Effect of different diet supplements in the pre- and post-partum period on reproductive performance in the dairy cow

The study compared the impact of feeding different energy supplements (barley, molassed sugar beet and fat) prior to calving and the effects of feeding supplemental fat post-partum, on subsequent production and reproductive efficiency of dairy cows. Forty-eight multiparous Holstein-Friesian dairy cows were assigned to one of two groups, six weeks prior to expected calving date and fed a grass based total mixed ration according to ME requirements for late gestation. Group 1 was supplemented with barley (B) or molassed sugar beet feed (SB) prior to calving and was then given a high starch lactation ration. Group 2 was supplemented with either fat (F) or no supplement (C) pre partum, and was then given a similar lactation ration as Group 1 but supplemented with fat. Lactation rations were fed through to week-20 post partum and the cows were monitored during this period. Milk yield (P<0.002) and milkfat (P<0.02) production were higher and milk protein concentration (P<0.001) was lower in Group 2. The number of days to first rise in progesterone following parturition was greater (P<0.01) in Group 2. Due to the design of the study, effects of prepartum supplementation were only evaluated within each lactation ration group. Conception rate to first service was higher (P<0.001) for B than SB supplemented cows in Group 1 and higher (P<0.02) for F than C supplemented cows in Group 2. Services per conception were lower (P=0.06) for B than SB supplemented cows in Group 1 and lower (P<0.05) for F than C supplemented cows in Group 2. Overall pregnancy rates and days open were not significantly different between the groups. The data shows that pre-partum nutrition had an important role in determining subsequent fertility. Despite having negative effects early post partum, supplementing with fat did not affect overall reproductive performance but it did improve milk production.

Effects of ration on the maturation and fecundity in captive Atlantic herring (Clupea harengus)

We examined the effects of amount of food on vitellogenic oocyte size and number (fecundity) between two experimental groups of Atlantic herring (Clupea harengus) kept in separate but identical compartments of a large seawater tank. Growth and maturation were monitored for 1.5 years. Each group of 200 fish was fed exclusively on krill. At the end of the experiment, a high-ration group, fed 12 mg ·g fish-1 ·day-1, had similar weights-at-length as wild specimens of the same stock. A low-ration group fed about half the amount of the high-ration group had significantly lower weights-at-length. Ration had no effect on oocyte size and relative potential fecundity (oocytes per gram), but mean potential fecundity (oocytes per fish) of the low-ration fish was 26% lower than that of the high-ration fish. The relative intensity of early stages of atresia was quantified histologically. Atresia is a common phenomenon in Atlantic herring and increases markedly with suboptimal feeding. Mean relative atretic intensities were estimated at about 3 and 6% for the high- and low-ration groups, respectively, but with large intragroup variation. Modeled realized fecundity (spawned eggs per fish) indicated a 9 and 40% reduction compared with the measured potential fecundities, respectively.

Errata

In the February 1966 issue of this journal, two errors occurred in Joan C. Pitzner’s and Hughlett L. Morris’s article “Articulation Skills and Adequacy of Breath Pressure Ratios of Children with Cleft Palate.” On page 29, the heading “Reality” should be “Reliability,” and on page 30, the heading “Pressure-Ration Group One” should be “Pressure-Ratio Group One.”