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Brangus cows (n = 29) were used in three experiments to evaluate the effects of parity (multiparous vs. primiparous) and potential genetic merit for milk production (high vs. low) on forage intake during late gestation, early lactation, and late lactation. Cows were selected for milk production based on their sire's EPD for milk production (MEPD). Cows had ad libitum access to (130% of previous 2-d average intake) low-quality hay (5.3% CP and 76% NDF), and cottonseed meal was supplemented to ensure adequate degradable intake protein. All females were adapted to diets for at least 7 d, and individual intake data were collected for 9 d. During the lactation trials, actual milk production was determined using a portable milking machine following a 12-h separation from calves. During late gestation, multiparous cows consumed 24% more (P = 0.01) forage DM (kg/d) than primiparous cows; however, parity class did not influence forage intake when intake was expressed relative to BW. Furthermore, MEPD did not influence forage intake during late gestation. During early lactation, multiparous cows produced 66% more (P < 0.001) milk than primiparous cows, and high MEPD tended (P = 0.10) to produce more milk than low MEPD. Multiparous cows consumed 19% more (P < 0.0001) forage DM than did primiparous cows when expressed on an absolute basis, but not when expressed on a BW basis. High-MEPD cows consumed 8% more (P < 0.05) forage DM than did low-MEPD cows. During late lactation, multiparous cows produced 84% more milk than primiparous cows, although MEPD did not influence (P = 0.40) milk yield. In addition, multiparous cows consumed 17% more (P < 0.01) forage DM per day than primiparous cows, but when intake was expressed relative to BW, neither parity nor MEPD influenced forage DMI during late lactation. Milk yield and BW explained significant proportions of the variation in forage DMI during early and late lactation. Each kilogram increase in milk yield was associated with a 0.33- and 0.37-kg increase in forage DMI for early and late lactation, respectively. Results suggest that multiand primiparous cows consume similar amounts of low-quality forage DM, expressed per unit of BW, during late gestation and lactation. Selecting beef cows for increased genetic merit for milk production increases forage DMI during early lactation.

Milk yield from 273 Angus- and Hereford-sired cows and preweaning performance of their calves were used to determine how accurately milk EPD of Angus and Hereford sires predicted milk production of crossbred daughters and subsequent calf performance. Mean milk EPD (kg) for high Angus (HA), low Angus (LA), high Hereford (HH), and low Hereford (LH) bulls (n = 41) selected as sires were +8.7, -6.2, +7.6, and -4.8, respectively. Cows calved in spring or fall from 1992 to 1997 and yielded a total of 660 records. Twenty-four-hour milk production of the cows was estimated by two weigh-suckle-weigh measurements at monthly intervals. The statistical model included breed, milk EPD level, sire of cow within breed and milk EPD level, year, season, cow age, calf sire, sex, and all two- and three-way interactions. Means were obtained for monthly milk production, total milk production, time and yield of peak production, monthly calf weights, monthly cow weights and body condition scores (1 through 9), and calf birth and weaning data. The least squares means for 24-h milk production (kg) of HA, LA, HH, and LH with P-values for high vs low, across breeds, were, respectively, as follows: mo 1: 6.9, 5.9, 7.1, and 5.7 (P < 0.01); mo 2: 7.2, 6.1, 6.9, and 5.7 (P < 0.01); mo 3: 6.1, 5.1, 5.1, and 4.3 (P = 0.01); mo 4: 6.1, 4.9, 4.9, and 4.8 (P = 0.01); mo 5: 4.8, 4.0, 4.2, and 3.8 (P = 0.01); mo 6: 4.7, 3.4, 3.2, and 3.0 (P < 0.01); and mo 7: 3.7, 2.5, 3.0, and 3.0 (P = 0.05). Least squares means for total milk (kg) were 911.4, 729.6, 758.0, and 664.2 (P < 0.01); for yield at peak (kg/d) were 7.0, 5.7, 6.1, and 5.2 (P < 0.01); for birth weight (kg) were 37.1, 37.9, 38.3, and 38.8 (P = 0.31); for 205-d weight (kg) were 237.3, 218.2, 222.2, and 214.1 (P < 0.01); for final cow weight (kg) were 482.4, 505.4, 509.5, and 511.7 (P = 0.11); and for final cow BCS were 4.9, 5.3, 5.1, and 5.2 (P < 0.01). The correlations of total production with the monthly productions were 0.52, 0.56, 0.52, 0.54, 0.35, 0.37, and 0.31 (P < 0.01) and were 0.12 with birth weight, 0.45 with 205-d weight, -0.12 with final cow weight, and -0.26 with final cow body condition score (all P < 0.01). Daughters of high-milk EPD sires produced more milk and weaned heavier calves than those of low-milk EPD sires at the expense of body condition. These results suggest that sire milk EPD are sufficiently associated with milk yield and calf performance to be useful tools in genetic improvement of preweaning performance.

