***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: One hundred and twenty early lactating Holstein dairy cows were assigned to investigate the effect of dietary chromium ( Cr ) supplementation ( 0 or 6 mg Cr/head/day from organic preparation ) on the productive and reproductive performance as well as on some blood serum parameters under heat stress ( 35 - 40 degrees C ) . Cows received treatment from 3 weeks pre-partum through 12 weeks post-partum . Chromium supplemented diet had lower body weight loss and improved dry matter intake with consequent reduction in the energy balance deficits during the first period after calving when compared with the control group . Chromium supplementation increased ( p < 0.05 ) milk yield by 6.7 % , 12.3 % and 16.5 % at 4 , 8 and 12 weeks post-partum , respectively , whereas milk composition and milk to feed ratio were unaffected ( p > 0.05 ) when compared with the control . Moreover , dietary Cr supplementation had no effect ( p > 0.05 ) on blood serum glucose , calcium and phosphorus concentrations . A reduction ( p < 0.05 ) of non-esterified fatty acids at 1 week pre-partum , 2 and 4 weeks post-partum was also observed . Serum insulin concentration increased whereas cortisol concentration decreased , when compared with the control group , throughout the whole experimental period . Also Cr supplementation showed a trend towards improving reproductive performance as indicated by increased percentage of pregnant cows in the first 28 days of breeding . It could be concluded that dietary Cr supplementation at level of 6 mg/head/day may offer a potential protective management practice to lessen the effect of heat stress in dairy cattle OBJECTIVE To evaluate the effects of length of exposure to prepartum transition diets on milk yield , fat and protein production . DESIGN Prospect i ve cohort study . The number of days that the cows were fed the prepartum transition diets was the exposure of interest . PROCEDURES Holstein and Holstein x Jersey cows ( n = 1008 ) were enrolled .  Diets given in the far-off dry period ( from end of lactation until approximately 3 weeks before expected parturition ) consisted of ad libitum access to perennial ryegrass pastures . Prepartum transition diets included perennial ryegrass pasture , ryegrass silage , cereal hay , grain , grain by-product , protein meals , BioChlor , sodium monensin , virginiamycin or tylosin , MgSO(4 ) , trace elements and vitamins . On a dry matter basis , these contained 16.0 % crude protein , 4.2 % rumen undegradable protein , and 9.9 mJ metabolisable energy/kg . Diets provided an estimated metabolisable protein balance of 286 g/day and dietary cation anion difference of -150 meq/kg dry matter . Statistical models controlled for effects of herd , calving day , breed , age and gestation period . RESULTS Increasing length of exposure to the prepartum transition diets significantly increased the 4.0 % fat- and 3.2 % protein-corrected milk yield and milk-protein yield as a linear and quadratic effect . The optimal duration of exposure to the prepartum transition diets was 25 days for fat- and protein-corrected milk production and 22 days for milk protein production . Milk-fat percentage decreased significantly and linearly with increasing exposure to the prepartum transition diets ; however , milk-fat yield or milk-protein percentage did not vary significantly with duration of exposure to the diets . CONCLUSIONS Increasing exposure to prepartum transition diets increased milk and milk-protein yields and decreased the milk fat-percentage , but not the milk-protein percentage or milk-fat yield Milk protein concentration in dairy cows has been positively associated with a range of measures of reproductive performance . It was possible that these associations were due to confounding by milk volume . A retrospective single cohort study was conducted using data collected from 74 dairy herds with seasonal or split calving patterns . Associations between milk protein concentration and reproductive performance in Holstein dairy cows were assessed using r and om effects logistic regression . The key finding from this study was that the associations between milk protein concentration in early lactation and reproductive performance were not due to confounding by milk yield . Associations between milk protein concentration and reproductive performance were weaker at higher early lactation milk yields , but positive associations were evident at all milk volumes assessed . The second major finding was that increases in milk yield were associated with improved proportions of cows pregnant by wk 6 and 21 at low to moderate milk protein concentrations but with decreases in these reproductive measures at high milk protein concentrations . Thus , no simple relationship is present between milk yield and reproductive performance ; effects of milk yield depend on milk protein concentration . These results indicate that mechanisms causing the associations between milk protein concentration and reproductive performance may be linked to milk yield but these mechanisms operate over a wide range of milk yields ( < 2,000 to ≥5,000 kg in the first 120d of lactation ) . Further research is required to identify the causes of these associations Twenty preparturient dairy cows were in a 2-yr switchover design to test effects of dietary ions on incidence of milk fever .  