Pregnancy rates of dairy cows at first service: influence of gonadotropin-releasing hormone and timing of AI relative to estrus

The 1989 Annual KSU Dairy Day is known as Dairy Day, 1989We demonstrated that gonadotropin-releasing hormone (GnRH or Cystorelin®) failed to improve pregnancy rates at the first service. When GnRH injection and insemination are both carried out either in early or late estrus or if cows are bred in early estrus and given a GnRH injection later in estrus, pregnancy rates are reduced by 9 to 13 percentage points compared to breeding according to the am-pm rule without GnRH treatment (control). Pregnancy rates of cows injected with GnRH early in estrus and bred in late estrus were similar to controls injected with saline and inseminated late in estrus (46 vs 43%). Altering the time of breeding and the time of GnRH injection to either early or late estrus did not improve pregnancy rates. We continue to recommend using GnRH only for repeat breeders, because GnRH consistently improves pregnancy rates at 3rd or 4th service, but not at first services

Reducing bovine leukosis in dairy cattle

Bovine leukosis virus (BLV) is a cancerous condition of tissues in which lymph nodes and lymphocytes are affected. Infected cattle may be identified by testing blood sera for BLV antibodies using the agar gel immunodiffusion (AGID) test that requires 2 days for processing. Most dairy farms have infected animals, but the condition is not considered important because less than 1% of infected cattle show clinical signs. However, many of these cows are culled because of poor milk production or reproductive performance. Procedures for reducing and(or) eliminating the disease are outlined. Results obtained at the Kansas State University Dairy Teaching and Research Center demonstrate that feeding only colostrum and whole milk from BLV-negative cows to newborn and young calves is an effective method of reducing the incidence of BLV in future generations.; Dairy Day, 1996, Kansas State University, Manhattan, KS, 1996

Performance of lactating dairy cows fed alfalfa haylage treated with bacterial inoculants at the time of ensilation

Sixty Holstein cows averaging 65 days in milk at the initiation of a 13-week study were used to evaluate three alfalfa haylages. Haylages were treated at the time of ensilation with either a Pioneer experimental inoculant (Treatment A), no inoculant (Treatment B), or Pioneer brand 1174® inoculant (Treatment C). Cows fed A had greater peak yields and tended to produce more milk than cows fed B and C. Milk fat percentages were 3.7, 3.66, and 3.59 for A, B, and C, respectively. Greater milk yield and butterfat percentage translated into higher (P<.05) daily fat production by cows fed A compared to C but not B

Double inseminations and treatment of repeat breeders with gonadotropin-releasing hormone

An experiment was conducted in one Kansas and five California dairy herds to determine if double inseminations with and without treatment with 100 µg gonadotropinreleasing hormone (GnRH) would improve conception rates of repeat-breeding dairy cattle (n=723). Both lactating cows and virgin dairy heifers were assigned randomly to treatments as repeat breeders, if they had failed to conceive to at least two previous services. Cows inseminated once and treated with GnRH had the best conception rates (41%), which were higher (P<.OI) than those of cows inseminated once without GnRH treatment (32%) and higher (P<.OI) than those of cows inseminated twice without treatment with GnRH (33%). Cattle bred twice that received the GnRH treatment had intermediate rates (37%). We conclude that treatment of repeat breeders with GnRH at the time of insemination (only one service given according to the am-pm, pm-am rule) improved conception rates

Reducing bovine leukosis in dairy cattle

Bovine leukosis virus (BLV) is a cancerous condition of tissues in which lymph nodes and lymphocytes are affected. Infected cattle may be identified by testing blood sera for BLV antibodies using the agar gel immunodiffusion (AGID) test that requires 2 days for processing. Most dairy farms have infected animals, but the condition is not considered important because less than 1% of infected cattle show clinical signs. However, many of these cows are culled because of poor milk production or reproductive performance. Procedures for reducing and(or) eliminating the disease are outlined. Results obtained at the Kansas State University Dairy Teaching and Research Center demonstrate that feeding only colostrum and whole milk from BLV-negative cows to newborn and young calves is an effective method of reducing the incidence of BLV in future generations