In dairy cattle, increased circulating growth hormone has been associated with selection for greater milk yield. This study tested the hypothesis that beef cows divergently selected for milk production would have differing GH responses to a challenge dose of GHRH. Growth hormone response to a challenge of GHRH was measured in 36 Angus-sired cows ranging from 6 to 10 yr of age. The cows were classified as high milking (n = 16) or low milking (n = 20), on the basis of their sires' milk EPD. Mean milk EPD (in kilograms) were 16.6 and -14.4 for high and low milking cows, respectively. Milk production was estimated by the weigh-suckle-weigh procedure. Blood samples were taken immediately before and 10 min after a clearance dose of 4.5 microg of GHRH/100 kg BW (injected i.v.) and, 3 h later, immediately before and 10 min after a challenge dose of either 1.5 or 4.5 microg of GHRH/100 kg BW. Each animal received both challenge doses, and the doses were randomly assigned across 2 d of blood collection. Serum concentrations of GH and IGF-I were measured by RIA. Serum IGF-I was measured in the baseline blood sample on d 1 of blood collection. A positive relationship (r = 0.35; P = 0.03) was observed between the cows' rankings for each dose of GHRH; that is, high responders to the low dose were high responders to the high dose. Growth hormone response to the 4.5 microg/100 kg BW challenge dose of GHRH was positively related to sire milk EPD (R2 = 0.09; P = 0.03). Response of GH to the 1.5 microg GHRH/100 kg BW challenge dose also tended to be related (P = 0.08) to sire milk EPD of high milking cows. In addition, IGF-I concentrations of high milking cows were inversely related (R2 = 0.24; P = 0.04) to sire milk EPD. Growth hormone response to GHRH challenge may have potential as an additional tool in the evaluation of milk production in beef cattle.

Our objective was to compare the influence of dietary NaHCO3 and a multielement buffer on ruminal acid-base status and lactation performance of dairy cows. Five ruminally fistulated, primiparous and multiparous lactating Holstein cows averaging 123 +/- 21 d postpartum were assigned randomly to treatments in a 5 x 5 Latin square with 3-wk experimental periods. Treatments were a basal diet without supplemental buffers, with 1.5% NaHCO3 or 1.5% multielement buffer, or with NaHCO3 or multielement buffer solutions poured into the rumen via cannula at 2 h postfeeding. Addition of either buffer to the diet reduced ruminal fluid hydrogen ion concentration from 0 to 6 h postfeeding; only NaHCO3 reduced ruminal fluid acidity when dosed via the cannula. Addition of buffers via ruminal cannula appeared to retard the reduction in ruminal fluid acidity that normally occurs from 6 to 12 h postfeeding; this may have been related to a feedback mechanism inhibiting salivary buffer secretion. Buffering capacity of ruminal fluid tended to increase with buffer addition; the increase was greatest during infusion of NaHCO3. The ruminal fluid buffer value index increased by 4 units for control cows from early (0 to 6 h) to late (6 to 12) postfeeding; smaller increases were noted for addition of multielement buffer. This index was not different for NaHCO3 during these two intervals. Milk yield and DMI were not affected by buffer addition. Although milk fat content tended to be higher with the multielement buffer than with NaHCO3, it was not accompanied by the expected alterations in ruminal acid-base status. Therefore, this increase may be related to systemic effects of specific minerals in the multielement buffer rather than to a more stable ruminal environment. Based on the ruminal fluid buffer value index, NaHCO3 tended to maintain the most stable ruminal acid-base status.

Monthly estimates of 24-h milk yield were obtained on 160 spring-calving and 153 fall-calving crossbred cows containing various proportions (0, 1/4 or 1/2) of Brahman breeding, all bred to Limousin sires. Milk production was measured using weigh-suckle-weigh procedures. Interactions between crossbred group and season of calving were not significant. Across seasons, milk production rarely was affected by proportion of Brahman breeding; however, milk yield, averaged over six monthly measurements, was greater (P less than .10) for cows out of Hereford dams than for cows out of Angus dams. Averaged over six monthly measurements, estimated 24-h milk yield ranged from 5.3 kg for Hereford x Angus to 6.2 kg for Brahman x Hereford cows. Season of calving affected milk yield during the first and fourth measurement periods. Fall-calving cows produced more (P less than .01) milk during the first period whereas spring-calving cows produced more milk during the fourth period. Lactation patterns for the two seasons differed. Spring-calving cows had a more typical lactation curve, whereas the curve for fall-calving cows showed more variability in milk yield throughout lactation. Phenotypic correlations between monthly measurements of 24-h milk yield and calf performance tended to be moderate and positive within the spring group. Correlations for the fall group, although positive, tended to be weaker than those found in the spring group.

The article discusses a study to determine the effect of linseed meal (LSM) supplement in beef cows during late gestation and early lactation impacting offspring growth performance, steer carcass composition, and puberty attainment in heifer calves. It mentions that birth weight, and weaning weight of calves was not affected by LSM supplementation. The result of the study suggests that LSM supplement does not affect calf growth or onset of puberty in heifer calves.

