Productive and reproductive performance of crossbred and indigenous dairy cows at smallholdings in selected towns of Jimma Zone, Ethiopia

Context Evaluation of the performance of dairy cows kept in different production systems is essential for the development of appropriate breeding strategies. Aims To examine milk production and reproductive performance of crossbred (CB) and indigenous (I) dairy cows, farmers’ traits preference for CB and I breeding females, and factors affecting the performance of dairy cattle on smallholdings in selected towns of Jimma Zone, Ethiopia. Methods In total, 52 smallholder dairy cattle farmers were randomly sampled and data were collected through individual face-to-face interviews by using structured questionnaires. The traits studied were daily milk yield (DMY), lactation milk yield (LMY), lactation length (LL), age at first service (AFS), age at first calving (AFC), calving interval (CI), days open (DO), and number of service per conception (NSC), all being factors affecting performance of dairy cattle and farmers’ preferred dairy traits. Results On average, CB cows had significantly (P < 0.05) higher DMY (6.0 ± 0.33 vs 1.8 ± 0.07 L/cow), LMY (1466.7 ± 1.13 vs 376.0 ± 21.02 L (L)), LL (8.1 ± 0.41 vs 6.9 ± 0.22 months), and lower AFS (2.69 ± 0.1 vs 3.3 ± 0.07 years), AFC (3.7 ± 0.13 vs 4.3 ± 0.07 years) and CI (21.2 ± 1.37 vs 29.8 ± 1.30 months) than did I cows. However, DO and NSC were not significantly (P > 0.05) affected by genotype. In order of perceived importance, high milk yield (mean rank = 0.306), LL (0.292) and fertility (0.199) were farmers’ most preferred traits for CB breeding cows, and the corresponding preferred traits for I cows were high milk yield (0.253), adaptability (0.229) and LL (0.192). The most important factors perceived by farmers affecting the performance of dairy cattle were breed, nutrition, diseases, breeding and management practices Conclusions The findings of the study indicated that even though CB cows performed better, the performance of both breeds of dairy cows in the study area was found to be generally low due to delayed AFS, late AFC, long CI, shorter LL, low daily and LMY and high NSC. Implications The study highlighted that there is a potential for increasing the performance of dairy cows in the study area, through improved management strategies leading to shorter AFS, AFC, CI and lower NSC. Furthermore, future breed-improvement programs should take into consideration farmers’ trait preferences in design of sustainable improvement programs.

A review of oestrous behaviour and detection in dairy cows

A number of measurable physiological events characteristically occur and cause changes during the perioestrual period including the classical, diagnostic sign of standing behaviour. The onset of oestrus coincides with peak titres of oestradiol-17β that subsequently induce the preovulatory surge of LH within 1 to 3 h and ovulation of a mature follicle some 24 to 32 h after the onset of oestrus. Although detection efficiencies are consistently greater in higher producing herds, oestrus-detection efficiency generally has declined in recent years as herd size and milk production have increased. New technologies have introduced some needed assistance for detecting cows in oestrus. These include various in expensive heat mount detectors to more sophisticated electronic gadgetry, such aspedometry and radiotelemetric sensors that detect temperature, tissue impedance, and pressure. Oestrus detection aids are usually more efficient but not necessarily more accurate than visual observation. Differences in housing and environmental conditions, in addition to labor inputs, costs, and efficacies, result in variable acceptance of such technologies. Detection efficiency and accuracy can be improved by simultaneous use of synergistic technologies; those that compliment each other and monitor different indicators of oestrus. Combining technologies for simultaneous measurements of several physiological events associated specifically with the onset of oestrus and their radiotelemetrically signaling to a central computer for subsequent analysis should provide greater efficiency ofoestrus detection with fewer false positives. The ultimate goal of determining the onset of oestrus or ovulation is to predict the optimal timing for insemination. Ultimately, herd personnel must interpret information gathered by these technologies and judge whether or not and when to inseminate cows based on their visual inspection of identified cows.

Epidemiological study on factors influencing fertility indices in Israeli dairy herds

The objective of this study was to determine feeding factors connected with differences in the fertility of Israeli Kibbutz dairy herds. In an epidemiological case-control survey, data from 30, low-fertility Kibbutz dairy herds having a mean overall conception rate of 35% in multiparous cows were compared with the data from 30, high-fertility Kibbutz dairy herds having a mean overall conception rate of 48% in multiparous cows. Nutritional factors accounted for 67% of the differences between low-fertility and high-fertility herds in the overall conception rate of multiparous cows, while only 4.8% could be related to the body condition during the dry period. Among the factors which occurred more frequently in the low-fertility than in the high-fertility herds were 1) a higher average protein density and lower energy/protein ratio was fed during lactation and 2) a single feeding group was maintained for all lactating cows. 3) There were phytoestrogens in the silage or alfalfa hay, fed during lactation. 4) Faulty dry period was instituted, which was defined as the presence of at least one of the following three practices: a) the daily feed was above 3 kg of high lactation mix; b) more than 15 Mcal of net energy per day was given during the first part of the dry period; c) more than 30% of the cows were obese during the dry period. Three or more risk factors were found in one high-fertility herd and in 20 low-fertility herds. This finding emphasizes the importance of identifying and removing risk factors as a possible means for improving the reproductive performance of herds.