In yr 1 , cows were blocked and assigned r and omly 45 days prepartum to one of two diets ; one diet contained an excess of anions , and the second diet contained an excess of cations . In yr 2 , cows were changed to the opposite diet . Both diets were equivalent for crude protein ( 11 % ) , calcium ( .65 % ) , phosphorus ( .25 % ) , and energy on a dry basis but differed for quantities of chlorine , sulfur , and sodium . Both diets were chopped alfalfa hay , corn silage , high moisture corn , and vitamin-mineral mix . Diets were available ad libitum as complete rations . There were no differences in dry matter intake of the diets . Cows consuming the anionic diet had no milk fever , but cows consuming the canionic diet had 47.4 % incidence . Sample s of blood plasma showed that cows consuming the anionic diet maintained calcium and phosphorus through parturition , whereas cows consuming the cationic diet decreased in these minerals around calving . Hydroxyproline was higher for cows consuming the anionic diet during the peripartal period compared to cows consuming the cationic diet .  Milk produced in the lactation subsequent to prepartum treatment was 6.8 % less for cows offered the cationic diet . When milk production of paretic and nonparetic cows offered the cationic diet was compared , milk was reduced 14 % with milk fever Forty-six multiparous Holstein cows were assigned at 5 d postpartum to a completely r and omized design employing a 2 x 3 factorial arrangement of treatments . Factors were 0 and 5 % added prilled long-chain fatty acids ( DM basis ) and three forage to concentrate ratios ( 45:55 , 64:36 , 84:16 ) . Diets consisted of immature alfalfa silage and a concentrate of shelled corn and soybean meal with or without fat replacing a portion of the corn .  Mean plasma concentration of cholesterol was higher for cows fed 5 % vs. 0 % fat and increased over the first 100 d in milk for all animals regardless of treatment . There were no differences in reproductive performance due to either of the main effects . Mean plasma progesterone was higher due to fat treatment in the mid to late luteal phase of the second postpartum cycle as well as the metestrous to early luteal phase and mid to late luteal phase of the third cycle . Even though progesterone concentrations were higher in cows fed 5 % fat during the luteal phase after breeding , the conception rates at this service were not different from those fed 0 % fat . The biological significance of increased plasma progesterone concentration was not identified with any postpartum reproductive trait measured in this trial Conjugated linoleic acid ( CLA ) reduces mammary milk fat synthesis in a dose-dependent manner . Our objective was to determine the effects of lipid-encapsulated CLA ( LE-CLA ) supplementation on milk production , reproductive performance and metabolic responses in lactating dairy cows fed a grass silage-based diet . Seventy-two Holstein-Friesian cows ( 32 primiparous and 40 multiparous ) were used in a completely r and omized block design . Cows received either 80 g of LE-CLA daily or 60 g of calcium salts of palm fatty acids daily ( control ) from parturition until 60 days in milk . LE-CLA contained a 50:50 mix of cis-9,trans-11 CLA and trans-10,cis-12 CLA , result ing in a daily intake of 6 g of each isomer . Milk production and dry matter intake were recorded daily , and blood sample s were collected 3-times a week . Blood sample s were analysed for circulating concentrations of glucose , non-esterified fatty acids ( NEFA ) , β-hydroxybutyrate ( BHBA ) , insulin and insulin-like growth factor-I ( IGF-I ) . Progesterone was measured in blood sample s collected after the first post-partum insemination . Ovarian ultrasound examinations commenced at 8 - 10 d post partum and were carried out 3-times a week until first ovulation . LE-CLA treatment result ed in decreased milk fat concentration , with consequent improvements in energy balance and body condition score ( BCS ) . The peak concentration of NEFA in blood was reduced by LE-CLA , but