6. Production traits in twin- and single-calving cows after calving

A study of the same dairy farm in northern Hungary [40] compared the total lactation performance data of 10,666 cows, in detail, examining the most economically important traits such as milk yield (kg), fat yield (kg), and protein yield (kg) and taking into account factors such as whether the cow had a single or twin calving, the proportion of Holstein Friesian genetics, the season the calving occurred in, the number of lactations, and the year of calving. The average total milk yield produced was 7140 kg, a noticeable difference was seen in comparison of single-calving and twin-calving cows in favor of single-calving cows (p = 0.013). On average, single-calving cows were found to produce 7390 kg of milk, whereas the twin-calving cows were found to produce 6890 kg. In terms of the type of calving, it was shown that cows that had twins yield on average 500 kg less milk than single-calving cows. As mentioned above, not only was total lactation yield (kg) evaluated but also fat yield (kg) and protein yield (kg) were evaluated. Regarding the fat yield, a meaningful distinction was recognized between single-calving cows and twin-calving cows (p = 0.030); single-calving cows gave 17 kg more fat.

The overall standard lactation milk yield is 6685 kg. When the milk yield (p = 0.002), the fat yield (p = 0.001), and the protein yield (p = 0.004) were examined, they were found to have significant differences based on the type of calving. Twin-calving cows produced on average 410 kg less milk than single-calving cows.

However, contradicting results were found in another study [30]. Examining a herd of 23,588 cows of a local breed improved with Holstein Friesian between the years 2000 and 2008, it was found that the average milk yield in kg after calving was found to be 6219 for single-calving cows, 6434 for twin-calving cows, and 7097 for cows calving triplets.

to be increasing over time. Cows having twins are at greater risk for many periparturient reproductive and metabolic disorders than cows having single calves. Abortion, stillbirth, neonatal calf mortality, and reduced birth weights are seen more with the birth of twins than

Twin Calving and Its Connection to Other Economically Important Traits in Dairy Cattle

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It was found in a study [27] that the average length of gestation before calving on the studied farm was 276.3 days. Here we experienced significant (p < 0.001) difference of approximately 5 days by type of calving. Twin-calving cows' gestation length (274 days) has proven to be shorter than that of nontwinning (278.7 days) herdmates. As their gestation is shorter and their reproductive performances are better, with shorter regeneration time and higher conception rates, they have a short calving interval. However, the benefits of this shortened calving interval before twinning are negated by the reproductive problems following twinning. There

are more factors influencing the profitability of dairy cows than calving interval alone.

Dystocia means a difficult or abnormal delivery that occurs more frequently with twin births than with single births. In any calving, dystocia can be due to fetopelvic disproportion, an oversized calf or a dam with incomplete development or incomplete cervical dilation or due to abnormal presentation of the calf. However, twin calvings have the added complication of both calves entering the birth canal at the same time. These are usually dealt with by some sort

Multiple births can cause difficulties at parturition, if parts of more than one fetus enter the birth canal at the same time [42–48]. These abnormalities can occur when two of the fetuses are

The symptoms of dystocia are highly variable, since each of the fetuses may be presenting in the anterior or posterior positions with variable positioning of the head and legs [50]. Therefore, these presentation anomalies occur more regularly in twin births than in single

The occurrence of posterior presentation in twin birth is approximately four times higher (10.7%) than in single births (2.5%) [54]. Abnormal presentation was the cause of dystocia in 15.3% of the singletons and 77.8% of the twins. However, this can be easily corrected in twins due to their relatively low body weight, but nevertheless these factors still can result in stillbirths when there is a lack of observation during parturition. Obstetrical intervention was

Some studies in the USA have demonstrated that the incidence of calving difficulty has decreased within the last number of years [26], whereas conflicting studies have shown the opposite, that it has not changed [55]. In this period of time, a gradual increase of twinning and

An analysis of the relationship between multiple births and dystocia [56] data was drawn from the SYMLEK database and provided information on 148,385 calvings of Polish Black-and-White

released from the uterine horns at the same time and meet in front of the pelvis [49].

implemented in 42.2% of twin births and 20.4% of single births [28].

periparturient mortality was detected [26, 55].

with that of single calves [30].

7.2. Dystocia and perinatal mortality

births [28, 42, 43, 45, 46, 51–53].

7.1. Gestation length

of intervention.

In a study performed in the USA [41], the effects of twin calving on the lactation in Holsteins were studied from a compilation of calving records from the Eastern Artificial Insemination Cooperative. The records of cows were grouped according to whether or not the twin calving was associated with dystocia. Records of each twin-calving cow were paired with records of a singlecalving control herdmate. In the twin group of 175 cows that had difficult calvings, twin pregnancy was not found to have an effect on the cows' production; milk and fat yield in the lactation initiated by twinning were depressed; however, this was not significant. In the group of 367 twincalving cows with no dystocia at calving, milk and fat production were depressed by 285 and 14 kg in the lactation after the calving. It was shown that twinning associated with dystocia seemed to depress the milk yield in the subsequent lactation (year 2). Compared to controls, twin-calving cows outperformed their herdmates in both the lactation before the twin calving (year 1) and the lactation after the next successful calving (year 3). Separate analysis of the 172 individuals with milk records for years 1 and 2 gave mean yields for year 1 of 7848 kg for twincalving cows and 7722 kg for the control cows. For year 2, the mean for twin-calving cows was 7794 kg compared to a mean of 7811 kg for control cows. Although these means also indicate a depressive effect of twinning, this interaction was not considered significant. Mean values for cows where twinning was not associated with dystocia showed that twinning also depressed subsequent milk yield. The twin calvers outperformed their herdmates in years 1 and 3. No depression was noted for milk yield in the twin pregnancy lactation (year 1). There was also significant depression in fat percentage with twinning combined with a depression in milk yield to depress fat yield. In a group of 305 pairs in which no dystocia with twinning was observed, fat yield also was depressed in the twin pregnancy lactation. Twin calvers outproduced their herdmates in year 3, the year not directly affected by a twin calving. Both groups showed roughly the same effect of twinning on the number of open days following a twinning (Table 2). The 100 twin calvers associated with dystocia showed a noticeable increase in the number of open days following twinning. The 157 twin-calving cows with records for years 2 and 3 were open for an average of 105 days prior to conception of twins and 132 days after birth of twins as compared to means for the controls of 101 and 106 days. Analysis of the conception rate of 212 pairs of cows in which twin calvers had no difficulty calving showed that conceptions with twins averaged 9 days earlier when compared to conceptions of single-calving herdmate controls. After the twin birth, twin calvers took 22 days longer to conceive than their herdmates. When 316 pairs were examined for years 2 and 3 only, twin calvers showed a mean number of days open prior to conception of twins of 100 days and a mean of 131 days to conception following the twinning as compared to means of the controls of 105 and 108 days.
