Production and related variables in bovine leukaemia virus-infected cows

A newly developed milk dot blot test was used to detect anti-bovine leukaemia virus (BLV) antibody in milk samples from 2079 lactating adult cows from among 61 herds. The milk dot blot test was highly repeatable; the concordance rate, compared with the agar gel immunodiffusion test performed on serum, was 83.5%. All herds contained BLV-positive cows; the prevalence rate was 36%. BLV-positive cows tended to come from larger herds and were older and more often later in lactation. Fourteen production and related variables (herd size, age, days open, days in milk, milk somatic cell count, milk, fat, and protein produced in the current lactation, projected production of milk, fat, and protein, and breed class average deviations for milk, fat, and protein) were compared between BLV-positive and BLV-negative cows. Although somatic cell count, milk produced, and projected production of milk and protein were related significantly to BLV status using simple tests of association, once the variables herd size, age and days in milk were controlled, these differences were removed. Further analyses using logistic (outcome: individual cow BLV status) and least-squares regression (outcome:herd proportion of BLV-positive cows) failed to show an association between any of the measured production or related variables and BLV-positivity. We concluded that the effect of BLV on production and related variables in dairy cows was below the sensitivity of our analytical techniques or was non-existent.Abbreviations ABCA herd average breed class average for milk, fat, and protein production - AVGAGE average age of the herd - ADIM herd average for days in milk - AGID agar gel immunodiffusion - AVGSCC herd average milk somatic cell count - BCA breed class average, a milk, fat and protein production index calculated by comparing a cow's actual 305-day lactation production to the corresponding BCA standard for the same breed, age, and month of calving - BLV bovine leukaemia virus - CALVINT calving interval - COWAGE cow age - DBCA breed class average deviation for milk, fat, and protein production, the difference between an individual cow's BCA and the herd average - DIM days in milk - HS herd size corresponding to the number of lactating cows in a herd - LACT actual amount of milk, fat, and protein produced in a cow's lactation - ODHIC Ontario Dairy Herd Improvement Corporation - PCTPOS percentage of herd that is BLV-positive - PROJ projected 305-day production for milk, fat, and protein by fitting to a standard lactation curve adjusted for days in milk and age at calving - RHBCA rolling herd average for breed class average for milk, fat, and protein production, the average for all cows that completed a lactation (cows must have completed a 305-day lactation) during the previous 12 months - SCC milk somatic cell count     

Genetic aspects of productive and reproductive traits in a Murrah buffalo herd in São Paulo,Brazil

This study investigated genetic trends of some productive and reproductive traits in a herd of Murrah buffalo raised in São Paulo, Brazil. Variance components for milk production (MP), length of lactation (LL), calving interval (CI) and age of first calving (AFC) were estimated by the restricted maximum likelihood method, using an animal model. Estimated heritability values were 0.38; 0.01; 0.10 and 0.20 for MP, LL, CI and AFC, respectively. Estimated repeatability values were 0.50, 0.13 and 0.20 for MP, LL and CI, respectively. Means of predicted breeding values for cows, dams and sires according to calving year and the genetic correlations were presented.     

Estimation of genetic and phenotypic relationships between age at first calving and productive performance in Iranian Holsteins

Calving records from the Animal Breeding Center of Iran collected from January 1990 to December 2007 and comprising 207,106 first calving events of Holsteins from 2,506 herds were analysed using univariate and bivariate linear sire models to estimate heritabilities and genetic correlations between age at first calving (AFC) and productive performance. Average AFC was 26.48 months in this study. The peak in the frequency distribution of AFC clearly exists coinciding with cows calving for the first time at approximately 25 months of age. Heritability estimate for AFC was 0.34 which was greater than the corresponding values for productive traits. The heritability estimates were low to medium for productive traits which ranged from 0.17 to 0.26 for cows in their first calvings. Except for fat and protein percentages of milk, phenotypic and genetic correlations between AFC and productive performance traits were low to moderately negative. Range of genetic correlations between productive traits was −0.53 to 0.99. Reduction of age at first calving appeared to have a negative effect on first lactation protein and fat percentages; however, it had positive effects on milk yield, fat yield, protein yield and their mature equivalents. It seems that reducing age at first calving to 24–25 months is probably more profitable than reducing age at first calving to an earlier time in Iranian conditions.     

