Productivity of different cow genotypes: culling rates and early calf performance

Records of Jersey-sired (Jx), Santa Gertrudis-sired (Sx), Charolais-sired (Cx) and straightbred Hereford (H) cows were examined to determine culling rates, birth dates, weaning weights and average daily gains of their first, second and third calves. Culling categories were defined on the basis of number of calves weaned before removal from the herd. Calf performance data were analyzed by cow breed group and cow culling category. A second-degree polynomial model fit the data of all breeds, and accounted for a greater proportion of variation in percentage culled than did the linear model (P less than .05). Total percentage culled through the study were 71, 67, 54 and 53 for the H, Sx, Cx and Jx cows, respectively. Culling rates in the H and Sx cows tended to be higher at earlier ages than in the Cx and Jx cows. Cow-culling category was a significant source of variation only on birth date of first calves. Cows culled after one calf had calves that were born later than cows in the other two categories (P less than .05). Birth date, weaning weight and average daily gain of first calves varied with cow breed in that Jx cows had calves that were born earlier, gained faster and weaned heavier than first calves from the other breed groups (P less than .05). First calves from Sx and Cx cows gained faster (P less than .05) than calves from H cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of grazing on cow mortality in Danish dairy herds

The effect of summer grazing in large Danish dairy herds and certain management characteristics of grazing were studied for their impact on dairy cow mortality. Mortality data (from the Danish Cattle Database) from 391 Danish dairy herds (>100 cows) were combined with information from a questionnaire survey of grazing procedures on these herds in 2008. In all, 131 of the herds were identified as summer grazing and 260 as zero-grazing herds. The mortality was affected by an interaction of summer grazing and milking system. The risk of a cow dying was reduced to 46% in a grazing compared to a zero-grazing herd having automatic milking system. In traditional milking system, mortality was reduced to 75% in grazing compared to zero-grazing herds. Within the grazing herds, the risk of mortality decreased with increasing number of hours on pasture during the season. Free access between barn and pasture was associated with increased cow mortality.     

Discrete time survival analysis of lamb mortality in a terminal sire composite population

Mortality records of 8,642 lambs from a composite population at the U.S. Meat Animal Research Center during the first year of life were studied using discrete survival analyses. Lamb mortality was studied across periods from birth to weaning, birth to 365 d of age, and weaning to 365 d of age. Animal-time data sets were created for each period using different time intervals: daily, weekly, fortnightly, and monthly. Each data set was analyzed using logistic and complementary log-log sire, animal, and maternal effects models. Explanatory variables included in the models were duration of time interval, sex, type of birth, contemporary group, age of dam, and type of upbringing (nursery or not). Similar estimates of explanatory variables were obtained within the same period across models and different time intervals. Heritability estimates from the complementary log-log models were greater than those from the comparable logistic models because of the difference in variance of the respective link functions. Heritability estimates from the complementary log-log sire model ranged from 0.13 to 0.21 for all periods. These estimates were greater than the complementary log-log animal model estimates that ranged from 0.04 to 0.12. Maternal effects were important early in life, with the maternal heritability slightly greater than the direct additive heritability. Negative correlations (-0.72 to -0.65) between direct additive and maternal effects was estimated. The similarity of results among survival analysis methods demonstrates that the discrete methodology is a viable alternative to estimate variance components in livestock survival data.     

Associations between health disorders of French dairy cows and early and late culling within the lactation

Data from an observational study, carried out during a 4.5 year period (1986–1990), were used to quantify the effects of health disorders on the risk of culling. The study population consisted of 47 commercial Holstein dairy herds from western France, comprising 4123 cows.

Logistic regression was used to assess the relationships between health disorders and early and late culling. Fourteen main health disorders with clinical signs and one subclinical disease were studied: abortion, periparturient accident, calving provided with assistance, digestive disorders, ketosis, locomotor disorders, mastitis, metritis, milk fever, cystic ovaries, respiratory disorders, retained placenta, teat injuries, non-traumatic udder disorders and status with respect to milk somatic cell count. Adjustments were made for year, month of calving, parity, breeding value for milk, best of the two first milk production records and reproductive performance. The possible effects of interactions among variables were also studied. The herd effect was taken into account using random effect models.