Estimation of genetic variation in the interval from calving to postpartum ovulation of dairy cows

Data on the interval from calving to the commencement of luteal activity of postpartum dairy cows were obtained for 1737 lactations of 1137 British Friesian cows in 11 commercial herds and 1 experimental herd between 1975 and 1982. The interval from calving to commencement of luteal activity was measured using progesterone concentrations of milk samples that were collected three or more times per week from shortly after calving to approximately 100 DIM of the following gestation. Genetic models were fitted using REML and accounting for known genetic relationships. Estimates of heritability and repeatability were 0.28 and 0.28, respectively, for the untransformed data; 0.21 and 0.26, respectively, for log-transformed data; and 0.13 and 0.26, respectively, after reciprocals were considered. In all cases, the heritability was significantly different from 0, and, of three scales, the log transformation had the greater likelihood. The likelihood of the transformation was closely related to the magnitude of the coefficient of skewness, and the power transformation with maximum likelihood was between 0.35 and 0.30, for which heritability was 0.19. The geometric mean interval was 25.6 d; coefficient of variation was 37%; and herds, years, parity, and season all had significant effects upon the interval to commencement of luteal activity. The postpartum interval grew longer by 2.2% with each parity [confidence interval 95% (1.1%, 3.0%)] and showed seasonal variation. Cows calving during spring took 1.21 times longer to commencement of luteal activity than did cows calving during autumn [95% confidence interval (1.13, 1.29)]. Genetic regression on PTA of the sire for milk, fat, and protein yields and for fat and protein percentages and on a national economic index were carried out using a subset of animals during 721 lactations. The regression was positive for fat percentage, but not significantly different from 0 for others. The magnitude of the heritability estimate in this study indicates that the postpartum interval to commencement of luteal activity may be useful for selecting cattle for improved fertility because shorter intervals have been postulated to be correlated with higher reproductive efficiency.

Effects of dietary crude protein, breed, parity, and health status on the fertility of dairy cows

A study was conducted to determine the impact of dietary CP (13% vs. 20%), parity (first vs. second lactation or later), and breed (Holstein vs. Jersey) on the reproductive efficiency of dairy cows. Sixty-four cows were blocked by parity and breed and assigned to one of two treatments. Cows were removed from treatments on d 100 or 120 depending on pregnancy status. Cows were categorized by health status based on the occurrence of postparturient disorders. Plasma urea N concentrations were influenced by diet (8.6 vs. 21 mg/dl, 13 and 20% CP, respectively), parity, and breed. Reproductive indices were not influenced by diet except that days to first estimated ovulation increased for cows fed the 20% CP diet when health status was added to the model. Days to first observed estrus, first AI service, and cumulative pregnancy rate were affected by health status. Regression analysis for survival showed an interaction of diet and health status for days open. High CP diets tended to increase days open when cows had major health problems; otherwise, a high CP diet decreased days open. The implementation of a strict reproductive management program allowed high reproductive efficiency goals to be achieved regardless of plasma urea N concentrations.

Induction of estrus after thyroidectomy in nonlactating Holstein cows

Hypothyroidism reportedly decreased sexual behavior in several species. To confirm the role of hypothyroidism in the expression of estrus in cattle, our objective was to determine whether estrus could be induced in ovariectomized cows without intact thyroid glands using estradiol benzoate and progesterone. Eight nonlactating, nonpregnant Holstein cows were thyroidectomized and ovariectomized, and another four cows were ovariectomized only. All cows were given either estradiol benzoate in a crossover design with two replicates during 4 consecutive wk. Cows were observed continuously for estrus from 9 to 45 h after treatment with gonadal steroids. Intensity of estrus was assessed by quantitative measurement of the frequencies of mounting activity and standing behavior. The percentage of cows showing estrus was influenced by thyroidectomy-ovariectomy (78.1%) compared with ovariectomy (31.1%) but was unaffected by hormonal treatment. In contrast, other measures of estrous behavior (duration of standing estrus and frequencies of mounting and standing activities) were unaffected by thyroid status or by hormonal treatments. We concluded that ovariectomized cows without intact thyroid glands exhibit estrus and that the exhibited behavior is similar in intensity and duration to that in ovariectomized cows treated with gonadal steroids. Hypothyroidism may not cause failure to express estrus.