Crossbreeding effects on milk yield traits and calving interval in spring‐calving dairy cows

The aim of the study was to assess crossbreeding effects for 305‐day milk, fat, and protein yield and calving interval (CI) in Irish dairy cows (parities 1 to 5) calving in the spring from 2002 to 2006. Data included 188 927 records for production traits and 157 117 records for CI. The proportion of genes from North American Holstein Friesian (HO), Friesian (FR), Jersey (JE) and Montbéliarde (MO) breeds, and coefficients of expected heterosis for HO×FR, HO×JE and HO×MO crosses were calculated from the breed composition of cows’ parents. The model used to assess crossbreeding effects accounted for contemporary group, age at calving within parity, linear regression on gene proportions for FR, JE and MO, and linear regression on coefficients of expected heterosis for HO×FR, HO×JE and HO×MO, as fixed effects, and additive genetic, permanent environmental and residual as random. Breed effects for production traits were in favour of HO, while for CI were in favour of breeds other than HO. The highest heterosis estimates for production were for HO×JE, with first‐generation crosses yielding 477 kg more milk, 25.3 kg more fat, and 17.4 kg more protein than the average of the parental breeds. The highest estimate for CI was for HO×MO, with first‐generation crosses showing 10.2 days less CI than the average of the parental breeds. Results from this study indicate breed differences and specific heterosis effects for milk yield traits and fertility exist in Irish dairy population.     

A comparison of holstein friesians,Dutch friesians and dutch red and whites. I. Production characteristics

Production characteristics of purebred Holstein Friesians (HF), Dutch Friesians (DF) and Dutch Red and Whites (DRW) were compared to determine the genetic differences between the three breeds under Dutch production systems. In the first, second, and subsequent lactations, HF animals produced, respectively, 18.8, 20.7 and 18.8% more milk and 10.5, 11.1 and 9.8% more fat and protein than the DF animals. The DRW animals produced 7.3, 7.0 and 6.4% less milk and 7.2, 7.1 and 5.9% less fat and protein in the first three lactations, respectively, than the DF animals.In beef and veal production the HF animals had a slightly less efficient conversion of feed to gain than the DF animals, but the feed conversion of the DRW was better than that of the DF animals. Slaughter quälity traits (dressing percentage and fleshiness) were lowest for the HF animals in all slaughter categories and highest for the DRW animals. Carcass weights averaged 305 kg for HF cows, 285 kg for DF cows and 297 kg for DRW cows. For the HF, DF and DRW cows, percentages of calves born alive were, respectively, 88.6, 93.9 and 87.0%; birth weights were, respectively, 42.7, 36.2 and 39.2 kg; days of pregnancy were, respectively, 282.2, 276.9 and 278.0; and inseminations per pregnancy were respectively, 1.91, 1.55 and 1.59. Other averages for HF, DF and DRW were, respectively, age at first calving 778, 748 and 759 days; first calving interval 400, 370 and 387 days; and later calving intervals 389, 374 and 381 days. Significant differences in disease frequencies and reasons for calling were observed between the breeds.     

Holstein Friesians,Dutch Friesians and Dutch Red and Whites on two complete diets with a different amount of roughage: Differences in performance between first and second lactation

Groups of 11 Holstein Friesian (HF), 11 Dutch Red and White (DRW) and 12 Dutch Friesian (DF) second calved cows were fed a complete diet with only roughage (a mixture of grass- and corn-silage) or the same mixture of roughage with 50% concentrates on a dry matter basis. The animals had participated in the same experiment during their first lactation.For none of the characteristics was a significant breed-feed composition interaction found. The differences between breeds in feed intake, milk production, body weight and gain were equal with both feed compositions.The breeds differed significantly in the increase in milk, fat and protein yield from the first to the second lactation. This increase was 902, 194 and 103 kg milk, 46, 16 and 5 kg fat and 27, 1 and 3 kg protein for the HF, DRW and DF animals, respectively. The body weight gain of the concentrates group in the second lactation was much less than in the first lactation.For the HF animals, 55% of total energy intake was used for milk yield, 37% for maintenance and 8% for gain; corresponding values for the DRW animals were 48, 41 and 11%, respectively, and for the DF animals 44, 37 and 19%, respectively. For the concentrates group, this partition was 51, 36 and 13%, respectively, and for the roughage group 47, 41 and 13%, respectively.     

