Effects of calving induction on subsequent milk yield and reproductive performance of cows from seasonally mated New Zealand dairy herds

A longitudinal study of reproductive performance and management of 82 dairy herds in the Waikato region with differing policies on the routine use of induction of parturition

AIMS

To describe the reproductive performance and management practices over three lactations in dairy herds that had different policies on the routine use of induction of parturition; to describe any change in outcomes in herds that ceased inductions during the study period; and to investigate other herd-level factors associated with reproductive performance.

METHODS

From 2002 to 2004 inclusive, a longitudinal study was undertaken in 82 herds in the Waikato region of New Zealand. The main outcome variables were the percentage of cows pregnant after 8 weeks of mating (8-week in-calf rate) and the percentage of cows not pregnant at the end of mating (final empty rate). Data were obtained from pregnancy diagnosis records from a veterinary practice and from an electronic database, and a questionnaire. Herds were classified as either not using inductions in the three lactations (Nil; n=14), ceased inductions in the second or third lactation (Transitional; n=12), or continuing to induce (Continuing; n=56).

RESULTS

Nil herds had a higher 8-week in-calf rate (p=0.01) than Transitional or Continuing herds (83%, 78% and 79%, respectively). The final empty rate in Nil and Transitional herds was similar (10.2% and 9.9%), tended to be greater in Nil than in Continuing herds (10.2% vs 9.0%; p=0.06) and was greater in Transitional than in Continuing herds (9.9% vs 9.0%; p=0.04), respectively. Multivariable modelling found that 8-week in-calf rates were additionally associated with year of lactation, interval from the planned start of calving (PSC) to the median calving date, duration of artificial insemination, and 21-day submission rate; and that final empty rates were associated with year of lactation, predominant breed, percentage of the herd calving within 40 days of the planned start of mating (PSM), the total duration of mating, and the 21-day submission rate, but not the herd induction policy. A change to ceasing routine use of induction tended to be associated (p=0.07) with a 2.5% increase in the final empty rate in the lactation of change.

CONCLUSIONS

The reproductive performance of herds was associated with induction policy, in addition to other factors. Herds that ceased induction had a greater 8-week in-calf rate but a greater final empty rate than those that continued. The higher empty rate in Nil herds was partly due to their shorter duration of mating.

CLINICAL RELEVANCE

Herdowners and their advisors planning to cease routine use of induction should plan for an increase in the final empty rate in both the lactation of change and in the longer term, and undertake measures to mitigate against this effect.

Induction of parturition in dairy cattle and its effects on health and subsequent lactation and reproductive performance

OBJECTIVE

To determine the effect of induction of parturition on health, milk production and reproductive performance of dairy cows.

DESIGN

A prospective cohort study in 62 dairy herds.

PROCEDURE

Health, milk production and fertility indices were documented for 1449 dairy cows treated with dexamethasone trimethylacetate, with or without prostaglandin to induce calving. Equivalent data was collected for 603 untreated herd mates that calved at approximately the same time.

RESULTS

The median interval from initial treatment to calving was 11 days. Induction was associated with a substantially lower calf survival and commercial value of surviving calves. Calf viability and value was lower when induced cows were at an earlier stage of pregnancy. Retained foetal membranes, photosensitisation and other problems were significantly more frequent in the induced group compared to the untreated group. Milk production of induced cows was approximately 4% lower than untreated ones, but the majority of reproductive indices were not significantly different between the two groups.

CONCLUSIONS

The practice of induction of parturition in seasonal calving dairy herds is a reliable way of shortening the gestation period of cows. Costs associated with morbidity and mortality of induced cows and losses in lactation and calf production are offset by benefits of improved reproductive performance and more efficient management of the herd. The welfare aspects of induction on calf survival must be considered.

Advances in bovine theriogenology in New Zealand. 2. Breeding management and technologies for improved reproduction