circulating concentrations of insulin , glucose , IGF-I , BHBA and progesterone were not affected . There was no effect of LE-CLA supplementation on the post-partum interval to first ovulation . Services per conception tended to be reduced . The reduction in milk energy output and improvement in energy status and BCS in LE-CLA-supplemented cows provides a strong rationale for further studies with greater cow numbers to test effects on reproductive performance Clinical mastitis and reproductive records from two southern California dairy herds were used in a cross-sectional study to determine the risk of an altered interestrus interval  following clinical mastitis . An altered interestrus interval was defined as cycles occurring at either less than 18 day or more than 24-day intervals . The data were stratified by herd to assess herd differences and by lactation number to assess confounding by cow parity . The predominant pathogen isolated from mastitis cases in Herd 1 was Staphylococcus aureus , whereas the predominant pathogens in Herd 2 were gram-negative isolates . Cows in Herd 1 which had coliforms cultured from mastitic milk were excluded in the analysis for comparison with Herd 2 . In Herd 1 , cows with clinical mastitis were less likely to have an altered interestrus interval ( Relative Risk [RR]=0.9 ; 95 % Confidence Interval [CI]=0.6,1.6 ) than herdmates without clinical mastitis . However , cows in Herd 2 were almost two times more likely to have an altered interestrus interval following an episode of clinical mastitis compared to herdmates without clinical mastitis ( RR=1.6 ; 95 % CI=1.3,2.0 ) . Because herd management practice s differ and could cause differences in mastitis and reproductive outcomes at the dairies , this preliminary field evidence should be followed by prospect i ve studies of luteal function after clinical coliform mastitis The effects of grain , fructose , and histidine on ruminal pH and fermentation products were studied in dairy cattle during an induced subacute acidosis protocol . Thirty Holstein heifers were r and omly allocated to 5 treatment groups : ( 1 ) control ( no grain ) ; ( 2 ) grain [ fed at a crushed triticale dry matter intake ( DMI ) of 1.2 % of body weight ( BW ) ] ; ( 3 ) grain ( 0.8 % of BW DMI)+fructose ( 0.4 % of BW DMI ) ; ( 4 ) grain ( 1.2 % of BW DMI)+histidine ( 6 g/head ) ; and ( 5 ) grain ( 0.8 % of BW DMI)+fructose ( 0.4 % of BW DMI)+histidine ( 6 g/head ) in a partial factorial arrangement . Heifers were fed 1 kg of grain daily with ad libitum access to ryegrass silage and alfalfa hay for 10 d. Feed was withheld for 14 h before challenge day , on which heifers were fed 200 g of alfalfa hay and then the treatment diets immediately thereafter . Rumen sample s were collected 5 min after diet ingestion , 60 min later , and at 3 subsequent 50-min intervals . Grain decreased ruminal pH and increased ammonia , total volatile fatty acid ( VFA ) , acetate , butyrate , propionate , and valerate concentrations compared with controls . The addition of grain had no effect on ruminal D- and L-lactate concentrations . Fructose markedly decreased ruminal pH and markedly increased D- and L-lactate concentrations . Fructose increased total VFA and butyrate and decreased valerate concentrations . Although histidine did not have a marked effect on ruminal fermentation , increased concentrations of histamine were observed following feeding . This study demonstrates that the substitution of some grain for fructose can lower ruminal pH and increase VFA and lactate concentrations , warranting further investigation into the role of sugars on the risk of acidosis in dairy cattle The aim of this study was to investigate the relationship between measures of body condition score collected from calving until wk 26 of lactation and reproductive measures ( calving interval , days to first heat , days to first service , and conception at first service ) . Since 19 
    Output:
    
There was no multivariable model developed to assess variables associated with calving to pregnancy interval but , univariably , increased metabolizable energy balance was associated with a shorter calving to pregnancy interval whereas increased milk production was associated with longer time to pregnancy .
Increased intake of some AA , particularly threonine and lysine , were associated with a longer calving to pregnancy interval .
It is clear nutritional management around calving can influence reproductive success .
The importance of dietary fats and increased energy and protein balances in early lactation for improved fertility outcomes is supported and suggests that starch and sugars may have different effects on the proportion of cows that are pregnant to AI .