Genetic and phenotypic parameters and annual trends for milk production and fertility traits of the Sahiwal cattle in semi arid Kenya

Data comprising 7211 lactation records of 2894 cows were used to estimate genetic and phenotypic parameters for milk production (lactation milk yield, LMY and lactation length, LL) and fertility (calving interval, CI; number of services per conception, NSC and age at first calving, AFC) traits. Genetic, environmental and phenotypic trends were also estimated. Variance components were estimated using univariate, bivariate and trivariate animal models on based restricted maximum likelihood procedures. Univariate models were used for each trait, while bivariate models were used to estimate genetic and phenotypic correlations between milk production and fertility traits and between LMY, LL, CI and NSC within each lactation. Trivariate models were used in the analysis of LMY, LL, CI and NSC in the first three lactations. Heritability estimates from the univariate model were 0.16, 0.07, 0.03, 0.04 and 0.01 for LMY, LL, CI, AFC and NSC, respectively. The heritability estimates from trivariate analysis were higher for milk production traits than those from univariate analyses. Genetic correlations were high and undesirable between milk production and fertility traits, while phenotypic correlations were correspondingly low. Genetic trends were close to zero for all traits, while environmental and phenotypic trends fluctuated over the study period.     

Genetic and Environmental Effects on the Productivity of Holstein–Friesian Cattle under the Climatic Conditions of Central Sudan

A herd of 370 Holstein–Friesian cows were maintained in Central Sudan, Khartoum for intensive dairy production during the period 1990–1996. The area is characterized by high temperatures during the day and cools down at night, with an average thermal-humidity index (THI) of 74.8. The average adjusted lactation milk yield, milk yield per day, milk yield per day of calving interval and lactation length of the animals in the herd were 5117±123 (SE) kg, 14.7±0.25 kg, 11.3±0.36 kg and 350±8.0 days, respectively. Heifers calved at 25.2±2.3 (SD) months of age. The variation was large, which suggested large environmental fluctuations. Sire variance contributed 1.35% and 19.6% to the total variance in cows and heifers, respectively, while cow within sire contributed 19%. The heritabilities of total lactation yield, 305-day yield, milk per day of lactation, milk per day of calving interval, and lactation length in heifers were 0.78±0.24, 0.36±0.34, 0.39±0.24, 0.23±0.23, and 0.23±0.22, respectively. In cows, the heritability estimates were 0.05±0.24, 0.06±0.24, 0.08±0.24, 0.00 and 0.00 for the same traits, respectively. The repeatabilities of total lactation yield, 305-day yield, milk per day, milk per day of calving interval and lactation length were 0.02±0.03, 0.22±0.03, 0.17±0.02, 0.05±0.02 and 0.00, respectively. Regression analysis showed that, for each unit increase in THI, milk yield decreased by 0.29±0.04 kg. The stress usually caused by the combined effects of temperature and humidity was not severe in this area.     

The impact of installation of automatic milking system on production and reproduction traits of dairy cows

The objective of the research was the evaluation of change in the traditional milking system using automatic milking system in the scope of the selected reproduction features of dairy cows of the Polish Holstein–Friesian breed. Animal material consisted of 2,818 cows used on nine farms equipped with the automatic milking system Astronaut A4 made by Lely. The cows were controlled in the scope of services per conception, service period, length of pregnancy, calving interval and calving to conception period, milk yield, protein and fat content obtained in lactations of 305 days. The selected traits were observed between 2005 and 2015. In this period, the milking system was changed from the conventional to automated one. The collected data material was statistically processed, using the multifactorial analysis of variance. The period between the first calving and the second effective insemination was reduced by 11.8 days, and the period between the second calving and the third effective insemination was shortened by 4 days after the installation of the automatic milking system. The increase in milk yield by 466 kg during 305‐day lactation was observed among primiparous cows. The percentage of protein and fat content in the researched groups decreased; moreover, the fall of intergroup variability was noticeable, which may be a sign of the levelling of the yield within the herd.     