The importance of submission rates (SR) on conception patterns in dairy herds during a short artificial breeding (AB) programme was first reported in 1973. Subsequent research has focussed on achieving 3-week SRs of 90% through improved detection of oestrus utilising tailpainting and vasectomised bulls fitted with chin-ball harnesses. Despite nutritional limitations of spring pasture as a sole diet, conception rates to first insemination of 65% have been recorded in cycling cows in many trials. Anovulatory anoestrus (AA) has become a major factor compromising SRs as well as reducing average conception rates and herd in-calf rates by 4-7 weeks after the planned start of mating (PSM). Whole herd synchronisation programmes have been developed but not widely used on dairy cows and have had only limited use on dairy heifers, despite a focus on concentrated conception patterns. The related technologies have become most commonly used to increase the SR of AA cows. Extreme variation in the weekly demand for processed semen in seasonally-intensive AB programmes has been accommodated by the development of a unique semen diluent, Caprogen. Its use has allowed sperm to be temporarily stored without freezing and used at dose rates of 1 million sperm/insemination. Sire variation with this form of semen processing is lower than with deep frozen semen. The greater use of production genes derived from Holstein-Friesian sires of North American origin in most AB programmes has left progeny with reduced reproductive performance. This effect has been greater than that associated with the increased productivity of dairy cows achieved through continued use of semen from intensively selected groups of progeny tested sires.

Advances in bovine theriogenology in New Zealand. 1. Pregnancy, parturition and the postpartum period

Unique systems of breeding and calving management have been developed to allow New Zealand cattle herd owners to maintain seasonally concentrated calving patterns. Improved pastures are used as the sole ration for most beef and dairy cows with limited conservation and no grain feeding. Patterns of calving are described in relation to herd Planned Start of Calving (PSC) dates, calculated as 282 days after the first date of insemination in the preceding seasonal artificial breeding (AB) programme. Corticosteroids have been systematically used in over 80% of New Zealand dairy herds to induce premature parturition (calving induction) during the third trimester of pregnancy for about 25 years, to condense calving patterns into periods of 6-12 weeks. Widespread use of calving induction has minimised the adverse effects of declining reproductive performance in dairy herds on the sustainability of seasonally concentrated calving. The use of calving induction is now discouraged on animal welfare grounds and due to possible consequences for the marketing of New Zealand dairy products. Recent declines in the reproductive performance of dairy herds are linked to increased prevalence of extended periods of postpartum anovulatory anoestrus (AA), which has become the major form of infertility in dairy herds in New Zealand and can be related to reliance on grazed pasture as the sole diet for cows of increasing genetic merit. The prevalence of AA is influenced by by parity, breed, recent genetic origin within a breed, body condition score, herd and year. management strategies such as once-daily milking, preferential grazing or feeding of silage, have not proven as successful as hormonal treatments. Although seasonal concentrated calving has remained a standard feature of the industry's low-cost, pasture-based system of management, continuing research will be required to economically maintain this pattern.

Effects of periparturient diseases and conditions on the reproductive performance of New Zealand dairy cows

AIM

To determine the effect of retained foetal membranes (RFM), periparturient recumbency, calf mortality, dystocia, twin births and induction of parturition on submission and pregnancy rates of pasture-fed, seasonally-calving dairy cows in New Zealand.

METHODS

Data were retrospectively collected for 2652 cows from 11 herds on the occurrence of periparturient diseases and condition, calving date, age and treatment for anoestrus prior to the planned start of mating (PSM). The effects of each disease or condition on submission and pregnancy rate by 28 days after PSM, final pregnancy rate, and the proportion of cows that conceived more than 50 days after PSM were examined using separate logistic regression models. Results are expressed as odds ratios (OR). Additionally, the effect of each disease or condition on the interval from PSM to conception was examined using survival analysis. Age, herd and late calving (i.e. cows calved < or =40 days before PSM) were included as factors in the models examined.

RESULTS

Induction of parturition increased the risk of RFM (OR=3.3, p<0.01). The 28-day submission rate was affected by age and herd but not by any of the periparturient conditions examined. The 28-day pregnancy rate was reduced by RFM (OR=0.04, p<0.05), induction of parturition (OR=0.67, p<0.01), assisted calving (OR=0.61, p<0.01), late calving (OR=0.55, p<0.05) and anoestrus (OR=0.27, p<0.05). The final pregnancy rate was reduced by RFM (OR=0.013, p<0.01), induction (OR=0.25, p<0.05), assisted calving (OR=0.30, p<0.005) and anoestrus (OR=0.32, p<0.05), and was increased if the cow was submitted for mating within 28 days after PSM (OR=2.72, p<0.05). Effects of recumbency and twinning were not significant in any of the models.

CONCLUSIONS

Cows that had had RFM or were assisted, induced or late to calve, had significantly lower pregnancy rates or took longer to conceive than unaffected herd-mates.

CLINICAL RELEVANCE

Intervention programs aimed at the examination and treatment of cows with periparturient conditions may improve the reproductive performance of New Zealand dairy herds. Investigations of poor reproductive performance of a herd should include analysis of the prevalence and effects of periparturient diseases and conditions.