No abstract

The objective of this study was to examine the effects of dietary starch source and content in the immediate postpartum period on plasma metabolites and hormones and ovarian follicular development. One of 3 diets was fed in a randomized block design to 40 cows from calving until 70 d in milk. The diets contained 45% alfalfa silage (AS), 45% barley silage (BS), or 41% barley silage and 4% supplemental starch (SS) on a dry matter basis. All diets contained 45% barley-based concentrate and 10% alfalfa hay. Resulting starch levels were 25.2, 23.3, and 26.7% for AS, BS, and SS, respectively. Body condition was scored every other week and dry matter intake and milk yield were recorded daily. Milk samples were obtained weekly and blood samples were taken at calving and then every other week to determine concentrations of glucose, insulin, insulin-like growth factor-1, β-hydroxybutyrate, and nonesterified fatty acids. Transrectal ultrasonography was performed twice per week from 7 d after calving until first ovulation or 62 d in milk in all cows. For a subset of 7 AS-, 8 BS-, and 9 SS-fed cows, a complete estrous cycle was monitored for ovarian dynamics, and blood samples were collected every second day for progesterone and estradiol. Luteinizing hormone pulsatility was also determined (5 cows/treatment) approximately 15 d postcalving. Treatment had no effect on body condition score, dry matter intake, blood metabolites, milk yield, or milk fat and protein contents, but BS-fed cows had significantly higher levels of milk urea nitrogen compared with SS cows. Cows fed SS (31 d) tended to have a shorter interval from calving to first ovulation than cows fed AS (43 d) or BS (38 d). The incidence of double first ovulations was higher in cows fed SS (46%) compared with those fed BS (0%). Treatment had no effect on LH pulse frequency or amplitude, ovarian dynamics, or progesterone and estradiol concentrations during the observed estrous cycle. Energy balance did not differ among cows fed the 3 diets. Overall, dietary starch source and concentration had little effect on productivity or metabolic status of postpartum cows.

Two studies were conducted to determine the effect of canola meal source on the standardized ileal digestible amino acids (AA) and nitrogen-corrected apparent metabolizable energy (AMEn) contents of canola meal (CM) from 6 processing plants in Canada. Two plants provided CM in both mash and pellet forms, while the other 4 provided CM in mash form only, giving a total of 8 samples. In the standardized ileal digestibility (SID) assay, 280 birds were housed 7 per cage and fed a commercial starter diet from 1 to 14 d of age followed by the test diets from 15 to 21 d. Diets were formulated to contain CM as the only source of protein. Chromic oxide was included in all diets as an indigestible marker. Diets were randomly assigned to 5 cages of 7 birds. On d 21, birds were euthanized by CO2 asphyxiation and digesta samples were collected from the terminal ileum for SID of AA. The SID values were calculated using ileal endogenous AA losses determination. In the AMEn assay, 330 birds were housed 6 per cage and fed a commercial starter diet from 1 to 14 d of age followed by the experimental diets from 15 to 19 d. The 8 experimental diets contained 30% of CM and 70% of a corn-soybean meal-based diet. There were differences (P < 0.05) among CM samples in the standardized ileal digestible content of all AA. Standardized ileal digestible contents of Arg, Lys, Met, and Thr averaged 2.17, 1.74, 0.53, and 1.03%, respectively. Pelleting reduced (P < 0.05) the standardized ileal digestible content of all AA in CM from one of the plants. There were differences (P<0.05) among CM samples in the AMEn contents with values ranging from 1,590 to 2,041 kcal/kg DM. In conclusion, there was effect of CM source on the standardized ileal digestible AA and AMEn contents. Regression equations for predicting standardized ileal digestible contents of selected AA from a simple measure of acid detergent fiber (ADF) were developed.

Associations of blood metabolites and production variables with ovarian function and parity, specifically, interval to first ovulation (IFO) and the incidence of ovarian cysts (OC) and multiple ovulation (MOV) at the first ovulation postpartum, were determined in lactating dairy cows. This retrospective study involved data on 169 Holstein cows from three studies on the same herd. Blood samples were taken weekly from week −1 to week 4, relative to calving, and transrectal ultrasonography was performed twice weekly from day 7 to day 60 postpartum. The overall IFO was 32.6 ± 1.9 d (mean ± SEM) and did not differ among lactations. Primiparous cows were at a greater risk of failing to ovulate before day 60 postpartum and cows in the third or greater lactation were at a higher risk for OC and MOV. Blood metabolites and production variables indicating a negative energy balance were associated with cows failing to ovulate before day 35 postpartum, but were not related with OC. Increased dry matter intake and milk yield, particularly in second lactation cows, were associated with a higher incidence of OC. While beta-hydroxybutyrate acid and insulin-like growth factor 1 were associated with MOV, the relationship was weak. Reducing negative energy balance is necessary to reduce IFO but may increase the incidence of MOV.

Studies have shown that there are variations in the chemical and nutritive composition of canola meal (CM) produced in Canada, some of which may result from differences among the canola seed crushing plants. Therefore, it is necessary to determine the variability in the nutritive value of CM as its end users desire increased meal consistency and more information on any potential variability in AA digestibility. Thus, 18 ileal cannulated barrows (average initial BW = 23.3 kg) were used to determine the apparent (AID) and standardized (SID) ileal digestibility of N and AA and standardized ileal digestible N and AA contents in CM from 6 processing plants in Canada. Two processing plants provided CM in both mash and pellet forms, whereas the other 4 provided it only in mash form, giving a total of 8 CM samples. The barrows were fed 9 cornstarch-based diets. The first 8 diets were formulated to contain the CM samples as the only source of AA. The ninth diet was a casein-cornstarch diet to determine ileal endogenous AA losses. All diets contained 0.3% titanium dioxide as an indigestible marker. Pigs were housed individually in pens and were fed the 9 diets in a completely randomized design for 3 periods to give 6 pigs per diet. Each experimental period lasted for 7 d, consisting of 5 d of adaptation and 2 d of ileal digesta collection at 2-h intervals from 0800 to 2000 h on d 6 and 7. There was an effect ( < 0.05) of CM source on 1) the AID of N, Met, Cys, Thr, Val, Gly, and Ser; 2) the SID of N, Met, and Cys; and 3) the standardized ileal digestible content of all AA. Pelleting reduced ( < 0.05) the standardized ileal digestible content of Arg, Ile, Glu, and Gly in 1 of the CM samples tested and of all AA except His in the other CM sample. The SID values for Arg, Lys, Met, and Thr averaged 87.2%, 78.2%, 84.5%, and 74.1%, respectively. The standardized ileal digestible contents of Arg, Lys, Met, and Thr averaged 2.10%, 1.71%, 0.50%, and 1.01%, respectively. In conclusion, there were variations in the AID, SID, and standardized ileal digestible AA contents of CM among crushing plants in Canada.