Adjustment of lactation yield for age at calving in relation to level of production

The influence of age at calving on 305-day milk, fat and protein yield in relation to herd and population level of production was investigated and a procedure for age adjustment was derived.Age differences were estimated by a repeatability model for 49 669 complete 305-day lactation records (kg milk, kg fat and kg protein) from 27 965 Dutch Friesian cows calving between 1 June 1979 and 31 May 1982. Several mathematical functions were applied to the estimated age differences. The best fit was by a second degree polynomial for Lactations 1 and 2 separately (R² ⩾ 0.995) and a linear function including the log of age at calving for third and later lactations (R²=0.967).One set of adjustment factors was found to apply to all herd levels of production. However, age adjustment factors were different from those found by Dommerholt (1975) where the population level was about 1000 kg milk lower. A more accurate age adjustment would be obtained by updating the mean production of heifers at 24 months of age and using mathematical functions for computation of age factors.     

Relationships between age at first calving and first lactation milk yield, and lifetime productivity and longevity in dairy cows

Lifetime records of 442 Holstein cows on one farm in North Queensland, Australia, were analysed to evaluate the effects of age at first calving (AFC) and first lactation milk yield on parities per lifetime, longevity, milk yield in subsequent lactations, lifetime milk production and the longevity index (LI), that is the proportion of a cow's life spent in active milk production. The mean daily yield in the first lactation was a reliable indicator of milk yield in subsequent lactations, estimated lifetime production, longevity and LI. The afc had no effect on lifetime days in milk. Neither the AFC nor the milk yield in the first lactation significantly affected the number of parities per lifetime. For the majority of cows, which produced less than 30 l/day in the first lactation, there was a significant positive relationship between longevity and AFC. However, none of the cows that produced more than 30 l/day in the first lactation survived for more than two lactations. The optimal AFC was thus two to two-and-a-half years, as these cows had the highest first lactation yield, estimated lifetime production and LI. The optimal mean daily yield in the first lactation was 20 to 30 l/day, as these cows lived longer and had a higher LI and lifetime production.     

A survey of the phosphorus and calcium contents of pastures and the serum inorganic phosphorus and calcium contents of cows on four Manawatu dairy farms

Serum inorganic phosphorus (Pi) and calcium (Ca) concentrations were assessed in 20 cows on each of four Manawatu factory supply dairy farms. Blood was taken from each cow before calving and at six-week intervals during lactation. Bleeding coincided with herd testing. Herds of Friesian or Friesian X cows and Jersey or Jersey X cows were compared on adjacent farms on a Central Yellow-brown Sand and on adjacent farms on a Peat Loam overlying a Central Yellow-brown Earth soil. Pasture mass and composition were estimated to grazing height in the next two paddocks to be grazed in the rotation. Mean serum Pi concentration was higher in cows on sandy soils (1.55 mmol Pi/l than in cows on the peat loam (1.34 mmol Pi/l (P<0.001). Concentrations were highest before calving (1.69 mmol Pi/l) but fell to low levels at peak lactation (1.17mmol Pi/l when 70% of cows were below the minima of the 'normal range', and during the drought (1.29 mmol Pi/l. Pasture phosphorus (P) concentrations were adequate to support cow nutrition for lactation (>0.33% DM, ad lib. feeding) until the summer drought when low herbage mass would have restricted milk production. Serum Ca was adequate for lactating cows and changed little between months or between cows (mean 2.12 mmol Ca/l). No metabolic disorders relating to mineral deficiencies were observed. It appears that serum Pi in a high proportion of cows falls below the normal range during peak lactation without cows displaying clinical deficiency symptoms or a depression in butterfat production.     

西宁奶牛场荷斯坦奶牛乳脂率测定

对西宁奶牛场３２７头中国荷斯坦泌乳奶牛的乳汁进行乳脂率测定。结果：乳脂率平均值为３．４９％，变动范围１．２％～６．８％；乳脂率在２．７％以下的牛３１头，占全群牛的９．５％，２．８％～３．２％的牛６７头，占２０．５％，３．３％～３．９％的牛１６３头，占４９．８％，４％以上的牛６６头，占２０．２％；不同胎次、产奶量及不同泌乳期乳脂率有一定的变化。     

Differences in feed intake between holstein Friesian,Dutch Red and White and Dutch Friesian cattle

In a comparison of Holstein Friesian (HF) from North America with Dutch Red and Whites (DRW) and Dutch Friesians (DF), the feed intake of 20 animals per breed was measured at different stages of lactation and at different ages. In the experiments with dairy cows, the animals were offered concentrates individually according to their milk yield. In all experiments roughage (silage or hay) was offered ad libitum.In all experiments the DRW animals ate less roughage than the HF and DF animals, although they ate the lowest amount of concentrates in nearly all experiments, due to their lower milk yield. The HF animals were offered more concentrates than the DF animals, but ate the same amount of roughage.     

