactation was not affected by administration of bST during the dry period; however, body condition scores of cows in this experiment averaged approximately 3.25 during the late dry period.

In summary, these data suggest that responses to bST administration during the dry period may be affected by body condition score such that fatter cows are more likely to respond to treatment. Further research is required to determine whether differences in responses indeed can be attributed to body condition score (i.e., susceptibility to impaired metabolic health postcalving).

Note -- Posilac is not approved for use in cows before 63 days in milk.

T. R. Overton

Milk Composition in Dairy Cows Selected for High or Low Milk Fat %

A paper from Sweden reported the results of a long-term genetic selection program (M. Akerlind et al., Livestock Prod. Sci., 59:1, 1999). Swedish Red and White cows were selected for either high (HF) or low (LF) milk fat %. Most of the cows (85%) in this study had been selected for 2 or 3 generations. The feeding program was similar for all cows. Grain was fed individually to meet nutrient requirements. There were 27 cows in the HF group and 21 cows in the LF group. The key results from this study are:

1. Average % milk fat was 5.07 (HF) and 4.19 (LF).


2. Average daily milk production was 56.5 (HF) and 65.3 (LF) lbs/day.


3. Average 4% FCM as 65.1 (HF) and 66.6 (LF) lbs/day.


4. Milk protein % was 3.63 (HF) and 3.3 (LF).


5. Milk lactose production was higher in the cows selected for low milk fat %. Milk lactose content was 4.72 and 4.73% for the 2 groups.


6. Feed efficiency was the same for both groups.

This study indicates that a significant shift can be made in milk fat % by genetic selection. However, these cows produced significantly less pounds of milk. Milk production was equal when adjusted to a 4 % FCM basis. Total milk income per day needs to be calculated for these 2 groups. You can do this for your specific milk market and the values for each milk component.

L. E. Chase

1999 Cornell Nutrition Conference

Below are the program and registration form for the 1999 Cornell Nutrition Conference. We are excited about this year’s program, including the preconference symposium sponsored by Cornell. The single-page registration form can be printed below for your convenience. Please contact Dee Brothers (dab2@cornell.edu) or Larry Chase (lec7@cornell.edu) for additional information

Conference registration postmarked on or before October 1, 1999 is $75. Registration postmarked after October 1, 1999 , or taken at the door is $100. MasterCard and Visa are accepted. Checks must be drawn on a U.S. bank; international money orders are also accepted. Registration will not be acknowledged in advance of the conference. There is no partial registration fee. The fee includes one lunch, refreshment breaks, hors d’oeuvres, one dinner and a copy of the conference proceedings. Extra copies of the conference proceedings are also available. You must register for the Zinpro and Alltech breakfasts separately.

Email notification

Please email Tom Overton at tro2@cornell.edu to be added to our list of subscribers for notification of new issues.