The Influence of Cell Mediated Immune Response of Braham Cows on Calving Interval, Post Partum Interval, Colostral Immunoglobulin Concentration, Serum Immunoglobulin Concentration, and Growth of their Calves

The primary objective of this study was to determine relationships between cellmediated immune response (CMIR) of cows and: calving interval; postpartum interval (PPI; calving to estrus); colostral immunoglobulins (IgG-1 and IgM); and calf growth. Multiparous Brahman cows (n=435) were previously evaluated for CMIR. In experiment 1- cows were classified into response groups based on mean and SD of CMIR. High responders were those with CMIR ½ SD≥ the mean (CMIR H: ≥2.8), intermediate cows were within ½ SD of the mean (I: 2.7-1.8), and cows ½ SD≤ the mean were low (L: ≤1.7). Multiparous cows had records for six consecutive calving intervals and associated calf weaning weights. Cows with high CMIR had a greater stayability (P=<.0001) over six calving intervals than cows in the low CMIR group. Cows in the high CMIR group had a tendency towards shorter overall calving interval than cows in the low CMIR group (P=0.06). Calf weaning weight did not differ among CMIR groups (P>0.1). In experiment 2, BW and BCS were recorded at 28-d intervals for 84 d before calving. On d0, d7, and d28 post-calving BCS and BW were recorded. If calves failed to nurse independently within 6 hr after birth, the calf was nursed to ensure colostrum consumption. To achieve milk letdown oxytocin was injected into a tail vessel 6-12 hours post-calving and the cow was milked by hand until the udder was depleted. Colostrum was analyzed for IgG-1 and IgM by ELISA. PROC MIXED and Chi Square procedures of SAS were used to analyze variables with a model including CMIR, calf sex, and their interaction as fixed effects. Cell-mediated immune response was not related to PPI (P=0.9), cow BW (P=0.9) or BCS (P=0.6), calf birth weight (P=0.6), 28 d of age weight (P=0.4), or IgM colostrum concentration (P=0.3). An interaction between calf sex and CMIR was observed for both IgG-1 (P=0.06) and Total IG (IgG-1 + IgM; P=0.06) colostrum concentrations. Cow or calf performance was not related to CMIR class, but there was a tendency for an interaction between cow CMIR class and calf gender. Selection for high CMIR can result in selection of cows which are more likely to remain in the herd long enough to be profitable as they have a greater stayability and shorter calving intervals than their low CMIR herdmates