Dr. Gustavo M. Schuenemann, Professor and Extension Veterinarian, Department of Veterinary Preventive Medicine, The Ohio State University
Many dairy herds are implementing a beef-dairy crossbreeding program for all or a portion of their lactating cows in order to add value to newborn calves. In beef cattle, there is a moderate to high correlation between heritability of growth traits and their genetic correlations with birth weight (e.g., yearling body weight has a heritability of 58% and a correlation with birth weight of 0.61). Although there are several considerations such as market for beef-dairy cross calves, replacement heifers needed, and calf death losses due to dystocia and the subsequent survival and performance of lactating cows, the potential for added value by implementing a beef-dairy crossbreeding program must not neglect the potential to increase calving difficulty due to increased birth weights.
A case study using data from a beef-dairy crossbreeding program was developed to illustrate a systematic approach to assess calf death losses. The case study was developed for educational purposes; and the information may or may not be applicable to other situations. The overall objective was to assess calf death losses at calving for a 12-month period (March 2020 to March 2021). Therefore, the patterns of calf death losses were assessed on the following variables by:
- Length of dry period (primarily cows with <44 days),
- Gestation length and twin pregnancies,
- Parity (first calf heifer and multiparous cows),
- Sire (beef and Holstein bulls),
- Calendar week, and
- Calendar month.
Background: A total of 6488 calvings during March 2020 to March 2021 from one Holstein dairy herd were assessed. All cows were housed in free-stall barns and fed a TMR to meet or exceed nutritional requirements. Prepartum cows and pregnant heifers were fed an anionic diet and postpartum cows were grouped for the first 21 days in milk. First calf-heifers were grouped separately from multiparous cows in both pre- and postpartum pens. All lactating cows were milked 3x per day (every 8-hour interval) with an average annual milk yield of 96 lb/day (3.3% milk protein and 3.5% milk fat, and ~160,000 SCC/mL). The reported voluntary waiting period was 60 days for lactating cows. All lactating cows were presynched (starting at 26 ± 3 DIM) and enrolled in Ovsynch 12 days later. Cows showing signs of estrus during Ovsynch were bred and the remaining animals were subjected to timed-AI (~60% of cows were bred on heat detection and ~40% of cows on timed-AI). Multiparous cows (lactation 2 or greater) were bred with beef bulls and lactation 1 cows were bred with sex-sorted semen for the first two services (3rd or greater services with beef bulls). Breeding heifers were bred with sex-sorted semen following a simple reproductive program consisting of PGF2α every 14 days plus heat detection. Pregnant first-calf heifers were moved to the farm ~45 days prior to calving. All replacement heifers were raised on-site at a different facility. Pregnancy diagnosis was performed weekly for cows (32 to 38 days post-AI) and first-calf heifers (42 to 48 post-AI). Regarding the reproductive performance, cows had an overall 42% conception rate (CR) with 28% 21-day pregnancy rate (PR) and replacement heifers had an overall 60% CR with 42% 21-day PR. The owners and their advising team requested an assessment of the maternity (overall calf death losses) to adjust, if necessary, their beef-dairy crossbreeding program. The dairy herd was enrolled in DHIA and maternity data available on calf losses were obtained from PCDART.
Case Study Outcomes:
The overall calf death loss at the maternity was 5.4% (340 out of 6488 calvings). The pattern of calf death losses (n = 340) at calving were further analyzed to identify opportunities for improvement within the beef-dairy crossbreeding program (calving difficulty was not recorded):
1. What is the pattern of calf death losses by length of dry period?
Pregnant cows experiencing short dry period length (≤44 days) accounted for 41.1% of all calf death losses (n=140/340; Table 1). Regardless of sires, male calves had ~37% more mortality (5.9%) compared to female calves (4.3%). When looking at length of dry period, keep in mind that there is an interaction with short gestation length and twin pregnancies. Pregnant cows and first-calf heifers with twin pregnancies have shorter gestation lengths.
Table 1. Calf death losses by length of dry period.
2. What is the pattern of calf death losses by gestation length and birth of twins?
Pregnant cows experiencing short gestation length (<270 days) accounted for 15% (n = 48) of the calf death losses (Table 2). In dairy cattle, successful pregnancy results in the birth of one calf. However, the birth of two or more calves could occur at a rate of 3 to 5%. Birth of twin calves has been associated with genetics, season, parity (1.2% in primiparous and 5.8% in multiparous), breeding program (timed-AI versus estrus detection), and high milk yield. It has been shown that high milk producing cows have reduced blood progesterone due to increased metabolism to support milk yield. This reduction of blood progesterone occurs at the time of peak milk yield and breeding during the selection of the preovulatory follicle around 60 days in milk. Cycling dairy cows inseminated following estrus detection are more likely to experience double ovulation resulting in twin pregnancies (10-15%) compared to cows bred following timed-AI (3-5%). Therefore, high milk producing cows bred following estrus detection increased the likelihood of twin pregnancies, and cows with twin pregnancies have shorter gestation length. In dairy cattle, the gestation length is 276±6 days, but pregnant cows/heifers could experience a short (255-269 days), average (270-283 days), or long gestation length (284-297 days). It is known that dairy cows experiencing short or long gestation length have more calf losses at calving.
Table 2. Calf death losses by gestation length and twin pregnancies.