Dose titration of sustained-release recombinant bovine somatotropin in lactating dairy cows

Lactating dairy cows (n = 264) were used in seven dose titration experiments at four geographic locations in the United States. A sustained-release formulation of recombinant bST was evaluated for a 30-wk treatment period that began 14 wk postpartum. The first series of four experiments evaluated doses of 0, 140, 350, or 700 mg of bST/14 d (series A); the second series evaluated doses of 0, 56, 140, or 350 mg of bST/14 d (series B). Milk yield, DMI, milk composition, body condition, health, and reproductive parameters were measured. Multiparous cows in series A that were administered 700 mg of bST/14 d yielded 3.0 kg/d more milk and 3.5% FCM than control cows. When all seven experiments were combined, multiparous cows that were administered 350 mg of bST/14 d yielded 2.7 and 2.6 kg/d more milk and 3.5% FCM than control cows. Dry matter intake was not significantly affected by bST administration. In series A, an increase in milk yield with no increase in DMI resulted in lower adequacy of dietary NEL and CP to meet maintenance and yield requirements among multiparous cows administered 700 mg of bST/14 d. Primiparous cows that were administered bST in series A and both parity groups in the combined seven experiments were not different from control cows in the adequacy of dietary NEL or CP to meet maintenance and yield requirements. No adverse effects of bST on health parameters were significant, and doses of 350 mg of bST/14 d or less caused no changes in reproductive parameters. Conception rate was decreased by administration of 700 mg of bST/14 d. These data suggest that 350 mg of bST/14 d increased yields of milk and FCM with no adverse effects on DMI, health, or reproduction in dairy cows.

Factors affecting days open, gestation length, and calving interval in Florida dairy cattle

Effects of several factors on reproductive performance were evaluated. Mean performance and number of observations were for days from parturition to first service, 93 and 7730; days from first to successful service, 35 and 11,751; days open, 123 and 8571; gestation length, 280 and 13,612; and calving interval, 400 and 8524. Data covered 52 yr during which no detectable trends in calving interval occurred; other variables changed slightly. Jerseys had 8 fewer d from parturition to first service, 16 fewer d from first service to conception, 8 fewer d open, and 8-d shorter calving intervals than did Guernseys and Holsteins, which did not differ. Cows freshening in warm rather than cool weather suffered by 7, 7, 12, and 13 d for these variables. Repeatabilities ranged from .05 to .12; heritabilities were .05 and .06. Nonmaternal estimate of heritability of gestation length was .22. Phenotypic and genetic correlations between days from parturition to first service and calving interval were .48 and .87; for days open and calving interval, they were .97 and .96. Although days from first to successful service were essentially uncorrelated with days open and calving interval phenotypically (.05), genetic correlations were greater than 1.0 and estimated as unity. Results show no discrepancy between estimates for measures of reproductive performance in a subtropical environment and numerous studies in temperate areas. Large studies from subtropical areas are sparse; essentially none concerns long-term trends.

Factors affecting calving interval in Italian Holstein-Friesian heifers

Effect of rump conformation on calving interval of 520 Italian Holstein Friesian heifers was evaluated with simultaneous adjustment for herd, year of birth, calving month, age at first parturition, and milk production. All factors, except age at first parturition, were important sources of variation. Heifers with narrow rumps at the pins had the longest calving interval. There were significant differences among the herds. Cows born between 1979 and 1981 had shorter calving intervals, probably resulting from a national plan against bovine infertility initiated in 1981. Cows calving in July had better reproductive performance. There was positive relationship between milk production and calving interval.

Reproductive disorders in the periparturient dairy cow

Incidence, predisposing factors, and implications of various reproductive disorders (dystocia, twinning, stillbirth, retained placenta, cystic ovaries, anovulation, infections of the reproductive tract, metritis, and abnormal health status) are reviewed as to their inter-relationships and collective impact on reproductive performance, milk yield and predisposition to other diseases or disorders in the periparturient dairy cow. All reproductive disorders reviewed reviewed reduce reproductive performance either directly or indirectly. Concurrent milk yield was reduced marginally in a few studies as a consequence of twinning, retained placenta, cystic ovaries, metritis, or other uterine disorders, and in cows with an abnormal health status. There is strong evidence for associated losses in milk yield following surgical delivery of a stillborn calf. We conclude that most periparturient disorders occur as a complex, rather than as a single abnormality. Cows with one disorders are at increased risk for other disorders, including metabolic ones. In contrast, actual milk yield or potential for high production generally does not predispose cows to increased risk for any of the reproductive disorders. The literature suggests that prophylactic measures to prevent occurrence of the one disorder might decrease the risk and incidence of other related disorders, either directly or indirectly.