The objectives were to study the effects of feeding rolled flaxseed (FLX) to early-lactation dairy cows on milk yield, milk components, and milk fatty acid profiles as well as on measures of cow reproduction. Lactating Holstein cows, on 3 commercial dairies, were fed either an early-lactation ration (CON) or a ration that was similar in protein, energy, and fat content but that included FLX (0.85 kg of DM/cow per day). Within each dairy, cows were allocated alternately to breeding pens upon leaving the fresh pen (approximately 10 ± 5 d postpartum). Pens (n = 4 to 5 pens/dairy) were randomized to treatment (n = 2 to 3 pens/treatment per dairy). Pen (CON, n = 6; FLX, n 7) was considered the experimental unit and data were analyzed as a split plot with pen as the whole-plot error term. Cows fed FLX had greater (P ≤ 0.06) proportions of cis-9, trans-11 C18:2, C18:3n-3, and C20:0 fatty acids in milk fat and a lesser (P = 0.03) proportion of C20:3n-6 fatty acid when compared with cows fed the CON diet. Treatment did not affect (P ≥ 0.24) milk yield, milk protein, protein yield, milk fat, or milk fat yield. No interactions (P ≥ 0.52) were found between treatment and season of the year or parity, or between treatment and days open, pregnancies per AT at first or second service, or pregnancy loss. In conclusion, feeding FLX at 0.85 kg/cow per day (DM basis) altered the fatty acid profile of milk, but milk yield, milk composition, and reproductive performance of dairy cows were not affected. [ABSTRACT FROM AUTHOR]

Data from 158 predominantly Angus fall-calving beef cows were used in 4 consecutive years to determine the effects of weaning date and cow age class on cow and calf performance. Treatments were arranged in a 2 × 2 factorial with 2 weaning dates and 2 age classes (young cows ⩽3 yr and mature cows ⩾4 yr). Weaning dates were 1) normal weaning in mid-April at 210 d of age (NW) and 2) late weaning in mid-July at 300 d of age (LW). Mature cows were heavier (P < 0.01) than young cows throughout the trial, although BCS was similar (P ⩾ 0.10) among cow age classes. Cow BW (P = 0.58) and BCS (P = 0.40) were similar among weaning treatments at NW; however, at the beginning of the calving season, NW cows were heavier (585 vs. 562 kg; P = 0.02) and had greater BCS (6.57 vs. 5.95; P < 0.0001) than LW cows. Postpartum BW and BCS losses were greater (P < 0.0001) for NW cows, resulting in similar BW (P = 0.56) and BCS (P = 0.07) at the beginning of the breeding season and until April. Progeny of NW cows, were 2.4 kg heavier (P < 0.01) at birth and grew faster before the April weaning date, resulting in increased BW (8 kg; P < 0.05) at the time of normal weaning. This increase in BW gain may be partially explained by the increased milk production of NW cows (0.59 kg/d as measured in February; P < 0.05). Although NW calves had increased BW in April, LW calves were heavier in July because of increased ADG during the weaning interval (1.13 vs. 0.8 kg; P < 0.0001). A cow age class x weaning date interaction (P = 0.007) was detected for pregnancy rate. Pregnancy rates were greater (P < 0.10) for LW-mature cows (96.7%) and NW-young cows (98.4%) than for LW-young cows (89.3%). However, pregnancy rate of NW-mature cows (90.2%) did not differ (P = 0.12) from that of LW-mature or LW-young cows, but was less than that of NW-young cows. These findings indicate that producers may benefit from matching weaning date to cow age class. It appears more advantageous to delay weaning of calves born to dams 4 yr or older while maintaining NW for dams 3 yr or younger at the time of calving. Late weaning had no detrimental effects on the performance of mature cows. [ABSTRACT FROM AUTHOR]

Spring calving Angus and Angus × Hereford multiparous cows were utilized to determine the effects of intramammary treatment with penicillin G procaine (200,000 IU) and novobiocin (400 mg) at the time of weaning on udder health and calf growth after the subsequent calving. Cows were stratified by age and breed and assigned randomly to receive intramammary treatment (n = 99) at weaning or as untreated controls (n = 97). Quarter milk samples were collected at weaning and at 8 to 14 d after calving. Milk samples were analyzed for somatic cell counts (SCC) and mastitis-causing bacteria. Dry cow treatment decreased (P = 0.005) the number of cows infected after calving. Treatment decreased (P = 0.04) the number of cows that developed new infections and reduced (P = 0.03) the number of quarters with mastitis-causing bacteria after calving that were infected at weaning. Somatic cell counts after calving were greatest (P = 0.008) for cows infected with Staphylococcus aureus. Treatment did not alter (P = 0.19) SCC of quarters after calving that were infected with S. aureus at weaning but reduced (P = 0.002) SCC after calving of quarters that were infected with coagulase-negative staphylococci at weaning. Body weight of calves during early lactation was increased (P = 0.006) if cows with intramammary infection were treated at weaning. Treatment of noninfected cows at weaning increased (P = 0.008) adjusted 205-d weaning weights of calves after the subsequent lactation when compared with untreated noninfected cows. We conclude that treatment of beef cows at weaning with intramammary antibiotics decreased intramammary infections after calving, improved udder health during the subsequent lactation, and increased BW gain of the calves. [ABSTRACT FROM AUTHOR]