Reproductive Systems for North American Dairy Cattle Herds

Effect of Gammulin supplementation during the first 24 d of life on health, growth, and first-lactation performance of Holstein cows

Development and health during calfhood are paramount for the success of dairy operations because they are associated with longevity and productivity later in life. Thus, provision of nutritional supplements has been explored as an alternative to improve growth of preweaned calves. Holstein calves (female = 472, male = 46) from 2 dairies located in the San Joaquin Valley were assigned randomly to receive 25 g/d of Gammulin (APC Inc.) from 2 to 24 d of age (GAM = 263) or to receive no supplementation (control = 255). Calves were fed a mixture of waste milk and milk replacer (3.79 L/d), and study personnel added the supplement to the bottles of calves in the GAM treatment daily. Study personnel monitored calves 6 d/wk and recorded starter intake, fecal score (1 = firm, 4 = watery), and attitude score (1 = alert and responsive, 4 = recumbent). Blood samples were collected (4, 7, 14, 26, 44, 56, and 68 d of age) to determine concentrations of total protein, glucose (n = 64), nonesterified fatty acids (n = 64), β-hydroxybutyrate (n = 171), and hematocrit (n = 518). Calves (n = 64) were treated with 0.5 mg of ovalbumin at 3, 21, and 42 d of age, and concentration of anti-ovalbumin IgG was measured. The percentage of polymorphonuclear leukocytes positive for phagocytosis and oxidative burst after the ex vivo exposure to an enteropathogenic Escherichia coli was evaluated (n = 64). We followed the female calves through the end of the first lactation or until they left the herd to evaluate the effect of treatment on first-lactation performance. Treatment did not affect metabolic and immune responses. During the supplementation (1 to 24 d of age), starter intake did not differ between treatments, but the GAM treatment reduced starter intake (638.5 ± 1.1 vs. 696.6 ± 1.1 g/d; mean ± standard error of the mean) from 25 to 60 d of age and average daily gain (798.8 ± 15.4 and 749.5 ± 15.2) from 23 to 60 d of age, resulting in reduced body weight at 60 d of age (68.4 ± 0.4 vs. 69.8 ± 0.5 kg). From 1 to 24 d of age, GAM treatment reduced the number of days calves had fecal score = 4 (ratio of number of days = 0.92; 95% confidence interval = 0.84-1.00) and it reduced the number of electrolyte treatments calves received (ratio of number of treatments = 0.92; 95% confidence interval = 0.85-0.99). Treatment did not affect the hazard of first calving and first-lactation 305-d milk yield, but the adjusted hazard ratio (0.82; 95% confidence interval = 0.65, 1.04) of pregnancy in the first lactation tended to be reduced for the GAM treatment. In the conditions of this experiment, supplementation with 25 g/d of GAM to the liquid feed from 2 to 24 d of age did not improve calfhood health and performance.

Relationship between sire predicted transmitting ability for daughter pregnancy rate and daughter's reproductive performance and milk production in Japanese dairy herds

Modern genetic improvement in dairy cattle is directed towards improvement of fertility; however, reproduction traits generally exhibit a genetic antagonism with milk yield. Herein, we aimed to clarify the effects of sire predicted transmitting ability (PTA) for daughter pregnancy rate (DPR) on the reproductive performance and milk yield of daughters in Japanese dairy herds. We conducted a retrospective cohort study on four dairy herds in eastern Hokkaido, Japan, using 1,612 records from 1,018 cows with first, second, or third calvings between March 2015 and September 2018. First, we classified sires into three groups based on the tertile value of their DPR estimate: ≤ −2.2 (low), −2.1 to −0.4 (intermediate), and ≥ −0.3 (high). Subsequently, we compared the sire PTA estimates, reproductive performance, and milk production among DPR groups for each parity of the daughters. In the first and second parity, the hazard of pregnancy by 200 days postpartum was highest in cows from the high-DPR group (P < 0.05); in the third parity, it was unaffected by DPR group. Although sire PTA for milk production in cows from the low-DPR group was highest, actual milk production was unaffected by DPR group regardless of parity. Our findings demonstrate that using sires with PTA for high fertility can enable farmers to improve reproductive performance without decreasing milk yield in Japanese dairy herds. However, it should be noted that sires with PTA for high fertility are at risk for reducing the genetic merit for milk production.