Non-traumatic udder disorders, teat injuries, milk fever and the occurrence of both ketosis and assistance at calving were significantly associated with an increased risk of being early culled (odds ratios (OR) ranging from 1.6 to 10.3). Early and late abortion, late metritis, poor peproductive performance, retained placenta, non-traumatic udder disorders within 45 days post-partum and mastitis occurring in the first 3 months of the lactation were positively associated with a late culling (OR ranging from 1.2 to 6.6). Cows with lower breeding value for milk and higher parities were high risk groups for culling. A lower level of milk production and occurrence of both reproductive disorders and poor reproductive performance were risk factors for late culling.     

Causes of mortality and culling in adult pheasants

The causes of the deaths or culling of 155 adult pheasants in breeding pens on one site between 1995 and 1997 were investigated. Approximately half the deaths were the result of problems associated with the reproductive tract or trauma, including injuries acquired during fighting or mating. Sinusitis was the commonest infectious cause of mortality or culling, despite medication of the flocks for mycoplasmosis. Marble spleen disease and pheasant coronavirus-associated nephritis, two viral conditions capable of causing high mortality, were diagnosed in a few birds in 1996 and 1997. Histomoniasis (blackhead) contributed to the mortality in 1996. A lymphomatous condition of uncertain aetiology was detected in a small number of birds.     

泌乳初期奶牛乳成分与血液生化指标相关性研究

通过分析泌乳初期健康、酮病和低钙血症奶牛血液生化指标及乳成分,明确相关疾病的乳成分特征,同时对泌乳初期奶牛血液生化指标与乳成分相关性进行分析,以期为牛群健康评价提供方法支持。根据血液指标选取产后7~21d荷斯坦奶牛72头,分为亚临床低钙血症试验组、酮病试验组和健康对照组,每组各24头。采集试验奶牛的血液和乳汁用于血液生化指标与乳成分相关性分析。结果显示,酮病和低钙血症引起乳蛋白和非脂乳固体水平降低,而乳中柠檬酸的含量增加。奶牛乳中柠檬酸与血清NEFA、BHBA和GLU相关性方程分别为:y=3.192x-0.802,R~2=0.363;y=4.594x-0.793,R~2=0.320;y=1.228x+0.775,R~2=0.261;其中方程中x为乳中柠檬酸的含量。结果表明,乳中柠檬酸的含量与血液NEFA呈显著正相关,可用于能量负平衡的早期诊断标示物。血中BUN及ALB的水平可用于评价乳蛋白和尿素的水平。     

Analysis of early survival of Holstein-Friesian heifers of diverse sire origins on commercial dairy farms in Kenya

The use of imported semen within the Holstein-Friesian cattle population in Kenya has contributed to increased milk production per cow, however, information on how this has impacted on functional traits, particularly early life survival and reproductive performance is scarce. This study evaluated age at first calving (AFC), survival to age at first calving, and survival to four years of age using survival analyses techniques, in Holstein-Friesian cattle on four dairy farms in Kenya. The heritability estimate obtained for AFC was 0.15 ± 0.06 for an average AFC of 1058 days. Animals sired by New Zealand and Australian born bulls had the earliest average AFC (907 days). On average, 25% of all the heifers born were culled prior to attaining a first calving, while 34% were culled prior to four years of age. Though the highest proportion of losses was due to unspecified reasons, the relative risk of being culled was highest when an animal had a specific disease, and the first 60 days of life were the most critical for survival. Daughters of sires from South-Africa and Israel tended to have better survival rates than those sired by bulls originating from other regions. Unfavourable selection towards animals sired by Kenyan born bulls was evident. The economic implications of the high rate of early mortality need to be evaluated in order to assist livestock producers make informed decisions on choice of sires for breeding.     