3. What is the pattern of calf losses by parity (first-calf heifers and multiparous cows)?
First calf heifers had less calf death losses compared to multiparous cows (Table 3). This is due to the fact that all replacement heifers and the first two services of lactation=1 cows were bred using sex-sorted semen (Holstein bulls); thus, more females calves were born. About 52% of first-calf heifers calved with ≤21 months. Multiparous cows (lactation 2 or greater) were bred using semen from beef bulls. Also, it is important to note that about 60% of all multiparous cows were bred following observation of standing heat; thus, this increases the likelihood of double ovulation, resulting in twin pregnancies regardless of sires. The overall twining rate was ~1% for first-calf heifers, ~4% for lactation 1, and ~7% for multiparous cows. When removing calves born from twin pregnancies for multiparous cows (lactation=3 or greater), the overall calf death losses was 3.1%. Calf death losses appears to be associated with twin pregnancies, gender (male) and age at calving of heifers rather than type of sires.
Table 3. Calf death losses by parity.
Footnote: Lactation 1 cows became first-calf heifers after calving (bred with sex-sorted semen). Lactation 2 cows were bred with sex-sorted semen during lactation 1 and became lactation 2 after calving.
4. What is the pattern of calf death losses by sire (beef and Holstein bulls)?
A total of 111 bulls were assessed (8 beef and 103 Holsteins). Table 4 provides information for a subset of 17 bulls (3 beef and 14 Holsteins) with ~60% of the total calf death losses. Out of 8 beef bulls assessed, 3 beef bulls (Limousine, Simmental, and Simental-Angus cross) had 24% of all calvings (11-15% twin pregnancies) with ~39% of all death losses (n = 133). Also, the data reveled an important interaction between birth of twins and calf death losses, regardless of sires (beef or Holstein bulls). Cows with twin pregnancies from beef bulls likely had to deal with an added effect of increased calf birth weight (primarily for male calves) and delivery of multiple calves. Calf birth weight is the most important predictor for difficult calving. Calf mortality due to a dystocic birth increases by 0.35% for every increased pound of birth weight above the mean for the breed. When removing calves born from twin pregnancies from the analysis for cows with lactation=3 or greater, the overall calf death losses was 3.1%. Therefore, both beef and Holstein bulls had similar overall calf death losses.
Table 4. Calf death losses by sires.
5. What has been the pattern of calf death loss at birth by calendar week?
In the calendar week, Monday had above mean calf death losses (Figure 1). Typically, Mondays are a busier workday for dairy farms because personnel are trying to catch up from any unfinished work from the previous weekend or week. This trend highlights the importance to review and adjust protocols and tasks to allow personnel sufficient time to monitor the maternity area.
Figure 1. Calf death losses by day of week.
6. What has been the pattern of calf death loss at birth by month?
Overall, summer had above mean calf death losses compared with spring, winter and fall (Figure 2). This trend is likely due to a drop in prepartum DM intake experienced by heat stressed cows with the subsequent increase in blood non-esterified fatty acids (NEFA) prior to calving. The process of calving is an active process that requires energy (glucose) and calcium to support strong uterine and abdominal contractions for the successful delivery of one or more calves.
Figure 2. Calf death losses by month.
For this case study, what are the top opportunities to reduce calf death losses?
At a minimum, the confounding effect of twin pregnancies, gender (male vs female), and parity, season and calendar week should be considered when assessing calf death losses for a beef-dairy breeding program. The overall calf death losses for this case study (5.4%) are similar to the overall for the US (5.1%). However, the top 10% dairy herds in the US, in terms of calf survival, are achieving <2% calf losses at calving. To reduce calf losses at calving, consider the following points:
- Although beef bulls had similar proportion of calf death losses as Holstein bulls, select calving ease beef sires without neglecting growth traits for beef-dairy crossbred calves. Track the degree of calving difficulty using a 4-point scale and calf birth weights for all sires, including calves born from sex-sorted semen.
- Adjust management for twin pregnancies:
- Increase the proportion of multiparous cows bred on timed-AI by reducing heat detection. This reproductive strategy allows most high milk producing cows to develop the pre-ovulatory follicle under the influence of high blood progesterone, thus increasing the likelihood of single ovulation.
- Extend the voluntary waiting period from 60 to 70 DIM to allow cows more time to recover their uterine environment and start breeding cows right after the peak milk yield when DM intake supports production and liver metabolism.
- Cows confirmed pregnant with twins should be moved into the prepartum pen with an anionic diet 10 days earlier than the rest of the cows (at 245 ± 3 days of gestation). Because cows pregnant with twins had reduced gestation length, this management strategy allows enough exposure to the anionic diet to prevent hypocalcemia.
- Review and adjust the criteria for the replacement program: a) growth and development (e.g., double calf birth weight by 60 days of life, 1.9-2 lb/day of body weight gain from weaning to calving) and b) breeding criteria (age, body weight, and height). Calf death losses increase when first calf heifers are calving with ≤22 or >28 months of age and at <1200 lb of postpartum body wight (or <80% body weight of lactation 4 cows at 100-200 days in milk).
- Train calving personnel and adjust daily tasks to allow consistent handling of the maternity workload within the calendar week.
- Adjust the heat abatement system to overcome the negative effect of heat stress during summer.
An ounce of prevention is worth a pound of cure! Please have this discussion with your veterinarian, nutritionist, and breeding team. These little details make the difference at the end of the day.