Genetic evaluation of length of productive life in the Spanish Holstein-Friesian population. Model validation and genetic parameters estimation

Functional longevity (FL), measured as length of productive life (LPL) adjusted by production level, has been regarded as an important trait to measure the global functional aptitude of a cow, particularly when direct measures of the functional traits (health and reproductive performance) are not available. The objective of this study was to analyze the trait FL making use of survival analysis techniques in order to propose a model for the genetic evaluation of this trait in the Spanish Holstein Friesian population. The data set consisted of 133,629 registered cows of three regions; Andalusia, Basque Country and Catalonia. The hazard function was described as the product of a baseline hazard function and the time-independent effects of age at first calving, lactation number-stage of lactation, annual change in herd size, milk, fat and protein yield. Sire and maternal grandsire and herd-year-season of calving were considered as random effects. Percentage of right-censored data ranged from 41.9% to 52.7% for the analysed data sets. All the effects analyzed were significant (P < 0.0001) and had a great influence on the risk of culling of a cow, except for the age at first calving which showed a relatively small effect. Higher risk for factors such as age at first calving, change in herd size and relative level of milk production was associated with the more extreme classes. The consistency of the results among regional samples which represent diverse production systems in the population indicated that the proposed model could be applied at the national level. The relatively low heritability (0.048 to 0.074) suggests that genetic improvement of LPL could be effective if the direct evaluation is combined with indirect measures of LPL.     

The Estimation of Genetic Parameters of Holstein Dairy Cows in Ningxia Region

The genetic parameters of milk fat percentage (FP), milk protein percentage (PP), somatic cell score (SCS), milk yield of 305 days (MYD), age at first calving (AFC),calving interval (CI) and linear classification scores (LCS) were estimated using the DHI data of 2008 to 2016 in Ningxia area of 27 444 Holstein dairy cows and type records. With the aid of DMU v 6.0 AI-REML software, DMU combined with EM algorithm and multi character animal model was used to model the influence factors of the birth season, herd, year, parity and individual additive genetic effect. The results showed that FP, PP, SCS, MYD, AFC, CI and LCS's heritability were 0.14, 0.19, 0.19, 0.31, 0.37, 0.10, 0.07, respectively. At the same time, the breeding value, genetic correlation and CPI2 values of different traits were calculated. The genetic evaluation for dairy cows in Ningxia, could be more in-depth understanding of the basic situation of the herd, to provide basic data for the construction of dairy cow breeding matching selection, planning and selection index.     

宁夏地区荷斯坦奶牛遗传参数估计

利用2008-2016年出生的27 444头宁夏地区荷斯坦奶牛生产性能（dairy herd improvement,DHI）数据及体型线性评分数据计算乳脂率（fat percentage,FP）、乳蛋白率（protein percentage,PP）、体细胞评分（somatic cell score,SCS）、305 d产奶量（milk yield of 305 days,MYD）、初产日龄（age at first calving,AFC）、产犊间隔（calving interval,CI）和体况评分（linear classification scores,LCS）的遗传参数。利用DMU v 6.0软件,采用AI-REML模块结合EM算法并配合多性状动物模型,以季节、场、年份、胎次和动物个体加性遗传效应作为模型的影响因素。计算结果表明,宁夏地区奶牛的FP、PP、SCS、MYD、AFC、CI和LCS的遗传力分别为0.14、0.19、0.19、0.31、0.37、0.10和0.07,同时得出了奶牛不同性状的育种值、遗传相关和奶牛生产性能指数2（China performance index 2,CPI2）值。本研究通过对宁夏地区奶牛DHI数据的深挖和遗传评估,准确地把握了宁夏奶牛群体结构特征,对于奶牛的选种选配、育种规划和选择指数的构建有重要意义。     

Holstein Friesians,Dutch Friesians and Dutch Red and Whites on two complete diets with a different amount of roughage: Performance in first lactation