Theoretical aspects of culling and selection in dairy cattle

A theoretical analysis is made of the optimal culling or selection policy among cows to maximize mean yield in herds which do not breed bulls, but use those nationally available by A.I. For simplicity the analysis deals mostly with an idealized case where voluntary culling on yield is carried out only on the basis of first lactation yield. A formula is developed for computing the optimal culling rate, which is a function of the expected difference in yield between first and later lactations and of the repeatability of yield.The present mean yield of the herd is little affected by culling. At the optimum of about 70% of cows retained, the increment in yield is around 1%, so it is likely to be more economic to bring fewer heifers into the herd and practise a minimum of culling. If a substantial genetic trend is incorporated and yield is to be maximized in later generations, the benefits of culling are greater and fewer animals should be retained after first lactation. The greatest benefits from culling are obtained if it is practised in mid-lactation.     

蒸汽压片玉米、烟酸和蛋氨酸锌对泌乳早期奶牛产奶量及乳成分的影响

本研究选择泌乳早期的经产奶牛40头随机分成4组,其中一组作为对照组,各试验组奶牛日粮中分别添加蒸汽压片玉米(蒸汽压片组)、烟酸和蛋氨酸锌(添加剂组)、蒸汽压片玉米+烟酸和蛋氨酸锌(蒸汽压片+添加剂组)。观测其对泌乳早期奶牛产奶量及乳成分的影响。结果表明:饲喂蒸汽压片+添加剂组和蒸汽压片组的奶牛乳蛋白率和乳糖率显著高于对照组(P0.05);添加剂组奶牛乳蛋白率显著高于对照组(P0.05);各试验组的产奶量、4%FCM、乳脂率和非脂固形物都比对照组有所提高,但无显著差异(P0.05);试验组乳中体细胞数有降低的趋势,但差异不显著(P0.05)。试验结果提示,蒸汽压片玉米、烟酸及蛋氨酸锌具有提高泌乳早期奶牛的产奶量和改善乳品质的作用;各组日粮对奶牛产奶量和乳成分的影响大小为蒸汽压片+添加剂组蒸汽压片组添加剂组对照组,奶牛日粮中混合添加蒸汽压片玉米、烟酸及蛋氨酸锌效果优于分别添加蒸汽压片玉米和添加剂。     

喀斯特地区奶牛小区泌乳盛期能量需要量研究

选用处于泌乳盛期中国荷斯坦奶牛12头,采用随机分组设计,根据产奶量、胎次、泌乳期、体重等因素,将试验牛分为试验1组(对照组,采用当地惯用日粮饲喂)、2组和3组。其中试验2组和3组进行2×2因子交叉饲养试验。试验牛的日粮由苜蓿、野草、稻草和精料组成,其中一组能量的供给量按饲养标准的推荐量供给,另一组的供给量是饲养标准推荐量的120%。饲养试验共进行2期,每期正式期15d,预试期7d。通过试验得到喀斯特地区奶牛小区饲养能量、蛋白质与钙、磷供应平衡模式:NER盛期(KJ)=1.2097(356W0.75×k) M×(0.4 15×Fat)×3138 △W×6.56×3138。     

The effect of feeding grass silage in early pregnancy on claw health during first lactation

Two groups of eight Holstein-Friesian heifers were fed either a grass-silage-based diet (S) or one based on meadow hay supplemented with 1.8 kg/day barley concentrate mix (H) during cubicle housing as young stock (and in early pregnancy). Lameness and claw lesion development were monitored from approximately four weeks before until 20 weeks after first calving. No significant difference was found between S and H for claw conformation or horn growth and wear. Both groups showed net wear immediately after calving. The prevalence of poor locomotion and the extent of lesion development 20 weeks after calving (when they were highest) were significantly (P< 0.05) higher in S than H. It was concluded that feeding grass silage to young stock may deleteriously affect subsequent claw health and that this risk factor requires further study.     

Effect of using an internal teat sealant at drying-off in cows wintered on forage crops in New Zealand on culling in the dry period and early lactation

AIMS: To determine the impact of treatment with internal teat sealant (ITS) compared to no treatment at drying-off on culling during the dry period and 90 days after calving, for cows wintered on forage crops.

METHODS: In four dairy herds in the South Island of New Zealand, cows with no history of clinical mastitis or somatic cell counts >100,000 cells/mL during the 2015–16 season were randomly assigned to treatment with ITS in each quarter (ITS group) or no treatment (Control group). Cows were otherwise treated similarly, wintered on forage crops and transferred to pasture for calving and lactation. Culling was defined as an unplanned exit from the herd, including cows sold for slaughter, cows slaughtered for salvage value and cows that died on farm. Culls and cull dates were recorded between drying-off and 90 days after calving.

RESULTS: Between drying-off and 90 days after calving 24/491 (4.9%) cows in the ITS group and 45/473 (9.5%) cows in the Control group were culled (RR=0.51; 95% CI=0.75–0.83), and between 30 days before calving and 90 days after calving 20/491 (4.1%) cows in the ITS group and 40/473 (8.5%) cows in the Control group were culled (RR=0.48; 95% CI=0.29–0.81). In the final multivariable logistic regression model, adjusting for dry-period length, cow age, breed and farm, the OR for culling in the study period was 0.43 (95% CI=0.23–0.81) for cows in the ITS compared with the Control group. For a Friesian/Jersey cow, aged 4–8 years, with a dry period of 30–80 days, dried-off without ITS, the probability of culling in the study period was 0.10 (95% CI=0.06–0.16), and for such a cow treated with ITS the probability was 0.05 (95% CI=0.03–0.08).

CONCLUSIONS AND CLINICAL RELEVANCE: In these four herds, the use of ITS at drying-off reduced the incidence of culling between drying-off and 90 days after calving. The use of ITS at drying-off in cows prior to wintering on forage crops may provide additional benefit to farmers through reduced incidence of culling and should be considered in any cost–benefit analysis of its use.     

超数排卵与采卵对供体牛产奶量及繁殖性能影响的试验研究

超数排卵和胚胎移植技术是良种奶牛快速扩繁的最佳手段和途径,但有人担心超数排卵、采卵等不良刺激会对供体牛的产奶量和繁殖性能产生不良影响。2003～2004年对90头供体牛超数排卵和采卵后的产奶量和繁殖情况进行记录,并与未经超排的成乳牛和育成牛进行比较,发现超数排卵与采卵对供体牛的产奶量和繁殖性能均无显著影响。     

Effects of feeding fatty acid calcium and the interaction of forage quality on production performance and biochemical indexes in early lactation cow

Multiparous early lactation Holstein cows (n = 16) were used in a randomized complete block design to determine the effects of feeding fatty acid calcium and the interaction of forage quality on production performance and biochemical indexes in early lactation cow. Treatments were as follows: (i) feeding low‐quality forage without supplying fatty acid calcium (Diet A), (ii) feeding low‐quality forage with supplying 400 g fatty acid calcium (Diet B), (iii) feeding high‐quality forage without supplying fatty acid calcium (Diet C) and (iv) feeding high‐quality forage with supplying 400 g fatty acid calcium. This experiment consisted 30 days. The milk and blood samples were collected in the last day of the trail. Intakes were recorded in the last 2 days of the trail. Supplementation of fatty acid calcium decreased significantly dry matter intake (DMI) (p < 0.01). Addition fatty acid calcium decreased milk protein percentage (p < 0.01) and milk SNF percentage (p < 0.01), but increased MUN (p < 0.05). Supplemented fatty acid decreased concentration of blood BHBA (p < 0.05), but increased TG, NEFA, glucagon, GLP‐1, CCK, leptin, ApoA‐IV, serotonin and MSH concentration in blood, the CCK concentration and feed intake showed a significant negative correlation (p < 0.05).     