Groups of 20 Holstein Friesian (HF), 23 Dutch Red and White (DRW) and 20 Dutch Friesian (DF) heifers were fed a complete diet with only roughage (a mixture of grass and corn-silage) or the same mixture of roughage with 50% concentrates on a dry matter basis, from 2 months before the first calving until 10 months after calving.No significant breed-feed composition interactions were found for any of the characteristics.The HF, DRW and DF heifers differed significantly in feed intake and milk production. They consumed 4725, 4432 and 4476 kVEM, respectively, and produced 5331, 4562 and 4660 kg milk, respectively, with 3.96, 4.20 and 4.22% of fat, respectively, and 3.25, 3.49 and 3.40% of protein, respectively.The concentrates and roughage groups differed significantly in feed intake, milk production, average body weight and gain. The respective mean values for the concentrates and the roughage groups were: 5160 and 3928 kVEM, 5534 and 4168 kg milk, 4.00 and 4.26% fat, 3.52 and 3.24% protein, 542 and 506 kg body weight and 97 and 38 kg gain, respectively.HF heifers used 51% of their energy intake for milk production (milk energy), DF heifers 49% and DRW heifers 48%. Both feed composition groups used 49% of their energy intake for milk production, but the roughage group used 8% more of the energy intake for maintenance than the concentrates group, as a result of lower energy intake.     

Comparison of the performance of Holstein-Friesian and Jersey×Holstein-Friesian crossbred dairy cows within three contrasting grassland-based systems of milk production

The performance of spring calving Holstein-Friesian (HF) and Jersey×Holstein-Friesian (J×HF) dairy cows was examined during three successive years (mean of 35 HF cows and 31 J×HF cows per year). Throughout the experiment cows were managed on one of three grassland-based systems of milk production, namely low concentrate (LC), medium concentrate (MC) or high concentrate (HC). Post-calving, cows were housed and offered grass silage, supplemented with 6.0, 8.0 and 10.0 kg concentrate/cow/d in systems LC, MC and HC, respectively (mean period from calving to start of full time grazing, 69 days). During the grazing period target concentrate feed levels were 0, 2.5 and 5.0 kg/cow/d for systems LC, MC and HC, respectively (mean period from start of full time grazing to start full time re-housing, 206 days). Full lactation concentrate inputs were 530, 1092 and 1667 kg/cow, in systems LC, MC and HC, respectively. There were no significant genotype×system interactions for any of the milk production parameters examined. Food intake during the confinement and grazing periods was unaffected by genotype. Milk yield was highest with HF cows while milk fat and milk protein content were highest with the J×HF cows (P<0.001). Genotype had no effect on fat plus protein yield. Milk yield and fat plus protein yield were higher with systems MC and HC than with LC (P<0.001). HF cows were on average 44 kg heavier than J×HF cows, while the mean condition score of the J×HF cows was approximately 0.2 units higher than that of the HF cows (P<0.001). Live weight and condition score changes during the lactation followed similar trends with both genotypes. The J×HF cows had fewer days to first observed heat (P<0.05), a higher conception rate to first service (P<0.01), first plus second service (P<0.001), and a higher pregnancy rate at the end of the breeding season (P<0.05). Although mean somatic cell score was unaffected by genotype, the proportion of cows with one or more cases of mastitis was lower with the J×HF cows (P<0.05). In summary, while the J×HF cows had improved fertility performance compared to the HF cows, both genotypes exhibited similar levels of tissue mobilisation and deposition throughout the lactation, while there was no evidence of a genotype×grassland system interaction for any of the milk production parameters examined.     

Treatment and control of an outbreak of fat cow syndrome in a large dairy herd

An outbreak of fat cow syndrome occurred in a herd of 300 Friesian and Friesian/Holstein dairy cows calving predominantly between January and May. The herd came in off grass in good condition despite a long and hot summer. The dry cows received a diet of grass silage, brewing waste and minerals until the end of December, but the grass silage was butyric and was partially replaced by maize silage. By January 23, 16 of 70 calving cows (23 per cent) had appeared to suffer milk fever. Subsequent blood tests revealed that the cows may have been ketotic, and clinical and post mortem examination showed that they were probably suffering from fat cow syndrome. The freshly calved sick cows were treated with glucose, and corticosteroids were injected every second day into those which remained ill. The cattle had received a high energy diet, but the cows still to calve were placed on a diet of low metabolisable energy (77 MJ/cow) but adequate levels of undegradable protein. The problem was associated with a possible clostridial infection in two cows and with reduced fertility.