The effect of age on erythrocyte magnesium concentrations of dairy cows during late pregnancy and early lactation

Blood samples were taken at weekly intervals from fifty four dairy cows (mainly Friesians and Jerseys) during the periods 8 weeks before and 8 weeks after calving. The cows were divided into two age groups; Group 1 consisting of 26 cows 2 1/2 to 4 years old and Group 2 consisting of 28 cows over 4 years old.The changes in erythrocyte magnesium (EMg) and plasma magnesium (PMg) concentrations before and after calving were expressed as the slope of each blood parameter regressed on weeks. The post-partum EMg concentration slope (increase) was greater (P<0.05) in the older cows than in the young ones. The older cows also had higher (P<0.05) mean EMg concentrations than the young cows. Between cow EMg concentration variations were significant (P<0.05) in both age groups while the weekly EMg concentration variations were only significant (P<0.05) in the older cows after calving. Age did not influence the changes in PMg concentrations before or after calving. Nor did the PMg concentrations vary significantly either between cows or between weeks.     

Post-grazing sward height imposed during the first 10 weeks of lactation: Influence on early and total lactation dairy cow production,and spring and annual sward characteristics

Increasing the proportion of grazed grass in the diet of the dairy cow is the main target of grass-based milk production systems. Imposing a severe post-grazing sward height (PGSH) in early lactation is one strategy to increase grass utilisation. A grazing experiment was undertaken to investigate the direct and carryover effects of PGSH imposed in early lactation on sward and dairy cow lactation performance. Ninety Holstein–Friesian dairy cows (mean calving date: February 13) were randomly assigned to one of three target PGSH treatments: 2.7 cm (severe; S), 3.5 cm (low; L) and 4.2 cm (moderate; M) from February 14 to April 24, 2011 (period 1; P1). This was followed by a carryover period (period 2; P2) during which cows were randomly re-assigned within their P1 treatment across two PGSH treatments: 3.5 or 4.5 cm until November 13. Sward utilisation (>2.7 cm) during P1 was significantly improved by decreasing PGSH from M (0.74) to L (0.82) and further to S (0.94). At the end of the entire grazing season, the M treatment swards had produced +1.4 t dry matter (DM)/ha than the S and L treatment swards which had similar total DM yields (14.1 t DM/ha). Treatment had no immediate or carryover effect on the proportions of leaf, stem and senescent material in the sward or the quality of herbage selected by the animals. During P1 the cows in S had greater bodyweight loss (−18 kg), reduced milk (−2.1 kg/day) and milk solids yields (−0.21 kg/day) as well as lower grass DM intake (−1.7 kg DM/day) compared with the cows in L and M, which performed similarly (−5 kg, 24.1 kg/day, 1.94 kg/day, and 13.0 kg DM/day, respectively). There was no carryover effect of early lactation PGSH on milk and milk solids yields, fat and protein concentrations during P2. This indicates that cows restricted in P1 were able to adjust production in accordance with the higher PGSH imposed during the remainder of the lactation. The S treatment had numerically lower, though not significantly lower, total lactation milk and milk solids yields, reflecting their significantly reduced yields in early lactation. It was concluded that grazing to 2.7 cm in early lactation is too restrictive for dairy cows. Cows in L and M had very similar total cumulative production performance. As a result, grazing to 3.5 cm during the first 10 weeks of lactation contributes to achieving both high milk output from pasture and high grass utilisation.     

三段冷却方式对淘汰奶牛背最长肌宰后生化变化和嫩度的影响

分别取淘汰奶牛的左侧背最长肌,在2℃冷却24h作为对照组;右侧背最长肌在2℃冷却3h,15℃冷却6h,然后在2℃冷却15h(三段冷却方式),作为处理组。测定结果显示,对照组的肌肉中心温度宰后10h时已降至4.1℃,处理组肌肉中心温度在宰后3⁹h维持在(16±0.5)℃范围内,到宰后13.5h降到4℃。处理组宰后8和24h的肌糖原含量显著低于对照组,宰后8h处理组的pH值显著低于对照组。这一结果表明,宰后4h开始处理组的肌糖原分解速度快于对照组,从而加快宰后处理组pH值的降低速度。处理组宰后8,24,48h的肌节长度显著大于对照组,宰后1和3d的剪切力值显著低于对照组。这一结果提示,淘汰奶牛宰后在2℃持续冷却,可能导致背最长肌的严重冷收缩,从而对嫩度产生负面影响,三段冷却方式可以改善淘汰奶牛宰后嫩度品质。